WorldWideScience

Sample records for spectral domain optical

  1. INTRASURGICAL MICROSCOPE-INTEGRATED SPECTRAL DOMAIN OPTICAL COHERENCE TOMOGRAPHY-ASSISTED MEMBRANE PEELING.

    Science.gov (United States)

    Falkner-Radler, Christiane I; Glittenberg, Carl; Gabriel, Max; Binder, Susanne

    2015-10-01

    To evaluate microscope-integrated intrasurgical spectral domain optical coherence tomography during macular surgery in a prospective monocenter study. Before pars plana vitrectomy and before, during, and after membrane peeling, 512 × 128 macular cube scans were performed using a Carl Zeiss Meditec Cirrus high-definition OCT system adapted to the optical pathway of a Zeiss OPMI VISU 200 surgical microscope and compared with retinal staining. The study included 51 patients with epiretinal membranes, with 8 of those having additional lamellar macular holes, 11 patients with vitreomacular traction, and 8 patients with full-thickness macular holes. Intraoperative spectral domain optical coherence tomography allowed performing membrane peeling without using retinal dyes in 40% of cases (28 of 70 patients). No residual membranes were found in 94.3% of patients (66 of 70 patients) in intrasurgical spectral domain optical coherence tomography and subsequent (re)staining. In patients with vitreomacular traction, intrasurgical spectral domain optical coherence tomography scans facilitated decisions on the need for an intraocular tamponade after membrane peeling. Intraoperative spectral domain optical coherence tomography was comparable with retinal dyes in confirming success after membrane peeling. However, the visualization of flat membranes was better after staining.

  2. Spectral domain optical coherence tomography findings in tamoxifen retinopathy--a case report.

    Science.gov (United States)

    Nair, Sandhya Narayanan; Anantharaman, Giridhar; Gopalakrishnan, Mahesh; Vyas, Jyothiprakash

    2013-01-01

    To report spectral domain optical coherence tomography findings in a case of typical tamoxifen retinopathy. In this observational case report, a patient with tamoxifen retinopathy was imaged with spectral domain optical coherence tomography and fundus auto fluorescence. Spectral domain optical coherence tomography showed numerous hyperreflective spots within the retina, mainly in the inner retinal layers in both the eyes. The external limiting membrane, the Inner Segment-Outer Segment junction, and the photoreceptors were not discernable at the fovea in the right eye. In the left eye, there was foveal atrophy with total loss of photoreceptors. The autofluorescent images showed macular hypofluorescence with foveal hyperfluorescence. Spectral domain optical coherence tomography demonstrated abnormalities in the outer retinal layers in tamoxifen retinopathy. There were also characteristic alterations in the autofluorescence pattern at the macula in tamoxifen retinopathy.

  3. Submicron Resolution Spectral-Domain Optical Coherence Tomography

    KAUST Repository

    Alarousu, Erkki; Jabbour, Ghassan

    2013-01-01

    Apparatuses and systems for submicron resolution spectral-domain optical coherence tomography (OCT) are disclosed. The system may use white light sources having wavelengths within 400-1000 nanometers, and achieve resolution below 1 .mu

  4. Posterior lattice degeneration characterized by spectral domain optical coherence tomography.

    Science.gov (United States)

    Manjunath, Varsha; Taha, Mohammed; Fujimoto, James G; Duker, Jay S

    2011-03-01

    The purpose of this study was to use high-resolution spectral domain optical coherence tomography in the characterization of retinal and vitreal morphological changes overlying posterior lattice degeneration. A cross-sectional retrospective analysis was performed on 13 eyes of 13 nonconsecutive subjects with posterior lattice degeneration seen at the New England Eye Center, Tufts Medical Center between October 2009 and January 2010. Spectral domain optical coherence tomography images taken through the region of lattice degeneration were qualitatively analyzed. Four characteristic changes of the retina and vitreous were seen in the 13 eyes with lattice degeneration: 1) anterior/posterior U-shaped vitreous traction; 2) retinal breaks; 3) focal retinal thinning; and 4) vitreous membrane formation. The morphologic appearance of vitreous traction and retinal breaks were found to be consistent with previous histologic reports. It is possible to image posterior lattice degeneration in many eyes using spectral domain optical coherence tomography and to visualize the spectrum of retinal and vitreous changes throughout the area of lattice degeneration.

  5. Spectral-domain optical coherence tomography of roth spots.

    Science.gov (United States)

    Giovinazzo, Jerome; Mrejen, Sarah; Freund, K Bailey

    2013-01-01

    To describe the retinal findings of subacute bacterial endocarditis, their evolution after treatment, and analysis with spectral-domain optical coherence tomography. Retrospective chart review. A 21-year-old man presented with the sudden onset of a central scotoma in his left eye because of a sub-internal limiting membrane hemorrhage overlying the left fovea. When examined 2 weeks later, Roth spots were noted in his right eye. The patient was immediately referred to his internist and diagnosed with subacute bacterial endocarditis with cultures positive for Streptococcus viridans. He subsequently underwent aortic valve replacement surgery after 4 weeks of intravenous antibiotic therapy. When examined 4 weeks after valve replacement surgery, there was regression of the Roth spots. The present case demonstrates the importance of a funduscopic examination in the early diagnosis and management of subacute bacterial endocarditis. The analysis of Roth spots with spectral-domain optical coherence tomography suggested that they were septic emboli.

  6. Submicron Resolution Spectral-Domain Optical Coherence Tomography

    KAUST Repository

    Alarousu, Erkki

    2013-11-14

    Apparatuses and systems for submicron resolution spectral-domain optical coherence tomography (OCT) are disclosed. The system may use white light sources having wavelengths within 400-1000 nanometers, and achieve resolution below 1 .mu.m. The apparatus is aggregated into a unitary piece, and a user can connect the apparatus to a user provided controller and/or light source. The light source may be a supercontinuum source.

  7. Online monitoring of printed electronics by Spectral-Domain Optical Coherence Tomography

    KAUST Repository

    Alarousu, Erkki; Alsaggaf, Ahmed; Jabbour, Ghassan E.

    2013-01-01

    Spectral-Domain Optical Coherence Tomography (SD-OCT) is an optical method capable of 3D imaging of object's internal structure with micron-scale resolution. Modern SD-OCT tools offer the speed capable of online monitoring of printed devices

  8. Relationship Between Optic Nerve Appearance and Retinal Nerve Fiber Layer Thickness as Explored with Spectral Domain Optical Coherence Tomography

    Science.gov (United States)

    Aleman, Tomas S.; Huang, Jiayan; Garrity, Sean T.; Carter, Stuart B.; Aleman, Wendy D.; Ying, Gui-shuang; Tamhankar, Madhura A.

    2014-01-01

    Purpose To study the relationship between the appearance of the optic nerve and the retinal nerve fiber layer (RNFL) thickness determined by spectral domain optical coherence tomography (OCT). Methods Records from patients with spectral domain-OCT imaging in a neuro-ophthalmology practice were reviewed. Eyes with glaucoma/glaucoma suspicion, macular/optic nerve edema, pseudophakia, and with refractive errors > 6D were excluded. Optic nerve appearance by slit lamp biomicroscopy was related to the RNFL thickness by spectral domain-OCT and to visual field results. Results Ninety-one patients (176 eyes; mean age: 49 ± 15 years) were included. Eighty-three eyes (47%) showed optic nerve pallor; 89 eyes (50.6%) showed RNFL thinning (sectoral or average peripapillary). Average peripapillary RNFL thickness in eyes with pallor (mean ± SD = 76 ± 17 μm) was thinner compared to eyes without pallor (91 ± 14 μm, P < 0.001). Optic nerve pallor predicted RNFL thinning with a sensitivity of 69% and a specificity of 75%. Optic nerve appearance predicted RNFL thinning (with a sensitivity and specificity of 81%) when RNFL had thinned by ∼ 40%. Most patients with pallor had RNFL thinning with (66%) or without (25%) visual field loss; the remainder had normal RNFL and fields (5%) or with visual field abnormalities (4%). Conclusions Optic nerve pallor as a predictor of RNFL thinning showed fair sensitivity and specificity, although it is optimally sensitive/specific only when substantial RNFL loss has occurred. Translational Relevance Finding an acceptable relationship between the optic nerve appearance by ophthalmoscopy and spectral domain-OCT RNFL measures will help the clinician's interpretation of the information provided by this technology, which is gaining momentum in neuro-ophthalmic research. PMID:25374773

  9. Extended depth of focus adaptive optics spectral domain optical coherence tomography

    Science.gov (United States)

    Sasaki, Kazuhiro; Kurokawa, Kazuhiro; Makita, Shuichi; Yasuno, Yoshiaki

    2012-01-01

    We present an adaptive optics spectral domain optical coherence tomography (AO-SDOCT) with a long focal range by active phase modulation of the pupil. A long focal range is achieved by introducing AO-controlled third-order spherical aberration (SA). The property of SA and its effects on focal range are investigated in detail using the Huygens-Fresnel principle, beam profile measurement and OCT imaging of a phantom. The results indicate that the focal range is extended by applying SA, and the direction of extension can be controlled by the sign of applied SA. Finally, we demonstrated in vivo human retinal imaging by altering the applied SA. PMID:23082278

  10. Posterior Lattice Degeneration Characterized by Spectral Domain Optical Tomography

    OpenAIRE

    Manjunath, Varsha; Taha, Mohammed; Fujimoto, James G.; Duker, Jay S.

    2011-01-01

    PURPOSE: To utilize high-resolution spectral domain optical coherence tomography (SD-OCT) in the characterization of retinal and vitreal morphological changes overlying posterior lattice degeneration. METHODS: A cross-sectional, retrospective analysis was performed on 13 eyes of 13 nonconsecutive subjects with posterior lattice degeneration seen at the New England Eye Center, Tufts Medical Center between October 2009 and January 2010. SD-OCT images taken through the region of latti...

  11. Autofluorescence and spectral-domain optical coherence tomography of optic disk melanocytoma.

    Science.gov (United States)

    Guerra, Ricardo Luz Leitão; Marback, Eduardo Ferrari; Silva, Igor Sandes Pessoa da; Maia Junior, Otacílio de Oliveira; Marback, Roberto Lorens

    2014-01-01

    The authors report fundus autofluorescence (FAF) and spectral-domain optical coherence tomography (OCT) findings of two consecutive patients who presented with optic disk melanocytoma (ODM). A retrospective study was performed by reviewing medical records and ophthalmic imaging examinations. Optical coherence tomography findings were sloped and brightly reflective anterior tumor surface, adjacent retinal desorganization and abrupt posterior optical shadowing. Vitreous seeds were found in one patient. Fundus autofluorescence revealed outstanding hypoautofluorescence at the tumor area and isoautofluorescence at the remaining retina. Optical coherence tomography findings of the reported cases are consistent with those reported in the reviewed literature. Fundus autofluorescence has been used in the assessment of choroidal melanocytic tumors, but not yet in melanocytomas. We assume that this is the first report of these findings and believe that when its pattern has become clearly defined, fundus autofluorescence will be a useful tool to avoid misdiagnosis in suspicious cases and for follow-up.

  12. Autofluorescence and spectral-domain optical coherence tomography of optic disk melanocytoma

    Directory of Open Access Journals (Sweden)

    Ricardo Luz Leitão Guerra

    2014-12-01

    Full Text Available The authors report fundus autofluorescence (FAF and spectral-domain optical coherence tomography (OCT findings of two consecutive patients who presented with optic disk melanocytoma (ODM. A retrospective study was performed by reviewing medical records and ophthalmic imaging examinations. Optical coherence tomography findings were sloped and brightly reflective anterior tumor surface, adjacent retinal desorganization and abrupt posterior optical shadowing. Vitreous seeds were found in one patient. Fundus autofluorescence revealed outstanding hypoautofluorescence at the tumor area and isoautofluorescence at the remaining retina. Optical coherence tomography findings of the reported cases are consistent with those reported in the reviewed literature. Fundus autofluorescence has been used in the assessment of choroidal melanocytic tumors, but not yet in melanocytomas. We assume that this is the first report of these findings and believe that when its pattern has become clearly defined, fundus autofluorescence will be a useful tool to avoid misdiagnosis in suspicious cases and for follow-up.

  13. Spectral-domain optical coherence tomography staging and autofluorescence imaging in achromatopsia.

    Science.gov (United States)

    Greenberg, Jonathan P; Sherman, Jerome; Zweifel, Sandrine A; Chen, Royce W S; Duncker, Tobias; Kohl, Susanne; Baumann, Britta; Wissinger, Bernd; Yannuzzi, Lawrence A; Tsang, Stephen H

    2014-04-01

    IMPORTANCE Evidence is mounting that achromatopsia is a progressive retinal degeneration, and treatments for this condition are on the horizon. OBJECTIVES To categorize achromatopsia into clinically identifiable stages using spectral-domain optical coherence tomography and to describe fundus autofluorescence imaging in this condition. DESIGN, SETTING, AND PARTICIPANTS A prospective observational study was performed between 2010 and 2012 at the Edward S. Harkness Eye Institute, New York-Presbyterian Hospital. Participants included 17 patients (aged 10-62 years) with full-field electroretinography-confirmed achromatopsia. MAIN OUTCOMES AND MEASURES Spectral-domain optical coherence tomography features and staging system, fundus autofluorescence and near-infrared reflectance features and their correlation to optical coherence tomography, and genetic mutations served as the outcomes and measures. RESULTS Achromatopsia was categorized into 5 stages on spectral-domain optical coherence tomography: stage 1 (2 patients [12%]), intact outer retina; stage 2 (2 patients [12%]), inner segment ellipsoid line disruption; stage 3 (5 patients [29%]), presence of an optically empty space; stage 4 (5 patients [29%]), optically empty space with partial retinal pigment epithelium disruption; and stage 5 (3 patients [18%]), complete retinal pigment epithelium disruption and/or loss of the outer nuclear layer. Stage 1 patients showed isolated hyperreflectivity of the external limiting membrane in the fovea, and the external limiting membrane was hyperreflective above each optically empty space. On near infrared reflectance imaging, the fovea was normal, hyporeflective, or showed both hyporeflective and hyperreflective features. All patients demonstrated autofluorescence abnormalities in the fovea and/or parafovea: 9 participants (53%) had reduced or absent autofluorescence surrounded by increased autofluorescence, 4 individuals (24%) showed only reduced or absent autofluorescence, 3

  14. Thin film and multilayer optics for XUV spectral domain (1 nm to 60 nm)

    International Nuclear Information System (INIS)

    Delmotte, Franck

    2010-02-01

    The XUV spectral domain (1-60 nm wavelength range) has experienced rapid growth in recent years. On one side, the sources (synchrotron radiation, harmonic generation, x-ray laser, free-electron laser...) require ever more efficient optics, on the other hand, applications (diagnostics of hot plasma, solar physics, x-ray microscopy, EUV lithography, x-ray analysis...) provide new constraints on the design of multilayer stacks. The multilayer mirrors are the only way to achieve efficient optics operating at non-grazing incidence angles in this spectral range. Our work within the team XUV Optics at Laboratoire Charles Fabry de l'Institut d'Optique focuses on the study of materials in thin layers correlated to the study of optical properties of multilayers. The objective is to achieve new multilayer components previously unavailable in the XUV domain, through a better understanding of physical phenomena in these nano-layer stacks. We show through several examples of how we have managed both to improve the performance of multilayer mirrors in a broad spectral range, and secondly, to develop new optical functions: beam splitters, broadband mirrors, dual-band mirrors or phase compensation mirrors. (author)

  15. Transient spectral domain optical coherence tomography findings in classic MEWDS: a case report.

    Science.gov (United States)

    Lavigne, Luciana Castro; Isaac, David Leonardo Cruvinel; Duarte Júnior, José Osório; Avila, Marcos Pereira de

    2014-01-01

    The purpose of this study was to describe a patient with multiple evanescent white dot syndrome (MEWDS) who presented with classic retinal findings and transient changes in outer retinal anatomy. A 20-year-old man presented with mild blurred vision in the left eye, reporting flu-like symptoms 1 week before the visual symptoms started. Fundus examination of the left eye revealed foveal granularity and multiple scattered spots deep to the retina in the posterior pole. Fluorescein angiography and indocyanine green angiography showed typical MEWDS findings. Spectral Domain Optical Coherence Tomography has shown transient changes in outer retinal anatomy with disappearance of inner segment-outer segment junction and mild attenuation of external limiting membrane. Six months later, Spectral Domain Optical Coherence Tomography has shown complete resolution with recovery of normal outer retinal aspect.

  16. Spectral phase encoding of ultra-short optical pulse in time domain for OCDMA application.

    Science.gov (United States)

    Wang, Xu; Wada, Naoya

    2007-06-11

    We propose a novel reconfigurable time domain spectral phase encoding (SPE) scheme for coherent optical code-division-multiple-access application. In the proposed scheme, the ultra-short optical pulse is stretched by dispersive device and the SPE is done in time domain using high speed phase modulator. The time domain SPE scheme is robust to wavelength drift of the light source and is very flexible and compatible with the fiber optical system. Proof-of-principle experiments of encoding with 16-chip, 20 GHz/chip binary-phase-shift-keying codes and 1.25 Gbps data transmission have been successfully demonstrated together with an arrayed-wave-guide decoder.

  17. Infrared imaging and spectral-domain optical coherence tomography findings correlate with microperimetry in acute macular neuroretinopathy: a case report

    Directory of Open Access Journals (Sweden)

    Grover Sandeep

    2011-10-01

    Full Text Available Abstract Introduction Spectral-domain optical coherence tomography findings in a patient with acute macular neuroretinopathy, and correlation with functional defects on microperimetry, are presented. Case presentation A 25-year old Caucasian woman presented with bitemporal field defects following an upper respiratory tract infection. Her visual acuity was 20/20 in both eyes and a dilated fundus examination revealed bilateral hyperpigmentary changes in the papillomacular bundle. Our patient underwent further evaluation with spectral-domain optical coherence tomography, infrared and fundus autofluorescence imaging. Functional changes were assessed by microperimetry. Infrared imaging showed the classic wedge-shaped defects and spectral-domain optical coherence tomography exhibited changes at the inner segment-outer segment junction, with a thickened outer plexiform layer overlying these areas. Fluorescein and indocyanine green angiography did not demonstrate any perfusion defects or any other abnormality. Microperimetry demonstrated focal elevation in threshold correlating with the wedge-shaped defects in both eyes. Conclusion Spectral-domain optical coherence tomography findings provide new evidence of the involvement of the outer plexiform layer of the retina in acute macular neuroretinopathy.

  18. Technologies for Elastic Optical Networking Systems in Spatial, Temporal and Spectral Domains

    Science.gov (United States)

    Qin, Chuan

    wavelength to track the signal wavelength, thus providing a technique for authentically automatic wavelength tracking. I also explored different materials and crystal orientations to reduce the radio-frequency (RF) power consumption required to shift the wavelengths. Based on the elastic optical networking in the temporal, spectral and spatial domains, an additional degree of freedom has been investigated recently to increase the data capacity. The exploration to use the spatial domain to carry more data is termed as spatial division multiplexing (SDM). One such SDM method is orbital angular momentum(OAM), which is a group of orthogonal light beams carrying orbital angular momentum exhibiting an azimuthal phase variation. The utilization of OAM states has the potential to significantly increase the spectral efficiency and channel capacity. The thesis also includes the demonstration to establish a connection by exploiting the elasticity steering in spatial, temporal and spectral domains. Beam steering based on optical phased array (OPA) is also a potential candidate of SDM to carry information when a different linear phase will distribute light to different spatial locations. The states are intrinsically orthogonal to one another. Using 4x4 3-D waveguides written by ultrafast laser inscription (ULI), we demonstrated 2-D optical phased array (OPA) beam steering that shows steering in both vertical and horizontal directions. Enabling technologies provide future pathways for elastic optical networking and will fundamentally impact optical communication systems in many ways.

  19. Spectral domain optical coherence tomography characteristics in diabetic retinopathy

    Directory of Open Access Journals (Sweden)

    Laxmi Gella

    2014-01-01

    Full Text Available Purpose: To report the appearance of diabetic retinopathy lesions using spectral domain optical coherence tomography (SD-OCT. Materials and Methods: A total of 287 eyes of 199 subjects were included. All the subjects underwent complete ophthalmic examination including SD-OCT. Results: The appearance of various lesions of diabetic retinopathy and the retinal layers involved were reported. In subjects with macular edema the prevalence of incomplete PVD was 55.6%. Conclusion: SD-OCT brings new insights into the morphological changes of the retina in diabetic retinopathy.

  20. Clinical manifestations of optic pit maculopathy as demonstrated by spectral domain optical coherence tomography

    Directory of Open Access Journals (Sweden)

    Tzu JH

    2013-01-01

    Full Text Available Jonathan H Tzu, Harry W Flynn Jr, Audina M Berrocal, William E Smiddy, Timothy G Murray, Yale L FisherDepartment of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USAPurpose: The purpose of this retrospective study was to evaluate the characteristic features, including spectral-domain optical coherence tomography (SD-OCT, clinical course, and outcome of treatment if given for patients with optic disc pit maculopathy.Methods: We investigated a consecutive series of patients with a diagnosis of optic pit maculopathy treated between 2001 and 2012 at the Bascom Palmer Eye Institute. Patients were divided into two main groups, ie, patients who were observed without surgery and patients who received surgical intervention. The main outcome measures were presenting and final visual acuity, and changes in SD-OCT imaging were recorded. Other data including age, gender, eye, age of onset, length of follow-up, location of optic pit, and location of fluid by OCT were also recorded.Results: On OCT, 67% (12/18 of the eyes showed schisis-like cavities, 22% (4/18 had only subretinal fluid, and 17% (3/18 had only a schisis-like cavity without subretinal fluid. In the patients managed by observation, visual acuity was ≥20/200 in 6/8 eyes initially and 6/8 eyes at last follow-up. Ten of 18 patients received either focal laser, surgery or both. Six of 10 eyes undergoing surgery had initial visual acuity ≥ 20/200, and 8 of 10 eyes undergoing surgery had a visual acuity of ≥20/200 at last follow-up.Conclusion: In this study, many eyes were observed and remained stable during follow-up. In eyes with reduced vision, surgical intervention produced variable outcomes, and persistent intraretinal/subretinal fluid was a common occurrence.Keywords: optic pit maculopathy, spectral-domain optical coherence tomography

  1. Spectral domain optical coherence tomography morphology in optic disc pit associated maculopathy

    Directory of Open Access Journals (Sweden)

    Janusz Michalewski

    2014-01-01

    Full Text Available Purpose: Our purpose was to study the clinical manifestation and course of optic pit maculopathy using Spectral Domain Optical Coherence Tomography (SD- OCT images. Materials and Methods: We used SD-OCT to examine 20 eyes of 19 patients with a macular detachment in combination with an optic. Results: We observed five different fovea appearances in regard to fluid localization. In five eyes, we recorded changes in the fluid distribution with SD-OCT. In 17/20 eyes, we noted a communication between the perineural and subretinal and/or intraretinal space at the margin of the optic disc. Conclusion: 3-dimensional SD-OCT (3D-SDOCT scans revealed a three-fold connection, between subretinal and intraretinal space, perineural space, and the vitreous cavity. Therefore, we suppose that intraretinal or subretinal fluid in optic pit maculopathy may have both a vitreous and cerebrospinal origin. A membrane, covering the optic nerve was noted in 14 cases. Even if it seems intact in some B-scans, it is not complete in others several micrometers apart. Additionally, we observed fluid accumulation below the margin of the optic disc and hyperreflective porous tissue in the optic disc excavation. Those findings do not influence the course of maculopathy.

  2. Quantifying Optical Microangiography Images Obtained from a Spectral Domain Optical Coherence Tomography System

    Directory of Open Access Journals (Sweden)

    Roberto Reif

    2012-01-01

    Full Text Available The blood vessel morphology is known to correlate with several diseases, such as cancer, and is important for describing several tissue physiological processes, like angiogenesis. Therefore, a quantitative method for characterizing the angiography obtained from medical images would have several clinical applications. Optical microangiography (OMAG is a method for obtaining three-dimensional images of blood vessels within a volume of tissue. In this study we propose to quantify OMAG images obtained with a spectral domain optical coherence tomography system. A technique for determining three measureable parameters (the fractal dimension, the vessel length fraction, and the vessel area density is proposed and validated. Finally, the repeatability for acquiring OMAG images is determined, and a new method for analyzing small areas from these images is proposed.

  3. Online monitoring of printed electronics by Spectral-Domain Optical Coherence Tomography

    KAUST Repository

    Alarousu, Erkki

    2013-03-28

    Spectral-Domain Optical Coherence Tomography (SD-OCT) is an optical method capable of 3D imaging of object\\'s internal structure with micron-scale resolution. Modern SD-OCT tools offer the speed capable of online monitoring of printed devices. This paper demonstrates the use of SD-OCT in a simulated roll-to-roll (R2R) process through monitoring some structural properties of moving screen printed interdigitated electrodes. It is shown that structural properties can be resolved for speeds up to ca. 1m/min, which is the first step towards application of this method in real manufacturing processes, including roll-to-roll (R2R) printing.

  4. Extending the Effective Ranging Depth of Spectral Domain Optical Coherence Tomography by Spatial Frequency Domain Multiplexing

    Directory of Open Access Journals (Sweden)

    Tong Wu

    2016-11-01

    Full Text Available We present a spatial frequency domain multiplexing method for extending the imaging depth range of a spectral domain optical coherence tomography (SDOCT system without any expensive device. This method uses two galvo scanners with different pivot-offset distances in two independent reference arms for spatial frequency modulation and multiplexing. The spatial frequency contents corresponding to different depth regions of the sample can be shifted to different frequency bands. The spatial frequency domain multiplexing SDOCT system provides an approximately 1.9-fold increase in the effective ranging depth compared with that of a conventional full-range SDOCT system. The reconstructed images of phantom and biological tissue demonstrate the expected increase in ranging depth. The parameters choice criterion for this method is discussed.

  5. Full-range k-domain linearization in spectral-domain optical coherence tomography.

    Science.gov (United States)

    Jeon, Mansik; Kim, Jeehyun; Jung, Unsang; Lee, Changho; Jung, Woonggyu; Boppart, Stephen A

    2011-03-10

    A full-bandwidth k-domain linearization method for spectral-domain optical coherence tomography (SD-OCT) is demonstrated. The method uses information of the wavenumber-pixel-position provided by a translating-slit-based wavelength filter. For calibration purposes, the filter is placed either after a broadband source or at the end of the sample path, and the filtered spectrum with a narrowed line width (∼0.5 nm) is incident on a line-scan camera in the detection path. The wavelength-swept spectra are co-registered with the pixel positions according to their central wavelengths, which can be automatically measured with an optical spectrum analyzer. For imaging, the method does not require a filter or a software recalibration algorithm; it simply resamples the OCT signal from the detector array without employing rescaling or interpolation methods. The accuracy of k-linearization is maximized by increasing the k-linearization order, which is known to be a crucial parameter for maintaining a narrow point-spread function (PSF) width at increasing depths. The broadening effect is studied by changing the k-linearization order by undersampling to search for the optimal value. The system provides more position information, surpassing the optimum without compromising the imaging speed. The proposed full-range k-domain linearization method can be applied to SD-OCT systems to simplify their hardware/software, increase their speed, and improve the axial image resolution. The experimentally measured width of PSF in air has an FWHM of 8 μm at the edge of the axial measurement range. At an imaging depth of 2.5 mm, the sensitivity of the full-range calibration case drops less than 10 dB compared with the uncompensated case.

  6. Extracting structural features of rat sciatic nerve using polarization-sensitive spectral domain optical coherence tomography

    NARCIS (Netherlands)

    Islam, M.S.; Oliveira, M.C.; Wang, Y.; Henry, F.P.; Randolph, M.A.; Park, B. H.; de Boer, J.F.

    2012-01-01

    We present spectral domain polarization-sensitive optical coherence tomography (SD PS-OCT) imaging of peripheral nerves. Structural and polarization-sensitive OCT imaging of uninjured rat sciatic nerves was evaluated both qualitatively and quantitatively. OCT and its functional extension, PS-OCT,

  7. Photoreceptor inner segment ellipsoid band integrity on spectral domain optical coherence tomography

    Directory of Open Access Journals (Sweden)

    Saxena S

    2014-12-01

    Full Text Available Sandeep Saxena,1 Khushboo Srivastav,1 Chui M Cheung,2 Joanne YW Ng,3 Timothy YY Lai3 1Retina Service, Department of Ophthalmology, King George’s Medical University Lucknow, India; 2Singapore National Eye Centre, Singapore; 3Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Kowloon, Hong Kong Abstract: Spectral domain optical coherence tomography cross-sectional imaging of the macula has conventionally been resolved into four bands. However, some doubts were raised regarding authentication of the existence of these bands. Recently, a number of studies have suggested that the second band appeared to originate from the inner segment ellipsoids of the foveal cone photoreceptors, and therefore the previously called inner segment-outer segment junction is now referred to as inner segment ellipsoidband. Photoreceptor dysfunction may be a significant predictor of visual acuity in a spectrum of surgical and medical retinal diseases. This review aims to provide an overview and summarizes the role of the photoreceptor inner segment ellipsoid band in the management and prognostication of various vitreoretinal diseases. Keywords: spectral domain optical coherence tomography, inner segment-outer segment junction, external limiting membrane, macular hole, diabetic macular edema, age relate macular degeneration

  8. Flow patterns on spectral-domain optical coherence tomography reveal flow directions at retinal vessel bifurcations

    DEFF Research Database (Denmark)

    Willerslev, Anne; Li, Xiao Q; Munch, Inger C

    2014-01-01

    PURPOSE: To study intravascular characteristics of flowing blood in retinal vessels using spectral-domain optical coherence tomography (SD-OCT). METHODS: Examination of selected arterial bifurcations and venous sites of confluence in 25 healthy 11-year-old children recruited as an ad hoc subsample...

  9. Spectral domain optical coherence tomography imaging of spectacular ecdysis in the royal python (Python regius).

    Science.gov (United States)

    Tusler, Charlotte A; Maggs, David J; Kass, Philip H; Paul-Murphy, Joanne R; Schwab, Ivan R; Murphy, Christopher J

    2015-01-01

    To describe using spectral domain optical coherence tomography (SD-OCT), digital slit-lamp biomicroscopy, and external photography, changes in the ophidian cuticle, spectacle, and cornea during ecdysis. Four normal royal pythons (Python regius). Snakes were assessed once daily throughout a complete shed cycle using nasal, axial, and temporal SD-OCT images, digital slit-lamp biomicroscopy, and external photography. Spectral domain optical coherence tomography (SD-OCT) images reliably showed the spectacular cuticle and stroma, subcuticular space (SCS), cornea, anterior chamber, iris, and Schlemm's canal. When visible, the subspectacular space (SSS) was more distended peripherally than axially. Ocular surface changes throughout ecdysis were relatively conserved among snakes at all three regions imaged. From baseline (7 days following completion of a full cycle), the spectacle gradually thickened before separating into superficial cuticular and deep, hyper-reflective stromal components, thereby creating the SCS. During spectacular separation, the stroma regained original reflectivity, and multiple hyper-reflective foci (likely fragments from the cuticular-stromal interface) were noted within the SCS. The cornea was relatively unchanged in character or thickness throughout all stages of ecdysis. Slit-lamp images did not permit observation of these changes. Spectral domain optical coherence tomography (SD-OCT) provided excellent high-resolution images of the snake anterior segment, and especially the cuticle, spectacle, and cornea of manually restrained normal snakes at all stages of ecdysis and warrants investigation in snakes with anterior segment disease. The peripheral spectacle may be the preferred entry point for diagnostic or therapeutic injections into the SSS and for initiating spectacular surgery. © 2014 American College of Veterinary Ophthalmologists.

  10. A joint estimation detection of Glaucoma progression in 3D spectral domain optical coherence tomography optic nerve head images

    Science.gov (United States)

    Belghith, Akram; Bowd, Christopher; Weinreb, Robert N.; Zangwill, Linda M.

    2014-03-01

    Glaucoma is an ocular disease characterized by distinctive changes in the optic nerve head (ONH) and visual field. Glaucoma can strike without symptoms and causes blindness if it remains without treatment. Therefore, early disease detection is important so that treatment can be initiated and blindness prevented. In this context, important advances in technology for non-invasive imaging of the eye have been made providing quantitative tools to measure structural changes in ONH topography, an essential element for glaucoma detection and monitoring. 3D spectral domain optical coherence tomography (SD-OCT), an optical imaging technique, has been commonly used to discriminate glaucomatous from healthy subjects. In this paper, we present a new framework for detection of glaucoma progression using 3D SD-OCT images. In contrast to previous works that the retinal nerve fiber layer (RNFL) thickness measurement provided by commercially available spectral-domain optical coherence tomograph, we consider the whole 3D volume for change detection. To integrate a priori knowledge and in particular the spatial voxel dependency in the change detection map, we propose the use of the Markov Random Field to handle a such dependency. To accommodate the presence of false positive detection, the estimated change detection map is then used to classify a 3D SDOCT image into the "non-progressing" and "progressing" glaucoma classes, based on a fuzzy logic classifier. We compared the diagnostic performance of the proposed framework to existing methods of progression detection.

  11. Spectral domain optical coherence tomography imaging of subretinal bands associated with chronic retinal detachments

    OpenAIRE

    Kothari, Nikisha; Kuriyan, Ajay E; Flynn, Harry W

    2016-01-01

    Nikisha Kothari, Ajay E Kuriyan, Harry W Flynn JrDepartment of Ophthalmology, Bascom Palmer Eye Institute, Miller School of Medicine, University of Miami, Miami, FL, USAAbstract: We report three patients with subretinal bands associated with retinal detachment in chronic retinal detachments who underwent successful retinal reattachment. Subretinal bands before and after surgery can be identified on clinical examination and spectral domain optical coherence tomography. Removal of subr...

  12. Photoreceptor layer map using spectral-domain optical coherence tomography.

    Science.gov (United States)

    Lee, Ji Eun; Lim, Dae Won; Bae, Han Yong; Park, Hyun Jin

    2009-12-01

    To develop a novel method for analysis of the photoreceptor layer map (PLM) generated using spectral-domain optical coherence tomography (OCT). OCT scans were obtained from 20 eyes, 10 with macular holes (MH) and 10 with central serous chorioretinopathy (CSC) using the Macular Cube (512 x 128) protocol of the Cirrus HD-OCT (Carl Zeiss). The scanned data were processed using embedded tools of the advanced visualization. A partial thickness OCT fundus image of the photoreceptor layer was generated by setting the region of interest to a 50-microm thick layer that was parallel and adjacent to the retinal pigment epithelium. The resulting image depicted the photoreceptor layer as a map of the reflectivity in OCT. The PLM was compared with fundus photography, auto-fluorescence, tomography, and retinal thickness map. The signal from the photoreceptor layer of every OCT scan in each case was demonstrated as a single image of PLM in a fundus photograph fashion. In PLM images, detachment of the sensory retina is depicted as a hypo-reflective area, which represents the base of MH and serous detachment in CSC. Relative hypo-reflectivity, which was also noted at closed MH and at recently reattached retina in CSC, was associated with reduced signal from the junction between the inner and outer segments of photoreceptors in OCT images. Using PLM, changes in the area of detachment and reflectivity of the photoreceptor layer could be efficiently monitored. The photoreceptor layer can be analyzed as a map using spectral-domain OCT. In the treatment of both MH and CSC, PLM may provide new pathological information about the photoreceptor layer to expand our understanding of these diseases.

  13. Three-dimensional, time-resolved profiling of ferroelectric domain wall dynamics by spectral-domain optical coherence tomography

    International Nuclear Information System (INIS)

    Haussmann, Alexander; Schmidt, Sebastian; Wehmeier, Lukas; Eng, Lukas M.; Kirsten, Lars; Cimalla, Peter; Koch, Edmund

    2017-01-01

    We apply here spectral-domain optical coherence tomography (SD-OCT) for the precise detection and temporal tracking of ferroelectric domain walls (DWs) in magnesium-doped periodically poled lithium niobate (Mg:PPLN). We reproducibly map static DWs at an axial (depth) resolution down to ∝ 0.6 μm, being located up to 0.5 mm well inside the single crystalline Mg:PPLN sample. We show that a full 3-dimensional (3D) reconstruction of the DW geometry is possible from the collected data, when applying a special algorithm that accounts for the nonlinear optical dispersion of the material. Our OCT investigation provides valuable reference information on the DWs' polarization charge distribution, which is known to be the key to the electrical conductivity of ferroelectric DWs in such systems. Hence, we carefully analyze the SD-OCT signal dependence both when varying the direction of incident polarization, and when applying electrical fields along the polar axis. Surprisingly, the large backreflection intensities recorded under extraordinary polarization are not affected by any electrical field, at least for field strengths below the switching threshold, while no significant signals above noise floor are detected under ordinary polarization. Finally, we employed the high-speed SD-OCT setup for the real-time DW tracking upon ferroelectric domain switching under high external fields. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. Three-dimensional, time-resolved profiling of ferroelectric domain wall dynamics by spectral-domain optical coherence tomography

    Energy Technology Data Exchange (ETDEWEB)

    Haussmann, Alexander; Schmidt, Sebastian; Wehmeier, Lukas; Eng, Lukas M. [Technische Universitaet Dresden, Institute of Applied Physics and Center for Advancing Electronics Dresden (cfaed), Dresden (Germany); Kirsten, Lars; Cimalla, Peter; Koch, Edmund [Technische Universitaet Dresden, Faculty of Medicine Carl Gustav Carus, Anesthesiology and Intensive Care Medicine, Clinical Sensoring and Monitoring, Dresden (Germany)

    2017-08-15

    We apply here spectral-domain optical coherence tomography (SD-OCT) for the precise detection and temporal tracking of ferroelectric domain walls (DWs) in magnesium-doped periodically poled lithium niobate (Mg:PPLN). We reproducibly map static DWs at an axial (depth) resolution down to ∝ 0.6 μm, being located up to 0.5 mm well inside the single crystalline Mg:PPLN sample. We show that a full 3-dimensional (3D) reconstruction of the DW geometry is possible from the collected data, when applying a special algorithm that accounts for the nonlinear optical dispersion of the material. Our OCT investigation provides valuable reference information on the DWs' polarization charge distribution, which is known to be the key to the electrical conductivity of ferroelectric DWs in such systems. Hence, we carefully analyze the SD-OCT signal dependence both when varying the direction of incident polarization, and when applying electrical fields along the polar axis. Surprisingly, the large backreflection intensities recorded under extraordinary polarization are not affected by any electrical field, at least for field strengths below the switching threshold, while no significant signals above noise floor are detected under ordinary polarization. Finally, we employed the high-speed SD-OCT setup for the real-time DW tracking upon ferroelectric domain switching under high external fields. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. Agreement of angle closure assessments between gonioscopy, anterior segment optical coherence tomography and spectral domain optical coherence tomography

    OpenAIRE

    Tay, Elton Lik Tong; Yong, Vernon Khet Yau; Lim, Boon Ang; Sia, Stelson; Wong, Elizabeth Poh Ying; Yip, Leonard Wei Leon

    2015-01-01

    AIM: To determine angle closure agreements between gonioscopy and anterior segment optical coherence tomography (AS-OCT), as well as gonioscopy and spectral domain OCT (SD-OCT). A secondary objective was to quantify inter-observer agreements of AS-OCT and SD-OCT assessments. METHODS: Seventeen consecutive subjects (33 eyes) were recruited from the study hospital’s Glaucoma clinic. Gonioscopy was performed by a glaucomatologist masked to OCT results. OCT images were read independently by 2 ...

  16. Time domain optical spectrometry with fiber optic waveguides

    International Nuclear Information System (INIS)

    Whitten, W.B.

    1983-01-01

    Spectrometers which use optical fibers to obtain time domain spectral dispersion are reviewed. Pulse transmission through fiber optic waveguides is discussed and the basic requirements for sources and detectors are given. Multiplex spectrometry and time-of-flight spectrometry are then discussed. Resolution, fiber requirements, instrumentation and specific spectrometers are presented

  17. Using spectral-domain optical coherence tomography to detect optic neuropathy in patients with craniosynostosis.

    Science.gov (United States)

    Dagi, Linda R; Tiedemann, Laura M; Heidary, Gena; Robson, Caroline D; Hall, Amber M; Zurakowski, David

    2014-12-01

    Detecting and monitoring optic neuropathy in patients with craniosynostosis is a clinical challenge due to limited cooperation, and subjective measures of visual function. The purpose of this study was to appraise the correlation of peripapillary retinal nerve fiber layer (RNFL) thickness measured by spectral-domain ocular coherence tomography (SD-OCT) with indication of optic neuropathy based on fundus examination. The medical records of all patients with craniosynostosis presenting for ophthalmic evaluation during 2013 were retrospectively reviewed. The following data were abstracted from the record: diagnosis, historical evidence of elevated intracranial pressure, current ophthalmic evaluation and visual field results, and current peripapillary RNFL thickness. A total of 54 patients were included (mean age, 10.6 years [range, 2.4-33.8 years]). Thirteen (24%) had evidence of optic neuropathy based on current fundus examination. Of these, 10 (77%) demonstrated either peripapillary RNFL elevation and papilledema or depression with optic atrophy. Sensitivity for detecting optic atrophy was 88%; for papilledema, 60%; and for either form of optic neuropathy, 77%. Specificity was 94%, 90%, and 83%, respectively. Kappa agreement was substantial for optic atrophy (κ = 0.73) and moderate for papilledema (κ = 0.39) and for either form of optic neuropathy (κ = 0.54). Logistic regression indicated that peripapillary RNFL thickness was predictive of optic neuropathy (P optic neuropathy than visual field testing (likelihood ratio = 10.02; P = 0.002). Sensitivity and specificity of logMAR visual acuity in detecting optic neuropathy were 15% and 95%, respectively. Peripapillary RNFL thickness measured by SD-OCT provides adjunctive evidence for identifying optic neuropathy in patients with craniosynostosis and appears more sensitive at detecting optic atrophy than papilledema. Copyright © 2014 American Association for Pediatric Ophthalmology and Strabismus. Published by

  18. Automated 3-D method for the correction of axial artifacts in spectral-domain optical coherence tomography images

    NARCIS (Netherlands)

    B. Antony (Bhavna); M.D. Abràmoff (Michael); L. Tang (Li); W.D. Ramdas (Wishal); J.R. Vingerling (Hans); N.M. Jansonius (Nomdo); K. Lee (Kyungmoo); Y.H. Kwon (Young); M. Sonka (Milan); M.K. Garvin (Mona)

    2011-01-01

    textabstractThe 3-D spectral-domain optical coherence tomography (SD-OCT) images of the retina often do not reflect the true shape of the retina and are distorted differently along the x and y axes. In this paper, we propose a novel technique that uses thin-plate splines in two stages to estimate

  19. Automated 3-D method for the correction of axial artifacts in spectral-domain optical coherence tomography images

    NARCIS (Netherlands)

    Antony, Bhavna; Abramoff, Michael D.; Tang, Li; Ramdas, Wishal D.; Vingerling, Johannes R.; Jansonius, Nomdo M.; Lee, Kyungmoo; Kwon, Young H.; Sonka, Milan; Garvin, Mona K.

    2011-01-01

    The 3-D spectral-domain optical coherence tomography (SD-OCT) images of the retina often do not reflect the true shape of the retina and are distorted differently along the x and y axes. In this paper, we propose a novel technique that uses thin-plate splines in two stages to estimate and correct

  20. Two-harmonic complex spectral-domain optical coherence tomography using achromatic sinusoidal phase modulation

    Science.gov (United States)

    Lu, Sheng-Hua; Huang, Siang-Ru; Chou, Che-Chung

    2018-03-01

    We resolve the complex conjugate ambiguity in spectral-domain optical coherence tomography (SD-OCT) by using achromatic two-harmonic method. Unlike previous researches, the optical phase of the fiber interferometer is modulated by an achromatic phase shifter based on an optical delay line. The achromatic phase modulation leads to a wavelength-independent scaling coefficient for the two harmonics. Dividing the mean absolute value of the first harmonic by that of the second harmonic in a B-scan interferogram directly gives the scaling coefficient. It greatly simplifies the determination of the magnitude ratio between the two harmonics without the need of third harmonic and cumbersome iterative calculations. The inverse fast Fourier transform of the complex-valued interferogram constructed with the scaling coefficient, first and second harmonics yields a full-range OCT image. Experimental results confirm the effectiveness of the proposed achromatic two-harmonic technique for suppressing the mirror artifacts in SD-OCT images.

  1. Spectral Domain Optical Coherence Tomography Findings in Posterior Microphthalmia

    Directory of Open Access Journals (Sweden)

    Emine Tınkır Kayıtmazbatır

    2014-05-01

    Full Text Available The retinal spectral domain optical coherence tomography (SD-OCT findings of two posterior microphthalmia cases are presented in this case report. For this purpose, the findings of two siblings aged five and seven years who presented to our clinic with the complain of far-sightedness and high hypermetropia were evaluated. Both cases diagnosed to have posterior microphthalmia demonstrated normal biomicroscopic anterior segment examination and gonioscopy findings and the axial lengths were measured to be shorter than 17mm. The SD-OCT analysis of papillomacular folds detected in fundus examination revealed contribution of only neurosensorial retina. Beneath the retinal fold, we observed bilateral cysts in the intraretinal area in one of the cases and a triangle-shaped hyporeflective space with an apex corresponding to that of the retinal fold in the subretinal area in both cases. SD-OCT is an adjunctive imaging tool for diagnosis and follow-up of degenerative changes in posterior microphthalmia. These changes may be also important for visual prognosis. (Turk J Ophthalmol 2014; 44: 240-2

  2. Investigation of retinal morphology alterations using spectral domain optical coherence tomography in a mouse model of retinal branch and central retinal vein occlusion.

    Directory of Open Access Journals (Sweden)

    Andreas Ebneter

    Full Text Available Retinal vein occlusion is a leading cause of visual impairment. Experimental models of this condition based on laser photocoagulation of retinal veins have been described and extensively exploited in mammals and larger rodents such as the rat. However, few reports exist on the use of this paradigm in the mouse. The objective of this study was to investigate a model of branch and central retinal vein occlusion in the mouse and characterize in vivo longitudinal retinal morphology alterations using spectral domain optical coherence tomography. Retinal veins were experimentally occluded using laser photocoagulation after intravenous application of Rose Bengal, a photo-activator dye enhancing thrombus formation. Depending on the number of veins occluded, variable amounts of capillary dropout were seen on fluorescein angiography. Vascular endothelial growth factor levels were markedly elevated early and peaked at day one. Retinal thickness measurements with spectral domain optical coherence tomography showed significant swelling (p<0.001 compared to baseline, followed by gradual thinning plateauing two weeks after the experimental intervention (p<0.001. Histological findings at day seven correlated with spectral domain optical coherence tomography imaging. The inner layers were predominantly affected by degeneration with the outer nuclear layer and the photoreceptor outer segments largely preserved. The application of this retinal vein occlusion model in the mouse carries several advantages over its use in other larger species, such as access to a vast range of genetically modified animals. Retinal changes after experimental retinal vein occlusion in this mouse model can be non-invasively quantified by spectral domain optical coherence tomography, and may be used to monitor effects of potential therapeutic interventions.

  3. Three dimensional tracking for volumetric spectral-domain optical coherence tomography.

    Science.gov (United States)

    Maguluri, Gopi; Mujat, Mircea; Park, B H; Kim, K H; Sun, Wei; Iftimia, N V; Ferguson, R D; Hammer, Daniel X; Chen, Teresa C; de Boer, Johannes F

    2007-12-10

    We present a three-dimensional (3D) tracker for a clinical ophthalmic spectral domain optical coherence tomography (SD-OCT) system that combines depth-tracking with lateral tracking, providing a stabilized reference frame for 3D data recording and post acquisition analysis. The depth-tracking system is implemented through a real-time dynamic feedback mechanism to compensate for motion artifact in the axial direction. Active monitoring of the retina and adapting the reference arm of the interferometer allowed the whole thickness of the retina to be stabilized to within +/-100 mum. We achieve a relatively constant SNR from image to image by stabilizing the image of the retina with respect to the depth dependent sensitivity of SD-OCT. The depth tracking range of our system is 5.2 mm in air and the depth is adjusted every frame.nhancement in the stability of the images with the depth-tracking algorithm is demonstrated on a healthy volunteer.

  4. Infrared autofluorescence, short-wave autofluorescence and spectral-domain optical coherence tomography of optic disk melanocytomas

    Directory of Open Access Journals (Sweden)

    Peng Zhang

    2016-05-01

    Full Text Available AIM: To investigate the findings of infrared fundus autofluorescence (IR-AF and spectral-domain optical coherence tomography (SD-OCT in eyes with optic disc melanocytoma (ODM. METHODS: IR-AF findings and those of other ophthalmologic imaging examinations, including short-wave autofluorescence (SW-AF, fluorescein angiography (FA, fundus color photography, and SD-OCT of 8 eyes of 8 consecutive cases with ODM were assessed. RESULTS: The ODMs in all cases (100% presented similar IR-AF, SW-AF, and FA findings. On IR-AF images, ODMs showed outstanding hyper-AF with well-defined outline. On SW-AF images, the area of ODMs presented as hypo-AF. FA images revealed the leaking retinal telangiectasia on the surface of the ODMs. On SD-OCT images in 8 cases (100%, the ODMs were sloped with highly reflective surface, which were disorganized retina and optic nerve layers. In 7 cases (87.5%, peripapillary choroids were involved. The melanocytomas of 8 cases (100% presented as optically empty spaces. Vitreous seeds were found in one case (12.5%. CONCLUSION: IR-AF imaging may provide a new modality to evaluate the pathologic features of ODMs, and together with SW-AF imaging, offers a new tool to study biological characteristics associated with ODMs. SD-OCT is a valuable tool in delimitating the tumor extension and providing morphological information about the adjacent retinal tissue.

  5. PREVALENCE OF FOVEOLAR LUCENCY WITH DIFFERENT GAS TAMPONADES IN SURGICALLY CLOSED MACULAR HOLES ASSESSED BY SPECTRAL DOMAIN OPTICAL COHERENCE TOMOGRAPHY.

    Science.gov (United States)

    Zarranz-Ventura, Javier; Ellabban, Abdallah A; Sim, Dawn A; Keane, Pearse A; Kirkpatrick, James N; Sallam, Ahmed A B

    2017-07-07

    To evaluate the prevalence of foveolar lucency (FL) in surgically closed macular holes by spectral domain optical coherence tomography. One hundred forty-two eyes of 132 patients underwent pars plana vitrectomy, internal limiting membrane peeling, and gas tamponade in a 60-month time frame. Anatomical success and FL rates assessed by spectral domain optical coherence tomography, mean preoperative, and postoperative best-measured visual acuity and surgical details were retrospectively analyzed. Spectral domain optical coherence tomography confirmed closed holes with FL in 33.7% (34/101) of eyes at 1 month, 7.3% (9/123) at 3 months, 4.6% (6/129) at 6 months, and 3% (4/133) at 12 months. Prevalence of FL in closed holes at Month 1 was lower in C3F8-treated eyes (9.5%, 2/21) compared with C2F6 (40.9%, 18/44, P = 0.03) and SF6-treated eyes (38.9%, 14/36, P = 0.05). No differences were observed at Month 3. No differences in best-measured visual acuity change were observed between closed holes with or without FL at Month 1 (-0.14 ± 0.19 vs. -0.11 ± 0.23, P = 0.48) or any of the other time points. Temporary FL is a highly prevalent feature in successfully closed macular holes. Eyes treated with C3F8 gas had lower rates of FL at Month 1 than C2F6 and SF6-treated eyes. The presence of FL in closed holes does not seem to have any effect on the visual outcomes.

  6. Clinical manifestations of optic pit maculopathy as demonstrated by spectral domain optical coherence tomography.

    Science.gov (United States)

    Tzu, Jonathan H; Flynn, Harry W; Berrocal, Audina M; Smiddy, William E; Murray, Timothy G; Fisher, Yale L

    2013-01-01

    The purpose of this retrospective study was to evaluate the characteristic features, including spectral-domain optical coherence tomography (SD-OCT), clinical course, and outcome of treatment if given for patients with optic disc pit maculopathy. We investigated a consecutive series of patients with a diagnosis of optic pit maculopathy treated between 2001 and 2012 at the Bascom Palmer Eye Institute. Patients were divided into two main groups, ie, patients who were observed without surgery and patients who received surgical intervention. The main outcome measures were presenting and final visual acuity, and changes in SD-OCT imaging were recorded. Other data including age, gender, eye, age of onset, length of follow-up, location of optic pit, and location of fluid by OCT were also recorded. On OCT, 67% (12/18) of the eyes showed schisis-like cavities, 22% (4/18) had only subretinal fluid, and 17% (3/18) had only a schisis-like cavity without subretinal fluid. In the patients managed by observation, visual acuity was ≥20/200 in 6/8 eyes initially and 6/8 eyes at last follow-up. Ten of 18 patients received either focal laser, surgery or both. Six of 10 eyes undergoing surgery had initial visual acuity ≥ 20/200, and 8 of 10 eyes undergoing surgery had a visual acuity of ≥20/200 at last follow-up. In this study, many eyes were observed and remained stable during follow-up. In eyes with reduced vision, surgical intervention produced variable outcomes, and persistent intraretinal/subretinal fluid was a common occurrence.

  7. Preclinical evaluation and intraoperative human retinal imaging with a high-resolution microscope-integrated spectral domain optical coherence tomography device.

    Science.gov (United States)

    Hahn, Paul; Migacz, Justin; O'Donnell, Rachelle; Day, Shelley; Lee, Annie; Lin, Phoebe; Vann, Robin; Kuo, Anthony; Fekrat, Sharon; Mruthyunjaya, Prithvi; Postel, Eric A; Izatt, Joseph A; Toth, Cynthia A

    2013-01-01

    The authors have recently developed a high-resolution microscope-integrated spectral domain optical coherence tomography (MIOCT) device designed to enable OCT acquisition simultaneous with surgical maneuvers. The purpose of this report is to describe translation of this device from preclinical testing into human intraoperative imaging. Before human imaging, surgical conditions were fully simulated for extensive preclinical MIOCT evaluation in a custom model eye system. Microscope-integrated spectral domain OCT images were then acquired in normal human volunteers and during vitreoretinal surgery in patients who consented to participate in a prospective institutional review board-approved study. Microscope-integrated spectral domain OCT images were obtained before and at pauses in surgical maneuvers and were compared based on predetermined diagnostic criteria to images obtained with a high-resolution spectral domain research handheld OCT system (HHOCT; Bioptigen, Inc) at the same time point. Cohorts of five consecutive patients were imaged. Successful end points were predefined, including ≥80% correlation in identification of pathology between MIOCT and HHOCT in ≥80% of the patients. Microscope-integrated spectral domain OCT was favorably evaluated by study surgeons and scrub nurses, all of whom responded that they would consider participating in human intraoperative imaging trials. The preclinical evaluation identified significant improvements that were made before MIOCT use during human surgery. The MIOCT transition into clinical human research was smooth. Microscope-integrated spectral domain OCT imaging in normal human volunteers demonstrated high resolution comparable to tabletop scanners. In the operating room, after an initial learning curve, surgeons successfully acquired human macular MIOCT images before and after surgical maneuvers. Microscope-integrated spectral domain OCT imaging confirmed preoperative diagnoses, such as full-thickness macular hole

  8. Structure-function relationships using spectral-domain optical coherence tomography: comparison with scanning laser polarimetry.

    Science.gov (United States)

    Aptel, Florent; Sayous, Romain; Fortoul, Vincent; Beccat, Sylvain; Denis, Philippe

    2010-12-01

    To evaluate and compare the regional relationships between visual field sensitivity and retinal nerve fiber layer (RNFL) thickness as measured by spectral-domain optical coherence tomography (OCT) and scanning laser polarimetry. Prospective cross-sectional study. One hundred and twenty eyes of 120 patients (40 with healthy eyes, 40 with suspected glaucoma, and 40 with glaucoma) were tested on Cirrus-OCT, GDx VCC, and standard automated perimetry. Raw data on RNFL thickness were extracted for 256 peripapillary sectors of 1.40625 degrees each for the OCT measurement ellipse and 64 peripapillary sectors of 5.625 degrees each for the GDx VCC measurement ellipse. Correlations between peripapillary RNFL thickness in 6 sectors and visual field sensitivity in the 6 corresponding areas were evaluated using linear and logarithmic regression analysis. Receiver operating curve areas were calculated for each instrument. With spectral-domain OCT, the correlations (r(2)) between RNFL thickness and visual field sensitivity ranged from 0.082 (nasal RNFL and corresponding visual field area, linear regression) to 0.726 (supratemporal RNFL and corresponding visual field area, logarithmic regression). By comparison, with GDx-VCC, the correlations ranged from 0.062 (temporal RNFL and corresponding visual field area, linear regression) to 0.362 (supratemporal RNFL and corresponding visual field area, logarithmic regression). In pairwise comparisons, these structure-function correlations were generally stronger with spectral-domain OCT than with GDx VCC and with logarithmic regression than with linear regression. The largest areas under the receiver operating curve were seen for OCT superior thickness (0.963 ± 0.022; P polarimetry, and was better expressed logarithmically than linearly. Measurements with these 2 instruments should not be considered to be interchangeable. Copyright © 2010 Elsevier Inc. All rights reserved.

  9. WIDEFIELD SPECTRAL-DOMAIN OPTICAL COHERENCE TOMOGRAPHY IMAGING OF PERIPHERAL ROUND RETINAL HOLES WITH OR WITHOUT RETINAL DETACHMENT.

    Science.gov (United States)

    Casswell, Edward J; Abou Ltaif, Sleiman; Carr, Thomas; Keane, Pearse A; Charteris, David G; Wickham, Louisa

    2018-03-02

    To describe the widefield spectral-domain optical coherence tomography features of peripheral round retinal holes, with or without associated retinal detachment (RD). Retrospective, observational study of 28 eyes with peripheral round retinal holes, with and without RD. Patients underwent imaging with a widefield 50-degree spectral-domain optical coherence tomography (Heidelberg Engineering, Germany) and Optos ultra-widefield imaging systems (Optos, United Kingdom). Vitreous attachment at the site of the retinal hole was detected in 27/28 (96.4%) cases. Cases were split into three groups: RHs with RD (n = 12); RHs with subretinal fluid (n = 5), and flat RHs (n = 11), with minimal or no subretinal fluid. 91.6% retinal holes associated with subretinal fluid or RD had vitreous attachment at the site of the hole. Eighty percent had vitreous attachment at both edges of the retinal hole, in a U-shape configuration, which appeared to exert traction. By contrast, flat retinal holes had visible vitreous attachment only at one edge of the retinal hole in 45.4%. Vitreous attachment was commonly seen at the site of round retinal holes. Vitreous attachment at both edges of the retinal hole in a U-shape configuration was more commonly seen at holes associated with subretinal fluid or RD.

  10. 3-D segmentation of retinal blood vessels in spectral-domain OCT volumes of the optic nerve head

    Science.gov (United States)

    Lee, Kyungmoo; Abràmoff, Michael D.; Niemeijer, Meindert; Garvin, Mona K.; Sonka, Milan

    2010-03-01

    Segmentation of retinal blood vessels can provide important information for detecting and tracking retinal vascular diseases including diabetic retinopathy, arterial hypertension, arteriosclerosis and retinopathy of prematurity (ROP). Many studies on 2-D segmentation of retinal blood vessels from a variety of medical images have been performed. However, 3-D segmentation of retinal blood vessels from spectral-domain optical coherence tomography (OCT) volumes, which is capable of providing geometrically accurate vessel models, to the best of our knowledge, has not been previously studied. The purpose of this study is to develop and evaluate a method that can automatically detect 3-D retinal blood vessels from spectral-domain OCT scans centered on the optic nerve head (ONH). The proposed method utilized a fast multiscale 3-D graph search to segment retinal surfaces as well as a triangular mesh-based 3-D graph search to detect retinal blood vessels. An experiment on 30 ONH-centered OCT scans (15 right eye scans and 15 left eye scans) from 15 subjects was performed, and the mean unsigned error in 3-D of the computer segmentations compared with the independent standard obtained from a retinal specialist was 3.4 +/- 2.5 voxels (0.10 +/- 0.07 mm).

  11. Retinal nerve fiber and optic disc morphology using spectral-domain optical coherence tomography in scleroderma patients.

    Science.gov (United States)

    Sahin-Atik, Sevinc; Koc, Feray; Akin-Sari, Sirin; Ozmen, Mustafa

    2017-05-11

    To evaluate the optic nerve head parameters and peripapillary retinal nerve fiber layer using spectral-domain optical coherence tomography (SD-OCT) in a systemic sclerosis (SSc) cohort and age-matched controls to determine whether SSc patients have an increased risk of normal-tension glaucoma (NTG). We examined 30 patients (3 male, 27 female) with SSc and 28 age- and sex-matched controls. Retinal nerve fiber and optic disc morphology were evaluated using Cirrus SD-OCT. Optic disc morphology measurements including disc area, rim area, average and vertical cup/disc (C/D) ratio, and cup volume were not significantly different between the study groups. The average and 4-quadrant retinal nerve fiber layer (RNFL) measurements of the C/D >0.3 subgroups were not significantly different in the patients and controls. These values were also similar for the C/D >0.5 subgroups except that the average inferior quadrant RNFL thickness of the right eyes in the patient subgroup was significantly thinner than in the control subgroup (p<0.05). Our SSc cohort had relatively shorter disease duration but increased prevalence of early glaucomatous damage signs. Our findings indicate that SSc is a risk factor for developing normal-tension glaucoma. Further studies combined with visual field evaluation are necessary to identify the long-term glaucomatous effects of SSc.

  12. UTILIZATION OF FUNDUS AUTOFLUORESCENCE, SPECTRAL DOMAIN OPTICAL COHERENCE TOMOGRAPHY, AND ENHANCED DEPTH IMAGING IN THE CHARACTERIZATION OF BIETTI CRYSTALLINE DYSTROPHY IN DIFFERENT STAGES.

    Science.gov (United States)

    Li, Qian; Li, Yang; Zhang, Xiaohui; Xu, Zhangxing; Zhu, Xiaoqing; Ma, Kai; She, Haicheng; Peng, Xiaoyan

    2015-10-01

    To characterize Bietti crystalline dystrophy (BCD) in different stages using multiple imaging modalities. Sixteen participants clinically diagnosed as BCD were included in the retrospective study and were categorized into 3 stages according to fundus photography. Eleven patients were genetically confirmed. Fundus autofluorescence, spectral domain optical coherence tomography, and enhanced depth imaging features of BCD were analyzed. On fundus autofluorescence, the abnormal autofluorescence was shown to enlarge in area and decrease in intensity with stages. Using spectral domain optical coherence tomography, the abnormalities in Stage 1 were observed to localize in outer retinal layers, whereas in Stage 2 and Stage 3, more extensive retinal atrophy was seen. In enhanced depth imaging, the subfoveal choroidal layers were delineated clearly in Stage 1; in Stage 2, destructions were primarily found in the choriocapillaris with associated alterations in the outer vessels; Stage 3 BCD displayed severe choroidal thinning. Choroidal neovascularization and macular edema were exhibited with high incidence. IVS6-8del17bp/inGC of the CYP4V2 gene was the most common mutant allele. Noninvasive fundus autofluorescence, spectral domain optical coherence tomography, and enhanced depth imaging may help to characterize the chorioretinal pathology of BCD at different degrees, and therefore, we propose staging of BCD depending on those methods. Physicians should be cautious of the vision-threatening complications of the disease.

  13. Development of a low-cost, 11 µm spectral domain optical coherence tomography surface profilometry prototype

    Science.gov (United States)

    Suliali, Nyasha J.; Baricholo, Peter; Neethling, Pieter H.; Rohwer, Erich G.

    2017-06-01

    A spectral-domain Optical Coherence Tomography (OCT) surface profilometry prototype has been developed for the purpose of surface metrology of optical elements. The prototype consists of a light source, spectral interferometer, sample fixture and software currently running on Microsoft® Windows platforms. In this system, a broadband light emitting diode beam is focused into a Michelson interferometer with a plane mirror as its sample fixture. At the interferometer output, spectral interferograms of broadband sources were measured using a Czerny-Turner mount monochromator with a 2048-element complementary metal oxide semiconductor linear array as the detector. The software performs importation and interpolation of interferometer spectra to pre-condition the data for image computation. One dimensional axial OCT images were computed by Fourier transformation of the measured spectra. A first reflection surface profilometry (FRSP) algorithm was then formulated to perform imaging of step-function-surfaced samples. The algorithm re-constructs two dimensional colour-scaled slice images by concatenation of 21 and 13 axial scans to form a 10 mm and 3.0 mm slice respectively. Measured spectral interferograms, computed interference fringe signals and depth reflectivity profiles were comparable to simulations and correlated to displacements of a single reflector linearly translated about the arm null-mismatch point. Surface profile images of a double-step-function-surfaced sample, embedded with inclination and crack detail were plotted with an axial resolution of 11 μm. The surface shape, defects and misalignment relative to the incident beam were detected to the order of a micron, confirming high resolution of the developed system as compared to electro-mechanical surface profilometry techniques.

  14. Retinal Imaging of Infants on Spectral Domain Optical Coherence Tomography

    Directory of Open Access Journals (Sweden)

    Anand Vinekar

    2015-01-01

    Full Text Available Spectral domain coherence tomography (SD OCT has become an important tool in the management of pediatric retinal diseases. It is a noncontact imaging device that provides detailed assessment of the microanatomy and pathology of the infant retina with a short acquisition time allowing office examination without the requirement of anesthesia. Our understanding of the development and maturation of the infant fovea has been enhanced by SD OCT allowing an in vivo assessment that correlates with histopathology. This has helped us understand the critical correlation of foveal development with visual potential in the first year of life and beyond. In this review, we summarize the recent literature on the clinical applications of SD OCT in studying the pathoanatomy of the infant macula, its ability to detect subclinical features, and its correlation with disease and vision. Retinopathy of prematurity and macular edema have been discussed in detail. The review also summarizes the current status of SD OCT in other infant retinal conditions, imaging the optic nerve, the choroid, and the retinal nerve fibre in infants and children, and suggests future areas of research.

  15. High-speed spectral domain optical coherence tomography using non-uniform fast Fourier transform

    Science.gov (United States)

    Chan, Kenny K. H.; Tang, Shuo

    2010-01-01

    The useful imaging range in spectral domain optical coherence tomography (SD-OCT) is often limited by the depth dependent sensitivity fall-off. Processing SD-OCT data with the non-uniform fast Fourier transform (NFFT) can improve the sensitivity fall-off at maximum depth by greater than 5dB concurrently with a 30 fold decrease in processing time compared to the fast Fourier transform with cubic spline interpolation method. NFFT can also improve local signal to noise ratio (SNR) and reduce image artifacts introduced in post-processing. Combined with parallel processing, NFFT is shown to have the ability to process up to 90k A-lines per second. High-speed SD-OCT imaging is demonstrated at camera-limited 100 frames per second on an ex-vivo squid eye. PMID:21258551

  16. Comparison of retina specialist preferences regarding spectral-domain and swept-source optical coherence tomography angiography

    Directory of Open Access Journals (Sweden)

    Su GL

    2017-05-01

    Full Text Available Grace L Su,1 Douglas M Baughman,2 Qinqin Zhang,3 Kasra Rezaei,2 Aaron Y Lee,2 Cecilia S Lee2 1Lewis Katz School of Medicine, Temple University, Philadelphia, PA, 2Department of Ophthalmology, 3Department of Bioengineering, University of Washington, Seattle, WA, USA Purpose: The aim of this study was to compare physician preferences regarding the commercially available spectral-domain (SD optical coherence tomography angiography (OCTA and swept-source (SS OCTA prototype device.Design: Comparative analysis of diagnostic instruments was performed.Patients and methods: Subjects at the University of Washington Eye Institute and Harborview Medical Center were prospectively recruited and imaged with the Zeiss SD OCTA (HD-5000, Angioplex and Zeiss SS OCTA (Plex Elite, Everest devices on the same day. The study included 10 eyes from 10 subjects diagnosed with a retinal/choroidal disease. Deidentified images were compiled into a survey and sent to retina specialists in various countries. The survey presented masked SD and SS images of each eye for each retinal sublayer side by side. Respondents were asked about their image preference and impact on clinical management. A priori and post hoc preferences for SD vs SS were collected.Results: Fifty-four retina specialists responded to the survey. Median years in practice was 3.00 (interquartile range [IQR] 1.50–17.00. At baseline, 23 (48% physicians owned an OCTA machine. The majority of physician responses showed a preference for the SS over SD OCTA, independent of the retinal pathology shown (n=454 overall responses, 74%. Nevertheless, the majority indicated that both SD and SS would be equally valuable in informing clinical decisions (n=374 overall responses, 61%.Conclusion: These findings indicate that the majority of retina specialists surveyed prefer SS over SD OCTA based on image quality, regardless of the retinal pathology shown. Regarding the clinical utility of each modality, the majority of

  17. Do different spectral domain OCT hardwares measure the same? Comparison of retinal thickness using third-party software

    DEFF Research Database (Denmark)

    Sander, Birgit; Ahmad Al-Abiji, Hajer; Kofod, Mads

    2015-01-01

    Purpose Spectral-domain optical coherence tomographies (OCTs) from different companies do not give identical retinal thicknesses. The purpose of this study was to evaluate if differences in thickness when using a spectral domain Cirrus OCT or a Heidelberg Spectralis are due to hardware difference...

  18. OTDM-WDM Conversion Based on Time-Domain Optical Fourier Transformation with Spectral Compression

    DEFF Research Database (Denmark)

    Mulvad, Hans Christian Hansen; Palushani, Evarist; Galili, Michael

    2011-01-01

    We propose a scheme enabling direct serial-to-parallel conversion of OTDM data tributaries onto a WDM grid, based on optical Fourier transformation with spectral compression. Demonstrations on 320 Gbit/s and 640 Gbit/s OTDM data are shown.......We propose a scheme enabling direct serial-to-parallel conversion of OTDM data tributaries onto a WDM grid, based on optical Fourier transformation with spectral compression. Demonstrations on 320 Gbit/s and 640 Gbit/s OTDM data are shown....

  19. Dynamic virtual optical network embedding in spectral and spatial domains over elastic optical networks with multicore fibers

    Science.gov (United States)

    Zhu, Ruijie; Zhao, Yongli; Yang, Hui; Tan, Yuanlong; Chen, Haoran; Zhang, Jie; Jue, Jason P.

    2016-08-01

    Network virtualization can eradicate the ossification of the infrastructure and stimulate innovation of new network architectures and applications. Elastic optical networks (EONs) are ideal substrate networks for provisioning flexible virtual optical network (VON) services. However, as network traffic continues to increase exponentially, the capacity of EONs will reach the physical limitation soon. To further increase network flexibility and capacity, the concept of EONs is extended into the spatial domain. How to map the VON onto substrate networks by thoroughly using the spectral and spatial resources is extremely important. This process is called VON embedding (VONE).Considering the two kinds of resources at the same time during the embedding process, we propose two VONE algorithms, the adjacent link embedding algorithm (ALEA) and the remote link embedding algorithm (RLEA). First, we introduce a model to solve the VONE problem. Then we design the embedding ability measurement of network elements. Based on the network elements' embedding ability, two VONE algorithms were proposed. Simulation results show that the proposed VONE algorithms could achieve better performance than the baseline algorithm in terms of blocking probability and revenue-to-cost ratio.

  20. Spectral-domain optical coherence tomography findings of the macula in 500 consecutive patients with uveitis.

    Science.gov (United States)

    Grajewski, R S; Boelke, A C; Adler, W; Meyer, S; Caramoy, A; Kirchhof, B; Cursiefen, C; Heindl, L M

    2016-11-01

    PurposeTo analyze the macular structure in a large series of consecutive patients with different types of uveitis using spectral-domain optical coherence tomography (SD-OCT).Patients and methodsFive hundred eyes of 500 consecutive patients with anterior, intermediate, posterior, and panuveitis underwent standardized macular examination using SD-OCT. Central retinal thickness (CRT), macular volume (MV), and presence of cystoid macular edema (CME), diffuse macular edema (DME), serous retinal detachment (SRD), epiretinal membrane with (ERM+) and without (ERM-) retinal surface wrinkling were determined.ResultsThe anatomic location of inflammation affected significantly CRT and MV (Pmacula is recommended for all uveitis patients. CRT, MV, and the incidence of CME were highest in intermediate and panuveitis.

  1. Optical coherence tomography-based decision making in exudative age-related macular degeneration: comparison of time- vs spectral-domain devices.

    Science.gov (United States)

    Cukras, C; Wang, Y D; Meyerle, C B; Forooghian, F; Chew, E Y; Wong, W T

    2010-05-01

    To determine whether optical coherence tomography (OCT) device-type influences clinical grading of OCT imaging in the context of exudative age-related macular degeneration (AMD). Ninety-six paired OCT scans from 49 patients with active exudative AMD were obtained on both the time-domain Stratus OCT system and the spectral-domain Cirrus OCT system at the same visit. Three independent graders judged each scan for the presence of intraretinal fluid (IRF) or subretinal fluid (SRF). The degree of grader consensus was evaluated and the ability of the systems to detect the presence of disease activity was analysed. Cirrus OCT generated a higher degree of inter-grader consensus than Stratus OCT with higher intraclass correlation coefficients for all parameters analysed. A pair-wise comparison of Cirrus OCT with Stratus OCT systems revealed that Cirrus-based gradings more frequently reported the presence of SRF and IRF and detected overall neovascular activity at a higher rate (P<0.05) compared with Stratus-based gradings. The choice of time-domain (Stratus) vs spectra-domain (Cirrus) OCT systems has a measurable impact on clinical decision making in exudative AMD. Spectral-domain OCT systems may be able to generate more consensus in clinical interpretation and, in particular cases, detect disease activity not detected by time-domain systems. Clinical trials using OCT-based clinical evaluations of exudative AMD may need to account for these inter-system differences in planning and analysis.

  2. Optical Coherence Tomography-Based Decision Making in Exudative Age-related Macular Degeneration: Comparison of Time- versus Spectral-Domain Devices

    Science.gov (United States)

    Cukras, Catherine; Wang, Yunqing D.; Meyerle, Catherine B.; Forooghian, Farzin; Chew, Emily Y.; Wong, Wai T.

    2010-01-01

    Purpose To determine if optical coherence tomography (OCT) device-type influences clinical grading of OCT imaging in the context of exudative age-related macular degeneration (AMD). Methods Ninety-six paired OCT scans from 49 patients with active exudative AMD were obtained on both the time-domain Stratus™ OCT system and the spectral-domain Cirrus™ OCT system at the same visit. Three independent graders judged each scan for the presence of intraretinal fluid (IRF) or subretinal fluid (SRF). The degree of grader consensus was evaluated and the ability of the systems to detect the presence of disease activity was analyzed. Results Cirrus™ OCT generated a higher degree of inter-grader consensus than Stratus OCT with higher intraclass correlation coefficients (ICC) for all parameters analyzed. A pair-wise comparison of Cirrus™ OCT to Stratus™ OCT systems revealed that Cirrus™-based gradings more frequently reported the presence of SRF and IRF and detected overall neovascular activity at a higher rate (p<0.05) compared to Stratus™-based gradings Conclusions The choice of time-domain (Stratus™) versus spectra-domain (Cirrus™) OCT systems has a measurable impact on clinical decision making in exudative AMD. Spectral-domain OCT systems may be able to generate more consensus in clinical interpretation and, in particular cases, detect disease activity not detected by time-domain systems. Clinical trials employing OCT-based clinical evaluations of exudative AMD may need to account for these inter-system differences in planning and analysis. PMID:19696804

  3. Ultra-Widefield Steering-Based Spectral-Domain Optical Coherence Tomography Imaging of the Retinal Periphery.

    Science.gov (United States)

    Choudhry, Netan; Golding, John; Manry, Matthew W; Rao, Rajesh C

    2016-06-01

    To describe the spectral-domain optical coherence tomography (SD OCT) features of peripheral retinal findings using an ultra-widefield (UWF) steering technique to image the retinal periphery. Observational study. A total of 68 patients (68 eyes) with 19 peripheral retinal features. Spectral-domain OCT-based structural features. Nineteen peripheral retinal features, including vortex vein, congenital hypertrophy of the retinal pigment epithelium, pars plana, ora serrata pearl, typical cystoid degeneration (TCD), cystic retinal tuft, meridional fold, lattice and cobblestone degeneration, retinal hole, retinal tear, rhegmatogenous retinal detachment, typical degenerative senile retinoschisis, peripheral laser coagulation scars, ora tooth, cryopexy scars (retinal tear and treated retinoblastoma scar), bone spicules, white without pressure, and peripheral drusen, were identified by peripheral clinical examination. Near-infrared scanning laser ophthalmoscopy images and SD OCT of these entities were registered to UWF color photographs. Spectral-domain OCT resolved structural features of all peripheral findings. Dilated hyporeflective tubular structures within the choroid were observed in the vortex vein. Loss of retinal lamination, neural retinal attenuation, retinal pigment epithelium loss, or hypertrophy was seen in several entities, including congenital hypertrophy of the retinal pigment epithelium, ora serrata pearl, TCD, cystic retinal tuft, meridional fold, lattice, and cobblestone degenerations. Hyporeflective intraretinal spaces, indicating cystoid or schitic fluid, were seen in ora serrata pearl, ora tooth, TCD, cystic retinal tuft, meridional fold, retinal hole, and typical degenerative senile retinoschisis. The vitreoretinal interface, which often consisted of lamellae-like structures of the condensed cortical vitreous near or adherent to the neural retina, appeared clearly in most peripheral findings, confirming its association with many low-risk and vision

  4. Time domain spectral phase encoding/DPSK data modulation using single phase modulator for OCDMA application.

    Science.gov (United States)

    Wang, Xu; Gao, Zhensen; Kataoka, Nobuyuki; Wada, Naoya

    2010-05-10

    A novel scheme using single phase modulator for simultaneous time domain spectral phase encoding (SPE) signal generation and DPSK data modulation is proposed and experimentally demonstrated. Array- Waveguide-Grating and Variable-Bandwidth-Spectrum-Shaper based devices can be used for decoding the signal directly in spectral domain. The effects of fiber dispersion, light pulse width and timing error on the coding performance have been investigated by simulation and verified in experiment. In the experiment, SPE signal with 8-chip, 20GHz/chip optical code patterns has been generated and modulated with 2.5 Gbps DPSK data using single modulator. Transmission of the 2.5 Gbps data over 34km fiber with BEROCDMA) and secure optical communication applications. (c) 2010 Optical Society of America.

  5. Adaptive optics parallel spectral domain optical coherence tomography for imaging the living retina

    Science.gov (United States)

    Zhang, Yan; Rha, Jungtae; Jonnal, Ravi S.; Miller, Donald T.

    2005-06-01

    Although optical coherence tomography (OCT) can axially resolve and detect reflections from individual cells, there are no reports of imaging cells in the living human retina using OCT. To supplement the axial resolution and sensitivity of OCT with the necessary lateral resolution and speed, we developed a novel spectral domain OCT (SD-OCT) camera based on a free-space parallel illumination architecture and equipped with adaptive optics (AO). Conventional flood illumination, also with AO, was integrated into the camera and provided confirmation of the focus position in the retina with an accuracy of ±10.3 μm. Short bursts of narrow B-scans (100x560 μm) of the living retina were subsequently acquired at 500 Hz during dynamic compensation (up to 14 Hz) that successfully corrected the most significant ocular aberrations across a dilated 6 mm pupil. Camera sensitivity (up to 94 dB) was sufficient for observing reflections from essentially all neural layers of the retina. Signal-to-noise of the detected reflection from the photoreceptor layer was highly sensitive to the level of cular aberrations and defocus with changes of 11.4 and 13.1 dB (single pass) observed when the ocular aberrations (astigmatism, 3rd order and higher) were corrected and when the focus was shifted by 200 μm (0.54 diopters) in the retina, respectively. The 3D resolution of the B-scans (3.0x3.0x5.7 μm) is the highest reported to date in the living human eye and was sufficient to observe the interface between the inner and outer segments of individual photoreceptor cells, resolved in both lateral and axial dimensions. However, high contrast speckle, which is intrinsic to OCT, was present throughout the AO parallel SD-OCT B-scans and obstructed correlating retinal reflections to cell-sized retinal structures.

  6. A spectral analysis of the domain decomposed Monte Carlo method for linear systems

    Energy Technology Data Exchange (ETDEWEB)

    Slattery, S. R.; Wilson, P. P. H. [Engineering Physics Department, University of Wisconsin - Madison, 1500 Engineering Dr., Madison, WI 53706 (United States); Evans, T. M. [Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37830 (United States)

    2013-07-01

    The domain decomposed behavior of the adjoint Neumann-Ulam Monte Carlo method for solving linear systems is analyzed using the spectral properties of the linear operator. Relationships for the average length of the adjoint random walks, a measure of convergence speed and serial performance, are made with respect to the eigenvalues of the linear operator. In addition, relationships for the effective optical thickness of a domain in the decomposition are presented based on the spectral analysis and diffusion theory. Using the effective optical thickness, the Wigner rational approximation and the mean chord approximation are applied to estimate the leakage fraction of stochastic histories from a domain in the decomposition as a measure of parallel performance and potential communication costs. The one-speed, two-dimensional neutron diffusion equation is used as a model problem to test the models for symmetric operators. In general, the derived approximations show good agreement with measured computational results. (authors)

  7. A spectral analysis of the domain decomposed Monte Carlo method for linear systems

    International Nuclear Information System (INIS)

    Slattery, S. R.; Wilson, P. P. H.; Evans, T. M.

    2013-01-01

    The domain decomposed behavior of the adjoint Neumann-Ulam Monte Carlo method for solving linear systems is analyzed using the spectral properties of the linear operator. Relationships for the average length of the adjoint random walks, a measure of convergence speed and serial performance, are made with respect to the eigenvalues of the linear operator. In addition, relationships for the effective optical thickness of a domain in the decomposition are presented based on the spectral analysis and diffusion theory. Using the effective optical thickness, the Wigner rational approximation and the mean chord approximation are applied to estimate the leakage fraction of stochastic histories from a domain in the decomposition as a measure of parallel performance and potential communication costs. The one-speed, two-dimensional neutron diffusion equation is used as a model problem to test the models for symmetric operators. In general, the derived approximations show good agreement with measured computational results. (authors)

  8. Enhanced spectral domain optical coherence tomography for pathological and functional studies

    Science.gov (United States)

    Yuan, Zhijia

    Optical coherence tomography (OCT) is a novel technique that enables noninvasive or minimally invasive, cross-sectional imaging of biological tissue at sub-10mum spatial resolution and up to 2-3mm imaging depth. Numerous technological advances have emerged in recent years that have shown great potential to develop OCT into a powerful imaging and diagnostic tools. In particular, the implementation of Fourier-domain OCT (FDOCT) is a major step forward that leads to greatly improved imaging rate and image fidelity of OCT. This dissertation summarizes the work that focuses on enhancing the performances and functionalities of spectral radar based FDOCT (SDOCT) for pathological and functional applications. More specifically, chapters 1-4 emphasize on the development of SDOCT and its utility in pathological studies, including cancer diagnosis. The principle of SDOCT is first briefly outlined, followed by the design of our bench-top SDOCT systems with emphasis on spectral linear interpolation, calibration and system dispersion compensation. For ultrahigh-resolution SDOCT, time-lapse image registration and frame averaging is introduced to effectively reduce speckle noise and uncover subcellular details, showing great promise for enhancing the diagnosis of carcinoma in situ. To overcome the image depth limitation of OCT, a dual-modal imaging method combing SDOCT with high-frequency ultrasound is proposed and examined in animal cancer models to enhance the sensitivity and staging capabilities for bladder cancer diagnosis. Chapters 5-7 summarize the work on developing Doppler SDOCT for functional studies. Digital-frequency-ramping OCT (DFR-OCT) is developed in the study, which has demonstrated the ability to significantly improve the signal-to-noise ratio and thus sensitivity for retrieving subsurface blood flow imaging. New DFR algorithms and imaging processing methods are discussed to further enhance cortical CBF imaging. Applications of DFR-OCT for brain functional studies

  9. Spectral-domain optical coherence tomography of macula in myopia.

    Science.gov (United States)

    Choovuthayakorn, Janejit; Laowong, Taksaorn; Watanachai, Nawat; Patikulsila, Direk; Chaikitmongkol, Voraporn

    2016-06-01

    The aim of this study is to determine the associations between regional macular thickness and gender, age, axial length, and degree of myopia in young and middle-aged healthy myopic eyes. One hundred and seventy-one subjects with -0.5 diopters of myopia or worse underwent prospective macular thickness measurement by Spectralis spectral-domain optical coherence tomography. Subjects' mean age was 32.40 ± 8.25 years (range 18 to 49 years), with 45 % being male. The mean degree of myopia was -4.57 ± 3.52 diopters, with a mean axial length of 25.09 ± 1.67 mm. Multivariate regression analysis demonstrated significantly thicker central (mean 9.13 µm thicker) and inner subfields (mean 8.55 µm thicker) in males (P values were <0.001 and 0.002, respectively). In addition, in both genders, for each millimeter of increased axial length, the central subfield thickness increased by 2.11 µm, the inner subfield decreased by 2.25 µm, and the outer subfield decreased by 3.62 µm (P values were 0.010, <0.001, and <0.001, respectively). Factors including gender and axial length affect baseline regional macular thickness in young and middle-age myopic subjects. The central subfield and inner subfield were affected by both gender and axial length, while the outer subfield was affected only by axial length. The macular thickness of myopic subjects with macular disease should be interpreted in light of these factors.

  10. Spectral domain optical coherence tomography as an effective screening test for hydroxychloroquine retinopathy (the “flying saucer” sign

    Directory of Open Access Journals (Sweden)

    Eric Chen

    2010-10-01

    Full Text Available Eric Chen, David M Brown, Matthew S Benz, Richard H Fish, Tien P Wong, Rosa Y Kim, James C MajorRetina Consultants of Houston, The Methodist Hospital, Houston, Texas, USAPurpose: While the long-term incidence of hydroxychloroquine (HCQ retinopathy is low, there remains no definitive clinical screening test to recognize HCQ toxicity before ophthalmoscopic fundus changes or visual symptoms. Patients receiving HCQ were evaluated with spectral domain optical coherence tomography (SD OCT to assess the feasibility of identifying HCQ retinopathy at an early stage.Methods: Twenty-five patients referred for the evaluation of hydroxychloroquine toxicity underwent a comprehensive ocular examination, Humphrey visual field (HVF perimetry, time domain OCT, and SD OCT. Some patients with screening abnormalities also underwent further diagnostic testing at the discretion of the treating providers.Results: Five patients were found to have SD OCT findings corresponding to HCQ toxicity and retinal damage as seen by clinical exam and/or HVF perimetry. Two patients with advanced toxicity were found to have significant outer retina disruption in the macula on SD OCT. Three patients with early HCQ toxicity and HVF 10-2 perifoveal defects were found to have loss of the perifoveal photoreceptor inner segment/outer segment (IS/OS junction with intact outer retina directly under the fovea, creating the “flying saucer” sign. While two of these three patients had early ophthalmoscopic fundus changes, one had none.Conclusion: Outer retinal abnormalities including perifoveal photoreceptor IS/OS junction disruption can be identified by SD OCT in early HCQ toxicity, sometimes even before ophthalmoscopic fundus changes are apparent. SD OCT may have a potential complementary role in screening for HCQ retinopathy due to its quick acquisition and because it is more objective than automated perimetry.Keywords: drug toxicity, hydroxychloroquine, photoreceptors, screening test

  11. Quantification of retinal nerve fiber layer thickness using spectral domain optical coherence tomography in normal Indian population

    Directory of Open Access Journals (Sweden)

    Tarannum Mansoori

    2012-01-01

    Full Text Available The purpose of this study was to measure peripapillary retinal nerve fiber layer thickness (RNFLT using spectral domain optical coherence tomography (SD-OCT in normal Indian eyes, for which, 210 normal volunteers were recruited. One eye of each subject underwent RNFL scanning at 3.4 mm circle diameter around optic nerve using SD OCT. The data were analyzed to determine RNFLT in the sample population and its variation with age and gender. The average peripapillary RNFLT was 114.03 ± 9.59 μm. There was no effect of gender on RNFLT parameters. Age had significant negative correlation with average (P = 0.005, superior (P = 0.04, temporal (P = 0.049, and nasal quadrants (P = 0.01 RNFLT. Inferior quadrant RNFLT also had a negative correlation with age, but it was not statistically significant (P = 0.15.

  12. Cost-Effective Brillouin Optical Time-Domain Analysis Sensor Using a Single Optical Source and Passive Optical Filtering

    Directory of Open Access Journals (Sweden)

    H. Iribas

    2016-01-01

    Full Text Available We present a simplified configuration for distributed Brillouin optical time-domain analysis sensors that aims to reduce the cost of the sensor by reducing the number of components required for the generation of the two optical waves involved in the sensing process. The technique is based on obtaining the pump and probe waves by passive optical filtering of the spectral components generated in a single optical source that is driven by a pulsed RF signal. The optical source is a compact laser with integrated electroabsorption modulator and the optical filters are based on fiber Bragg gratings. Proof-of-concept experiments demonstrate 1 m spatial resolution over a 20 km sensing fiber with a 0.9 MHz precision in the measurement of the Brillouin frequency shift, a performance similar to that of much more complex setups. Furthermore, we discuss the factors limiting the sensor performance, which are basically related to residual spectral components in the filtering process.

  13. Peripapillary Retinal Nerve Fiber Measurement with Spectral-Domain Optical Coherence Tomography in Age-Related Macular Degeneration

    Directory of Open Access Journals (Sweden)

    Simon K. Law

    2017-12-01

    Full Text Available Purpose: To evaluate the relationship between the peripapillary retinal nerve fiber layer (RNFL measurements with Spectral-domain Optical Coherence Tomography (OCT and Age-related macular degeneration (AMD. Methods: Patients >60 years of age without glaucoma or record of intraocular pressure >21 mmHg and no systemic or intraocular diseases or treatment or surgical intervention that affected the RNFL underwent OCT measurement of the RNFL. The severity of AMD was staged with the Clinical Age-Related Maculopathy Staging System. The relationship between RNFL measurements and AMD stages of one eye per patient was analyzed. Results: Eighty-six eyes (46 patients with AMD and no glaucoma or other exclusion criteria received OCT RNFL measurements. Nine eyes (10.5% were excluded because of distorted peripapillary anatomy from exudative AMD (7 eyes or failure of the RNFL segmentation algorithm (2 eyes. Mean age ± S.D. of the 43 patients analyzed was 81.2 ± 7.3 years. The mean stage ± S.D. of AMD of the 77 eyes was 3.77 ± 1.05. Higher stages of AMD were statistically significantly associated with lower average RNFL and inferior sector RNFL (p = 0.049, 0 0015, respectively. The association of inferior sector RNFL and AMD stage remained statistically significant after adjusting for age. Conclusions: Spectral domain OCT is generally useful in measuring the peripapillary RNFL in eyes with different stages of AMD. Higher stage of AMD is associated with thinner peripapillary RNFL, which may masquerade as early glaucomatous damage.

  14. Evaluation of time domain and spectral domain optical coherence tomography in the measurement of diabetic macular edema.

    Science.gov (United States)

    Forooghian, Farzin; Cukras, Catherine; Meyerle, Catherine B; Chew, Emily Y; Wong, Wai T

    2008-10-01

    To evaluate macular thickness and volume measurements and their intrasession repeatability in two optical coherence tomography (OCT) systems: the Stratus OCT, a time domain system, and the Cirrus HD-OCT, a spectral domain system (both by Carl Zeiss Meditec, Inc., Dublin, CA), in the context of diabetic macular edema (DME). Thirty-three eyes of 33 diabetic patients with clinically significant macular edema (CSME) were scanned in a single session by a single operator on both OCT systems. Macular thickness measurements of nine standard macular subfields and total macular volume were obtained and analyzed. Bland-Altman plots were constructed to assess agreement in macular measurements. Intraclass correlation coefficients (ICCs), coefficients of repeatability (CR(W)), and coefficients of variation (CV(W)) were used to assess intrasession repeatability. Macular thickness in nine retinal subfields and macular volume were significantly higher in the Cirrus HD-OCT system compared with the Stratus OCT system. Subfield thickness and total volume measurements, respectively, were 30 to 55 microm and 3.2 mm(3) greater for the Cirrus HD-OCT system compared with the Stratus OCT system. Both Stratus OCT and Cirrus HD-OCT systems demonstrated high intrasession repeatability, with overlapping ranges for CR(W), CV(W), and ICC. Repeatability measures (CR(W) and CV(W)) differed significantly between systems in only one of nine subfields (outer temporal subfield). Absolute measures of macular thickness and volume in patients with DME differed significantly in magnitude between the Stratus OCT and Cirrus HD-OCT systems. However, both OCT systems demonstrated high intrasessional repeatability. Although the two systems may not be used interchangeably, they appear equally reliable in generating macular measurements for clinical practice and research.

  15. Acute Retinal Pigment Epitheliitis: Spectral Domain Optical Coherence Tomography, Fluorescein Angiography, and Autofluorescence Findings

    Directory of Open Access Journals (Sweden)

    Tuğba Aydoğan

    2015-01-01

    Full Text Available A 17-year-old presented with central and paracentral scotomas in his right eye for one week. There was no remarkable medical or ocular history. Blood analyses were within normal range. At presentation both eyes’ best-corrected visual acuities were 20/20. Slit-lamp examination result was normal. Fundus examination revealed yellow-white hypopigmented areas in the macula. Fluorescein angiography (FA showed hypofluorescence surrounded by ring of hyperfluorescence. Fundus autofluorescence (FAF was slightly increased. Spectral domain optical coherence tomography (SD-OCT showed disruption of IS/OS junction with expansion of abnormal hyperreflectivity from retinal pigment epithelium to the outer nuclear layer (ONL. One month later fundus examination showed disappearance of the lesions. FA revealed transmission hyperfluorescence. FAF showed increased autofluorescence and pigment clumping. Hyperreflective band in SD-OCT disappeared. Loss of photoreceptor segment layers was observed in some of the macular lesions. The diagnosis of acute retinal pigment epitheliitis can be challenging after disappearance of fundus findings. FA, FAF, and SD-OCT are important tests for diagnosis after resolution of the disease.

  16. Management of Patients with Graves’ Disease and Orbital Involvement: Role of Spectral Domain Optical Coherence Tomography

    Directory of Open Access Journals (Sweden)

    Alice Bruscolini

    2018-01-01

    Full Text Available Purpose. To investigate the role of choroidal thickness evaluation with spectral domain optical coherence tomography (SDOCT and enhanced depth imaging (EDI technique in the management of patients with Graves’ disease and orbitopathy (GO. Methods. Thirty-six eyes of 18 patients with GO and 36 eyes of 18 age-matched control subjects were included in this retrospective observational study. All the subjects underwent a complete ophthalmological evaluation, including clinical activity score (CAS and exophthalmometry. The SDOCT images of the choroid were obtained by EDI modality. Results. Choroidal thickness was significantly increased in GO than in control eyes (p<0.01. A significant correlation was found between choroidal thickness and CAS, proptosis, and the duration of disease (p<0.05. Conclusion. This study shows that choroidal thickness, evaluated with EDI-OCT, is significantly increased in patients with GO and correlates with the activity of the disease, proptosis, and duration of the disease. The choroidal thickening may reflect the ocular hemodynamic changes, and enhanced depth imaging optical coherence tomography may be a useful tool for the evaluation of orbital congestion and management of patients with Graves’ disease and orbital involvement.

  17. Spectral domain optical coherence tomography cross-sectional image of optic nerve head during intraocular pressure elevation

    Directory of Open Access Journals (Sweden)

    Ji Young Lee

    2014-12-01

    Full Text Available AIM: To analyze changes of the optic nerve head (ONH and peripapillary region during intraocular pressure (IOP elevation in patients using spectral domain optical coherence tomography (SD-OCT.METHODS: Both an optic disc 200×200 cube scan and a high-definition 5-line raster scan were obtained from open angle glaucoma patients presented with monocular elevation of IOP (≥30 mm Hg using SD-OCT. Additional baseline characteristics included age, gender, diagnosis, best-corrected visual acuity, refractive error, findings of slit lamp biomicroscopy, findings of dilated stereoscopic examination of the ONH and fundus, IOP, pachymetry findings, and the results of visual field.RESULTS: The 24 patients were selected and divided into two groups:group 1 patients had no history of IOP elevation or glaucoma (n=14, and group 2 patients did have history of IOP elevation or glaucoma (n=10. In each patient, the study eye with elevated IOP was classified into group H (high, and the fellow eye was classified into group L (low. The mean deviation (MD differed significantly between groups H and L when all eyes were considered (P=0.047 and in group 2 (P=0.042, not in group 1 (P=0.893. Retinal nerve fiber layer (RNFL average thickness (P=0.050, rim area (P=0.015, vertical cup/disc ratio (P=0.011, cup volume (P=0.028, inferior quadrant RNFL thickness (P=0.017, and clock-hour (1, 5, and 6 RNFL thicknesses (P=0.050, 0.012, and 0.018, respectively, cup depth (P=0.008, central prelaminar layer thickness (P=0.023, mid-inferior prelaminar layer thickness (P=0.023, and nasal retinal slope (P=0.034 were significantly different between the eyes with groups H and L.CONCLUSION:RNFL average thickness, rim area, vertical cup/disc ratio, cup volume, inferior quadrant RNFL thickness, and clock-hour (1, 5, and 6 RNFL thicknesses significantly changed during acute IOP elevation.

  18. The hand-hold polarization-sensitive spectral domain optical coherence and its applications

    Science.gov (United States)

    Liu, Hao; Gao, Wanrong

    2017-08-01

    The polarization-sensitive spectral domain optical coherence tomography (PSOCT) has the advantages of being able to measure the polarization properties of samples, such as phase-retardation, diattenuation, depolarization, and optical axis orientation, providing a contrast to identify the diseased area and normal area in tissues in PSOCT images. Conventionally, the sample arm of PSOCT is fixed on the stage where biomedical tissues or models is placed, and the OCT images is acquired by scanning with a galvanometer-based mirror. To be applied in the practical diagnosis, a promising way is to design a hand-held device. To this end, it is required that probe is assembled with a small volume to allow for comprehensively imaging large tissues areas at a microscopic scale, and is available to move on different samples to be acquired quickly with negligible motion artifacts. Meanwhile, the probe should be manufactured wih well stability to avoid system jitter error while it is used to detect the biological tissues in vivo. In this work, a design of a hand-hold fiber-based PSOCT is described. The device is of the size of 10 cm (length) × 8 cm (width) × 6 cm (height). Both the axial resolution and the imaging depth of the system are measured and were approximately 7 μm and 2.5 mm in air, respectively, which are in good agreement with the theoretical predictions. The A-scan rate of the system is 70 kHz. The structure is compact and all the components are fixed on the shell to reduce the motion artifact, resulting in a great stability on measuring the tissues in vivo. The cross sectional images of ex vivo chicken breast, ex vivo pork cartilage and in vivo forearm skin of human wolunteer are presented to demonstrate the capability of the system.

  19. A hierarchical cluster analysis of normal-tension glaucoma using spectral-domain optical coherence tomography parameters.

    Science.gov (United States)

    Bae, Hyoung Won; Ji, Yongwoo; Lee, Hye Sun; Lee, Naeun; Hong, Samin; Seong, Gong Je; Sung, Kyung Rim; Kim, Chan Yun

    2015-01-01

    Normal-tension glaucoma (NTG) is a heterogenous disease, and there is still controversy about subclassifications of this disorder. On the basis of spectral-domain optical coherence tomography (SD-OCT), we subdivided NTG with hierarchical cluster analysis using optic nerve head (ONH) parameters and retinal nerve fiber layer (RNFL) thicknesses. A total of 200 eyes of 200 NTG patients between March 2011 and June 2012 underwent SD-OCT scans to measure ONH parameters and RNFL thicknesses. We classified NTG into homogenous subgroups based on these variables using a hierarchical cluster analysis, and compared clusters to evaluate diverse NTG characteristics. Three clusters were found after hierarchical cluster analysis. Cluster 1 (62 eyes) had the thickest RNFL and widest rim area, and showed early glaucoma features. Cluster 2 (60 eyes) was characterized by the largest cup/disc ratio and cup volume, and showed advanced glaucomatous damage. Cluster 3 (78 eyes) had small disc areas in SD-OCT and were comprised of patients with significantly younger age, longer axial length, and greater myopia than the other 2 groups. A hierarchical cluster analysis of SD-OCT scans divided NTG patients into 3 groups based upon ONH parameters and RNFL thicknesses. It is anticipated that the small disc area group comprised of younger and more myopic patients may show unique features unlike the other 2 groups.

  20. Imaging of the iridocorneal angle with the RTVue spectral domain optical coherence tomography.

    Science.gov (United States)

    Perera, Shamira A; Ho, Ching Lin; Aung, Tin; Baskaran, Mani; Ho, Henrietta; Tun, Tin A; Lee, Tian Loon; Kumar, Rajesh S

    2012-04-02

    To determine the ability of the RTVue spectral domain optical coherence tomography (SDOCT) to image the anterior chamber angle (ACA). Consecutive subjects, recruited from glaucoma clinics, prospectively underwent ophthalmic evaluation including gonioscopy by an ophthalmologist and anterior chamber imaging with SDOCT, adapted with a corneal lens adapter (cornea anterior module-low magnification [CAM-L]) and anterior segment OCT (ASOCT), both performed by a technician. Two different ophthalmologists, masked to gonioscopy findings, assessed visualization of the scleral spur (SS), Schwalbe's line (SL), and trabecular meshwork (TM) by the two modalities. The ability to detect a closed angle was compared with gonioscopy. The average age (SD) of the 81 subjects enrolled was 64.1 (11.4) years; the majority were Chinese (91.4%) and female (61.7%). SDOCT images revealed the SS in 26.9% (56/324) of quadrants and the SL in 44.1% (143/324) of quadrants; in ASOCT images, the SS could be visualized in 69.1% (224/324) of quadrants (P gonioscopy. When analyzing the horizontal quadrants only, both modalities agreed well with gonioscopy, 0.75 and 0.74, respectively (AC1 statistics). The RTVue SDOCT allowed visualization of SL, TM, and SS. However, these landmarks were not detected in a large percentage of images.

  1. Ability of spectral domain optical coherence tomography peripapillary retinal nerve fiber layer thickness measurements to identify early glaucoma

    Directory of Open Access Journals (Sweden)

    Tarannum Mansoori

    2011-01-01

    Full Text Available Purpose : To evaluate the ability of spectral domain optical coherence tomography (OCT peripapillary retinal nerve fiber layer thickness (RNFLT parameters to distinguish normal eyes from those with early glaucoma in Asian Indian eyes. Design : Observational cross-sectional study. Materials and Methods : One hundred and seventy eight eyes (83 glaucoma patients and 95 age matched healthy subjects of subjects more than 40 years of age were included in the study. All subjects underwent RNFLT measurement with spectral OCT/ scanning laser ophthalmoscope (SLO after dilatation. Sensitivity, specificity and area under the receiving operating characteristic curve (AROC were calculated for various OCT peripapillary RNFL parameters. Results: The mean RNFLT in healthy subjects and patients with early glaucoma were 105.7 ± 5.1 μm and 90.7 ± 7.5 μm, respectively. The largest AROC was found for 12 o′clock- hour (0.98, average (0.96 and superior quadrant RNFLT (0.9. When target specificity was set at ≥ 90% and ≥ 80%, the parameters with highest sensitivity were 12 o′clock -hour (91.6%, average RNFLT (85.3% and 12 o′ clock- hour (96.8 %, average RNFLT (94.7% respectively. Conclusion : Our study showed good ability of spectral OCT/ SLO to differentiate normal eyes from patients with early glaucoma and hence it may serve as an useful adjunct for early diagnosis of glaucoma.

  2. Simultaneous Confocal Scanning Laser Ophthalmoscopy Combined with High-Resolution Spectral-Domain Optical Coherence Tomography: A Review

    Directory of Open Access Journals (Sweden)

    Verônica Castro Lima

    2011-01-01

    Full Text Available We aimed to evaluate technical aspects and the clinical relevance of a simultaneous confocal scanning laser ophthalmoscope and a high-speed, high-resolution, spectral-domain optical coherence tomography (SDOCT device for retinal imaging. The principle of confocal scanning laser imaging provides a high resolution of retinal and choroidal vasculature with low light exposure. Enhanced contrast, details, and image sharpness are generated using confocality. The real-time SDOCT provides a new level of accuracy for assessment of the angiographic and morphological correlation. The combined system allows for simultaneous recordings of topographic and tomographic images with accurate correlation between them. Also it can provide simultaneous multimodal imaging of retinal pathologies, such as fluorescein and indocyanine green angiographies, infrared and blue reflectance (red-free images, fundus autofluorescence images, and OCT scans (Spectralis HRA + OCT; Heidelberg Engineering, Heidelberg, Germany. The combination of various macular diagnostic tools can lead to a better understanding and improved knowledge of macular diseases.

  3. Agreement of Two Different Spectral Domain Optical Coherence Tomography Instruments for Retinal Nerve Fiber Layer Measurements

    Directory of Open Access Journals (Sweden)

    Hooshang Faghihi

    2014-01-01

    Full Text Available Purpose: To determine the agreement between Spectralis and Cirrus spectral domain optical coherence tomography (SD-OCT measurements of peripapillary retinal nerve fiber layer (RNFL thickness. Methods: Suspected or confirmed cases of glaucoma who met the inclusion criteria underwent peripapillary RNFL thickness measurement using both the Spectralis and Cirrus on the same day within a few minutes. Results: Measurements were performed on 103 eyes of 103 patients with mean age of 50.4±17.7 years. Mean RNFL thickness was 89.22±15.87 versus 84.54±13.68 μm using Spectralis and Cirrus, respectively. The difference between measurements and the average of paired measurements with the two devices showed a significant linear relationship. Bland-Altman plots demonstrated that Spectralis thickness values were systematically larger than that of Cirrus. Conclusion: Spectralis OCT generates higher peripapillary RNFL thickness readings as compared to Cirrus OCT; this should be kept in mind when values obtained with different instruments are compared during follow-up.

  4. Automated 3-D method for the correction of axial artifacts in spectral-domain optical coherence tomography images

    Science.gov (United States)

    Antony, Bhavna; Abràmoff, Michael D.; Tang, Li; Ramdas, Wishal D.; Vingerling, Johannes R.; Jansonius, Nomdo M.; Lee, Kyungmoo; Kwon, Young H.; Sonka, Milan; Garvin, Mona K.

    2011-01-01

    The 3-D spectral-domain optical coherence tomography (SD-OCT) images of the retina often do not reflect the true shape of the retina and are distorted differently along the x and y axes. In this paper, we propose a novel technique that uses thin-plate splines in two stages to estimate and correct the distinct axial artifacts in SD-OCT images. The method was quantitatively validated using nine pairs of OCT scans obtained with orthogonal fast-scanning axes, where a segmented surface was compared after both datasets had been corrected. The mean unsigned difference computed between the locations of this artifact-corrected surface after the single-spline and dual-spline correction was 23.36 ± 4.04 μm and 5.94 ± 1.09 μm, respectively, and showed a significant difference (p < 0.001 from two-tailed paired t-test). The method was also validated using depth maps constructed from stereo fundus photographs of the optic nerve head, which were compared to the flattened top surface from the OCT datasets. Significant differences (p < 0.001) were noted between the artifact-corrected datasets and the original datasets, where the mean unsigned differences computed over 30 optic-nerve-head-centered scans (in normalized units) were 0.134 ± 0.035 and 0.302 ± 0.134, respectively. PMID:21833377

  5. Structure-function relationships with spectral-domain optical coherence tomography retinal nerve fiber layer and optic nerve head measurements.

    Science.gov (United States)

    Pollet-Villard, Frédéric; Chiquet, Christophe; Romanet, Jean-Paul; Noel, Christian; Aptel, Florent

    2014-05-02

    To evaluate the regional structure-function relationship between visual field sensitivity and retinal nerve fiber layer (RNFL) thickness and optic nerve head (ONH) measurements using spectral-domain optical coherence tomography (SD-OCT). Prospective cross-sectional study conducted on patients with glaucoma, suspected glaucoma, and healthy subjects. Eyes were tested on Cirrus OCT and standard achromatic perimetry. RNFL thickness of 12 peripapillary 30° sectors, neuroretinal rim thickness extracted from 36 neuroretinal rim scans, and Bruch membrane opening minimum rim width (BMO-MRW)-a recently defined parameter-extracted from 36 neuroretinal rim scans were obtained. Correlations between peripapillary RNFL thickness, neuroretinal rim thickness, all six sectors of BMO-MRW, and visual field sensitivity in the six corresponding areas were evaluated using logarithmic regression analysis. Receiver operating curve areas were calculated for each RNFL, ONH, and macular ganglion cell analysis parameter. We included 142 eyes of 142 subjects. The correlations (r(2)) between RNFL thickness, Cirrus-based neuroretinal rim thickness, BMO-MRW and visual field sensitivity ranged from 0.07 to 0.60, 0.15 to 0.49, and 0.24 to 0.66, respectively. The structure-function correlations were stronger with BMO-MRW than with Cirrus-based neuroretinal rim thickness. The largest areas under the receiver operating curve were seen for rim area (0.926 [95% confidence interval 0.875, 0.977]; P function relationship was significantly stronger with BMO-MRW than other ONH SD-OCT parameters. The best diagnostic capabilities were seen with rim area and average RNFL.

  6. Spectral-domain optical coherence tomography study on dynamic changes of human tears after instillation of artificial tears.

    Science.gov (United States)

    Napoli, Pietro Emanuele; Satta, Giovanni Maria; Coronella, Franco; Fossarello, Maurizio

    2014-07-01

    To analyze in vivo the dynamic changes induced by different artificial tears (ATs) in the precorneal tear film (PCTF) and lower tear meniscus (LTM) by using spectral-domain (SD) anterior segment optical coherence tomography (OCT). We prospectively examined 42 normal human eyes by using SD-OCT imaging. On the day before OCT imaging, all enrolled subjects were evaluated for abnormalities of ocular surface. All tear film images were obtained before and after instillation of three different types of ATs (mucomimetic, lipid-based, and saline) in five serial scans: immediately (within 30 seconds), at the first, fifth, 10th, and 20th minute. Subjects received a drop of 35 μL in one randomly selected eye. All examinations were conducted in the same conditions of temperature, brightness, humidity, and time of day. Changes in the morphological pattern of both LTM and PCTF were associated with the type of artificial tear instilled on the ocular surface. Similarly, the radius of curvature (rc), the height (h), and the depth (d) showed dynamic variations depending on treatment. Although by the 20th minute, both h and d returned to baseline values in all groups, a significant difference in rc (compared with baseline) was detected for mucomimetic ATs (P = 0.04) and lipid ATs (P = 0.02). Spectral-domain OCT imaging has preliminarily proved to be a noninvasive tool to evaluate, in real time, the different changes induced by ATs instillation. An important stride in understanding the clinical response to various tear substitutes can be achieved by this objective and quantitative approach. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.

  7. Fourier phase in Fourier-domain optical coherence tomography

    Science.gov (United States)

    Uttam, Shikhar; Liu, Yang

    2015-01-01

    Phase of an electromagnetic wave propagating through a sample-of-interest is well understood in the context of quantitative phase imaging in transmission-mode microscopy. In the past decade, Fourier-domain optical coherence tomography has been used to extend quantitative phase imaging to the reflection-mode. Unlike transmission-mode electromagnetic phase, however, the origin and characteristics of reflection-mode Fourier phase are poorly understood, especially in samples with a slowly varying refractive index. In this paper, the general theory of Fourier phase from first principles is presented, and it is shown that Fourier phase is a joint estimate of subresolution offset and mean spatial frequency of the coherence-gated sample refractive index. It is also shown that both spectral-domain phase microscopy and depth-resolved spatial-domain low-coherence quantitative phase microscopy are special cases of this general theory. Analytical expressions are provided for both, and simulations are presented to explain and support the theoretical results. These results are further used to show how Fourier phase allows the estimation of an axial mean spatial frequency profile of the sample, along with depth-resolved characterization of localized optical density change and sample heterogeneity. Finally, a Fourier phase-based explanation of Doppler optical coherence tomography is also provided. PMID:26831383

  8. Fourier phase in Fourier-domain optical coherence tomography.

    Science.gov (United States)

    Uttam, Shikhar; Liu, Yang

    2015-12-01

    Phase of an electromagnetic wave propagating through a sample-of-interest is well understood in the context of quantitative phase imaging in transmission-mode microscopy. In the past decade, Fourier-domain optical coherence tomography has been used to extend quantitative phase imaging to the reflection-mode. Unlike transmission-mode electromagnetic phase, however, the origin and characteristics of reflection-mode Fourier phase are poorly understood, especially in samples with a slowly varying refractive index. In this paper, the general theory of Fourier phase from first principles is presented, and it is shown that Fourier phase is a joint estimate of subresolution offset and mean spatial frequency of the coherence-gated sample refractive index. It is also shown that both spectral-domain phase microscopy and depth-resolved spatial-domain low-coherence quantitative phase microscopy are special cases of this general theory. Analytical expressions are provided for both, and simulations are presented to explain and support the theoretical results. These results are further used to show how Fourier phase allows the estimation of an axial mean spatial frequency profile of the sample, along with depth-resolved characterization of localized optical density change and sample heterogeneity. Finally, a Fourier phase-based explanation of Doppler optical coherence tomography is also provided.

  9. En face spectral domain optical coherence tomography analysis of lamellar macular holes.

    Science.gov (United States)

    Clamp, Michael F; Wilkes, Geoff; Leis, Laura S; McDonald, H Richard; Johnson, Robert N; Jumper, J Michael; Fu, Arthur D; Cunningham, Emmett T; Stewart, Paul J; Haug, Sara J; Lujan, Brandon J

    2014-07-01

    To analyze the anatomical characteristics of lamellar macular holes using cross-sectional and en face spectral domain optical coherence tomography. Forty-two lamellar macular holes were retrospectively identified for analysis. The location, cross-sectional length, and area of lamellar holes were measured using B-scans and en face imaging. The presence of photoreceptor inner segment/outer segment disruption and the presence or absence of epiretinal membrane formation were recorded. Forty-two lamellar macular holes were identified. Intraretinal splitting occurred within the outer plexiform layer in 97.6% of eyes. The area of intraretinal splitting in lamellar holes did not correlate with visual acuity. Eyes with inner segment/outer segment disruption had significantly worse mean logMAR visual acuity (0.363 ± 0.169; Snellen = 20/46) than in eyes without inner segment/outer segment disruption (0.203 ± 0.124; Snellen = 20/32) (analysis of variance, P = 0.004). Epiretinal membrane was present in 34 of 42 eyes (81.0%). En face imaging allowed for consistent detection and quantification of intraretinal splitting within the outer plexiform layer in patients with lamellar macular holes, supporting the notion that an area of anatomical weakness exists within Henle's fiber layer, presumably at the synaptic connection of these fibers within the outer plexiform layer. However, the en face area of intraretinal splitting did not correlate with visual acuity, disruption of the inner segment/outer segment junction was associated with significantly worse visual acuity in patients with lamellar macular holes.

  10. Intrasurgical Human Retinal Imaging With Manual Instrument Tracking Using a Microscope-Integrated Spectral-Domain Optical Coherence Tomography Device.

    Science.gov (United States)

    Hahn, Paul; Carrasco-Zevallos, Oscar; Cunefare, David; Migacz, Justin; Farsiu, Sina; Izatt, Joseph A; Toth, Cynthia A

    2015-07-01

    To characterize the first in-human intraoperative imaging using a custom prototype spectral-domain microscope-integrated optical coherence tomography (MIOCT) device during vitreoretinal surgery with instruments in the eye. Under institutional review board approval for a prospective intraoperative study, MIOCT images were obtained at surgical pauses with instruments held static in the vitreous cavity and then concurrently with surgical maneuvers. Postoperatively, MIOCT images obtained at surgical pauses were compared with images obtained with a high-resolution handheld spectral-domain OCT (HHOCT) system with objective endpoints, including acquisition of images acceptable for analysis and identification of predefined macular morphologic or pathologic features. Human MIOCT images were successfully obtained before incision and during pauses in surgical maneuvers. MIOCT imaging confirmed preoperative diagnoses, such as epiretinal membrane, full-thickness macular hole, and vitreomacular traction and demonstrated successful achievement of surgical goals. MIOCT and HHOCT images obtained at surgical pauses in two cohorts of five patients were comparable with greater than or equal to 80% correlation in 80% of patients. Real-time video-imaging concurrent with surgical manipulations enabled, for the first time using this device, visualization of dynamic instrument-retina interaction with targeted OCT tracking. MIOCT is successful for imaging at surgical pauses and for real-time image guidance with implementation of targeted OCT tracking. Even faster acquisition speeds are currently being developed with incorporation of a swept-source MIOCT engine. Further refinements and investigations will be directed toward continued integration for real-time volumetric imaging of surgical maneuvers. Ongoing development of seamless MIOCT systems will likely transform surgical visualization, approaches, and decision-making.

  11. Comparison of automated analysis of Cirrus HD OCT spectral-domain optical coherence tomography with stereo photographs of the optic disc.

    Science.gov (United States)

    Sharma, Ashish; Oakley, Jonathan D; Schiffman, Joyce C; Budenz, Donald L; Anderson, Douglas R

    2011-07-01

    To evaluate a new automated analysis of optic disc images obtained by spectral-domain optical coherence tomography (SD OCT). Areas of the optic disc, cup, and neural rim in SD OCT images were compared with these areas from stereoscopic photographs to represent the current traditional optic nerve evaluation. The repeatability of measurements by each method was determined and compared. Evaluation of diagnostic technology. One hundred nineteen healthy eyes, 23 eyes with glaucoma, and 7 glaucoma suspect eyes. Optic disc and cup margins were traced from stereoscopic photographs by 3 individuals independently. Optic disc margins and rim widths were determined automatically in SD OCT. A subset of photographs was examined and traced a second time, and duplicate SD OCT images also were analyzed. Agreement among photograph readers, between duplicate readings, and between SD OCT and photographs were quantified by the intraclass correlation coefficient (ICC), by the root mean square, and by the standard deviation of the differences. Optic disc areas tended to be slightly larger when judged in photographs than by SD OCT, whereas cup areas were similar. Cup and optic disc areas showed good correlation (0.8) between the average photographic reading and SD OCT, but only fair correlation of rim areas (0.4). The SD OCT was highly reproducible (ICC, 0.96-0.99). Each reader also was consistent with himself on duplicate readings of 21 photographs (ICC, 0.80-0.88 for rim area and 0.95-0.98 for all other measurements), but reproducibility was not as good as SD OCT. Measurements derived from SD OCT did not differ from photographic readings more than the readings of photographs by different readers differed from each other. Designation of the cup and optic disc boundaries by an automated analysis of SD OCT was within the range of variable designations by different readers from color stereoscopic photographs, but use of different landmarks typically made the designation of the optic disc

  12. Time domain optical memories using rare earth ions

    International Nuclear Information System (INIS)

    Sellars, M.J.; Dyke, T.; Pryde, G.J.; Manson, N.B.

    1998-01-01

    Full text: Rare earth doped crystals are the chosen materials for the next generation of optical memories where the process of spectral holeburning can be employed to provide an extra dimension of frequency or time to spatial dimensions and with certain rare earth ions increases of the order of 10 7 in storage capacity can be achieved over conventional optical memories. Time domain techniques are preferred over frequency domain techniques and are now well developed. In these techniques arbitrary pulse sequences are stored in the material and read out at some later time with a single read pulse using a stimulated photon echo process. Long pulse sequences will enable more data to be stored but necessitates the use of materials with long dephasing times (corresponding to narrow spectral lines) and it is this characteristic of rare earth systems that makes them the preferred material for the new time domain optical memories. The storage time can range from hours to days but in a practical device will require refreshing or re-enforcing and this puts special requirements on the stability of the laser used for storing the information. The storage process itself can also be weak and more reliable storage can be achieved by recording the data several times with the same pulse sequence. For this to be successful the laser must be at held at a constant frequency and be stable in phase over the entire duration of the pulse sequence. The procedure of reinforcing the data sequence has been proposed before and attempted without attention to the laser frequency stability. However, if the laser is not stable although some data bits will be reinforced or increased in size others will be decreased or even erased. Indeed the reliability of the memory is degraded by the introducing the rewrite process. For our work we have developed a laser with the excellent stability and able to demonstrate reproducible reinforcement of the data sequence. Thus with the rewrite sequence we are able to

  13. General spectral flow formula for fixed maximal domain

    DEFF Research Database (Denmark)

    Booss-Bavnbek, Bernhelm; Zhu, Chaofeng

    2005-01-01

    and symplectic analysis and give a full (and surprisingly short) proof of our General Spectral Flow Formula for the case of fixed maximal domain. As a side result, we establish local stability of weak inner unique continuation property (UCP) and explain its role for parameter dependent spectral theory....... of the resulting continuous family of (unbounded) self-adjoint Fredholm operators in terms of the Maslov index of two related curves of Lagrangian spaces. One curve is given by the varying domains, the other by the Cauchy data spaces. We provide rigorous definitions of the underlying concepts of spectral theory...

  14. Preface to the special issue on ;Optical Communications Exploiting the Space Domain;

    Science.gov (United States)

    Wang, Jian; Yu, Siyuan; Li, Guifang

    2018-02-01

    The demand for high capacity optical communications will continue to be driven by the exponential growth of global internet traffic. Optical communications are about the exploitation of different physical dimensions of light waves, including complex amplitude, frequency (or wavelength), time, polarization, etc. Conventional techniques such as wavelength-division multiplexing (WDM), time-division multiplexing (TDM) and polarization-division multiplexing (PDM) have almost reached their scalability limits. Space domain is the only known physical dimension left and space-division multiplexing (SDM) seems the only option to further scale the transmission capacity and spectral efficiency of optical communications. In recent years, few-mode fiber (FMF), multi-mode fiber (MMF), multi-core fiber (MCF) and few-mode multi-core fiber (FM-MCF) have been widely explored as promising candidates for fiber-based SDM. The challenges for SDM include efficient (de)multiplexer, amplifiers, and multiple-input multiple-output (MIMO) digital signal processing (DSP) techniques. Photonic integration will also be a key technology to SDM. Meanwhile, free-space and underwater optical communications have also exploited the space domain to increase the transmission capacity and spectral efficiency. The challenges include long-distance transmission limited by propagation loss, divergence, scattering and turbulence. Very recently, helically phased light beams carrying orbital angular momentum (OAM) have also seen potential applications both in free-space, underwater and fiber-based optical communications. Actually, different mode bases such as linearly polarized (LP) modes and OAM modes can be employed for SDM. Additionally, SDM could be used in chip-scale photonic interconnects and data center optical interconnects. Quantum processing exploiting the space domain is of great interest. The information capacity limit and physical layer security in SDM optical communications systems are important

  15. Automated Fovea Detection in Spectral Domain Optical Coherence Tomography Scans of Exudative Macular Disease

    Directory of Open Access Journals (Sweden)

    Jing Wu

    2016-01-01

    Full Text Available In macular spectral domain optical coherence tomography (SD-OCT volumes, detection of the foveal center is required for accurate and reproducible follow-up studies, structure function correlation, and measurement grid positioning. However, disease can cause severe obscuring or deformation of the fovea, thus presenting a major challenge in automated detection. We propose a fully automated fovea detection algorithm to extract the fovea position in SD-OCT volumes of eyes with exudative maculopathy. The fovea is classified into 3 main appearances to both specify the detection algorithm used and reduce computational complexity. Based on foveal type classification, the fovea position is computed based on retinal nerve fiber layer thickness. Mean absolute distance between system and clinical expert annotated fovea positions from a dataset comprised of 240 SD-OCT volumes was 162.3 µm in cystoid macular edema and 262 µm in nAMD. The presented method has cross-vendor functionality, while demonstrating accurate and reliable performance close to typical expert interobserver agreement. The automatically detected fovea positions may be used as landmarks for intra- and cross-patient registration and to create a joint reference frame for extraction of spatiotemporal features in “big data.” Furthermore, reliable analyses of retinal thickness, as well as retinal structure function correlation, may be facilitated.

  16. “En-Face” Spectral-Domain Optical Coherence Tomography Findings in Multiple Evanescent White Dot Syndrome

    Directory of Open Access Journals (Sweden)

    Flore De bats

    2014-01-01

    Full Text Available Purpose. The recent use of “en-face” enhanced-depth imaging spectral-domain optical coherence tomography (EDI SD-OCT helps distinguish the retinal layers involved in the physiopathology of multiple evanescent white dot syndrome (MEWDS. Methods. Four patients presenting with MEWDS underwent a comprehensive ocular examination including C-scan (“en-face” EDI SD-OCT at the initial visit and during follow-up. Results. C-scans combined with the other multimodal imaging enabled the visualization of retinal damage. Acute lesions appeared as diffuse and focal disruptions occurring in the ellipsoid and interdigitation zones. The match between autofluorescence imaging, indocyanine green angiography, and “en-face” OCT helped identify the acute microstructural damages in the outer retina further than the choroid. Follow-up using “en-face” EDI-OCT revealed progressive and complete recovery of the central outer retinal layers. Conclusion. “En-face” EDI SD-OCT identified the site of initial damage in MEWDS as the photoreceptors and the interdigitation layers rather than the choroid. Moreover, “en-face” OCT is helpful in the follow-up of these lesions by being able to show the recovery of the outer retinal layers.

  17. Is Spectral-Domain Optical Coherence Tomography Essential for Flexible Treatment Regimens with Ranibizumab for Neovascular Age-Related Macular Degeneration?

    Directory of Open Access Journals (Sweden)

    Abdullah Ozkaya

    2013-01-01

    Full Text Available Purpose. To evaluate the ability of spectral-domain optical coherence tomography to detect subtle amounts of retinal fluid when the choroidal neovascularization is detected as inactive via time-domain optical coherence tomography and clinical examination in neovascular age-related macular degeneration (nAMD patients. Methods. Forty-nine eyes of 49 patients with nAMD after ranibizumab treatment were included in this cross-sectional, prospective study. All patients were imaged with TD-OCT and SD-OCT at the same visit one month after a ranibizumab injection. The presence of subretinal, intraretinal, and subretinal pigment epithelium fluid (subRPE in SD-OCT was evaluated; also mean central retinal thickness (CRT and the rate of vitreoretinal surface disorders detected via the two devices were evaluated. Results. The mean CRT via TD-OCT and SD-OCT was 218.1±51.3 and 325.7±78.8 microns. Sixteen patients (32.6% showed any kind of retinal fluid via SD-OCT. In detail, 8 patients (16.3% showed subretinal fluid, 10 patients (20.4% showed intraretinal fluid, and 3 patients (6.1% showed SubRPE fluid. The ability of detecting vitreoretinal surface disorders was comparable between the two devices, except vitreomacular traction. Conclusion. SD-OCT is essential for the nAMD patients who are on an as-needed treatment regimen with ranibizumab. Only TD-OCT and clinical examination may cause insufficient treatment in this group of patients.

  18. Automated circumferential construction of first-order aqueous humor outflow pathways using spectral-domain optical coherence tomography.

    Science.gov (United States)

    Huang, Alex S; Belghith, Akram; Dastiridou, Anna; Chopra, Vikas; Zangwill, Linda M; Weinreb, Robert N

    2017-06-01

    The purpose was to create a three-dimensional (3-D) model of circumferential aqueous humor outflow (AHO) in a living human eye with an automated detection algorithm for Schlemm’s canal (SC) and first-order collector channels (CC) applied to spectral-domain optical coherence tomography (SD-OCT). Anterior segment SD-OCT scans from a subject were acquired circumferentially around the limbus. A Bayesian Ridge method was used to approximate the location of the SC on infrared confocal laser scanning ophthalmoscopic images with a cross multiplication tool developed to initiate SC/CC detection automated through a fuzzy hidden Markov Chain approach. Automatic segmentation of SC and initial CC’s was manually confirmed by two masked graders. Outflow pathways detected by the segmentation algorithm were reconstructed into a 3-D representation of AHO. Overall, only time and time with 1.4% false positive detection. 3-D representation of AHO pathways demonstrated variably thicker and thinner SC with some clear CC roots. Circumferential (360 deg), automated, and validated AHO detection of angle structures in the living human eye with reconstruction was possible.

  19. General spectral flow formula for fixed maximal domain

    DEFF Research Database (Denmark)

    Booss-Bavnbek, Bernhelm; Zhu, Chaofeng

    2005-01-01

    of the resulting continuous family of (unbounded) self-adjoint Fredholm operators in terms of the Maslov index of two related curves of Lagrangian spaces. One curve is given by the varying domains, the other by the Cauchy data spaces. We provide rigorous definitions of the underlying concepts of spectral theory......We consider a continuous curve of linear elliptic formally self-adjoint differential operators of first order with smooth coefficients over a compact Riemannian manifold with boundary together with a continuous curve of global elliptic boundary value problems. We express the spectral flow...... and symplectic analysis and give a full (and surprisingly short) proof of our General Spectral Flow Formula for the case of fixed maximal domain. As a side result, we establish local stability of weak inner unique continuation property (UCP) and explain its role for parameter dependent spectral theory....

  20. Diabetic retinal pigment epitheliopathy: fundus autofluorescence and spectral-domain optical coherence tomography findings.

    Science.gov (United States)

    Kang, Eui Chun; Seo, Yuri; Byeon, Suk Ho

    2016-10-01

    To describe the characteristics of an unfamiliar disease entity, diabetic retinal pigment epitheliopathy (DRPE), using fundus autofluorescence (FAF) and spectral-domain optical coherence tomography (SD-OCT). This retrospective study included 17 eyes from 10 proliferative diabetic retinopathy (PDR) patients with granular hypo-autofluorescence and/or variable hyper-autofluorescence on FAF (DRPE group) and 17 eyes from 10 age- and sex-matched PDR patients without abnormal autofluorescence (PDR group). Eyes with diabetic macular edema were excluded. Visual acuity (VA), retinal thickness (RT), and choroidal thickness (CT) were compared between the groups. Eyes in the DRPE group had worse logMAR VA than eyes in the PDR group (0.369 ± 0.266 vs. 0.185 ± 0.119; P = 0.026). The thickness of the retinal pigment epithelium plus the inner segment/outer segment of the photoreceptors was reduced to a greater degree in the DRPE group than the PDR group (P retina showed no differences between the two groups. CT was significantly thicker in the DRPE group than in the PDR group (329.00 ± 33.76 vs. 225.62 ± 37.47 μm; P retina, and thicker choroid in comparison with eyes with PDR. Alterations of autofluorescence on FAF and changes in the outer retinal thickness and CT on SD-OCT can be helpful for differentiating DRPE in patients with PDR.

  1. Comparison of two spectral domain optical coherence tomography devices for angle-closure assessment.

    Science.gov (United States)

    Quek, Desmond T; Narayanaswamy, Arun K; Tun, Tin A; Htoon, Hla M; Baskaran, Mani; Perera, Shamira A; Aung, Tin

    2012-08-03

    To compare two spectral domain optical coherence tomography (SD-OCT) devices for the identification of angle structures and the presence of angle closure. This was a prospective comparative study. Consecutive patients underwent gonioscopy and anterior segment imaging using two SD-OCT devices (iVue and Cirrus). Images were evaluated for the ability to detect angle structures such as Schwalbe's line (SL), trabecular meshwork (TM), Schlemm's canal (SC), and scleral spur (SS), and the presence of angle closure. Angle closure was defined as iris contact with the angle wall anterior to the SS on SD-OCT, and nonvisibility of the posterior TM on gonioscopy. Angle closure in an eye was defined as ≥two quadrants of closed angles. AC1 statistic was used to assess the agreement between devices. Of the 69 subjects studied (46.4% male, 84.1% Chinese, mean age 64.0 ± 10.5 years), 40 subjects (40 eyes, 58.0%) had angle closure on gonioscopy. The most identifiable structure on Cirrus SD-OCT was the SS (82.2%) and SL on iVue SD-OCT (74.5%). Angle closure was indeterminable in 14.5% and 50.7% of Cirrus and iVue scans (P gonioscopy was only fair (AC1 = 0.35 and 0.50 for Cirrus and iVue, respectively). It was more difficult to determine angle closure status with iVue compared with Cirrus SD-OCT. There was fair agreement between both devices with gonioscopy for identifying angle closure.

  2. Single-shot parallel full range complex Fourier-domain optical coherence tomography

    International Nuclear Information System (INIS)

    Huang Bingjie; Bu Peng; Nan Nan; Wang Xiangzhao

    2011-01-01

    We present a method of parallel full range complex Fourier-domain optical coherence tomography (FDOCT) that is capable of acquiring an artifacts-free two-dimensional (2-D) cross-sectional image, i.e. a full range B-scan tomogram, by a single shot of 2-D CCD camera. This method is based on a spatial carrier technique, in which the spatial carrier-frequency is instantaneously introduced into the 2-D spectral interferogram registered in parallel FDOCT by using a grating-generated reference beam. The spatial-carrier-contained 2-D spectral interferogram is processed through Fourier transformation to obtain a complex 2-D spectral interferogram. From the 2-D complex spectral interferomgram, a full range B-scan tomogram is reconstructed. The principle of our method is confirmed by imaging an onion sample.

  3. Prevalence of Split Nerve Fiber Layer Bundles in Healthy People Imaged with Spectral Domain Optical Coherence Tomography

    Directory of Open Access Journals (Sweden)

    Sirel Gür Güngör

    2016-12-01

    Full Text Available Objectives: The presence of retinal nerve fiber layer (RNFL split bundles was recently described in normal eyes scanned using scanning laser polarimetry and by histologic studies. Split bundles may resemble RNFL loss in healthy eyes. The aim of our study was to determine the prevalence of nerve fiber layer split bundles in healthy people. Materials and Methods: We imaged 718 eyes of 359 healthy persons with the spectral domain optical coherence tomography in this cross-sectional study. All eyes had intraocular pressure of 21 mmHg or less, normal appearance of the optic nerve head, and normal visual fields (Humphrey Field Analyzer 24-2 full threshold program. In our study, a bundle was defined as ‘split’ when there is localized defect not resembling a wedge defect in the RNFL deviation map with a symmetrically divided RNFL appearance on the RNFL thickness map. The classification was performed by two independent observers who used an identical set of reference examples to standardize the classification. Results: Inter-observer consensus was reached in all cases. Bilateral superior split bundles were seen in 19 cases (5.29% and unilateral superior split was observed in 15 cases (4.16%. In 325 cases (90.52% there was no split bundle. Conclusion: Split nerve fiber layer bundles, in contrast to single nerve fiber layer bundles, are not common findings in healthy eyes. In eyes with normal optic disc appearance, especially when a superior RNFL defect is observed in RNFL deviation map, the RNLF thickness map and graphs should also be examined for split nerve fiber layer bundles.

  4. Influence of corneal power on circumpapillary retinal nerve fiber layer and optic nerve head measurements by spectral-domain optical coherence tomography

    Directory of Open Access Journals (Sweden)

    Kazunori Hirasawa

    2017-09-01

    Full Text Available AIM: To evaluate the influence of corneal power on circumpapillary retinal nerve fiber layer (cpRNFL and optic nerve head (ONH measurements by spectral-domain optical coherence tomography (SD-OCT. METHODS: Twenty-five eyes of 25 healthy participants (mean age 23.6±3.6y were imaged by SD-OCT using horizontal raster scans. Disposable soft contact lenses of different powers (from −11 to +5 diopters including 0 diopter were worn to induce 2-diopter changes in corneal power. Differences in the cpRNFL and ONH measurements per diopter of change in corneal power were analyzed. RESULTS: As corneal power increased by 1 diopter, total and quadrant cpRNFL thicknesses, except for the nasal sector, decreased by −0.19 to −0.32 μm (P<0.01. Furthermore, the disc, cup, and rim areas decreased by −0.017, −0.007, and −0.015 mm2, respectively (P<0.001; the cup and rim volumes decreased by −0.0013 and −0.006 mm3, respectively (P<0.01; and the vertical and horizontal disc diameters decreased by −0.006 and −0.007 mm, respectively (P<0.001. CONCLUSION: For more precise OCT imaging, the ocular magnification should be corrected by considering both the axial length and corneal power. However, the effect of corneal power changes on cpRNFL thickness and ONH topography are small when compare with those of the axial length.

  5. 2.5 TW, two-cycle IR laser pulses via frequency domain optical parametric amplification.

    Science.gov (United States)

    Gruson, V; Ernotte, G; Lassonde, P; Laramée, A; Bionta, M R; Chaker, M; Di Mauro, L; Corkum, P B; Ibrahim, H; Schmidt, B E; Legaré, F

    2017-10-30

    Broadband optical parametric amplification in the IR region has reached a new milestone through the use of a non-collinear Frequency domain Optical Parametric Amplification system. We report a laser source delivering 11.6 fs pulses with 30 mJ of energy at a central wavelength of 1.8 μm at 10 Hz repetition rate corresponding to a peak power of 2.5 TW. The peak power scaling is accompanied by a pulse shortening of about 20% upon amplification due to the spectral reshaping with higher gain in the spectral wings. This source paves the way for high flux soft X-ray pulses and IR-driven laser wakefield acceleration.

  6. Impact of retinal pigment epithelium pathology on spectral-domain optical coherence tomography-derived macular thickness and volume metrics and their intersession repeatability.

    Science.gov (United States)

    Hanumunthadu, Daren; Wang, Jin Ping; Chen, Wei; Wong, Evan N; Chen, Yi; Morgan, William H; Patel, Praveen J; Chen, Fred K

    2017-04-01

    To determine the impact of retinal pigment epithelium (RPE) pathology on intersession repeatability of retinal thickness and volume metrics derived from Spectralis spectral-domain optical coherence tomography (Heidelberg Engineering, Heidelberg, Germany). Prospective cross-sectional single centre study. A total of 56 eyes of 56 subjects were divided into three groups: (i) normal RPE band (25 eyes); (ii) RPE elevation: macular soft drusen (13 eyes); and (iii) RPE attenuation: geographic atrophy or inherited retinal diseases (18 eyes). Each subject underwent three consecutive follow-up macular raster scans (61 B-scans at 119 μm separation) at 1-month intervals. Retinal thicknesses and volumes for each zone of the macular subfields before and after manual correction of segmentation error. Coefficients of repeatability (CR) were calculated. Mean (range) age was 57 (21-88) years. Mean central subfield thickness (CST) and total macular volume were 264 and 258 μm (P = 0.62), and 8.0 and 7.8 mm 3 (P = 0.31), before and after manual correction. Intersession CR (95% confidence interval) for CST and total macular volume were reduced from 40 (38-41) to 8.3 (8.1-8.5) and 0.62 to 0.16 mm 3 after manual correction of segmentation lines. CR for CST were 7.4, 23.5 and 66.7 μm before and 7.0, 10.9 and 7.6 μm after manual correction in groups i, ii and iii. Segmentation error in eyes with RPE disease has a significant impact on intersession repeatability of Spectralis spectral-domain optical coherence tomography macular thickness and volume metrics. Careful examination of each B-scan and manual adjustment can enhance the utility of quantitative measurement. Improved automated segmentation algorithms are needed. © 2016 Royal Australian and New Zealand College of Ophthalmologists.

  7. Development of ultraviolet- and visible-light one-shot spectral domain optical coherence tomography and in situ measurements of human skin

    Science.gov (United States)

    Hirayama, Heijiro; Nakamura, Sohichiro

    2015-07-01

    We have developed ultraviolet (UV)- and visible-light one-shot spectral domain (SD) optical coherence tomography (OCT) that enables in situ imaging of human skin with an arbitrary wavelength in the UV-visible-light region (370-800 nm). We alleviated the computational burden for each color OCT image by physically dispersing the irradiating light with a color filter. The system consists of SD-OCT with multicylindrical lenses; thus, mechanical scanning of the mirror or stage is unnecessary to obtain an OCT image. Therefore, only a few dozens of milliseconds are necessary to obtain single-image data. We acquired OCT images of one subject's skin in vivo and of a skin excision ex vivo for red (R, 650±20 nm), green (G, 550±20 nm), blue (B, 450±20 nm), and UV (397±5 nm) light. In the visible-light spectrum, R light penetrated the skin and was reflected at a lower depth than G or B light. On the skin excision, we demonstrated that UV light reached the dermal layer. We anticipated that basic knowledge about the spectral properties of human skin in the depth direction could be acquired with this system.

  8. Intraretinal hyperreflective foci on spectral-domain optical coherence tomographic images of patients with retinitis pigmentosa

    Science.gov (United States)

    Kuroda, Masako; Hirami, Yasuhiko; Hata, Masayuki; Mandai, Michiko; Takahashi, Masayo; Kurimoto, Yasuo

    2014-01-01

    Background The purpose of this study was to observe the characteristic findings of spectral-domain optical coherence tomography (SD-OCT) images in the retinas of patients with retinitis pigmentosa and to evaluate their distribution patterns in the early and advanced stages of the disease. Methods A total of 184 patients (368 eyes) with retinitis pigmentosa were observed using SD-OCT. We studied the presence or absence of continuous inner/outer segment (IS/OS) lines, presence of thinning of the retinal pigment epithelium-Bruch’s membrane complex, and distribution patterns of hyperreflective foci in the inner and outer nuclear layers (INL and ONL). Results The IS/OS junction had partially disappeared in 275 eyes, which were at the early stage of retinitis pigmentosa (group X), whereas the junction had totally disappeared in 93, which were at the advanced stage of retinitis pigmentosa (group Y). Hyperreflective foci in the INL were observed in a significantly larger proportion of the eyes in group X than in group Y (90% versus 61%, Pretinitis pigmentosa and hyperreflective foci in the ONL were more frequently observed in the advanced stage. Hyperreflective foci may be indicative of changes in the retinal structure at each stage of retinitis pigmentosa. PMID:24591813

  9. En Face Spectral-Domain Optical Coherence Tomography for the Monitoring of Lesion Area Progression in Stargardt Disease.

    Science.gov (United States)

    Melillo, Paolo; Testa, Francesco; Rossi, Settimio; Di Iorio, Valentina; Orrico, Ada; Auricchio, Alberto; Simonelli, Francesca

    2016-07-01

    We investigated the progression of Stargardt disease (STGD1) over a multiyear follow-up by evaluating the macular lesion area as computed by an automatic algorithm from spectral-domain optical coherence tomography (SD-OCT). We reviewed medical records of STGD1 patients, with a clinical and molecular diagnosis of STGD1 at a single institution, who underwent best-corrected visual acuity (BCVA), fundus photography, SD-OCT, full-field electroretinography, and, when available, fundus autofluorescence (FAF). Regression models were fitted on the selected clinical parameters; in particular, on the macular lesion area computed by SD-OCT, to evaluate the disease progression over a multiyear follow-up. The comparison between SD-OCT and FAF, available for 22 patients, showed that macular lesion area, assessed by SD-OCT, significantly correlated with the area of absent FAF (P disease, showing a significant progression over the follow-up. Our findings suggest that the evaluation of macular lesion area by en face SD-OCT, together with FAF, could drive the choice of the most amenable candidates and the most suitable area to be treated in gene therapy clinical trials.

  10. Application of Novel Software Algorithms to Spectral-Domain Optical Coherence Tomography for Automated Detection of Diabetic Retinopathy.

    Science.gov (United States)

    Adhi, Mehreen; Semy, Salim K; Stein, David W; Potter, Daniel M; Kuklinski, Walter S; Sleeper, Harry A; Duker, Jay S; Waheed, Nadia K

    2016-05-01

    To present novel software algorithms applied to spectral-domain optical coherence tomography (SD-OCT) for automated detection of diabetic retinopathy (DR). Thirty-one diabetic patients (44 eyes) and 18 healthy, nondiabetic controls (20 eyes) who underwent volumetric SD-OCT imaging and fundus photography were retrospectively identified. A retina specialist independently graded DR stage. Trained automated software generated a retinal thickness score signifying macular edema and a cluster score signifying microaneurysms and/or hard exudates for each volumetric SD-OCT. Of 44 diabetic eyes, 38 had DR and six eyes did not have DR. Leave-one-out cross-validation using a linear discriminant at missed detection/false alarm ratio of 3.00 computed software sensitivity and specificity of 92% and 69%, respectively, for DR detection when compared to clinical assessment. Novel software algorithms applied to commercially available SD-OCT can successfully detect DR and may have potential as a viable screening tool for DR in future. [Ophthalmic Surg Lasers Imaging Retina. 2016;47:410-417.]. Copyright 2016, SLACK Incorporated.

  11. EVALUATION OF DIABETIC MACULAR OEDEMA WITH SPECTRAL DOMAIN OPTICAL COHERENCE TOMOGRAPHY AND FUNDUS FLUORESCEIN ANGIOGRAPHY

    Directory of Open Access Journals (Sweden)

    Mallika Venkitasubramanian

    2017-02-01

    Full Text Available BACKGROUND Macular oedema is an important cause of visual morbidity in Diabetic Retinopathy. It can be assessed by both Fundus Fluorescein Angiography (FFA and Optical Coherence Tomography (OCT. The aims of this study were to evaluate the agreement between morphological features on spectral domain Optical Coherence Tomography and Fluorescein Angiographic leakage patterns in Diabetic Macular Oedema, and to study the correlation between the best corrected visual acuity and central foveal thickness measured by Optical Coherence Tomography. MATERIALS AND METHODS This was an observational study. All patients with Diabetic Macular Oedema underwent complete ophthalmic examination and subjected to FFA and OCT. Presence or absence of macular oedema by FFA and OCT was noted and agreement between two modalities of imaging was assessed. Sensitivity of these modalities were also found out using appropriate statistical methods. Best Corrected Visual Acuity (BCVA measured were converted to LogMAR scale and Central foveal thickness measured by OCT. Linear regression analysis was done with central foveal thickness and LogMAR visual acuity. RESULTS A total of 69 eyes of 39 patients were studied. OCT revealed Diabetic Macular Oedema in 97.5% of eyes. Fundus Fluorescein Angiography performed in these patients identified leakage in 95.6% of eyes. Sensitivity and specificity of FFA and OCT were calculated keeping one as the gold standard for sensitivity and specificity of the other. FFA and OCT had almost equal sensitivity (95.46 for OCT and 96.92 for FFA for detection of DME. Specificity of OCT was found to be slightly higher (33.33% compared to FFA (25%. Our results suggest that there is minimal agreement between these two imaging modalities in evaluating DME. Statistically, Kappa value was 0.248. Linear regression analysis showed that central foveal thickness had a significant correlation with visual acuity, with Pearson correlation coefficient r=0.442, p=0

  12. Optic Nerve Head and Retinal Nerve Fiber Layer Differences Between Caribbean Black and African American Patients as Measured by Spectral Domain OCT.

    Science.gov (United States)

    Rao, Rohini; Dhrami-Gavazi, Elona; Al-Aswad, Lama; Ciarleglio, Adam; Cioffi, George A; Blumberg, Dana M

    2015-01-01

    There are well-established differences in optic nerve morphology between patients of African and European descent. Spectral domain optical coherence tomography (OCT) scanning has demonstrated these differences with respect to optic disc area (DA), average cup-disc ratio, cup volume, and nerve fiber layer thickness. However, the term "African descent" describes a heterogenous group with considerable variability. This study evaluates differences in optic nerve and retinal nerve fiber layer (RNFL) parameters as measured by Cirrus HD-OCT between Caribbean black and African American patients. A total of 25 African American subjects and 25 Caribbean black subjects with normal ocular examinations were consecutively recruited to this study. All patients received imaging of the optic nerve and nerve fiber layer with Cirrus HD-OCT. Optic nerve and RNFL parameters were evaluated for statistically significant differences using a t test. A mixed effect model for correlated data was then created to adjust outcome variables for (1) repeated measures and (2) optic nerve size. Two one-sided t tests were then utilized to determine equivalence. After adjustment for DA, RNFL thickness, cup volume, DA, inferior nerve fiber layer, and vertical cup-disc ratio demonstrated statistically significant equivalence between the 2 groups (P value fiber layer quadrant was significantly different between the 2 groups and may merit further investigation. Findings of this study suggest that optic nerve and RNFL morphology is markedly similar between Caribbean blacks and African Americans once adjusted for optic nerve size but cannot be considered equivalent in all measures, particularly in the superior nerve fiber layer.

  13. Spectral-Domain Measurement of Strain Sensitivity of a Two-Mode Birefringent Side-Hole Fiber

    Directory of Open Access Journals (Sweden)

    Waclaw Urbanczyk

    2012-09-01

    Full Text Available The strain sensitivity of a two-mode birefringent side-hole fiber is measured in the spectral domain. In a simple experimental setup comprising a broadband source, a polarizer, a two-mode birefringent side-hole fiber under varied elongations, an analyzer and a compact spectrometer, the spectral interferograms are resolved. These are characterized by the equalization wavelength at which spectral interference fringes have the highest visibility (the largest period due to the zero group optical path difference between the fundamental, the LP01 mode and the higher-order, the LP11 mode. The spectral interferograms with the equalization wavelength are processed to retrieve the phase as a function of the wavelength. From the retrieved phase functions corresponding to different elongations of a two-mode birefringent side-hole fiber under test, the spectral strain sensitivity is obtained. Using this approach, the intermodal spectral strain sensitivity was measured for both x and y polarizations. Moreover, the spectral polarimetric sensitivity to strain was measured for the fundamental mode when a birefringent delay line was used in tandem with the fiber. Its spectral dependence was also compared with that obtained from a shift of the spectral interferograms not including the equalization wavelength, and good agreement was confirmed.

  14. CLASSIFICATION AND QUANTITATIVE ANALYSIS OF GEOGRAPHIC ATROPHY JUNCTIONAL ZONE USING SPECTRAL DOMAIN OPTICAL COHERENCE TOMOGRAPHY.

    Science.gov (United States)

    Qu, Jinfeng; Velaga, Swetha Bindu; Hariri, Amir H; Nittala, Muneeswar Gupta; Sadda, Srinivas

    2017-08-22

    The junctional zone at the border of areas of geographic atrophy (GA) in eyes with nonneovascular age-related macular degeneration is an important target region for future therapeutic strategies. The goal of this study was to perform a detailed classification and quantitative characterization of the junctional zone using spectral domain optical coherence tomography. Spectral domain optical coherence tomography volume cube scans (Spectralis OCT, 1024 × 37, Automatic Real Time > 9) were obtained from 15 eyes of 11 patients with GA because of nonneovascular age-related macular degeneration. Volume optical coherence tomography data were imported into previously described validated grading software (3D-OCTOR), and manual segmentation of the retinal pigment epithelium (RPE) and photoreceptor layers was performed on all B-scans (total of 555). Retinal pigment epithelium and photoreceptor defect maps were produced for each case. The borders of the photoreceptor defect area and RPE defect area were delineated individually on separate annotation layers. The two outlines were then superimposed to compare the areas of overlap and nonoverlap. The perimeter of the RPE defect area was calculated by the software in pixels. The superimposed outline of the photoreceptor defect area and the RPE defect area was scrutinized to classify the overlap configuration of the junctional zone into one of three categories: Type 0, exact correspondence between the edge of the RPE defect and photoreceptor defect; Type 1, loss of photoreceptors outside and beyond the edge of the RPE defect; Type 2, preservation of photoreceptors beyond the edge of the RPE defect. The relative proportion of the various border configurations was expressed as a percentage of the perimeter of the RPE defect. Each configuration was then classified into four subgroups according to irregularity of the RPE band and the presence of debris. Fifteen eyes of 11 patients (mean age: 79.3 ± 4.3 years; range: 79-94 years) were

  15. Differences between time domain and Fourier domain optical coherence tomography in imaging tissues.

    Science.gov (United States)

    Gao, W; Wu, X

    2017-11-01

    It has been numerously demonstrated that both time domain and Fourier domain optical coherence tomography (OCT) can generate high-resolution depth-resolved images of living tissues and cells. In this work, we compare the common points and differences between two methods when the continuous and random properties of live tissue are taken into account. It is found that when relationships that exist between the scattered light and tissue structures are taken into account, spectral interference measurements in Fourier domain OCT (FDOCT) is more advantageous than interference fringe envelope measurements in time domain OCT (TDOCT) in the cases where continuous property of tissue is taken into account. It is also demonstrated that when random property of tissue is taken into account FDOCT measures the Fourier transform of the spatial correlation function of the refractive index and speckle phenomena will limit the effective limiting imaging resolution in both TDOCT and FDOCT. Finally, the effective limiting resolution of both TDOCT and FDOCT are given which can be used to estimate the effective limiting resolution in various practical applications. © 2017 The Authors Journal of Microscopy © 2017 Royal Microscopical Society.

  16. Macular laser photocoagulation guided by spectral-domain optical coherence tomography versus fluorescein angiography for diabetic macular edema

    Directory of Open Access Journals (Sweden)

    Gallego-Pinazo R

    2011-05-01

    Full Text Available Roberto Gallego-Pinazo1,2, Ana Marina Suelves-Cogollos1, Rosa Dolz-Marco1, J Fernando Arevalo3, Salvador García-Delpech1, J Luis Mullor4, Manuel Díaz-Llopis1,2,51Department of Ophthalmology, Hospital Universitario La Fe, Valencia, Spain; 2Centro de Investigación Biomédica en Red de Enfermedades Raras, Valencia, Spain; 3Retina and Vitreous Service, Clinical Ophthalmology Center, Caracas, Venezuela; 4Unit of Experimental Ophthalmology, Hospital Universitario La Fe, Valencia, Spain; 5University of Valencia, Faculty of Medicine, Valencia, SpainBackground: The aim of this study was to compare the efficacy of spectral-domain optical coherence tomography (SD-OCT and fluorescein angiography (FA in the guidance of macular laser photocoagulation for diabetic macular edema.Methods: This was a prospective interventional clinical comparative pilot study. Forty eyes from 24 consecutive patients with diabetic macular edema were allocated to receive laser photocoagulation guided by SD-OCT or FA. Best-corrected visual acuity (BCVA, central macular thickness, and retinal volume were assessed at baseline and two months after treatment.Results: Subjects treated using FA-guided laser improved BCVA from the logarithm of the minimum angle of resolution (logMAR 0.52 ± 0.2 to 0.37 ± 0.2 (P < 0.001, and decreased mean central macular thickness from 397.25 ± 139.1 to 333.50 ± 105.7 µm (P < 0.001 and retinal volume from 12.61 ± 1.6 to 10.94 ± 1.4 mm3 (P < 0.001. Subjects treated using SD-OCT guided laser had improved BCVA from 0.48 ± 0.2 to 0.33 ± 0.2 logMAR (P < 0.001, and decreased mean central macular thickness from 425.90 ± 149.6 to 353.4 ± 140 µm (P < 0.001 and retinal volume from 12.38 ± 2.1 to 11.53 ± 1.1 mm3 (P < 0.001. No significant differences between the groups were found in two-month BCVA (P = 0.505, two-month central macular thickness (P = 0.660, or two-month retinal volume (P = 0.582.Conclusion: The short-term results of this pilot study

  17. Changes in Tear Volume after 3% Diquafosol Treatment in Patients with Dry Eye Syndrome: An Anterior Segment Spectral-domain Optical Coherence Tomography Study.

    Science.gov (United States)

    Lee, Kwan Bok; Koh, Kyung Min; Kwon, Young A; Song, Sang Wroul; Kim, Byoung Yeop; Chung, Jae Lim

    2017-08-01

    To evaluate changes in the tear meniscus area and tear meniscus height over time in patients with dry eye syndrome, using anterior segment spectral-domain optical coherence tomography after the instillation of 3% diquafosol ophthalmic solution. Sixty eyes from 30 patients with mild to moderate dry eye syndrome were included. Tear meniscus images acquired by anterior segment spectral-domain optical coherence tomography were analyzed using National Institutes of Health's image-analysis software (ImageJ 1.44p). Tear meniscus area and tear meniscus height were measured at baseline, 5 minutes, 10 minutes, and 30 minutes after instillation of a drop of diquafosol in one eye and normal saline in the other eye. Changes in ocular surface disease index score, tear film break-up time, corneal staining score by Oxford schema, and meibomian expressibility were also evaluated at baseline, and after 1 week and 1 month of a diquafosol daily regimen. Sixty eyes from 30 subjects (mean age, 29.3 years; 8 men and 22 women) were included. In eyes receiving diquafosol, tear volume was increased at 5 and 10 minutes compared with baseline. It was also higher than saline instilled eyes at 5, 10, and 30 minutes. Changes in tear volume with respect to baseline were not statistically different after the use of diquafosol for 1 month. Ocular surface disease index score, tear film break-up time, and Oxford cornea stain score were significantly improved after 1 week and 1 month of daily diquafosol instillation, but meibomian expressibility did not change. Topical diquafosol ophthalmic solution effectively increased tear volume for up to 30 minutes, compared to normal saline in patients with dry eye syndrome. © 2017 The Korean Ophthalmological Society

  18. Augmenting the spectral efficiency of enhanced PAM-DMT-based optical wireless communications.

    Science.gov (United States)

    Islim, Mohamed Sufyan; Haas, Harald

    2016-05-30

    The energy efficiency of pulse-amplitude-modulated discrete multitone modulation (PAM-DMT) decreases as the modulation order of M-PAM modulation increases. Enhanced PAM-DMT (ePAM-DMT) was proposed as a solution to the reduced energy efficiency of PAM-DMT. This was achieved by allowing multiple streams of PAM-DMT to be superimposed and successively demodulated at the receiver side. In order to maintain a distortion-free unipolar ePAM-DMT system, the multiple time-domain PAM-DMT streams are required to be aligned. However, aligning the antisymmetry in ePAM-DMT is complex and results in efficiency losses. In this paper, a novel simplified method to apply the superposition modulation on M-PAM modulated discrete multitone (DMT) is introduced. Contrary to ePAM-DMT, the signal generation of the proposed system, termed augmented spectral efficiency discrete multitone (ASE-DMT), occurs in the frequency domain. This results in an improved spectral and energy efficiency. The analytical bit error rate (BER) performance bound of the proposed system is derived and compared with Monte-Carlo simulations. The system performance is shown to offer significant electrical and optical energy savings compared with ePAM-DMT and DC-biased optical orthogonal frequency division multiplexing (DCO-OFDM).

  19. 3D refraction correction and extraction of clinical parameters from spectral domain optical coherence tomography of the cornea.

    Science.gov (United States)

    Zhao, Mingtao; Kuo, Anthony N; Izatt, Joseph A

    2010-04-26

    Capable of three-dimensional imaging of the cornea with micrometer-scale resolution, spectral domain-optical coherence tomography (SDOCT) offers potential advantages over Placido ring and Scheimpflug photography based systems for accurate extraction of quantitative keratometric parameters. In this work, an SDOCT scanning protocol and motion correction algorithm were implemented to minimize the effects of patient motion during data acquisition. Procedures are described for correction of image data artifacts resulting from 3D refraction of SDOCT light in the cornea and from non-idealities of the scanning system geometry performed as a pre-requisite for accurate parameter extraction. Zernike polynomial 3D reconstruction and a recursive half searching algorithm (RHSA) were implemented to extract clinical keratometric parameters including anterior and posterior radii of curvature, central cornea optical power, central corneal thickness, and thickness maps of the cornea. Accuracy and repeatability of the extracted parameters obtained using a commercial 859nm SDOCT retinal imaging system with a corneal adapter were assessed using a rigid gas permeable (RGP) contact lens as a phantom target. Extraction of these parameters was performed in vivo in 3 patients and compared to commercial Placido topography and Scheimpflug photography systems. The repeatability of SDOCT central corneal power measured in vivo was 0.18 Diopters, and the difference observed between the systems averaged 0.1 Diopters between SDOCT and Scheimpflug photography, and 0.6 Diopters between SDOCT and Placido topography.

  20. Spectral element method for elastic and acoustic waves in frequency domain

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Linlin; Zhou, Yuanguo; Wang, Jia-Min; Zhuang, Mingwei [Institute of Electromagnetics and Acoustics, and Department of Electronic Science, Xiamen, 361005 (China); Liu, Na, E-mail: liuna@xmu.edu.cn [Institute of Electromagnetics and Acoustics, and Department of Electronic Science, Xiamen, 361005 (China); Liu, Qing Huo, E-mail: qhliu@duke.edu [Department of Electrical and Computer Engineering, Duke University, Durham, NC, 27708 (United States)

    2016-12-15

    Numerical techniques in time domain are widespread in seismic and acoustic modeling. In some applications, however, frequency-domain techniques can be advantageous over the time-domain approach when narrow band results are desired, especially if multiple sources can be handled more conveniently in the frequency domain. Moreover, the medium attenuation effects can be more accurately and conveniently modeled in the frequency domain. In this paper, we present a spectral-element method (SEM) in frequency domain to simulate elastic and acoustic waves in anisotropic, heterogeneous, and lossy media. The SEM is based upon the finite-element framework and has exponential convergence because of the use of GLL basis functions. The anisotropic perfectly matched layer is employed to truncate the boundary for unbounded problems. Compared with the conventional finite-element method, the number of unknowns in the SEM is significantly reduced, and higher order accuracy is obtained due to its spectral accuracy. To account for the acoustic-solid interaction, the domain decomposition method (DDM) based upon the discontinuous Galerkin spectral-element method is proposed. Numerical experiments show the proposed method can be an efficient alternative for accurate calculation of elastic and acoustic waves in frequency domain.

  1. Assessment of Corneal and Tear Film Parameters in Rheumatoid Arthritis Patients Using Anterior Segment Spectral Domain Optical Coherence Tomography.

    Science.gov (United States)

    El-Fayoumi, Dina; Youssef, Maha Mohamed; Khafagy, Mohamed Mahmoud; Badr El Dine, Nashwa; Gaber, Wafaa

    2018-01-01

    To study the corneal changes in rheumatoid arthritis (RA) patients in vivo, using spectral domain anterior segment optical coherence tomography (AS-OCT). A case-control study was done on 43 RA patients and 40 controls. The disease activity score (DAS28-ESR) was calculated and all participants had lower tear meniscus, corneal thickness, and epithelial thickness evaluation using AS-OCT. The lower tear meniscus height (LTMH) and the lower tear meniscus area (LTMA) were significantly lower in the RA patients than in controls (p < 0.001). RA patients also had a significantly thinner central corneal thickness (p = 0.02) and their epithelium was found to be thinner in the superotemporal peripheral sector. The LTMH and LTMA are significantly reduced in RA patients, despite the absence of clinical diagnosis of dry eye. RA patients have thinner corneal thickness and epithelial thickness than controls, which did not correlate with either disease duration or activity.

  2. Absolute measurement of subnanometer scale vibration of cochlear partition of an excised guinea pig cochlea using spectral-domain phase-sensitive optical coherence tomography

    Science.gov (United States)

    Subhash, Hrebesh M.; Choudhury, Niloy; Jacques, Steven L.; Wang, Ruikang K.; Chen, Fangyi; Zha, Dingjun; Nuttall, Alfred L.

    2012-01-01

    Direct measurement of absolute vibration parameters from different locations within the mammalian organ of Corti is crucial for understanding the hearing mechanics such as how sound propagates through the cochlea and how sound stimulates the vibration of various structures of the cochlea, namely, basilar membrane (BM), recticular lamina, outer hair cells and tectorial membrane (TM). In this study we demonstrate the feasibility a modified phase-sensitive spectral domain optical coherence tomography system to provide subnanometer scale vibration information from multiple angles within the imaging beam. The system has the potential to provide depth resolved absolute vibration measurement of tissue microstructures from each of the delay-encoded vibration images with a noise floor of ~0.3nm at 200Hz.

  3. Automated circumferential construction of first-order aqueous humor outflow pathways using spectral-domain optical coherence tomography

    Science.gov (United States)

    Huang, Alex S.; Belghith, Akram; Dastiridou, Anna; Chopra, Vikas; Zangwill, Linda M.; Weinreb, Robert N.

    2017-06-01

    The purpose was to create a three-dimensional (3-D) model of circumferential aqueous humor outflow (AHO) in a living human eye with an automated detection algorithm for Schlemm's canal (SC) and first-order collector channels (CC) applied to spectral-domain optical coherence tomography (SD-OCT). Anterior segment SD-OCT scans from a subject were acquired circumferentially around the limbus. A Bayesian Ridge method was used to approximate the location of the SC on infrared confocal laser scanning ophthalmoscopic images with a cross multiplication tool developed to initiate SC/CC detection automated through a fuzzy hidden Markov Chain approach. Automatic segmentation of SC and initial CC's was manually confirmed by two masked graders. Outflow pathways detected by the segmentation algorithm were reconstructed into a 3-D representation of AHO. Overall, only <1% of images (5114 total B-scans) were ungradable. Automatic segmentation algorithm performed well with SC detection 98.3% of the time and <0.1% false positive detection compared to expert grader consensus. CC was detected 84.2% of the time with 1.4% false positive detection. 3-D representation of AHO pathways demonstrated variably thicker and thinner SC with some clear CC roots. Circumferential (360 deg), automated, and validated AHO detection of angle structures in the living human eye with reconstruction was possible.

  4. Spectral element method for wave propagation on irregular domains

    Indian Academy of Sciences (India)

    A spectral element approximation of acoustic propagation problems combined with a new mapping method on irregular domains is proposed. Following this method, the Gauss–Lobatto–Chebyshev nodes in the standard space are applied to the spectral element method (SEM). The nodes in the physical space are ...

  5. En Face Spectral-Domain Optical Coherence Tomography for the Monitoring of Lesion Area Progression in Stargardt Disease

    Science.gov (United States)

    Melillo, Paolo; Testa, Francesco; Rossi, Settimio; Di Iorio, Valentina; Orrico, Ada; Auricchio, Alberto; Simonelli, Francesca

    2016-01-01

    Purpose We investigated the progression of Stargardt disease (STGD1) over a multiyear follow-up by evaluating the macular lesion area as computed by an automatic algorithm from spectral-domain optical coherence tomography (SD-OCT). Methods We reviewed medical records of STGD1 patients, with a clinical and molecular diagnosis of STGD1 at a single institution, who underwent best-corrected visual acuity (BCVA), fundus photography, SD-OCT, full-field electroretinography, and, when available, fundus autofluorescence (FAF). Regression models were fitted on the selected clinical parameters; in particular, on the macular lesion area computed by SD-OCT, to evaluate the disease progression over a multiyear follow-up. Results The comparison between SD-OCT and FAF, available for 22 patients, showed that macular lesion area, assessed by SD-OCT, significantly correlated with the area of absent FAF (P disease, showing a significant progression over the follow-up. Our findings suggest that the evaluation of macular lesion area by en face SD-OCT, together with FAF, could drive the choice of the most amenable candidates and the most suitable area to be treated in gene therapy clinical trials. PMID:27409479

  6. Spectral domain optical coherence tomography as an effective screening test for hydroxychloroquine retinopathy (the "flying saucer" sign).

    Science.gov (United States)

    Chen, Eric; Brown, David M; Benz, Matthew S; Fish, Richard H; Wong, Tien P; Kim, Rosa Y; Major, James C

    2010-10-21

    While the long-term incidence of hydroxychloroquine (HCQ) retinopathy is low, there remains no definitive clinical screening test to recognize HCQ toxicity before ophthalmoscopic fundus changes or visual symptoms. Patients receiving HCQ were evaluated with spectral domain optical coherence tomography (SD OCT) to assess the feasibility of identifying HCQ retinopathy at an early stage. Twenty-five patients referred for the evaluation of hydroxychloroquine toxicity underwent a comprehensive ocular examination, Humphrey visual field (HVF) perimetry, time domain OCT, and SD OCT. Some patients with screening abnormalities also underwent further diagnostic testing at the discretion of the treating providers. Five patients were found to have SD OCT findings corresponding to HCQ toxicity and retinal damage as seen by clinical exam and/or HVF perimetry. Two patients with advanced toxicity were found to have significant outer retina disruption in the macula on SD OCT. Three patients with early HCQ toxicity and HVF 10-2 perifoveal defects were found to have loss of the perifoveal photoreceptor inner segment/outer segment (IS/OS) junction with intact outer retina directly under the fovea, creating the "flying saucer" sign. While two of these three patients had early ophthalmoscopic fundus changes, one had none. Outer retinal abnormalities including perifoveal photoreceptor IS/OS junction disruption can be identified by SD OCT in early HCQ toxicity, sometimes even before ophthalmoscopic fundus changes are apparent. SD OCT may have a potential complementary role in screening for HCQ retinopathy due to its quick acquisition and because it is more objective than automated perimetry.

  7. Coulomb field strength measurement by electro-optic spectral decoding system at the CALIFES beam line

    CERN Document Server

    Pan, R; Lefevre, T; Gillepsie, WA; CERN. Geneva. ATS Department

    2016-01-01

    Electro-optic (EO) techniques are increasingly used for longitudinal bunch profile measurements. A bunch profile monitor, based on electro-optic spectral decoding(EOSD), has been developed and demonstrated on the CALIFES beam line at CERN. The EO response is analysed using a frequency domain description, and two methods for extraction of absolute Coulomb field strengths from the electron bunch are demonstrated. Measurements at field strengths up to 1.3 MV/m agree with the expectation based on independent charge measurements.

  8. Spectral element method for wave propagation on irregular domains

    Indian Academy of Sciences (India)

    Yan Hui Geng

    2018-03-14

    Mar 14, 2018 ... Abstract. A spectral element approximation of acoustic propagation problems combined with a new mapping method on irregular domains is proposed. Following this method, the Gauss–Lobatto–Chebyshev nodes in the standard space are applied to the spectral element method (SEM). The nodes in the ...

  9. Three-dimensional mapping of peripapillary retinal layers using a spectral domain optical coherence tomography

    Directory of Open Access Journals (Sweden)

    Hashmani N

    2017-12-01

    Full Text Available Nauman Hashmani, Sharif Hashmani Department of Ophthalmology, Hashmanis Hospital, Karachi, Pakistan Purpose: To map and view the effects of age, gender, and axial length on seven individual retinal layers around the optic nerve head (ONH.Methods: We scanned 242 healthy patients using the Spectralis spectral domain optical coherence tomography in an outpatient setting. The layers were observed on the Early Treatment Diabetic Retinopathy Study sectors using the standard Spectralis Family Acquisition Module 6.0.11.0. The center was the ONH, the inner circle (IC was 1–3 mm away, and the outer circle (OC was 3–6 mm away. The seven layers were retinal nerve fiber layer (RNFL, ganglion cell layer (GCL, inner plexiform layer (IPL, inner nuclear layer (INL, outer plexiform layer (OPL, outer nuclear layer (ONL, and retinal pigment epithelium (RPE. Additionally, we calculated the mean thickness of two combined layers: inner retinal layer (IRL and photoreceptor layer (PL. Finally, we measured the mean of the total retinal thickness (TRT.Results: The TRT was highest at the inferior end in the IC and at the nasal end in the OC. The RPE (p<0.001 and PL (p<0.001 were thicker in males; however, the IRL (p=0.015 was thicker in females. We found that the RNFL (p<0.001, r=0.139, GCL (p<0.001, r=0.116, IPL (p=0.016, r=0.059, INL (p<0.001, r=0.104, OPL (p=0.009, r=0.064, ONL (p<0.001, r=0.157, RPE (p=0.001, r=0.079, IRL (p<0.001, r=0.190, PL (p=0.030, r=0.053, and TRT (p<0.001, r=0.191 correlated negatively with age. The axial length significantly and negatively correlated at the GCL (p=0.003, r=0.093, IPL (p=0.020, r=0.072, INL (p=0.018, r=0.073, ONL (p<0.001, r=0.110, IRL (p=0.003, r=0.092, and TRT (p=0.003, r=0.094. We found poor reproducibility in the IC; however, this was excellent in the OC.Conclusion: We found significant differences in layers according to age, gender, and axial length. Additionally, reproducibility can be improved by altering the

  10. Assessment of ischemia in acute central retinal vein occlusion from inner retinal reflectivity on spectral domain optical coherence tomography

    Directory of Open Access Journals (Sweden)

    Browning DJ

    2016-12-01

    Full Text Available David J Browning, Omar S Punjabi, Chong Lee Department of Ophthalmology, Charlotte Eye, Ear, Nose and Throat Associates, P.A., Charlotte, NC, USA Purpose: To determine the relationship between different spectral domain optical coherence tomography (SD-OCT signs of retinal ischemia in acute central retinal vein occlusion (CRVO and whether they predict anterior segment neovascularization (ASNV.Design: Retrospective, observational study.Subjects: Thirty-nine consecutive patients with acute CRVO and 12 months of follow-up.Methods: We graded baseline SD-OCTs for increased reflectivity of the inner retina, loss of definition of inner retinal layers, presence of a prominent middle-limiting membrane (p-MLM sign, and presence of paracentral acute middle maculopathy (PAMM. Graders were masked with respect to all clinical information.Results: The intraclass correlation coefficients (ICCs of grading–regrading by graders 1 and 2 were 0.8104, 95% confidence interval (CI (0.6686, 0.8956, and 0.7986, 95% CI (0.6475, 0.8892, respectively. The intragrader coefficients of repeatability (COR for graders 1 and 2 were 0.94 and 0.92, respectively. The ICC of graders 1 compared with 2 was 0.8039, 95% CI (0.6544, 0.8916. The intergrader COR was 0.80. SD-OCT grades of baseline ischemia were not associated with baseline visual acuity (VA, central subfield mean thickness (CSMT, or relative afferent pupillary defect; 12-month VA, CSMT, change in VA, change in CSMT, number of antivascular endothelial growth factor injections or corticosteroid injections, or proportion of eyes developing ASNV. SD-OCT grades of ischemia did not correlate with the proportion of eyes having the p-MLM sign or PAMM. PAMM and p-MLM are milder signs of ischemia than increased reflectivity of the inner retinal layers. Eyes with PAMM can evolve, losing PAMM and gaining the p-MLM sign.Conclusion: Grading of ischemia from SD-OCT in acute CRVO was repeatable within graders and reproducible across

  11. Estimating the Spectral Width of a Narrowband Optical Signal

    DEFF Research Database (Denmark)

    Lading, Lars; Skov Jensen, A.

    1980-01-01

    Methods for estimating the spectral width of a narrowband optical signal are investigated. Spectral analysis and Fourier spectroscopy are compared. Optimum and close-to-optimum estimators are developed under the constraint of having only one photodetector.......Methods for estimating the spectral width of a narrowband optical signal are investigated. Spectral analysis and Fourier spectroscopy are compared. Optimum and close-to-optimum estimators are developed under the constraint of having only one photodetector....

  12. Spectrally selective molecular doped solids: spectroscopy, photophysics and their application to ultrafast optical pulse processing

    International Nuclear Information System (INIS)

    Galaup, Jean-Pierre

    2005-01-01

    The persistent spectral hole-burning (PSHB) phenomenon observed in molecular doped polymers cooled down to liquid helium temperatures allows the engraving of spectral structures in the inhomogeneous absorption profile of the material. This phenomenon known since 1974 has became a fruitful field for the study of the intimacy of complex molecular systems in the solid state, revealing high-resolution spectroscopy, photophysics, photochemistry and dynamics of molecular doped amorphous media, organic as well as inorganic. A PSHB molecular doped solid can be programmed in spectral domain and therefore, it can be converted in an optical processor capable to achieve user-defined optical functions. Some aspects of this field are illustrated in the present paper. An application is presented where a naphthalocyanine doped polymer film is used in a demonstrative experiment to prove that temporal aberration free re-compression of ultra-short light pulses is feasible. Perspectives for the coherent control of light fields or photochemical processes are also evoked

  13. Advances in spectral inversion of time-domain induced polarization

    DEFF Research Database (Denmark)

    Fiandaca, Gianluca; Auken, Esben; Christiansen, Anders Vest

    The extraction of spectral information in the inversion process of time-domain (TD) induced polarization (IP) data is changing the use of the TDIP method. Data interpretation is evolving from a qualitative description of the subsurface, able only to discriminate the presence of contrasts in charg......The extraction of spectral information in the inversion process of time-domain (TD) induced polarization (IP) data is changing the use of the TDIP method. Data interpretation is evolving from a qualitative description of the subsurface, able only to discriminate the presence of contrasts...... in chargeability parameters, towards a quantitative analysis of the investigated media, which allows for detailed soil- and rock-type characterization. In this work a review of the recent advances in spectral inversion of TDIP data is presented, in terms of: supported IP parameterizations; modelling of transmitter...

  14. Reflectivity and thickness analysis of epiretinal membranes using spectral-domain optical coherence tomography

    Directory of Open Access Journals (Sweden)

    Ajay E. Kuriyan

    2016-01-01

    Full Text Available AIM: To compare thickness and reflectivity spectral domain optical coherence tomography (SD-OCT findings in patients with idiopathic epiretinal membranes (ERMs, before and after ERM peeling surgery, with normal controls. METHODS: A retrospective study analyzed SD-OCTs of eyes with ERMs undergoing ERM peeling surgery by one surgeon from 2008 to 2010 and normal control eyes. SD-OCTs were analyzed using a customized algorithm to measure reflectivity and thickness. The relationship between the SD-OCT findings and best corrected visual acuity (BCVA outcomes was also studied. RESULTS: Thirty-four ERM eyes and 12 normal eyes were identified. Preoperative eyes had high reflectivity and thickness of the group of layers from the internal limiting membrane (ILM to the retinal pigment epithelium (RPE and the group of layers from the ILM to the external limiting membrane (ELM. The values of reflectivity of these two groups of layers decreased postoperatively, but were still higher than normal eyes. In contrast, preoperative eyes had lower reflectivity of two 10×15 pixel regions of interest (ROIs incorporating: 1 ELM + outer nuclear layer (ONL and 2 photoreceptor layer (PRL + RPE, compared to controls. The values of reflectivity of these ROIs increased postoperatively, but were still lower than normal controls. A larger improvement in BCVA postoperatively was correlated with a greater degree of abnormal preoperative reflectivity and thickness findings. CONCLUSION: Quantitative differences in reflectivity and thickness between preoperative, postoperative, and normal SD-OCTs allow assessment of changes in the retina secondary to ERM. Our study identified hyperreflective inner retina changes and hyporeflective outer retina changes in patients with ERMs. SD-OCT quantitative measures of reflectivity and/or thickness of specific groups of retinal layers and/or ROIs correlate with improvement in BCVA.

  15. Optical characterization of agricultural pest insects: a methodological study in the spectral and time domains

    Science.gov (United States)

    Li, Y. Y.; Zhang, H.; Duan, Z.; Lian, M.; Zhao, G. Y.; Sun, X. H.; Hu, J. D.; Gao, L. N.; Feng, H. Q.; Svanberg, S.

    2016-08-01

    Identification of agricultural pest insects is an important aspect in insect research and agricultural monitoring. We have performed a methodological study of how spectroscopic techniques and wing-beat frequency analysis might provide relevant information. An optical system based on the combination of close-range remote sensing and reflectance spectroscopy was developed to study the optical characteristics of different flying insects, collected in Southern China. The results demonstrate that the combination of wing-beat frequency assessment and reflectance spectral analysis has the potential to successfully differentiate between insect species. Further, studies of spectroscopic characteristics of fixed specimen of insects, also from Central China, showed the possibility of refined agricultural pest identification. Here, in addition to reflectance recordings also laser-induced fluorescence spectra were investigated for all the species of insects under study and found to provide complementary information to optically distinguish insects. In order to prove the practicality of the techniques explored, clearly fieldwork aiming at elucidating the variability of parameters, even within species, must be performed.

  16. Optical-domain Compensation for Coupling between Optical Fiber Conjugate Vortex Modes

    DEFF Research Database (Denmark)

    Lyubopytov, Vladimir S.; Tatarczak, Anna; Lu, Xiaofeng

    2016-01-01

    We demonstrate for the first time optical-domain compensation for coupling between conjugate vortex modes in optical fibers. We introduce a novel method for reconstructing the complex propagation matrix of the optical fiber with straightforward implementation.......We demonstrate for the first time optical-domain compensation for coupling between conjugate vortex modes in optical fibers. We introduce a novel method for reconstructing the complex propagation matrix of the optical fiber with straightforward implementation....

  17. On the detection and monitoring of reduced water content in plants using spectral responses in the visible domain

    Science.gov (United States)

    Baranoski, Gladimir V. G.; Van Leeuwen, Spencer; Chen, Tenn F.

    2016-05-01

    The water status of cultivated plants can have a significant impact not only on food production, but also on the appropriate usage of increasingly scarce freshwater supplies. Accordingly, the cost-effective detection and monitoring of changes in their water content are longstanding remote sensing goals. Existing procedures employed to achieve these goals are largely based on the spectral responses of plant leaves in the infrared domain where the light absorption within the foliar tissues is dominated by water. Recently, it has been suggested that such procedures could be implemented using spectral responses, more specifically spectral subsurface reflectance to transmittance ratios, obtained in the visible domain. The basis for this proposition resides on the premise that a reduced water content (RWC) can result in histological changes whose effects on the foliar optical properties may not be limited to the infrared domain. However, the experiments leading to this proposition were performed on detached leaves, which were not influenced by the whole plant's adaptation mechanisms to water stress. In this work, we investigate whether the spectral responses of living plant leaves in the visible domain can lead to reliable RWC estimations. We employ measured biophysical data and predictive light transport simulations in order to extend qualitatively and quantitatively the scope of previous studies in this area. Our findings indicate that the living specimens' physiological responses to water stress should be taken into account in the design of new procedures for the cost-effective RWC estimation using visible subsurface reflectance to transmittance ratios.

  18. Fundus autofluorescence in central serous chorioretinopathy:association with spectral-domain optical coherence tomography and fluorescein angiography

    Directory of Open Access Journals (Sweden)

    Peng Zhang

    2015-10-01

    Full Text Available AIM: To evaluate the correlation among changes in fundus autofluorescence (AF measured using infrared fundus AF (IR-AF and short-wave length fundus AF (SW-AF with changes in spectral-domain optical coherence tomography (SD-OCT and fluorescein angiography (FA in central serous chorioretinopathy (CSC.METHODS:Two hundred and twenty consecutive patients with CSC were included. In addition to AF, patients were assessed by means of SD-OCT and FA. Abnormalities in images of IR-AF, SW-AF, FA were analyzed and correlated with the corresponding outer retinal alterations in SD-OCT findings.RESULTS:Eyes with abnormalities on either IR-AF or SW-AF were found in 256 eyes (58.18%, among them 256 eyes (100% showed abnormal IR-AF, but SW-AF abnormalities were present only in 213 eyes (83.20%. The hypo-IR-AF corresponded to accumulation of sub-retinal liquid, collapse of retinal pigment epithelium (RPE or detachment of RPE with or without RPE leakage point in the corresponding area. The hyper-IR-AF corresponded to the area with loss of the ellipsoid portion of the inner segments and sub-sensory retinal deposits or focal melanogenesis under sensory retina. The hypo-SW-AF corresponded to accumulation of sub-retinal liquid or atrophy of RPE. The hyper-SW-AF associated with sub-sensory retinal deposits, detachment of RPE and focal melanogenesis.CONCLUSION:IR-AF was more sensitive than SW-AF and FA for identifying pathological abnormalities in CSC. The characteristics of IR-AF in CSC were attributable to the modification of melanin in the RPE. IR-AF should be used as a common diagnostic tool for identifying pathological lesion in CSC.KEYWORDS:central serous chorioretinopathy; fluorescein angiography; fundus autofluorescence; optical coherence tomography

  19. Macular thickness and macular volume measurements using spectral domain optical coherence tomography in normal Nepalese eyes

    Directory of Open Access Journals (Sweden)

    Pokharel A

    2016-03-01

    Full Text Available Amrit Pokharel,1 Gauri Shankar Shrestha,2 Jyoti Baba Shrestha2 1Department of Ophthalmology, Kathmandu Medical College Teaching Hospital, 2B P Koirala Lions Centre for Ophthalmic Studies, Institute of Medicine, Kathmandu, Nepal Purpose: To record the normative values for macular thickness and macular volume in normal Nepalese eyes. Methods: In all, 126 eyes of 63 emmetropic subjects (mean age: 21.17±6.76 years; range: 10–37 years were assessed for macular thickness and macular volume, using spectral domain-optical coherence tomography over 6×6 mm2 in the posterior pole. A fast macular thickness protocol was employed. Statistics such as the mean, median, standard deviation, percentiles, and range were used, while a P-value was set at 0.05 to test significance. Results: Average macular thickness and total macular volume were larger in males compared to females. With each year of increasing age, these variables decreased by 0.556 µm and 0.0156 mm3 for average macular thickness and total macular volume, respectively. The macular thickness was greatest in the inner superior section and lowest at the center of the fovea. The volume was greatest in the outer nasal section and thinnest in the fovea. The central subfield thickness (r=-0.243, P=0.055 and foveal volume (r=0.216, P=0.09 did not correlate with age. Conclusion: Males and females differ significantly with regard to macular thickness and macular volume measurements. Reports by other studies that the increase in axial length reduced thickness and volume, were negated by this study which found a positive correlation among axial length, thickness, and volume. Keywords: macular thickness, macular volume, optical coherence tomography, Nepal

  20. Spectral domain OCT versus time domain OCT in the evaluation of macular features related to wet age-related macular degeneration

    Directory of Open Access Journals (Sweden)

    Isola V

    2012-02-01

    Full Text Available Luisa Pierro1, Elena Zampedri1, Paolo Milani2, Marco Gagliardi1, Vincenzo Isola2, Alfredo Pece21Department of Ophthalmology, University Vita-Salute, Scientific Institute San Raffaele, Milano, Italy, 2Fondazione Retina 3000, Milano, ItalyBackground: The aim of this study was to compare the agreement between spectral domain optical coherence tomography (SD OCT and time domain stratus OCT (TD OCT in evaluating macular morphology alterations in wet age-related macular degeneration (AMD.Methods: This retrospective study was performed on 77 eyes of 77 patients with primary or recurring subfoveal choroidal neovascularization secondary to AMD. All patients underwent OCT examination using Zeiss Stratus OCT 3 (Carl Zeiss Meditec Inc, Dublin, CA and Opko OTI Spectral SLO/OCT (Ophthalmic Technologies Inc, Toronto, Canada. In all radial line scans, the presence of intraretinal edema (IRE, serous pigment epithelium detachment (sPED, neurosensory serous retinal detachment (NSRD, epiretinal membrane (EM, inner limiting membrane thickening (ILMT, and hard exudates (HE were evaluated. The degree of matching was quantified by Kappa measure of agreement.Results: The percentage distribution of TD OCT findings versus SD OCT findings was: IRE 36.3% versus 77.9%, sPED 57.1% versus 85.7%, NSRD 38.9% versus 53.2%, EM 10.5% versus 26.3%, ILMT 3.8% versus 32.4%, and HE 6.4% versus 54.5%. The agreement was as follows: sPED: kappa value 0.15; NSRD: kappa value 0.61; IRE: kappa value 0.18; EM: kappa value 0.41; ILMT: kappa value 0.02; HE: kappa value 0.06.Conclusion: The agreement in the evaluation of macular lesions between the two techniques is poor and depends on the lesion considered. SD OCT allows better detection of the alterations typically related to choroidal neovascularization such as IRE, PED, ILM thickening, and HE. Consequently its use should be strongly considered in patients with wet AMD.Keywords: spectral domain, OCT, time domain, macular degeneration, AMD

  1. Age, Sex, and Ethnic Variations in Inner and Outer Retinal and Choroidal Thickness on Spectral-Domain Optical Coherence Tomography.

    Science.gov (United States)

    Bafiq, Rinoza; Mathew, Raeba; Pearce, Elizabeth; Abdel-Hey, Ahmed; Richardson, Matthew; Bailey, Thomas; Sivaprasad, Sobha

    2015-11-01

    To evaluate age, sex, and ethnic variations in inner and outer retinal and choroidal thickness and foveal pit, using spectral-domain optical coherence tomography (SD OCT). Single-center observational cross-sectional study. Ninety randomly selected, healthy individuals of white, black, and South Asian origin underwent SD OCT raster and enhanced depth imaging scan. Manual measurements of inner and outer retinal thickness and choroidal thickness up to 3 mm nasal and temporal to the fovea were performed. The age, sex, and ethnic differences in these parameters were analyzed. The mean inner retinal thickness was lower by approximately 12 μm in black subjects across the central retina compared to white subjects (P ethnic groups but the temporal choroid was significantly thinner in black subjects (P < .05). The choroid showed an age-related decline in thickness of 2 μm per year of age of the subjects. Interethnic differences include wider fovea, lower central foveal thickness, and thinner inner retina in eyes of black subjects compared to their white and South Asian counterparts. Copyright © 2015 Elsevier Inc. All rights reserved.

  2. Relationship between macular ganglion cell complex thickness and macular outer retinal thickness: a spectral-domain optical coherence tomography study.

    Science.gov (United States)

    Kita, Yoshiyuki; Kita, Ritsuko; Takeyama, Asuka; Anraku, Ayako; Tomita, Goji; Goldberg, Ivan

    2013-01-01

    To assess the relationship between macular ganglion cell complex and macular outer retinal thicknesses. Case-control study. Forty-two normal eyes and 91 eyes with primary open-angle glaucoma were studied. Spectral-domain optical coherence tomography (RTVue-100) was used to measure the macular ganglion cell complex and macular outer retinal thickness. Ganglion cell complex to outer retinal thickness ratio was also calculated. The relationships between the ganglion cell complex and outer retinal thicknesses and between the ganglion cell complex to outer retinal thickness ratio and outer retinal thickness were evaluated. There was a positive correlation between ganglion cell complex and outer retinal thicknesses in the normal group and the glaucoma group (r = 0.53, P variation in the outer retinal thickness. Therefore, when determining the ganglion cell complex, it seems necessary to consider the outer retinal thickness as well. We propose the ratio as a suitable parameter to account for individual variations in outer retinal thickness. © 2013 The Authors. Clinical and Experimental Ophthalmology © 2013 Royal Australian and New Zealand College of Ophthalmologists.

  3. Effect of Hydroxychloroquine on the Retinal Layers: A Quantitative Evaluation with Spectral-Domain Optical Coherence Tomography

    Directory of Open Access Journals (Sweden)

    Hasim Uslu

    2016-01-01

    Full Text Available Purpose. To evaluate the effect of hydroxychloroquine on retinal pigment epithelium- (RPE- Bruch’s membrane complex, photoreceptor outer segment, and macular ganglion cell-inner plexiform layer (GCIPL thicknesses using spectral-domain optical coherence tomography (SD-OCT. Methods. In this prospective case-control study, 51 eyes of 51 hydroxychloroquine patients and 30 eyes of 30 healthy subjects were included. High-quality images were obtained using a Cirrus HD-OCT with 5-line raster mode; the photoreceptor inner segment (IS and outer segment (OS, sum of the segments (IS + OS, and RPE-Bruch’s membrane complex were analyzed. Results. The thicknesses of the IS + OS and OS layers were significantly lower in the hydroxychloroquine subjects compared to the control subjects (P<0.05. RPE-Bruch’s membrane complex thicknesses were significantly higher in the hydroxychloroquine subjects than for those of the control subjects (P<0.05. The minimum and temporal-inferior macular GCIPL thicknesses were significantly different between the patients with hydroxychloroquine use and the control subjects (P=0.04 and P=0.03, resp.. Conclusions. The foveal photoreceptor OS thinning, loss of GCIPL, and RPE-Bruch’s membrane thickening were detected in patients with hydroxychloroquine therapy. This quantitative approach using SD-OCT images may have important implications to use as an early indicator of retinal toxicity without any visible signs of hydroxychloroquine retinopathy.

  4. Agreement of angle closure assessments between gonioscopy, anterior segment optical coherence tomography and spectral domain optical coherence tomography.

    Science.gov (United States)

    Tay, Elton Lik Tong; Yong, Vernon Khet Yau; Lim, Boon Ang; Sia, Stelson; Wong, Elizabeth Poh Ying; Yip, Leonard Wei Leon

    2015-01-01

    To determine angle closure agreements between gonioscopy and anterior segment optical coherence tomography (AS-OCT), as well as gonioscopy and spectral domain OCT (SD-OCT). A secondary objective was to quantify inter-observer agreements of AS-OCT and SD-OCT assessments. Seventeen consecutive subjects (33 eyes) were recruited from the study hospital's Glaucoma clinic. Gonioscopy was performed by a glaucomatologist masked to OCT results. OCT images were read independently by 2 other glaucomatologists masked to gonioscopy findings as well as each other's analyses of OCT images. Totally 84.8% and 45.5% of scleral spurs were visualized in AS-OCT and SD-OCT images respectively (Pgonioscopy was fair at k=0.31 (95% confidence interval, CI: 0.03-0.59) and k=0.35 (95% CI: 0.07-0.63) for reader 1 and 2 respectively. The agreement for angle closure between SD-OCT and gonioscopy was fair at k=0.21 (95% CI: 0.07-0.49) and slight at k=0.17 (95% CI: 0.08-0.42) for reader 1 and 2 respectively. The inter-reader agreement for angle closure in AS-OCT images was moderate at 0.51 (95% CI: 0.13-0.88). The inter-reader agreement for angle closure in SD-OCT images was slight at 0.18 (95% CI: 0.08-0.45). Significant proportion of scleral spurs were not visualised with SD-OCT imaging resulting in weaker inter-reader agreements. Identifying other angle landmarks in SD-OCT images will allow more consistent angle closure assessments. Gonioscopy and OCT imaging do not always agree in angle closure assessments but have their own advantages, and should be used together and not exclusively.

  5. Donor disc attachment assessment with intraoperative spectral optical coherence tomography during descemet stripping automated endothelial keratoplasty

    Directory of Open Access Journals (Sweden)

    Edward Wylegala

    2013-01-01

    Full Text Available Optical coherence tomography has already been proven to be useful for pre- and post-surgical anterior eye segment assessment, especially in lamellar keratoplasty procedures. There is no evidence for intraoperative usefulness of optical coherence tomography (OCT. We present a case report of the intraoperative donor disc attachment assessment with spectral-domain optical coherence tomography in case of Descemet stripping automated endothelial keratoplasty (DSAEK surgery combined with corneal incisions. The effectiveness of the performed corneal stab incisions was visualized directly by OCT scan analysis. OCT assisted DSAEK allows the assessment of the accuracy of the Descemet stripping and donor disc attachment.

  6. Comparison of choroidal thickness using swept-source and spectral-domain optical coherence tomography in normal Indian eyes.

    Science.gov (United States)

    Narendran, Siddharth; Manayath, George; Venkatapathy, Narendran

    2018-01-01

    Choroidal thickness measurements are reported to differ between spectral-domain optical coherence tomography (SD-OCT) and swept-source OCT (SS-OCT). The aim of this study was to assess the comparability of choroidal thickness measurements using SS-OCT and SD-OCT devices among normal participants. This was a prospective study of 31 (62 eyes) normal participants. Choroidal imaging was performed sequentially with the Spectralis OCT (SD-OCT) and the deep range imaging OCT (DRI OCT-1) (SS-OCT) using standardized imaging protocols. The subfoveal choroidal thickness (SFChT) was measured manually by two masked retinal specialists. Paired t -tests and intraclass correlation coefficients (ICCs) were used to compare the measurements. The mean SFChT was 319.5 μm and 325.3 μm for DRI OCT-1 and Spectralis OCT, respectively ( P = 0.001), with a mean difference of 5.9 with ICC of 0.97. The mean difference in choroidal thickness between the OCT devices was larger among eyes with choroidal thickness > 350 μm compared with eyes with thinner choroids (8.0 μm vs. 4.7 μm). SFChT measurements are comparable between DRI OCT-1 and Spectralis OCT. The variability between the devices increases in thicker choroids.

  7. Mechanism of Retinal Pigment Epithelium Tear Formation Following Intravitreal Anti–Vascular Endothelial Growth Factor Therapy Revealed by Spectral-Domain Optical Coherence Tomography

    DEFF Research Database (Denmark)

    Nagiel, Aaron; Freund, K Bailey; Spaide, Richard F

    2013-01-01

    to the retracted RPE. In all eyes, the RPE ruptured along a segment of bare RPE not in contact with the CNV or Bruch membrane. CONCLUSIONS: Eyes with vascularized PEDs secondary to AMD may show specific OCT findings that increase the risk for RPE tear following intravitreal anti-VEGF injection. Rapid involution......PURPOSE: To demonstrate the mechanism by which retinal pigment epithelium (RPE) tears occur in eyes with neovascular age-related macular degeneration (AMD) treated with intravitreal anti-vascular endothelial growth factor (VEGF) agents using spectral-domain optical coherence tomography (OCT......). DESIGN: Retrospective observational case series. METHODS: OCT images of 8 eyes that developed RPE tears following the administration of intravitreal anti-VEGF agents for neovascular AMD were evaluated. Pretear and posttear images were compared in order to elucidate the mechanism by which RPE tears occur...

  8. Comparisons of spectrally-enhanced asymmetrically-clipped optical OFDM systems.

    Science.gov (United States)

    Lowery, Arthur James

    2016-02-22

    Asymmetrically clipped optical orthogonal frequency-division multiplexing (ACO-OFDM) is a technique that sacrifices spectral efficiency in order to transmit an orthogonally frequency-division multiplexed signal over a unipolar channel, such as a directly modulated direct-detection fiber or free-space channel. Several methods have been proposed to regain this spectral efficiency, including: asymmetrically clipped DC-biased optical OFDM (ADO-OFDM), enhanced U-OFDM (EU-OFDM), spectral and energy efficient OFDM (SEE-OFDM), Hybrid-ACO-OFDM and Layered-ACO-OFDM. This paper presents simulations up to high-order constellation sizes to show that Layered-ACO-OFDM offers the highest receiver sensitivity for a given optical power at spectral efficiencies above 3 bit/s/Hz. For comparison purposes, white Gaussian noise is added at the receiver, component nonlinearities are not considered, and the fiber is considered to be linear and dispersion-less. The simulations show that LACO-OFDM has a 7-dB sensitivity advantage over DC-biased OFDM (DCO-OFDM) for 1024-QAM at 87.5% of DCO-OFDM's spectral efficiency, at the same bit rate and optical power. This is approximately equivalent to a 4.4-dB advantage at the same spectral efficiency of 87.7% if 896-QAM were to be used for DCO-OFDM.

  9. Signal processing in an acousto-optical spectral colorimeter

    Science.gov (United States)

    Emeljanov, Sergey P.; Kludzin, Victor V.; Kochin, Leonid B.; Medvedev, Sergey V.; Polosin, Lev L.; Sokolov, Vladimir K.

    2002-02-01

    The algorithms of spectrometer signals processing in the acousto-optical spectral colorimeter, proposed earlier are discussed. This processing is directional on distortion elimination of an optical system spectral characteristics and photoelectric transformations, and also for calculation of tristimulus coefficients X,Y,Z in an international colorimetric system of a CIE - 31 and transformation them in coordinates of recommended CIE uniform contrast systems LUV and LAB.

  10. Agreement of angle closure assessments between gonioscopy, anterior segment optical coherence tomography and spectral domain optical coherence tomography

    Directory of Open Access Journals (Sweden)

    Elton Lik Tong Tay

    2015-04-01

    Full Text Available AIM: To determine angle closure agreements between gonioscopy and anterior segment optical coherence tomography (AS-OCT, as well as gonioscopy and spectral domain OCT (SD-OCT. A secondary objective was to quantify inter-observer agreements of AS-OCT and SD-OCT assessments. METHODS: Seventeen consecutive subjects (33 eyes were recruited from the study hospital’s Glaucoma clinic. Gonioscopy was performed by a glaucomatologist masked to OCT results. OCT images were read independently by 2 other glaucomatologists masked to gonioscopy findings as well as each other’s analyses of OCT images. RESULTS: Totally 84.8% and 45.5% of scleral spurs were visualized in AS-OCT and SD-OCT images respectively (P<0.01. The agreement for angle closure between AS-OCT and gonioscopy was fair at k=0.31 (95% confidence interval, CI: 0.03-0.59 and k=0.35 (95% CI: 0.07-0.63 for reader 1 and 2 respectively. The agreement for angle closure between SD-OCT and gonioscopy was fair at k=0.21 (95% CI: 0.07-0.49 and slight at k=0.17 (95% CI: 0.08-0.42 for reader 1 and 2 respectively. The inter-reader agreement for angle closure in AS-OCT images was moderate at 0.51 (95% CI: 0.13-0.88. The inter-reader agreement for angle closure in SD-OCT images was slight at 0.18 (95% CI: 0.08-0.45. CONCLUSION: Significant proportion of scleral spurs were not visualised with SD-OCT imaging resulting in weaker inter-reader agreements. Identifying other angle landmarks in SD-OCT images will allow more consistent angle closure assessments. Gonioscopy and OCT imaging do not always agree in angle closure assessments but have their own advantages, and should be used together and not exclusively.

  11. Evaluation of Macular Ganglion Cell-inner Plexiform Layer and Choroid in Psoriasis Patients Using Enhanced Depth Imaging Spectral Domain Optical Coherence Tomography.

    Science.gov (United States)

    Ersan, Ismail; Kilic, Sevilay; Arikan, Sedat; Kara, Selcuk; Işik, Selda; Gencer, Baran; Ogretmen, Zerrin

    2017-08-01

    To evaluate changes in the thickness of the central macula, macular ganglion cell-inner plexiform layer (mGCIPL), and subfoveal choroid in patients with psoriasis using spectral domain optical coherence tomography (SD-OCT). The measurements of macular, mGCIPL thicknesses and subfoveal choroidal thickness (SFCT) obtained by SD-OCT of psoriasis patients (n = 46). These measurements were compared with those of 50 healthy controls. The macular, mGCIPL, and choroidal thicknesses did not differ between the controls and psoriatic subjects (p>0.05). When the patients were divided into two distinct groups, only the SFCT was significantly thicker in the severe psoriasis group compared with the mild psoriasis group (p = 0.003). These findings suggest that choroidal alterations are seen without macular changes in patients with psoriasis. Severe psoriasis appears to be related to increases in SFCT as a consequence of possible inflammatory cascades that are part of the disease's pathogenesis.

  12. Effect of ocular magnification on macular measurements made using spectral domain optical coherence tomography

    Directory of Open Access Journals (Sweden)

    Mohana Kuppuswamy Parthasarathy

    2015-01-01

    Full Text Available Aim: The aim of the present study was to study the effect of ocular magnification on macular measurements made using spectral domain optical coherence tomography (OCT. Materials and Methods: One hundred and fifty-one subjects were included from the normative study of foveal morphology carried out at our hospital. Subjects underwent comprehensive eye examination and macular scanning using Cirrus high-definition OCT and axial length (AXL measurement. Macular cube 512 × 128 scan protocol was used for scanning the macula. Automated measurements of the fovea namely foveal diameter, foveal slope (lateral measurements and foveal depth (axial measurement were taken. A correction factor for ocular magnification was done using the formula t = p × q × s, where "t0" is the corrected measurement, "p" is the magnification of OCT, "q0" is the ocular magnification, and "s" is the measurement on OCT without correction. The difference between corrected and uncorrected measurements was evaluated for statistical significance. Results: Mean AXL was 22.95 ± 0.78 mm. Refractive error ranged from −3D to +4D. Mean difference between measured and corrected foveal diameter, slope and depth was 166.05 ± 95.37 ΅m (P < 0.001, 0.81° ± 0.53° (P < 0.001 and 0.05 ± 0.49 ΅m (P = 0.178 respectively. AXL lesser than the OCT calibrated value of 24.46 mm showed an increased foveal diameter (r = 0.961, P < 0.001 and a reduced foveal slope (r = −0.863, P < 0.001 than the corrected value. Conclusion: Lateral measurements made on OCT varied with AXL s other than the OCT calibrated value of 24.46 mm. Therefore, to estimate the actual dimensions of a retinal lesion using OCT, especially lateral dimensions, we recommend correction for the ocular magnification factor.

  13. Spectral Domain Optical Coherence Tomography in Glaucoma: Qualitative and Quantitative Analysis of the Optic Nerve Head and Retinal Nerve Fiber Layer (An AOS Thesis)

    Science.gov (United States)

    Chen, Teresa C.

    2009-01-01

    Purpose: To demonstrate that video-rate spectral domain optical coherence tomography (SDOCT) can qualitatively and quantitatively evaluate optic nerve head (ONH) and retinal nerve fiber layer (RNFL) glaucomatous structural changes. To correlate quantitative SDOCT parameters with disc photography and visual fields. Methods: SDOCT images from 4 glaucoma eyes (4 patients) with varying stages of open-angle glaucoma (ie, early, moderate, late) were qualitatively contrasted with 2 age-matched normal eyes (2 patients). Of 61 other consecutive patients recruited in an institutional setting, 53 eyes (33 patients) met inclusion/exclusion criteria for quantitative studies. Images were obtained using two experimental SDOCT systems, one utilizing a superluminescent diode and the other a titanium:sapphire laser source, with axial resolutions of about 6 μm and 3 μm, respectively. Results: Classic glaucomatous ONH and RNFL structural changes were seen in SDOCT images. An SDOCT reference plane 139 μm above the retinal pigment epithelium yielded cup-disc ratios that best correlated with masked physician disc photography cup-disc ratio assessments. The minimum distance band, a novel SDOCT neuroretinal rim parameter, showed good correlation with physician cup-disc ratio assessments, visual field mean deviation, and pattern standard deviation (P values range, .0003–.024). RNFL and retinal thickness maps correlated well with disc photography and visual field testing. Conclusions: To our knowledge, this thesis presents the first comprehensive qualitative and quantitative evaluation of SDOCT images of the ONH and RNFL in glaucoma. This pilot study provides basis for developing more automated quantitative SDOCT-specific glaucoma algorithms needed for future prospective multicenter national trials. PMID:20126502

  14. Morphometric analysis of fovea with spectral-domain optical coherence tomography and visual outcome postsurgery for retinal detachment

    Directory of Open Access Journals (Sweden)

    Manish Nagpal

    2014-01-01

    Full Text Available Purpose: The purpose of this study was to correlate the postoperative best-corrected visual acuity (BCVA with spectral-domain optical coherence tomography (SD-OCT findings in fovea involving rhegmatogenous retinal detachment (RRD surgery. Materials and Methods: Thirty eyes with preoperative fovea-involving RRD, who underwent scleral buckling (SB (6 eyes and pars plana vitrectomy (PPV (19 eyes and combined SB and PPV (5 eyes were recruited. Patients underwent clinical examination and SD-OCT scan of fovea preoperatively and at 30 days and 90 days postoperatively. The correlations between SD-OCT findings and BCVA were analyzed. Results: Inner segment/outer segment (IS/OS junction integrity was the indicator of better BCVA at 30 days and 90 days (P = 0.0002 and P = 0.0003, respectively whereas outer retinal corrugation (ORC was related to worse BCVA at 30 days and 90 days (P = 0.001. External limiting membrane did not have a co-relation with visual outcome, but cystoid macular edema showed co-relation at 90 days (P = 0.047. All eyes of SB and 3 eyes of PPV had a minimal subfoveal fluid at 30 days follow-up that had no effect on visual acuity. All retinas were attached at final follow-up. Conclusion: IS/OS junction integrity and ORC may be important predictors of postoperative visual outcome after anatomically successful RRD surgery.

  15. Comparison of peripapillary choroidal thickness measurements via spectral domain optical coherence tomography with and without enhanced depth imaging.

    Science.gov (United States)

    Ayyildiz, Onder; Kucukevcilioglu, Murat; Ozge, Gokhan; Koylu, Mehmet Talay; Ozgonul, Cem; Gokce, Gokcen; Mumcuoglu, Tarkan; Durukan, Ali Hakan; Mutlu, Fatih Mehmet

    2016-05-01

    To compare peripapillary choroidal thickness (PP-CT) measurements using a spectral domain optical coherence tomography (SD-OCT) device with and without enhanced depth imaging (EDI). Sixty healthy subjects aged from 18 to 40 years were included in this study. PP-CTs were measured in the right eyes by manual segmentation via SD-OCT both with and without EDI. The intraclass correlation coefficient (ICC) for each technique and comparison of PP-CT measurements between two techniques were evaluated. The correlation between retinal nerve fiber layer (RNFL) thickness and PP-CT was also explored on images of SD-OCT without EDI. The PP-CT measurements of 55 subjects were evaluated. The ICC was 0.999 (95% CI: 0.998-1.0, p  0.05). Additionally, there was no correlation between RNFL thickness and PP-CT (r = -0.109; p = 0.335). The PP-CT measurements via SD-OCT without EDI were consistent with the measurements via SD-OCT with EDI. Ophthalmologists who do not have access to EDI technology can use images of SD-OCT without EDI to measure the peripapillary choroid for research purposes. However, thicker peripapillary choroids cannot be measured using this technique and require further modifications or newer technologies, such as SD-OCT with EDI.

  16. Impacts of age and sex on retinal layer thicknesses measured by spectral domain optical coherence tomography with Spectralis.

    Science.gov (United States)

    Nieves-Moreno, María; Martínez-de-la-Casa, José M; Morales-Fernández, Laura; Sánchez-Jean, Rubén; Sáenz-Francés, Federico; García-Feijoó, Julián

    2018-01-01

    To examine differences in individual retinal layer thicknesses measured by spectral domain optical coherence tomography (SD-OCT) (Spectralis®) produced with age and according to sex. Cross-sectional, observational study. The study was conducted in 297 eyes of 297 healthy subjects aged 18 to 87 years. In one randomly selected eye of each participant the volume and mean thicknesses of the different macular layers were measured by SD-OCT using the instrument's macular segmentation software. Volume and mean thickness of macular retinal nerve fiber layer (mRNFL), ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer (INL), outer plexiform layer (OPL), outer nuclear layer (ONL), retinal pigmentary epithelium (RPE) and photoreceptor layer (PR). Retinal thickness was reduced by 0.24 μm for every one year of age. Age adjusted linear regression analysis revealed mean GCL, IPL, ONL and PR thickness reductions and a mean OPL thickness increase with age. Women had significantly lower mean GCL, IPL, INL, ONL and PR thicknesses and volumes and a significantly greater mRNFL volume than men. The thickness of most retinal layers varies both with age and according to sex. Longitudinal studies are needed to determine the rate of layer thinning produced with age.

  17. Spectral Behavior of Weakly Compressible Aero-Optical Distortions

    Science.gov (United States)

    Mathews, Edwin; Wang, Kan; Wang, Meng; Jumper, Eric

    2016-11-01

    In classical theories of optical distortions by atmospheric turbulence, an appropriate and key assumption is that index-of-refraction variations are dominated by fluctuations in temperature and the effects of turbulent pressure fluctuations are negligible. This assumption is, however, not generally valid for aero-optical distortions caused by turbulent flow over an optical aperture, where both temperature and pressures fluctuations may contribute significantly to the index-of-refraction fluctuations. A general expression for weak fluctuations in refractive index is derived using the ideal gas law and Gladstone-Dale relation and applied to describe the spectral behavior of aero-optical distortions. Large-eddy simulations of weakly compressible, temporally evolving shear layers are then used to verify the theoretical results. Computational results support theoretical findings and confirm that if the log slope of the 1-D density spectrum in the inertial range is -mρ , the optical phase distortion spectral slope is given by - (mρ + 1) . The value of mρ is then shown to be dependent on the ratio of shear-layer free-stream densities and bounded by the spectral slopes of temperature and pressure fluctuations. Supported by HEL-JTO through AFOSR Grant FA9550-13-1-0001 and Blue Waters Graduate Fellowship Program.

  18. High Spectral Density Optical Communication Technologies

    CERN Document Server

    Nakazawa, Masataka; Miyazaki, Tetsuya

    2010-01-01

    The latest hot topics of high-spectral density optical communication systems using digital coherent optical fibre communication technologies are covered by this book. History and meaning of a "renaissance" of the technology, requirements to the Peta-bit/s class "new generation network" are also covered in the first part of this book. The main topics treated are electronic and optical devices, digital signal processing including forward error correction, modulation formats as well as transmission and application systems. The book serves as a reference to researchers and engineers.

  19. All-optical OFDM demultiplexing by spectral magnification and band-pass filtering.

    Science.gov (United States)

    Palushani, E; Mulvad, H C Hansen; Kong, D; Guan, P; Galili, M; Oxenløwe, L K

    2014-01-13

    We propose a simple OFDM receiver allowing for the use of standard WDM receivers to receive spectrally advanced OFDM signals. We propose to spectrally magnify the optical-OFDM super-channels using a spectral telescope consisting of two time-lenses, which enables reduced inter-carrier-interference in subcarrier detection by simple band-pass filtering. A demonstration on an emulated 100 Gbit/s DPSK optical-OFDM channel shows improved sensitivities after 4-times spectral magnification.

  20. Segmentation of the geographic atrophy in spectral-domain optical coherence tomography and fundus autofluorescence images.

    Science.gov (United States)

    Hu, Zhihong; Medioni, Gerard G; Hernandez, Matthias; Hariri, Amirhossein; Wu, Xiaodong; Sadda, Srinivas R

    2013-12-30

    Geographic atrophy (GA) is the atrophic late-stage manifestation of age-related macular degeneration (AMD), which may result in severe vision loss and blindness. The purpose of this study was to develop a reliable, effective approach for GA segmentation in both spectral-domain optical coherence tomography (SD-OCT) and fundus autofluorescence (FAF) images using a level set-based approach and to compare the segmentation performance in the two modalities. To identify GA regions in SD-OCT images, three retinal surfaces were first segmented in volumetric SD-OCT images using a double-surface graph search scheme. A two-dimensional (2-D) partial OCT projection image was created from the segmented choroid layer. A level set approach was applied to segment the GA in the partial OCT projection image. In addition, the algorithm was applied to FAF images for the GA segmentation. Twenty randomly chosen macular SD-OCT (Zeiss Cirrus) volumes and 20 corresponding FAF (Heidelberg Spectralis) images were obtained from 20 subjects with GA. The algorithm-defined GA region was compared with consensus manual delineation performed by certified graders. The mean Dice similarity coefficients (DSC) between the algorithm- and manually defined GA regions were 0.87 ± 0.09 in partial OCT projection images and 0.89 ± 0.07 in registered FAF images. The area correlations between them were 0.93 (P segment GA regions in both SD-OCT and FAF images. This approach demonstrated good agreement between the algorithm- and manually defined GA regions within each single modality. The GA segmentation in FAF images performed better than in partial OCT projection images. Across the two modalities, the GA segmentation presented reasonable agreement.

  1. Frequency doubling technique perimetry and spectral domain optical coherence tomography in patients with early glaucoma.

    Science.gov (United States)

    Horn, F K; Mardin, C Y; Bendschneider, D; Jünemann, A G; Adler, W; Tornow, R P

    2011-01-01

    To assess the combined diagnostic power of frequency-doubling technique (FDT)-perimetry and retinal nerve fibre layer (RNFL) thickness measurements with spectral domain optical coherence tomography (SDOCT). The study included 330 experienced participants in five age-related groups: 77 'preperimetric' open-angle glaucoma (OAG) patients, 52 'early' OAG, 50 'moderate' OAG, 54 ocular hypertensive patients, and 97 healthy subjects. For glaucoma assessment in all subjects conventional perimetry, evaluation of fundus photographs, FDT-perimetry and RNFL thickness measurement with SDOCT was done. Glaucomatous visual field defects were classified using the Glaucoma Staging System. FDT evaluation used a published method with casewise calculation of an 'FDT-score', including all missed localized probability levels. SDOCT evaluation used mean RNFL thickness and a new individual SDOCT-score considering normal confidence limits in 32 sectors of a peripapillary circular scan. To examine the joined value of both methods a combined score was introduced. Significance of the difference between Receiver-operating-characteristic (ROC) curves was calculated for a specificity of 96%. Sensitivity in the preperimetric glaucoma group was 44% for SDOCT-score, 25% for FDT-score, and 44% for combined score, in the early glaucoma group 83, 81, and 89%, respectively, and in the moderate glaucoma group 94, 94, and 98%, respectively, all at a specificity of 96%. ROC performance of the newly developed combined score is significantly above single ROC curves of FDT-score in preperimetric and early OAG and above RNFL thickness in moderate OAG. Combination of function and morphology by using the FDT-score and the SDOCT-score performs equal or even better than each single method alone.

  2. In vivo visualization of photoreceptor layer and lipofuscin accumulation in Stargardt’s disease and fundus flavimaculatus by high resolution spectral-domain optical coherence tomography

    Directory of Open Access Journals (Sweden)

    Giuseppe Querques

    2009-12-01

    Full Text Available Giuseppe Querques, Rosy Prato, Gabriel Coscas, Gisèle Soubrane, Eric H SouiedDepartment of Ophthalmology, Hopital Intercommunal de Creteil, University Paris XII, FranceIntroduction: To assess photoreceptor (PR layer morphology in patients with Stargardt’s disease (STGD and fundus flavimaculatus (FFM using high resolution spectral domain optical coherence tomography (HD-OCT; OCT 4000 Cirrus, Humphrey-Zeiss, San Leandro, CA.Methods: This was a prospective observational case series. Sixteen consecutive patients with STGD and FFM underwent a complete ophthalmologic examination. Optical coherence tomography examination was performed with HD-OCT, a high-speed (27,000 axial scans per second OCT system using spectral/Fourier domain detection, with an axial image resolution of 5 µm.Results: A total of 31 eyes were included in the study. Transverse loss of the PR layer in the foveal region was shown by HD-OCT. Twenty eyes with clinically evident central atrophy had a disruption of either the Verhoeff‘s membrane (VM or the layer corresponding to the interface of inner segment (IS and outer segment (OS of PR in the foveal region. Among these eyes, 12/20 eyes had a loss of the PR layer (loss of both VM and IS-OS interface in the foveal region. Eleven eyes (11/31 without clinically evident central atrophy had an intact interface of IS and OS of PR centrally. Moreover, we observed hyperreflective deposits: type 1 lesions located within the retinal pigment epithelium (RPE layer and at the level of the outer segments of PR, and type 2 lesions located at the level of the outer nuclear layer and clearly separated from the RPE layer. Type 1 lesions alone were associated with absence of loss of the PR layer in the foveal region in all eyes; type 2 lesions were always associated with presence of type 1 lesions, and often (8/12 eyes associated with loss of the PR layer within the foveal region. Mean best-corrected visual acuity (BCVA was significantly

  3. Effect of input spectrum on the spectral switch characteristics in a white-light Michelson interferometer.

    Science.gov (United States)

    Brundavanam, Maruthi M; Viswanathan, Nirmal K; Rao, D Narayana

    2009-12-01

    We report here a detailed experimental study to demonstrate the effect of source spectral characteristics such as spectral bandwidth (Deltalambda), peak wavelength (lambda(0)), and shape of the spectrum on the spectral shifts and spectral switches measured due to temporal correlation in a white-light Michelson interferometer operated in the spectral domain. Behavior of the spectral switch characteristics such as the switch position, switch amplitude, and switch symmetry are discussed in detail as a function of optical path difference between the interfering beams. The experimental results are compared with numerical calculations carried out using interference law in the spectral domain with modified source spectral characteristics. On the basis of our results we feel that our study is of critical importance in the selection of source spectral characteristics to further improve the longitudinal resolution or the measurement sensitivity in spectral-domain optical coherence tomography and microscopy.

  4. Towards spectral-domain optical coherence tomography on a silicon chip

    NARCIS (Netherlands)

    Akça, B.I.; Worhoff, Kerstin; Nguyen, V.D.; Kalkman, J.; van Leeuwen, Ton; de Ridder, R.M.; Pollnau, Markus

    Optical coherence tomography (OCT) is a widely used optical imaging technology, particularly in the medical field, since it can provide non-invasive, sub-micrometer resolution diagnostic images of tissue. Current OCT systems contain optical fibers and free-space optical components which make these

  5. From spectral holeburning memory to spatial-spectral microwave signal processing

    International Nuclear Information System (INIS)

    Babbitt, Wm Randall; Barber, Zeb W; Harrington, Calvin; Mohan, R Krishna; Sharpe, Tia; Bekker, Scott H; Chase, Michael D; Merkel, Kristian D; Stiffler, Colton R; Traxinger, Aaron S; Woidtke, Alex J

    2014-01-01

    Many storage and processing systems based on spectral holeburning have been proposed that access the broad bandwidth and high dynamic range of spatial-spectral materials, but only recently have practical systems been developed that exceed the performance and functional capabilities of electronic devices. This paper reviews the history of the proposed applications of spectral holeburning and spatial-spectral materials, from frequency domain optical memory to microwave photonic signal processing systems. The recent results of a 20 GHz bandwidth high performance spectrum monitoring system with the additional capability of broadband direction finding demonstrates the potential for spatial-spectral systems to be the practical choice for solving demanding signal processing problems in the near future. (paper)

  6. Stable multi-domain spectral penalty methods for fractional partial differential equations

    Science.gov (United States)

    Xu, Qinwu; Hesthaven, Jan S.

    2014-01-01

    We propose stable multi-domain spectral penalty methods suitable for solving fractional partial differential equations with fractional derivatives of any order. First, a high order discretization is proposed to approximate fractional derivatives of any order on any given grids based on orthogonal polynomials. The approximation order is analyzed and verified through numerical examples. Based on the discrete fractional derivative, we introduce stable multi-domain spectral penalty methods for solving fractional advection and diffusion equations. The equations are discretized in each sub-domain separately and the global schemes are obtained by weakly imposed boundary and interface conditions through a penalty term. Stability of the schemes are analyzed and numerical examples based on both uniform and nonuniform grids are considered to highlight the flexibility and high accuracy of the proposed schemes.

  7. Optic Nerve Head and Retinal Nerve Fiber Layer Analysis in Ocular Hypertension and Early-Stage Glucoma Using Spectral-Domain Optical Coherence Tomography Copernicus

    Directory of Open Access Journals (Sweden)

    Nilgün Solmaz

    2014-01-01

    Full Text Available Objectives: Evaluation of structural alterations of the optic nerve head (ONH and the retinal nerve fiber layer (RNFL in patients with ocular hypertension (OHT and early-stage glaucoma and assessment of the discriminatory diagnostic performance of spectral-domain optical coherence tomography (SD-OCT Copernicus (Optopol Technology S.A.. Materials and Methods: This study included 59 eyes of a total of 59 patients, 29 of whom were diagnosed with OHT (Group 1 and 30 with early-stage glaucoma (Group 2. The differentiation of early-stage glaucoma and OHT was carried out on the basis of standard achromatic visual field test results. Analysis of the ONH and RNFL thickness of all cases was made using SD-OCT. Group 1 and Group 2 were compared with respect to the ONH parameters and RNFL thickness. The diagnostic sensitivity of the OCT parameters was evaluated by the area under the receiver operating characteristics curves (AUC. Results: The average, superior, inferior, and nasal RNFL thicknesses in early-stage glaucoma cases were approximately 10% (12-14 µm less compared to the OHT eyes, with differences being highly significant (p≤0.001. However, there was no statistically significant difference in the temporal RNFL thicknesses. The most sensitive parameter in the early diagnosis of glaucoma was average RNFL thickness corresponding to AUC: 0.852, followed by AUC: 0.816 and AUC: 0.773 values in superior and inferior RNFL thickness, respectively. In localized RNFL defects, the highest sensitivity corresponded to superior and superonasal quadrants (ACU: 0.805 and ACU: 0.781, respectively. There were not any statistically significant differences between the ONH morphological parameters of the two groups. Conclusion: RNFL analysis obtained using SD-OCT Copernicus is able to discriminate early-stage glaucoma eyes from those with OHT. However, ONH morphological parameters do not have the same diagnostic sensitivity. Turk J Ophthalmol 2014; 44: 35-41

  8. Spectral-domain optical coherence tomography on a silicon chip

    NARCIS (Netherlands)

    Akça, B.I.

    2012-01-01

    Optical coherence tomography (OCT) is a non-invasive optical technique for high-resolution cross-sectional imaging of specimens, with many applications in clinical medicine and industry (e.g. materials testing, quality assurance, and process control). Current state-of-the-art OCT systems operate in

  9. All-optical OFDM demultiplexing by spectral magnification and optical band-pass filtering

    DEFF Research Database (Denmark)

    Palushani, Evarist; Mulvad, Hans Christian Hansen; Kong, Deming

    2013-01-01

    We propose spectral magnification of optical-OFDM super-channels using time-lenses, enabling reduced inter-carrier-interference in subcarrier detection by simple band-pass filtering. A demonstration on an emulated 100 Gbit/s DPSK optical-OFDM channel shows improved sensitivities after 4-times spe...

  10. Ultrafast two-photon absorption optical thresholding of spectrally coded pulses

    Science.gov (United States)

    Zheng, Z.; Shen, S.; Sardesai, H.; Chang, C.-C.; Marsh, J. H.; Karkhanehchi, M. M.; Weiner, A. M.

    1999-08-01

    We report studies on two-photon absorption (TPA) GaAs p-i-n waveguide photodetectors as optical thresholders for proposed ultrashort pulse optical code-division multiple-access (CDMA) systems. For either chirped optical pulses or spectrally phase coded pseudonoise bursts, the TPA photocurrent response reveals a strong pulseshape dependence and shows good agreement with theoretical predictions and results from conventional SHG measurements. The performance limits of the TPA optical thresholders set by the encoded bandwidth in the spectral encoding-decoding process are also discussed based on numerical simulations. Our results show the feasibility of applying such devices as nonlinear intensity discriminators in ultrahigh-speed optical network applications.

  11. COHERENT DETECTION FOR SPECTRAL AMPLITUDE-CODED OPTICAL LABEL SWITCHING SYSTEMS

    DEFF Research Database (Denmark)

    Osadchiy, Alexey Vladimirovich; Tafur Monroy, Idelfonso

    2010-01-01

    Coherent detection for spectrally encoded optical labels is proposed and experimentally demonstrated for three label tones spectrally spaced at 1 GHz. The proposed method utilizes a frequency swept local oscillator in a coherent receiver supported by digital signal processing for improved...... flexibility and upgradeability while reducing label detection subsystem complexity as compared with the conventional optical autocorrelation based approaches....

  12. Grading of Age-Related Macular Degeneration: Comparison between Color Fundus Photography, Fluorescein Angiography, and Spectral Domain Optical Coherence Tomography

    Directory of Open Access Journals (Sweden)

    Nils F. Mokwa

    2013-01-01

    Full Text Available Purpose. To compare color fundus photography (FP, fluorescein angiography (FA, and spectral domain optical coherence tomography (SDOCT for the detection of age-related macular degeneration (AMD, choroidal neovascularisation (CNV, and CNV activity. Methods. FPs, FAs, and SDOCT volume scans from 120 eyes of 66 AMD and control patients were randomly collected. Control eyes were required to show no AMD, but other retinal pathology was allowed. The presence of drusen, pigmentary changes, CNV, and signs for CNV activity was independently analyzed for all imaging modalities. Results. AMD was diagnosed based on FP in 75 eyes. SDOCT and FA showed sensitivity (specificity of 89% (76% and 92% (82%, respectively. CNV was present on FA in 68 eyes. Sensitivity (specificity was 78% (100% for FP and 94% (98% for SDOCT. CNV activity was detected by SDOCT or FA in 60 eyes with an agreement in 46 eyes. Sensitivity was 88% for SDOCT and 88% for FA. FP showed sensitivity of 38% and specificity of 98%. Conclusions. CNV lesions and activity may be missed by FP alone, but FP may help identifying drusen and pigmentary changes. SDOCT is highly sensitive for the detection of AMD, CNV, and CNV activity; however, it cannot fully replace FA.

  13. Normative data for macular thickness by high-definition spectral-domain optical coherence tomography (spectralis).

    Science.gov (United States)

    Grover, Sandeep; Murthy, Ravi K; Brar, Vikram S; Chalam, Kakarla V

    2009-08-01

    To establish normative data for the macular thickness by spectral-domain optical coherence tomography (SD-OCT) in subjects with no known retinal disease. Prospective, observational study in an academic institutional setting. Fifty subjects (age range, 20 to 84 years) with no known retinal disease, best-corrected visual acuity 20/20, and normal intraocular pressure were enrolled. The subjects were divided into 3 age groups: group 1 included subjects 20 to 40 years of age; group 2 included subjects 41 to 60 years of age; and group 3 included subjects 61 years of age and older. All subjects underwent a complete ophthalmologic examination to rule out any retinal diseases or glaucoma. All the OCT scans were performed by a single operator, and data obtained from the right eyes were analyzed by default, unless the right eye did not meet the inclusion criteria, and then data from left eyes were analyzed (n = 4). Central point thickness (CPT) and retinal thickness (RT) in 9 Early Treatment Diabetic Retinopathy Study (ETDRS) subfields, including central subfield (CSF), were analyzed. Statistical analyses were carried out using the analysis of variance. Overall, the mean CPT was 227.3 +/- 23.2 microm, and mean CSF was 270.2 +/- 22.5 microm. Among the ETDRS subfields, the outer nasal quadrant had the maximum thickness (mean +/- standard deviation, 339.5 +/- 16.9 microm). The RT did not show significant difference with age (P = .62) or with gender (P = .1). However, there was a suggestion of significant difference in RT of Black subjects as compared with White subjects (P = .007) in the present study. Normative values for macular thickness in otherwise healthy eyes were measured to be 227.3 microm (CPT) and 270.2 microm (CSF) using commercially available Spectralis SD-OCT. Based on the data, the present study proposes the guidelines for normal CSF thickness to be 315 microm for future studies using macular thickness measurements with Spectralis SD-OCT (Heidelberg Engineering

  14. A Fiber-Optic System Generating Pulses of High Spectral Density

    Science.gov (United States)

    Abramov, A. S.; Zolotovskii, I. O.; Korobko, D. A.; Fotiadi, A. A.

    2018-03-01

    A cascade fiber-optic system that generates pulses of high spectral density by using the effect of nonlinear spectral compression is proposed. It is demonstrated that the shape of the pulse envelope substantially influences the degree of compression of its spectrum. In so doing, maximum compression is achieved for parabolic pulses. The cascade system includes an optical fiber exhibiting normal dispersion that decreases along the fiber length, thereby ensuring that the pulse envelope evolves toward a parabolic shape, along with diffraction gratings and a fiber spectral compressor. Based on computer simulation, we determined parameters of cascade elements leading to maximum spectral density of radiation originating from a subpicosecond laser pulse of medium energy.

  15. A domain decomposition method for pseudo-spectral electromagnetic simulations of plasmas

    International Nuclear Information System (INIS)

    Vay, Jean-Luc; Haber, Irving; Godfrey, Brendan B.

    2013-01-01

    Pseudo-spectral electromagnetic solvers (i.e. representing the fields in Fourier space) have extraordinary precision. In particular, Haber et al. presented in 1973 a pseudo-spectral solver that integrates analytically the solution over a finite time step, under the usual assumption that the source is constant over that time step. Yet, pseudo-spectral solvers have not been widely used, due in part to the difficulty for efficient parallelization owing to global communications associated with global FFTs on the entire computational domains. A method for the parallelization of electromagnetic pseudo-spectral solvers is proposed and tested on single electromagnetic pulses, and on Particle-In-Cell simulations of the wakefield formation in a laser plasma accelerator. The method takes advantage of the properties of the Discrete Fourier Transform, the linearity of Maxwell’s equations and the finite speed of light for limiting the communications of data within guard regions between neighboring computational domains. Although this requires a small approximation, test results show that no significant error is made on the test cases that have been presented. The proposed method opens the way to solvers combining the favorable parallel scaling of standard finite-difference methods with the accuracy advantages of pseudo-spectral methods

  16. Interferometric and nonlinear-optical spectral-imaging techniques for outer space and live cells

    Science.gov (United States)

    Itoh, Kazuyoshi

    2015-12-01

    Multidimensional signals such as the spectral images allow us to have deeper insights into the natures of objects. In this paper the spectral imaging techniques that are based on optical interferometry and nonlinear optics are presented. The interferometric imaging technique is based on the unified theory of Van Cittert-Zernike and Wiener-Khintchine theorems and allows us to retrieve a spectral image of an object in the far zone from the 3D spatial coherence function. The retrieval principle is explained using a very simple object. The promising applications to space interferometers for astronomy that are currently in progress will also be briefly touched on. An interesting extension of interferometric spectral imaging is a 3D and spectral imaging technique that records 4D information of objects where the 3D and spectral information is retrieved from the cross-spectral density function of optical field. The 3D imaging is realized via the numerical inverse propagation of the cross-spectral density. A few techniques suggested recently are introduced. The nonlinear optical technique that utilizes stimulated Raman scattering (SRS) for spectral imaging of biomedical targets is presented lastly. The strong signals of SRS permit us to get vibrational information of molecules in the live cell or tissue in real time. The vibrational information of unstained or unlabeled molecules is crucial especially for medical applications. The 3D information due to the optical nonlinearity is also the attractive feature of SRS spectral microscopy.

  17. Bidirectional soliton spectral tunneling effects in the regime of optical event horizon

    DEFF Research Database (Denmark)

    Gu, Jie; Guo, Hairun; Wang, Shaofei

    2015-01-01

    We study the cross-phase-modulation-induced soliton spectral shifting in the regime of the optical event horizon. The perturbed soliton to either red-shifting or blue-shifting is controllable, which could evoke bidirectional soliton spectral tunneling effects.......We study the cross-phase-modulation-induced soliton spectral shifting in the regime of the optical event horizon. The perturbed soliton to either red-shifting or blue-shifting is controllable, which could evoke bidirectional soliton spectral tunneling effects....

  18. Retinal ganglion cell complex changes using spectral domain optical coherence tomography in diabetic patients without retinopathy

    Directory of Open Access Journals (Sweden)

    Ahmed I. Hegazy

    2017-03-01

    Full Text Available AIM: To assess the ganglion cell complex (GCC thickness in diabetic eyes without retinopathy. METHODS: Two groups included 45 diabetic eyes without retinopathy and 21 non diabetic eyes. All subjects underwent full medical and ophthalmological history, full ophthalmological examination, measuring GCC thickness and central foveal thickness (CFT using the RTVue® spectral domain-optical coherence tomography (SD-OCT, and HbA1C level. RESULTS: GCC focal loss volume (FLV% was significantly more in diabetic eyes (22.2% below normal than normal eyes (P=0.024. No statistically significant difference was found between the diabetic group and the control group regarding GCC global loss volume (GLV% (P=0.160. CFT was positively correlated to the average, superior and inferior GCC (P=0.001, 0.000 and 0.001 respectively and negatively correlated to GLV% and FLV% (P=0.002 and 0.031 respectively in diabetic eyes. C/D ratio in diabetic eyes was negatively correlated to average, superior and inferior GCC (P=0.015, 0.007 and 0.017 respectively. The FLV% was negatively correlated to the refraction and level of HbA1c (P=0.019 and 0.013 respectively and positively correlated to the best corrected visual acuity (BCVA in logMAR in diabetic group (P=0.004. CONCLUSION: Significant GCC thinning in diabetes predates retinal vasculopathy, which is mainly focal rather than diffuse. It has no preference to either the superior or inferior halves of the macula. Increase of myopic error is significantly accompanied with increased focal GCC loss. GCC loss is accompanied with increased C/D ratio in diabetic eyes.

  19. Large scale 2D spectral compressed sensing in continuous domain

    KAUST Repository

    Cai, Jian-Feng

    2017-06-20

    We consider the problem of spectral compressed sensing in continuous domain, which aims to recover a 2-dimensional spectrally sparse signal from partially observed time samples. The signal is assumed to be a superposition of s complex sinusoids. We propose a semidefinite program for the 2D signal recovery problem. Our model is able to handle large scale 2D signals of size 500 × 500, whereas traditional approaches only handle signals of size around 20 × 20.

  20. Large scale 2D spectral compressed sensing in continuous domain

    KAUST Repository

    Cai, Jian-Feng; Xu, Weiyu; Yang, Yang

    2017-01-01

    We consider the problem of spectral compressed sensing in continuous domain, which aims to recover a 2-dimensional spectrally sparse signal from partially observed time samples. The signal is assumed to be a superposition of s complex sinusoids. We propose a semidefinite program for the 2D signal recovery problem. Our model is able to handle large scale 2D signals of size 500 × 500, whereas traditional approaches only handle signals of size around 20 × 20.

  1. Retinal nerve fiber layer thickness in normals measured by spectral domain OCT.

    Science.gov (United States)

    Bendschneider, Delia; Tornow, Ralf P; Horn, Folkert K; Laemmer, Robert; Roessler, Christopher W; Juenemann, Anselm G; Kruse, Friedrich E; Mardin, Christian Y

    2010-09-01

    To determine normal values for peripapillary retinal nerve fiber layer thickness (RNFL) measured by spectral domain Optical Coherence Tomography (SOCT) in healthy white adults and to examine the relationship of RNFL with age, gender, and clinical variables. The peripapillary RNFL of 170 healthy patients (96 males and 74 females, age 20 to 78 y) was imaged with a high-resolution SOCT (Spectralis HRA+OCT, Heidelberg Engineering) in an observational cross-sectional study. RNFL thickness was measured around the optic nerve head using 16 automatically averaged, consecutive circular B-scans with 3.4-mm diameter. The automatically segmented RNFL thickness was divided into 32 segments (11.25 degrees each). One randomly selected eye per subject entered the study. Mean RNFL thickness in the study population was 97.2 ± 9.7 μm. Mean RNFL thickness was significantly negatively correlated with age (r = -0.214, P = 0.005), mean RNFL decrease per decade was 1.90 μm. As age dependency was different in different segments, age-correction of RNFL values was made for all segments separately. Age-adjusted RNFL thickness showed a significant correlation with axial length (r = -0.391, P = 0.001) and with refractive error (r = 0.396, P<0.001), but not with disc size (r = 0.124). Normal RNFL results with SOCT are comparable to those reported with time-domain OCT. In accordance with the literature on other devices, RNFL thickness measured with SOCT was significantly correlated with age and axial length. For creating a normative database of SOCT RNFL values have to be age adjusted.

  2. Precision spectral manipulation: A demonstration using a coherent optical memory

    Energy Technology Data Exchange (ETDEWEB)

    Sparkes, B. M.; Cairns, C.; Hosseini, M.; Higginbottom, D.; Campbell, G. T.; Lam, P. K.; Buchler, B. C. [Centre for Quantum Computation and Communication Technology, The Australian National University, Canberra (Australia)

    2014-12-04

    The ability to coherently spectrally manipulate quantum information has the potential to improve qubit rates across quantum channels and find applications in optical quantum computing. Here we present experiments that use a multi-element solenoid combined with the three-level gradient echo memory scheme to perform precision spectral manipulation of optical pulses. If applied in a quantum information network, these operations would enable frequency-based multiplexing of qubits.

  3. Volumetric three-dimensional reconstruction and segmentation of spectral-domain OCT.

    Science.gov (United States)

    Aaker, Grant D; Gracia, Luis; Myung, Jane S; Borcherding, Vanessa; Banfelder, Jason R; D'Amico, Donald J; Kiss, Szilárd

    2011-07-01

    Despite advances in optical coherence tomography (OCT), three-dimensional (3D) renderings of OCT images remain limited to scanning consecutive two-dimensional (2D) OCT slices. The authors describe a method of reconstructing 2D OCT data for 3D retinal analysis and visualization in a Computer Assisted Virtual Environment (CAVE). Using customized signal processing software, raw data from 2D slice-based spectral-domain OCT images were rendered into high-resolution 3D images for segmentation and quantification analysis. Reconstructed OCT images were projected onto a four-walled space and viewed through stereoscopic glasses, resulting in a virtual reality perception of the retina. These 3D retinal renderings offer a novel method for segmentation and isolation of volumetric images. The ability to manipulate the images in a virtual reality environment allows visualization of complex spatial relationships that may aid our understanding of retinal pathology. More importantly, these 3D retinal renderings can be viewed, manipulated, and analyzed on traditional 2D monitors independent of the CAVE. Copyright 2011, SLACK Incorporated.

  4. Heterodyne detection using spectral line pairing for spectral phase encoding optical code division multiple access and dynamic dispersion compensation.

    Science.gov (United States)

    Yang, Yi; Foster, Mark; Khurgin, Jacob B; Cooper, A Brinton

    2012-07-30

    A novel coherent optical code-division multiple access (OCDMA) scheme is proposed that uses spectral line pairing to generate signals suitable for heterodyne decoding. Both signal and local reference are transmitted via a single optical fiber and a simple balanced receiver performs sourceless heterodyne detection, canceling speckle noise and multiple-access interference (MAI). To validate the idea, a 16 user fully loaded phase encoded system is simulated. Effects of fiber dispersion on system performance are studied as well. Both second and third order dispersion management is achieved by using a spectral phase encoder to adjust phase shifts of spectral components at the optical network unit (ONU).

  5. Spectral tailoring of nanoscale EUV and soft x-ray multilayer optics

    Science.gov (United States)

    Huang, Qiushi; Medvedev, Viacheslav; van de Kruijs, Robbert; Yakshin, Andrey; Louis, Eric; Bijkerk, Fred

    2017-03-01

    Extreme ultraviolet and soft X-ray (XUV) multilayer optics have experienced significant development over the past few years, particularly on controlling the spectral characteristics of light for advanced applications like EUV photolithography, space observation, and accelerator- or lab-based XUV experiments. Both planar and three dimensional multilayer structures have been developed to tailor the spectral response in a wide wavelength range. For the planar multilayer optics, different layered schemes are explored. Stacks of periodic multilayers and capping layers are demonstrated to achieve multi-channel reflection or suppression of the reflective properties. Aperiodic multilayer structures enable broadband reflection both in angles and wavelengths, with the possibility of polarization control. The broad wavelength band multilayer is also used to shape attosecond pulses for the study of ultrafast phenomena. Narrowband multilayer monochromators are delivered to bridge the resolution gap between crystals and regular multilayers. High spectral purity multilayers with innovated anti-reflection structures are shown to select spectrally clean XUV radiation from broadband X-ray sources, especially the plasma sources for EUV lithography. Significant progress is also made in the three dimensional multilayer optics, i.e., combining micro- and nanostructures with multilayers, in order to provide new freedom to tune the spectral response. Several kinds of multilayer gratings, including multilayer coated gratings, sliced multilayer gratings, and lamellar multilayer gratings are being pursued for high resolution and high efficiency XUV spectrometers/monochromators, with their advantages and disadvantages, respectively. Multilayer diffraction optics are also developed for spectral purity enhancement. New structures like gratings, zone plates, and pyramids that obtain full suppression of the unwanted radiation and high XUV reflectance are reviewed. Based on the present achievement

  6. Optical signal processing for enabling high-speed, highly spectrally efficient and high capacity optical systems

    Science.gov (United States)

    Fazal, Muhammad Irfan

    The unabated demand for more capacity due to the ever-increasing internet traffic dictates that the boundaries of the state of the art maybe pushed to send more data through the network. Traditionally, this need has been satisfied by multiple wavelengths (wavelength division multiplexing), higher order modulation formats and coherent communication (either individually or combined together). WDM has the ability to reduce cost by using multiple channels within the same physical fiber, and with EDFA amplifiers, the need for O-E-O regenerators is eliminated. Moreover the availability of multiple colors allows for wavelength-based routing and network planning. Higher order modulation formats increases the capacity of the link by their ability to encode data in both the phase and amplitude of light, thereby increasing the bits/sec/Hz as compared to simple on-off keyed format. Coherent communications has also emerged as a primary means of transmitting and receiving optical data due to its support of formats that utilize both phase and amplitude to further increase the spectral efficiency of the optical channel, including quadrature amplitude modulation (QAM) and quadrature phase shift keying (QPSK). Polarization multiplexing of channels can double capacity by allowing two channels to share the same wavelength by propagating on orthogonal polarization axis and is easily supported in coherent systems where the polarization tracking can be performed in the digital domain. Furthermore, the forthcoming IEEE 100 Gbit/s Ethernet Standard, 802.3ba, provides greater bandwidth, higher data rates, and supports a mixture of modulation formats. In particular, Pol-MUX QPSK is increasingly becoming the industry's format of choice as the high spectral efficiency allows for 100 Gbit/s transmission while still occupying the current 50 GHz/channel allocation of current 10 Gbit/s OOK fiber systems. In this manner, 100 Gbit/s transfer speeds using current fiber links, amplifiers, and filters

  7. Multivendor Spectral-Domain Optical Coherence Tomography Dataset, Observer Annotation Performance Evaluation, and Standardized Evaluation Framework for Intraretinal Cystoid Fluid Segmentation

    Directory of Open Access Journals (Sweden)

    Jing Wu

    2016-01-01

    Full Text Available Development of image analysis and machine learning methods for segmentation of clinically significant pathology in retinal spectral-domain optical coherence tomography (SD-OCT, used in disease detection and prediction, is limited due to the availability of expertly annotated reference data. Retinal segmentation methods use datasets that either are not publicly available, come from only one device, or use different evaluation methodologies making them difficult to compare. Thus we present and evaluate a multiple expert annotated reference dataset for the problem of intraretinal cystoid fluid (IRF segmentation, a key indicator in exudative macular disease. In addition, a standardized framework for segmentation accuracy evaluation, applicable to other pathological structures, is presented. Integral to this work is the dataset used which must be fit for purpose for IRF segmentation algorithm training and testing. We describe here a multivendor dataset comprised of 30 scans. Each OCT scan for system training has been annotated by multiple graders using a proprietary system. Evaluation of the intergrader annotations shows a good correlation, thus making the reproducibly annotated scans suitable for the training and validation of image processing and machine learning based segmentation methods. The dataset will be made publicly available in the form of a segmentation Grand Challenge.

  8. Study of the spectral bandwidth of a double-pass acousto-optic system [Invited].

    Science.gov (United States)

    Champagne, Justine; Kastelik, Jean-Claude; Dupont, Samuel; Gazalet, Joseph

    2018-04-01

    Acousto-optic tunable filters are known as efficient instruments for spectral and spatial filtering of light. In this paper, we analyze the bandwidth dependence of a double-pass filter. The interaction geometry chosen allows the simultaneous diffraction of the ordinary and the extraordinary optical modes by a single ultrasonic frequency. We present the main parameters of a custom device (design, optical range, driving frequency) and experimental results concerning the angular deviation of the beams including the effect of optical birefringence. The spectral resolution and the side lobes' significance are discussed. Spectral bandwidth of such a system is analyzed.

  9. Retinal pigment epithelial changes in chronic Vogt-Koyanagi-Harada disease: fundus autofluorescence and spectral domain optical coherence tomography findings

    Science.gov (United States)

    Vasconcelos-Santos, Daniel V.; Sohn, Elliott H.; Sadda, Srinivas; Rao, Narsing A.

    2009-01-01

    Purpose To determine whether fundus autofluorescence (FAF) and spectral-domain optical coherence tomography (SD-OCT) imaging allows better assessment of RPE and outer retina (OR) in subjects with chronic VKH compared to examination and angiography alone. Methods Cross-sectional analysis of a series of seven consecutive patients with chronic VKH undergoing FAF and SD-OCT. Chronic VKH was defined as during >3 months. Color fundus photographs were correlated to FAF and SD-OCT images. The images were later correlated to fluorescein angiography (FA) and indocyanine green angiography (ICG-A). Results All patients had sunset glow fundus, which resulted in no apparent corresponding abnormality on FAF or SD-OCT. Lesions with decreased autofluorescence signal were observed in 11 eyes (85%), being associated with loss of the RPE and involvement of OR on SD-OCT. In 5 eyes (38%) some of these lesions were very subtle on clinical examination but easily detected by FAF. Lesions with increased autofluorescence signal were seen in 8 eyes (61.5%), showing variable involvement of the OR on SD-OCT and corresponding clinically to areas of RPE proliferation and cystoid macular edema. Conclusion Combined use of FAF and SD-OCT imaging allowed noninvasive delineation of RPE/OR changes in patients with chronic VKH, which were consistent with previous histopathological reports. Some of these changes were not apparent on clinical examination. PMID:20010321

  10. Long ranging swept-source optical coherence tomography-based angiography outperforms its spectral-domain counterpart in imaging human skin microcirculations

    Science.gov (United States)

    Xu, Jingjiang; Song, Shaozhen; Men, Shaojie; Wang, Ruikang K.

    2017-11-01

    There is an increasing demand for imaging tools in clinical dermatology that can perform in vivo wide-field morphological and functional examination from surface to deep tissue regions at various skin sites of the human body. The conventional spectral-domain optical coherence tomography-based angiography (SD-OCTA) system is difficult to meet these requirements due to its fundamental limitations of the sensitivity roll-off, imaging range as well as imaging speed. To mitigate these issues, we demonstrate a swept-source OCTA (SS-OCTA) system by employing a swept source based on a vertical cavity surface-emitting laser. A series of comparisons between SS-OCTA and SD-OCTA are conducted. Benefiting from the high system sensitivity, long imaging range, and superior roll-off performance, the SS-OCTA system is demonstrated with better performance in imaging human skin than the SD-OCTA system. We show that the SS-OCTA permits remarkable deep visualization of both structure and vasculature (up to ˜2 mm penetration) with wide field of view capability (up to 18×18 mm2), enabling a more comprehensive assessment of the morphological features as well as functional blood vessel networks from the superficial epidermal to deep dermal layers. It is expected that the advantages of the SS-OCTA system will provide a ground for clinical translation, benefiting the existing dermatological practice.

  11. Fundus autofluorescence and optical coherence tomography findings in thiamine responsive megaloblastic anemia.

    Science.gov (United States)

    Ach, Thomas; Kardorff, Rüdiger; Rohrschneider, Klaus

    2015-01-01

    To report ophthalmologic fundus autofluorescence and spectral domain optical coherence tomography findings in a patient with thiamine responsive megaloblastic anemia (TRMA). A 13-year-old girl with genetically proven TRMA was ophthalmologically (visual acuity, funduscopy, perimetry, electroretinogram) followed up over >5 years. Fundus imaging also included autofluorescence and spectral domain optical coherence tomography. During a 5-year follow-up, visual acuity and visual field decreased, despite a special TRMA diet. Funduscopy revealed bull's eye appearance, whereas fundus autofluorescence showed central and peripheral hyperfluorescence and perifoveal hypofluorescence. Spectral domain optical coherence tomography revealed affected inner segment ellipsoid band and irregularities in the retinal pigment epithelium and choroidea. Autofluorescence and spectral domain optical coherence tomography findings in a patient with TRMA show retinitis pigmentosa-like retina, retinal pigment epithelium, and choroid alterations. These findings might progress even under special TRMA diet, indispensable to life. Ophthalmologist should consider TRMA in patients with deafness and ophthalmologic disorders.

  12. All-optical signal processing of OTDM and OFDM signals based on time-domain Optical Fourier Transformation

    DEFF Research Database (Denmark)

    Clausen, Anders; Guan, Pengyu; Mulvad, Hans Christian Hansen

    2014-01-01

    All-optical time-domain Optical Fourier Transformation utilised for signal processing of ultra-high-speed OTDM signals and OFDM signals will be presented.......All-optical time-domain Optical Fourier Transformation utilised for signal processing of ultra-high-speed OTDM signals and OFDM signals will be presented....

  13. Mapping of landfills using time-domain spectral induced polarization data

    DEFF Research Database (Denmark)

    Gazoty, Aurélie; Fiandaca, Gianluca; Pedersen, Jesper Bjergsted

    2012-01-01

    This study uses time-domain induced polarization data for the delineation and characterization of the former landfill site at Eskelund, Denmark. With optimized acquisition parameters combined with a new inversion algorithm, we use the full content of the decay curve and retrieve spectral informat......This study uses time-domain induced polarization data for the delineation and characterization of the former landfill site at Eskelund, Denmark. With optimized acquisition parameters combined with a new inversion algorithm, we use the full content of the decay curve and retrieve spectral...... information from time-domain IP data. Thirteen IP/DC profiles were collected in the area, supplemented by el-log drilling for accurate correlation between the geophysics and the lithology. The data were inverted using a laterally constrained 1D inversion considering the full decay curves to retrieve the four......-log measurements giving in situ values, for which the Cole-Cole parameters were computed. The 3D shape of the waste body was pinpointed and well-defined. The inversion of the IP data also shows a strong correlation with the initial stage of the waste dump and its composition combining an aerial map with acquired...

  14. Spectral resolution control of acousto-optical cells operating with collimated and divergent beams

    Science.gov (United States)

    Voloshinov, Vitaly B.; Mishin, Dimitry D.

    1994-01-01

    The paper is devoted to theoretical and experimental investigations of acousto-optical interactions in crystals which may be used for spectral filtration of light in tunable acousto- optical filters. Attention is paid to spectral resolution control during operation with divergent or collimated noncoherent optical beams. In all examined cases spectral bands of anisotropic Bragg diffraction were regulated by means of novel electronical methods. Resolution control was achieved in paratellurite cells with non-collinear and quasi-collinear regimes of the diffraction. Filtration spectral bandwidths for visible light were electronically changed by a factor of 10 divided by 20 by drive electrical signals switching and drive electrical power regulations.

  15. Multichannel spectral mode of the ALOHA up-conversion interferometer

    Science.gov (United States)

    Lehmann, L.; Darré, P.; Boulogne, H.; Delage, L.; Grossard, L.; Reynaud, F.

    2018-06-01

    In this paper, we propose a multichannel spectral configuration of the Astronomical Light Optical Hybrid Analysis (ALOHA) instrument dedicated to high-resolution imaging. A frequency conversion process is implemented in each arm of an interferometer to transfer the astronomical light to a shorter wavelength domain. Exploiting the spectral selectivity of this non-linear optical process, we propose to use a set of independent pump lasers in order to simultaneously study multiple spectral channels. This principle is experimentally demonstrated with a dual-channel configuration as a proof-of-principle.

  16. Dental optical coherence domain reflectometry explorer

    Energy Technology Data Exchange (ETDEWEB)

    Everett, Matthew J. (Livermore, CA); Colston, Jr., Billy W. (Livermore, CA); Sathyam, Ujwal S. (Livermore, CA); Da Silva, Luiz B. (Pleasanton, CA)

    2001-01-01

    A hand-held, fiber optic based dental device with optical coherence domain reflectometry (OCDR) sensing capabilities provides a profile of optical scattering as a function of depth in the tissue at the point where the tip of the dental explorer touches the tissue. This system provides information on the internal structure of the dental tissue, which is then used to detect caries and periodontal disease. A series of profiles of optical scattering or tissue microstructure are generated by moving the explorer across the tooth or other tissue. The profiles are combined to form a cross-sectional, or optical coherence tomography (OCT), image.

  17. Impact of spectral nudging and domain size in studies of RCM response to parameter modification

    Energy Technology Data Exchange (ETDEWEB)

    Separovic, Leo; Laprise, Rene [Universite du Quebec a Montreal, Centre pour l' Etude et la Simulation du Climat a l' Echelle Regionale (ESCER), Montreal, QC (Canada); Universite du Quebec a Montreal (UQAM), Montreal, QC (Canada); Elia, Ramon de [Universite du Quebec a Montreal, Centre pour l' Etude et la Simulation du Climat a l' Echelle Regionale (ESCER), Montreal, QC (Canada); Consortium Ouranos, Montreal, QC (Canada)

    2012-04-15

    The paper aims at finding an RCM configuration that facilitates studies devoted to quantifying RCM response to parameter modification. When using short integration times, the response of the time-averaged variables to RCM modification tend to be blurred by the noise originating in the lack of predictability of the instantaneous atmospheric states. Two ways of enhancing the signal-to-noise ratio are studied in this work: spectral nudging and reduction of the computational domain size. The approach followed consists in the analysis of the sensitivity of RCM-simulated seasonal averages to perturbations of two parameters controlling deep convection and stratiform condensation, perturbed one at a time. Sensitivity is analyzed within different simulation configurations obtained by varying domain size and using the spectral nudging option. For each combination of these factors multiple members of identical simulations that differ exclusively in initial conditions are also generated to provide robust estimates of the sensitivities (the signal) and sample the noise. Results show that the noise magnitude is decreased both by reduction of domain size and the spectral nudging. However, the reduction of domain size alters some sensitivity signals. When spectral nudging is used significant alterations of the signal are not found. (orig.)

  18. All-optical OFDM demultiplexing by spectral magnification and band-pass filtering

    DEFF Research Database (Denmark)

    Palushani, Evarist; Mulvad, Hans Christian Hansen; Kong, Deming

    2014-01-01

    We propose a simple OFDM receiver allowing for the use of standard WDM receivers to receive spectrally advanced OFDM signals. We propose to spectrally magnify the optical-OFDM super-channels using a spectral telescope consisting of two time-lenses, which enables reduced inter-carrier-interference...

  19. Precision Spectral Manipulation: A Demonstration Using a Coherent Optical Memory

    Directory of Open Access Journals (Sweden)

    B. M. Sparkes

    2012-06-01

    Full Text Available The ability to coherently spectrally manipulate quantum information has the potential to improve qubit rates across quantum channels and find applications in optical quantum computing. In this paper, we present experiments that use a multielement solenoid combined with the three-level gradient echo memory scheme to perform precision spectral manipulation of optical pulses. These operations include separate bandwidth and frequency manipulation with precision down to tens of kHz, spectral filtering of up to three separate frequency components, as well as time-delayed interference between pulses with both the same, and different, frequencies. If applied in a quantum information network, these operations would enable frequency-based multiplexing of qubits.

  20. Optical network scaling: roles of spectral and spatial aggregation.

    Science.gov (United States)

    Arık, Sercan Ö; Ho, Keang-Po; Kahn, Joseph M

    2014-12-01

    As the bit rates of routed data streams exceed the throughput of single wavelength-division multiplexing channels, spectral and spatial traffic aggregation become essential for optical network scaling. These aggregation techniques reduce network routing complexity by increasing spectral efficiency to decrease the number of fibers, and by increasing switching granularity to decrease the number of switching components. Spectral aggregation yields a modest decrease in the number of fibers but a substantial decrease in the number of switching components. Spatial aggregation yields a substantial decrease in both the number of fibers and the number of switching components. To quantify routing complexity reduction, we analyze the number of multi-cast and wavelength-selective switches required in a colorless, directionless and contentionless reconfigurable optical add-drop multiplexer architecture. Traffic aggregation has two potential drawbacks: reduced routing power and increased switching component size.

  1. Spectral and kinetic analysis of radiation induced optical attenuation in silica: towards intrinsic fibre optic dosimetry?

    International Nuclear Information System (INIS)

    Borgermans, P.

    2002-01-01

    The document is an abstract of a PhD thesis. The PhD work concerns the detailed investigation of the behaviour of optical fibres in radiation fields such as is the case for various nuclear and space application,s. The core of the work concerns the spectral and kinetic analysis of the radiation induced optical attenuation. Models describing underlying physical phenomena, both for the spectral and the time dimensions, have been developed. The potential of silica optical fibre waveguides for intrinsic dosimetry has been assessed by employing specific properties of radiation induced defects in the silica waveguide material

  2. High-Speed Microscale Optical Tracking Using Digital Frequency-Domain Multiplexing.

    Science.gov (United States)

    Maclachlan, Robert A; Riviere, Cameron N

    2009-06-01

    Position-sensitive detectors (PSDs), or lateral-effect photodiodes, are commonly used for high-speed, high-resolution optical position measurement. This paper describes the instrument design for multidimensional position and orientation measurement based on the simultaneous position measurement of multiple modulated sources using frequency-domain-multiplexed (FDM) PSDs. The important advantages of this optical configuration in comparison with laser/mirror combinations are that it has a large angular measurement range and allows the use of a probe that is small in comparison with the measurement volume. We review PSD characteristics and quantitative resolution limits, consider the lock-in amplifier measurement system as a communication link, discuss the application of FDM to PSDs, and make comparisons with time-domain techniques. We consider the phase-sensitive detector as a multirate DSP problem, explore parallels with Fourier spectral estimation and filter banks, discuss how to choose the modulation frequencies and sample rates that maximize channel isolation under design constraints, and describe efficient digital implementation. We also discuss hardware design considerations, sensor calibration, probe construction and calibration, and 3-D measurement by triangulation using two sensors. As an example, we characterize the resolution, speed, and accuracy of an instrument that measures the position and orientation of a 10 mm × 5 mm probe in 5 degrees of freedom (DOF) over a 30-mm cube with 4-μm peak-to-peak resolution at 1-kHz sampling.

  3. Reducing BER of spectral-amplitude coding optical code-division multiple-access systems by single photodiode detection technique

    Science.gov (United States)

    Al-Khafaji, H. M. R.; Aljunid, S. A.; Amphawan, A.; Fadhil, H. A.; Safar, A. M.

    2013-03-01

    In this paper, we present a single photodiode detection (SPD) technique for spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA) systems. The proposed technique eliminates both phase-induced intensity noise (PIIN) and multiple-access interference (MAI) in the optical domain. Analytical results show that for 35 simultaneous users transmitting at data rate of 622 Mbps, the bit-error rate (BER) = 1.4x10^-28 for SPD technique is much better compared to 9.3x10^-6 and 9.6x10^-3 for the modified-AND as well as the AND detection techniques, respectively. Moreover, we verified the improved performance afforded by the proposed technique using data transmission simulations.

  4. Improved phase sensitivity in spectral domain phase microscopy using line-field illumination and self phase-referencing

    Science.gov (United States)

    Yaqoob, Zahid; Choi, Wonshik; Oh, Seungeun; Lue, Niyom; Park, Yongkeun; Fang-Yen, Christopher; Dasari, Ramachandra R.; Badizadegan, Kamran; Feld, Michael S.

    2010-01-01

    We report a quantitative phase microscope based on spectral domain optical coherence tomography and line-field illumination. The line illumination allows self phase-referencing method to reject common-mode phase noise. The quantitative phase microscope also features a separate reference arm, permitting the use of high numerical aperture (NA > 1) microscope objectives for high resolution phase measurement at multiple points along the line of illumination. We demonstrate that the path-length sensitivity of the instrument can be as good as 41 pm/Hz, which makes it suitable for nanometer scale study of cell motility. We present the detection of natural motions of cell surface and two-dimensional surface profiling of a HeLa cell. PMID:19550464

  5. Scanning laser polarimetry and spectral domain optical coherence tomography for the detection of retinal changes in Parkinson's disease.

    Science.gov (United States)

    Stemplewitz, Birthe; Keserü, Matthias; Bittersohl, Diana; Buhmann, Carsten; Skevas, Christos; Richard, Gisbert; Hassenstein, Andrea

    2015-12-01

    Whether retinal degeneration is part of the degenerative processes in patients with Parkinson's disease (PD) is still unclear. This cross-sectional study was undertaken to compare the retinal morphology of patients with PD and healthy controls using spectral domain optical coherence tomography (SD-OCT) and scanning laser polarimetry (SLP). Both eyes of patients with PD (n = 108) and healthy controls (n = 165) were examined using SD-OCT and SLP on the same day. Data on the thickness of the retinal nerve fibre layer (RNFL) of all quadrants and the macular area were acquired by OCT (Cirrus, Zeiss). The SLP device (Glaucoma diagnostics (GDx), Zeiss) measured the RNFL and calculated the nerve fibre index (NFI). All patients and probands were checked for concomitant ocular disorders by an ophthalmologist. Visual acuity, intraocular pressure (IOP), objective refraction and the anterior and posterior segment were assessed. Patients with PD showed a reduced macular volume and a reduced central subfield thickness in OCT examinations. The RNFL in the different quadrants did not differ significantly from that of controls. SLP data showed a reduced average RNFL thickness, a decreased thickness of the inferior quadrant and an increase of the NFI in patients with PD. PD may be associated with reduced thickness and volume of the macula and a reduced thickness of the RNFL in the inferior quadrant of the retina. Investigations using SD-OCT and SLP revealed distinct but significant differences between patients with PD and healthy controls. © 2015 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

  6. Spectral-domain optical coherence tomography analysis of persistent subretinal fluid after scleral buckling surgery for macula-off retinal detachment

    Science.gov (United States)

    Gharbiya, M; Malagola, R; Mariotti, C; Parisi, F; De Vico, U; Ganino, C; Grandinetti, F

    2015-01-01

    Purpose To determine the predictive value of markers for persistent subretinal fluid (SRF) absorption and the influence of subfoveal fluid on visual outcome after scleral buckle (SB) surgery for rhegmatogenous retinal detachment (RRD). Patients and methods This was a retrospective, observational study. We reviewed the medical records of 64 eyes of 64 patients who underwent SB surgery for macula-off RRD. Patients underwent clinical examination and spectral-domain optical coherence tomography before surgery, at 1 month and every 3 months postoperatively. The height and width of SRF bleb(s) were measured over time. Results Persistent SRF at 1 month was observed in 40 eyes (62.5%). SRF blebs were first detected 1.7±2.2 months postoperatively. In 29 cases that could be fully followed up, SRF blebs were completely absorbed 7.8±4.4 months postoperatively. Resolution of fluid was associated with an improvement of VA (P=0.003). Serial measurements of SRF bleb size showed that bleb width decreased significantly at all time points during the 12-month follow-up period (P0.05). The cut-off value of the bleb width-to-height ratio level for predicting bleb absorption at 6 months was 7, with 89% sensitivity and 83% specificity. Conclusions Visual improvement may occur with late resolution of residual subfoveal fluid. A bleb width-to-height ratio >7 indicates a higher risk of SRF to persist beyond 6 months after surgery. PMID:26139048

  7. Cross-Sectional Analysis of Neurocognitive Function, Retinopathy, and Retinal Thinning by Spectral-Domain Optical Coherence Tomography in Sickle Cell Patients.

    Science.gov (United States)

    Oltra, Erica Z; Chow, Clement C; Wubben, Thomas; Lim, Jennifer I; Chau, Felix Y; Moss, Heather E

    2016-01-01

    The purpose was to examine the relationship between neurocognitive function and two distinct forms of retinopathy in sickle cell disease. Patients with sickle cell disease (n = 44, age range: 19-56 years, 70% female) were prospectively recruited for this cross-sectional study. Retinopathy was characterized by: (1) Presence of focal retinal thinning on spectral domain optical coherence tomography and (2) determination of the sickle retinopathy stage on funduscopic exam based on Goldberg classification. Neurocognitive function was assessed using the Philadelphia Brief Assessment of Cognition (PBAC), a validated test of cognition. Univariate and multivariate analyses for PBAC score outcomes were performed. Retinal thinning and retinopathy stage were primary variables of interest and age, gender, genotype, education, and history of stroke were covariates. Univariate analysis revealed associations with total PBAC score and age (P = 0.049), history of stroke (P = 0.04), and genotype (P retinopathy stage were not associated with each other in this sample. Neither the presence of focal retinal thinning nor degree of retinopathy was associated with total PBAC score in univariate or multivariate analyses. We find an association between lower cognitive function and older age, history of stroke and sickle cell genotype SS in patients with sickle cell disease. Our data do not provide evidence to support an association between cognitive function and retinopathy in sickle cell patients.

  8. Introduction of Spectrally and Spatially Flexible Optical Networks

    DEFF Research Database (Denmark)

    Xia, Tiejun J.; Fevrier, Herve; Wang, Ting

    2015-01-01

    Given the introduction of coherent 100G systems has provided enough fiber capacity to meet data traffic growth in the near term, enhancing network efficiency will be service providers' high priority. Adding flexibility at the optical layer is a key step to increasing network efficiency, and both...... spectral and spatial functionality will be considered in next generation optical networks along with advanced network management to effectively harness the new capabilities....

  9. Automated detection of exudative age-related macular degeneration in spectral domain optical coherence tomography using deep learning.

    Science.gov (United States)

    Treder, Maximilian; Lauermann, Jost Lennart; Eter, Nicole

    2018-02-01

    Our purpose was to use deep learning for the automated detection of age-related macular degeneration (AMD) in spectral domain optical coherence tomography (SD-OCT). A total of 1112 cross-section SD-OCT images of patients with exudative AMD and a healthy control group were used for this study. In the first step, an open-source multi-layer deep convolutional neural network (DCNN), which was pretrained with 1.2 million images from ImageNet, was trained and validated with 1012 cross-section SD-OCT scans (AMD: 701; healthy: 311). During this procedure training accuracy, validation accuracy and cross-entropy were computed. The open-source deep learning framework TensorFlow™ (Google Inc., Mountain View, CA, USA) was used to accelerate the deep learning process. In the last step, a created DCNN classifier, using the information of the above mentioned deep learning process, was tested in detecting 100 untrained cross-section SD-OCT images (AMD: 50; healthy: 50). Therefore, an AMD testing score was computed: 0.98 or higher was presumed for AMD. After an iteration of 500 training steps, the training accuracy and validation accuracies were 100%, and the cross-entropy was 0.005. The average AMD scores were 0.997 ± 0.003 in the AMD testing group and 0.9203 ± 0.085 in the healthy comparison group. The difference between the two groups was highly significant (p deep learning-based approach using TensorFlow™, it is possible to detect AMD in SD-OCT with high sensitivity and specificity. With more image data, an expansion of this classifier for other macular diseases or further details in AMD is possible, suggesting an application for this model as a support in clinical decisions. Another possible future application would involve the individual prediction of the progress and success of therapy for different diseases by automatically detecting hidden image information.

  10. Spectral space-time coding for optical communications through a multimode fiber

    NARCIS (Netherlands)

    Alonso, A.; Berghmans, F.; Thienpont, H.; Danckaert, J.; Desmet, L.

    2001-01-01

    We propose a method for coding the mode structure of a multimode optical fiber by spectral coding mixed with space-time modulation. With this system we can improve the data carrying capacity of a multimode fiber for optical communications and optical interconnects, and encode and decode the

  11. Spectral analysis of point-vortex dynamics: first application to vortex polygons in a circular domain

    International Nuclear Information System (INIS)

    Speetjens, M F M; Meleshko, V V; Van Heijst, G J F

    2014-01-01

    The present study addresses the classical problem of the dynamics and stability of a cluster of N-point vortices of equal strength arranged in a polygonal configuration (‘N-vortex polygons’). In unbounded domains, such N-vortex polygons are unconditionally stable for N⩽7. Confinement in a circular domain tightens the stability conditions to N⩽6 and a maximum polygon size relative to the domain radius. This work expands on existing studies on stability and integrability by a first giving an exploratory spectral analysis of the dynamics of N vortex polygons in circular domains. Key to this is that the spectral signature of the time evolution of vortex positions reflects their qualitative behaviour. Expressing vortex motion by a generic evolution operator (the so-called Koopman operator) provides a rigorous framework for such spectral analyses. This paves the way to further differentiation and classification of point-vortex behaviour beyond stability and integrability. The concept of Koopman-based spectral analysis is demonstrated for N-vortex polygons. This reveals that conditional stability can be seen as a local form of integrability and confirms an important generic link between spectrum and dynamics: discrete spectra imply regular (quasi-periodic) motion; continuous (sub-)spectra imply chaotic motion. Moreover, this exposes rich nonlinear dynamics as intermittency between regular and chaotic motion and quasi-coherent structures formed by chaotic vortices. (ss 1)

  12. Spectral domain, common path OCT in a handheld PIC based system

    Science.gov (United States)

    Leinse, Arne; Wevers, Lennart; Marchenko, Denys; Dekker, Ronald; Heideman, René G.; Ruis, Roosje M.; Faber, Dirk J.; van Leeuwen, Ton G.; Kim, Keun Bae; Kim, Kyungmin

    2018-02-01

    Optical Coherence Tomography (OCT) has made it into the clinic in the last decade with systems based on bulk optical components. The next disruptive step will be the introduction of handheld OCT systems. Photonic Integrated Circuit (PIC) technology is the key enabler for this further miniaturization. PIC technology allows signal processing on a stable platform and the implementation of a common path interferometer in that same platform creates a robust fully integrated OCT system with a flexible fiber probe. In this work the first PIC based handheld and integrated common path based spectral domain OCT system is described and demonstrated. The spectrometer in the system is based on an Arrayed Waveguide Grating (AWG) and fully integrated with the CCD and a fiber probe into a system operating at 850 nm. The AWG on the PIC creates a 512 channel spectrometer with a resolution of 0.22 nm enabling a high speed analysis of the full A-scan. The silicon nitride based proprietary waveguide technology (TriPleXTM) enables low loss complex photonic structures from the visible (405 nm) to IR (2350 nm) range, making it a unique candidate for OCT applications. Broadband AWG operation from visible to 1700 nm has been shown in the platform and Photonic Design Kits (PDK) are available enabling custom made designs in a system level design environment. This allows a low threshold entry for designing new (OCT) designs for a broad wavelength range.

  13. Spectrally and Energy Efficient OFDM (SEE-OFDM) for Intensity Modulated Optical Wireless Systems

    OpenAIRE

    Lam, Emily; Wilson, Sarah Kate; Elgala, Hany; Little, Thomas D. C.

    2015-01-01

    Spectrally and energy efficient orthogonal frequency division multiplexing (SEE-OFDM) is an optical OFDM technique based on combining multiple asymmetrically clipped optical OFDM (ACO-OFDM) signals into one OFDM signal. By summing different components together, SEE-OFDM can achieve the same spectral efficiency as DC-biased optical OFDM (DCO-OFDM) without an energy-inefficient DC-bias. This paper introduces multiple methods for decoding a SEE-OFDM symbol and shows that an iterative decoder wit...

  14. Group velocity measurement using spectral interference in near-field scanning optical microscopy

    International Nuclear Information System (INIS)

    Mills, John D.; Chaipiboonwong, Tipsuda; Brocklesby, William S.; Charlton, Martin D. B.; Netti, Caterina; Zoorob, Majd E.; Baumberg, Jeremy J.

    2006-01-01

    Near-field scanning optical microscopy provides a tool for studying the behavior of optical fields inside waveguides. In this experiment the authors measure directly the variation of group velocity between different modes of a planar slab waveguide as the modes propagate along the guide. The measurement is made using the spectral interference between pulses propagating inside the waveguide with different group velocities, collected using a near-field scanning optical microscope at different points down the guide and spectrally resolved. The results are compared to models of group velocities in simple guides

  15. Retinal pigment epithelial changes in chronic Vogt-Koyanagi-Harada disease: fundus autofluorescence and spectral domain-optical coherence tomography findings.

    Science.gov (United States)

    Vasconcelos-Santos, Daniel V; Sohn, Elliott H; Sadda, Srinivas; Rao, Narsing A

    2010-01-01

    The purpose of this study was to determine whether fundus autofluorescence (FAF) and spectral domain-optical coherence tomography (SD-OCT) imaging allow better assessment of retinal pigment epithelium and the outer retina in subjects with chronic Vogt-Koyanagi-Harada disease compared with examination and angiography alone. A cross-sectional analysis of a series of seven consecutive patients with chronic Vogt-Koyanagi-Harada disease undergoing FAF and SD-OCT was conducted. Chronic disease was defined as duration of intraocular inflammation >3 months. Color fundus photographs were correlated to FAF and SD-OCT images. The images were later correlated to fluorescein angiography and indocyanine green angiography. All patients had sunset glow fundus, which resulted in no apparent corresponding abnormality on FAF or SD-OCT. Lesions with decreased autofluorescence signal were observed in 11 eyes (85%), being associated with loss of the retinal pigment epithelium and involvement of the outer retina on SD-OCT. In 5 eyes (38%), some of these lesions were very subtle on clinical examination but easily detected by FAF. Lesions with increased autofluorescence signal were seen in 8 eyes (61.5%), showing variable involvement of the outer retina on SD-OCT and corresponding clinically to areas of retinal pigment epithelium proliferation and cystoid macular edema. Combined use of FAF and SD-OCT imaging allowed noninvasive delineation of retinal pigment epithelium/outer retina changes in patients with chronic Vogt-Koyanagi-Harada disease, which were consistent with previous histopathologic reports. Some of these changes were not apparent on clinical examination.

  16. Optical spectral weight anomalies and strong correlation

    International Nuclear Information System (INIS)

    Toschi, A.; Capone, M.; Ortolani, M.; Calvani, P.; Lupi, S.; Castellani, C.

    2007-01-01

    The anomalous behavior observed in the optical spectral weight (W) of the cuprates provides valuable information about the physics of these compounds. Both the doping and the temperature dependences of W are hardly explained through conventional estimates based on the f-sum rule. By computing the optical conductivity of the doped Hubbard model with the Dynamical Mean Field Theory, we point out that the strong correlation plays a key role in determining the basic features of the observed anomalies: the proximity to a Mott insulating phase accounts simultaneously for the strong temperature dependence of W and for its zero temperature value

  17. Fundus Autofluorescence and Spectral Domain OCT in Central Serous Chorioretinopathy

    Directory of Open Access Journals (Sweden)

    Luiz Roisman

    2011-01-01

    Full Text Available Background. To describe the standard autofluorescence (FAF, the near infrared autofluorescence (NIA and optical coherence tomography (OCT patterns in central serous chorioretinopathy, correlating them with fluorescein angiography. Methods. Cross-sectional observational study, in which patients with at least seven months of CSC underwent ophthalmologic examination, fundus photography, FAF, NIA, fluorescein angiography (FA, and spectral-domain OCT. Results. Seventeen eyes of thirteen patients were included. The presentation features were a mottled hyperFAF in the detached area and areas with pigment mottling. NIA images showed areas of hyperNIA similar to FAF and localized areas of hypoNIA, which correlated with the points of leakage in the FA. OCT showed pigment epithelium detachment at the location of these hypoNIA spots. Discussion. FAF showed increased presence of fluorophores in the area of retinal detachment, which is believed to appear secondary to lipofuscin accumulation in the RPE or the presence of debris in the subretinal fluid. NIA has been related to the choroidal melanin content and there were areas of both increased and decreased NIA, which could be explained by damage ahead the retina, basically RPE and choroid. These findings, along with the PEDs found in the areas of hypoNIA, support the notion of a primary choroidal disease in CSC.

  18. Microresonator-Based Optical Frequency Combs: A Time Domain Perspective

    Science.gov (United States)

    2016-04-19

    AFRL-AFOSR-VA-TR-2016-0165 (BRI) Microresonator-Based Optical Frequency Combs: A Time Domain Perspective Andrew Weiner PURDUE UNIVERSITY 401 SOUTH...Optical Frequency Combs: A Time Domain Perspective 5a. CONTRACT NUMBER 5b. GRANT NUMBER FA9550-12-1-0236 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S...average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data

  19. Digital nonlinearity compensation in high-capacity optical communication systems considering signal spectral broadening effect.

    Science.gov (United States)

    Xu, Tianhua; Karanov, Boris; Shevchenko, Nikita A; Lavery, Domaniç; Liga, Gabriele; Killey, Robert I; Bayvel, Polina

    2017-10-11

    Nyquist-spaced transmission and digital signal processing have proved effective in maximising the spectral efficiency and reach of optical communication systems. In these systems, Kerr nonlinearity determines the performance limits, and leads to spectral broadening of the signals propagating in the fibre. Although digital nonlinearity compensation was validated to be promising for mitigating Kerr nonlinearities, the impact of spectral broadening on nonlinearity compensation has never been quantified. In this paper, the performance of multi-channel digital back-propagation (MC-DBP) for compensating fibre nonlinearities in Nyquist-spaced optical communication systems is investigated, when the effect of signal spectral broadening is considered. It is found that accounting for the spectral broadening effect is crucial for achieving the best performance of DBP in both single-channel and multi-channel communication systems, independent of modulation formats used. For multi-channel systems, the degradation of DBP performance due to neglecting the spectral broadening effect in the compensation is more significant for outer channels. Our work also quantified the minimum bandwidths of optical receivers and signal processing devices to ensure the optimal compensation of deterministic nonlinear distortions.

  20. Quantitative Characteristics of Spectral-Domain Optical Coherence Tomography in Corresponding Areas of Increased Autofluorescence at the Margin of Geographic Atrophy in Patients With Age-Related Macular Degeneration.

    Science.gov (United States)

    Hariri, Amir H; Nittala, Muneeswar G; Sadda, SriniVas R

    2016-06-01

    To evaluate the spectral-domain optical coherence tomography (SD-OCT) characteristics of the junctional zone corresponding to areas of increased autofluorescence (IAF) at the margin of geographic atrophy (GA) in patients with age-related macular degeneration (AMD). SD-OCT and fundus autofluorescence (FAF) images from untreated eyes with GA available from archived studies at Doheny Image Reading Center were evaluated. Areas of definite decreased autofluorescence (DDAF) corresponding to GA, and areas of IAF at the margins of the GA were manually segmented. Eyes with evidence of IAF were selected. Following manual registration of FAF and OCT data, areas of IAF and normal fluorescence were correlated with OCT features at these locations. Thirty eyes were included. The mean retinal pigment epithelium (RPE) thickness in areas of IAF was 40.6 µm ± 7.69 µm, compared to 28.8 µm ± 7.09 µm in normal adjacent areas (P Retina. 2016;47:523-527.]. Copyright 2016, SLACK Incorporated.

  1. Frequency interleaving towards spectrally efficient directly detected optical OFDM for next-generation optical access networks.

    Science.gov (United States)

    Mehedy, Lenin; Bakaul, Masuduzzaman; Nirmalathas, Ampalavanapillai

    2010-10-25

    In this paper, we theoretically analyze and demonstrate that spectral efficiency of a conventional direct detection based optical OFDM system (DDO-OFDM) can be improved significantly using frequency interleaving of adjacent DDO-OFDM channels where OFDM signal band of one channel occupies the spectral gap of other channel and vice versa. We show that, at optimum operating condition, the proposed technique can effectively improve the spectral efficiency of the conventional DDO-OFDM system as much as 50%. We also show that such a frequency interleaved DDO-OFDM system, with a bit rate of 48 Gb/s within 25 GHz bandwidth, achieves sufficient power budget after transmission over 25 km single mode fiber to be used in next-generation time-division-multiplexed passive optical networks (TDM-PON). Moreover, by applying 64- quadrature amplitude modulation (QAM), the system can be further scaled up to 96 Gb/s with a power budget sufficient for 1:16 split TDM-PON.

  2. Spectrally efficient polymer optical fiber transmission

    Science.gov (United States)

    Randel, Sebastian; Bunge, Christian-Alexander

    2011-01-01

    The step-index polymer optical fiber (SI-POF) is an attractive transmission medium for high speed communication links in automotive infotainment networks, in industrial automation, and in home networks. Growing demands for quality of service, e.g., for IPTV distribution in homes and for Ethernet based industrial control networks will necessitate Gigabit speeds in the near future. We present an overview on recent advances in the design of spectrally efficient and robust Gigabit-over-SI-POF transmission systems.

  3. Allocation of spectral and spatial modes in multidimensional metro-access optical networks

    Science.gov (United States)

    Gao, Wenbo; Cvijetic, Milorad

    2018-04-01

    Introduction of spatial division multiplexing (SDM) has added a new dimension in an effort to increase optical fiber channel capacity. At the same time, it can also be explored as an advanced optical networking tool. In this paper, we have investigated the resource allocation to end-users in multidimensional networking structure with plurality of spectral and spatial modes actively deployed in different networking segments. This presents a more comprehensive method as compared to the common practice where the segments of optical network are analyzed independently since the interaction between network hierarchies is included into consideration. We explored the possible transparency from the metro/core network to the optical access network, analyzed the potential bottlenecks from the network architecture perspective, and identified an optimized network structure. In our considerations, the viability of optical grooming through the entire hierarchical all-optical network is investigated by evaluating the effective utilization and spectral efficiency of the network architecture.

  4. Multi-spectral and fluorescence diffuse optical tomography of breast cancer

    Science.gov (United States)

    Corlu, Alper

    Multi-spectral and fluorescence diffuse optical tomography (DOT) techniques are explored and applied to image human breast cancer in vivo. Image reconstruction algorithms that utilize first and second order gradient information are described in detail. Breast DOT requires large computational memory and long run times. To this end, parallel computation techniques were developed appropriate to each reconstruction algorithm. A parallel plate DOT instrument developed for breast cancer imaging is described. The system relies heavily on continuous-wave (CW) transmission measurements and utilizes frequency domain (FD) measurements on the reemission side. However, traditional DOT image reconstruction methods based on CW measurements fail to separate tissue absorption and scattering uniquely. In this manuscript, multi-spectral DOT is shown to be capable of minimizing cross-talk and retrieving spectral parameters almost uniquely when the measurement wavelengths are optimized. A theoretical framework to select optimum wavelengths is provided, and tested with computer simulations. Results from phantom spectroscopy experiments and in vivo patient measurements support the notion that multi-spectral methods are superior to traditional DOT image reconstruction schemes. The same breast DOT instrument is improved and utilized to obtain the first in vivo images of human breast cancer based on fluorescence DOT (FDOT). To this end the fluorophore Indocyanine Green (ICG) is injected intravenously and fluorescence excitation and detection are accomplished in the soft-compression, parallel-plane, transmission geometry using laser sources at 786 nm and spectrally filtered CCD detection. Careful phantom and in vivo measurements are carried on to assure that the signals are due to ICG fluorescence, rather than tissue autofluorescence and excitation light leakage. An in vivo measurement protocol is designed to maximize the ICG contrast by acquiring full fluorescence tomographic scan during

  5. A multi-domain spectral method for time-fractional differential equations

    Science.gov (United States)

    Chen, Feng; Xu, Qinwu; Hesthaven, Jan S.

    2015-07-01

    This paper proposes an approach for high-order time integration within a multi-domain setting for time-fractional differential equations. Since the kernel is singular or nearly singular, two main difficulties arise after the domain decomposition: how to properly account for the history/memory part and how to perform the integration accurately. To address these issues, we propose a novel hybrid approach for the numerical integration based on the combination of three-term-recurrence relations of Jacobi polynomials and high-order Gauss quadrature. The different approximations used in the hybrid approach are justified theoretically and through numerical examples. Based on this, we propose a new multi-domain spectral method for high-order accurate time integrations and study its stability properties by identifying the method as a generalized linear method. Numerical experiments confirm hp-convergence for both time-fractional differential equations and time-fractional partial differential equations.

  6. Ganglion cell-inner plexiform layer and retinal nerve fibre layer changes within the macula in retinitis pigmentosa: a spectral domain optical coherence tomography study.

    Science.gov (United States)

    Yoon, Chang Ki; Yu, Hyeong Gon

    2018-03-01

    To investigate how macular ganglion cell-inner plexiform layer (GCIPL) and retinal nerve fibre layer (RNFL) thicknesses within the macula change with retinitis pigmentosa (RP) severity. Spectral domain optical coherence tomography (SD-OCT) was used to examine 177 patients with RP and 177 normal controls. An optical coherence tomography (OCT) line scan was used to grade RP severity. Retinitis pigmentosa (RP) was categorized as more advanced if there was no identifiable inner segment ellipsoid (ISe) band (NISE) and as less advanced if an ISe band could be identified and peripheral loss of ISe was apparent (IISE). Ganglion cell-inner plexiform layer (GCIPL) and RNFL thicknesses were manually measured on OCT images and analysed. Pearson's correlation analyses were used to examine correlations between GCIPL thickness, RNFL thickness, visual acuity (VA) and visual field extent in patients and controls. Ganglion cell-inner plexiform layer (GCIPL) was significantly thicker in IISE than in control eyes (p layer (RNFL) was significantly thicker in eyes with IISE and NISE than in control eyes in both horizontal and vertical meridians (all p layer (GCIPL) thickness showed a weak positive correlation with vision, and RNFL thickness showed a weak negative correlation with vision and visual field extent. Based on these results, the inner retina, including the GCIPL and RNFL, maintains its gross integrity longer than the photoreceptor layer in RP. Additionally, thickening of the inner retina may have some functional implications in patients with RP. © 2017 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

  7. Optical spectral signatures of liquids by means of fiber optic technology for product and quality parameter identification

    Science.gov (United States)

    Mignani, A. G.; Ciaccheri, L.; Mencaglia, A. A.; Diaz-Herrera, N.; Garcia-Allende, P. B.; Ottevaere, H.; Thienpont, H.; Attilio, C.; Cimato, A.; Francalanci, S.; Paccagnini, A.; Pavone, F. S.

    2009-01-01

    Absorption spectroscopy in the wide 200-1700 nm spectral range is carried out by means of optical fiber instrumentation to achieve a digital mapping of liquids for the prediction of important quality parameters. Extra virgin olive oils from Italy and lubricant oils from turbines with different degrees of degradation were considered as "case studies". The spectral data were processed by means of multivariate analysis so as to obtain a correlation to quality parameters. In practice, the wide range absorption spectra were considered as an optical signature of the liquids from which to extract product quality information. The optical signatures of extra virgin olive oils were used to predict the content of the most important fatty acids. The optical signatures of lubricant oils were used to predict the concentration of the most important parameters for indicating the oil's degree of degradation, such as TAN, JOAP anti-wear index, and water content.

  8. Time Lens based Optical Fourier Transformation for All-Optical Signal Processing of Spectrally-Efficient Data

    DEFF Research Database (Denmark)

    Guan, Pengyu; Røge, Kasper Meldgaard; Lillieholm, Mads

    2017-01-01

    We review recent progress in the use of time lens based optical Fourier transformation for advanced all-optical signal processing. A novel time lens based complete optical Fourier transformation (OFT) technique is introduced. This complete OFT is based on two quadratic phase-modulation stages using...... four-wave mixing (FWM), separated by a dispersive medium, which enables time-to-frequency and frequency-to-time conversions simultaneously, thus performing an exchange between the temporal and spectral profiles of the input signal. Using the proposed complete OFT, several advanced all-optical signal......, such as orthogonal frequency division multiplexing (OFDM), Nyquist wavelength-division multiplexing (Nyquist-WDM) and Nyquist optical time division multiplexing (Nyquist-OTDM) signals....

  9. Spectral-optical characteristics of anthocyanin-containing natural dye staff

    International Nuclear Information System (INIS)

    Astanov, S.; Sharipov, M.Z.; Dalmuradova, N.N.

    2007-01-01

    Spectral-optical characteristics of anthocyanin-containing natural dye staff received from fruit ficus carica are determined. The chromatographic separating of dyeing pigment obtained is performed. The data obtained can be used as passport characteristics of the new food dye staff. (authors)

  10. Comparison of optic area measurement using fundus photography and optical coherence tomography between optic nerve head drusen and control subjects.

    Science.gov (United States)

    Flores-Rodríguez, Patricia; Gili, Pablo; Martín-Ríos, María Dolores; Grifol-Clar, Eulalia

    2013-03-01

    To compare optic disc area measurement between optic nerve head drusen (ONHD) and control subjects using fundus photography, time-domain optical coherence tomography (TD-OCT) and spectral-domain optical coherence tomography (SD-OCT). We also made a comparison between each of the three techniques. We performed our study on 66 eyes (66 patients) with ONHD and 70 healthy control subjects (70 controls) with colour ocular fundus photography at 20º (Zeiss FF 450 IR plus), TD-OCT (Stratus OCT) with the Fast Optic Disc protocol and SD-OCT (Cirrus OCT) with the Optic Disc Cube 200 × 200 protocol for measurement of the optic disc area. The measurements were made by two observers and in each measurement a correction of the image magnification factor was performed. Measurement comparison using the Student's t-test/Mann-Whitney U test, the intraclass correlation coefficient, Pearson/Spearman rank correlation coefficient and the Bland-Altman plot was performed in the statistical analysis. Mean and standard deviation (SD) of the optic disc area in ONHD and in controls was 2.38 (0.54) mm(2) and 2.54 (0.42) mm(2), respectively with fundus photography; 2.01 (0.56) mm(2) and 1.66 (0.37) mm(2), respectively with TD-OCT, and 2.03 (0.49) mm(2) and 1.75 (0.38) mm(2), respectively with SD-OCT. In ONHD and controls, repeatability of optic disc area measurement was excellent with fundus photography and optical coherence tomography (TD-OCT and SD-OCT), but with a low degree of agreement between both techniques. Optic disc area measurement is smaller in ONHD compared to healthy subjects with fundus photography, unlike time-domain and spectral-domain optical coherence tomography in which the reverse is true. Both techniques offer good repeatability, but a low degree of correlation and agreement, which means that optic disc area measurement is not interchangeable or comparable between techniques. Ophthalmic & Physiological Optics © 2013 The College of Optometrists.

  11. Segmentation error and macular thickness measurements obtained with spectral-domain optical coherence tomography devices in neovascular age-related macular degeneration

    Directory of Open Access Journals (Sweden)

    Moosang Kim

    2013-01-01

    Full Text Available Purpose: To evaluate frequency and severity of segmentation errors of two spectral-domain optical coherence tomography (SD-OCT devices and error effect on central macular thickness (CMT measurements. Materials and Methods: Twenty-seven eyes of 25 patients with neovascular age-related macular degeneration, examined using the Cirrus HD-OCT and Spectralis HRA + OCT, were retrospectively reviewed. Macular cube 512 × 128 and 5-line raster scans were performed with the Cirrus and 512 × 25 volume scans with the Spectralis. Frequency and severity of segmentation errors were compared between scans. Results: Segmentation error frequency was 47.4% (baseline, 40.7% (1 month, 40.7% (2 months, and 48.1% (6 months for the Cirrus, and 59.3%, 62.2%, 57.8%, and 63.7%, respectively, for the Spectralis, differing significantly between devices at all examinations (P < 0.05, except at baseline. Average error score was 1.21 ± 1.65 (baseline, 0.79 ± 1.18 (1 month, 0.74 ± 1.12 (2 months, and 0.96 ± 1.11 (6 months for the Cirrus, and 1.73 ± 1.50, 1.54 ± 1.35, 1.38 ± 1.40, and 1.49 ± 1.30, respectively, for the Spectralis, differing significantly at 1 month and 2 months (P < 0.02. Automated and manual CMT measurements by the Spectralis were larger than those by the Cirrus. Conclusions: The Cirrus HD-OCT had a lower frequency and severity of segmentation error than the Spectralis HRA + OCT. SD-OCT error should be considered when evaluating retinal thickness.

  12. Automated retinal fovea type distinction in spectral-domain optical coherence tomography of retinal vein occlusion

    Science.gov (United States)

    Wu, Jing; Waldstein, Sebastian M.; Gerendas, Bianca S.; Langs, Georg; Simader, Christian; Schmidt-Erfurth, Ursula

    2015-03-01

    Spectral-domain Optical Coherence Tomography (SD-OCT) is a non-invasive modality for acquiring high- resolution, three-dimensional (3D) cross-sectional volumetric images of the retina and the subretinal layers. SD-OCT also allows the detailed imaging of retinal pathology, aiding clinicians in the diagnosis of sight degrading diseases such as age-related macular degeneration (AMD), glaucoma and retinal vein occlusion (RVO). Disease diagnosis, assessment, and treatment will require a patient to undergo multiple OCT scans, possibly using multiple scanners, to accurately and precisely gauge disease activity, progression and treatment success. However, cross-vendor imaging and patient movement may result in poor scan spatial correlation potentially leading to incorrect diagnosis or treatment analysis. The retinal fovea is the location of the highest visual acuity and is present in all patients, thus it is critical to vision and highly suitable for use as a primary landmark for cross-vendor/cross-patient registration for precise comparison of disease states. However, the location of the fovea in diseased eyes is extremely challenging to locate due to varying appearance and the presence of retinal layer destroying pathology. Thus categorising and detecting the fovea type is an important prior stage to automatically computing the fovea position. Presented here is an automated cross-vendor method for fovea distinction in 3D SD-OCT scans of patients suffering from RVO, categorising scans into three distinct types. OCT scans are preprocessed by motion correction and noise filing followed by segmentation using a kernel graph-cut approach. A statistically derived mask is applied to the resulting scan creating an ROI around the probable fovea location from which the uppermost retinal surface is delineated. For a normal appearance retina, minimisation to zero thickness is computed using the top two retinal surfaces. 3D local minima detection and layer thickness analysis are used

  13. SPECTRAL OPTICAL MONITORING OF THE NARROW-LINE SEYFERT 1 GALAXY Ark 564

    International Nuclear Information System (INIS)

    Shapovalova, A. I.; Burenkov, A. N.; Popović, L. Č.; Kovačević, J.; Chavushyan, V. H.; Valdes, J. R.; Torrealba, J.; Carrasco, L.; Ilić, D.; Kovačević, A.; Kollatschny, W.; Bochkarev, N. G.; León-Tavares, J.; Mercado, A.; Benítez, E.; Dultzin, D.; De la Fuente, E.

    2012-01-01

    We present the results of a long-term (1999-2010) spectral optical monitoring campaign of the active galactic nucleus (AGN) Ark 564, which shows a strong Fe II line emission in the optical. This AGN is a narrow-line Seyfert 1 (NLS1) galaxy, a group of AGNs with specific spectral characteristics. We analyze the light curves of the permitted Hα, Hβ, optical Fe II line fluxes, and the continuum flux in order to search for a time lag between them. Additionally, in order to estimate the contribution of iron lines from different multiplets, we fit the Hβ and Fe II lines with a sum of Gaussian components. We find that during the monitoring period the spectral variation (F max /F min ) of Ark 564 is between 1.5 for Hα and 1.8 for the Fe II lines. The correlation between the Fe II and Hβ flux variations is of higher significance than that of Hα and Hβ (whose correlation is almost absent). The permitted-line profiles are Lorentzian-like and do not change shape during the monitoring period. We investigate, in detail, the optical Fe II emission and find different degrees of correlation between the Fe II emission arising from different spectral multiplets and the continuum flux. The relatively weak and different degrees of correlations between permitted lines and continuum fluxes indicate a rather complex source of ionization of the broad-line emission region.

  14. SPECTRAL OPTICAL MONITORING OF THE NARROW-LINE SEYFERT 1 GALAXY Ark 564

    Energy Technology Data Exchange (ETDEWEB)

    Shapovalova, A. I.; Burenkov, A. N. [Special Astrophysical Observatory of the Russian AS, Nizhnij Arkhyz, Karachaevo-Cherkesia 369167 (Russian Federation); Popovic, L. C.; Kovacevic, J. [Astronomical Observatory, Volgina 7, 11160 Belgrade 74 (Serbia); Chavushyan, V. H.; Valdes, J. R.; Torrealba, J.; Carrasco, L. [Instituto Nacional de Astrofisica, Optica y Electronica, Apartado Postal 51-216, 72000 Puebla (Mexico); Ilic, D.; Kovacevic, A. [Isaac Newton Institute of Chile, Yugoslavia Branch, Belgrade (Serbia); Kollatschny, W. [Institut fuer Astrophysik, Georg-August-Universitaet, Goettingen (Germany); Bochkarev, N. G. [Sternberg Astronomical Institute, Moscow (Russian Federation); Leon-Tavares, J. [Aalto University Metsaehovi Radio Observatory, Metsaehovintie 114, FIN-02540 Kylmaelae (Finland); Mercado, A. [Universidad Politecnica de Baja California, Av. de la Industria 291, 21010 Mexicali, B.C. (Mexico); Benitez, E.; Dultzin, D. [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-264, Mexico, D.F. 04510 (Mexico); De la Fuente, E., E-mail: ashap@sao.ru [Instituto de Astronomia y Meteorologia, Dpto. de Fisica CUCEI, Universidad de Guadalajara, Av. Vallarta 2602, 44130 Guadalajara, Jalisco (Mexico)

    2012-09-15

    We present the results of a long-term (1999-2010) spectral optical monitoring campaign of the active galactic nucleus (AGN) Ark 564, which shows a strong Fe II line emission in the optical. This AGN is a narrow-line Seyfert 1 (NLS1) galaxy, a group of AGNs with specific spectral characteristics. We analyze the light curves of the permitted H{alpha}, H{beta}, optical Fe II line fluxes, and the continuum flux in order to search for a time lag between them. Additionally, in order to estimate the contribution of iron lines from different multiplets, we fit the H{beta} and Fe II lines with a sum of Gaussian components. We find that during the monitoring period the spectral variation (F{sub max}/F{sub min}) of Ark 564 is between 1.5 for H{alpha} and 1.8 for the Fe II lines. The correlation between the Fe II and H{beta} flux variations is of higher significance than that of H{alpha} and H{beta} (whose correlation is almost absent). The permitted-line profiles are Lorentzian-like and do not change shape during the monitoring period. We investigate, in detail, the optical Fe II emission and find different degrees of correlation between the Fe II emission arising from different spectral multiplets and the continuum flux. The relatively weak and different degrees of correlations between permitted lines and continuum fluxes indicate a rather complex source of ionization of the broad-line emission region.

  15. Time lens based optical fourier transformation for advanced processing of spectrally-efficient OFDM and N-WDM signals

    DEFF Research Database (Denmark)

    Guan, Pengyu; Røge, Kasper Meldgaard; Morioka, Toshio

    2016-01-01

    We review recent progress in the use of time lens based optical Fourier transformation for advanced optical signal processing, with focus on all-optical generation, detection and format conversion of spectrally-efficient OFDM and N-WDM signals.......We review recent progress in the use of time lens based optical Fourier transformation for advanced optical signal processing, with focus on all-optical generation, detection and format conversion of spectrally-efficient OFDM and N-WDM signals....

  16. Time-Domain Optical Fourier Transformation for OTDM-DWDM and DWDM-OTDM Conversion

    DEFF Research Database (Denmark)

    Mulvad, Hans Christian Hansen; Palushani, Evarist; Galili, Michael

    2011-01-01

    Applications of time-domain optical Fourier transformation (OFT) in ultra-high-speed optical time-division multiplexed systems (OTDM) are reviewed, with emphasis on the recent demonstrations of OFT-based conversion between the OTDM and DWDM formats.......Applications of time-domain optical Fourier transformation (OFT) in ultra-high-speed optical time-division multiplexed systems (OTDM) are reviewed, with emphasis on the recent demonstrations of OFT-based conversion between the OTDM and DWDM formats....

  17. Multi-spectral confocal microendoscope for in-vivo imaging

    Science.gov (United States)

    Rouse, Andrew Robert

    The concept of in-vivo multi-spectral confocal microscopy is introduced. A slit-scanning multi-spectral confocal microendoscope (MCME) was built to demonstrate the technique. The MCME employs a flexible fiber-optic catheter coupled to a custom built slit-scan confocal microscope fitted with a custom built imaging spectrometer. The catheter consists of a fiber-optic imaging bundle linked to a miniature objective and focus assembly. The design and performance of the miniature objective and focus assembly are discussed. The 3mm diameter catheter may be used on its own or routed though the instrument channel of a commercial endoscope. The confocal nature of the system provides optical sectioning with 3mum lateral resolution and 30mum axial resolution. The prism based multi-spectral detection assembly is typically configured to collect 30 spectral samples over the visible chromatic range. The spectral sampling rate varies from 4nm/pixel at 490nm to 8nm/pixel at 660nm and the minimum resolvable wavelength difference varies from 7nm to 18nm over the same spectral range. Each of these characteristics are primarily dictated by the dispersive power of the prism. The MCME is designed to examine cellular structures during optical biopsy and to exploit the diagnostic information contained within the spectral domain. The primary applications for the system include diagnosis of disease in the gastro-intestinal tract and female reproductive system. Recent data from the grayscale imaging mode are presented. Preliminary multi-spectral results from phantoms, cell cultures, and excised human tissue are presented to demonstrate the potential of in-vivo multi-spectral imaging.

  18. Extraction of optical parameters of thin films from spectral measurements for design and optical performance of multilayer structures

    International Nuclear Information System (INIS)

    Muellerova, J.; Jurecka, S.; Kucerova, A.

    2003-01-01

    Optical parameters of a-Si:H and indium tin oxide (ITO) thin films deposited on glass substrates are determined from spectral measurements of reflectance and/or transmittance. It is shown how important the exact knowledge of optical parameters as well as thicknesses of the layers for the design and the optical performance of multilayer structures is. The model of the p-i-n based a:Si-H solar cell with ITO as transparent conductive oxide layer is used for illustrating. The modeling of the solar cell integral reflectance in the spectral region of (650-830) nm is used as a criterion to reverse engineering of a multilayer structure with suppressed reflectance losses. The reflectance of a solar cell is modelled and the simulation of the varying optical parameters of individual layers including their thicknesses is discussed. Besides this,the advantage of using an antireflective layer under ITO is discussed (Authors)

  19. Optically transparent multiple access networks employing incoherent spectral codes

    NARCIS (Netherlands)

    Huiszoon, B.

    2008-01-01

    This Ph.D. thesis is divided into 7 chapters to provide the reader an overview of the main results achieved in di®erent sub-topics of the study towards optically transparent multiple access networks employing incoherent spectral codes taking into account wireless transmission aspects. The work

  20. Structure-function correlations in glaucoma using matrix and standard automated perimetry versus time-domain and spectral-domain OCT devices.

    Science.gov (United States)

    Pinto, Luciano Moreira; Costa, Elaine Fiod; Melo, Luiz Alberto S; Gross, Paula Blasco; Sato, Eduardo Toshio; Almeida, Andrea Pereira; Maia, Andre; Paranhos, Augusto

    2014-04-10

    We examined the structure-function relationship between two perimetric tests, the frequency doubling technology (FDT) matrix and standard automated perimetry (SAP), and two optical coherence tomography (OCT) devices (time-domain and spectral-domain). This cross-sectional study included 97 eyes from 29 healthy individuals, and 68 individuals with early, moderate, or advanced primary open-angle glaucoma. The correlations between overall and sectorial parameters of retinal nerve fiber layer thickness (RNFL) measured with Stratus and Spectralis OCT, and the visual field sensitivity obtained with FDT matrix and SAP were assessed. The relationship also was evaluated using a previously described linear model. The correlation coefficients for the threshold sensitivity measured with SAP and Stratus OCT ranged from 0.44 to 0.79, and those for Spectralis OCT ranged from 0.30 to 0.75. Regarding FDT matrix, the correlation ranged from 0.40 to 0.79 with Stratus OCT and from 0.39 to 0.79 with Spectralis OCT. Stronger correlations were found in the overall measurements and the arcuate sectors for both visual fields and OCT devices. A linear relationship was observed between FDT matrix sensitivity and the OCT devices. The previously described linear model fit the data from SAP and the OCT devices well, particularly in the inferotemporal sector. The FDT matrix and SAP visual sensitivities were related strongly to the RNFL thickness measured with the Stratus and Spectralis OCT devices, particularly in the overall and arcuate sectors. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.

  1. Semiautomated segmentation and analysis of retinal layers in three-dimensional spectral-domain optical coherence tomography images of patients with atrophic age-related macular degeneration.

    Science.gov (United States)

    Hu, Zhihong; Shi, Yue; Nandanan, Kiran; Sadda, Srinivas R

    2017-01-01

    Historically, regular drusen and geographic atrophy (GA) have been recognized as the hallmarks of nonneovascular age-related macular degeneration (AMD). Recent imaging developments have revealed another distinct nonneovascular AMD phenotype, reticular pseudodrusen (RPD). We develop an approach to semiautomatically quantify retinal surfaces associated with various AMD lesions (i.e., regular drusen, RPD, and GA) in spectral domain (SD) optical coherence tomography (OCT) images. More specifically, a graph-based algorithm was used to segment multiple retinal layers in SD-OCT volumes. Varying surface feasibility constraints based on the presegmentation were applied on the double-surface graph search to refine the surface segmentation. The thicknesses of these layers and their correlation with retinal functional measurements, including microperimetry (MP) sensitivity and visual acuity (VA), were investigated. The photoreceptor outer segment layer demonstrated significant thinning with a reduction in MP sensitivity and VA score when atrophic AMD lesions were present. Regular drusen and RPD were separately segmented on SD-OCT images to allow their characteristics and distribution to be studied separately. The mean thickness of regular drusen was found to significantly correlate with the VA score. RPD appeared to be distributed evenly throughout the macula and regular drusen appeared to be more concentrated centrally.

  2. Near-infrared spectral tomography integrated with digital breast tomosynthesis: Effects of tissue scattering on optical data acquisition design

    Energy Technology Data Exchange (ETDEWEB)

    Michaelsen, Kelly; Krishnaswamy, Venkat; Pogue, Brian W.; Poplack, Steven P.; Paulsen, Keith D. [Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755 (United States); Department of Diagnostic Radiology, Dartmouth Medical School, Lebanon, New Hampshire 03756 (United States); Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755 and Department of Diagnostic Radiology, Dartmouth Medical School, Lebanon, New Hampshire 03756 (United States)

    2012-07-15

    Purpose: Design optimization and phantom validation of an integrated digital breast tomosynthesis (DBT) and near-infrared spectral tomography (NIRST) system targeting improvement in sensitivity and specificity of breast cancer detection is presented. Factors affecting instrumentation design include minimization of cost, complexity, and examination time while maintaining high fidelity NIRST measurements with sufficient information to recover accurate optical property maps. Methods: Reconstructed DBT slices from eight patients with abnormal mammograms provided anatomical information for the NIRST simulations. A limited frequency domain (FD) and extensive continuous wave (CW) NIRST system was modeled. The FD components provided tissue scattering estimations used in the reconstruction of the CW data. Scattering estimates were perturbed to study the effects on hemoglobin recovery. Breast mimicking agar phantoms with inclusions were imaged using the combined DBT/NIRST system for comparison with simulation results. Results: Patient simulations derived from DBT images show successful reconstruction of both normal and malignant lesions in the breast. They also demonstrate the importance of accurately quantifying tissue scattering. Specifically, 20% errors in optical scattering resulted in 22.6% or 35.1% error in quantification of total hemoglobin concentrations, depending on whether scattering was over- or underestimated, respectively. Limited frequency-domain optical signal sampling provided two regions scattering estimates (for fat and fibroglandular tissues) that led to hemoglobin concentrations that reduced the error in the tumor region by 31% relative to when a single estimate of optical scattering was used throughout the breast volume of interest. Acquiring frequency-domain data with six wavelengths instead of three did not significantly improve the hemoglobin concentration estimates. Simulation results were confirmed through experiments in two-region breast mimicking

  3. Near-infrared spectral tomography integrated with digital breast tomosynthesis: Effects of tissue scattering on optical data acquisition design

    International Nuclear Information System (INIS)

    Michaelsen, Kelly; Krishnaswamy, Venkat; Pogue, Brian W.; Poplack, Steven P.; Paulsen, Keith D.

    2012-01-01

    Purpose: Design optimization and phantom validation of an integrated digital breast tomosynthesis (DBT) and near-infrared spectral tomography (NIRST) system targeting improvement in sensitivity and specificity of breast cancer detection is presented. Factors affecting instrumentation design include minimization of cost, complexity, and examination time while maintaining high fidelity NIRST measurements with sufficient information to recover accurate optical property maps. Methods: Reconstructed DBT slices from eight patients with abnormal mammograms provided anatomical information for the NIRST simulations. A limited frequency domain (FD) and extensive continuous wave (CW) NIRST system was modeled. The FD components provided tissue scattering estimations used in the reconstruction of the CW data. Scattering estimates were perturbed to study the effects on hemoglobin recovery. Breast mimicking agar phantoms with inclusions were imaged using the combined DBT/NIRST system for comparison with simulation results. Results: Patient simulations derived from DBT images show successful reconstruction of both normal and malignant lesions in the breast. They also demonstrate the importance of accurately quantifying tissue scattering. Specifically, 20% errors in optical scattering resulted in 22.6% or 35.1% error in quantification of total hemoglobin concentrations, depending on whether scattering was over- or underestimated, respectively. Limited frequency-domain optical signal sampling provided two regions scattering estimates (for fat and fibroglandular tissues) that led to hemoglobin concentrations that reduced the error in the tumor region by 31% relative to when a single estimate of optical scattering was used throughout the breast volume of interest. Acquiring frequency-domain data with six wavelengths instead of three did not significantly improve the hemoglobin concentration estimates. Simulation results were confirmed through experiments in two-region breast mimicking

  4. A pseudospectral collocation time-domain method for diffractive optics

    DEFF Research Database (Denmark)

    Dinesen, P.G.; Hesthaven, J.S.; Lynov, Jens-Peter

    2000-01-01

    We present a pseudospectral method for the analysis of diffractive optical elements. The method computes a direct time-domain solution of Maxwell's equations and is applied to solving wave propagation in 2D diffractive optical elements. (C) 2000 IMACS. Published by Elsevier Science B.V. All rights...

  5. Defining the spectral and amplitude domain of music---a window into audio

    Science.gov (United States)

    Nam, Myoung W.

    In terms of 'visualizing music', this thesis presents the first critical measurements for the selected musical instruments (piano, violin, cello, flute, piccolo, drums, double bass, electric bass, and electric guitar) seeking to describe their place in the spectral and amplitude domain. All data presented as a part of this research were measured with Z-weighting (un-weighted) from 12.5Hz to 20kHz along the frequency axis, in 1/3 octave bands, evaluated statistically and in equivalent sound level. Measuring musical performances can be a very subjective process. Therefore, this research proceeded under some strategically chosen conditions and limitations. The measurements were made with each musician playing at several different intensities of musical performance. Chosen musical genres were classical, pop and jazz for the selected musical instruments. To obtain data representative of real world conditions, musical instrument measurements were made mostly in professional recording studios by professional players. The results seek to define the spectral and amplitude domain occupied by these instruments when playing typical works.

  6. Research on the strong optical feedback effects based on spectral analysis method

    Science.gov (United States)

    Zeng, Zhaoli; Qu, XueMin; Li, Weina; Zhang, Min; Wang, Hao; Li, Tuo

    2018-01-01

    The strong optical feedback has the advantage of generating high resolution fringes. However, these feedback fringes usually seem like the noise signal when the feedback level is high. This defect severely limits its practical application. In this paper, the generation mechanism of noise fringes with strong optical feedback is studied by using spectral analysis method. The spectral analysis results show that, in most cases, the noise-like fringes are observed owing to the strong multiple high-order feedback. However, at certain feedback cavity condition, there may be only one high-order feedback beam goes back to the laser cavity, the noise-like fringes can change to the cosine-like fringes. And the resolution of this fringe is dozens times than that of the weak optical feedback. This research provides a method to obtain high resolution cosine-like fringes rather than noise signal in the strong optical feedback, which makes it possible to be used in nanoscale displacement measurements.

  7. Thin film optical coatings for the ultraviolet spectral region

    Science.gov (United States)

    Torchio, P.; Albrand, G.; Alvisi, M.; Amra, C.; Rauf, H.; Cousin, B.; Otrio, G.

    2017-11-01

    The applications and innovations related to the ultraviolet field are today in strong growth. To satisfy these developments which go from biomedical to the large equipment like the Storage Ring Free Electron Laser, it is crucial to control with an extreme precision the optical performances, in using the substrates and the thin film materials impossible to circumvent in this spectral range. In particular, the reduction of the losses by electromagnetic diffusion, Joule effect absorption, or the behavior under UV luminous flows of power, resistance to surrounding particulate flows... become top priority which concerns a broad European and international community. Our laboratory has the theoretical, experimental and technological tools to design and fabricate numerous multilayer coatings with desirable optical properties in the visible and infrared spectral ranges. We have extended our expertise to the ultraviolet. We present here some results on high reflectivity multidielectric mirrors towards 250 nm in wavelength, produced by Ion Plating Deposition. The latter technique allows us to obtain surface treatments with low absorption and high resistance. We give in this study the UV transparent materials and the manufacturing technology which have been the best suited to meet requirements. Single UV layers were deposited and characterized. HfO2/SiO2 mirrors with a reflectance higher than 99% at 300 nm were obtained. Optical and non-optical characterizations such as UV spectrophotometric measurements, X-Ray Diffraction spectra, Scanning Electron Microscope and Atomic Force Microscope images were performed

  8. Design of integrated optics all-optical label swappers for spectral amplitude code label swapping optical packet networks on active/passive InP technology

    NARCIS (Netherlands)

    Habib, C.; Munoz, P.; Leijtens, X.J.M.; Chen, Lawrence; Smit, M.K.; Capmany, J.

    2009-01-01

    In this paper the designs of optical label swapper devices, for spectral amplitude coded labels, monolithically integrated on InP active/passive technology are pre sented. The devices are based on cross-gain modulation in a semiconductor optical amplifier. Multi-wavelength operation is enabled by

  9. Discrimination of Temperature and Strain in Brillouin Optical Time Domain Analysis Using a Multicore Optical Fiber.

    Science.gov (United States)

    Zaghloul, Mohamed A S; Wang, Mohan; Milione, Giovanni; Li, Ming-Jun; Li, Shenping; Huang, Yue-Kai; Wang, Ting; Chen, Kevin P

    2018-04-12

    Brillouin optical time domain analysis is the sensing of temperature and strain changes along an optical fiber by measuring the frequency shift changes of Brillouin backscattering. Because frequency shift changes are a linear combination of temperature and strain changes, their discrimination is a challenge. Here, a multicore optical fiber that has two cores is fabricated. The differences between the cores' temperature and strain coefficients are such that temperature (strain) changes can be discriminated with error amplification factors of 4.57 °C/MHz (69.11 μ ϵ /MHz), which is 2.63 (3.67) times lower than previously demonstrated. As proof of principle, using the multicore optical fiber and a commercial Brillouin optical time domain analyzer, the temperature (strain) changes of a thermally expanding metal cylinder are discriminated with an error of 0.24% (3.7%).

  10. Discrimination of Temperature and Strain in Brillouin Optical Time Domain Analysis Using a Multicore Optical Fiber

    Directory of Open Access Journals (Sweden)

    Mohamed A. S. Zaghloul

    2018-04-01

    Full Text Available Brillouin optical time domain analysis is the sensing of temperature and strain changes along an optical fiber by measuring the frequency shift changes of Brillouin backscattering. Because frequency shift changes are a linear combination of temperature and strain changes, their discrimination is a challenge. Here, a multicore optical fiber that has two cores is fabricated. The differences between the cores’ temperature and strain coefficients are such that temperature (strain changes can be discriminated with error amplification factors of 4.57 °C/MHz (69.11 μ ϵ /MHz, which is 2.63 (3.67 times lower than previously demonstrated. As proof of principle, using the multicore optical fiber and a commercial Brillouin optical time domain analyzer, the temperature (strain changes of a thermally expanding metal cylinder are discriminated with an error of 0.24% (3.7%.

  11. High-resolution retinal imaging using adaptive optics and Fourier-domain optical coherence tomography

    Science.gov (United States)

    Olivier, Scot S.; Werner, John S.; Zawadzki, Robert J.; Laut, Sophie P.; Jones, Steven M.

    2010-09-07

    This invention permits retinal images to be acquired at high speed and with unprecedented resolution in three dimensions (4.times.4.times.6 .mu.m). The instrument achieves high lateral resolution by using adaptive optics to correct optical aberrations of the human eye in real time. High axial resolution and high speed are made possible by the use of Fourier-domain optical coherence tomography. Using this system, we have demonstrated the ability to image microscopic blood vessels and the cone photoreceptor mosaic.

  12. Optical decoherence times and spectral diffusion in an Er-doped optical fiber measured by two-pulse echoes, stimulated photon echoes, and spectral hole burning

    International Nuclear Information System (INIS)

    Macfarlane, R.M.; Sun, Y.; Sellin, P.B.; Cone, R.L.

    2007-01-01

    Two-pulse and stimulated photon echoes and spectral hole burning were measured on the transition from the lowest component of the 4 I 15/2 manifold to the lowest component of 4 I 13/2 of Er 3+ in a silicate optical fiber at 1.6 K. The two-pulse echo decays gave decoherence times as long as 230 ns for magnetic fields above 2 T. A large field dependent contribution to the homogeneous line width of >2 MHz was found and interpreted in terms of coupling to magnetic tunneling modes (TLS) in the glass. The stimulated echoes measured at 2 T showed spectral diffusion of 0.8 MHz/decade of time between 0.4 and 500 μs. Spectral diffusion in this high field region is attributed to coupling to elastic TLS modes which have a distribution of flip rates in glasses. Time-resolved spectral hole burning at very low field showed stronger spectral diffusion of 5.7 MHz/decade of time, attributed to coupling to magnetic spin-elastic TLS modes

  13. Spectral Optical Readout of Rectangular-Miniature Hollow Glass Tubing for Refractive Index Sensing.

    Science.gov (United States)

    Rigamonti, Giulia; Bello, Valentina; Merlo, Sabina

    2018-02-16

    For answering the growing demand of innovative micro-fluidic devices able to measure the refractive index of samples in extremely low volumes, this paper presents an overview of the performances of a micro-opto-fluidic sensing platform that employs rectangular, miniature hollow glass tubings. The operating principle is described by showing the analytical model of the tubing, obtained as superposition of different optical cavities, and the optical readout method based on spectral reflectivity detection. We have analyzed, in particular, the theoretical and experimental optical features of rectangular tubings with asymmetrical geometry, thus with channel depth larger than the thickness of the glass walls, though all of them in the range of a few tens of micrometers. The origins of the complex line-shape of the spectral response in reflection, due to the different cavities formed by the tubing flat walls and channel, have been investigated using a Fourier transform analysis. The implemented instrumental configuration, based on standard telecom fiberoptic components and a semiconductor broadband optical source emitting in the near infrared wavelength region centered at 1.55 µm, has allowed acquisition of reflectivity spectra for experimental verification of the expected theoretical behavior. We have achieved detection of refractive index variations related to the change of concentration of glucose-water solutions flowing through the tubing by monitoring the spectral shift of the optical resonances.

  14. Spectral Optical Readout of Rectangular–Miniature Hollow Glass Tubing for Refractive Index Sensing

    Science.gov (United States)

    Rigamonti, Giulia; Bello, Valentina

    2018-01-01

    For answering the growing demand of innovative micro-fluidic devices able to measure the refractive index of samples in extremely low volumes, this paper presents an overview of the performances of a micro-opto-fluidic sensing platform that employs rectangular, miniature hollow glass tubings. The operating principle is described by showing the analytical model of the tubing, obtained as superposition of different optical cavities, and the optical readout method based on spectral reflectivity detection. We have analyzed, in particular, the theoretical and experimental optical features of rectangular tubings with asymmetrical geometry, thus with channel depth larger than the thickness of the glass walls, though all of them in the range of a few tens of micrometers. The origins of the complex line-shape of the spectral response in reflection, due to the different cavities formed by the tubing flat walls and channel, have been investigated using a Fourier transform analysis. The implemented instrumental configuration, based on standard telecom fiberoptic components and a semiconductor broadband optical source emitting in the near infrared wavelength region centered at 1.55 µm, has allowed acquisition of reflectivity spectra for experimental verification of the expected theoretical behavior. We have achieved detection of refractive index variations related to the change of concentration of glucose-water solutions flowing through the tubing by monitoring the spectral shift of the optical resonances. PMID:29462907

  15. Distributed strain measurement in perfluorinated polymer optical fibres using optical frequency domain reflectometry

    International Nuclear Information System (INIS)

    Liehr, Sascha; Wendt, Mario; Krebber, Katerina

    2010-01-01

    We present the latest advances in distributed strain measurement in perfluorinated polymer optical fibres (POFs) using backscatter techniques. Compared to previously introduced poly(methyl methacrylate) POFs, the measurement length can be extended to more than 500 m at improved spatial resolution of a few centimetres. It is shown that strain in a perfluorinated POF can be measured up to 100%. In parallel to these investigations, the incoherent optical frequency domain reflectometry (OFDR) technique is introduced to detect strained fibre sections and to measure distributed length change along the fibre with sub-millimetre resolution by applying a cross-correlation algorithm to the backscatter signal. The overall superior performance of the OFDR technique compared to the optical time domain reflectometry in terms of accuracy, dynamic range, spatial resolution and measurement speed is presented. The proposed sensor system is a promising technique for use in structural health monitoring applications where the precise detection of high strain is required

  16. Phase sensitive spectral domain interferometry for label free biomolecular interaction analysis and biosensing applications

    Science.gov (United States)

    Chirvi, Sajal

    Biomolecular interaction analysis (BIA) plays vital role in wide variety of fields, which include biomedical research, pharmaceutical industry, medical diagnostics, and biotechnology industry. Study and quantification of interactions between natural biomolecules (proteins, enzymes, DNA) and artificially synthesized molecules (drugs) is routinely done using various labeled and label-free BIA techniques. Labeled BIA (Chemiluminescence, Fluorescence, Radioactive) techniques suffer from steric hindrance of labels on interaction site, difficulty of attaching labels to molecules, higher cost and time of assay development. Label free techniques with real time detection capabilities have demonstrated advantages over traditional labeled techniques. The gold standard for label free BIA is surface Plasmon resonance (SPR) that detects and quantifies the changes in refractive index of the ligand-analyte complex molecule with high sensitivity. Although SPR is a highly sensitive BIA technique, it requires custom-made sensor chips and is not well suited for highly multiplexed BIA required in high throughput applications. Moreover implementation of SPR on various biosensing platforms is limited. In this research work spectral domain phase sensitive interferometry (SD-PSI) has been developed for label-free BIA and biosensing applications to address limitations of SPR and other label free techniques. One distinct advantage of SD-PSI compared to other label-free techniques is that it does not require use of custom fabricated biosensor substrates. Laboratory grade, off-the-shelf glass or plastic substrates of suitable thickness with proper surface functionalization are used as biosensor chips. SD-PSI is tested on four separate BIA and biosensing platforms, which include multi-well plate, flow cell, fiber probe with integrated optics and fiber tip biosensor. Sensitivity of 33 ng/ml for anti-IgG is achieved using multi-well platform. Principle of coherence multiplexing for multi

  17. Intra-operative application of optical coherence tomography with an operating microscope.

    Science.gov (United States)

    Just, T; Lankenau, E; Hüttmann, G; Pau, H W

    2009-09-01

    To introduce the use of optical coherence tomography with an operating microscope for intra-operative evaluation of the human larynx. A specially equipped operating microscope with integrated spectral domain optical coherence tomography apparatus was used during microlaryngoscopy. Technical improvements in optical coherence tomography equipment (e.g. pilot beam, variable focal distance, improved image quality and integration into an operating microscope) have enabled greater sensitivity and imaging speed and a non-contact approach. Spectral domain optical coherence tomography now enables a better correlation between optical coherence tomography images and histological findings. With this new technology, the precision of biopsy can be improved during microlaryngoscopy. Use of this new optical coherence tomography technology, integrated into an operating microscope, enables the surgeon to define the biopsy site location and resection plane precisely, while the optical zoom of the operating microscope can be used over the complete range.

  18. Optical stealth transmission based on super-continuum generation in highly nonlinear fiber over WDM network.

    Science.gov (United States)

    Zhu, Huatao; Wang, Rong; Pu, Tao; Fang, Tao; Xiang, Peng; Zheng, Jilin; Chen, Dalei

    2015-06-01

    In this Letter, the optical stealth transmission carried by super-continuum spectrum optical pulses generated in highly nonlinear fiber is proposed and experimentally demonstrated. In the proposed transmission scheme, super-continuum signals are reshaped in the spectral domain through a wavelength-selective switch and are temporally spread by a chromatic dispersion device to achieve the same noise-like characteristic as the noise in optical networks, so that in both the time domain and the spectral domain, the stealth signals are hidden in public channel. Our experimental results show that compared with existing schemes where stealth channels are carried by amplified spontaneous emission noise, super-continuum signal can increase the transmission performance and robustness.

  19. Spectral methods. Fundamentals in single domains

    International Nuclear Information System (INIS)

    Canuto, C.

    2006-01-01

    Since the publication of ''Spectral Methods in Fluid Dynamics'' 1988, spectral methods have become firmly established as a mainstream tool for scientific and engineering computation. The authors of that book have incorporated into this new edition the many improvements in the algorithms and the theory of spectral methods that have been made since then. This latest book retains the tight integration between the theoretical and practical aspects of spectral methods, and the chapters are enhanced with material on the Galerkin with numerical integration version of spectral methods. The discussion of direct and iterative solution methods is also greatly expanded. (orig.)

  20. Multiplex CARS imaging with spectral notch shaped laser pulses delivered by optical fibers.

    Science.gov (United States)

    Oh, Seung Ryeol; Park, Joo Hyun; Kim, Kyung-Soo; Lee, Jae Yong; Kim, Soohyun

    2017-12-11

    We present an experimental demonstration of single-pulse coherent anti-Stokes Raman spectroscopy (CARS) using a spectrally shaped broadband laser that is delivered by an optical fiber to a sample at its distal end. The optical fiber consists of a fiber Bragg grating component to serve as a narrowband notch filter and a combined large-mode-area fiber to transmit such shaped ultrashort laser pulses without spectral distortion in a long distance. Experimentally, our implementation showed a capability to measure CARS spectra of various samples with molecular vibrations in the fingerprint region. Furthermore, CARS imaging of poly(methyl methacrylate) bead samples was carried out successfully under epi-CARS geometry in which backward-scattered CARS signals were collected into a multimode optical fiber. A compatibility of single-pulse CARS scheme with fiber optics, verified in this study, implies a potential for future realization of compact all-fiber CARS spectroscopic imaging systems.

  1. Impact of initial pulse shape on the nonlinear spectral compression in optical fibre

    Science.gov (United States)

    Boscolo, Sonia; Chaussard, Frederic; Andresen, Esben; Rigneault, Hervé; Finot, Christophe

    2018-02-01

    We theoretically study the effects of the temporal intensity profile of the initial pulse on the nonlinear propagation spectral compression process arising from nonlinear propagation in an optical fibre. Various linearly chirped input pulse profiles are considered, and their dynamics is explained with the aid of time-frequency representations. While initially parabolic-shaped pulses show enhanced spectral compression compared to Gaussian pulses, no significant spectral narrowing occurs when initially super-Gaussian pulses are used. Triangular pulses lead to a spectral interference phenomenon similar to the Fresnel bi-prism experiment.

  2. Optical coherence techniques for plasma doppler spectroscopy

    International Nuclear Information System (INIS)

    Howard, J.; Michael, C.; Glass, F.; Cheetham, A.D.

    2000-01-01

    A new electro-optically Modulated Optical Solid-State (MOSS) interferometer has been constructed for measurement of the low order spectral moments of line emission from optically thin radiant media. The instrument, which is based on the principle of the Fourier transform spectrometer, has high etendue and is rugged, compact and inexpensive. By employing electro-optical path-length modulation techniques, the spectral information is transferred to the temporal frequency domain and can be obtained using a single photodetector. Specifically, the zeroth moment (brightness) is given by the average signal level, the first moment (shift) by the modulation phase and the second moment (line width) by the modulation amplitude. (author)

  3. $h - p$ Spectral element methods for elliptic problems on non-smooth domains using parallel computers

    NARCIS (Netherlands)

    Tomar, S.K.

    2002-01-01

    It is well known that elliptic problems when posed on non-smooth domains, develop singularities. We examine such problems within the framework of spectral element methods and resolve the singularities with exponential accuracy.

  4. DWDM-TO-OTDM Conversion by Time-Domain Optical Fourier Transformation

    DEFF Research Database (Denmark)

    Mulvad, Hans Christian Hansen; Hu, Hao; Galili, Michael

    2011-01-01

    We propose DWDM-OTDM conversion by time-domain optical Fourier transformation. Error-free conversion of a 16×10 Gbit/s 50 GHz-spacing DWDM data signal to a 160 Gbit/s OTDM signal with a 2.1 dB average penalty is demonstrated.......We propose DWDM-OTDM conversion by time-domain optical Fourier transformation. Error-free conversion of a 16×10 Gbit/s 50 GHz-spacing DWDM data signal to a 160 Gbit/s OTDM signal with a 2.1 dB average penalty is demonstrated....

  5. Optical microwave filter based on spectral slicing by use of arrayed waveguide gratings.

    Science.gov (United States)

    Pastor, Daniel; Ortega, Beatriz; Capmany, José; Sales, Salvador; Martinez, Alfonso; Muñoz, Pascual

    2003-10-01

    We have experimentally demonstrated a new optical signal processor based on the use of arrayed waveguide gratings. The structure exploits the concept of spectral slicing combined with the use of an optical dispersive medium. The approach presents increased flexibility from previous slicing-based structures in terms of tunability, reconfiguration, and apodization of the samples or coefficients of the transversal optical filter.

  6. A Simple Novel Technique of Infrared Meibography by Means of Spectral-Domain Optical Coherence Tomography: A Cross-Sectional Clinical Study.

    Directory of Open Access Journals (Sweden)

    Pietro Emanuele Napoli

    Full Text Available To compare a novel spectral-domain optical coherence tomography (SD-OCT technique with traditional lid transillumination for evaluation of meibomian glands (MGs and to assess the relation of MG morphologic changes to the glandular atrophy.Evaluation of diagnostic technology.Sixty-one patients with obstructive MGD (30 men, 31 women; age [mean ± standard deviation] 45.1 ± 12.1 years, and 75 control subjects (32 men, 43 women; 44.1 ± 12.5 years were recruited in order to have a balanced distribution of glandular features.Agreement between SD-OCT and lid transillumination examination for the detection of drop-out (partial or complete loss of MGs and microscopic changes (i.e. shortening, distortion, segmentation and entanglement, as well as the relationship between morphological features and MG atrophy were evaluated.Agreement between the two meibographic techniques, bias in symmetry of classification, and association analysis between microscopic changes and MG dropout.Overall agreement for all morphological features was substantial (Cohen kappa coefficient = 0.77; p<0.001, even if, the majority of disagreement occurred for cases with segmentation, where agreement was present in only 108 (81.82% of 132 eyes with adequate images for interpretation, and where SD-OCT tended to diagnose more cases not detected by traditional lid transillumination (McNemar test, p<0.001. Moreover, segmentation and distortion pattern negatively correlated with the degree of drop-out, whereas shortening and entanglement pattern demonstrated only a weak correlation (Spearman's ρ was -0.691, -0.491, -0.359, -0.385, respectively.Each method has its advantages but in general there was close agreement between these meibographic techniques, particularly for MG dropout, which supports the reliability of our novel, simple and patient-friendly SD-OCT approach.

  7. Optical decoherence and persistent spectral hole burning in Er3+:LiNbO3

    International Nuclear Information System (INIS)

    Thiel, C.W.; Macfarlane, R.M.; Boettger, T.; Sun, Y.; Cone, R.L.; Babbitt, W.R.

    2010-01-01

    Developing new resonant optical materials for spatial-spectral holography and quantum information applications requires detailed knowledge of the decoherence and population relaxation dynamics for the quantum states involved in the optical transitions, motivating the need for fundamental material studies. We report recent progress in studying these properties in erbium-doped lithium niobate at liquid helium temperatures. The influence of temperature, applied magnetic fields, measurement timescale, and dopant concentration were probed using photon echo spectroscopy and time-resolved spectral hole burning on the 1532 nm transition of Er 3+ :LiNbO 3 . Effects of spectral diffusion due to interactions between Er 3+ ions and between the Er 3+ ion and 7 Li and 93 Nb nuclear spins in the host lattice were observed. In addition, long-lived persistent spectral storage of seconds to minutes was observed due to non-equilibrium population redistribution among superhyperfine states.

  8. Two- and three-dimensional topographic analysis of pathologically myopic eyes with dome-shaped macula and inferior staphyloma by spectral domain optical coherence tomography.

    Science.gov (United States)

    García-Ben, Antonio; Kamal-Salah, Radua; García-Basterra, Ignacio; Gonzalez Gómez, Ana; Morillo Sanchez, María José; García-Campos, Jose Manuel

    2017-05-01

    To investigate the posterior anatomical structure of pathologically myopic eyes with dome-shaped macula and inferior staphyloma using spectral domain optical coherence tomography (SD-OCT). Our database of 260 pathologically myopic eyes was analyzed retrospectively to identify patients with dome-shaped macula and inferior staphyloma. All patients underwent vertical and horizontal SD-OCT scans across the central fovea, with three-dimensional macular map reconstruction. Best-corrected visual acuity, axial length, and choroidal thickness measurements were recorded. The macular bulge height was also analyzed in eyes with dome-shaped macula. In the three-dimensional images, the symmetry and orientation of the main plane of the inward incurvation of the macula were examined. Twenty-eight (10.7%) of the 260 pathologically myopic eyes had dome-shaped macula of one of three different types: a round radially symmetrical dome (eight eyes, 28.5%), a horizontal axially symmetrical oval-shaped dome (15 eyes, 53.5%), or a vertical axially symmetrical oval-shaped dome (five eyes, 17.8%). The macular bulge height was significantly greater in horizontal oval-shaped dome eyes (p = 0.01, for each comparison). Inferior posterior staphylomas were observed in ten (3.8%) of the 260 pathologically myopic eyes with asymmetrical macular bends. Vertical and horizontal OCT sectional scanning in combination with three-dimensional macular map reconstruction provides important information for understanding the posterior anatomical structure of dome-shaped macula and inferior staphyloma in pathologically myopic eyes.

  9. Invited Article: Acousto-optic finite-difference frequency-domain algorithm for first-principles simulations of on-chip acousto-optic devices

    Directory of Open Access Journals (Sweden)

    Yu Shi

    2017-02-01

    Full Text Available We introduce a finite-difference frequency-domain algorithm for coupled acousto-optic simulations. First-principles acousto-optic simulation in time domain has been challenging due to the fact that the acoustic and optical frequencies differ by many orders of magnitude. We bypass this difficulty by formulating the interactions between the optical and acoustic waves rigorously as a system of coupled nonlinear equations in frequency domain. This approach is particularly suited for on-chip devices that are based on a variety of acousto-optic interactions such as the stimulated Brillouin scattering. We validate our algorithm by simulating a stimulated Brillouin scattering process in a suspended waveguide structure and find excellent agreement with coupled-mode theory. We further provide an example of a simulation for a compact on-chip resonator device that greatly enhances the effect of stimulated Brillouin scattering. Our algorithm should facilitate the design of nanophotonic on-chip devices for the harnessing of photon-phonon interactions.

  10. The diagnostic use of choroidal thickness analysis and its correlation with visual field indices in glaucoma using spectral domain optical coherence tomography.

    Directory of Open Access Journals (Sweden)

    Zhongjing Lin

    Full Text Available To evaluate the quantitative characteristics of choroidal thickness in primary open-angle glaucoma (POAG, normal tension glaucoma (NTG and in normal eyes using spectral-domain optical coherence tomography (SD-OCT. To evaluate the diagnostic ability of choroidal thickness in glaucoma and to determine the correlation between choroidal thickness and visual field parameters in glaucoma.A total of 116 subjects including 40 POAG, 30 NTG and 46 healthy subjects were enrolled in this study. Choroidal thickness measurements were acquired in the macular and peripapillary regions using SD-OCT. All subjects underwent white-on-white (W/W and blue-on-yellow (B/Y visual field tests using Humphrey Field Analyzer. The receiver operating characteristic (ROC curve and the area under curve (AUC were generated to assess the discriminating power of choroidal thickness for glaucoma. Pearson's correlation coefficients were calculated to assess the structure function correlation for glaucoma patients.No significant differences were observed for macular choroidal thickness among the different groups (all P > 0.05. Regarding the peripapillary choroidal thickness (PPCT, significant differences were observed among the three groups (all P 0.05, but showed significant correlations with B/Y MD (all P < 0.05. In the early glaucomatous eyes, PPCT showed significant correlations with W/W MD and B/Y MD (all P < 0.05.In our study, peripapillary choroidal thickness measured on OCT showed a low to moderate but statistically significant diagnostic power and a significant correlation with blue-on-yellow visual field indices in glaucoma. This may indicate a potential adjunct for peripapillary choroidal thickness in glaucoma diagnosis.

  11. Optical network control plane for multi-domain networking

    DEFF Research Database (Denmark)

    Manolova, Anna Vasileva

    This thesis focuses on multi-domain routing for traffice engineering and survivability support in optical transport networks under the Generalized Multi-Protocol Label Switching (GMPLS) control framework. First, different extensions to the Border Gateway Protocol for multi-domain Traffic...... process are not enough for efficient TE in mesh multi-domain networks. Enhancing the protocol with multi-path dissemination capability, combined with the employment of an end-to-end TE metric proves to be a highly efficient solution. Simulation results show good performance characteristics of the proposed...... is not as essential for improved network performance as the length of the provided paths. Second, the issue of multi-domain survivability support is analyzed. An AS-disjoint paths is beneficial not only for resilience support, but also for facilitating adequate network reactions to changes in the network, which...

  12. Control systems using modal domain optical fiber sensors for smart structure applications

    Science.gov (United States)

    Lindner, Douglas K.; Reichard, Karl M.

    1991-01-01

    Recently, a new class of sensors has emerged for structural control which respond to environmental changes over a significant gauge length; these sensors are called distributed-effect sensors. These sensors can be fabricated with spatially varying sensitivity to the distributed measurand, and can be configured to measure a variety of structural parameters which can not be measured directly using point sensors. Examples of distributed-effect sensors include piezoelectric film, holographic sensors, and modal domain optical fiber sensors. Optical fiber sensors are particularly attractive for smart structure applications because they are flexible, have low mass, and can easily be embedded directly into materials. In this paper we describe the implementation of weighted modal domain optical fiber sensors. The mathematical model of the modal domain optical fiber sensor model is described and used to derive an expression for the sensor sensitivity. The effects of parameter variations on the sensor sensitivity are demonstrated to illustrate methods of spatially varying the sensor sensitivity.

  13. Single interval shortwave radiation scheme with parameterized optical saturation and spectral overlaps

    Czech Academy of Sciences Publication Activity Database

    Mašek, Jan; Geleyn, J.- F.; Brožková, Radmila; Giot, O.; Achom, H. O.; Kuma, P.

    2016-01-01

    Roč. 142, č. 659 (2016), s. 304-326 ISSN 0035-9009 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0073 Institutional support: RVO:67179843 Keywords : shortwave radiative transfer * delta-two stream system * broadband approach * Malkmus band model * optical saturation * idealized optical paths * spectral overlap Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 3.444, year: 2016

  14. Frequency-domain multisource optical spectrometer and oximeter

    Science.gov (United States)

    Fantini, Sergio; Franceschini, Maria-Angela; Maier, John S.; Walker, Scott A.; Gratton, Enrico

    1995-01-01

    We have designed and constructed a near-infrared spectrometer for the non-invasive optical study of biological tissue. This instrument works in the frequency-domain and employs multiple source-detector distances to recover the absorption coefficient ((mu) (alpha )) and the reduced scattering coefficient ((mu) s') of tissue. The light sources are eight light emitting diodes (LEDs) whose intensities are modulated at a frequency of 120 MHz. Four LEDs emit light at a peak wavelength of 715 nm ((lambda) 1), while the other four LEDs emit at a peak wavelength of 850 nm ((lambda) 2). From the frequency-domain raw data of phase, dc intensity, and ac amplitude obtained from each one of the eight light sources, which are located at different distances from the detector fiber, we calculate (mu) (alpha ) and (mu) s' at the two wavelengths (lambda) 1 and (lambda) 2. The concentrations of oxy- and deoxy-hemoglobin, and hence hemoglobin saturation, are then derived from the known extinction coefficients of oxy- and deoxy-hemoglobin at (lambda) 1 and (lambda) 2. The statistical error in the measurement of the optical coefficients due to instrument noise is about 1 - 2%. The accuracy in the determination of the absolute value of the optical coefficients is within 10 - 20%. Preliminary results obtained in vivo on the forearm of a volunteer during an ischemia measurement protocol are presented.

  15. Linear and nonlinear optical spectroscopy: Spectral, temporal and spatial resolution

    DEFF Research Database (Denmark)

    Hvam, Jørn Marcher

    1997-01-01

    Selected linear and nonlinear optical spectroscopies are being described with special emphasis on the possibility of obtaining simultaneous spectral, temporal and spatial resolution. The potential of various experimental techniques is being demonstrated by specific examples mostly taken from inve...... investigations of the electronic, and opto-electronic, properties of semiconductor nanostructures....

  16. Spectral tailoring of nanoscale EUV and soft x-ray multilayer optics

    NARCIS (Netherlands)

    Huang, Qiushi; Medvedev, Viacheslav; van de Kruijs, Robbert Wilhelmus Elisabeth; Yakshin, Andrey; Louis, Eric; Bijkerk, Frederik

    2017-01-01

    Extreme ultraviolet and soft X-ray (XUV) multilayer optics have experienced significant development over the past few years, particularly on controlling the spectral characteristics of light for advanced applications like EUV photolithography, space observation, and accelerator- or lab-based XUV

  17. High Time-Resolution 640-Gb/s Clock Recovery Using Time-Domain Optical Fourier Transformation and Narrowband Optical Filter

    DEFF Research Database (Denmark)

    Guan, P.; Mulvad, Hans Christian Hansen; Kasai, K.

    2010-01-01

    We present a novel scheme for subharmonic clock recovery from an optical time-division-multiplexing signal using time-domain optical Fourier transformation and a narrowband optical filter. High-resolution 640-Gb/s clock recovery is successfully demonstrated with no pattern dependence. The clock...

  18. Growth, spectral, linear and nonlinear optical characteristics of an efficient semiorganic acentric crystal: L-valinium L-valine chloride

    Energy Technology Data Exchange (ETDEWEB)

    Nageshwari, M.; Jayaprakash, P.; Kumari, C. Rathika Thaya [PG & Research Department of Physics, Arignar Anna Govt. Arts College, Cheyyar 604407, Tamil Nadu (India); Vinitha, G. [Department of Physics, School of Advanced Sciences, VIT Chennai, 600127 Tamil Nadu (India); Caroline, M. Lydia, E-mail: lydiacaroline2006@yahoo.co.in [PG & Research Department of Physics, Arignar Anna Govt. Arts College, Cheyyar 604407, Tamil Nadu (India)

    2017-04-15

    An efficient nonlinear optical semiorganic material L-valinium L-valine chloride (LVVCl) was synthesized and grown-up by means of slow evaporation process. Single crystal XRD evince that LVVCl corresponds to monoclinic system having acentric space group P2{sub 1}. The diverse functional groups existing in LVVCl were discovered with FTIR spectral investigation. The UV-Visible and photoluminescence spectrum discloses the optical and electronic properties respectively for the grown crystal. Several optical properties specifically extinction coefficient, reflectance, linear refractive index, electrical and optical conductivity were also determined. The SEM analysis was also carried out and it portrayed the surface morphology of LVVCl. The calculated value of laser damage threshold was 2.59 GW/cm{sup 2}. The mechanical and dielectric property of LVVCl was investigated employing microhardness and dielectric studies. The second and third order nonlinear optical characteristics of LVVCl was characterized utilizing Kurtz Perry and Z scan technique respectively clearly suggest its suitability in the domain of optics and photonics. - Graphical abstract: Good quality transparent single crystals of L-valinium L-valine chloride single crystal was grown by slow evaporation technique. The grown crystals were analyzed using different instrumentation methods to check its usefulness for the device fabrication. The determination of nonlinear refractive index (n{sub 2}), absorption coefficient (β) and third order nonlinear susceptibility was determined by Z scan technique, highlighted that LVVCl can serve as a promising candidate for opto electronic and nonlinear optical applications.

  19. On the possibility of developing incoherent fibre-optic data transmission systems based on signal spectral coding with matched acousto-optical filters

    International Nuclear Information System (INIS)

    Proklov, Valerii V; Byshevski-Konopko, O A; Grigorievski, V I

    2013-01-01

    The scheme is suggested for developing the optical communication line based on the principle of code division of multiple access with matched acousto-optical filters and a 16-bit long Walsh sequence. Results of modelling show that such a line can operate if adjacent spectral lines are separated by at least double the Rayleigh criterion. (optical information transmission)

  20. Longitudinal analysis of progression in glaucoma using spectral-domain optical coherence tomography.

    Science.gov (United States)

    Wessel, Julia M; Horn, Folkert K; Tornow, Ralf P; Schmid, Matthias; Mardin, Christian Y; Kruse, Friedrich E; Juenemann, Anselm G; Laemmer, Robert

    2013-05-01

    To compare the longitudinal loss of RNFL thickness measurements by SD-OCT in healthy individuals and glaucoma patients with or without progression concerning optic disc morphology. A total of 62 eyes, comprising 38 glaucomatous eyes with open angle glaucoma and 24 healthy controls, were included in the study (Erlangen Glaucoma Registry, NTC00494923). All patients were investigated annually over a period of 3 years by Spectralis SD-OCT measuring peripapillary RNFL thickness. By masked comparative analysis of photographs, the eyes were classified into nonprogressive and progressive glaucoma cases. Longitudinal loss of RNFL thickness was compared with morphological changes of optic disc morphology. Mixed model analysis of annual OCT scans revealed an estimated annual decrease of the RNFL thickness by 2.12 μm in glaucoma eyes with progression, whereas glaucoma eyes without progression in optic disc morphology lost 1.18 μm per year in RNFL thickness (P = 0.002). The rate of change in healthy eyes was 0.60 μm and thereby also significantly lower than in glaucoma eyes with progression (P < 0.001). The intrasession variability of three successive measurements without head repositioning was 1.5 ± 0.7 μm. The loss of mean RNFL thickness exceeded the intrasession variability in 60% of nonprogressive eyes, and in 85% of progressive eyes after 3 years. LONGITUDINAL MEASUREMENTS OF RNFL THICKNESS USING SD-OCT SHOW A MORE PRONOUNCED REDUCTION OF RNFL THICKNESS IN PATIENTS WITH PROGRESSION COMPARED WITH PATIENTS WITHOUT PROGRESSION IN GLAUCOMATOUS OPTIC DISC CHANGES. (www.clinicaltrials.gov number, NTC00494923.).

  1. Mapping possible flowpaths of contaminants through surface and cross-borehole spectral time-domain induced polarization

    DEFF Research Database (Denmark)

    Bording, Thue Sylvester; Fiandaca, Gianluca; Maurya, Pradip Kumar

    Traditional methods for mapping possible flowpaths of contaminants in sedimentary environments by boreholes may often be insufficient. Additional information may be acquired by geophysical methods. In the present study, cross-borehole and surface measurements were performed using time-domain indu......-domain induced polarization (TDIP). After measurements the entire test site was dug out, and the geology was described. A 2D spectral inversion of the combined dataset is presented, which is in great correspondence with the observed geology....

  2. Spectral shaping for non-Gaussian source spectra in optical coherence tomography

    NARCIS (Netherlands)

    Tripathi, R; Nassif, N. A.; Nelson, JS; Park, B.H.; de Boer, JF

    2002-01-01

    We present a digital spectral shaping technique to reduce the sidelobes (ringing) of the axial point-spread function in optical coherence tomography for non-Gaussian-shaped source spectra. The spectra of two superluminescent diodes were combined to generate a spectrum with significant modulation.

  3. Integration of spectral domain optical coherence tomography with microperimetry generates unique datasets for the simultaneous identification of visual function and retinal structure in ophthalmological applications

    Science.gov (United States)

    Koulen, Peter; Gallimore, Gary; Vincent, Ryan D.; Sabates, Nelson R.; Sabates, Felix N.

    2011-06-01

    Conventional perimeters are used routinely in various eye disease states to evaluate the central visual field and to quantitatively map sensitivity. However, standard automated perimetry proves difficult for retina and specifically macular disease due to the need for central and steady fixation. Advances in instrumentation have led to microperimetry, which incorporates eye tracking for placement of macular sensitivity values onto an image of the macular fundus thus enabling a precise functional and anatomical mapping of the central visual field. Functional sensitivity of the retina can be compared with the observed structural parameters that are acquired with high-resolution spectral domain optical coherence tomography and by integration of scanning laser ophthalmoscope-driven imaging. Findings of the present study generate a basis for age-matched comparison of sensitivity values in patients with macular pathology. Microperimetry registered with detailed structural data performed before and after intervention treatments provides valuable information about macular function, disease progression and treatment success. This approach also allows for the detection of disease or treatment related changes in retinal sensitivity when visual acuity is not affected and can drive the decision making process in choosing different treatment regimens and guiding visual rehabilitation. This has immediate relevance for applications in central retinal vein occlusion, central serous choroidopathy, age-related macular degeneration, familial macular dystrophy and several other forms of retina related visual disability.

  4. Soil-embedded optical fiber sensing cable interrogated by Brillouin optical time-domain reflectometry (B-OTDR) and optical frequency-domain reflectometry (OFDR) for embedded cavity detection and sinkhole warning system

    International Nuclear Information System (INIS)

    Lanticq, V; Bourgeois, E; Delepine-Lesoille, S; Magnien, P; Dieleman, L; Vinceslas, G; Sang, A

    2009-01-01

    A soil-embedded optical fiber sensing cable is evaluated for an embedded cavity detection and sinkhole warning system in railway tunnels. Tests were performed on a decametric structure equipped with an embedded 110 m long fiber optic cable. Both Brillouin optical time-domain reflectometry (B-OTDR) and optical frequency-domain reflectometry (OFDR) sensing techniques were used for cable interrogation, yielding results that were in good qualitative agreement with finite-element calculations. Theoretical and experimental comparison enabled physical interpretation of the influence of ground properties, and the analysis of embedded cavity size and position. A 5 mm embedded cavity located 2 m away from the sensing cable was detected. The commercially available sensing cable remained intact after soil collapse. Specificities of each technique are analyzed in view of the application requirements. For tunnel monitoring, the OFDR technique was determined to be more viable than the B-OTDR due to higher spatial resolution, resulting in better detection and size determination of the embedded cavities. Conclusions of this investigation gave outlines for future field use of distributed strain-sensing methods under railways and more precisely enabled designing a warning system suited to the Ebersviller tunnel specificities

  5. In vivo imaging of palisades of Vogt in dry eye versus normal subjects using en-face spectral-domain optical coherence tomography.

    Directory of Open Access Journals (Sweden)

    Wajdene Ghouali

    Full Text Available To evaluate a possible clinical application of spectral-domain optical coherence tomography (SD-OCT using en-face module for the imaging of the corneoscleral limbus in normal subjects and dry eye patients.Seventy-six subjects were included in this study. Seventy eyes of 35 consecutive patients with dry eye disease and 82 eyes of 41 healthy control subjects were investigated. All subjects were examined with the Avanti RTVue® anterior segment OCT. En-face OCT images of the corneoscleral limbus were acquired in four quadrants (inferior, superior, nasal and temporal and then were analyzed semi-quantitatively according to whether or not palisades of Vogt (POV were visible. En-face OCT images were then compared to in vivo confocal microscopy (IVCM in eleven eyes of 7 healthy and dry eye patients.En-face SD-OCT showed POV as a radially oriented network, located in superficial corneoscleral limbus, with a good correlation with IVCM features. It provided an easy and reproducible identification of POV without any special preparation or any direct contact, with a grading scale from 0 (no visualization to 3 (high visualization. The POV were found predominantly in superior (P<0.001 and inferior (P<0.001 quadrants when compared to the nasal and temporal quadrants for all subjects examined. The visibility score decreased with age (P<0.001 and was lower in dry eye patients (P<0.01. In addition, the score decreased in accordance with the severity of dry eye disease (P<0.001.En-face SD-OCT is a non-contact imaging technique that can be used to evaluate the POV, thus providing valuable information about differences in the limbal anatomy of dry eye patients as compared to healthy patients.

  6. Two optical bistability domains in composites of metal nanoparticles with nonlinear dielectric core

    Energy Technology Data Exchange (ETDEWEB)

    Shewamare, Sisay, E-mail: sisayshewa20@yahoo.com [Department of Physics, Addis Ababa University, P.O. Box 1176, Addis Ababa (Ethiopia); Mal' nev, V.N., E-mail: vadimnmalnev@yahoo.com [Department of Physics, Addis Ababa University, P.O. Box 1176, Addis Ababa (Ethiopia)

    2012-12-15

    It is shown that the local field in metal spherical particles with a dielectric core in an external varying electric field has two maxima at two different frequencies. The second maximum becomes more important with an increment in the metal fraction. Due to the nonlinear dielectric function of the core, the composite of these inclusions may have two optically induced bistability domains at different frequencies. At rather high metal fraction, two bistability domains merge and form one entire bistability domain. The parameters of these domains are studied numerically. The paper focuses on the second bistability domain, which has not been discussed in the literature so far. This domain exists in a comparatively narrow frequency range and its onset fields are lower than those of the first bistability domain. The lowest bistability onset fields are obtained in the entire domain. This peculiarity of the optical induced bistability in the metal composite with small dielectric cores can be attractive for possible applications.

  7. Two optical bistability domains in composites of metal nanoparticles with nonlinear dielectric core

    International Nuclear Information System (INIS)

    Shewamare, Sisay; Mal'nev, V.N.

    2012-01-01

    It is shown that the local field in metal spherical particles with a dielectric core in an external varying electric field has two maxima at two different frequencies. The second maximum becomes more important with an increment in the metal fraction. Due to the nonlinear dielectric function of the core, the composite of these inclusions may have two optically induced bistability domains at different frequencies. At rather high metal fraction, two bistability domains merge and form one entire bistability domain. The parameters of these domains are studied numerically. The paper focuses on the second bistability domain, which has not been discussed in the literature so far. This domain exists in a comparatively narrow frequency range and its onset fields are lower than those of the first bistability domain. The lowest bistability onset fields are obtained in the entire domain. This peculiarity of the optical induced bistability in the metal composite with small dielectric cores can be attractive for possible applications.

  8. Nondestructive analysis of automotive paints with spectral domain optical coherence tomography.

    Science.gov (United States)

    Dong, Yue; Lawman, Samuel; Zheng, Yalin; Williams, Dominic; Zhang, Jinke; Shen, Yao-Chun

    2016-05-01

    We have demonstrated for the first time, to our knowledge, the use of optical coherence tomography (OCT) as an analytical tool for nondestructively characterizing the individual paint layer thickness of multiple layered automotive paints. A graph-based segmentation method was used for automatic analysis of the thickness distribution for the top layers of solid color paints. The thicknesses measured with OCT were in good agreement with the optical microscope and ultrasonic techniques that are the current standard in the automobile industry. Because of its high axial resolution (5.5 μm), the OCT technique was shown to be able to resolve the thickness of individual paint layers down to 11 μm. With its high lateral resolution (12.4 μm), the OCT system was also able to measure the cross-sectional area of the aluminum flakes in a metallic automotive paint. The range of values measured was 300-1850  μm2. In summary, the proposed OCT is a noncontact, high-resolution technique that has the potential for inclusion as part of the quality assurance process in automobile coating.

  9. Advanced spectral processing of broadband light using acousto-optic devices with arbitrary transmission functions.

    Science.gov (United States)

    Molchanov, Vladimir Ya; Yushkov, Konstantin B

    2014-06-30

    In the paper, we developed a dispersive method for transmission function synthesis of collinear and quasi-collinear acousto-optic tunable filters. General theoretical consideration was performed, and modelling was made for broadband and narrowband signals. Experimental results on spectral shaping of femtosecond laser emission were obtained. Binary spectral encoding of broadband emission was demonstrated.

  10. Algebraic reconstruction techniques for spectral reconstruction in diffuse optical tomography

    International Nuclear Information System (INIS)

    Brendel, Bernhard; Ziegler, Ronny; Nielsen, Tim

    2008-01-01

    Reconstruction in diffuse optical tomography (DOT) necessitates solving the diffusion equation, which is nonlinear with respect to the parameters that have to be reconstructed. Currently applied solving methods are based on the linearization of the equation. For spectral three-dimensional reconstruction, the emerging equation system is too large for direct inversion, but the application of iterative methods is feasible. Computational effort and speed of convergence of these iterative methods are crucial since they determine the computation time of the reconstruction. In this paper, the iterative methods algebraic reconstruction technique (ART) and conjugated gradients (CGs) as well as a new modified ART method are investigated for spectral DOT reconstruction. The aim of the modified ART scheme is to speed up the convergence by considering the specific conditions of spectral reconstruction. As a result, it converges much faster to favorable results than conventional ART and CG methods

  11. Optical decoherence and persistent spectral hole burning in Tm3+:LiNbO3

    International Nuclear Information System (INIS)

    Thiel, C.W.; Sun, Y.; Boettger, T.; Babbitt, W.R.; Cone, R.L.

    2010-01-01

    We report studies of decoherence and spectral hole burning for the 794 nm optical transition of thulium-doped lithium niobate. In addition to transient spectral holes due to the 3 H 4 and 3 F 4 excited states of Tm 3+ , persistent spectral holes with lifetimes of up to minutes were observed when a magnetic field of a few hundred Gauss was applied. The observed anti-hole structure identified the hole burning mechanism as population storage in the 169 Tm nuclear hyperfine levels. In addition, the magnetic field was effective in suppressing spectral diffusion, increasing the phase memory lifetime from 11 μs at zero field to 23 μs in a field of 320 Gauss applied along the crystal's c-axis. Coupling between Tm 3+ and the 7 Li and 93 Nb spins in the host lattice was also observed and a quadrupole shift of 22 kHz was measured for 7 Li at 1.7 K. A Stark shift of 18 kHz cm/V was measured for the optical transition with the electric field applied parallel to the c-axis.

  12. Investigations of soft and hard tissues in oral cavity by spectral domain optical coherence tomography

    Science.gov (United States)

    Madjarova, Violeta Dimitrova; Yasuno, Yoshiaki; Makita, Shuichi; Hori, Yasuaki; Voeffray, Jean-Baptiste; Itoh, Masahide; Yatagai, Toyohiko; Tamura, Masami; Nanbu, Toshiyuki

    2006-02-01

    Fourier Domain Optical Coherence Tomography (SD-OCT) systems for dental measurements are demonstrated. Two systems have been developed. The first system is fiber based Michelson interferometer with super luminescent diodes at 1310 nm and 100 nm FWHM as a light source. The sensitivity of the system was 106 dB with depth measurement range in air of 2.5 mm. The second systems is a fiber based Mach-Zehnder interferometer with wavelength scanning laser as light source at center wavelength of 1310 nm, wavelength range of 110 nm and scanning rate of 20 KHz. The sensitivity of the system is 112 dB and depth measurement range in air is 6 mm. Both systems can acquire real-time three dimensional (3-D) images in the range of several second. The systems were applied for early caries detection in tooth, for diagnostics of tooth condition after operational tooth treatment, and for diagnostics of the alveolar bone structure. In-vivo measurements were performed on two volunteers. The systems were able to detect discontinuities in tooth and resin filling after tooth treatment. In addition early carries lesion was detected in one of the volunteers. The 3-D profile of the alveolar bone was acquired for first time with non-contact method.

  13. Signal enhancement by spectral equalization of high frequency broadband signals transmitted through optical fibers

    International Nuclear Information System (INIS)

    Lyons, P.B.; Ogle, J.W.; Holzman, M.A.

    1980-01-01

    A new technique is discussed for enhancing the bandwidth and intensity of high frequency (> 1 GHz) analog, spectrally broad (40 nm) signals transmitted through one kilometer of optical fiber. The existing method for bandwidth enhancement of such a signal uses a very narrow (approx. 1 nm) filter between the fiber and detector to limit bandwidth degradation due to material dispersion. Using this method, most of the available optical intensity is rejected and lost. This new technique replaces the narrow-band filter with a spectral equalizer device which uses a reflection grating to disperse the input signal spectrum and direct it onto a linear array of fibers

  14. Real-time all-optical OFDM transmission system based on time-domain optical fourier transformation

    DEFF Research Database (Denmark)

    Guan, Pengyu; Kong, Deming; Røge, Kasper Meldgaard

    2014-01-01

    We propose a novel simple all-optical OFDM transmission system based on time-domain OFT using time-lenses. A real-time 160 Gbit/s DPSK OFDM transmission with 16 decorrelated data subcarriers is successfully demonstrated over 100 km....

  15. Retrieval of the thickness and refractive index dispersion of parallel plate from a single interferogram recorded in both spectral and angular domains

    Science.gov (United States)

    Dong, Jingtao; Lu, Rongsheng

    2018-04-01

    The principle of retrieving the thickness and refractive index dispersion of a parallel glass plate is reported based on single interferogram recording and phase analysis. With the parallel plate illuminated by a convergent light sheet, the transmitted light interfering in both spectral and angular domains is recorded. The phase recovered from the single interferogram by Fourier analysis is used to retrieve the thickness and refractive index dispersion without periodic ambiguity. Experimental results of an optical substrate standard show that the accuracy of refractive index dispersion is less than 2.5 × 10-5 and the relative uncertainty of thickness is 6 × 10-5 (3σ). This method is confirmed to be robust against the intensity noises, indicating the capability of stable and accurate measurement.

  16. Evaluation of methods to determine the spectral variations of aerosol optical thickness

    Digital Repository Service at National Institute of Oceanography (India)

    Suresh, T.; Talaulikar, M.; Rodrigues, A.; Desa, E.; Chauhan, P.

    The methods used to derive spectral variations of aerosol optical thickness, AOT are evaluated. For our analysis we have used the AOT measured using a hand held sunphotometer at the coastal station on the west coast of India, Dona-Paula, Goa...

  17. Extended chaotic domain in the long optical fibers based on SBS process

    International Nuclear Information System (INIS)

    Gao, Junbo; Ding, Yingchun; Chen, Zhaoyang; Lin, Chengyou

    2014-01-01

    Chaotic stimulated Brillouin scattering (SBS) in optical fibers with weak external optical feedback has been investigated experimentally and theoretically. However, only the bifurcation route to chaos through period-one and quasi-periodic emission was discovered in the former work because the chaotic domain is very short in the general nonlinear system. In order to control the chaos process and observe finer periodic-orbit structures, a novel experiment was designed to extend the chaotic domain by using long optical fibers in the SBS system. In this experiment, the period-one, period-doubling, period-four and period-eight cycle routes to the chaos laser process as well as the more details of chaos, have been observed.

  18. Resolving fine spectral features in lattice vibrational modes using femtosecond coherent spectroscopy

    Directory of Open Access Journals (Sweden)

    A. Card

    2016-02-01

    Full Text Available We show resolution of fine spectral features within several Raman active vibrational modes in potassium titanyl phosphate (KTP crystal. Measurements are performed using a femtosecond time-domain coherent anti-Stokes Raman scattering spectroscopy technique that is capable of delivering equivalent spectral resolution of 0.1 cm−1. The Raman spectra retrieved from our measurements show several spectral components corresponding to vibrations of different symmetry with distinctly different damping rates. In particular, linewidths for unassigned optical phonon mode triplet centered at around 820 cm−1 are found to be 7.5 ± 0.2 cm−1, 9.1 ± 0.3 cm−1, and 11.2 ± 0.3 cm−1. Results of our experiments will ultimately help to design an all-solid-state source for sub-optical-wavelength waveform generation that is based on stimulated Raman scattering.

  19. High-Speed Microscale Optical Tracking Using Digital Frequency-Domain Multiplexing

    OpenAIRE

    MacLachlan, Robert A.; Riviere, Cameron N.

    2009-01-01

    Position-sensitive detectors (PSDs), or lateral-effect photodiodes, are commonly used for high-speed, high-resolution optical position measurement. This paper describes the instrument design for multidimensional position and orientation measurement based on the simultaneous position measurement of multiple modulated sources using frequency-domain-multiplexed (FDM) PSDs. The important advantages of this optical configuration in comparison with laser/mirror combinations are that it has a large ...

  20. Optical decoherence and persistent spectral hole burning in Er{sup 3+}:LiNbO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Thiel, C.W., E-mail: thiel@physics.montana.ed [Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States); Department of Physics, Montana State University, Bozeman, MT 59717 (United States); Macfarlane, R.M. [Department of Physics, Montana State University, Bozeman, MT 59717 (United States); IBM Almaden Research Center, San Jose, CA 95120 (United States); Boettger, T. [Department of Physics, University of San Francisco, San Francisco, CA 94117 (United States); Sun, Y. [Department of Physics, University of South Dakota, Vermillion, SD 57069 (United States); Cone, R.L. [Department of Physics, Montana State University, Bozeman, MT 59717 (United States); Babbitt, W.R. [Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States); Department of Physics, Montana State University, Bozeman, MT 59717 (United States)

    2010-09-15

    Developing new resonant optical materials for spatial-spectral holography and quantum information applications requires detailed knowledge of the decoherence and population relaxation dynamics for the quantum states involved in the optical transitions, motivating the need for fundamental material studies. We report recent progress in studying these properties in erbium-doped lithium niobate at liquid helium temperatures. The influence of temperature, applied magnetic fields, measurement timescale, and dopant concentration were probed using photon echo spectroscopy and time-resolved spectral hole burning on the 1532 nm transition of Er{sup 3+}:LiNbO{sub 3}. Effects of spectral diffusion due to interactions between Er{sup 3+} ions and between the Er{sup 3+} ion and {sup 7}Li and {sup 93}Nb nuclear spins in the host lattice were observed. In addition, long-lived persistent spectral storage of seconds to minutes was observed due to non-equilibrium population redistribution among superhyperfine states.

  1. All-optical cryptography of M-QAM formats by using two-dimensional spectrally sliced keys.

    Science.gov (United States)

    Abbade, Marcelo L F; Cvijetic, Milorad; Messani, Carlos A; Alves, Cleiton J; Tenenbaum, Stefan

    2015-05-10

    There has been an increased interest in enhancing the security of optical communications systems and networks. All-optical cryptography methods have been considered as an alternative to electronic data encryption. In this paper we propose and verify the use of a novel all-optical scheme based on cryptographic keys applied on the spectral signal for encryption of the M-QAM modulated data with bit rates of up to 200 gigabits per second.

  2. Spectral domain optical coherence tomography changes following intravitreal dexamethasone implant, Ozurdex ® in patients with uveitic cystoid macular edema

    Directory of Open Access Journals (Sweden)

    Pooja Bansal

    2015-01-01

    Full Text Available Purpose: To correlate the structural and functional changes following intravitreal injection of dexamethasone 0.7 mg (Ozurdex ® implant in patients with recalcitrant uveitic cystoid macular edema (CME. Materials and Methods: In a prospective, interventional, nonrandomized study, 30 eyes (27 patients with uveitic CME received Ozurdex ® implant and were followed-up for 24 weeks at periodic intervals to monitor structural alterations seen on spectral domain optical coherence tomography (SD-OCT. The outcome measures included change in central macular thickness (CMT and best-corrected visual acuity (BCVA as well as structural alterations seen on OCT such as change in the height of cystoid spaces (CSs and sub-foveal serous retinal detachment (SSRD. The integrity of external limiting membrane and inner-outer segment junction was assessed at baseline and follow-up visits. Results: Mean age of the patients was 46.09 ± 15.66 years. The mean CMT decreased by 96 μm at 1-day, 231.64 μm at 1-week, 254.21 μm at 4 weeks and 249.14 μm at 12 weeks (P < 0.001 compared with baseline. BCVA improved from a baseline mean of 0.62 LogMAR units to 0.49 on day 1 to 0.31 at 24 weeks (P < 0.001. A decrease in the mean height of CS, that is, 133.28 μm from a baseline of 317.71 μm was noted on the 1 st day (P < 0.001. 4 eyes demonstrated the presence of CS at 4 weeks, 1 eye at 6 weeks and 3 eyes at 12 weeks. At baseline, 16 eyes (53.33% demonstrated the presence of SSRD. Among these, 11 eyes showed resolution of SSRD on day 1. SSRD resolved in all patients at 4 weeks and was maintained up to 24 weeks. Conclusions: Ozurdex ® implant improves the visual outcome of patients with recalcitrant uveitic CME. Reversibility of retinal changes may be possible following treatment with dexamethasone implant. Thus final visual outcome may be independent of pretreatment CMT, the height of CS or SSRD.

  3. Comparison of Scheimpflug imaging and spectral domain anterior segment optical coherence tomography for detection of narrow anterior chamber angles.

    Science.gov (United States)

    Grewal, D S; Brar, G S; Jain, R; Grewal, S P S

    2011-05-01

    To compare the performance of anterior chamber volume (ACV) and anterior chamber depth (ACD) obtained using Scheimpflug imaging with angle opening distance (AOD500) and trabecular-iris space area (TISA500) obtained using spectral domain anterior segment optical coherence tomography (SD-ASOCT) in detecting narrow angles classified using gonioscopy. In this prospective, cross-sectional observational study, 265 eyes of 265 consecutive patients underwent sequential Scheimpflug imaging, SD-ASOCT imaging, and gonioscopy. Correlations between gonioscopy grading, ACV, ACD, AOD500, and TISA500 were evaluated. Area under receiver operating characteristic curve (AUC), sensitivity, specificity, and likelihood ratios (LRs) were calculated to assess the performance of ACV, ACD, AOD500, and TISA500 in detecting narrow angles (defined as Shaffer grade ≤1 in all quadrants). SD-ASOCT images were obtained at the nasal and temporal quadrants only. Twenty-eight eyes (10.6%) were classified as narrow angles on gonioscopy. ACV correlated with gonioscopy grading (P<0.001) for temporal (r=0.204), superior (r=0.251), nasal (r=0.213), and inferior (r=0.236) quadrants. ACV correlated with TISA500 for nasal (r=0.135, P=0.029) and temporal (P=0.160, P=0.009) quadrants and also with AOD500 for nasal (r=0.498, P<0.001) and temporal (r=0.517, P<0.001) quadrants. For detection of narrow angles, ACV (AUC=0.935; 95% confidence interval (CI) =0.898-0.961) performed similar to ACD (AUC=0.88, P=0.06) and significantly better than AOD500 nasal (AUC=0.761, P=0.001), AOD500 temporal (AUC=0.808, P<0.001), TISA500 nasal (AUC=0.756, P<0.001), and TISA500 temporal (AUC=0.738, P<0.001). Using a cutoff of 113 mm(3), ACV had 90% sensitivity and 88% specificity for detecting narrow angles. Positive and negative LRs for ACV were 8.63 (95% CI=7.4-10.0) and 0.11 (95% CI=0.03-0.4), respectively. ACV measurements using Scheimpflug imaging outperformed AOD500 and TISA500 using SD-ASOCT for detecting narrow angles.

  4. THICKNESS OF THE MACULA, RETINAL NERVE FIBER LAYER, AND GANGLION CELL-INNER PLEXIFORM LAYER IN THE AGE-RELATED MACULAR DEGENERATION: The Repeatability Study of Spectral Domain Optical Coherence Tomography.

    Science.gov (United States)

    Shin, Il-Hwan; Lee, Woo-Hyuk; Lee, Jong-Joo; Jo, Young-Joon; Kim, Jung-Yeul

    2018-02-01

    To determine the repeatability of measuring the thickness of the central macula, retinal nerve fiber layer, and ganglion cell-inner plexiform layer (GC-IPL) using spectral domain optical coherence tomography (Cirrus HD-OCT) in eyes with age-related macular degeneration. One hundred and thirty-four eyes were included. The measurement repeatability was assessed by an experienced examiner who performed two consecutive measurements using a 512 × 128 macular cube scan and a 200 × 200 optic disk cube scan. To assess changes in macular morphology in patients with age-related macular degeneration, the patients were divided into the following three groups according to the central macular thickness (CMT): A group, CMT 300 μm. Measurement repeatability was assessed using test-retest variability, a coefficient of variation, and an intraclass correlation coefficient. The mean measurement repeatability for the central macular, retinal nerve fiber layer, and GC-IPL thickness was high in the B group. The mean measurement repeatability for both the central macula and retinal nerve fiber layer thickness was high in the A and C groups, but was lower for the GC-IPL thickness. The measurement repeatability for GC-IPL thickness was high in the B group, but low in the A group and in the C group. The automated measurement repeatability for GC-IPL thickness was significantly lower in patients with age-related macular degeneration with out of normal CMT range. The effect of changes in macular morphology should be considered when analyzing GC-IPL thicknesses in a variety of ocular diseases.

  5. Enhanced optical transmission through a star-shaped bull's eye at dual resonant-bands in UV and the visible spectral range.

    Science.gov (United States)

    Nazari, Tavakol; Khazaeinezhad, Reza; Jung, Woohyun; Joo, Boram; Kong, Byung-Joo; Oh, Kyunghwan

    2015-07-13

    Dual resonant bands in UV and the visible range were simultaneously observed in the enhanced optical transmission (EOT) through star-shaped plasmonic structures. EOTs through four types of polygonal bull's eyes with a star aperture surrounded by the concentric star grooves were analyzed and compared for 3, 4, 5, and 6 corners, using finite difference time domain (FDTD) method. In contrast to plasmonic resonances in the visible range, the UV-band resonance intensity was found to scale with the number of corners, which is related with higher order multipole interactions. Spectral positions and relative intensities of the dual resonances were analyzed parametrically to find optimal conditions to maximize EOT in UV-visible dual bands.

  6. Estimation of spectral kurtosis

    Science.gov (United States)

    Sutawanir

    2017-03-01

    Rolling bearings are the most important elements in rotating machinery. Bearing frequently fall out of service for various reasons: heavy loads, unsuitable lubrications, ineffective sealing. Bearing faults may cause a decrease in performance. Analysis of bearing vibration signals has attracted attention in the field of monitoring and fault diagnosis. Bearing vibration signals give rich information for early detection of bearing failures. Spectral kurtosis, SK, is a parameter in frequency domain indicating how the impulsiveness of a signal varies with frequency. Faults in rolling bearings give rise to a series of short impulse responses as the rolling elements strike faults, SK potentially useful for determining frequency bands dominated by bearing fault signals. SK can provide a measure of the distance of the analyzed bearings from a healthy one. SK provides additional information given by the power spectral density (psd). This paper aims to explore the estimation of spectral kurtosis using short time Fourier transform known as spectrogram. The estimation of SK is similar to the estimation of psd. The estimation falls in model-free estimation and plug-in estimator. Some numerical studies using simulations are discussed to support the methodology. Spectral kurtosis of some stationary signals are analytically obtained and used in simulation study. Kurtosis of time domain has been a popular tool for detecting non-normality. Spectral kurtosis is an extension of kurtosis in frequency domain. The relationship between time domain and frequency domain analysis is establish through power spectrum-autocovariance Fourier transform. Fourier transform is the main tool for estimation in frequency domain. The power spectral density is estimated through periodogram. In this paper, the short time Fourier transform of the spectral kurtosis is reviewed, a bearing fault (inner ring and outer ring) is simulated. The bearing response, power spectrum, and spectral kurtosis are plotted to

  7. Experimental study of the use of multiband acousto-optic filters for spectral encoding / decoding the optical signals

    International Nuclear Information System (INIS)

    Proklov, V V; Byshevski-Konopko, O A; Filatov, A L; Lugovskoi, A V; Pisarevsky, Yu V

    2016-01-01

    A prototype of the acousto-optic (AO) decoder of optical signals is created on the base of the multiband AO filter. The joint work of the decoder with the developed previously AO coder has been verified experimentally. The main qualitative and quantitate characteristics of the spectral coding and decoding by Walsh sequences of the industrial LED radiation in the near infrared range are investigated. It is shown, that in the proposed data transmission system realization Signal-to-Interference Ratio (SIR) is not less than 13 dB. (paper)

  8. FY1995 ultrafast photonic devices using dielectric domain superlattice; 1995 nendo yudentai domain chokoshi wo mochiita chokosoku photonic device

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-03-31

    All optical wavelength conversion around 1550nm is of great importance for the wavelength division multiplexing optical communication system. A dielectric domain superlattice, which has a periodically domain inverted structure, has a wide potential for the various nonlinear interactions such as second harmonic generation (SHG) and difference frequency generation (DFG). The purpose of our research is to establish the theoretical bases and fabrication processes of the guided-wave wavelength converter based on the DFG by domain-inverted LiTaO{sub 3}. We have investigated basic characteristics of guided-wave DFG devices and developed the domain-inversion process by an electric field poling utilizing a liquid electrolyte consisting of LiCI in deionized water as a electrode for applying the electric field to LiTaO{sub 3} substrate. By controlling the injection current for the domain inversion precisely, we fabricated successfully uniform domain-inverted structures. 0.5mm-thick domain-inverted LiTaO{sub 3} of 7.8, 17.2 and 21.3 {mu}m periods and 0.5 duty ratio were obtained by optimizing electrode structure and the domain-inversion process. Waveguide structures can increase the conversion efficiency of DFG by several orders of magnitude over bulk interactions. We have also developed waveguide fabrication process for the domain-inverted LiTaO{sub 3} substrate. Low loss proton-exchanged waveguides were formed by annealed proton exchange technique without a degradation of the domain inversion structure. Domain-controlled nonlinear optics by designing the ferroelectric domain structure of LiTaO{sub 3} and LiNbO{sub 3} make it possible to extend all the spectral range from ultra-violet to far-infrared and THz wave region. (NEDO)

  9. Correlation between Spectral Optical Coherence Tomography and Fundus Autofluorescence at the margins of Geographic Atrophy

    Science.gov (United States)

    Brar, Manpreet; Kozak, Igor; Cheng, Lingyun; Bartsch, Dirk-Uwe G.; Yuson, Ritchie; Nigam, Nitin; Oster, Stephen F.; Mojana, Francesca; Freeman, William R.

    2009-01-01

    Purpose We studied the appearance of margins of Geographic atrophy in high- resolution optical coherence tomography (OCT) images and correlate those changes with fundus autofluorescence imaging. Design Retrospective observational case study. Methods Patients with geographic atrophy secondary to dry age related macular degeneration (ARMD) were assessed by means of Spectral Domain OCT (Spectralis HRA/OCT; Heidelberg Engineering, Heidelberg, Germany or OTI, Inc, Toronto, Canada) as well as Autofluoresence Imaging (HRA or Spectralis Heidelberg Engineering, Heidelberg, Germany): The outer retinal layer alterations were analyzed in the junctional zone between normal retina and atrophic retina, and correlated with corresponding fundus autofluorescence. Results 23 eyes of 16 patients aged between 62 years to 96 years were examined. There was a significant association between OCT findings and the fundus autofluorescence findings(r=0.67, pautofluorescence; Smooth margins on OCT correspond significantly to normal fundus autofluorescence. (Kappa-0.7348, pautofluorescence; secondary to increased lipofuscin may together serve as determinants of progression of geographic atrophy. PMID:19541290

  10. Incoherent Optical Frequency Domain Reflectometry for Distributed Thermal Sensing

    DEFF Research Database (Denmark)

    Karamehmedovic, Emir

    2006-01-01

    comprising a pump laser, optical filters, optical fibre and photo-detectors are presented. Limitations, trade-offs and optimisation processes are described for setups having different specifications with respect to range, resolution and accuracy. The analysis is conducted using computer simulation programs...... developed and implemented in Matlab. The computer model is calibrated and tested, and describes the entire system with high precision. Noise analysis and digital processing of the detected signal are discussed as well. An equation describing the standard deviation of the measured temperature is derived......This thesis reports the main results from an investigation of a fibre-optic distributed temperature sensor based on spontaneous Raman scattering. The technique used for spatial resolving is the incoherent optical frequency domain reflectometry, where a pump laser is sine modulated with a stepwise...

  11. Spectral triangulation molecular contrast optical coherence tomography with indocyanine green as the contrast agent

    OpenAIRE

    Yang, Changhuei; McGuckin, Laura E. L.; Simon, John D.; Choma, Michael A.; Applegate, Brian E.; Izatt, Joseph A.

    2004-01-01

    We report a new molecular contrast optical coherence tomography (MCOCT) implementation that profiles the contrast agent distribution in a sample by measuring the agent's spectral differential absorption. The method, spectra triangulation MCOCT, can effectively suppress contributions from spectrally dependent scatterings from the sample without a priori knowledge of the scattering properties. We demonstrate molecular imaging with this new MCOCT modality by mapping the distribution of indocyani...

  12. A New Statistical Approach to the Optical Spectral Variability in Blazars

    Directory of Open Access Journals (Sweden)

    Jose A. Acosta-Pulido

    2016-12-01

    Full Text Available We present a spectral variability study of a sample of about 25 bright blazars, based on optical spectroscopy. Observations cover the period from the end of 2008 to mid 2015, with an approximately monthly cadence. Emission lines have been identified and measured in the spectra, which permits us to classify the sources into BL Lac-type or FSRQs, according to the commonly used EW limit. We have obtained synthetic photometry and produced colour-magnitude diagrams which show different trends associated with the object classes: generally, BL Lacs tend to become bluer when brighter and FSRQs become redder when brighter, although several objects exhibit both trends, depending on brightness. We have also applied a pattern recognition algorithm to obtain the minimum number of physical components which can explain the variability of the optical spectrum. We have used NMF (Non-Negative Matrix Factorization instead of PCA (Principal Component Analysis to avoid un-realistic negative components. For most targets we found that 2 or 3 meta-components are enough to explain the observed spectral variability.

  13. Handbook of coherent domain optical methods biomedical diagnostics, environmental and material science

    CERN Document Server

    2004-01-01

    For the first time in one set of books, coherent-domain optical methods are discussed in the framework of various applications, which are characterized by a strong light scattering. A few chapters describe basic research containing the updated results on coherent and polarized light non-destructive interactions with a scattering medium, in particular, diffraction, interference, and speckle formation at multiple scattering. These chapters allow for understanding coherent-domain diagnostic techniques presented in later chapters. A large portion of Volume I is dedicated to analysis of various aspects of optical coherence tomography (OCT) - a very new and growing field of coherent optics. Two chapters on laser scanning confocal microscopy give insight to recent extraordinary results on in vivo imaging and compare the possibilities and achievements of confocol, excitation multiphoton, and OCT microscopy. This two volume reference contains descriptions of holography, interferometry and optical heterodyning techniqu...

  14. Spectral phase shift and residual angular dispersion of an accousto-optic programme dispersive filter

    International Nuclear Information System (INIS)

    Boerzsoenyi, A.; Meroe, M.

    2010-01-01

    Complete text of publication follows. There is an increasing demand for active and precise dispersion control of ultrashort laser pulses. In chirped pulse amplification (CPA) laser systems, the dispersion of the optical elements of the laser has to be compensated at least to the fourth order to obtain high temporal contrast compressed pulses. Nowadays the most convenient device for active and programmable control of spectral phase and amplitude of broadband laser pulses is the acousto-optic programmable dispersive filter (AOPDF), claimed to be able to adjust the spectral phase up to the fourth order. Although it has been widely used, surprisingly enough there has been only a single, low resolution measurement reported on the accuracy of the induced spectral phase shift of the device. In our paper we report on the first systematic experiment aiming at the precise characterization of an AOPDF device. In the experiment the spectral phase shift of the AOPDF device was measured by spectrally and spatially resolved interferometry, which is especially powerful tool to determine small dispersion values with high accuracy. Besides the spectral phase dispersion, we measured both the propagation direction angular dispersion (PDAD) and the phase front angular dispersion (PhFAD). Although the two quantities are equal for plane waves, there may be noticeable difference for Gaussian pulses. PDAD was determined simply by focusing the beam on the slit of an imaging spectrograph, while PhFAD was measured by the use of an inverted Mach-Zehnder interferometer and an imaging spectrograph. In the measurements, the spectral phase shift and both types of angular dispersion have been recorded upon the systematic change of all the accessible functions of the acousto-optic programmable dispersive filter. The measured values of group delay dispersion (GDD) and third order dispersion (TOD) have been found to agree with the preset values within the error of the measurement (1 fs 2 and 10 fs 3

  15. Optic Disc Pit with Sectorial Retinitis Pigmentosa

    OpenAIRE

    Balikoglu-Yilmaz, Melike; Taskapili, Muhittin; Yilmaz, Tolga; Teke, Mehmet Yasin

    2013-01-01

    Sectorial retinitis pigmentosa (RP) and optic disc pit (ODP) are rare clinical conditions. We present a 40-year-old woman with a history of mild night blindness and decreased vision in the right eye for about 5 years. Fundus examination revealed retinal pigmentary changes in the superior and inferotemporal sectors covering the macula and reduced arterial calibre and ODP at the temporal edge of the optic disc. In addition, fundus autofluorescence, spectral-domain optical coherence tomography, ...

  16. Alterations of the outer retina in non-arteritic anterior ischaemic optic neuropathy detected using spectral-domain optical coherence tomography.

    Science.gov (United States)

    Ackermann, Philipp; Brachert, Maike; Albrecht, Philipp; Ringelstein, Marius; Finis, David; Geerling, Gerd; Aktas, Orhan; Guthoff, Rainer

    2017-07-01

    A characteristic disease pattern may be reflected by retinal layer thickness changes in non-arteritic anterior ischaemic optic neuropathy measured using spectraldomain optical coherence tomography. Retinal layer segmentation is enabled by advanced software. In this study, retinal layer thicknesses in acute and chronic non-arteritic anterior ischaemic optic neuropathy were compared. A single-centre cross-sectional analysis was used. A total of 27 patients (20 age-matched healthy eyes) were included: 14 with acute (optic neuropathy. Macular volume and 12° peripapillary ring optical coherence tomography scans were used. The peripapillary thicknesses of the following layers were determined by manual segmentation: retinal nerve fibres, ganglion cells + inner plexiform layer, inner nuclear layer + outer plexiform layer, outer nuclear layer + inner segments of the photoreceptors and outer segments of the photoreceptors to Bruch's membrane. Macular retinal layer thicknesses were automatically determined in volume cubes centred on the fovea. Peripapillary retinal swelling in acute nonarteritic anterior ischaemic optic neuropathy was attributable to retinal nerve fibre layer, ganglion cell layer/inner plexiform layer and outer nuclear layer/segments of the photoreceptors thickening. In chronic cases, peripapillary retinal nerve fibre layer, macular ganglion cell layer and inner plexiform layer thinning were observed. In acute non-arteritic anterior ischaemic optic neuropathy, the inner and outer peripapillary retinal layers are affected by thickness changes. In chronic cases, atrophy of the ganglion cells and their axons and dendrites is evident by inner retinal layer thinning. © 2017 Royal Australian and New Zealand College of Ophthalmologists.

  17. Potential of remote sensing of cirrus optical thickness by airborne spectral radiance measurements at different sideward viewing angles

    OpenAIRE

    Wolf, Kevin; Ehrlich, André; Hüneke, Tilman; Pfeilsticker, Klaus; Werner, Frank; Wirth, Martin; Wendisch, Manfred

    2017-01-01

    Spectral radiance measurements collected in nadir and sideward viewing directions by two airborne passive solar remote sensing instruments, the Spectral Modular Airborne Radiation measurement sysTem (SMART) and the Differential Optical Absorption Spectrometer (mini-DOAS), are used to compare the remote sensing results of cirrus optical thickness τ. The comparison is based on a sensitivity study using radiative transfer simulations (RTS) and on data obtained during three airb...

  18. Dynamic terahertz spectroscopy of gas molecules mixed with unwanted aerosol under atmospheric pressure using fibre-based asynchronous-optical-sampling terahertz time-domain spectroscopy

    Science.gov (United States)

    Hsieh, Yi-Da; Nakamura, Shota; Abdelsalam, Dahi Ghareab; Minamikawa, Takeo; Mizutani, Yasuhiro; Yamamoto, Hirotsugu; Iwata, Tetsuo; Hindle, Francis; Yasui, Takeshi

    2016-06-01

    Terahertz (THz) spectroscopy is a promising method for analysing polar gas molecules mixed with unwanted aerosols due to its ability to obtain spectral fingerprints of rotational transition and immunity to aerosol scattering. In this article, dynamic THz spectroscopy of acetonitrile (CH3CN) gas was performed in the presence of smoke under the atmospheric pressure using a fibre-based, asynchronous-optical-sampling THz time-domain spectrometer. To match THz spectral signatures of gas molecules at atmospheric pressure, the spectral resolution was optimized to 1 GHz with a measurement rate of 1 Hz. The spectral overlapping of closely packed absorption lines significantly boosted the detection limit to 200 ppm when considering all the spectral contributions of the numerous absorption lines from 0.2 THz to 1 THz. Temporal changes of the CH3CN gas concentration were monitored under the smoky condition at the atmospheric pressure during volatilization of CH3CN droplets and the following diffusion of the volatilized CH3CN gas without the influence of scattering or absorption by the smoke. This system will be a powerful tool for real-time monitoring of target gases in practical applications of gas analysis in the atmospheric pressure, such as combustion processes or fire accident.

  19. Power Spectral Density Specification and Analysis of Large Optical Surfaces

    Science.gov (United States)

    Sidick, Erkin

    2009-01-01

    The 2-dimensional Power Spectral Density (PSD) can be used to characterize the mid- and the high-spatial frequency components of the surface height errors of an optical surface. We found it necessary to have a complete, easy-to-use approach for specifying and evaluating the PSD characteristics of large optical surfaces, an approach that allows one to specify the surface quality of a large optical surface based on simulated results using a PSD function and to evaluate the measured surface profile data of the same optic in comparison with those predicted by the simulations during the specification-derivation process. This paper provides a complete mathematical description of PSD error, and proposes a new approach in which a 2-dimentional (2D) PSD is converted into a 1-dimentional (1D) one by azimuthally averaging the 2D-PSD. The 1D-PSD calculated this way has the same unit and the same profile as the original PSD function, thus allows one to compare the two with each other directly.

  20. In vivo sweat film layer thickness measured with Fourier-domain optical coherence tomography

    CSIR Research Space (South Africa)

    Jonathan, E

    2008-01-01

    Full Text Available s Centre form the f th s pr t fi d id Keywords: Fourier-domain optical coherence tomography; Human sweat secretion; Sweat gland; Sweat duct; Hyperhidrosis growing list of triggers include cancer, glucose control disorder, mental stress, social..., that is, the gland, duct and pore(s). However, due to a slow imaging time, COCT is largely restricted to morphometry of human tissue and thickness measurement of biologic and biologic samples [12,13]. ARTICLE IN PRESS Fourier-domain optical coherence...

  1. Spectral shaping of an all-fiber torsional acousto-optic tunable filter.

    Science.gov (United States)

    Ko, Jeakwon; Lee, Kwang Jo; Kim, Byoung Yoon

    2014-12-20

    Spectral shaping of an all-fiber torsional acousto-optic (AO) tunable filter is studied. The technique is based on the axial modulation of AO coupling strength along a highly birefringent optical fiber, which is achieved by tailoring the outer diameter of the fiber along its propagation axis. Two kinds of filter spectral shaping schemes-Gaussian apodization and matched filtering with triple resonance peaks-are proposed and numerically investigated under realistic experimental conditions: at the 50-cm-long AO interaction length of the fiber and at half of the original fiber diameter as the minimum thickness of the tailored fiber section. The results show that the highest peak of sidelobe spectra in filter transmission is suppressed from 11.64% to 0.54% via Gaussian modulation of the AO coupling coefficient (κ). Matched filtering with triple resonance peaks operating with a single radio frequency signal is also achieved by cosine modulation of κ, of which the modulation period determines the spectral distance between two satellite peaks located in both wings of the main resonance peak. The splitting of two satellite peaks in the filter spectra reaches 48.2 nm while the modulation period varies from 7.7 to 50 cm. The overall peak power of two satellite resonances is calculated to be 22% of the main resonance power. The results confirm the validity and practicality of our approach, and we predict robust and stable operation of the designed all-fiber torsional AO filters.

  2. Optical study of the skeletal muscle during exercise with a second-generation frequency-domain tissue oximeter

    Science.gov (United States)

    Franceschini, Maria-Angela; Wallace, Don J.; Barbieri, Beniamino B.; Fantini, Sergio; Mantulin, William W.; Pratesi, Simone; Donzelli, Gian Paolo; Gratton, Enrico

    1997-08-01

    We present a re-engineered frequency-domain tissue oximeter operating in the near-infrared spectral region. This instrument is based on the multi-distance measurement protocol, which we have implemented in our original design by multiplexing multiple light sources. The new instrument uses intensity modulated (110 MHz) laser diodes emitting at 750 and 840 nm. The laser diodes are coupled to glass optical fibers (600 micrometer core diameter). The average light intensity delivered to the tissue is about 3 mW. The multiplexing electronics are based on solid state switches that allow for acquisition times per point as short as tens of milliseconds. Our tests on phantoms and in vivo with the new oximeter have shown significant improvement in terms of stability, reliability, and reproducibility with respect to the original prototype. Furthermore, by using optical fibers we achieve a high versatility in the design of the measuring probe, permitting custom design for various tissue contours and different measurements. To verify the improved performance of the new oximeter, we have performed an in vivo test consisting of monitoring the hemoglobin saturation (Y) and concentration (THC) on the calf of 18 healthy volunteers during walking and running routines.

  3. Comparison of perceptual properties of auditory streaming between spectral and amplitude modulation domains.

    Science.gov (United States)

    Yamagishi, Shimpei; Otsuka, Sho; Furukawa, Shigeto; Kashino, Makio

    2017-07-01

    The two-tone sequence (ABA_), which comprises two different sounds (A and B) and a silent gap, has been used to investigate how the auditory system organizes sequential sounds depending on various stimulus conditions or brain states. Auditory streaming can be evoked by differences not only in the tone frequency ("spectral cue": ΔF TONE , TONE condition) but also in the amplitude modulation rate ("AM cue": ΔF AM , AM condition). The aim of the present study was to explore the relationship between the perceptual properties of auditory streaming for the TONE and AM conditions. A sequence with a long duration (400 repetitions of ABA_) was used to examine the property of the bistability of streaming. The ratio of feature differences that evoked an equivalent probability of the segregated percept was close to the ratio of the Q-values of the auditory and modulation filters, consistent with a "channeling theory" of auditory streaming. On the other hand, for values of ΔF AM and ΔF TONE evoking equal probabilities of the segregated percept, the number of perceptual switches was larger for the TONE condition than for the AM condition, indicating that the mechanism(s) that determine the bistability of auditory streaming are different between or sensitive to the two domains. Nevertheless, the number of switches for individual listeners was positively correlated between the spectral and AM domains. The results suggest a possibility that the neural substrates for spectral and AM processes share a common switching mechanism but differ in location and/or in the properties of neural activity or the strength of internal noise at each level. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

  4. Conjugation of fiber-coupled wide-band light sources and acousto-optical spectral elements

    Science.gov (United States)

    Machikhin, Alexander; Batshev, Vladislav; Polschikova, Olga; Khokhlov, Demid; Pozhar, Vitold; Gorevoy, Alexey

    2017-12-01

    Endoscopic instrumentation is widely used for diagnostics and surgery. The imaging systems, which provide the hyperspectral information of the tissues accessible by endoscopes, are particularly interesting and promising for in vivo photoluminescence diagnostics and therapy of tumour and inflammatory diseases. To add the spectral imaging feature to standard video endoscopes, we propose to implement acousto-optical (AO) filtration of wide-band illumination of incandescent-lamp-based light sources. To collect maximum light and direct it to the fiber-optic light guide inside the endoscopic probe, we have developed and tested the optical system for coupling the light source, the acousto-optical tunable filter (AOTF) and the light guide. The system is compact and compatible with the standard endoscopic components.

  5. Visualizing Macular Structures During Membrane Peeling Surgery With an Intraoperative Spectral-Domain Optical Coherence Tomography Device.

    Science.gov (United States)

    Leisser, Christoph; Hackl, Christoph; Hirnschall, Nino; Luft, Nikolaus; Döller, Birgit; Draschl, Petra; Rigal, Karl; Findl, Oliver

    2016-04-01

    The aim of this study was to examine the quality of intraoperative visualization of the posterior hyaloid, epiretinal membrane (ERM), inner limiting membrane (ILM), and hyporeflective subfoveal zone with a commercially available, microscope-integrated spectral-domain OCT setup (mi-SD-OCT) (Rescan 700; Carl Zeiss Meditec AG, Germany). Twenty patients prospectively scheduled for pars plana vitrectomy with membrane peeling due to an idiopathic ERM were included. Standard 23-gauge, three-port pars plana vitrectomy with membrane peeling and staining of the ERM with a trypan blue-based chromovitrectomy dye was performed in all cases. Intraoperative SD-OCT was performed before and after peeling and visualization of the posterior hyaloid, ERM, ILM, and presence of subfoveal hyporeflective zones were examined. OCT follow-ups were performed 2 days and 3 months after surgery. The study was approved by the local ethics committee of the city of Vienna. Successful intraoperative visualization of ERM by mi-SD-OCT was possible in all cases. The posterior hyaloid and ILM could not be seen in the mi-SD-OCT scans, whereas an intraoperative subfoveal hyporeflective zone presented in 35% of cases. In 12.5% an independent subfoveal hyporeflective zone presented postoperatively. Visual acuity improved in 93.8% of patients after surgery. mi-SD-OCT appears to be a valuable tool for intraoperative visualization of the ERM and offers immediate visualization of retinal anatomy during peeling. Therefore, it adds to the understanding of intraoperative traumatic changes due to the peeling procedure. Copyright 2016, SLACK Incorporated.

  6. Simultaneous Fluorescein Angiography and Spectral Domain Optical Coherence Tomography Correlate Retinal Thickness Changes to Vascular Abnormalities in an In Vivo Mouse Model of Retinopathy of Prematurity

    Directory of Open Access Journals (Sweden)

    Olachi J. Mezu-Ndubuisi

    2017-01-01

    Full Text Available Background. Retinopathy of prematurity (ROP is a condition of abnormal retinal vascular development (RVD in premature infants. Fluorescein angiography (FA has depicted phases (early, mid, late, and mature of RVD in oxygen-induced retinopathy (OIR mice. We sought to establish the relationship between retinal structural and vascular changes using simultaneous FA and spectral domain optical coherence tomography (SD-OCT. Method. 63 mice were exposed to 77% oxygen at postnatal day 7 (P7 for 5 days, while 63 mice remained in room air (RA. Total retinal thickness (TRT, inner retinal thickness (IRT, and outer retinal thickness (ORT were calculated at early (P19, mid (P24, late (P32, and mature (P47 phases of RVD. Results. TRT was reduced in OIR (162.66 ± 17.75 μm, n=13 compared to RA mice at P19 (197.57 ± 3.49 μm, n=14, P24, P32, and P49 (P0.05. IRT was reduced in OIR (71.60 ± 17.14 μm compared to RA (103.07 ± 3.47 μm mice at P19 and all ages (P<0.0001. Conclusion. We have shown the spatial and temporal relationship between retinal structure and vascular development in OIR. Significant inner retinal thinning in OIR mice persisted despite revascularization of the capillary network; further studies will elucidate its functional implications in ROP.

  7. EFFECT OF INTRAVITREAL RANIBIZUMAB ON GANGLION CELL COMPLEX AND PERIPAPILLARY RETINAL NERVE FIBER LAYER IN NEOVASCULAR AGE-RELATED MACULAR DEGENERATION USING SPECTRAL DOMAIN OPTICAL COHERENCE TOMOGRAPHY.

    Science.gov (United States)

    Zucchiatti, Ilaria; Cicinelli, Maria V; Parodi, Maurizio Battaglia; Pierro, Luisa; Gagliardi, Marco; Accardo, Agostino; Bandello, Francesco

    2017-07-01

    To analyze the changes in ganglion cell complex and peripapillary retinal nerve fiber layer thickness, in central macular thickness and choroidal thickness on spectral domain optical coherence tomography in patients with neovascular age-related macular degeneration treated with intravitreal ranibizumab injections. All consecutive patients with untreated neovascular age-related macular degeneration received loading phase of three monthly intravitreal ranibizumab, followed by retreatments on a pro re nata protocol for 12 months. changes in ganglion cell complex and retinal nerve fiber layer at the end of follow-up. Secondary outcome: changes in best-corrected visual acuity, central macular thickness, and choroidal thickness at the end of follow-up. Choroidal thickness was measured at 500 μm, 1000 μm, and 1,500 μm intervals nasally, temporally, superiorly, and inferiorly to the fovea, respectively, on horizontal and vertical line scans centered on the fovea. Twenty-four eyes were included. Ganglion cell complex and peripapillary retinal nerve fiber layer thickness did not show statistically significant changes through 12 months (55.6 ± 18.5 and 81.9 ± 9.9 μm at baseline, 52.7 ± 19.3 and 84.6 ± 15.5 μm at month 12, P > 0.05). Central macular thickness showed progressive decrease from baseline to month 12, with maximum reduction at month 3 (P macular thickness was significantly reduced at the end of treatment. Further studies, with larger sample, longer follow-up, and greater number of injections, are warranted.

  8. 2-μm optical time domain reflectometry measurements from novel Al-, Ge-, CaAlSi- doped and standard single-mode fibers

    Science.gov (United States)

    Rodriguez-Novelo, J. C.; Sanchez-Nieves, J. A.; Sierra-Calderon, A.; Sanchez-Lara, R.; Alvarez-Chavez, J. A.

    2017-08-01

    The development of novel Al-, Ge- doped and un-doped standard single mode fibers for future optical communication at 2μm requires the integration of, among other pieces of equipment, an optical time domain reflectometry (OTDR) technique for precise spectral attenuation characterization, including the well-known cut-back method. The integration of a state of the art OTDR at 2μm could provide valuable attenuation information from the aforementioned novel fibers. The proposed setup consists of a 1.7 mW, 1960nm pump source, a 30 dB gain Thulium doped fibre amplifier at 2μm, an 0.8mm focal length lens with a 0.5 NA, a 30 MHz acusto-optic modulator, a 3.1 focal length lens with a 0.68NA, an optical circulator at 2μm, an InGaAs photodetector for 1.2 nm-2.6 nm range, a voltage amplifier and an oscilloscope. The propagated pulse rate is 50 KHz, with 500 ns, 200 ns, 100 ns and 50 ns pulse widths. Attenuation versus novel fibers types for lengths ranging from 400- to 1000- meter samples were obtained using the proposed setup.

  9. Reduced timing Sensitivity in all-optical switching using flat-top control pulses obtained by the optical fourier transform technique

    DEFF Research Database (Denmark)

    Oxenløwe, Leif Katsuo; Galili, Michael; Mulvad, Hans Christian Hansen

    2006-01-01

    into the time domain, referred to as the optical Fourier transform technique. A 3 ps flat-top pulse derived from a 3 nm wide square filter is obtained, and used to gate an all-optical OTDM demultiplexer, yielding an error-free timing jitter tolerance of 3 ps for 80 Gb/s and 160 Gb/s data signals.......For high-speed serial data, timing tolerance is crucial for switching and regeneration. We propose a novel scheme to generate flat-top pulses, for use as gating control pulses. The scheme relies on spectral shaping by a square-shaped filter, followed by a linear transformation of the spectral shape...

  10. Universal dispersion model for characterization of optical thin films over wide spectral range: Application to magnesium fluoride

    Science.gov (United States)

    Franta, Daniel; Nečas, David; Giglia, Angelo; Franta, Pavel; Ohlídal, Ivan

    2017-11-01

    Optical characterization of magnesium fluoride thin films is performed in a wide spectral range from far infrared to extreme ultraviolet (0.01-45 eV) utilizing the universal dispersion model. Two film defects, i.e. random roughness of the upper boundaries and defect transition layer at lower boundary are taken into account. An extension of universal dispersion model consisting in expressing the excitonic contributions as linear combinations of Gaussian and truncated Lorentzian terms is introduced. The spectral dependencies of the optical constants are presented in a graphical form and by the complete set of dispersion parameters that allows generating tabulated optical constants with required range and step using a simple utility in the newAD2 software package.

  11. Distributed Optical Fiber Sensors Based on Optical Frequency Domain Reflectometry: A review.

    Science.gov (United States)

    Ding, Zhenyang; Wang, Chenhuan; Liu, Kun; Jiang, Junfeng; Yang, Di; Pan, Guanyi; Pu, Zelin; Liu, Tiegen

    2018-04-03

    Distributed optical fiber sensors (DOFS) offer unprecedented features, the most unique one of which is the ability of monitoring variations of the physical and chemical parameters with spatial continuity along the fiber. Among all these distributed sensing techniques, optical frequency domain reflectometry (OFDR) has been given tremendous attention because of its high spatial resolution and large dynamic range. In addition, DOFS based on OFDR have been used to sense many parameters. In this review, we will survey the key technologies for improving sensing range, spatial resolution and sensing performance in DOFS based on OFDR. We also introduce the sensing mechanisms and the applications of DOFS based on OFDR including strain, stress, vibration, temperature, 3D shape, flow, refractive index, magnetic field, radiation, gas and so on.

  12. Prediction of meat spectral patterns based on optical properties and concentrations of the major constituents.

    Science.gov (United States)

    ElMasry, Gamal; Nakauchi, Shigeki

    2016-03-01

    A simulation method for approximating spectral signatures of minced meat samples was developed depending on concentrations and optical properties of the major chemical constituents. Minced beef samples of different compositions scanned on a near-infrared spectroscopy and on a hyperspectral imaging system were examined. Chemical composition determined heuristically and optical properties collected from authenticated references were simulated to approximate samples' spectral signatures. In short-wave infrared range, the resulting spectrum equals the sum of the absorption of three individual absorbers, that is, water, protein, and fat. By assuming homogeneous distributions of the main chromophores in the mince samples, the obtained absorption spectra are found to be a linear combination of the absorption spectra of the major chromophores present in the sample. Results revealed that developed models were good enough to derive spectral signatures of minced meat samples with a reasonable level of robustness of a high agreement index value more than 0.90 and ratio of performance to deviation more than 1.4.

  13. Brillouin Scattering Spectrum Analysis Based on Auto-Regressive Spectral Estimation

    Science.gov (United States)

    Huang, Mengyun; Li, Wei; Liu, Zhangyun; Cheng, Linghao; Guan, Bai-Ou

    2018-06-01

    Auto-regressive (AR) spectral estimation technology is proposed to analyze the Brillouin scattering spectrum in Brillouin optical time-domain refelectometry. It shows that AR based method can reliably estimate the Brillouin frequency shift with an accuracy much better than fast Fourier transform (FFT) based methods provided the data length is not too short. It enables about 3 times improvement over FFT at a moderate spatial resolution.

  14. Brillouin Scattering Spectrum Analysis Based on Auto-Regressive Spectral Estimation

    Science.gov (United States)

    Huang, Mengyun; Li, Wei; Liu, Zhangyun; Cheng, Linghao; Guan, Bai-Ou

    2018-03-01

    Auto-regressive (AR) spectral estimation technology is proposed to analyze the Brillouin scattering spectrum in Brillouin optical time-domain refelectometry. It shows that AR based method can reliably estimate the Brillouin frequency shift with an accuracy much better than fast Fourier transform (FFT) based methods provided the data length is not too short. It enables about 3 times improvement over FFT at a moderate spatial resolution.

  15. Reliability of Entire Corneal Thickness Mapping in Normal Post-Laser in situ Keratomileusis and Keratoconus Eyes Using Long Scan Depth Spectral Domain Optical Coherence Tomography.

    Science.gov (United States)

    Xu, Zhe; Chen, Sisi; Yang, Chun; Huang, Shenghai; Shen, Meixiao; Wang, Yuanyuan

    2018-01-01

    To investigate the repeatability and reproducibility of mapping the entire corneal thickness using spectral domain optical coherence tomography (SD-OCT). Thirty normal eyes, 30 post-laser in situ keratomileusis (LASIK) surgery eyes, and 30 keratoconus eyes were analyzed. A custom-built long scan depth SD-OCT device was used to obtain entire corneal images. Ten-millimeter-diameter corneal thickness maps were generated by an automated segmentation algorithm. Intraclass correlation coefficients of repeatability (ICC1) and reproducibility (ICC2), and coefficients of repeatability (CoR1) and reproducibility (CoR2), were calculated to quantify the precision and accuracy of corneal pachymetry measurements using the Bland-Altman method. For SD-OCT measurements in healthy subjects, CoR1 and CoR2 were less than 5.00 and 5.53 μm. ICC1 and ICC2 were more than 0.997 and 0.996. For SD-OCT measurements in LASIK patients, CoR1 and CoR2 were less than 5.09 and 5.34 μm. ICC1 and ICC2 were more than 0.997 and 0.996. For SD-OCT measurements in keratoconus patients, CoR1 and CoR2 were less than 11.57 and 10.92 μm. ICC1 and ICC2 were more than 0.995 and 0.996. The measurements of corneal pachymetric mapping by long scan depth SD-OCT can be assessed over the entire corneal area with good repeatability and reproducibility. © 2017 S. Karger AG, Basel.

  16. Correlation between morphological characteristics in spectral-domain-optical coherence tomography, different functional tests and a patient's subjective handicap in acute central serous chorioretinopathy.

    Science.gov (United States)

    Gerendas, Bianca S; Kroisamer, Julia-Sophie; Buehl, Wolf; Rezar-Dreindl, Sandra M; Eibenberger, Katharina M; Pablik, Eleonore; Schmidt-Erfurth, Ursula; Sacu, Stefan

    2018-01-16

    The purpose of this study was to identify quantitatively measurable morphologic optical coherence tomography (OCT) characteristics in patients with an acute episode of central serous chorioretinopathy (CSC) and evaluate their correlation to functional and psychological variables for their use in daily clinical practice. Retinal thickness (RT), the height, area and volume of subretinal fluid (SRF)/pigment epithelium detachments were evaluated using the standardized procedures of the Vienna Reading Center. These morphologic characteristics were compared with functional variables [best-corrected visual acuity (BCVA), contrast sensitivity (CS), retinal sensitivity/microperimetry, fixation stability], and patients' subjective handicap from CSC using the National Eye Institute 25-item Visual Function Questionnaire (NEI VFQ-25). Data from 39 CSC patients were included in this analysis. Three different SRF height measures showed a high negative correlation (r = -0.7) to retinal sensitivity within the central 9°, which was also negatively correlated with SRF area and volume (r = -0.6). The CS score and fixation stability (fixation points within 2°) showed a moderate negative correlation (r = -0.4) with SRF height variables. Comparison of the subjective handicap with morphological characteristics in spectral-domain (SD)-OCT showed SRF height had the highest correlation (r = -0.4) with the subjective problems reported and overall NEI VFQ-25 score. In conclusion, SRF height measured in SD-OCT showed the best correlation with functional variables and patients' subjective handicap caused by the disease and therefore seems to be the best variable to look at in daily clinical routine. Even though area and volume also show a correlation, these cannot be so easily measured as height and are therefore not suggested for daily clinical routine. © 2018 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

  17. Optical protocols for terabit networks

    Science.gov (United States)

    Chua, P. L.; Lambert, J. L.; Morookian, J. M.; Bergman, L. A.

    1991-01-01

    This paper describes a new fiber-optic local area network technology providing 100X improvement over current technology, has full crossbar funtionality, and inherent data security. Based on optical code-division multiple access (CDMA), using spectral phase encoding/decoding of optical pulses, networking protocols are implemented entirely in the optical domain and thus conventional networking bottlenecks are avoided. Component and system issues for a proof-of-concept demonstration are discussed, as well as issues for a more practical and commercially exploitable system. Possible terrestrial and aerospace applications of this technology, and its impact on other technologies are explored. Some initial results toward realization of this concept are also included.

  18. Brain connectivity study of joint attention using frequency-domain optical imaging technique

    Science.gov (United States)

    Chaudhary, Ujwal; Zhu, Banghe; Godavarty, Anuradha

    2010-02-01

    Autism is a socio-communication brain development disorder. It is marked by degeneration in the ability to respond to joint attention skill task, from as early as 12 to 18 months of age. This trait is used to distinguish autistic from nonautistic populations. In this study, diffuse optical imaging is being used to study brain connectivity for the first time in response to joint attention experience in normal adults. The prefrontal region of the brain was non-invasively imaged using a frequency-domain based optical imager. The imaging studies were performed on 11 normal right-handed adults and optical measurements were acquired in response to joint-attention based video clips. While the intensity-based optical data provides information about the hemodynamic response of the underlying neural process, the time-dependent phase-based optical data has the potential to explicate the directional information on the activation of the brain. Thus brain connectivity studies are performed by computing covariance/correlations between spatial units using this frequency-domain based optical measurements. The preliminary results indicate that the extent of synchrony and directional variation in the pattern of activation varies in the left and right frontal cortex. The results have significant implication for research in neural pathways associated with autism that can be mapped using diffuse optical imaging tools in the future.

  19. Spectral interferometry including the effect of transparent thin films to measure distances and displacements

    International Nuclear Information System (INIS)

    Hlubina, P.

    2004-01-01

    A spectral-domain interferometric technique is applied for measuring mirror distances and displacements in a dispersive Michelson interferometer when the effect of transparent thin films coated onto the interferometer beam splitter and compensator is known. We employ a low-resolution spectrometer in two experiments with different amounts of dispersion in a Michelson interferometer that includes fused-silica optical sample. Knowing the thickness of the optical sample and the nonlinear phase function of the thin films, the positions of the interferometer mirror are determined precisely by a least-squares fitting of the theoretical spectral interferograms to the recorded ones. We compare the results of the processing that include and do not include the effect of transparent thin films (Author)

  20. Comparison of Ganglion Cell and Retinal Nerve Fiber Layer Thickness in Pigment Dispersion Syndrome, Pigmentary Glaucoma, and Healthy Subjects with Spectral-domain OCT.

    Science.gov (United States)

    Arifoglu, Hasan Basri; Simavli, Huseyin; Midillioglu, Inci; Berk Ergun, Sule; Simsek, Saban

    2017-01-01

    To evaluate the ganglion cell complex (GCC) and retinal nerve fiber layer (RNFL) thickness in pigment dispersion syndrome (PDS) and pigmentary glaucoma (PG) with RTVue spectral domain optical coherence tomography (SD-OCT). A total of 102 subjects were enrolled: 29 with PDS, 18 with PG, and 55 normal subjects. Full ophthalmic examination including visual field analysis was performed. SD-OCT was used to analyze GCC superior, GCC inferior, and average RNFL thickness. To compare the discrimination capabilities, the areas under the receiver operating characteristic curves were assessed. Superior GCC, inferior GCC, and RNFL thickness values of patients with PG were statistically signicantly lower than those of patients with PDS (p  0.05). The SD-OCT-derived GCC and RNFL thickness parameters can be useful to discriminate PG from both PDS and normal subjects.

  1. Multi-spectral optical absorption in substrate-free nanowire arrays

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Junpeng; Chia, Andrew; Boulanger, Jonathan; LaPierre, Ray, E-mail: lapierr@mcmaster.ca [Department of Engineering Physics, McMaster University, 1280 Main St. West, Hamilton, Ontario L8S 4L7 (Canada); Dhindsa, Navneet; Khodadad, Iman; Saini, Simarjeet [Department of Electrical and Computer Engineering, University of Waterloo, 200 University Ave West, Waterloo, Ontario N2L 3G1 (Canada); Waterloo Institute of Nanotechnology, University of Waterloo, 200 University Ave West, Waterloo, Ontario N2L 3G1 (Canada)

    2014-09-22

    A method is presented of fabricating gallium arsenide (GaAs) nanowire arrays of controlled diameter and period by reactive ion etching of a GaAs substrate containing an indium gallium arsenide (InGaP) etch stop layer, allowing the precise nanowire length to be controlled. The substrate is subsequently removed by selective etching, using the same InGaP etch stop layer, to create a substrate-free GaAs nanowire array. The optical absorptance of the nanowire array was then directly measured without absorption from a substrate. We directly observe absorptance spectra that can be tuned by the nanowire diameter, as explained with rigorous coupled wave analysis. These results illustrate strong optical absorption suitable for nanowire-based solar cells and multi-spectral absorption for wavelength discriminating photodetectors. The solar-weighted absorptance above the bandgap of GaAs was 94% for a nanowire surface coverage of only 15%.

  2. Potential of optical spectral transmission measurements for joint inflammation measurements in rheumatoid arthritis patients

    Science.gov (United States)

    Meier, A. J. Louise; Rensen, Wouter H. J.; de Bokx, Pieter K.; de Nijs, Ron N. J.

    2012-08-01

    Frequent monitoring of rheumatoid arthritis (RA) patients enables timely treatment adjustments and improved outcomes. Currently this is not feasible due to a shortage of rheumatologists. An optical spectral transmission device is presented for objective assessment of joint inflammation in RA patients, while improving diagnostic accuracy and clinical workflow. A cross-sectional, nonrandomized observational study was performed with this device. In the study, 77 proximal interphalangeal (PIP) joints in 67 patients have been analyzed. Inflammation of these PIP joints was also assessed by a rheumatologist with a score varying from 1 (not inflamed) to 5 (severely inflamed). Out of 77 measurements, 27 were performed in moderate to strongly inflamed PIP joints. Comparison between the clinical assessment and an optical measurement showed a correlation coefficient r=0.63, p<0.001, 95% CI [0.47, 0.75], and a ROC curve (AUC=0.88) that shows a relative good specificity and sensitivity. Optical spectral transmission measurements in a single joint correlate with clinical assessment of joint inflammation, and therefore might be useful in monitoring joint inflammation in RA patients.

  3. Adaptive optics imaging of the retina

    Directory of Open Access Journals (Sweden)

    Rajani Battu

    2014-01-01

    Full Text Available Adaptive optics is a relatively new tool that is available to ophthalmologists for study of cellular level details. In addition to the axial resolution provided by the spectral-domain optical coherence tomography, adaptive optics provides an excellent lateral resolution, enabling visualization of the photoreceptors, blood vessels and details of the optic nerve head. We attempt a mini review of the current role of adaptive optics in retinal imaging. PubMed search was performed with key words Adaptive optics OR Retina OR Retinal imaging. Conference abstracts were searched from the Association for Research in Vision and Ophthalmology (ARVO and American Academy of Ophthalmology (AAO meetings. In total, 261 relevant publications and 389 conference abstracts were identified.

  4. Ultra-high-speed optical serial-to-parallel data conversion by time-domain optical Fourier transformation in a silicon nanowire

    DEFF Research Database (Denmark)

    Mulvad, Hans Christian Hansen; Palushani, Evarist; Hu, Hao

    2011-01-01

    We demonstrate conversion from 64 × 10 Gbit/s optical timedivision multiplexed (OTDM) data to dense wavelength division multiplexed (DWDM) data with 25 GHz spacing. The conversion is achieved by time-domain optical Fourier transformation (OFT) based on four-wave mixing (FWM) in a 3.6 mm long...

  5. Distributed Optical Fiber Sensors Based on Optical Frequency Domain Reflectometry: A review

    Directory of Open Access Journals (Sweden)

    Zhenyang Ding

    2018-04-01

    Full Text Available Distributed optical fiber sensors (DOFS offer unprecedented features, the most unique one of which is the ability of monitoring variations of the physical and chemical parameters with spatial continuity along the fiber. Among all these distributed sensing techniques, optical frequency domain reflectometry (OFDR has been given tremendous attention because of its high spatial resolution and large dynamic range. In addition, DOFS based on OFDR have been used to sense many parameters. In this review, we will survey the key technologies for improving sensing range, spatial resolution and sensing performance in DOFS based on OFDR. We also introduce the sensing mechanisms and the applications of DOFS based on OFDR including strain, stress, vibration, temperature, 3D shape, flow, refractive index, magnetic field, radiation, gas and so on.

  6. Distributed Optical Fiber Sensors Based on Optical Frequency Domain Reflectometry: A review

    Science.gov (United States)

    Wang, Chenhuan; Liu, Kun; Jiang, Junfeng; Yang, Di; Pan, Guanyi; Pu, Zelin; Liu, Tiegen

    2018-01-01

    Distributed optical fiber sensors (DOFS) offer unprecedented features, the most unique one of which is the ability of monitoring variations of the physical and chemical parameters with spatial continuity along the fiber. Among all these distributed sensing techniques, optical frequency domain reflectometry (OFDR) has been given tremendous attention because of its high spatial resolution and large dynamic range. In addition, DOFS based on OFDR have been used to sense many parameters. In this review, we will survey the key technologies for improving sensing range, spatial resolution and sensing performance in DOFS based on OFDR. We also introduce the sensing mechanisms and the applications of DOFS based on OFDR including strain, stress, vibration, temperature, 3D shape, flow, refractive index, magnetic field, radiation, gas and so on. PMID:29614024

  7. [Research on symmetrical optical waveguide based surface plasmon resonance sensing with spectral interrogation].

    Science.gov (United States)

    Zhang, Yi-long; Liu, Le; Guo, Jun; Zhang, Peng-fei; Guo, Ji-hua; Ma, Hui; He, Yong-hong

    2015-02-01

    Surface plasmon resonance (SPR) sensors with spectral interrogation can adopt fiber to transmit light signals, thus leaving the sensing part separated, which is very convenient for miniaturization, remote-sensing and on-site analysis. Symmetrical optical waveguide (SOW) SPR has the same refractive index of the-two buffer media layers adjacent to the metal film, resulting in longer propagation distance, deeper penetration depth and better performance compared to conventional SPR In the present paper, we developed a symmetrical optical, waveguide (SOW) SPR sensor with wavelength interrogation. In the system, MgF2-Au-MgF2 film was used as SOW module for glucose sensing, and a fiber based light source and detection was used in the spectral interrogation. In the experiment, a refractive index resolution of 2.8 x 10(-7) RIU in fluid protocol was acquired. This technique provides advantages of high resolution and could have potential use in compact design, on-site analysis and remote sensing.

  8. Vibration sensing in flexible structures using a distributed-effect modal domain optical fiber sensor

    Science.gov (United States)

    Reichard, Karl M.; Lindner, Douglas K.; Claus, Richard O.

    1991-01-01

    Modal domain optical fiber sensors have recently been employed in the implementation of system identification algorithms and the closed-loop control of vibrations in flexible structures. The mathematical model of the modal domain optical fiber sensor used in these applications, however, only accounted for the effects of strain in the direction of the fiber's longitudinal axis. In this paper, we extend this model to include the effects of arbitrary stress. Using this sensor model, we characterize the sensor's sensitivity and dynamic range.

  9. Spectral dependence of third-order nonlinear optical properties in InN

    International Nuclear Information System (INIS)

    Ahn, H.; Lee, M.-T.; Chang, Y.-M.

    2014-01-01

    We report on the nonlinear optical properties of InN measured in a wide near-infrared spectral range with the femtosecond Z-scan technique. The above-bandgap nonlinear absorption in InN is found to originate from the saturation of absorption by the band-state-filling and its cross-section increases drastically near the bandgap energy. With below-bandgap excitation, the nonlinear absorption undergoes a transition from saturation absorption (SA) to reverse-SA (RSA), attributed to the competition between SA of band-tail states and two-photon-related RSA. The measured large nonlinear refractive index of the order of 10 −10 cm 2 /W indicates InN as a potential material for all-optical switching and related applications

  10. Measurements of spectral responses for developing fiber-optic pH sensor

    Science.gov (United States)

    Yoo, Wook Jae; Heo, Ji Yeon; Jang, Kyoung Won; Seo, Jeong Ki; Moon, Jin Soo; Park, Jang-Yeon; Park, Byung Gi; Cho, Seunghyun; Lee, Bongsoo

    2011-01-01

    In this study, we have fabricated a fiber-optic pH sensor, which is composed of a light source, a pH-sensing probe, plastic optical fibers and a spectrometer, for determining the degree of infection by Helicobacter pylori in the stomach. As pH indicators, phenol red and m-cresol purple are used, and pH liquid solutions are prepared by mixing phenol red or m-cresol purple solutions and various kinds of pH buffer solutions. The light emitted by a light source is guided by plastic optical fibers to the pH liquid solution, and the optical characteristic of a reflected light is changed according to the color variations of the pH indicator in the pH-sensing probe. Therefore, we have measured the intensities and wavelength shifts of the reflected lights, which change according to the color variations of indicators at different pH values, by using a spectrometer for spectral analysis. Also, the relationships between the pH values of liquid solutions and the optical properties of the modulated lights are obtained on the basis of the changes of the colors of indicators.

  11. Spectral characterization in deep UV of an improved imaging KDP acousto-optic tunable filter

    International Nuclear Information System (INIS)

    Gupta, Neelam; Voloshinov, Vitaly

    2014-01-01

    Recently, we developed a number of high quality noncollinear acousto-optic tunable filter (AOTF) cells in different birefringent materials with UV imaging capability. Cells based on a single crystal of KDP (potassium dihydrophosphate) had the best transmission efficiency and the optical throughput needed to acquire high quality spectral images at wavelengths above 220 nm. One of the main limitations of these imaging filters was their small angular aperture in air, limited to about 1.0°. In this paper, we describe an improved imaging KDP AOTF operating from the deep UV to the visible region of the spectrum. The linear and angular apertures of the new filter are 10 × 10 mm 2 and 1.8°, respectively. The spectral tuning range is 205–430 nm with a 60 cm −1 spectral resolution. We describe the filter and present experimental results on imaging using both a broadband source and a number of light emitting diodes (LEDs) in the UV, and include the measured spectra of these LEDs obtained with a collinear SiO 2 filter-based spectrometer operating above 255 nm. (paper)

  12. Scintillation index and performance analysis of wireless optical links over non-Kolmogorov weak turbulence based on generalized atmospheric spectral model.

    Science.gov (United States)

    Cang, Ji; Liu, Xu

    2011-09-26

    Based on the generalized spectral model for non-Kolmogorov atmospheric turbulence, analytic expressions of the scintillation index (SI) are derived for plane, spherical optical waves and a partially coherent Gaussian beam propagating through non-Kolmogorov turbulence horizontally in the weak fluctuation regime. The new expressions relate the SI to the finite turbulence inner and outer scales, spatial coherence of the source and spectral power-law and then used to analyze the effects of atmospheric condition and link length on the performance of wireless optical communication links. © 2011 Optical Society of America

  13. Removal of Optically Thick Clouds from Multi-Spectral Satellite Images Using Multi-Frequency SAR Data

    Directory of Open Access Journals (Sweden)

    Robert Eckardt

    2013-06-01

    Full Text Available This study presents a method for the reconstruction of pixels contaminated by optical thick clouds in multi-spectral Landsat images using multi-frequency SAR data. A number of reconstruction techniques have already been proposed in the scientific literature. However, all of the existing techniques have certain limitations. In order to overcome these limitations, we expose the Closest Spectral Fit (CSF method proposed by Meng et al. to a new, synergistic approach using optical and SAR data. Therefore, the term Closest Feature Vector (CFV is introduced. The technique facilitates an elegant way to avoid radiometric distortions in the course of image reconstruction. Furthermore the cloud cover removal is independent from underlying land cover types and assumptions on seasonality, etc. The methodology is applied to mono-temporal, multi-frequency SAR data from TerraSAR-X (X-Band, ERS (C-Band and ALOS Palsar (L-Band. This represents a way of thinking about Radar data not as foreign, but as additional data source in multi-spectral remote sensing. For the assessment of the image restoration performance, an experimental framework is established and a statistical evaluation protocol is designed. The results show the potential of a synergistic usage of multi-spectral and SAR data to overcome the loss of data due to cloud cover.

  14. Magneto-optical properties of InSb for terahertz applications

    Directory of Open Access Journals (Sweden)

    Jan Chochol

    2016-11-01

    Full Text Available Magneto-optical permittivity tensor spectra of undoped InSb, n-doped and p-doped InSb crystals were determined using the terahertz time-domain spectroscopy (THz-TDS and the Fourier transform far-infrared spectroscopy (far-FTIR. A Huge polar magneto-optical (MO Kerr-effect (up to 20 degrees in rotation and a simultaneous plasmonic behavior observed at low magnetic field (0.4 T and room temperature are promising for terahertz nonreciprocal applications. We demonstrate the possibility of adjusting the the spectral rage with huge MO by increase in n-doping of InSb. Spectral response is modeled using generalized magneto-optical Drude-Lorentz theory, giving us precise values of free carrier mobility, density and effective mass consistent with electric Hall effect measurement.

  15. Residual strain sensor using Al-packaged optical fiber and Brillouin optical correlation domain analysis.

    Science.gov (United States)

    Choi, Bo-Hun; Kwon, Il-Bum

    2015-03-09

    We propose a distributed residual strain sensor that uses an Al-packaged optical fiber for the first time. The residual strain which causes Brillouin frequency shifts in the optical fiber was measured using Brillouin optical correlation domain analysis with 2 cm spatial resolution. We quantified the Brillouin frequency shifts in the Al-packaged optical fiber by the tensile stress and compared them for a varying number of Al layers in the optical fiber. The Brillouin frequency shift of an optical fiber with one Al layer had a slope of 0.038 MHz/με with respect to tensile stress, which corresponds to 78% of that for an optical fiber without Al layers. After removal of the stress, 87% of the strain remained as residual strain. When different tensile stresses were randomly applied, the strain caused by the highest stress was the only one detected as residual strain. The residual strain was repeatedly measured for a time span of nine months for the purpose of reliability testing, and there was no change in the strain except for a 4% reduction, which is within the error tolerance of the experiment. A composite material plate equipped with our proposed Al-packaged optical fiber sensor was hammered for impact experiment and the residual strain in the plate was successfully detected. We suggest that the Al-packaged optical fiber can be adapted as a distributed strain sensor for smart structures, including aerospace structures.

  16. Spectral solar irradiance and some optical properties for various polluted atmospheres

    International Nuclear Information System (INIS)

    Jacovides, Constantinos P.; Asimakopoulos, Demosthenis N.; Steven, Michael D.

    2000-01-01

    Using ground-based spectroradiometric measurements taken over the Athens atmosphere during May 1995, the influence of gaseous pollutants and aerosol on the spectral radiant energy distribution was investigated. It was found that spectral measurements exhibited variations based on various polluted urban atmospheric conditions as determined via gaseous pollutants record analysis. The relative attenuations cause by gaseous pollutants and aerosol can exceed 27%, 17% and 16% in the global ultraviolet, visible and near-infrared portions of the solar spectrum respectively, as compared to 'background' values. In contrast, an enhancement of the near-infrared diffuse component by 66%, was observed, while in visible and ultraviolet bands the relative increases reached 54% and 21% respectively. Experimental total Rayleigh-corrected and spectral aerosol optical depths were retrieved, representing differences in polluted air over the Athens atmosphere. The diffuse component accounts for more than 80% of the total radiation field under high polluted atmosphere. The observed differences of solar radiation between the Athens center and at a nearby suburban site are a manifestation of contrasting air properties provided mainly by automotive traffic. (Author)

  17. DSP-enabled reconfigurable and transparent spectral converters for converging optical and mobile fronthaul/backhaul networks.

    Science.gov (United States)

    Mao, M Z; Giddings, R P; Cao, B Y; Xu, Y T; Wang, M; Tang, J M

    2017-06-12

    Dynamically reconfigurable and transparent signal spectral conversion is expected to play a vital role in seamlessly integrating traditional metropolitan optical networks and mobile fronthaul/backhaul networks. In this paper, a simple digital signal processing (DSP)-enabled spectral converter is proposed and extensively investigated, for the first time, which just utilizes a single standard dual-parallel Mach-Zehnder modulator (DP-MZM) driven by SDN-controllable RF signals and DC bias currents. As an important thrust of the paper, optimum operating conditions of the proposed converter are analytically identified, statistically examined and experimentally verified. Optimum operating condition-supported spectral converter performances in IMDD-based network nodes are explored both theoretically and experimentally in terms of frequency detuning range-dependent conversion efficiency, spectral conversion-induced OSNR/power penalty and transparency to input signal characteristics. The proposed spectral converter has unique advantages including low configuration complexity, strict transparency, SDN-controllable performance reconfigurability and flexibility, as well as negligible spectral conversion-induced latency.

  18. OPTICAL POLARIZATION AND SPECTRAL VARIABILITY IN THE M87 JET

    International Nuclear Information System (INIS)

    Perlman, Eric S.; Cara, Mihai; Bourque, Matthew; Simons, Raymond C.; Adams, Steven C.; Harris, D. E.; Madrid, Juan P.; Clausen-Brown, Eric; Cheung, C. C.; Stawarz, Lukasz; Georganopoulos, Markos; Sparks, William B.; Biretta, John A.

    2011-01-01

    During the last decade, M87's jet has been the site of an extraordinary variability event, with one knot (HST-1) increasing by over a factor 100 in brightness. Variability has also been seen on timescales of months in the nuclear flux. Here we discuss the optical-UV polarization and spectral variability of these components, which show vastly different behavior. HST-1 shows a highly significant correlation between flux and polarization, with P increasing from ∼20% at minimum to >40% at maximum, while the orientation of its electric vector stayed constant. HST-1's optical-UV spectrum is very hard (α UV-O ∼ 0.5, F ν ∝ν –α ), and displays 'hard lags' during epochs 2004.9-2005.5, including the peak of the flare, with soft lags at later epochs. We interpret the behavior of HST-1 as enhanced particle acceleration in a shock, with cooling from both particle aging and the relaxation of the compression. We set 2σ upper limits of 0.5δ pc and 1.02c on the size and advance speed of the flaring region. The slight deviation of the electric vector orientation from the jet position angle (P.A.) makes it likely that on smaller scales the flaring region has either a double or twisted structure. By contrast, the nucleus displays much more rapid variability, with a highly variable electric vector orientation and 'looping' in the (I, P) plane. The nucleus has a much steeper spectrum (α UV-O ∼ 1.5) but does not show UV-optical spectral variability. Its behavior can be interpreted as either a helical distortion to a steady jet or a shock propagating through a helical jet.

  19. OPTICAL POLARIZATION AND SPECTRAL VARIABILITY IN THE M87 JET

    Energy Technology Data Exchange (ETDEWEB)

    Perlman, Eric S.; Cara, Mihai; Bourque, Matthew; Simons, Raymond C. [Department of Physics and Space Sciences, 150 W. University Blvd., Florida Institute of Technology, Melbourne, FL 32901 (United States); Adams, Steven C. [Department of Physics and Astronomy, University of Georgia, Athens, GA 30605 (United States); Harris, D. E. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Madrid, Juan P. [Center for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, VIC 3122 (Australia); Clausen-Brown, Eric [Department of Physics, Purdue University, West Lafayette, IN 47907 (United States); Cheung, C. C. [National Academy of Sciences, Washington, DC 20001 (United States); Stawarz, Lukasz [Institute of Space and Astronautical Science, JAXA, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Georganopoulos, Markos [Department of Physics, University of Maryland-Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250 (United States); Sparks, William B.; Biretta, John A., E-mail: eperlman@fit.edu [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

    2011-12-20

    During the last decade, M87's jet has been the site of an extraordinary variability event, with one knot (HST-1) increasing by over a factor 100 in brightness. Variability has also been seen on timescales of months in the nuclear flux. Here we discuss the optical-UV polarization and spectral variability of these components, which show vastly different behavior. HST-1 shows a highly significant correlation between flux and polarization, with P increasing from {approx}20% at minimum to >40% at maximum, while the orientation of its electric vector stayed constant. HST-1's optical-UV spectrum is very hard ({alpha}{sub UV-O} {approx} 0.5, F{sub {nu}}{proportional_to}{nu}{sup -{alpha}}), and displays 'hard lags' during epochs 2004.9-2005.5, including the peak of the flare, with soft lags at later epochs. We interpret the behavior of HST-1 as enhanced particle acceleration in a shock, with cooling from both particle aging and the relaxation of the compression. We set 2{sigma} upper limits of 0.5{delta} pc and 1.02c on the size and advance speed of the flaring region. The slight deviation of the electric vector orientation from the jet position angle (P.A.) makes it likely that on smaller scales the flaring region has either a double or twisted structure. By contrast, the nucleus displays much more rapid variability, with a highly variable electric vector orientation and 'looping' in the (I, P) plane. The nucleus has a much steeper spectrum ({alpha}{sub UV-O} {approx} 1.5) but does not show UV-optical spectral variability. Its behavior can be interpreted as either a helical distortion to a steady jet or a shock propagating through a helical jet.

  20. Optical Sideband Generation: a Longitudinal Electron Beam Diagnostic Beyond the Laser Bandwidth Resolution Limit

    Energy Technology Data Exchange (ETDEWEB)

    Lawrence Berkeley National Laboratory; Tilborg, J. van; Matlis, N. H.; Plateau, G. R.; Leemans, W. P.

    2010-06-01

    Electro-optic sampling (EOS) is widely used as a technique to measure THz-domain electric field pulses such asthe self-fields of femtosecond electron beams. We present an EOS-based approach for single-shot spectral measurement that excels in simplicity (compatible with fiber integration) and bandwidth coverage (overcomes the laser bandwidth limitation), allowing few-fs electron beams or single-cycle THz pulses to be characterized with conventional picosecond probes. It is shown that the EOS-induced optical sidebands on the narrow-bandwidth optical probe are spectrally-shifted replicas of the THz pulse. An experimental demonstration on a 0-3 THz source is presented.

  1. Optical decoherence and persistent spectral hole burning in Tm{sup 3+}:LiNbO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Thiel, C.W., E-mail: thiel@physics.montana.ed [Department of Physics, Montana State University, EPS 264, Bozeman, MT 59717 (United States); Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States); Sun, Y. [Department of Physics, University of South Dakota, Vermillion, SD 57069 (United States); Boettger, T. [Department of Physics, University of San Francisco, San Francisco, CA 94117 (United States); Babbitt, W.R. [Department of Physics, Montana State University, EPS 264, Bozeman, MT 59717 (United States); Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States); Cone, R.L. [Department of Physics, Montana State University, EPS 264, Bozeman, MT 59717 (United States)

    2010-09-15

    We report studies of decoherence and spectral hole burning for the 794 nm optical transition of thulium-doped lithium niobate. In addition to transient spectral holes due to the {sup 3}H{sub 4} and {sup 3}F{sub 4} excited states of Tm{sup 3+}, persistent spectral holes with lifetimes of up to minutes were observed when a magnetic field of a few hundred Gauss was applied. The observed anti-hole structure identified the hole burning mechanism as population storage in the {sup 169}Tm nuclear hyperfine levels. In addition, the magnetic field was effective in suppressing spectral diffusion, increasing the phase memory lifetime from 11 {mu}s at zero field to 23 {mu}s in a field of 320 Gauss applied along the crystal's c-axis. Coupling between Tm{sup 3+} and the {sup 7}Li and {sup 93}Nb spins in the host lattice was also observed and a quadrupole shift of 22 kHz was measured for {sup 7}Li at 1.7 K. A Stark shift of 18 kHz cm/V was measured for the optical transition with the electric field applied parallel to the c-axis.

  2. Analysis of In-Situ Spectral Reflectance of Sago and Other Palms: Implications for Their Detection in Optical Satellite Images

    Science.gov (United States)

    Rendon Santillan, Jojene; Makinano-Santillan, Meriam

    2018-04-01

    We present a characterization, comparison and analysis of in-situ spectral reflectance of Sago and other palms (coconut, oil palm and nipa) to ascertain on which part of the electromagnetic spectrum these palms are distinguishable from each other. The analysis also aims to reveal information that will assist in selecting which band to use when mapping Sago palms using the images acquired by these sensors. The datasets used in the analysis consisted of averaged spectral reflectance curves of each palm species measured within the 345-1045 nm wavelength range using an Ocean Optics USB4000-VIS-NIR Miniature Fiber Optic Spectrometer. This in-situ reflectance data was also resampled to match the spectral response of the 4 bands of ALOS AVNIR-2, 3 bands of ASTER VNIR, 4 bands of Landsat 7 ETM+, 5 bands of Landsat 8, and 8 bands of Worldview-2 (WV2). Examination of the spectral reflectance curves showed that the near infra-red region, specifically at 770, 800 and 875 nm, provides the best wavelengths where Sago palms can be distinguished from other palms. The resampling of the in-situ reflectance spectra to match the spectral response of optical sensors made possible the analysis of the differences in reflectance values of Sago and other palms in different bands of the sensors. Overall, the knowledge learned from the analysis can be useful in the actual analysis of optical satellite images, specifically in determining which band to include or to exclude, or whether to use all bands of a sensor in discriminating and mapping Sago palms.

  3. Transfer standard for the spectral density of relative intensity noise of optical fiber sources near 1550 nm

    International Nuclear Information System (INIS)

    Obarski, Gregory E.; Splett, Jolene D.

    2001-01-01

    We have developed a transfer standard for the spectral density of relative intensity noise (RIN) of optical fiber sources near 1550 nm. Amplified spontaneous emission (ASE) from an erbium-doped fiber amplifier (EDFA), when it is optically filtered over a narrow band (<5 nm), yields a stable RIN spectrum that is practically constant to several tens of gigahertz. The RIN is calculated from the power spectral density as measured with a calibrated optical spectrum analyzer. For a typical device it is -110 dB/Hz, with uncertainty ≤0.12 dB/Hz. The invariance of the RIN under attenuation yields a considerable dynamic range with respect to rf noise levels. Results are compared with those from a second method that uses a distributed-feedback laser (DFB) that has a Poisson-limited RIN. Application of each method to the same RIN measurement system yields frequency-dependent calibration functions that, when they are averaged, differ by ≤0.2 dB. [copyright] 2001 Optical Society of America

  4. Phase-detected Brillouin optical correlation-domain reflectometry

    Science.gov (United States)

    Mizuno, Yosuke; Hayashi, Neisei; Fukuda, Hideyuki; Nakamura, Kentaro

    2018-05-01

    Optical fiber sensing techniques based on Brillouin scattering have been extensively studied for structural health monitoring owing to their capability of distributed strain and temperature measurement. Although a higher signal-to-noise ratio (leading to high spatial resolution and high-speed measurement) is generally obtained for two-end-access systems, they reduce the degree of freedom in embedding the sensors into structures, and render the measurement no longer feasible when extremely high loss or breakage occurs at a point of the sensing fiber. To overcome these drawbacks, a one-end-access sensing technique called Brillouin optical correlation-domain reflectometry (BOCDR) has been developed. BOCDR has a high spatial resolution and cost efficiency, but its conventional configuration suffered from relatively low-speed operation. In this paper, we review the recently developed high-speed configurations of BOCDR, including phase-detected BOCDR, with which we demonstrate real-time distributed measurement by tracking a propagating mechanical wave. We also demonstrate breakage detection with a wide strain dynamic range.

  5. Analytical investigation of a novel interrogation approach of fiber Bragg grating sensors using Optical Frequency Domain Reflectometry

    Science.gov (United States)

    Yüksel, Kivilcim; Pala, Deniz

    2016-06-01

    This work presents a novel approach in interrogating Polarization Dependent Loss (PDL) of cascaded identical FBGs using Optical Frequency Domain Reflectometer (OFDR). The fundamentals of both polarisation properties of uniform FBGs and polarisation-sensitive OFDR are explained and the benefits of this novel approach in measuring transversal load are discussed. The numerical programs computing the spectral evolution of PDL of the FBGs in the array as a function of grating parameters (grating length and birefringence) are presented. Our simulation results show an excellent agreement with the previously reported simulation (and experimental) results in the literature obtained on a single FBG by using classical state-of-the-art measurement techniques. As an envisaged application, the proposed system shows the feasibility of measuring the residual stresses during manufacturing process of composite materials which is not straightforward by amplitude spectrum measurements and/or considering only the axial strains.

  6. Understanding Soliton Spectral Tunneling as a Spectral Coupling Effect

    DEFF Research Database (Denmark)

    Guo, Hairun; Wang, Shaofei; Zeng, Xianglong

    2013-01-01

    Soliton eigenstate is found corresponding to a dispersive phase profile under which the soliton phase changes induced by the dispersion and nonlinearity are instantaneously counterbalanced. Much like a waveguide coupler relying on a spatial refractive index profile that supports mode coupling...... between channels, here we suggest that the soliton spectral tunneling effect can be understood supported by a spectral phase coupler. The dispersive wave number in the spectral domain must have a coupler-like symmetric profile for soliton spectral tunneling to occur. We show that such a spectral coupler...

  7. Real-time processing for full-range Fourier-domain optical-coherence tomography with zero-filling interpolation using multiple graphic processing units.

    Science.gov (United States)

    Watanabe, Yuuki; Maeno, Seiya; Aoshima, Kenji; Hasegawa, Haruyuki; Koseki, Hitoshi

    2010-09-01

    The real-time display of full-range, 2048?axial pixelx1024?lateral pixel, Fourier-domain optical-coherence tomography (FD-OCT) images is demonstrated. The required speed was achieved by using dual graphic processing units (GPUs) with many stream processors to realize highly parallel processing. We used a zero-filling technique, including a forward Fourier transform, a zero padding to increase the axial data-array size to 8192, an inverse-Fourier transform back to the spectral domain, a linear interpolation from wavelength to wavenumber, a lateral Hilbert transform to obtain the complex spectrum, a Fourier transform to obtain the axial profiles, and a log scaling. The data-transfer time of the frame grabber was 15.73?ms, and the processing time, which includes the data transfer between the GPU memory and the host computer, was 14.75?ms, for a total time shorter than the 36.70?ms frame-interval time using a line-scan CCD camera operated at 27.9?kHz. That is, our OCT system achieved a processed-image display rate of 27.23 frames/s.

  8. Spectral tunneling of lattice nonlocal solitons

    International Nuclear Information System (INIS)

    Kartashov, Yaroslav V.; Torner, Lluis; Vysloukh, Victor A.

    2010-01-01

    We address spectral tunneling of walking spatial solitons in photorefractive media with nonlocal diffusion component of the nonlinear response and an imprinted shallow optical lattice. In contrast to materials with local nonlinearities, where solitons traveling across the lattice close to the Bragg angle suffer large radiative losses, in photorefractive media with diffusion nonlinearity resulting in self-bending, solitons survive when their propagation angle approaches and even exceeds the Bragg angle. In the spatial frequency domain this effect can be considered as tunneling through the band of spatial frequencies centered around the Bragg frequency where the spatial group velocity dispersion is positive.

  9. Enhancement of nonlinear optical response of weakly confined excitons in GaAs thin films by spectrally rectangle-shape-pulse-excitation

    International Nuclear Information System (INIS)

    Kojima, O; Isu, T; Ishi-Hayase, J; Sasaki, M; Tsuchiya, M

    2007-01-01

    We report the enhancement of the nonlinear optical response of the weakly confined excitons with use of spectrally rectangular pulse. The nonlinear optical response was investigated as a function of excitation energy by a degenerate four-wave-mixing (DFWM) technique. In the case that the laser pulse with the controlled spectral shape excites the plural exciton states simultaneously, the DFWM signal intensity is enhanced by a factor of two in comparison with the intensity under the excitation of a single exciton state. This enhancement is caused by the superposition of the nonlinear optical responses from the plural exciton states

  10. InP monolithically integrated label swapper device for spectral amplitude coded optical packet networks

    NARCIS (Netherlands)

    Muñoz, P.; García-Olcina, R.; Doménech, J.D.; Rius, M.; Sancho, J.C.; Capmany, J.; Chen, L.R.; Habib, C.; Leijtens, X.J.M.; Vries, de T.; Heck, M.J.R.; Augustin, L.M.; Nötzel, R.; Robbins, D.J.

    2010-01-01

    In this paper a label swapping device, for spectral amplitude coded optical packet networks, fully integrated using InP technology is presented. Compared to previous demonstrations using discrete component assembly, the device footprint is reduced by a factor of 105 and the operation speed is

  11. Acute Solar Retinopathy Imaged With Adaptive Optics, Optical Coherence Tomography Angiography, and En Face Optical Coherence Tomography.

    Science.gov (United States)

    Wu, Chris Y; Jansen, Michael E; Andrade, Jorge; Chui, Toco Y P; Do, Anna T; Rosen, Richard B; Deobhakta, Avnish

    2018-01-01

    Solar retinopathy is a rare form of retinal injury that occurs after direct sungazing. To enhance understanding of the structural changes that occur in solar retinopathy by obtaining high-resolution in vivo en face images. Case report of a young adult woman who presented to the New York Eye and Ear Infirmary with symptoms of acute solar retinopathy after viewing the solar eclipse on August 21, 2017. Results of comprehensive ophthalmic examination and images obtained by fundus photography, microperimetry, spectral-domain optical coherence tomography (OCT), adaptive optics scanning light ophthalmoscopy, OCT angiography, and en face OCT. The patient was examined after viewing the solar eclipse. Visual acuity was 20/20 OD and 20/25 OS. The patient was left-eye dominant. Spectral-domain OCT images were consistent with mild and severe acute solar retinopathy in the right and left eye, respectively. Microperimetry was normal in the right eye but showed paracentral decreased retinal sensitivity in the left eye with a central absolute scotoma. Adaptive optics images of the right eye showed a small region of nonwaveguiding photoreceptors, while images of the left eye showed a large area of abnormal and nonwaveguiding photoreceptors. Optical coherence tomography angiography images were normal in both eyes. En face OCT images of the right eye showed a small circular hyperreflective area, with central hyporeflectivity in the outer retina of the right eye. The left eye showed a hyperreflective lesion that intensified in area from inner to middle retina and became mostly hyporeflective in the outer retina. The shape of the lesion on adaptive optics and en face OCT images of the left eye corresponded to the shape of the scotoma drawn by the patient on Amsler grid. Acute solar retinopathy can present with foveal cone photoreceptor mosaic disturbances on adaptive optics scanning light ophthalmoscopy imaging. Corresponding reflectivity changes can be seen on en face OCT, especially

  12. Approaches to contactless optical thermometer in the NIR spectral range based on Nd{sup 3+} doped crystalline nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Kaldvee, K.; Nefedova, A.V. [Institute of Physics, University of Tartu, W. Ostwaldi st. 1, Tartu 50411 (Estonia); Fedorenko, S.G. [Voevodsky Institute of Chemical Kinetics and Combustion SB RAS, Novosibirsk 630090 (Russian Federation); Vanetsev, A.S. [Institute of Physics, University of Tartu, W. Ostwaldi st. 1, Tartu 50411 (Estonia); Prokhorov General Physics Institute RAS, Vavilov st. 38, Moscow 119991 (Russian Federation); Orlovskaya, E.O. [Prokhorov General Physics Institute RAS, Vavilov st. 38, Moscow 119991 (Russian Federation); Puust, L.; Pärs, M.; Sildos, I. [Institute of Physics, University of Tartu, W. Ostwaldi st. 1, Tartu 50411 (Estonia); Ryabova, A.V. [Prokhorov General Physics Institute RAS, Vavilov st. 38, Moscow 119991 (Russian Federation); National Research Nuclear University Moscow Engineering Physics Institute, Kashirskoe Highway, 31, Moscow 115409 (Russian Federation); Orlovskii, Yu.V., E-mail: orlovski@Lst.gpi.ru [Institute of Physics, University of Tartu, W. Ostwaldi st. 1, Tartu 50411 (Estonia); Prokhorov General Physics Institute RAS, Vavilov st. 38, Moscow 119991 (Russian Federation)

    2017-03-15

    The fluorescence kinetics and spectral intensity ratio (FIR) methods for contactless optical temperature measurement in the NIR spectral range with Nd{sup 3+} doped YAG micro- and YPO{sub 4} nanocrystals are considered and the problems are revealed. The requirements for good temperature RE doped crystalline nanoparticles sensor are formulated.

  13. ANALYSIS OF IN-SITU SPECTRAL REFLECTANCE OF SAGO AND OTHER PALMS: IMPLICATIONS FOR THEIR DETECTION IN OPTICAL SATELLITE IMAGES

    Directory of Open Access Journals (Sweden)

    J. R. Santillan

    2018-04-01

    Full Text Available We present a characterization, comparison and analysis of in-situ spectral reflectance of Sago and other palms (coconut, oil palm and nipa to ascertain on which part of the electromagnetic spectrum these palms are distinguishable from each other. The analysis also aims to reveal information that will assist in selecting which band to use when mapping Sago palms using the images acquired by these sensors. The datasets used in the analysis consisted of averaged spectral reflectance curves of each palm species measured within the 345–1045 nm wavelength range using an Ocean Optics USB4000-VIS-NIR Miniature Fiber Optic Spectrometer. This in-situ reflectance data was also resampled to match the spectral response of the 4 bands of ALOS AVNIR-2, 3 bands of ASTER VNIR, 4 bands of Landsat 7 ETM+, 5 bands of Landsat 8, and 8 bands of Worldview-2 (WV2. Examination of the spectral reflectance curves showed that the near infra-red region, specifically at 770, 800 and 875 nm, provides the best wavelengths where Sago palms can be distinguished from other palms. The resampling of the in-situ reflectance spectra to match the spectral response of optical sensors made possible the analysis of the differences in reflectance values of Sago and other palms in different bands of the sensors. Overall, the knowledge learned from the analysis can be useful in the actual analysis of optical satellite images, specifically in determining which band to include or to exclude, or whether to use all bands of a sensor in discriminating and mapping Sago palms.

  14. The optical constants and spectral specular reflectivity of highly oriented pyrolytic graphite (HOPG)

    International Nuclear Information System (INIS)

    Havstad, M.A.; Schildbach, M.A.; McLean, W. II.

    1993-08-01

    Measurements of the specular reflectivity and the optical constants of highly ordered pyrolytic graphite (HOPG) have been made using two independent optical systems. The first measures reflectance (at 1.06 μm and 293 K) by comparing the intensity of a laser beam before and after reflecting off the sample. The second determines the complex index of raft-action (from 0.55 to 8.45 μm, with sample temperatures of 293, 480, 900 and 1300 K) by ellipsometry. Agreement between the two methods is good. Moderate reflectivities are observed over the full spectral range of measurement: the spectral directional-hemispherical reflectivity at normal incidence varies from 0.41 at 0.55 μm to 0.74 at 8.45 μm. The components of the complex index of refraction increase smoothly with wavelength. The index of refraction increases from 3.10 at 0.55 μm to 7.84 at 8.45 μm. The extinction coefficient varies from 2.01 to 6.66 over the same range

  15. Autofluorescence Imaging and Spectral-Domain Optical Coherence Tomography in Incomplete Congenital Stationary Night Blindness and Comparison with Retinitis Pigmentosa

    Science.gov (United States)

    CHEN, ROYCE W. S.; GREENBERG, JONATHAN P.; LAZOW, MARGOT A.; RAMACHANDRAN, RITHU; LIMA, LUIZ H.; HWANG, JOHN C.; SCHUBERT, CARL; BRAUNSTEIN, ALEXANDRA; ALLIKMETS, RANDO; TSANG, STEPHEN H.

    2015-01-01

    PURPOSE To test the hypothesis that the evaluation of retinal structure can have diagnostic value in differentiating between incomplete congenital stationary night blindness (CSNB2) and retinitis pigmentosa (RP). To compare retinal thickness differences between patients with CSNB2 and myopic controls. DESIGN Prospective cross-sectional study. METHODS Ten eyes of 5 patients diagnosed with CSNB2 (4 X-linked recessive, 1 autosomal recessive) and 6 eyes of 3 patients with RP (2 autosomal dominant, 1 autosomal recessive) were evaluated with spectral-domain optical coherence tomography (SD OCT) and fundus autofluorescence (FAF). Diagnoses of CSNB2 and RP were confirmed by full-field electroretinography (ERG). Manual segmentation of retinal layers, aided by a computer program, was performed by 2 professional segmenters on SD OCT images of all CSNB2 patients and 4 age-similar, normal myopic controls. Seven patients were screened for mutations with congenital stationary night blindness and RP genotyping arrays. RESULTS Patients with CSNB2 had specific findings on SD OCT and FAF that were distinct from those found in RP. CSNB2 patients showed qualitatively normal SD OCT results with preserved photoreceptor inner segment/outer segment junction, whereas this junction was lost in RP patients. In addition, CSNB2 patients had normal FAF images, whereas patients with RP demonstrated a ring of increased autofluorescence around the macula. On SD OCT segmentation, the inner and outer retinal layers of both X-linked recessive and autosomal recessive CSNB2 patients were thinner compared with those of normal myopic controls, with means generally outside of normal 95% confidence intervals. The only layers that demonstrated similar thickness between CSNB2 patients and the controls were the retinal nerve fiber layer and, temporal to the fovea, the combined outer segment layer and retinal pigment epithelium. A proband and his 2 affected brothers from a family segregating X-linked recessive

  16. Compressive sensing in a photonic link with optical integration

    DEFF Research Database (Denmark)

    Chen, Ying; Yu, Xianbin; Chi, Hao

    2014-01-01

    In this Letter, we present a novel structure to realize photonics-assisted compressive sensing (CS) with optical integration. In the system, a spectrally sparse signal modulates a multiwavelength continuous-wave light and then is mixed with a random sequence in optical domain. The optical signal......, which is equivalent to the function of integration required in CS. A proof-of-concept experiment with four wavelengths, corresponding to a compression factor of 4, is demonstrated. More simulation results are also given to show the potential of the technique....

  17. EXCESS OPTICAL ENHANCEMENT OBSERVED WITH ARCONS FOR EARLY CRAB GIANT PULSES

    Energy Technology Data Exchange (ETDEWEB)

    Strader, M. J.; Mazin, B. A.; Spiro Jaeger, G. V.; Gwinn, C. R.; Meeker, S. R.; Szypryt, P.; Van Eyken, J. C.; Marsden, D.; Walter, A. B.; Ulbricht, G. [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Johnson, M. D. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); O' Brien, K. [Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Stoughton, C. [Fermilab Center for Particle Astrophysics, Batavia, IL 60510 (United States); Bumble, B. [NASA Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91125 (United States)

    2013-12-10

    We observe an extraordinary link in the Crab pulsar between the enhancement of an optical pulse and the timing of the corresponding giant radio pulse. At optical through infrared wavelengths, our observations use the high time resolution of ARray Camera for Optical to Near-IR Spectrophotometry, a unique superconducting energy-resolving photon-counting array at the Palomar 200 inch telescope. At radio wavelengths, we observe with the Robert C. Byrd Green Bank Telescope and the Green Bank Ultimate Pulsar Processing Instrument backend. We see an 11.3% ± 2.5% increase in peak optical flux for pulses that have an accompanying giant radio pulse arriving near the peak of the optical main pulse, in contrast to a 3.2% ± 0.5% increase when an accompanying giant radio pulse arrives soon after the optical peak. We also observe that the peak of the optical main pulse is 2.8% ± 0.8% enhanced when there is a giant radio pulse accompanying the optical interpulse. We observe no statistically significant spectral differences between optical pulses accompanied by and not accompanied by giant radio pulses. Our results extend previous observations of optical-radio correlation to the time and spectral domains. Our refined temporal correlation suggests that optical and radio emission are indeed causally linked, and the lack of spectral differences suggests that the same mechanism is responsible for all optical emission.

  18. EXCESS OPTICAL ENHANCEMENT OBSERVED WITH ARCONS FOR EARLY CRAB GIANT PULSES

    International Nuclear Information System (INIS)

    Strader, M. J.; Mazin, B. A.; Spiro Jaeger, G. V.; Gwinn, C. R.; Meeker, S. R.; Szypryt, P.; Van Eyken, J. C.; Marsden, D.; Walter, A. B.; Ulbricht, G.; Johnson, M. D.; O'Brien, K.; Stoughton, C.; Bumble, B.

    2013-01-01

    We observe an extraordinary link in the Crab pulsar between the enhancement of an optical pulse and the timing of the corresponding giant radio pulse. At optical through infrared wavelengths, our observations use the high time resolution of ARray Camera for Optical to Near-IR Spectrophotometry, a unique superconducting energy-resolving photon-counting array at the Palomar 200 inch telescope. At radio wavelengths, we observe with the Robert C. Byrd Green Bank Telescope and the Green Bank Ultimate Pulsar Processing Instrument backend. We see an 11.3% ± 2.5% increase in peak optical flux for pulses that have an accompanying giant radio pulse arriving near the peak of the optical main pulse, in contrast to a 3.2% ± 0.5% increase when an accompanying giant radio pulse arrives soon after the optical peak. We also observe that the peak of the optical main pulse is 2.8% ± 0.8% enhanced when there is a giant radio pulse accompanying the optical interpulse. We observe no statistically significant spectral differences between optical pulses accompanied by and not accompanied by giant radio pulses. Our results extend previous observations of optical-radio correlation to the time and spectral domains. Our refined temporal correlation suggests that optical and radio emission are indeed causally linked, and the lack of spectral differences suggests that the same mechanism is responsible for all optical emission

  19. Reliability and reproducibility of spectral and time domain optical coherence tomography images before and after correction for patients with age-related macular degeneration [v2; ref status: indexed, http://f1000r.es/50m

    Directory of Open Access Journals (Sweden)

    Mohammad A. Sadiq

    2015-03-01

    Full Text Available Purpose: To evaluate the reproducibility and reliability of optical coherence tomography scans obtained using the time domain (TD-OCT StratusTM OCT, and the Spectral Domain (SD-OCT SpectralisTM and CirrusTM OCT devices before and after manual correction in eyes with either Neovascular (NV-AMD or Non-Neovascular (NNV-AMD age-related macular degeneration. Design: Prospective observational study. Methods: Setting: University-based retina practice. Patients: Thirty-six patients (50 eyes with NV-AMD or NNV-AMD. Procedure: OCT scans were taken simultaneously using one TD-OCT and two SD-OCT devices. Main Outcome Measures: Macular thickness measurements were assessed before and after correction of the algorithm by constructing Bland-Altman plots for agreement and calculating intraclass correlation coefficients (ICCs and coefficients of repeatability (COR to evaluate intraclass repeatability. Results: Spectralis had the highest number of images needing manual correction.  All machines had high ICCs, with Spectralis having the highest.  Also, Bland-Altman plots indicated that there was low agreement between Cirrus™ and Stratus™, Spectralis™ and Stratus™, while there was good agreement between the Cirrus™ and Spectralis™.  The CORs were lowest for SpectralisTM and similar and higher for CirrusTM and StratusTM.  Agreement, CORs, and ICCs generally improved after manual correction, but only minimally.  Conclusion: Agreement is low between devices, except between both SD-OCT machines.  Manual correction tends to improve results.

  20. Spectral evolution of soft x-ray emission from optically thin, high electron temperature platinum plasmas

    Directory of Open Access Journals (Sweden)

    Hiroyuki Hara

    2017-08-01

    Full Text Available The soft x-ray spectra of heavy element plasmas are frequently dominated by unresolved transition array (UTA emission. We describe the spectral evolution of an intense UTA under optically thin conditions in platinum plasmas. The UTA was observed to have a peak wavelength around 4.6 nm at line-of-sight averaged electron temperatures less than 1.4 keV at electron densities of (2.5–7.5 × 1013 cm−3. The UTA spectral structure was due to emission from 4d–4f transitions in highly charged ions with average charge states of q = 20–40. A numerical simulation successfully reproduced the observed spectral behavior.

  1. Transfer standard for the spectral density of relative intensity noise of optical fiber sources near 1550 nm

    Energy Technology Data Exchange (ETDEWEB)

    Obarski, Gregory E.; Splett, Jolene D.

    2001-06-01

    We have developed a transfer standard for the spectral density of relative intensity noise (RIN) of optical fiber sources near 1550 nm. Amplified spontaneous emission (ASE) from an erbium-doped fiber amplifier (EDFA), when it is optically filtered over a narrow band ({lt}5 nm), yields a stable RIN spectrum that is practically constant to several tens of gigahertz. The RIN is calculated from the power spectral density as measured with a calibrated optical spectrum analyzer. For a typical device it is {minus}110 dB/Hz, with uncertainty {le}0.12 dB/Hz. The invariance of the RIN under attenuation yields a considerable dynamic range with respect to rf noise levels. Results are compared with those from a second method that uses a distributed-feedback laser (DFB) that has a Poisson-limited RIN. Application of each method to the same RIN measurement system yields frequency-dependent calibration functions that, when they are averaged, differ by {le}0.2 dB. {copyright} 2001 Optical Society of America

  2. Frequency domain finite-element and spectral-element acoustic wave modeling using absorbing boundaries and perfectly matched layer

    Science.gov (United States)

    Rahimi Dalkhani, Amin; Javaherian, Abdolrahim; Mahdavi Basir, Hadi

    2018-04-01

    Wave propagation modeling as a vital tool in seismology can be done via several different numerical methods among them are finite-difference, finite-element, and spectral-element methods (FDM, FEM and SEM). Some advanced applications in seismic exploration benefit the frequency domain modeling. Regarding flexibility in complex geological models and dealing with the free surface boundary condition, we studied the frequency domain acoustic wave equation using FEM and SEM. The results demonstrated that the frequency domain FEM and SEM have a good accuracy and numerical efficiency with the second order interpolation polynomials. Furthermore, we developed the second order Clayton and Engquist absorbing boundary condition (CE-ABC2) and compared it with the perfectly matched layer (PML) for the frequency domain FEM and SEM. In spite of PML method, CE-ABC2 does not add any additional computational cost to the modeling except assembling boundary matrices. As a result, considering CE-ABC2 is more efficient than PML for the frequency domain acoustic wave propagation modeling especially when computational cost is high and high-level absorbing performance is unnecessary.

  3. Normative spectral domain optical coherence tomography data on macular and retinal nerve fiber layer thickness in Indians

    Directory of Open Access Journals (Sweden)

    Bindu Appukuttan

    2014-01-01

    Full Text Available Aim: To provide the normative data of macular and retinal nerve fiber layer (RNFL thickness in Indians using spectral domain OCT (Spectralis OCT, Heidelberg Engineering, Germany and to evaluate the effects of age, gender, and refraction on these parameters. Design: Observational, cross-sectional study. Materials and Methods: The eyes of 105 healthy patients aged between 20-75 years, with no ocular disease and best corrected visual acuity of 20/20, were scanned using standard scanning protocols by a single examiner. Exclusion criteria included glaucoma, retinal diseases, diabetes, history of prior intraocular surgery or laser treatment. The mean macular and RNFL thickness were recorded, and the effects of age, gender, and refraction on these parameters were evaluated. This data was compared with published literature on Caucasians to assess the ethnic variations of these parameters. Results: The normal central foveal thickness in healthy Indian eyes measured using Spectralis OCT was 260.1 ± 18.19 ΅m. The nasal inner quadrant showed maximum retinal thickness (338.88 ± 18.17 ΅m.The mean RNFL thickness was 101.43 ± 8.63 ΅m with maximum thickness in the inferior quadrant. The central foveal thickness showed a gender-based difference (P = 0.005 but did not correlate significantly with age (P = 0.134, whereas the parafoveal, perifoveal thickness, macular volume, and RNFL thickness showed significant negative correlation with age. Conclusions: Our study provides the normative database for Indians on Spectralis OCT. It also suggests that age should be considered while interpreting the macular thickness and RNFL, whereas gender should also be given consideration in central foveal thickness.

  4. Fourier domain optical coherence tomography achieves full range complex imaging in vivo by introducing a carrier frequency during scanning

    International Nuclear Information System (INIS)

    Wang, Ruikang K

    2007-01-01

    The author describes a Fourier domain optical coherence tomography (FDOCT) system that is capable of full range complex imaging in vivo. This is achieved by introducing a constant carrier frequency into the OCT spectral interferograms at the time when imaging is performed. The complex functions of the spatial interferograms formed by each single wavelength are constructed before performing the Fourier transformation to localize the scatters within a sample. Two algorithms, based on Fourier filtering and Hilbert transformation, respectively, are described to achieve the full range complex FDOCT imaging. It is shown that the Hilbert transformation approach delivers better performance than the Fourier filtering method does in terms of tolerating the sample movement in vivo. The author finally demonstrates experimentally the system and algorithms for true in vivo imaging at a rate of 20 000 axial scans per second

  5. Estimation of Soil Moisture Content from the Spectral Reflectance of Bare Soils in the 0.4–2.5 µm Domain

    Directory of Open Access Journals (Sweden)

    Sophie Fabre

    2015-02-01

    Full Text Available This work aims to compare the performance of new methods to estimate the Soil Moisture Content (SMC of bare soils from their spectral signatures in the reflective domain (0.4–2.5 µm in comparison with widely used spectral indices like Normalized Soil Moisture Index (NSMI and Water Index SOIL (WISOIL. Indeed, these reference spectral indices use wavelengths located in the water vapour absorption bands and their performance are thus very sensitive to the quality of the atmospheric compensation. To reduce these limitations, two new spectral indices are proposed which wavelengths are defined using the determination matrix tool by taking into account the atmospheric transmission: Normalized Index of Nswir domain for Smc estimatiOn from Linear correlation (NINSOL and Normalized Index of Nswir domain for Smc estimatiOn from Non linear correlation (NINSON. These spectral indices are completed by two new methods based on the global shape of the soil spectral signatures. These methods are the Inverse Soil semi-Empirical Reflectance model (ISER, using the inversion of an existing empirical soil model simulating the soil spectral reflectance according to soil moisture content for a given soil class, and the convex envelope model, linking the area between the envelope and the spectral signature to the SMC. All these methods are compared using a reference database built with 32 soil samples and composed of 190 spectral signatures with five or six soil moisture contents. Half of the database is used for the calibration stage and the remaining to evaluate the performance of the SMC estimation methods. The results show that the four new methods lead to similar or better performance than the one obtained by the reference indices. The RMSE is ranging from 3.8% to 6.2% and the coefficient of determination R2 varies between 0.74 and 0.91 with the best performance obtained with the ISER model. In a second step, simulated spectral radiances at the sensor level are

  6. Power spectral density of velocity fluctuations estimated from phase Doppler data

    OpenAIRE

    Jicha Miroslav; Lizal Frantisek; Jedelsky Jan

    2012-01-01

    Laser Doppler Anemometry (LDA) and its modifications such as PhaseDoppler Particle Anemometry (P/DPA) is point-wise method for optical nonintrusive measurement of particle velocity with high data rate. Conversion of the LDA velocity data from temporal to frequency domain – calculation of power spectral density (PSD) of velocity fluctuations, is a non trivial task due to nonequidistant data sampling in time. We briefly discuss possibilities for the PSD estimation and specify limitations caused...

  7. Quasi-optical analysis of a far-infrared spatio-spectral space interferometer concept

    Science.gov (United States)

    Bracken, C.; O'Sullivan, C.; Murphy, J. A.; Donohoe, A.; Savini, G.; Lightfoot, J.; Juanola-Parramon, R.; Fisica Consortium

    2016-07-01

    FISICA (Far-Infrared Space Interferometer Critical Assessment) was a three year study of a far-infrared spatio-spectral double-Fourier interferometer concept. One of the aims of the FISICA study was to set-out a baseline optical design for such a system, and to use a model of the system to simulate realistic telescope beams for use with an end-to-end instrument simulator. This paper describes a two-telescope (and hub) baseline optical design that fulfils the requirements of the FISICA science case, while minimising the optical mass of the system. A number of different modelling techniques were required for the analysis: fast approximate simulation tools such as ray tracing and Gaussian beam methods were employed for initial analysis, with GRASP physical optics used for higher accuracy in the final analysis. Results are shown for the predicted far-field patterns of the telescope primary mirrors under illumination by smooth walled rectangular feed horns. Far-field patterns for both on-axis and off-axis detectors are presented and discussed.

  8. Spectral optical properties of selected photosynthetic microalgae producing biofuels

    International Nuclear Information System (INIS)

    Lee, Euntaek; Heng, Ri-Liang; Pilon, Laurent

    2013-01-01

    This paper presents the spectral complex index of refraction of biofuel producing photosynthetic microalgae between 400 and 750 nm. They were retrieved from their experimentally measured average absorption and scattering cross-sections. The microalgae were treated as homogeneous polydisperse spheres with equivalent diameter such that their surface area was identical to that of their actual spheroidal shape. An inverse method was developed combining Lorentz–Mie theory as the forward method and genetic algorithm. The unicellular green algae Chlamydomonas reinhardtii strain CC125 and its truncated chlorophyll antenna transformants tla1, tlaX, and tla1-CW + as well as Botryococcus braunii, Chlorella sp., and Chlorococcum littorale were investigated. These species were selected for their ability to produce either hydrogen gas or lipids for liquid fuel production. Their retrieved real and imaginary parts of the complex index of refraction were continuous functions of wavelength with absorption peaks corresponding to those of in vivo Chlorophylls a and b. The T-matrix method was also found to accurately predict the experimental measurements by treating the microalgae as axisymmetric spheroids with the experimentally measured major and minor diameter distributions and the retrieved spectral complex index of refraction. Finally, pigment mass fractions were also estimated from the retrieved absorption index. The method and/or the reported optical properties can be used in various applications from ocean remote sensing, carbon cycle study, as well as photobiological carbon dioxide mitigation and biofuel production. -- Highlights: ► Retrieval of optical properties from average absorption and scattering cross-sections. ► Inverse method based on Lorentz–Mie theory and genetic algorithm. ► Refraction and absorption indices of selected microalgae between 400 and 750 nm. ► Determination of pigment concentrations from absorption index. ► Good agreement between T

  9. Spectral optical properties of long-range transport Asian dust and pollution aerosols over Northeast Asia in 2007 and 2008

    Directory of Open Access Journals (Sweden)

    J. Jung

    2010-06-01

    Full Text Available As a part of the IGAC (International Global Atmospheric Chemistry Mega-cities program, aerosol physical and optical properties were continuously measured from March 2007 to March 2008 at an urban site (37.57° N, 126.94° E in Seoul, Korea. Spectral optical properties of long-range transported Asian dust and pollution aerosols have been investigated based on the year long measurement data. Optically measured black carbon/thermally measured elemental carbon (BC/EC ratio showed clear monthly variation with high values in summer and low values in winter mainly due to the enhancement of light attenuation by the internal mixing of EC. Novel approach has been suggested to retrieve the spectral light absorption coefficient (babs from Aethalometer raw data by using BC/EC ratio. Mass absorption efficiency, σabs (=babs/EC at 550 nm was determined to be 9.0±1.3, 8.9±1.5, 9.5±2.0, and 10.3±1.7 m2 g−1 in spring, summer, fall, and winter, respectively with an annual mean of 9.4±1.8 m2 g−1. Threshold values to classify severe haze events were suggested in this study. Increasing trend of aerosol single scattering albedo (SSA with wavelength was observed during Asian dust events while little spectral dependence of SSA was observed during long-range transport pollution (LTP events. Satellite aerosol optical thickness (AOT and Hysplit air mass backward trajectory analyses as well as chemical analysis were performed to characterize the dependence of spectral optical properties on aerosol type. Results from this study can provide useful information for studies on regional air quality and aerosol's effects on climate change.

  10. Optimization of a Michelson interferometer with a rotating retroreflector in opitcal design, spectral resolution, and optical throughput

    International Nuclear Information System (INIS)

    Haschberger, P.; Tank, V.

    1993-01-01

    A newly designed Michelson interferometer for Fourier spectroscopy utilizes a nutating retroreflector (cube corner mirror) to generate alterations in geometrical and optical paths. The practical optomechanical design of a Fourier-transform spectrometer incorporating a rotating retroreflector for path-length alteration is considered. (The instrument has been given the name MIROR, for Michelson Interferometer with a Rotating Retroreflector.) Two parameters of the instrument are essential: the maximum optical path difference, which yields the spectral resolution of the instrument, and the diameter of the transmitted beam, which determines the throughput and hence the achievable signal-to-noise ratio. The maximum allowable beam diameter is calculated as a function of the geometry and the orientation of the rotating retroreflector and the other optical components. The geometrical configuration and the orientation of all the optical components with respect to one another are also optimized for the maximum transmitted beam diameter when the required path difference is given. A principal investigation of different possible configurations of the optical components is presented. Then a quantitative optimization for an interferometer employing a retroreflector having a 5-in. (12.7-cm) aperture diameter requiring an optical path difference of more than 10 cm (spectral resolution better than 0.1 cm -1 ) is performed. Finally a simplified but enhanced design is described. 10 refs., 15 figs

  11. Microscope Integrated Intraoperative Spectral Domain Optical Coherence Tomography for Cataract Surgery: Uses and Applications.

    Science.gov (United States)

    Das, Sudeep; Kummelil, Mathew Kurian; Kharbanda, Varun; Arora, Vishal; Nagappa, Somshekar; Shetty, Rohit; Shetty, Bhujang K

    2016-05-01

    To demonstrate the uses and applications of a microscope integrated intraoperative Optical Coherence Tomography in Micro Incision Cataract Surgery (MICS) and Femtosecond Laser Assisted Cataract Surgery (FLACS). Intraoperative real time imaging using the RESCAN™ 700 (Carl Zeiss Meditec, Oberkochen, Germany) was done for patients undergoing MICS as well as FLACS. The OCT videos were reviewed at each step of the procedure and the findings were noted and analyzed. Microscope Integrated Intraoperative Optical Coherence Tomography was found to be beneficial during all the critical steps of cataract surgery. We were able to qualitatively assess wound morphology in clear corneal incisions, in terms of subclinical Descemet's detachments, tears in the inner or outer wound lips, wound gaping at the end of surgery and in identifying the adequacy of stromal hydration, for both FLACS as well as MICS. It also enabled us to segregate true posterior polar cataracts from suspected cases intraoperatively. Deciding the adequate depth of trenching was made simpler with direct visualization. The final position of the intraocular lens in the capsular bag and the lack of bioadhesivity of hydrophobic acrylic lenses were also observed. Even though Microscope Integrated Intraoperative Optical Coherence Tomography is in its early stages for its application in cataract surgery, this initial assessment does show a very promising role for this technology in the future for cataract surgery both in intraoperative decision making as well as for training purposes.

  12. Ultrafast spectral dynamics of dual-color-soliton intracavity collision in a mode-locked fiber laser

    Science.gov (United States)

    Wei, Yuan; Li, Bowen; Wei, Xiaoming; Yu, Ying; Wong, Kenneth K. Y.

    2018-02-01

    The single-shot spectral dynamics of dual-color-soliton collisions inside a mode-locked laser is experimentally and numerically investigated. By using the all-optically dispersive Fourier transform, we spectrally unveil the collision-induced soliton self-reshaping process, which features dynamic spectral fringes over the soliton main lobe, and the rebuilding of Kelly sidebands with wavelength drifting. Meanwhile, the numerical simulations validate the experimental observation and provide additional insights into the physical mechanism of the collision-induced spectral dynamics from the temporal domain perspective. It is verified that the dynamic interference between the soliton and the dispersive waves is responsible for the observed collision-induced spectral evolution. These dynamic phenomena not only demonstrate the role of dispersive waves in the sophisticated soliton interaction inside the laser cavity, but also facilitate a deeper understanding of the soliton's inherent stability.

  13. Fast Industrial Inspection of Optical Thin Film Using Optical Coherence Tomography

    Directory of Open Access Journals (Sweden)

    Muhammad Faizan Shirazi

    2016-09-01

    Full Text Available An application of spectral domain optical coherence tomography (SD-OCT was demonstrated for a fast industrial inspection of an optical thin film panel. An optical thin film sample similar to a liquid crystal display (LCD panel was examined. Two identical SD-OCT systems were utilized for parallel scanning of a complete sample in half time. Dual OCT inspection heads were utilized for transverse (fast scanning, while a stable linear motorized translational stage was used for lateral (slow scanning. The cross-sectional and volumetric images of an optical thin film sample were acquired to detect the defects in glass and other layers that are difficult to observe using visual inspection methods. The rapid inspection enabled by this setup led to the early detection of product defects on the manufacturing line, resulting in a significant improvement in the quality assurance of industrial products.

  14. Bandwidth scalable, coherent transmitter based on the parallel synthesis of multiple spectral slices using optical arbitrary waveform generation.

    Science.gov (United States)

    Geisler, David J; Fontaine, Nicolas K; Scott, Ryan P; He, Tingting; Paraschis, Loukas; Gerstel, Ori; Heritage, Jonathan P; Yoo, S J B

    2011-04-25

    We demonstrate an optical transmitter based on dynamic optical arbitrary waveform generation (OAWG) which is capable of creating high-bandwidth (THz) data waveforms in any modulation format using the parallel synthesis of multiple coherent spectral slices. As an initial demonstration, the transmitter uses only 5.5 GHz of electrical bandwidth and two 10-GHz-wide spectral slices to create 100-ns duration, 20-GHz optical waveforms in various modulation formats including differential phase-shift keying (DPSK), quaternary phase-shift keying (QPSK), and eight phase-shift keying (8PSK) with only changes in software. The experimentally generated waveforms showed clear eye openings and separated constellation points when measured using a real-time digital coherent receiver. Bit-error-rate (BER) performance analysis resulted in a BER < 9.8 × 10(-6) for DPSK and QPSK waveforms. Additionally, we experimentally demonstrate three-slice, 4-ns long waveforms that highlight the bandwidth scalable nature of the optical transmitter. The various generated waveforms show that the key transmitter properties (i.e., packet length, modulation format, data rate, and modulation filter shape) are software definable, and that the optical transmitter is capable of acting as a flexible bandwidth transmitter.

  15. Growth, spectral and optical characterization of a novel nonlinear optical organic material: D-Alanine DL-Mandelic acid single crystal

    Science.gov (United States)

    Jayaprakash, P.; Mohamed, M. Peer; Caroline, M. Lydia

    2017-04-01

    An organic nonlinear optical single crystal, D-alanine DL-mandelic acid was synthesized and successfully grown by slow evaporation solution growth technique at ambient temperature using solvent of aqueous solution. The unit cell parameters were assessed from single crystal X-ray diffraction analysis. The presence of diverse functional groups and vibrational modes were identified using Fourier Transform Infra Red and Fourier Transform Raman spectral analyses. The chemical structure of grown crystal has been identified by Nuclear Magnetic Resonance spectroscopic study. Ultraviolet-visible spectral analysis reveal that the crystal has lower cut-off wavelength down to 259 nm, is a key factor to exhibit second harmonic generation signal. The electronic optical band gap and Urbach energy is calculated as 5.31 eV and 0.2425 eV respectively from the UV absorption profile. The diverse optical properties such as, extinction coefficient, reflectance, linear refractive index, optical conductivity was calculated using UV-visible data. The relative second harmonic efficiency of the compound is found to be 0.81 times greater than that of KH2PO4 (KDP). The thermal stability of the grown crystal was studied by thermogravimetric analysis and differential thermal analysis techniques. The luminescence spectrum exhibited two peaks (520 nm, 564 nm) due to the donation of protons from carboxylic acid to amino group. The Vickers microhardness test was carried out employing one of the as-grown hard crystal and there by hardness number (Hv), Meyer's index (n), yield strength (σy), elastic stiffness constant (C11) and Knoop hardness number (HK) were assessed. The dielectric behaviour of the as-grown crystal was analyzed for different temperatures (313 K, 333 K, 353 K, and 373 K) at different frequencies.

  16. Two-tint pump-probe measurements using a femtosecond laser oscillator and sharp-edged optical filters.

    Science.gov (United States)

    Kang, Kwangu; Koh, Yee Kan; Chiritescu, Catalin; Zheng, Xuan; Cahill, David G

    2008-11-01

    We describe a simple approach for rejecting unwanted scattered light in two types of time-resolved pump-probe measurements, time-domain thermoreflectance (TDTR) and time-resolved incoherent anti-Stokes Raman scattering (TRIARS). Sharp edged optical filters are used to create spectrally distinct pump and probe beams from the broad spectral output of a femtosecond Ti:sapphire laser oscillator. For TDTR, the diffusely scattered pump light is then blocked by a third optical filter. For TRIARS, depolarized scattering created by the pump is shifted in frequency by approximately 250 cm(-1) relative to the polarized scattering created by the probe; therefore, spectral features created by the pump and probe scattering can be easily distinguished.

  17. Crystal growth, structural, spectral, thermal, dielectric, linear and nonlinear optical characteristics of a new organic acentric material: L-Methionine-Succinic acid (2/1)

    Science.gov (United States)

    Nageshwari, M.; Kumari, C. Rathika Thaya; Vinitha, G.; Mohamed, M. Peer; Sudha, S.; Caroline, M. Lydia

    2018-03-01

    L-Methionine-Succinic acid (2/1) (LMSA), 2C5H11NO2S·C4H6O4, a novel nonlinear optical material which belongs to the class of organic category was grown-up for the first time by the technique of slow evaporation. Purity of LMSA was improved using repetitive recrystallization. LMSA was analyzed by single crystal and powder X-ray diffraction investigation to affirm the crystal structure and crystalline character. The single crystal XRD revealed that LMSA corresponds to the crystal system of triclinic with P1 as space group showing the asymmetric unit consists of a neutral succinic acid molecule and two methionine residues which are crystallographically independent existing in zwitterionic form. The functional groups existing in LMSA was accomplished using Fourier transform infrared spectroscopy. The optical transparency and the band gap energy were identified utilizing UV-Visible spectrum. The optical constants specifically reflectance and extinction coefficient clearly indicate the elevated transparency of LMSA. The thermal analyses affirmed its thermal stability. The luminescence behavior of LMSA has been analyzed by Photoluminescence (PL) spectral study. The mechanical, laser damage threshold and dielectric investigation of LMSA was done to suggest the material for practical applications. The second and third harmonic generation efficacy was confirmed by means of Kurtz-Perry and Z-scan procedure which attest its potentiality in the domain of nonlinear optics.

  18. In-plane optical spectral weight redistribution in the optimally doped Ba0.6 K0.4Fe2As2 superconductor

    International Nuclear Information System (INIS)

    Xu Bing; Dai Yao-Min; Xiao Hong; Qiu Xiang-Gang; Lobo, R. P. S. M.

    2014-01-01

    We performed detailed temperature-dependent optical measurements on optimally doped Ba 0.6 K 0.4 Fe 2 As 2 single crystal. We examine the changes of the in-plane optical conductivity spectral weight in the normal state and the evolution of the superconducting condensate in the superconducting state. In the normal state, the low-frequency spectral weight shows a metallic response with an arctan (T) dependence, indicating a T-linear scattering rate behavior for the carriers. A high energy spectral weight transfer associated with the Hund's coupling occurs from the low frequencies below 4000 cm −1 ∼ 5000 cm −1 to higher frequencies up to at least 10 cm −1 . Its temperature dependence analysis suggests that the Hund's coupling strength is continuously enhanced as the temperature is reduced. In the superconducting state, the FGT sum rule is conserved according to the spectral weight estimation within the conduction bands, only about 40% of the conduction bands participates in the superconducting condensate indicating that Ba 0.6 K 0.4 Fe 2 As 2 is in dirty limit. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  19. Theoretical study of optical properties of anti phase domains in GaP

    Energy Technology Data Exchange (ETDEWEB)

    Tea, E., E-mail: etea.contact@gmail.com [Institute of R and D on Photovoltaic Energy (IRDEP) (UMR 7174, EDF-CNRS-ENSCP), 6 Quai Watier BP 49, 78401 Chatou cedex (France); FOTON INSA-Rennes (UMR 6082 CNRS), Université Européenne de Bretagne, 20 Avenue des Buttes de Coësmes, 35708 Rennes (France); Vidal, J.; Laribi, S.; Guillemoles, J.-F. [Institute of R and D on Photovoltaic Energy (IRDEP) (UMR 7174, EDF-CNRS-ENSCP), 6 Quai Watier BP 49, 78401 Chatou cedex (France); Pedesseau, L.; Cornet, C.; Jancu, J.-M.; Even, J.; Durand, O. [FOTON INSA-Rennes (UMR 6082 CNRS), Université Européenne de Bretagne, 20 Avenue des Buttes de Coësmes, 35708 Rennes (France)

    2014-02-14

    III-V/Si heterostructures are currently investigated for silicon photonics and solar energy conversion. In particular, dilute nitride alloy GaAsPN grown on a GaP/Si platform exhibits lattice match with Si and an optimal band gap configuration for tandem solar cell devices. However, monolithic “coherent” growth of the GaP thin layer on Si suffers from the nucleation of extended structural defects, which can hamper device operation as well as the GaP/Si interface level and through their propagation inside the overall heterostructure. However, the effect of such structural defects on optical and transport properties is actually not well understood in details. In this letter, we investigate the anti phase domains defect (also called inversion domains) by means of ab initio calculations giving insights into the alteration of optical and transport properties of GaP due to the defective GaP/Si interface.

  20. INFORMATIVITY OF SPECTRAL OPTICAL COHERENT TOMOGRAPHY IN AGGRESSIVE POSTERIOR RETINOPATHY OF PREMATURITY

    Directory of Open Access Journals (Sweden)

    A. V. Tereshchenko

    2017-01-01

    Full Text Available The purpose: to evaluate the informativity of optical coherence tomography in patients with aggressive posterior retinopathy of prematurity. Patients and methods. spectral optical coherence tomography using portable device iVue-100 with a removable camera (Optovue, USA was held in 32 children (64 eyes with aggressive posterior retinopathy of prematurity with a gestational period 26–31 week. Results. Children with aggressive posterior retinopathy of prematurity at the stage of early clinical manifestations, in addition to the indication that the immaturity of the retina, according to the spectral optical coherence tomography revealed only a few areas of epiretinal proliferation, which are not visualized with a digital retinoscopy and binocular indirect ophthalmoscopy. When the process is more pronounced in children with retinopathy of prematurity aggressive rear stage manifestation already determined multiple zones epiretinal proliferation as a "mushroom" and "flake" conglomerates with rear zone hyaloid membrane had an uneven seal. Coarser structural disorders of the retina and the vitreoretinal interface have been identified in patients with advancedstage aggressive posterior retinopathy of prematurity. We determined the shaft extraretinal proliferation as a "comb", as well as portions of epiretinal proliferation on the border of vascularized and avascular retina, which tended to merge, and the formation of massive hyperreflection complexes, lifted back hyaloid membrane, which was not only uneven sealed, but in some places is stratified. Conclusion. Despite the complexity of the procedure and the complexity of its implementation, the data obtained are particularly valuable and informative because they allow to complement the clinical picture and objectify it. It helps to choose the optimal tactics and improvement of a differentiated approach to the treatment of aggressive posterior retinopathy of prematurity.

  1. Broadband superluminescent diodes and semiconductor optical amplifiers for the spectral range 750 - 800 nm

    International Nuclear Information System (INIS)

    Il'chenko, S N; Kostin, Yu O; Kukushkin, I A; Ladugin, M A; Lapin, P I; Lobintsov, A A; Marmalyuk, Aleksandr A; Yakubovich, S D

    2011-01-01

    We have studied superluminescent diodes (SLDs) and semiconductor optical amplifiers (SOAs) based on an (Al x Ga 1-x )As/GaAs single quantum well structure with an Al content x ∼ 0.1 in a 10-nm-thick active layer. Depending on the length of the active channel, the single-mode fibre coupled cw output power of the SLDs is 1 to 30 mW at a spectral width of about 50 nm. The width of the optical gain band in the active channel exceeds 40 nm. Preliminary operating life tests have demonstrated that the devices are sufficiently reliable. (lasers)

  2. High symmetry versus optical isotropy of a negative-index metamaterial

    DEFF Research Database (Denmark)

    Menzel, Christoph; Rockstuhl, Carsten; Lliew, Rumen

    2010-01-01

    condition since it is usually assumed that light does not resolve the spatial details of MM but experiences the properties of an effective medium, which is then optically isotropic. In this work we challenge this assumption by analyzing the isofrequency surfaces of the dispersion relation of the split cube...... in carcass negative index MM. We show that this MM is basically optically isotropic but not in the spectral domain where it exhibits negative refraction. The primary goal of this contribution is to introduce a tool that allows to probe a MM against optical isotropy....

  3. Fundus auto fluorescence and spectral domain ocular coherence tomography in the early detection of chloroquine retinopathy

    OpenAIRE

    Megan B. Goodman; Ari Ziskind

    2015-01-01

    Purpose: To determine the sensitivity of spectral domain ocular coherence tomography (SD-OCT) and fundus auto fluorescence (FAF) images as a screening test to detect early changes in the retina prior to the onset of chloroquine retinopathy. Method: The study was conducted using patients taking chloroquine (CQ), referred by the Rheumatology Department to the Ophthalmology Department at Tygerberg Academic Hospital. Group A consisted of 59 patients on CQ for less than 5 years, and Group B co...

  4. RADIANCE AND PHOTON NOISE: Imaging in geometrical optics, physical optics, quantum optics and radiology.

    Science.gov (United States)

    Barrett, Harrison H; Myers, Kyle J; Caucci, Luca

    2014-08-17

    A fundamental way of describing a photon-limited imaging system is in terms of a Poisson random process in spatial, angular and wavelength variables. The mean of this random process is the spectral radiance. The principle of conservation of radiance then allows a full characterization of the noise in the image (conditional on viewing a specified object). To elucidate these connections, we first review the definitions and basic properties of radiance as defined in terms of geometrical optics, radiology, physical optics and quantum optics. The propagation and conservation laws for radiance in each of these domains are reviewed. Then we distinguish four categories of imaging detectors that all respond in some way to the incident radiance, including the new category of photon-processing detectors. The relation between the radiance and the statistical properties of the detector output is discussed and related to task-based measures of image quality and the information content of a single detected photon.

  5. Unified Multi-Layer among Software Defined Multi-Domain Optical Networks (Invited

    Directory of Open Access Journals (Sweden)

    Hui Yang

    2015-06-01

    Full Text Available The software defined networking (SDN enabled by OpenFlow protocol has gained popularity which can enable the network to be programmable and accommodate both fixed and flexible bandwidth services. In this paper, we present a unified multi-layer (UML architecture with multiple controllers and a dynamic orchestra plane (DOP for software defined multi-domain optical networks. The proposed architecture can shield the differences among various optical devices from multi-vendors and the details of connecting heterogeneous networks. The cross-domain services with on-demand bandwidth can be deployed via unified interfaces provided by the dynamic orchestra plane. Additionally, the globalization strategy and practical capture of signal processing are presented based on the architecture. The overall feasibility and efficiency of the proposed architecture is experimentally verified on the control plane of our OpenFlow-based testbed. The performance of globalization strategy under heavy traffic load scenario is also quantitatively evaluated based on UML architecture compared with other strategies in terms of blocking probability, average hops, and average resource consumption.

  6. Linear and Nonlinear Impairment Compensation in Coherent Optical Transmission with Digital Signal Processing

    DEFF Research Database (Denmark)

    Porto da Silva, Edson

    Digital signal processing (DSP) has become one of the main enabling technologies for the physical layer of coherent optical communication networks. The DSP subsystems are used to implement several functionalities in the digital domain, from synchronization to channel equalization. Flexibility...... nonlinearity compensation, (II) spectral shaping, and (III) adaptive equalization. For (I), original contributions are presented to the study of the nonlinearity compensation (NLC) with digital backpropagation (DBP). Numerical and experimental performance investigations are shown for different application...... scenarios. Concerning (II), it is demonstrated how optical and electrical (digital) pulse shaping can be allied to improve the spectral confinement of a particular class of optical time-division multiplexing (OTDM) signals that can be used as a building block for fast signaling single-carrier transceivers...

  7. Brillouin optical correlation domain analysis in composite material beams

    DEFF Research Database (Denmark)

    Stern, Yonatan; London, Yosef; Preter, Eyal

    2017-01-01

    Structural health monitoring is a critical requirement in many composites. Numerous monitoring strategies rely on measurements of temperature or strain (or both), however these are often restricted to point-sensing or to the coverage of small areas. Spatially-continuous data can be obtained...... with optical fiber sensors. In this work, we report high-resolution distributed Brillouin sensing over standard fibers that are embedded in composite structures. A phase-coded, Brillouin optical correlation domain analysis (B-OCDA) protocol was employed, with spatial resolution of 2 cm and sensitivity of 1 °K...... or 20 micro-strain. A portable measurement setup was designed and assembled on the premises of a composite structures manufacturer. The setup was successfully utilized in several structural health monitoring scenarios: (a) monitoring the production and curing of a composite beam over 60 h; (b...

  8. Practical implementation of spectral-intensity dispersion-canceled optical coherence tomography with artifact suppression

    Science.gov (United States)

    Shirai, Tomohiro; Friberg, Ari T.

    2018-04-01

    Dispersion-canceled optical coherence tomography (OCT) based on spectral intensity interferometry was devised as a classical counterpart of quantum OCT to enhance the basic performance of conventional OCT. In this paper, we demonstrate experimentally that an alternative method of realizing this kind of OCT by means of two optical fiber couplers and a single spectrometer is a more practical and reliable option than the existing methods proposed previously. Furthermore, we develop a recipe for reducing multiple artifacts simultaneously on the basis of simple averaging and verify experimentally that it works successfully in the sense that all the artifacts are mitigated effectively and only the true signals carrying structural information about the sample survive.

  9. System and method that suppresses intensity fluctuations for free space high-speed optical communication

    Science.gov (United States)

    Berman, Gennady P [Los Alamos, NM; Bishop, Alan R [Los Alamos, NM; Nguyen, Dinh C [Los Alamos, NM; Chernobrod, Boris M [Santa Fe, NM; Gorshkov, Vacheslav N [Kiev, UA

    2009-10-13

    A high-speed (Gbps), free space optical communication system is based on spectral encoding of radiation from a wide band light source, such as a laser. By using partially coherent laser beams in combination with a relatively slow photosensor, scintillations can be suppressed by orders of magnitude for distances of more than 10 km. To suppress the intensity fluctuations due to atmospheric turbulence, a source with partial transverse coherence in combination with slow response time photodetector is used. Information is encoded in the spectral domain of a wideband optical source by modulation of spectral amplitudes. A non-coherent light source with wide spectrum (an LED, for example) may be used for high-speed communication over short (less than about a mile) distances.

  10. Label swapper device for spectral amplitude coded optical packet networks monolithically integrated on InP

    NARCIS (Netherlands)

    Muñoz, P.; García-Olcina, R.; Habib, C.; Chen, L.R.; Leijtens, X.J.M.; Vries, de T.; Robbins, D.J.; Capmany, J.

    2011-01-01

    In this paper the design, fabrication and experimental characterization of an spectral amplitude coded (SAC) optical label swapper monolithically integrated on Indium Phosphide (InP) is presented. The device has a footprint of 4.8x1.5 mm2 and is able to perform label swapping operations required in

  11. Optical spectral reshaping for directly modulated 4-pulse amplitude modulation signals

    DEFF Research Database (Denmark)

    Ozolins, Oskars; Da Ros, Francesco; Cristofori, Valentina

    2017-01-01

    The tremendous traffic growth in intra/inter-datacenters requires low-cost high-speed integrated solutions [1]. To enable a significantly reduced footprint directly modulated lasers (DMLs) have been proposed instead of large external modulators. However, it is challenging to use DMLs due to their......The tremendous traffic growth in intra/inter-datacenters requires low-cost high-speed integrated solutions [1]. To enable a significantly reduced footprint directly modulated lasers (DMLs) have been proposed instead of large external modulators. However, it is challenging to use DMLs due...... (PAM) [3] signals. However, moving to 4-PAM,many of the impressive demonstrations reported so far rely heavily on off-line digital signal processing (DSP), which increases latency, power consumption and cost. In this talk, we report on (i) a detailed numerical analysis on the complex transfer function...... of the optical filter for optical spectral reshaping in case of pulse amplitude modulation and(ii) an experimental demonstration of real-time dispersion-uncompensated transmission of 10-GBd and 14-GBd 4-PAM signals up to 10- and 26-km SSMF. This is achieved by combining a commercial 10-Gb/s DML with optical...

  12. Optical spin-transfer-torque-driven domain-wall motion in a ferromagnetic semiconductor

    Czech Academy of Sciences Publication Activity Database

    Ramsay, A.J.; Roy, P.E.; Haigh, J.A.; Otxoa, R.M.; Irvine, A.C.; Janda, T.; Campion, R. P.; Gallagher, B. L.; Wunderlich, Joerg

    2015-01-01

    Roč. 114, č. 6 (2015), "067202-1"-"067202-5" ISSN 0031-9007 R&D Projects: GA ČR GB14-37427G Institutional support: RVO:68378271 Keywords : magnetic domain walls * magneto-optics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 7.645, year: 2015

  13. Spectral studies of ocean water with space-borne sensor SCIAMACHY using Differential Optical Absorption Spectroscopy (DOAS

    Directory of Open Access Journals (Sweden)

    M. Vountas

    2007-09-01

    Full Text Available Methods enabling the retrieval of oceanic parameter from the space borne instrumentation Scanning Imaging Absorption Spectrometer for Atmospheric ChartographY (SCIAMACHY using Differential Optical Absorption Spectroscopy (DOAS are presented. SCIAMACHY onboard ENVISAT measures back scattered solar radiation at a spectral resolution (0.2 to 1.5 nm. The DOAS method was used for the first time to fit modelled Vibrational Raman Scattering (VRS in liquid water and in situ measured phytoplankton absorption reference spectra to optical depths measured by SCIAMACHY. Spectral structures of VRS and phytoplankton absorption were clearly found in these optical depths. Both fitting approaches lead to consistent results. DOAS fits correlate with estimates of chlorophyll concentrations: low fit factors for VRS retrievals correspond to large chlorophyll concentrations and vice versa; large fit factors for phytoplankton absorption correspond with high chlorophyll concentrations and vice versa. From these results a simple retrieval technique taking advantage of both measurements is shown. First maps of global chlorophyll concentrations were compared to the corresponding MODIS measurements with very promising results. In addition, results from this study will be used to improve atmospheric trace gas DOAS-retrievals from visible wavelengths by including these oceanographic signatures.

  14. Teleophthalmology with optical coherence tomography imaging in community optometry. Evaluation of a quality improvement for macular patients

    Directory of Open Access Journals (Sweden)

    Kelly SP

    2011-12-01

    Full Text Available Simon P Kelly1, Ian Wallwork2, David Haider1, Kashif Qureshi11Ophthalmology Department, Royal Bolton Hospital National Health Service Foundation Trust, Bolton, 2Wallwork Opticians, Salford, UKPurpose: To describe a quality improvement for referral of National Health Service patients with macular disorders from a community optometry setting in an urban area.Methods: Service evaluation of teleophthalmology consultation based on spectral domain optical coherence tomography images acquired by the community optometrist and transmitted to hospital eye services.Results: Fifty patients with suspected macular conditions were managed via telemedicine consultation over 1 year. Responses were provided by hospital eye service-based ophthalmologists to the community optometrist or patient within the next day in 48 cases (96% and in 34 (68% patients on the same day. In the consensus opinion of the optometrist and ophthalmologist, 33 (66% patients required further “face-to-face” medical examination and were triaged on clinical urgency. Seventeen cases (34% were managed in the community and are a potential cost improvement. Specialty trainees were supervised in telemedicine consultations.Conclusion: Innovation and quality improvement were demonstrated in both optometry to ophthalmology referrals and in primary optometric care by use of telemedicine with spectral domain optical coherence tomography images. E-referral of spectral domain optical coherence tomography images assists triage of macular patients and swifter care of urgent cases. Teleophthalmology is also, in the authors’ opinion, a tool to improve interdisciplinary professional working with community optometrists. Implications for progress are discussed.Keywords: telemedicine, teleophthalmology, innovation, community referral, optical coherence tomography, service evaluation

  15. Magnetic field effects on spectrally resolved lifetime of on-line oxygen monitoring using magneto-optic probes

    Science.gov (United States)

    Mermut, O.; Gallant, P.; Le Bouch, N.; Leclair, S.; Noiseux, I.; Vernon, M.; Morin, J.-F.; Diamond, K.; Patterson, M. S.; Samkoe, K.; Pogue, B.

    2009-02-01

    Multimodal agents that serve as both probes for contrast and light-activated effectors of cellular processes in diseased tissue were developed. These agents were introduced into multicellular tumor spheroids (3D tissue models) and in the chorioallantoic membrane (CAM) of a chicken embryo. The luminescence decay was examined using a novel technique involving a spectrally-resolved fluorescence lifetime apparatus integrated with a weak electromagnet. A spectrallyresolved lifetime setup was used to identify magneto-optic species sensitive to magnetic field effects and distinguish from background emissions. We demonstrate that the applied magnetic fields can alter reaction rates and product distribution of some dyes detected by time- and spectrally-resolved luminescence changes. We will discuss the use of exogenous magneto-optical probes taken up in tumors to both induce phototoxicity, a process that is governed by complex and dynamically evolving mechanisms involving reactive oxygen species, and monitor treatment progress. The magnetic field enhancement, measured over a range of weak fields (0-300 mT) is correlated to oxygenation and may be used to monitor dynamic changes occurring due to oxygen consumption over the course of photodynamic therapy. Such online measurements provide the possibility to derive real-time information about response to treatment via monitoring magnetic field enhancement/suppression of the time-resolved, spectrally-resolved luminescence of the probe at the site of the treatment directly. Magnetic perturbation of lifetime can serve as a status reporter, providing optical feedback of oxygen-mediated treatments in situ and allowing for real-time adjustment of a phototherapy treatment plan.

  16. Characterization of Abnormal Optic Nerve Head Morphology in Albinism Using Optical Coherence Tomography.

    Science.gov (United States)

    Mohammad, Sarim; Gottlob, Irene; Sheth, Viral; Pilat, Anastasia; Lee, Helena; Pollheimer, Ellen; Proudlock, Frank Anthony

    2015-07-01

    To characterize abnormalities in three-dimensional optic nerve head (ONH) morphology in people with albinism (PWA) using spectral-domain optical coherence tomography (SD-OCT) and to determine whether ONH abnormalities relate to other retinal and clinical abnormalities. Spectral-domain OCT was used to obtain three-dimensional images from 56 PWA and 60 age- and sex-matched control subjects. B-scans were corrected for nystagmus-associated motion artefacts. Disc, cup, and rim ONH dimensions and peripapillary retinal nerve fiber layer (ppRNFL) thickness were calculated using Copernicus and ImageJ software. Median disc areas were similar in PWA (median = 1.65 mm2) and controls (1.71 mm2, P = 0.128), although discs were significantly elongated horizontally in PWA (P < 0.001). In contrast, median optic cup area in PWA (0.088 mm2) was 23.7% of that in controls (0.373 mm2, P < 0.001), with 39.4% of eyes in PWA not demonstrating a measurable optic cup. This led to significantly smaller cup to disc ratios in PWA (P < 0.001). Median rim volume in PWA (0.273 mm3) was 136.6% of that in controls (0.200 mm3). The ppRNFL was significantly thinner in PWA compared with controls (P < 0.001), especially in the temporal quadrant. In PWA, ppRNFL thickness was correlated to ganglion cell thickness at the central fovea (P = 0.007). Several ONH abnormalities, such as cup to disc ratio, were related to higher refractive errors in PWA. In PWA, ocular maldevelopment is not just limited to the retina but also involves the ONH. Reduced ppRNFL thickness is consistent with previous reports of reduced ganglion cell numbers in PWA. The thicker rim volumes may be a result of incomplete maturation of the ONH.

  17. Spacetime Discontinuous Galerkin FEM: Spectral Response

    International Nuclear Information System (INIS)

    Abedi, R; Omidi, O; Clarke, P L

    2014-01-01

    Materials in nature demonstrate certain spectral shapes in terms of their material properties. Since successful experimental demonstrations in 2000, metamaterials have provided a means to engineer materials with desired spectral shapes for their material properties. Computational tools are employed in two different aspects for metamaterial modeling: 1. Mircoscale unit cell analysis to derive and possibly optimize material's spectral response; 2. macroscale to analyze their interaction with conventional material. We compare two different approaches of Time-Domain (TD) and Frequency Domain (FD) methods for metamaterial applications. Finally, we discuss advantages of the TD method of Spacetime Discontinuous Galerkin finite element method (FEM) for spectral analysis of metamaterials

  18. A prospective, comparative, observational study on optical coherence tomography of the anterior eye segment

    NARCIS (Netherlands)

    Theelen, T.; Hoyng, C.B.

    2013-01-01

    BACKGROUND: We compared two commercially available spectral-domain optical coherence tomography (OCT) devices according to their capacity of imaging the anterior segment of the eye with the same detail and quality. METHODS: A prospective, observational, single-visit study with individuals aged 18

  19. 2D Spatial Frequency Considerations in Comparing 1D Power Spectral Density Measurements

    International Nuclear Information System (INIS)

    Takacs, P.Z.; Barber, S.; Church, E.L.; Kaznatcheev, K.; McKinney, W.R.; Yashchuk, V.Y.

    2010-01-01

    The frequency footprint of ID and 2D profiling instruments needs to be carefully considered in comparing ID surface roughness spectrum measurements made by different instruments. Contributions from orthogonal direction frequency components can not be neglected. The use of optical profiling instruments is ubiquitous in the measurement of the roughness of optical surfaces. Their ease-of-use and non-contact measurement method found widespread use in the optics industry for measuring the quality of delicate optical surfaces. Computerized digital data acquisition with these instruments allowed for quick and easy calculation of surface roughness statistics, such as root-mean-square (RMS) roughness. The computing power of the desktop computer allowed for the rapid conversion of spatial domain data into the frequency domain, enabling the application of sophisticated signal processing techniques to be applied to the analysis of surface roughness, the most powerful of which is the power spectral density (PSP) function. Application of the PSD function to surface statistics introduced the concept of 'bandwidth-limited' roughness, where the value of the RMS roughness depends critically upon the spatial frequency response of the instrument. Different instruments with different spatial frequency response characteristics give different answers when measuring the same surface.

  20. Compact optical processor for Hough and frequency domain features

    Science.gov (United States)

    Ott, Peter

    1996-11-01

    Shape recognition is necessary in a broad band of applications such as traffic sign or work piece recognition. It requires not only neighborhood processing of the input image pixels but global interconnection of them. The Hough transform (HT) performs such a global operation and it is well suited in the preprocessing stage of a shape recognition system. Translation invariant features can be easily calculated form the Hough domain. We have implemented on the computer a neural network shape recognition system which contains a HT, a feature extraction, and a classification layer. The advantage of this approach is that the total system can be optimized with well-known learning techniques and that it can explore the parallelism of the algorithms. However, the HT is a time consuming operation. Parallel, optical processing is therefore advantageous. Several systems have been proposed, based on space multiplexing with arrays of holograms and CGH's or time multiplexing with acousto-optic processors or by image rotation with incoherent and coherent astigmatic optical processors. We took up the last mentioned approach because 2D array detectors are read out line by line, so a 2D detector can achieve the same speed and is easier to implement. Coherent processing can allow the implementation of tilers in the frequency domain. Features based on wedge/ring, Gabor, or wavelet filters have been proven to show good discrimination capabilities for texture and shape recognition. The astigmatic lens system which is derived form the mathematical formulation of the HT is long and contains a non-standard, astigmatic element. By methods of lens transformation s for coherent applications we map the original design to a shorter lens with a smaller number of well separated standard elements and with the same coherent system response. The final lens design still contains the frequency plane for filtering and ray-tracing shows diffraction limited performance. Image rotation can be done

  1. Constellation Shaping for Fiber-optic Channels with QAM and High Spectral Efficiency

    DEFF Research Database (Denmark)

    Yankov, Metodi Plamenov; Zibar, Darko; Larsen, Knud J.

    2014-01-01

    In this letter the fiber-optic communication channel with Quadrature Amplitude Modulation (QAM) input constella- tion is treated. Using probabilistic shaping, we show that high order QAM constellations can achieve and slightly exceed the lower bound on the channel capacity, set by ring constellat......In this letter the fiber-optic communication channel with Quadrature Amplitude Modulation (QAM) input constella- tion is treated. Using probabilistic shaping, we show that high order QAM constellations can achieve and slightly exceed the lower bound on the channel capacity, set by ring...... constellations in [1]. We then propose a mapping function for turbo coded bit interleaved coded modulation based on optimization of the mu- tual information between the channel input and output. Using this mapping, spectral efficiency as high as 6.5 bits/s/Hz/polarization is achieved on a simulated single...... channel long-haul fiber-optical link excluding the pilot overhead, used for synchronization, and taking into account frequency and phase mismatch impairments, as well as laser phase noise and analog-to-digital conversion quantization impairments. The simulations suggest that major improvements can...

  2. Theory and optical design of x-ray echo spectrometers

    Science.gov (United States)

    Shvyd'ko, Yuri

    2017-08-01

    X-ray echo spectroscopy, a space-domain counterpart of neutron spin echo, is a recently proposed inelastic x-ray scattering (IXS) technique. X-ray echo spectroscopy relies on imaging IXS spectra and does not require x-ray monochromatization. Due to this, the echo-type IXS spectrometers are broadband, and thus have a potential to simultaneously provide dramatically increased signal strength, reduced measurement times, and higher resolution compared to the traditional narrow-band scanning-type IXS spectrometers. The theory of x-ray echo spectrometers presented earlier [Yu. Shvyd'ko, Phys. Rev. Lett. 116, 080801 (2016), 10.1103/PhysRevLett.116.080801] is developed here further with a focus on questions of practical importance, which could facilitate optical design and assessment of the feasibility and performance of the echo spectrometers. Among others, the following questions are addressed: spectral resolution, refocusing condition, echo spectrometer tolerances, refocusing condition adjustment, effective beam size on the sample, spectral window of imaging and scanning range, impact of the secondary source size on the spectral resolution, angular dispersive optics, focusing and collimating optics, and detector's spatial resolution. Examples of optical designs and characteristics of echo spectrometers with 1-meV and 0.1-meV resolutions are presented.

  3. Using spectral methods to obtain particle size information from optical data: applications to measurements from CARES 2010

    Science.gov (United States)

    Atkinson, Dean B.; Pekour, Mikhail; Chand, Duli; Radney, James G.; Kolesar, Katheryn R.; Zhang, Qi; Setyan, Ari; O'Neill, Norman T.; Cappa, Christopher D.

    2018-04-01

    Multi-wavelength in situ aerosol extinction, absorption and scattering measurements made at two ground sites during the 2010 Carbonaceous Aerosols and Radiative Effects Study (CARES) are analyzed using a spectral deconvolution method that allows extraction of particle-size-related information, including the fraction of extinction produced by the fine-mode particles and the effective radius of the fine mode. The spectral deconvolution method is typically applied to analysis of remote sensing measurements. Here, its application to in situ measurements allows for comparison with more direct measurement methods and validation of the retrieval approach. Overall, the retrieved fine-mode fraction and effective radius compare well with other in situ measurements, including size distribution measurements and scattering and absorption measurements made separately for PM1 and PM10, although there were some periods during which the different methods yielded different results. One key contributor to differences between the results obtained is the alternative, spectrally based definitions of fine and coarse modes from the optical methods, relative to instruments that use a physically defined cut point. These results indicate that for campaigns where size, composition and multi-wavelength optical property measurements are made, comparison of the results can result in closure or can identify unusual circumstances. The comparison here also demonstrates that in situ multi-wavelength optical property measurements can be used to determine information about particle size distributions in situations where direct size distribution measurements are not available.

  4. Using spectral methods to obtain particle size information from optical data: applications to measurements from CARES 2010

    Directory of Open Access Journals (Sweden)

    D. B. Atkinson

    2018-04-01

    Full Text Available Multi-wavelength in situ aerosol extinction, absorption and scattering measurements made at two ground sites during the 2010 Carbonaceous Aerosols and Radiative Effects Study (CARES are analyzed using a spectral deconvolution method that allows extraction of particle-size-related information, including the fraction of extinction produced by the fine-mode particles and the effective radius of the fine mode. The spectral deconvolution method is typically applied to analysis of remote sensing measurements. Here, its application to in situ measurements allows for comparison with more direct measurement methods and validation of the retrieval approach. Overall, the retrieved fine-mode fraction and effective radius compare well with other in situ measurements, including size distribution measurements and scattering and absorption measurements made separately for PM1 and PM10, although there were some periods during which the different methods yielded different results. One key contributor to differences between the results obtained is the alternative, spectrally based definitions of fine and coarse modes from the optical methods, relative to instruments that use a physically defined cut point. These results indicate that for campaigns where size, composition and multi-wavelength optical property measurements are made, comparison of the results can result in closure or can identify unusual circumstances. The comparison here also demonstrates that in situ multi-wavelength optical property measurements can be used to determine information about particle size distributions in situations where direct size distribution measurements are not available.

  5. UV-Vis-IR spectral complex refractive indices and optical properties of brown carbon aerosol from biomass burning

    Science.gov (United States)

    Sumlin, Benjamin J.; Heinson, Yuli W.; Shetty, Nishit; Pandey, Apoorva; Pattison, Robert S.; Baker, Stephen; Hao, Wei Min; Chakrabarty, Rajan K.

    2018-02-01

    Constraining the complex refractive indices, optical properties and size of brown carbon (BrC) aerosols is a vital endeavor for improving climate models and satellite retrieval algorithms. Smoldering wildfires are the largest source of primary BrC, and fuel parameters such as moisture content, source depth, geographic origin, and fuel packing density could influence the properties of the emitted aerosol. We measured in situ spectral (375-1047 nm) optical properties of BrC aerosols emitted from smoldering combustion of Boreal and Indonesian peatlands across a range of these fuel parameters. Inverse Lorenz-Mie algorithms used these optical measurements along with simultaneously measured particle size distributions to retrieve the aerosol complex refractive indices (m = n + iκ). Our results show that the real part n is constrained between 1.5 and 1.7 with no obvious functionality in wavelength (λ), moisture content, source depth, or geographic origin. With increasing λ from 375 to 532 nm, κ decreased from 0.014 to 0.003, with corresponding increase in single scattering albedo (SSA) from 0.93 to 0.99. The spectral variability of κ follows the Kramers-Kronig dispersion relation for a damped harmonic oscillator. For λ ≥ 532 nm, both κ and SSA showed no spectral dependency. We discuss differences between this study and previous work. The imaginary part κ was sensitive to changes in FPD, and we hypothesize mechanisms that might help explain this observation.

  6. Heavy carriers, non-drude optical conductivity and transfer of spectral weight in MnSi

    International Nuclear Information System (INIS)

    Mena, F.P.; Damascelli, A.; Marel, D. van der; Fath, M.; Menovsky, A.A.; Mydosh, J.A.

    2004-01-01

    The optical properties of the weak magnetic metal MnSi were determined using reflectance at 80 deg. (2-800 meV) and ellipsometry (0.8-4.5 eV). At low frequencies in the magnetic phase we observe a departure of the optical conductivity from Drude behavior: m*(ω)/m is strongly frequency dependent and 1/τ(ω) is approximately linear in frequency. In fact, we show that σ(ω)/σ(0)=(1+iω/Γ) -0.5 . Moreover, in the magnetic phase, the plasma frequency shifts to the red indicating that spectral weight is transferred to high frequencies. This is opposite to the effect recently seen in other magnetic compounds

  7. Subretinal fibrosis and uveitis: a spectral domain OCT study of its evolution and the minimal therapeutic effect of the off-label treatment with ranibizumab.

    Science.gov (United States)

    Symeonidis, Chrysanthos; Dastiridou, Anna; Konidaris, Vasilis; Brazitikos, Periklis; Androudi, Sofia

    2014-12-01

    The subretinal fibrosis and uveitis (SFU) syndrome is a rare multifocal posterior uveitis characterized by progressive subretinal fibrosis and significant visual loss. Slit-lamp examination, dilated fundoscopy, fluorescein angiography, Spectral Domain-Optical Coherence Tomography (SD-OCT) and laboratory testing were employed. A 52-year-old male presented with bilateral (best-corrected visual acuity: 2/10) visual loss. Clinical examination revealed bilateral anterior uveitis with posterior synechiae and posterior uveitis. Medical workup revealed no pathologic findings. Treatment included 1 gr intravenous prednisone followed by oral prednisone, immunosuppresive therapy and three ranibizumab injections in the right eye with no improvement. One year later, there was significant subretinal fibrosis. In the second year follow-up, the picture was slightly worse, with persisting bilateral macular edema and fibrosis. This is the first SFU syndrome report monitored with SD-OCT. This novel imaging modality can localize the lesion level, guide the therapeutic approach and may prove helpful in assessing disease prognosis.

  8. Hyper-spectral modulation fluorescent imaging using double acousto-optical tunable filter based on TeO2-crystals

    International Nuclear Information System (INIS)

    Zaytsev, Kirill I; Perchik, Alexey V; Chernomyrdin, Nikita V; Yurchenko, Stanislav O; Kudrin, Konstantin G; Reshetov, Igor V

    2015-01-01

    We have proposed a method for hyper-spectral fluorescent imaging based on acousto-optical filtering. The object of interest was pumped using ultraviolet radiation of mercury lamp equipped with monochromatic excitation filter with the window of transparency centered at 365 nm. Double TeO 2 -based acousto-optical filter, tunable in range from 430 to 780 nm and having 2 nm bandwidth of spectral transparency, was used in order to detect quasimonochromatic images of object fluorescence. Modulating of ultraviolet pump intensity was used in order to reduce an impact of non-fluorescent background on the sample fluorescent imaging. The technique for signal-to-noise ratio improvement, based on fluorescence intensity estimation via digital processing of modulated video sequence of fluorescent object, was introduced. We have implemented the proposed technique for the test sample studying and we have discussed its possible applications

  9. Geometric optimisation of an accurate cosine correcting optic fibre coupler for solar spectral measurement

    Science.gov (United States)

    Cahuantzi, Roberto; Buckley, Alastair

    2017-09-01

    Making accurate and reliable measurements of solar irradiance is important for understanding performance in the photovoltaic energy sector. In this paper, we present design details and performance of a number of fibre optic couplers for use in irradiance measurement systems employing remote light sensors applicable for either spectrally resolved or broadband measurement. The angular and spectral characteristics of different coupler designs are characterised and compared with existing state-of-the-art commercial technology. The new coupler designs are fabricated from polytetrafluorethylene (PTFE) rods and operate through forward scattering of incident sunlight on the front surfaces of the structure into an optic fibre located in a cavity to the rear of the structure. The PTFE couplers exhibit up to 4.8% variation in scattered transmission intensity between 425 nm and 700 nm and show minimal specular reflection, making the designs accurate and reliable over the visible region. Through careful geometric optimization near perfect cosine dependence on the angular response of the coupler can be achieved. The PTFE designs represent a significant improvement over the state of the art with less than 0.01% error compared with ideal cosine response for angles of incidence up to 50°.

  10. Geometric optimisation of an accurate cosine correcting optic fibre coupler for solar spectral measurement.

    Science.gov (United States)

    Cahuantzi, Roberto; Buckley, Alastair

    2017-09-01

    Making accurate and reliable measurements of solar irradiance is important for understanding performance in the photovoltaic energy sector. In this paper, we present design details and performance of a number of fibre optic couplers for use in irradiance measurement systems employing remote light sensors applicable for either spectrally resolved or broadband measurement. The angular and spectral characteristics of different coupler designs are characterised and compared with existing state-of-the-art commercial technology. The new coupler designs are fabricated from polytetrafluorethylene (PTFE) rods and operate through forward scattering of incident sunlight on the front surfaces of the structure into an optic fibre located in a cavity to the rear of the structure. The PTFE couplers exhibit up to 4.8% variation in scattered transmission intensity between 425 nm and 700 nm and show minimal specular reflection, making the designs accurate and reliable over the visible region. Through careful geometric optimization near perfect cosine dependence on the angular response of the coupler can be achieved. The PTFE designs represent a significant improvement over the state of the art with less than 0.01% error compared with ideal cosine response for angles of incidence up to 50°.

  11. Retrieval of spectral aerosol optical thickness over land using ocean color sensors MERIS and SeaWiFS

    Directory of Open Access Journals (Sweden)

    W. von Hoyningen-Huene

    2011-02-01

    Full Text Available For the determination of aerosol optical thickness (AOT Bremen AErosol Retrieval (BAER has been developed. Method and main features on the aerosol retrieval are described together with validation and results. The retrieval separates the spectral aerosol reflectance from surface and Rayleigh path reflectance for the shortwave range of the measured spectrum of top-of-atmosphere reflectance for wavelength less than 0.670 μm. The advantage of MERIS (Medium Resolution Imaging Spectrometer on the Environmental Satellite – ENVISAT – of the European Space Agency – ESA and SeaWiFS (Sea viewing Wide Field Sensor on OrbView-2 spacecraft observations is the availability of several spectral channels in the blue and visible range enabling the spectral determination of AOT in 7 (or 6 channels (0.412–0.670 μm and additionally channels in the NIR, which can be used to characterize the surface properties. A dynamical spectral surface reflectance model for different surface types is used to obtain the spectral surface reflectance for this separation. The normalized differential vegetation index (NDVI, taken from the satellite observations, is the model input. Further surface bi-directional reflectance distribution function (BRDF is considered by the Raman-Pinty-Verstraete (RPV model. Spectral AOT is obtained from aerosol reflectance using look-up-tables, obtained from radiative transfer calculations with given aerosol phase functions and single scattering albedos either from aerosol models, given by model package "optical properties of aerosol components" (OPAC or from experimental campaigns. Validations of the obtained AOT retrieval results with data of Aerosol Robotic Network (AERONET over Europe gave a preference for experimental phase functions derived from almucantar measurements. Finally long-term observations of SeaWiFS have been investigated for 11 year trends in AOT. Western European regions have negative trends with decreasing AOT with time

  12. Multi-spectral optical scanners for commercial earth observation missions

    Science.gov (United States)

    Schröter, Karin; Engel, Wolfgang; Berndt, Klaus

    2017-11-01

    In recent years, a number of commercial Earth observation missions have been initiated with the aim to gather data in the visible and near-infrared wavelength range. Some of these missions aim at medium resolution (5 to 10 m) multi-spectral imaging with the special background of daily revisiting. Typical applications aim at monitoring of farming area for growth control and harvest prediction, irrigation control, or disaster monitoring such as hail damage in farming, or flood survey. In order to arrive at profitable business plans for such missions, it is mandatory to establish the space segment, i.e. the spacecraft with their opto -electronic payloads, at minimum cost while guaranteeing maximum reliability for mission success. As multiple spacecraft are required for daily revisiting, the solutions are typically based on micro-satellites. This paper presents designs for multi-spectral opto-electric scanners for this type of missions. These designs are drive n by minimum mass and power budgets of microsatellites, and the need for minimum cost. As a consequence, it is mandatory to arrive at thermally robust, compact telescope designs. The paper gives a comparison between refractive, catadioptric, and TMA optics. For mirror designs, aluminium and Zerodur mirror technologies are briefly discussed. State-of-the art focal plane designs are presented. The paper also addresses the choice of detector technologies such as CCDs and CMOS Active Pixel Sensors. The electronics of the multi-spectral scanners represent the main design driver regarding power consumption, reliability, and (most often) cost. It can be subdivided into the detector drive electronics, analog and digital data processing chains, the data mass memory unit, formatting and down - linking units, payload control electronics, and local power supply. The paper gives overviews and trade-offs between data compression strategies and electronics solutions, mass memory unit designs, and data formatting approaches

  13. Towards the use of bioresorbable fibers in time-domain diffuse optics.

    Science.gov (United States)

    Di Sieno, Laura; Boetti, Nadia G; Dalla Mora, Alberto; Pugliese, Diego; Farina, Andrea; Konugolu Venkata Sekar, Sanathana; Ceci-Ginistrelli, Edoardo; Janner, Davide; Pifferi, Antonio; Milanese, Daniel

    2018-01-01

    In the last years bioresorbable materials are gaining increasing interest for building implantable optical components for medical devices. In this work we show the fabrication of bioresorbable optical fibers designed for diffuse optics applications, featuring large core diameter (up to 200 μm) and numerical aperture (0.17) to maximize the collection efficiency of diffused light. We demonstrate the suitability of bioresorbable fibers for time-domain diffuse optical spectroscopy firstly checking the intrinsic performances of the setup by acquiring the instrument response function. We then validate on phantoms the use of bioresorbable fibers by applying the MEDPHOT protocol to assess the performance of the system in measuring optical properties (namely, absorption and scattering coefficients) of homogeneous media. Further, we show an ex-vivo validation on a chicken breast by measuring the absorption and scattering spectra in the 500-1100 nm range using interstitially inserted bioresorbable fibers. This work represents a step toward a new way to look inside the body using optical fibers that can be implanted in patients. These fibers could be useful either for diagnostic (e. g. for monitoring the evolution after surgical interventions) or treatment (e. g. photodynamic therapy) purposes. Picture: Microscopy image of the 100 μm core bioresorbable fiber. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Quantitative functional optical imaging of the human skin using multi-spectral imaging

    International Nuclear Information System (INIS)

    Kainerstorfer, J. M.

    2010-01-01

    Light tissue interactions can be described by the physical principles of absorption and scattering. Based on those parameters, different tissue types and analytes can be distinguished. Extracting blood volume and oxygenation is of particular interest in clinical routines for tumor diagnostics and treatment follow up, since they are parameters of angiogenic processes. The quantification of those analytes in tissue can be done by physical modeling of light tissue interaction. The physical model used here is the random walk theory. However, for quantification and clinical usefulness, one has to account for multiple challenges. First, one must consider the effect of topology of the sample on measured physical parameters. Second, diffusion of light inside the tissue is dependent on the structure of the sample imaged. Thus, the structural conformation has to be taken into account. Third, clinical translation of imaging modalities is often hindered due to the complicated post-processing of data, not providing results in real-time. In this thesis, two imaging modalities are being utilized, where the first one, diffuse multi-spectral imaging, is based on absorption contrast and spectral characteristics and the second one, Optical Coherence Tomography (OCT), is based on scattering changes within the tissue. Multi-spectral imaging can provide spatial distributions of blood volume and blood oxygenation and OCT yields 3D structural images with micrometer resolution. In order to address the challenges mentioned above, a curvature correction algorithm for taking the topology into account was developed. Without taking curvature of the object into account, reconstruction of optical properties is not accurate. The method developed removes this artifact and recovers the underlying data, without the necessity of measuring the object's shape. The next step was to recover blood volume and oxygenation values in real time. Principal Component Analysis (PCA) on multi spectral images is

  15. Observation of magnetic domains using a reflection-mode scanning near-field optical microscope

    OpenAIRE

    SHVETS, IGOR

    1997-01-01

    PUBLISHED It is demonstrated that it is possible to image magnetic domains with a resolution of better than 60 nm with the Kerr effect in a reflection-mode scanning near-field optical microscope. Images taken of tracks of thermomagnetically prewritten bits in a Co/Pt multilayer structure magnetized out-of plane showed optical features in a track pattern whose appearance was determined by the position of an analyzer in front of the photomultiplier tube. These features were not apparent in t...

  16. Observation of magnetic domains using a reflection mode scanning near-field optical microscope

    OpenAIRE

    Durkam, C.; Shvets, I.V.; Lodder, J.C.

    1997-01-01

    It is demonstrated that it is possible to image magnetic domains with a resolution of better than 60 nm with the Kerr effect in a reflection-mode scanning near-field optical microscope. Images taken of tracks of thermomagnetically prewritten bits in a Co/Pt multilayer structure magnetized out-of plane showed optical features in a track pattern whose appearance was determined by the position of an analyzer in front of the photomultiplier tube. These features were not apparent in the topography...

  17. SAFARI optical system architecture and design concept

    Science.gov (United States)

    Pastor, Carmen; Jellema, Willem; Zuluaga-Ramírez, Pablo; Arrazola, David; Fernández-Rodriguez, M.; Belenguer, Tomás.; González Fernández, Luis M.; Audley, Michael D.; Evers, Jaap; Eggens, Martin; Torres Redondo, Josefina; Najarro, Francisco; Roelfsema, Peter

    2016-07-01

    SpicA FAR infrared Instrument, SAFARI, is one of the instruments planned for the SPICA mission. The SPICA mission is the next great leap forward in space-based far-infrared astronomy and will study the evolution of galaxies, stars and planetary systems. SPICA will utilize a deeply cooled 2.5m-class telescope, provided by European industry, to realize zodiacal background limited performance, and high spatial resolution. The instrument SAFARI is a cryogenic grating-based point source spectrometer working in the wavelength domain 34 to 230 μm, providing spectral resolving power from 300 to at least 2000. The instrument shall provide low and high resolution spectroscopy in four spectral bands. Low Resolution mode is the native instrument mode, while the high Resolution mode is achieved by means of a Martin-Pupplet interferometer. The optical system is all-reflective and consists of three main modules; an input optics module, followed by the Band and Mode Distributing Optics and the grating Modules. The instrument utilizes Nyquist sampled filled linear arrays of very sensitive TES detectors. The work presented in this paper describes the optical design architecture and design concept compatible with the current instrument performance and volume design drivers.

  18. Receiver sensitivity improvement in spectrally-efficient guard-band twin-SSB-OFDM using an optical IQ modulator

    Science.gov (United States)

    Chen, Ming; Peng, Miao; Zhou, Hui; Zheng, Zhiwei; Tang, Xionggui; Maivan, Lap

    2017-12-01

    To further improve receiver sensitivity of spectrally-efficient guard-band direct-detection optical orthogonal frequency-division multiplexing (OFDM) with twin single-side-band (SSB) modulation technique, an optical IQ modulator (IQM) is employed to optimize optical carrier-to-signal power ratio (CSPR). The CSPRs for the guard-band twin-SSB-OFDM signal generated by using dual-drive Mach-Zehnder modulator (DD-MZM) and optical IQM are theoretically analyzed and supported by simulations. The optimal CSPR for the two types of guard-band twin-SSB-OFDM are identified. The simulations exhibit that the error vector magnitude (EVM) performance of the IQM-enabled guard-band twin-SSB-OFDM is improved by more than 4-dB compared to that of the twin-SSB-OFDM enabled by DD-MZM after 80-km single-mode fiber (SMF) transmission. In addition, more than 3-dB and 10 dB receiver sensitivity improvements in terms of received optical power (ROP) and optical signal-to-noise ratio (OSNR) are also achieved, respectively.

  19. Recent progress on high-speed optical transmission

    Directory of Open Access Journals (Sweden)

    Jianjun Yu

    2016-05-01

    Full Text Available The recently reported high spectral efficiency (SE and high-baud-rate signal transmission are all based on digital coherent optical communications and digital signal processing (DSP. DSP simplifies the reception of advanced modulation formats and also enables the major electrical and optical impairments to be processed and compensated in the digital domain, at the transmitter or receiver side. In this paper, we summarize the research progress on high-speed signal generation and detection and also show the progress on DSP for high-speed signal detection. We also report the latest progress on multi-core and multi-mode multiplexing.

  20. Retinal nerve fiber layer thickness map determined from optical coherence tomography images

    NARCIS (Netherlands)

    Mujat, M.; Chan, R. C.; Cense, B.; Park, B.H.; Joo, C.; Akkin, T.; Chen, TC; de Boer, JF

    2005-01-01

    We introduce a method to determine the retinal nerve fiber layer (RNFL) thickness in OCT images based on anisotropic noise suppression and deformable splines. Spectral-Domain Optical Coherence Tomography (SDOCT) data was acquired at 29 kHz A-line rate with a depth resolution of 2.6 mum and a depth

  1. Dynamic analysis of smart composite beams by using the frequency domain spectral element method

    Energy Technology Data Exchange (ETDEWEB)

    Park, Il Wook; Lee, Usik [Inha Univ., Incheon (Korea, Republic of)

    2012-08-15

    To excite or measure the dynamic responses of a laminated composite structure for the active controls of vibrations or noises, wafertype piezoelectric transducers are often bonded on the surface of the composite structure to form a multi layer smart composite structure. Thus, for such smart composite structures, it is very important to develop and use a very reliable mathematical and/or computational model for predicting accurate dynamic characteristics. In this paper, the axial-bending coupled equations of motion and boundary conditions are derived for two layer smart composite beams by using the Hamilton's principle with Lagrange multipliers. The spectral element model is then formulated in the frequency domain by using the variation approach. Through some numerical examples, the extremely high accuracy of the present spectral element model is verified by comparing with the solutions by the conventional finite element model provided in this paper. The effects of the lay up of composite laminates and surface bonded wafer type piezoelectric (PZT) layer on the dynamics and wave characteristics of smart composite beams are investigated. The effective constraint forces at the interface between the base beam and PZT layer are also investigated via Lagrange multipliers.

  2. Polarization modeling and predictions for DKIST part 3: focal ratio and thermal dependencies of spectral polarization fringes and optic retardance

    Science.gov (United States)

    Harrington, David M.; Sueoka, Stacey R.

    2018-01-01

    Data products from high spectral resolution astronomical polarimeters are often limited by fringes. Fringes can skew derived magnetic field properties from spectropolarimetric data. Fringe removal algorithms can also corrupt the data if the fringes and object signals are too similar. For some narrow-band imaging polarimeters, fringes change the calibration retarder properties and dominate the calibration errors. Systems-level engineering tools for polarimetric instrumentation require accurate predictions of fringe amplitudes, periods for transmission, diattenuation, and retardance. The relevant instabilities caused by environmental, thermal, and optical properties can be modeled and mitigation tools developed. We create spectral polarization fringe amplitude and temporal instability predictions by applying the Berreman calculus and simple interferometric calculations to optics in beams of varying F/ number. We then apply the formalism to superachromatic six-crystal retarders in converging beams under beam thermal loading in outdoor environmental conditions for two of the world's largest observatories: the 10-m Keck telescope and the Daniel K. Inouye Solar Telescope (DKIST). DKIST will produce a 300-W optical beam, which has imposed stringent requirements on the large diameter six-crystal retarders, dichroic beamsplitters, and internal optics. DKIST retarders are used in a converging beam with F/ ratios between 8 and 62. The fringe spectral periods, amplitudes, and thermal models of retarder behavior assisted DKIST optical designs and calibration plans with future application to many astronomical spectropolarimeters. The Low Resolution Imaging Spectrograph with polarimetry instrument at Keck also uses six-crystal retarders in a converging F / 13 beam in a Cassegrain focus exposed to summit environmental conditions providing observational verification of our predictions.

  3. Coordinated Multi-layer Multi-domain Optical Network (COMMON) for Large-Scale Science Applications (COMMON)

    Energy Technology Data Exchange (ETDEWEB)

    Vokkarane, Vinod [University of Massachusetts

    2013-09-01

    We intend to implement a Coordinated Multi-layer Multi-domain Optical Network (COMMON) Framework for Large-scale Science Applications. In the COMMON project, specific problems to be addressed include 1) anycast/multicast/manycast request provisioning, 2) deployable OSCARS enhancements, 3) multi-layer, multi-domain quality of service (QoS), and 4) multi-layer, multidomain path survivability. In what follows, we outline the progress in the above categories (Year 1, 2, and 3 deliverables).

  4. Energy density engineering via zero-admittance domains in all-dielectric stratified materials

    Science.gov (United States)

    Amra, Claude; Zerrad, Myriam; Lemarchand, Fabien; Lereu, Aude; Passian, Ali; Zapien, Juan Antonio; Lequime, Michel

    2018-02-01

    Emerging photonic, sensing, and quantum applications require high fields and tight localization but low power consumption. Spatial, spectral, and magnitude control of electromagnetic fields is of key importance for enabling experiments in atomic, molecular, and optical physics. We introduce the concept of zero-admittance domains as a mechanism for tailoring giant optical fields bound within or on the surface of dielectric media. The described mechanism permits the creation of highly localized fields of extreme amplitudes simultaneously for incident photons of multiple wavelengths and incidence angles but arbitrary polarization states. No material constraints are placed upon the bounding media. Both intrinsic and extrinsic potential practical limitations of the predicted field enhancement are analyzed and applications relevant to optical sensors and microsources are briefly discussed.

  5. ASIC-enabled High Resolution Optical Time Domain Reflectometer

    Science.gov (United States)

    Skendzic, Sandra

    Fiber optics has become the preferred technology in communication systems because of what it has to offer: high data transmission rates, immunity to electromagnetic interference, and lightweight, flexible cables. An optical time domain reflectometer (OTDR) provides a convenient method of locating and diagnosing faults (e.g. break in a fiber) along a fiber that can obstruct crucial optical pathways. Both the ability to resolve the precise location of the fault and distinguish between two discrete, closely spaced faults are figures of merit. This thesis presents an implementation of a high resolution OTDR through the use of a compact and programmable ASIC (application specific integrated circuit). The integration of many essential OTDR functions on a single chip is advantageous over existing commercial instruments because it enables small, lightweight packaging, and offers low power and cost efficiency. Furthermore, its compactness presents the option of placing multiple ASICs in parallel, which can conceivably ease the characterization of densely populated fiber optic networks. The OTDR ASIC consists of a tunable clock, pattern generator, precise timer, electrical receiver, and signal sampling circuit. During OTDR operation, the chip generates narrow electrical pulse, which can then be converted to optical format when coupled with an external laser diode driver. The ASIC also works with an external photodetector to measure the timing and amplitude of optical reflections in a fiber. It has a 1 cm sampling resolution, which allows for a 2 cm spatial resolution. While this OTDR ASIC has been previously demonstrated for multimode fiber fault diagnostics, this thesis focuses on extending its functionality to single mode fiber. To validate this novel approach to OTDR, this thesis is divided into five chapters: (1) introduction, (2) implementation, (3), performance of ASIC-based OTDR, (4) exploration in optical pre-amplification with a semiconductor optical amplifier, and

  6. XOP: a multiplatform graphical user interface for synchrotron radiation spectral and optics calculations

    Science.gov (United States)

    Sanchez del Rio, Manuel; Dejus, Roger J.

    1997-11-01

    XOP (X-ray OPtics utilities) is a graphical user interface (GUI) created to execute several computer programs that calculate the basic information needed by a synchrotron beamline scientist (designer or experimentalist). Typical examples of such calculations are: insertion device (undulator or wiggler) spectral and angular distributions, mirror and multilayer reflectivities, and crystal diffraction profiles. All programs are provided to the user under a unified GUI, which greatly simplifies their execution. The XOP optics applications (especially mirror calculations) take their basic input (optical constants, compound and mixture tables) from a flexible file-oriented database, which allows the user to select data from a large number of choices and also to customize their own data sets. XOP includes many mathematical and visualization capabilities. It also permits the combination of reflectivities from several mirrors and filters, and their effect, onto a source spectrum. This feature is very useful when calculating thermal load on a series of optical elements. The XOP interface is written in the IDL (Interactive Data Language). An embedded version of XOP, which freely runs under most Unix platforms (HP, Sun, Dec, Linux, etc) and under Windows95 and NT, is available upon request.

  7. XOP: A multiplatform graphical user interface for synchrotron radiation spectral and optics calculations

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez del Rio, M. [European Synchrotron Radiation Facility, Grenoble (France); Dejus, R.J. [Argonne National Lab., IL (United States). Advanced Photon Source

    1997-09-01

    XOP (X-ray OPtics utilities) is a graphical user interface (GUI) created to execute several computer programs that calculate the basic information needed by a synchrotron beamline scientist (designer or experimentalist). Typical examples of such calculations are: insertion device (undulator or wiggler) spectral and angular distributions, mirror and multilayer reflectivities, and crystal diffraction profiles. All programs are provided to the user under a unified GUI, which greatly simplifies their execution. The XOP optics applications (especially mirror calculations) take their basic input (optical constants, compound and mixture tables) from a flexible file-oriented database, which allows the users to select data from a large number of choices and also to customize their own data sets. XOP includes many mathematical and visualization capabilities. It also permits the combination of reflectivities from several mirrors and filters, and their effect, onto a source spectrum. This feature is very useful when calculating thermal load on a series of optical elements. The XOP interface is written in the IDL (Interactive Data Language). An embedded version of XOP, which freely runs under most Unix platforms (HP, Sun, Dec, Linux, etc) and under Windows95 and NT, is available upon request.

  8. Spectral-domain low-coherence interferometry for phase-sensitive measurement of Faraday rotation at multiple depths.

    Science.gov (United States)

    Yeh, Yi-Jou; Black, Adam J; Akkin, Taner

    2013-10-10

    We describe a method for differential phase measurement of Faraday rotation from multiple depth locations simultaneously. A polarization-maintaining fiber-based spectral-domain interferometer that utilizes a low-coherent light source and a single camera is developed. Light decorrelated by the orthogonal channels of the fiber is launched on a sample as two oppositely polarized circular states. These states reflect from sample surfaces and interfere with the corresponding states of the reference arm. A custom spectrometer, which is designed to simplify camera alignment, separates the orthogonal channels and records the interference-related oscillations on both spectra. Inverse Fourier transform of the spectral oscillations in k-space yields complex depth profiles, whose amplitudes and phase difference are related to reflectivity and Faraday rotation within the sample, respectively. Information along a full depth profile is produced at the camera speed without performing an axial scan for a multisurface sample. System sensitivity for the Faraday rotation measurement is 0.86 min of arc. Verdet constants of clear liquids and turbid media are measured at 687 nm.

  9. Determination of the optical properties of melanin-pigmented human skin equivalents using terahertz time-domain spectroscopy

    Science.gov (United States)

    Lipscomb, Dawn; Echchgadda, Ibtissam; Peralta, Xomalin G.; Wilmink, Gerald J.

    2013-02-01

    Terahertz time-domain spectroscopy (THz-TDS) methods have been utilized in previous studies in order to characterize the optical properties of skin and its primary constituents (i.e., water, collagen, and keratin). However, similar experiments have not yet been performed to investigate whether melanocytes and the melanin pigment that they synthesize contribute to skin's optical properties. In this study, we used THz-TDS methods operating in transmission geometry to measure the optical properties of in vitro human skin equivalents with or without normal human melanocytes. Skin equivalents were cultured for three weeks to promote gradual melanogenesis, and THz time domain data were collected at various time intervals. Frequency-domain analysis techniques were performed to determine the index of refraction (n) and absorption coefficient (μa) for each skin sample over the frequency range of 0.1-2.0 THz. We found that for all samples as frequency increased, n decreased exponentially and the μa increased linearly. Additionally, we observed that skin samples with higher levels of melanin exhibited greater n and μa values than the non-pigmented samples. Our results indicate that melanocytes and the degree of melanin pigmentation contribute in an appreciable manner to the skin's optical properties. Future studies will be performed to examine whether these contributions are observed in human skin in vivo.

  10. THE POTENTIAL IMPORTANCE OF BINARY EVOLUTION IN ULTRAVIOLET-OPTICAL SPECTRAL FITTING OF EARLY-TYPE GALAXIES

    International Nuclear Information System (INIS)

    Li, Zhongmu; Mao, Caiyan; Chen, Li; Zhang, Qian; Li, Maocai

    2013-01-01

    Most galaxies possibly contain some binaries, and more than half of Galactic hot subdwarf stars, which are thought to be a possible origin of the UV-upturn of old stellar populations, are found in binaries. However, the effect of binary evolution has not been taken into account in most works on the spectral fitting of galaxies. This paper studies the role of binary evolution in the spectral fitting of early-type galaxies, via a stellar population synthesis model including both single and binary star populations. Spectra from ultraviolet to optical bands are fitted to determine a few galaxy parameters. The results show that the inclusion of binaries in stellar population models may lead to obvious change in the determination of some parameters of early-type galaxies and therefore it is potentially important for spectral studies. In particular, the ages of young components of composite stellar populations become much older when using binary star population models instead of single star population models. This implies that binary star population models will measure significantly different star formation histories for early-type galaxies compared to single star population models. In addition, stellar population models with binary interactions on average measure larger dust extinctions than single star population models. This suggests that when binary star population models are used, negative extinctions are possibly no longer necessary in the spectral fitting of galaxies (see previous works, e.g., Cid Fernandes et al. for comparison). Furthermore, it is shown that optical spectra have strong constraints on stellar age while UV spectra have strong constraints on binary fraction. Finally, our results suggest that binary star population models can provide new insight into the stellar properties of globular clusters

  11. Optical phase conjugation for time-domain undoing of dispersive self-phase-modulation effects

    International Nuclear Information System (INIS)

    Fisher, R.A.; Suydam, B.R.; Yevick, D.

    1983-01-01

    We show that the temporal distortion and spectral broadening of a pulse generated by the combined effects of group-velocity dispersion and self-phase modulation is removed by reflection of a cw-pumped, broadband, unity-reflecting Kerr-like optical phase conjugator followed by retraversal of the nonlinear medium. We also examine numerically the effects of finite linear loss in the material, of nonunity conjugate reflectivity, and of finite conjugator thickness

  12. Information content in spectral dependencies of optical unit volume parameters under action of He-Ne laser on blood

    Science.gov (United States)

    Khairullina, Alphiya Y.; Oleinik, Tatiana V.

    1995-01-01

    Our previous works concerned with the development of methods for studying blood and action of low-intensity laser radiation on blood and erythrocyte suspensions had shown the light- scattering methods gave a large body of information on a medium studied due to the methodological relationship between irradiation processes and techniques for investigations. Detail analysis of spectral diffuse reflectivities and transmissivities of optically thick blood layers, spectral absorptivities calculated on this basis over 600 - 900 nm, by using different approximations, for a pathological state owing to hypoxia testifies to the optical significance of not only hemoglobin derivatives but also products of hemoglobin decomposition. Laser action on blood is specific and related to an initial state of blood absorption due to different composition of chromoproteids. This work gives the interpretation of spectral observations. Analysis of spectral dependencies of the exinction coefficient e, mean cosine m of phase function, and parameter Q equals (epsilon) (1-(mu) )H/(lambda) (H - hematocrit) testifies to decreasing the relative index of refraction of erythrocytes and to morphological changes during laser action under pathology owing to hypoxia. The possibility to obtain physical and chemical information on the state of blood under laser action in vivo is shown to be based on the method proposed by us for calculating multilayered structures modeling human organs and on the technical implementation of this method.

  13. THE TIME-DOMAIN SPECTROSCOPIC SURVEY: UNDERSTANDING THE OPTICALLY VARIABLE SKY WITH SEQUELS IN SDSS-III

    International Nuclear Information System (INIS)

    Ruan, John J.; Anderson, Scott F.; Davenport, James R. A.; Green, Paul J.; Morganson, Eric; Eracleous, Michael; Brandt, William N.; Myers, Adam D.; Badenes, Carles; Bershady, Matthew A.; Chambers, Kenneth C.; Flewelling, Heather; Kaiser, Nick; Dawson, Kyle S.; Heckman, Timothy M.; Isler, Jedidah C.; Kneib, Jean-Paul; MacLeod, Chelsea L.; Ross, Nicholas P.; Paris, Isabelle

    2016-01-01

    The Time-Domain Spectroscopic Survey (TDSS) is an SDSS-IV eBOSS subproject primarily aimed at obtaining identification spectra of ∼220,000 optically variable objects systematically selected from SDSS/Pan-STARRS1 multi-epoch imaging. We present a preview of the science enabled by TDSS, based on TDSS spectra taken over ∼320 deg 2 of sky as part of the SEQUELS survey in SDSS-III, which is in part a pilot survey for eBOSS in SDSS-IV. Using the 15,746 TDSS-selected single-epoch spectra of photometrically variable objects in SEQUELS, we determine the demographics of our variability-selected sample and investigate the unique spectral characteristics inherent in samples selected by variability. We show that variability-based selection of quasars complements color-based selection by selecting additional redder quasars and mitigates redshift biases to produce a smooth quasar redshift distribution over a wide range of redshifts. The resulting quasar sample contains systematically higher fractions of blazars and broad absorption line quasars than from color-selected samples. Similarly, we show that M dwarfs in the TDSS-selected stellar sample have systematically higher chromospheric active fractions than the underlying M-dwarf population based on their H α emission. TDSS also contains a large number of RR Lyrae and eclipsing binary stars with main-sequence colors, including a few composite-spectrum binaries. Finally, our visual inspection of TDSS spectra uncovers a significant number of peculiar spectra, and we highlight a few cases of these interesting objects. With a factor of ∼15 more spectra, the main TDSS survey in SDSS-IV will leverage the lessons learned from these early results for a variety of time-domain science applications.

  14. Multi-Configuration Matched Spectral Filter Core, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — OPTRA proposes an open-architecture spectral gas sensor based on compressive sensing concepts employed for both spatial and spectral domains. Our matched spectral...

  15. The effect of silver on the optical, spectral-luminescent, and crystallization properties of bromide photo-thermo-refractive glasses

    Science.gov (United States)

    Oreshkina, K. V.; Dubrovin, V. D.; Ignat'ev, A. I.; Nikonorov, N. V.

    2017-10-01

    The effect of silver on the optical, spectral-luminescent, and crystallization properties of bromide photo-thermo-refractive glasses is studied. Multicomponent photosensitive glasses of the Na2O-ZnO-Al2O3-SiO2 system with photosensitizing agents (cerium, antimony, silver) and halogenides (fluorine and bromine) are synthesized. Ultraviolet irradiation and thermal treatment below the glass-transition temperature of the glasses cause the formation of silver molecular clusters, which exhibit luminescence in the visible and infrared regions. UV irradiation and thermal treatment of glasses above the glass-transition temperature lead to the growth of silver nanoparticles with plasmon resonance peak in the region of 420 nm. Further thermal treatment of glasses above the glass-transition temperature shifts the plasmon-resonance maximum by 70 nm to longer wavelengths, which is related to the growth of a crystalline shell consisting of mixed silver and sodium bromides on nanoparticles. This formation of a crystalline phase on colloidal centers results in a local increase in the refractive index of the irradiated region by +Δ n 900 ppm compared to the nonirradiated region. Photo-thermo-refractive glasses with increased silver concentration are promising photosensitive materials for creating holographic optical elements and devices for line narrowing and stabilizing filters, spectral beam combiners, and filters for increasing the spectral brightness of laser diodes. A positive change in the refractive index of Photo-thermo-refractive glasses provides the possibility of recording in them 3D waveguide and integrated-optical structures.

  16. 1.28 Tbaud Nyquist Signal Transmission using Time-Domain Optical Fourier Transformation based Receiver

    DEFF Research Database (Denmark)

    Hu, Hao; Kong, Deming; Palushani, Evarist

    2013-01-01

    We demonstrate transmission of a 1.28-Tbaud Nyquist-OTDM signal over a record distance of 100 km with detection by time-domain optical Fourier transformation followed by FEC decoding, resulting in error-free performance for all tributaries....

  17. Non-invasive optical monitoring of the newborn piglet brain using continuous-wave and frequency-domain spectroscopy

    International Nuclear Information System (INIS)

    Fantini, S.; Franceschini, M.A.; Gratton, E.; Hueber, D.; Rosenfeld, W.; Maulik, D.; Stubblefield, P.G.; Stankovic, M.R.

    1999-01-01

    We have used continuous-wave (CW) and frequency-domain spectroscopy to investigate the optical properties of the newborn piglet brain in vivo and non-invasively. Three anaesthetized, intubated, ventilated and instrumented newborn piglets were placed into a stereotaxic instrument for optimal experimental stability, reproducible probe-to-scalp optical contact and 3D adjustment of the optical probe. By measuring the absolute values of the brain absorption and reduced scattering coefficients at two wavelengths (758 and 830 nm), frequency-domain spectroscopy provided absolute readings (in contrast to the relative readings of CW spectroscopy) of cerebral haemoglobin concentration and saturation during experimentally induced perturbations in cerebral haemodynamics and oxygenation. Such perturbations included a modulation of the inspired oxygen concentration, transient brain asphyxia, carotid artery occlusion and terminal brain asphyxia. The baseline cerebral haemoglobin saturation and concentration, measured with frequency-domain spectroscopy, were about 60% and 42 μM respectively. The cerebral saturation values ranged from a minimum of 17% (during transient brain asphyxia) to a maximum of 80% (during recovery from transient brain asphyxia). To analyse the CW optical data, we have (a) derived a mathematical relationship between the cerebral optical properties and the differential pathlength factor and (b) introduced a method based on the spatial dependence of the detected intensity (dc slope method). The analysis of the cerebral optical signals associated with the arterial pulse and with respiration demonstrates that motion artefacts can significantly affect the intensity recorded from a single optode pair. Motion artefacts can be strongly reduced by combining data from multiple optodes to provide relative readings in the dc slope method. We also report significant biphasic changes (initial decrease and successive increase) in the reduced scattering coefficient measured

  18. Specification of optical components using Wigner distribution function

    International Nuclear Information System (INIS)

    Xu Jiancheng; Li Haibo; Xu Qiao; Chai Liqun; Fan Changjiang

    2010-01-01

    In order to characterize and specify small-scale local wavefront deformation of optical component, a method based on Wigner distribution function has been proposed, which can describe wavefront deformation in spatial and spatial frequency domain. The relationship between Wigner distribution function and power spectral density is analyzed and thus the specification of small-scale local wavefront deformation is obtained by Wigner distribution function. Simulation and experiment demonstrate the effectiveness of the proposed method. The proposed method can not only identify whether the optical component meets the requirement of inertial confinement fusion (ICF), but also determine t he location where small-scale wavefront deformation is unqualified. Thus it provides an effective guide to the revision of unqualified optical components. (authors)

  19. Investigation of Wide-FSR SOI Optical Filters Operating in C and L Bands

    Directory of Open Access Journals (Sweden)

    V. M. N. Passaro

    2012-06-01

    Full Text Available In this paper we present the investigation of optical filters based on triple ring resonator architectures in silicon-on-insulator technology. The generalized approach based on Mason’s rule and delay line signal processing has been implemented for modeling optical filters in Z-domain. A numerical investigation based on the coefficient map has been adopted for designing optical add-drop multiplexers with wide free spectral ranges, as large as 12 THz (~ 96 nm. Low crosstalk, of the order of -20 dB, has been numerically demonstrated in overall transmittances of optimized filters.

  20. Vortex algebra by multiply cascaded four-wave mixing of femtosecond optical beams.

    Science.gov (United States)

    Hansinger, Peter; Maleshkov, Georgi; Garanovich, Ivan L; Skryabin, Dmitry V; Neshev, Dragomir N; Dreischuh, Alexander; Paulus, Gerhard G

    2014-05-05

    Experiments performed with different vortex pump beams show for the first time the algebra of the vortex topological charge cascade, that evolves in the process of nonlinear wave mixing of optical vortex beams in Kerr media due to competition of four-wave mixing with self-and cross-phase modulation. This leads to the coherent generation of complex singular beams within a spectral bandwidth larger than 200nm. Our experimental results are in good agreement with frequency-domain numerical calculations that describe the newly generated spectral satellites.

  1. NEW OPTICAL/ULTRAVIOLET COUNTERPARTS AND THE SPECTRAL ENERGY DISTRIBUTIONS OF NEARBY, THERMALLY EMITTING, ISOLATED NEUTRON STARS

    International Nuclear Information System (INIS)

    Kaplan, D. L.; Kamble, A.; Van Kerkwijk, M. H.; Ho, W. C. G.

    2011-01-01

    We present Hubble Space Telescope optical and ultraviolet photometry for five nearby, thermally emitting neutron stars. With these measurements, all seven such objects have confirmed optical and ultraviolet counterparts. Combining our data with archival space-based photometry, we present spectral energy distributions for all sources and measure the 'optical excess': the factor by which the measured photometry exceeds that extrapolated from X-ray spectra. We find that the majority have optical and ultraviolet fluxes that are inconsistent with that expected from thermal (Rayleigh-Jeans) emission, exhibiting more flux at longer wavelengths. We also find that most objects have optical excesses between 5 and 12, but that one object (RX J2143.0+0654) exceeds the X-ray extrapolation by a factor of more than 50 at 5000 A, and that this is robust to uncertainties in the X-ray spectra and absorption. We consider explanations for this ranging from atmospheric effects, magnetospheric emission, and resonant scattering, but find that none is satisfactory.

  2. Broadband Fourier domain mode-locked laser for optical coherence tomography at 1060 nm

    DEFF Research Database (Denmark)

    Marschall, Sebastian; Klein, Thomas; Wieser, Wolfgang

    2012-01-01

    Optical coherence tomography (OCT) in the 1060nm range is interesting for in vivo imaging of the human posterior eye segment (retina, choroid, sclera) due to low absorption in water and deep penetration into the tissue. Rapidly tunable light sources, such as Fourier domain mode-locked (FDML) lasers...

  3. Observation of magnetic domains using a reflection mode scanning near-field optical microscope

    NARCIS (Netherlands)

    Durkam, C.; Shvets, I.V.; Lodder, J.C.

    1997-01-01

    It is demonstrated that it is possible to image magnetic domains with a resolution of better than 60 nm with the Kerr effect in a reflection-mode scanning near-field optical microscope. Images taken of tracks of thermomagnetically prewritten bits in a Co/Pt multilayer structure magnetized out-of

  4. Structural changes of macula and optic disk of the fellow eye in patients with nonarteritic anterior ischemic optic neuropathy.

    Science.gov (United States)

    Duman, R; Yavas, G F; Veliyev, I; Dogan, M; Duman, R

    2018-05-10

    The aim was to assess the ganglion cell complex (GCC) thickness, retinal nerve fiber layer (RNFL) thickness and optic disk features in the affected eyes (AE) and unaffected fellow eyes (FE) of subjects with unilateral nonarteritic anterior ischemic optic neuropathy (NAION) and to compare with healthy control eyes (CE) using spectral domain-optical coherence tomography (SD-OCT). This study included 28 patients and age, sex and refraction-matched 28 control subjects. Mean GCC thickness and peripapillary RNFL thickness in four quadrants measured by cirrus SD-OCT were evaluated in both AE and FE of patients and CE. In addition, optic disk measurements obtained with OCT were evaluated. Mean GCC thickness was significantly lower in AE compared with both FE and CE (P optic disk cupping compared with both FE and CE (P optic disk features between the CE and FE. And significantly greater optic disk cupping in the AE compared with both FE and CE supports the acquired enlargement of cupping after the onset of NAION.

  5. Detecting and monitoring water stress states in maize crops using spectral ratios obtained in the photosynthetic domain

    Science.gov (United States)

    Baranoski, Gladimir V. G.; Van Leeuwen, Spencer R.

    2017-07-01

    The reliable detection and monitoring of changes in the water status of crops composed of plants like maize, a highly adaptable C4 species in large demand for both food and biofuel production, are longstanding remote sensing goals. Existing procedures employed to achieve these goals rely predominantly on the spectral signatures of plant leaves in the infrared domain where the light absorption within the foliar tissues is dominated by water. It has been suggested that such procedures could be implemented using subsurface reflectance to transmittance ratios obtained in the visible (photosynthetic) domain with the assistance of polarization devices. However, the experiments leading to this proposition were performed on detached maize leaves, which were not influenced by the whole (living) plant's adaptation mechanisms to water stress. In this work, we employ predictive simulations of light-leaf interactions in the photosynthetic domain to demonstrate that the living specimens' physiological responses to dehydration stress should be taken into account in this context. Our findings also indicate that a reflectance to transmittance ratio obtained in the photosynthetic domain at a lower angle of incidence without the use of polarization devices may represent a cost-effective alternative for the assessment of water stress states in maize crops.

  6. Measurement of retinal nerve fiber layer thickness in eyes with optic disc swelling by using scanning laser polarimetry and optical coherence tomography.

    Science.gov (United States)

    Hata, Masayuki; Miyamoto, Kazuaki; Oishi, Akio; Kimura, Yugo; Nakagawa, Satoko; Horii, Takahiro; Yoshimura, Nagahisa

    2014-01-01

    The retinal nerve fiber layer thickness (RNFLT) in patients with optic disc swelling of different etiologies was compared using scanning laser polarimetry (SLP) and spectral-domain optical coherence tomography (OCT). Forty-seven patients with optic disc swelling participated in the cross-sectional study. Both GDx SLP (enhanced corneal compensation) and Spectralis spectral-domain OCT measurements of RNFLT were made in 19 eyes with papilledema (PE), ten eyes with optic neuritis (ON), and 18 eyes with nonarteritic anterior ischemic optic neuropathy (NAION) at the neuro-ophthalmology clinic at Kyoto University Hospital. Differences in SLP (SLP-RNFLT) and OCT (OCT-RNFLT) measurements among different etiologies were investigated. No statistical differences in average OCT-RNFLT among PE, ON, and NAION patients were noted. Average SLP-RNFLT in NAION patients was smaller than in PE (P<0.01) or ON (P=0.02) patients. When RNFLT in each retinal quadrant was compared, no difference among etiologies was noted on OCT, but on SLP, the superior quadrant was thinner in NAION than in PE (P<0.001) or ON (P=0.001) patients. Compared with age-adjusted normative data of SLP-RNFLT, average SLP-RNFLT in PE (P<0.01) and ON (P<0.01) patients was greater. Superior SLP-RNFLT in NAION patients was smaller (P=0.026). The ratio of average SLP-RNFLT to average OCT-RNFLT was smaller in NAION than in PE (P=0.001) patients. In the setting of RNFL thickening, despite increased light retardance in PE and ON eyes, SLP revealed that NAION eyes have less retardance, possibly associated with ischemic axonal loss.

  7. Enhancement of accuracy in shape sensing of surgical needles using optical frequency domain reflectometry in optical fibers.

    Science.gov (United States)

    Parent, Francois; Loranger, Sebastien; Mandal, Koushik Kanti; Iezzi, Victor Lambin; Lapointe, Jerome; Boisvert, Jean-Sébastien; Baiad, Mohamed Diaa; Kadoury, Samuel; Kashyap, Raman

    2017-04-01

    We demonstrate a novel approach to enhance the precision of surgical needle shape tracking based on distributed strain sensing using optical frequency domain reflectometry (OFDR). The precision enhancement is provided by using optical fibers with high scattering properties. Shape tracking of surgical tools using strain sensing properties of optical fibers has seen increased attention in recent years. Most of the investigations made in this field use fiber Bragg gratings (FBG), which can be used as discrete or quasi-distributed strain sensors. By using a truly distributed sensing approach (OFDR), preliminary results show that the attainable accuracy is comparable to accuracies reported in the literature using FBG sensors for tracking applications (~1mm). We propose a technique that enhanced our accuracy by 47% using UV exposed fibers, which have higher light scattering compared to un-exposed standard single mode fibers. Improving the experimental setup will enhance the accuracy provided by shape tracking using OFDR and will contribute significantly to clinical applications.

  8. Opto-mechanical design of the MTG FCI spectral separation assembly

    Science.gov (United States)

    Riguet, François; Brousse, Emmanuel; Carel, Jean-Louis; Cottenye, Justine; Harmann, David; Joncour, Marc; Makhlouf, Houssine; Mouricaud, Daniel; Oussalah, Meihdi; Rodolfo, Jacques

    2015-09-01

    The Spectral Separation Assembly is a key component of the Flexible Combined Imager, an instrument that will be on-board Meteosat Third Generation. It splits the input beam coming from the telescope into five spectral groups, for a total of 16 channels, from 0.4 to 13.3 μm. It comprises a set of four dichroics separators followed by four collimating optics for the infrared spectral groups, which feed the cold imaging optics. The visible spectral group is directly imaged on a detector. This paper presents the optical design of the assembly, the mechanical mounting of the optical components, and the coatings developed for the dichroics, mirrors and lenses.

  9. The optical + infrared L dwarf spectral sequence of young planetary-mass objects in the Upper Scorpius association

    Science.gov (United States)

    Lodieu, N.; Zapatero Osorio, M. R.; Béjar, V. J. S.; Peña Ramírez, K.

    2018-01-01

    We present the results of photometric and spectroscopic follow-ups of the lowest mass member candidates in the nearest OB association, Upper Scorpius (∼5-10 Myr; 145 ± 17 pc), with the Gran Telescopio de Canarias (GTC) and European Southern Observatory (ESO) Very Large Telescope (VLT). We confirm the membership of the large majority (>80 per cent) of candidates originally selected photometrically and astrometrically based on their spectroscopic features, weak equivalent widths of gravity-sensitive doublets and radial velocities. Confirmed members follow a sequence over a wide magnitude range (J = 17.0-19.3 mag) in several colour-magnitude diagrams with optical, near- and mid-infrared photometry and have near-infrared spectral types in the L1-L7 interval with likely masses below 15 Jupiter masses. We find that optical spectral types tend to be earlier than near-infrared spectral types by a few subclasses for spectral types later than M9. We investigate the behaviour of spectral indices, defined in the literature as a function of spectral type and gravity, by comparison with values reported in the literature for young and old dwarfs. We also derive effective temperatures in the 1900-1600 K range from fits of synthetic model-atmosphere spectra to the observed photometry, but we caution that the procedure carries large uncertainties. We determine bolometric corrections for young L dwarfs with ages of ∼5-10 Myr (Upper Sco association) and find them to be similar in the J band but larger by 0.1-0.4 mag in the K band with respect to field L dwarfs. Finally, we discover two faint young L dwarfs, Visible and Infrared Survey Telescope for Astronomy (VISTA) J1607-2146 (L4.5) and VISTA J1611-2215 (L5), that have Hα emission and possible flux excesses at 4.5 μm, pointing to the presence of accretion from a disc on to the central objects of mass below ∼15MJup at an age of 5-10 Myr.

  10. Sensitivity study of heavy precipitation in Limited Area Model climate simulations: influence of the size of the domain and the use of the spectral nudging technique

    Science.gov (United States)

    Colin, Jeanne; Déqué, Michel; Radu, Raluca; Somot, Samuel

    2010-10-01

    We assess the impact of two sources of uncertainties in a limited area model (LAM) on the representation of intense precipitation: the size of the domain of integration and the use of the spectral nudging technique (driving of the large-scale within the domain of integration). We work in a perfect-model approach where the LAM is driven by a general circulation model (GCM) run at the same resolution and sharing the same physics and dynamics as the LAM. A set of three 50 km resolution simulations run over Western Europe with the LAM ALADIN-Climate and the GCM ARPEGE-Climate are performed to address this issue. Results are consistent with previous studies regarding the seasonal-mean fields. Furthermore, they show that neither the use of the spectral nudging nor the choice of a small domain are detrimental to the modelling of heavy precipitation in the present experiment.

  11. Convergent optical wired and wireless long-reach access network using high spectral-efficient modulation.

    Science.gov (United States)

    Chow, C W; Lin, Y H

    2012-04-09

    To provide broadband services in a single and low cost perform, the convergent optical wired and wireless access network is promising. Here, we propose and demonstrate a convergent optical wired and wireless long-reach access networks based on orthogonal wavelength division multiplexing (WDM). Both the baseband signal and the radio-over-fiber (ROF) signal are multiplexed and de-multiplexed in optical domain, hence it is simple and the operation speed is not limited by the electronic bottleneck caused by the digital signal processing (DSP). Error-free de-multiplexing and down-conversion can be achieved for all the signals after 60 km (long-reach) fiber transmission. The scalability of the system for higher bit-rate (60 GHz) is also simulated and discussed.

  12. Giant magneto-optical faraday effect in HgTe thin films in the terahertz spectral range.

    Science.gov (United States)

    Shuvaev, A M; Astakhov, G V; Pimenov, A; Brüne, C; Buhmann, H; Molenkamp, L W

    2011-03-11

    We report the observation of a giant Faraday effect, using terahertz (THz) spectroscopy on epitaxial HgTe thin films at room temperature. The effect is caused by the combination of the unique band structure and the very high electron mobility of HgTe. Our observations suggest that HgTe is a high-potential material for applications as optical isolator and modulator in the THz spectral range.

  13. Information-efficient spectral imaging sensor

    Science.gov (United States)

    Sweatt, William C.; Gentry, Stephen M.; Boye, Clinton A.; Grotbeck, Carter L.; Stallard, Brian R.; Descour, Michael R.

    2003-01-01

    A programmable optical filter for use in multispectral and hyperspectral imaging. The filter splits the light collected by an optical telescope into two channels for each of the pixels in a row in a scanned image, one channel to handle the positive elements of a spectral basis filter and one for the negative elements of the spectral basis filter. Each channel for each pixel disperses its light into n spectral bins, with the light in each bin being attenuated in accordance with the value of the associated positive or negative element of the spectral basis vector. The spectral basis vector is constructed so that its positive elements emphasize the presence of a target and its negative elements emphasize the presence of the constituents of the background of the imaged scene. The attenuated light in the channels is re-imaged onto separate detectors for each pixel and then the signals from the detectors are combined to give an indication of the presence or not of the target in each pixel of the scanned scene. This system provides for a very efficient optical determination of the presence of the target, as opposed to the very data intensive data manipulations that are required in conventional hyperspectral imaging systems.

  14. Optical CDMA with Embedded Spectral-Polarization Coding over Double Balanced Differential-Detector

    Science.gov (United States)

    Huang, Jen-Fa; Yen, Chih-Ta; Chen, Bo-Hau

    A spectral-polarization coding (SPC) optical code-division multiple-access (OCDMA) configuration structured over arrayed-waveguide grating (AWG) router is proposed. The polarization-division double balanced detector is adopted to execute difference detection and enhances system performance. The signal-to-noise ratio (SNR) is derived by taking the effect of PIIN into account. The result indicates that there would be up to 9-dB SNR improvement than the conventional spectral-amplitude coding (SAC) structures with Walsh-Hadamard codes. Mathematical deriving results of the SNR demonstrate the system embedded with the orthogonal state of polarization (SOP) will suppress effectively phase-induced intensity noise (PIIN). In addition, we will analyze the relations about bit error rate (BER) vs. the number of active users under the different encoding schemes and compare them with our proposed scheme. The BER vs. the effective power under the different encoding scheme with the same number of simultaneous active user conditions are also revealed. Finally, the polarization-matched factor and the difference between simulated and experimental values are discussed.

  15. Determining the von Mises stress power spectral density for frequency domain fatigue analysis including out-of-phase stress components

    Science.gov (United States)

    Bonte, M. H. A.; de Boer, A.; Liebregts, R.

    2007-04-01

    This paper provides a new formula to take into account phase differences in the determination of an equivalent von Mises stress power spectral density (PSD) from multiple random inputs. The obtained von Mises PSD can subsequently be used for fatigue analysis. The formula was derived for use in the commercial vehicle business and was implemented in combination with Finite Element software to predict and analyse fatigue failure in the frequency domain.

  16. 3D airborne EM modeling based on the spectral-element time-domain (SETD) method

    Science.gov (United States)

    Cao, X.; Yin, C.; Huang, X.; Liu, Y.; Zhang, B., Sr.; Cai, J.; Liu, L.

    2017-12-01

    In the field of 3D airborne electromagnetic (AEM) modeling, both finite-difference time-domain (FDTD) method and finite-element time-domain (FETD) method have limitations that FDTD method depends too much on the grids and time steps, while FETD requires large number of grids for complex structures. We propose a time-domain spectral-element (SETD) method based on GLL interpolation basis functions for spatial discretization and Backward Euler (BE) technique for time discretization. The spectral-element method is based on a weighted residual technique with polynomials as vector basis functions. It can contribute to an accurate result by increasing the order of polynomials and suppressing spurious solution. BE method is a stable tine discretization technique that has no limitation on time steps and can guarantee a higher accuracy during the iteration process. To minimize the non-zero number of sparse matrix and obtain a diagonal mass matrix, we apply the reduced order integral technique. A direct solver with its speed independent of the condition number is adopted for quickly solving the large-scale sparse linear equations system. To check the accuracy of our SETD algorithm, we compare our results with semi-analytical solutions for a three-layered earth model within the time lapse 10-6-10-2s for different physical meshes and SE orders. The results show that the relative errors for magnetic field B and magnetic induction are both around 3-5%. Further we calculate AEM responses for an AEM system over a 3D earth model in Figure 1. From numerical experiments for both 1D and 3D model, we draw the conclusions that: 1) SETD can deliver an accurate results for both dB/dt and B; 2) increasing SE order improves the modeling accuracy for early to middle time channels when the EM field diffuses fast so the high-order SE can model the detailed variation; 3) at very late time channels, increasing SE order has little improvement on modeling accuracy, but the time interval plays

  17. Spectral nudging to eliminate the effects of domain position and geometry in regional climate model simulations

    Science.gov (United States)

    Miguez-Macho, Gonzalo; Stenchikov, Georgiy L.; Robock, Alan

    2004-07-01

    It is well known that regional climate simulations are sensitive to the size and position of the domain chosen for calculations. Here we study the physical mechanisms of this sensitivity. We conducted simulations with the Regional Atmospheric Modeling System (RAMS) for June 2000 over North America at 50 km horizontal resolution using a 7500 km × 5400 km grid and NCEP/NCAR reanalysis as boundary conditions. The position of the domain was displaced in several directions, always maintaining the U.S. in the interior, out of the buffer zone along the lateral boundaries. Circulation biases developed a large scale structure, organized by the Rocky Mountains, resulting from a systematic shifting of the synoptic wave trains that crossed the domain. The distortion of the large-scale circulation was produced by interaction of the modeled flow with the lateral boundaries of the nested domain and varied when the position of the grid was altered. This changed the large-scale environment among the different simulations and translated into diverse conditions for the development of the mesoscale processes that produce most of precipitation for the Great Plains in the summer season. As a consequence, precipitation results varied, sometimes greatly, among the experiments with the different grid positions. To eliminate the dependence of results on the position of the domain, we used spectral nudging of waves longer than 2500 km above the boundary layer. Moisture was not nudged at any level. This constrained the synoptic scales to follow reanalysis while allowing the model to develop the small-scale dynamics responsible for the rainfall. Nudging of the large scales successfully eliminated the variation of precipitation results when the grid was moved. We suggest that this technique is necessary for all downscaling studies with regional models with domain sizes of a few thousand kilometers and larger embedded in global models.

  18. Inflammatory Papillitis in Uveitis: Response to Treatment and Use of Optic Nerve Optical Coherence Tomography for Monitoring.

    Science.gov (United States)

    Cho, Heeyoon; Pillai, Parvathy; Nicholson, Laura; Sobrin, Lucia

    2016-01-01

    To describe the clinical course of uveitis-associated inflammatory papillitis and evaluate the utility and reproducibility of optic nerve spectral domain optical coherence tomography (SD-OCT). Data on 22 eyes of 14 patients with uveitis-related papillitis and optic nerve imaging were reviewed. SD-OCT measure reproducibility was determined and parameters were compared in active vs. inactive uveitis. Papillitis resolution lagged behind uveitis resolution in three patients. For SD-OCT measures, the intraclass correlation coefficients were 99.1-100% and 86.9-100% for intraobserver and interobserver reproducibility, respectively. All SD-OCT optic nerve measures except inferior and nasal peripapillary retinal thicknesses were significantly higher in active vs. inactive uveitis after correction for multiple hypotheses testing. Mean optic nerve central thickness decreased from 545.1 to 362.9 µm (p = 0.01). Resolution of inflammatory papillitis can lag behind resolution of uveitis. SD-OCT assessment of papillitis is reproducible and correlates with presence vs. resolution of uveitis.

  19. Time-domain scanning optical mammography: II. Optical properties and tissue parameters of 87 carcinomas

    International Nuclear Information System (INIS)

    Grosenick, Dirk; Wabnitz, Heidrun; Moesta, K Thomas; Mucke, Joerg; Schlag, Peter M; Rinneberg, Herbert

    2005-01-01

    Within a clinical trial on scanning time-domain optical mammography reported on in a companion publication (part I), craniocaudal and mediolateral projection optical mammograms were recorded from 154 patients, suspected of having breast cancer. Here we report on in vivo optical properties of the subset of 87 histologically validated carcinomas which were visible in optical mammograms recorded at two or three near-infrared wavelengths. Tumour absorption and reduced scattering coefficients were derived from distributions of times of flight of photons recorded at the tumour site employing the model of diffraction of photon density waves by a spherical inhomogeneity, located in an otherwise homogeneous tissue slab. Effective tumour radii, taken from pathology, and tumour location along the compression direction, deduced from off-axis optical scans of the tumour region, were included in the analysis as prior knowledge, if available. On average, tumour absorption coefficients exceeded those of surrounding healthy breast tissue by a factor of about 2.5 (670 nm), whereas tumour reduced scattering coefficients were larger by about 20% (670 nm). From absorption coefficients at 670 nm and 785 nm total haemoglobin concentration and blood oxygen saturation were deduced for tumours and surrounding healthy breast tissue. Apart from a few outliers total haemoglobin concentration was observed to be systematically larger in tumours compared to healthy breast tissue. In contrast, blood oxygen saturation was found to be a poor discriminator for tumours and healthy breast tissue; both median values of blood oxygen saturation are the same within their statistical uncertainties. However, the ratio of total haemoglobin concentration over blood oxygen saturation further improves discrimination between tumours and healthy breast tissue. For 29 tumours detected in optical mammograms recorded at three wavelengths (670 nm, 785 nm, 843 nm or 884 nm), scatter power was derived from transport

  20. Retinal pigment epithelium findings in patients with albinism using wide-field polarization-sensitive optical coherence tomography.

    Science.gov (United States)

    Schütze, Christopher; Ritter, Markus; Blum, Robert; Zotter, Stefan; Baumann, Bernhard; Pircher, Michael; Hitzenberger, Christoph K; Schmidt-Erfurth, Ursula

    2014-11-01

    To investigate pigmentation characteristics of the retinal pigment epithelium (RPE) in patients with albinism using wide-field polarization-sensitive optical coherence tomography compared with intensity-based spectral domain optical coherence tomography and fundus autofluorescence imaging. Five patients (10 eyes) with previously genetically diagnosed albinism and 5 healthy control subjects (10 eyes) were imaged by a wide-field polarization-sensitive optical coherence tomography system (scan angle: 40 × 40° on the retina), sensitive to melanin contained in the RPE, based on the polarization state of backscattered light. Conventional intensity-based spectral domain optical coherence tomography and fundus autofluorescence examinations were performed. Retinal pigment epithelium-pigmentation was analyzed qualitatively and quantitatively based on depolarization assessed by polarization-sensitive optical coherence tomography. This study revealed strong evidence of polarization-sensitive optical coherence tomography to specifically image melanin in the RPE. Depolarization of light backscattered by the RPE in patients with albinism was reduced compared with normal subjects. Heterogeneous RPE-specific depolarization characteristics were observed in patients with albinism. Reduction of depolarization observed in the light backscattered by the RPE in patients with albinism corresponds to expected decrease of RPE pigmentation. The degree of depigmentation of the RPE is possibly associated with visual acuity. Findings suggest that different albinism genotypes result in heterogeneous levels of RPE pigmentation. Polarization-sensitive optical coherence tomography showed a heterogeneous appearance of RPE pigmentation in patients with albinism depending on different genotypes.

  1. Optic disc pit with sectorial retinitis pigmentosa.

    Science.gov (United States)

    Balikoglu-Yilmaz, Melike; Taskapili, Muhittin; Yilmaz, Tolga; Teke, Mehmet Yasin

    2013-01-01

    Sectorial retinitis pigmentosa (RP) and optic disc pit (ODP) are rare clinical conditions. We present a 40-year-old woman with a history of mild night blindness and decreased vision in the right eye for about 5 years. Fundus examination revealed retinal pigmentary changes in the superior and inferotemporal sectors covering the macula and reduced arterial calibre and ODP at the temporal edge of the optic disc. In addition, fundus autofluorescence, spectral-domain optical coherence tomography, fluorescein angiography, and multifocal electroretinogram scans confirmed these clinical findings. Visual acuity was decreased due to an atrophic-appearing foveal lesion. No intervention was suggested because of the poor visual potential. To the best of our knowledge, the present study is the first to describe coexistent optic disc pit and sectorial RP in the superior and inferotemporal sectors covering the macula in the same eye with figures.

  2. Fibre and components induced limitations in high capacity optical networks

    DEFF Research Database (Denmark)

    Peucheret, Christophe

    2003-01-01

    The design of future all-optical networks relies on the knowledge of the physical layer transport properties. In this thesis, we focus on two types of system impairments: those induced by the non-ideal transfer functions of optical filters to be found in network elements such as optical add...... design in order to maximise the spectral efficiency in a four add-drop node ring network. The concept of "normalised transmission sections" is introduced in order to ease the dimensioning of transparent domains in future all-optical networks. Normalised sections based on standard single mode fibre (SMF......-drop multiplexers (OADM) and optical cross-connects (OXC), as well as those due to the interaction of group-velocity dispersion, optical fibre non-linearities and accumulation of amplifier noise in the transmission path. The dispersion of fibre optics components is shown to limit their cascadability. Dispersion...

  3. Utilizing the ratio and the summation of two spectral lines for estimation of optical depth: Focus on thick plasmas

    Science.gov (United States)

    Rezaei, Fatemeh; Tavassoli, Seyed Hassan

    2016-11-01

    In this paper, a study is performed on the spectral lines of plasma radiations created from focusing of the Nd:YAG laser on Al standard alloys at atmospheric air pressure. A new theoretical method is presented to investigate the evolution of the optical depth of the plasma based on the radiative transfer equation, in LTE condition. This work relies on the Boltzmann distribution, lines broadening equations, and as well as the self-absorption relation. Then, an experimental set-up is devised to extract some of plasma parameters such as temperature from modified line ratio analysis, electron density from Stark broadening mechanism, line intensities of two spectral lines in the same order of ionization from similar species, and the plasma length from the shadowgraphy section. In this method, the summation and the ratio of two spectral lines are considered for evaluation of the temporal variations of the plasma parameters in a LIBS homogeneous plasma. The main advantage of this method is that it comprises the both of thin and thick laser induced plasmas without straight calculation of self-absorption coefficient. Moreover, the presented model can also be utilized for evaluation the transition of plasma from the thin condition to the thick one. The results illustrated that by measuring the line intensities of two spectral lines at different evolution times, the plasma cooling and the growth of the optical depth can be followed.

  4. Optical coherence tomography and optical coherence domain reflectometry for deep brain stimulation probe guidance

    Science.gov (United States)

    Jeon, Sung W.; Shure, Mark A.; Baker, Kenneth B.; Chahlavi, Ali; Hatoum, Nagi; Turbay, Massud; Rollins, Andrew M.; Rezai, Ali R.; Huang, David

    2005-04-01

    Deep Brain Stimulation (DBS) is FDA-approved for the treatment of Parkinson's disease and essential tremor. Currently, placement of DBS leads is guided through a combination of anatomical targeting and intraoperative microelectrode recordings. The physiological mapping process requires several hours, and each pass of the microelectrode into the brain increases the risk of hemorrhage. Optical Coherence Domain Reflectometry (OCDR) in combination with current methodologies could reduce surgical time and increase accuracy and safety by providing data on structures some distance ahead of the probe. For this preliminary study, we scanned a rat brain in vitro using polarization-insensitive Optical Coherence Tomography (OCT). For accurate measurement of intensity and attenuation, polarization effects arising from tissue birefringence are removed by polarization diversity detection. A fresh rat brain was sectioned along the coronal plane and immersed in a 5 mm cuvette with saline solution. OCT images from a 1294 nm light source showed depth profiles up to 2 mm. Light intensity and attenuation rate distinguished various tissue structures such as hippocampus, cortex, external capsule, internal capsule, and optic tract. Attenuation coefficient is determined by linear fitting of the single scattering regime in averaged A-scans where Beer"s law is applicable. Histology showed very good correlation with OCT images. From the preliminary study using OCT, we conclude that OCDR is a promising approach for guiding DBS probe placement.

  5. Tunable dual-wavelength filter and its group delay dispersion in domain-engineered lithium niobate

    Directory of Open Access Journals (Sweden)

    Guang-hao Shao

    2016-12-01

    Full Text Available A tunable dual-wavelength filter is experimentally demonstrated in domain-engineered lithium niobate. Application of an electric field on the y-surfaces of the sample results in the optical axes rotating clockwise and anticlockwise, which makes selective polarization rotation. The quasi phase-matching wavelengths could be adjusted through suitable domain design. A unique dual valley spectrum is obtained in a periodically poled lithium niobate structure with a central defect if the sample is placed between two parallel polarizers. The expected bandwidth could be varied from ∼1 nm to ∼40 nm. Moreover, both the spectral response and group delay dispersion could be engineered.

  6. Metallicity and the spectral energy distribution and spectral types of dwarf O-stars

    NARCIS (Netherlands)

    Mokiem, MR; Martin-Hernandez, NL; Lenorzer, A; de Koter, A; Tielens, AGGA

    We present a systematic study of the effect of metallicity on the stellar spectral energy distribution (SED) of 0 main sequence (dwarf) stars, focussing on the hydrogen and helium ionizing continua, and on the optical and near-IR lines used for spectral classification. The spectra are based on

  7. Metallicity and the spectral energy distribution and spectral types of dwarf O-stars

    NARCIS (Netherlands)

    Mokiem, M.R.; Martín-Hernández, N.L.; Lenorzer, A.; de Koter, A.; Tielens, A.G.G.M.

    2004-01-01

    We present a systematic study of the effect of metallicity on the stellar spectral energy distribution (SED) of O main sequence (dwarf) stars, focussing on the hydrogen and helium ionizing continua, and on the optical and near-IR lines used for spectral classification. The spectra are based on

  8. Observation of Lorentzian lineshapes in the room temperature optical spectra of strongly coupled Jaggregate/metal hybrid nanostructures by linear two-dimensional optical spectroscopy

    International Nuclear Information System (INIS)

    Wang, Wei; Sommer, Ephraim; De Sio, Antonietta; Gross, Petra; Vogelgesang, Ralf; Lienau, Christoph; Vasa, Parinda

    2014-01-01

    We analyze the linear optical reflectivity spectra of a prototypical, strongly coupled metal/molecular hybrid nanostructure by means of a new experimental approach, linear two-dimensional optical spectroscopy. White-light, broadband spectral interferometry is used to measure amplitude and spectral phase of the sample reflectivity or transmission with high precision and to reconstruct the time structure of the electric field emitted by the sample upon impulsive excitation. A numerical analysis of this time-domain signal provides a two-dimensional representation of the coherent optical response of the sample as a function of excitation and detection frequency. The approach is used to study a nanostructure formed by depositing a thin J-aggregated dye layer on a gold grating. In this structure, strong coupling between excitons and surface plasmon polaritons results in the formation of hybrid polariton modes. In the strong coupling regime, Lorentzian lineshape profiles of different polariton modes are observed at room temperature. This is taken as an indication that the investigated strongly coupled polariton excitations are predominantly homogeneously broadened at room temperature. This new approach presents a versatile, simple and highly precise addition to nonlinear optical spectroscopic techniques for the analysis of line broadening phenomena. (paper)

  9. THE TIME-DOMAIN SPECTROSCOPIC SURVEY: UNDERSTANDING THE OPTICALLY VARIABLE SKY WITH SEQUELS IN SDSS-III

    Energy Technology Data Exchange (ETDEWEB)

    Ruan, John J.; Anderson, Scott F.; Davenport, James R. A. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Green, Paul J.; Morganson, Eric [Harvard Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Eracleous, Michael; Brandt, William N. [Department of Astronomy and Astrophysics, 525 Davey Lab, The Pennsylvania State University, University Park, PA 16802 (United States); Myers, Adam D. [Department of Physics and Astronomy 3905, University of Wyoming, 1000 E. University, Laramie, WY 82071 (United States); Badenes, Carles [Department of Physics and Astronomy and Pittsburgh Particle Physics, Astrophysics, and Cosmology Center (PITT-PACC), University of Pittsburgh (United States); Bershady, Matthew A. [Department of Astronomy, University of Wisconsin-Madison, 475 N. Charter Street, Madison, WI 53706 (United States); Chambers, Kenneth C.; Flewelling, Heather; Kaiser, Nick [Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822 (United States); Dawson, Kyle S. [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States); Heckman, Timothy M. [Center for Astrophysical Sciences, Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Isler, Jedidah C. [Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235 (United States); Kneib, Jean-Paul [Laboratoire d’astrophysique, Ecole Polytechnique Fédérale de Lausanne Observatoire de Sauverny, 1290 Versoix (Switzerland); MacLeod, Chelsea L.; Ross, Nicholas P. [Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh, EH9 3HJ (United Kingdom); Paris, Isabelle, E-mail: jruan@astro.washington.edu [INAF—Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, I-34131 Trieste (Italy); and others

    2016-07-10

    The Time-Domain Spectroscopic Survey (TDSS) is an SDSS-IV eBOSS subproject primarily aimed at obtaining identification spectra of ∼220,000 optically variable objects systematically selected from SDSS/Pan-STARRS1 multi-epoch imaging. We present a preview of the science enabled by TDSS, based on TDSS spectra taken over ∼320 deg{sup 2} of sky as part of the SEQUELS survey in SDSS-III, which is in part a pilot survey for eBOSS in SDSS-IV. Using the 15,746 TDSS-selected single-epoch spectra of photometrically variable objects in SEQUELS, we determine the demographics of our variability-selected sample and investigate the unique spectral characteristics inherent in samples selected by variability. We show that variability-based selection of quasars complements color-based selection by selecting additional redder quasars and mitigates redshift biases to produce a smooth quasar redshift distribution over a wide range of redshifts. The resulting quasar sample contains systematically higher fractions of blazars and broad absorption line quasars than from color-selected samples. Similarly, we show that M dwarfs in the TDSS-selected stellar sample have systematically higher chromospheric active fractions than the underlying M-dwarf population based on their H α emission. TDSS also contains a large number of RR Lyrae and eclipsing binary stars with main-sequence colors, including a few composite-spectrum binaries. Finally, our visual inspection of TDSS spectra uncovers a significant number of peculiar spectra, and we highlight a few cases of these interesting objects. With a factor of ∼15 more spectra, the main TDSS survey in SDSS-IV will leverage the lessons learned from these early results for a variety of time-domain science applications.

  10. Analysis of dust and marine aerosol optical depth spectral-curvature information in the UV to SWIR (Short Wave Infrared) wavelength regions.

    Science.gov (United States)

    O'Neill, N. T.; Smirnov, A.; Eck, T. F.; Sakerin, S.; Kabanov, D.

    2005-12-01

    Traditional sunphotometry in the UV, visible and very NIR (Near Infrared) spectral regions is weighted, in terms of spectral information content, towards sub-micron (fine mode) particles. Sunphotometry in the NIR and SWIR increases the diversity and information content of spectral aerosol optical depth (AOD) measurements for supermicron (coarse mode) particles. Two data sets representing dust aerosols from the UAE (United Arab Emirates) region and marine aerosols from the northern, tropical and southern Atlantic Ocean were analyzed in terms of their spectral curvature diversity and information content. The former data set was acquired using NIR-enhanced CIMEL sunphotometers (340, 340, 380, 440, 500, 670, 870, 1020, 1640 nm) as part of the August to October, 2004 UAE2 field campaign while the latter data set was acquired using an automated Russian UV to SWIR SP-5 sunphotometer (339, 423, 438, 484, 552, 633, 677, 777, 869, 1241, 1560, 2148, 4000 nm) as part of a October/December 2004 cruise campaign in the northern, tropical and south Atlantic Ocean. A Microtops hand-held sunphotometer was also employed to acquire VIS to NIR AOD spectra during the latter field campaign. Results will be presented in terms of robust micro-physical and spectral curvature parameters which characterize super-micron aerosols and, in a more general sense, in terms of what universal/fundamental optical inferences can be drawn from the two disperse data sets.

  11. MODIS Aqua Optical Throughput Degradation Impact on Relative Spectral Response and Calibration on Ocean Color Products

    Science.gov (United States)

    Lee, Shihyan; Meister, Gerhard

    2017-01-01

    Since Moderate Resolution Imaging Spectroradiometer Aqua's launch in 2002, the radiometric system gains of the reflective solar bands have been degrading, indicating changes in the systems optical throughput. To estimate the optical throughput degradation, the electronic gain changes were estimated and removed from the measured system gain. The derived optical throughput degradation shows a rate that is much faster in the shorter wavelengths than the longer wavelengths. The wavelength-dependent optical throughput degradation modulated the relative spectral response (RSR) of the bands. In addition, the optical degradation is also scan angle-dependent due to large changes in response versus the scan angle over time. We estimated the modulated RSR as a function of time and scan angles and its impacts on sensor radiometric calibration for the ocean science. Our results show that the calibration bias could be up to 1.8 % for band 8 (412 nm) due to its larger out-of-band response. For the other ocean bands, the calibration biases are much smaller with magnitudes at least one order smaller.

  12. Optical coherence tomography findings of quinine poisoning

    Directory of Open Access Journals (Sweden)

    John Christoforidis

    2011-01-01

    Full Text Available John Christoforidis, Robert Ricketts, Theodore Loizos, Susie ChangThe Ohio State University College of Medicine, Columbus, OH, USAPurpose: To report a case of acute quinine poisoning, document acute and chronic macular changes with optical coherence tomography imaging and fluorescein angiography (FA, and to review the literature on ocular toxicity of quinine.Methods: A 32-year-old white female presented to our Emergency Department after ingesting over 7.5 g of quinine. She underwent a complete ophthalmologic examination, fluorescein angiography, Stratus time-domain optical coherence tomography (OCT, and electroretinography at 72 hours and 15 months postingestion. Stratus time-domain and Cirrus spectral-domain OCT, fundus autofluorescence, and FA were obtained at 28 months postingestion.Results: Fluorescein angiography at 72 hours postingestion revealed normal filling times and vasculature. OCT showed marked thickening of the inner retina bilaterally. At 15 and 28 months follow-up, fundus photography and fluorescein angiography demonstrated optic nerve pallor, severely attenuated retinal vessels while OCT showed inner retinal atrophy. Fundus autofluorescence did not reveal any retinal pigmentary abnormalities.Conclusions: Quinine toxicity as seen by OCT reveals increased thickness with inner retinal hyperreflectivity acutely with development of significant retinal atrophy in the long-term. Fundus autofluorescence reveals an intact retinal pigment epithelial layer at 28 months. These findings suggest that quinine poisoning may produce a direct toxic effect on the inner retina in the acute phase resulting in long-term retinal atrophy.Keywords: retinal, optical coherence tomography, quinine toxicity 

  13. XOP: A graphical user interface for spectral calculations and x-ray optics utilities

    International Nuclear Information System (INIS)

    Dejus, R.J.; Sanchez del Rio, M.

    1996-01-01

    A graphical user interface, using the Interactive Data Language (IDL) widget toolkit, for calculation of spectral properties of synchrotron radiation sources and for interaction of x-rays with optical elements has been developed. The interface runs presently on three different computer architectures under the Unix operating system endash the Sun-OS, the HP-UX, and the DEC-Unix operating systems. The point-and-click interface is used as a driver program for a variety of codes from different authors written in different computer languages. The execution of codes for calculating synchrotron radiation from undulators, wigglers, and bending magnets is summarized. The computation of optical properties of materials and the x-ray diffraction profiles from crystals in different geometries are also discussed. The interface largely simplifies the use of these codes and may be used without prior knowledge of how to run a particular program. copyright 1996 American Institute of Physics

  14. Broadband semiconductor optical amplifiers of the spectral range 750 – 1100 nm

    International Nuclear Information System (INIS)

    Andreeva, E V; Il'chenko, S N; Lobintsov, A A; Shramenko, M V; Ladugin, M A; Marmalyuk, A A; Yakubovich, S D

    2013-01-01

    A line of travelling-wave semiconductor optical amplifiers (SOAs) based on heterostructures used for production of broadband superluminescent diodes is developed. The pure small-signal gains of the developed SOA modules are about 25 dB, while the gain bandwidths at a level of –10 dB reach 50 – 100 nm. As a whole, the SOA modules cover the IR spectral range from 750 to 1100 nm. The SOAs demonstrate a high reliability at a single-mode fibre-coupled cw output power up to 50 mW. Examples of application of two of the developed SOA modules as active elements of broadband fast-tunable lasers are presented. (lasers)

  15. Broadband semiconductor optical amplifiers of the spectral range 750 – 1100 nm

    Energy Technology Data Exchange (ETDEWEB)

    Andreeva, E V; Il' chenko, S N; Lobintsov, A A; Shramenko, M V [Superlum Diodes Ltd., Moscow (Russian Federation); Ladugin, M A [' Sigm Plyus' Ltd, Moscow (Russian Federation); Marmalyuk, A A [Open Joint-Stock Company M.F. Stel' makh Polyus Research Institute, Moscow (Russian Federation); Yakubovich, S D [Moscow State Institute of Radio-Engineering, Electronics and Automation (Technical University), Moscow (Russian Federation)

    2013-11-30

    A line of travelling-wave semiconductor optical amplifiers (SOAs) based on heterostructures used for production of broadband superluminescent diodes is developed. The pure small-signal gains of the developed SOA modules are about 25 dB, while the gain bandwidths at a level of –10 dB reach 50 – 100 nm. As a whole, the SOA modules cover the IR spectral range from 750 to 1100 nm. The SOAs demonstrate a high reliability at a single-mode fibre-coupled cw output power up to 50 mW. Examples of application of two of the developed SOA modules as active elements of broadband fast-tunable lasers are presented. (lasers)

  16. Contributed Review: Absolute spectral radiance calibration of fiber-optic shock-temperature pyrometers using a coiled-coil irradiance standard lamp

    Energy Technology Data Exchange (ETDEWEB)

    Fat’yanov, O. V., E-mail: fatyan1@gps.caltech.edu; Asimow, P. D., E-mail: asimow@gps.caltech.edu [Division of Geological and Planetary Sciences 252-21, California Institute of Technology, Pasadena, California 91125 (United States)

    2015-10-15

    We describe an accurate and precise calibration procedure for multichannel optical pyrometers such as the 6-channel, 3-ns temporal resolution instrument used in the Caltech experimental geophysics laboratory. We begin with a review of calibration sources for shock temperatures in the 3000-30 000 K range. High-power, coiled tungsten halogen standards of spectral irradiance appear to be the only practical alternative to NIST-traceable tungsten ribbon lamps, which are no longer available with large enough calibrated area. However, non-uniform radiance complicates the use of such coiled lamps for reliable and reproducible calibration of pyrometers that employ imaging or relay optics. Careful analysis of documented methods of shock pyrometer calibration to coiled irradiance standard lamps shows that only one technique, not directly applicable in our case, is free of major radiometric errors. We provide a detailed description of the modified Caltech pyrometer instrument and a procedure for its absolute spectral radiance calibration, accurate to ±5%. We employ a designated central area of a 0.7× demagnified image of a coiled-coil tungsten halogen lamp filament, cross-calibrated against a NIST-traceable tungsten ribbon lamp. We give the results of the cross-calibration along with descriptions of the optical arrangement, data acquisition, and processing. We describe a procedure to characterize the difference between the static and dynamic response of amplified photodetectors, allowing time-dependent photodiode correction factors for spectral radiance histories from shock experiments. We validate correct operation of the modified Caltech pyrometer with actual shock temperature experiments on single-crystal NaCl and MgO and obtain very good agreement with the literature data for these substances. We conclude with a summary of the most essential requirements for error-free calibration of a fiber-optic shock-temperature pyrometer using a high-power coiled tungsten halogen

  17. method for ranging and noise reduction of low coherence interferometry LCI and optical coherence tomography OCT signals by parallel detection of spectral bands

    NARCIS (Netherlands)

    Boer, JF De; Tearney, G. J.; Bouma, BE

    2008-01-01

    Apparatus and method for increasing the sensitivity in the detection of optical coherence tomography and loW coher ence interferometry (“LCI”) signals by detecting a parallel set of spectral bands, each band being a unique combination of optical frequencies. The LCI broad bandwidth source is split

  18. Measurements and estimation of the columnar optical depth of tropospheric aerosols in the UV spectral region

    Directory of Open Access Journals (Sweden)

    V. E. Cachorro

    2002-04-01

    Full Text Available We report values of the columnar tropospheric aerosol optical depth at UV wavelengths based on experimental measurements of the direct spectral irradiances carried out by a commercial spectroradiometer (Li1800 of Licor company covering the range from 300–1100 nm at two stations with different climate characteristics in Spain. The first station is located in a rural site in north central Spain with continental climate. The data extend from March to the end of October of 1995. The other station is a coastal site in the Gulf of Cádiz (southwest Spain of maritime climate type. This study is mainly focused on the capability of estimating aerosol optical depth values in the UV region based on the extracted information in the visible and near infrared ranges. A first method has been used based on the Ångström turbidity parameters. However, since this method requires detailed spectral information, a second method has also been used, based on the correlation between wavelengths. A correlation has been established between the experimental aerosol optical depth values at 350 nm and 500 nm wavelengths. Although the type of aerosol seems to be the key factor that determines the quality of these estimations, the evaluation of the associated error is necessary to know the behaviour of these estimations in each area of study.Key words. Atmospheric composition and structure (aerosols and particles; transmission and scattering of radiation; troposphere – composition and chemistry

  19. Measurements and estimation of the columnar optical depth of tropospheric aerosols in the UV spectral region

    Directory of Open Access Journals (Sweden)

    V. E. Cachorro

    Full Text Available We report values of the columnar tropospheric aerosol optical depth at UV wavelengths based on experimental measurements of the direct spectral irradiances carried out by a commercial spectroradiometer (Li1800 of Licor company covering the range from 300–1100 nm at two stations with different climate characteristics in Spain. The first station is located in a rural site in north central Spain with continental climate. The data extend from March to the end of October of 1995. The other station is a coastal site in the Gulf of Cádiz (southwest Spain of maritime climate type. This study is mainly focused on the capability of estimating aerosol optical depth values in the UV region based on the extracted information in the visible and near infrared ranges. A first method has been used based on the Ångström turbidity parameters. However, since this method requires detailed spectral information, a second method has also been used, based on the correlation between wavelengths. A correlation has been established between the experimental aerosol optical depth values at 350 nm and 500 nm wavelengths. Although the type of aerosol seems to be the key factor that determines the quality of these estimations, the evaluation of the associated error is necessary to know the behaviour of these estimations in each area of study.

    Key words. Atmospheric composition and structure (aerosols and particles; transmission and scattering of radiation; troposphere – composition and chemistry

  20. Frequency domain Monte Carlo simulation method for cross power spectral density driven by periodically pulsed spallation neutron source using complex-valued weight Monte Carlo

    International Nuclear Information System (INIS)

    Yamamoto, Toshihiro

    2014-01-01

    Highlights: • The cross power spectral density in ADS has correlated and uncorrelated components. • A frequency domain Monte Carlo method to calculate the uncorrelated one is developed. • The method solves the Fourier transformed transport equation. • The method uses complex-valued weights to solve the equation. • The new method reproduces well the CPSDs calculated with time domain MC method. - Abstract: In an accelerator driven system (ADS), pulsed spallation neutrons are injected at a constant frequency. The cross power spectral density (CPSD), which can be used for monitoring the subcriticality of the ADS, is composed of the correlated and uncorrelated components. The uncorrelated component is described by a series of the Dirac delta functions that occur at the integer multiples of the pulse repetition frequency. In the present paper, a Monte Carlo method to solve the Fourier transformed neutron transport equation with a periodically pulsed neutron source term has been developed to obtain the CPSD in ADSs. Since the Fourier transformed flux is a complex-valued quantity, the Monte Carlo method introduces complex-valued weights to solve the Fourier transformed equation. The Monte Carlo algorithm used in this paper is similar to the one that was developed by the author of this paper to calculate the neutron noise caused by cross section perturbations. The newly-developed Monte Carlo algorithm is benchmarked to the conventional time domain Monte Carlo simulation technique. The CPSDs are obtained both with the newly-developed frequency domain Monte Carlo method and the conventional time domain Monte Carlo method for a one-dimensional infinite slab. The CPSDs obtained with the frequency domain Monte Carlo method agree well with those with the time domain method. The higher order mode effects on the CPSD in an ADS with a periodically pulsed neutron source are discussed