An All-Silicon Passive Optical Diode

OpenAIRE

Fan, Li; Wang, Jian; Varghese, Leo T.; Shen, Hao; Niu, Ben; Xuan, Yi; Weiner, Andrew M.; Qi, Minghao

2011-01-01

A passive optical diode effect would be useful for on-chip optical information processing but has been difficult to achieve. Using a method based on optical nonlinearity, we demonstrate a forward-backward transmission ratio of up to 28 decibels within telecommunication wavelengths. Our device, which uses two silicon rings 5 micrometers in radius, is passive yet maintains optical nonreciprocity for a broad range of input power levels, and it performs equally well even if the backward input pow...

An all-silicon passive optical diode.

Science.gov (United States)

Fan, Li; Wang, Jian; Varghese, Leo T; Shen, Hao; Niu, Ben; Xuan, Yi; Weiner, Andrew M; Qi, Minghao

2012-01-27

A passive optical diode effect would be useful for on-chip optical information processing but has been difficult to achieve. Using a method based on optical nonlinearity, we demonstrate a forward-backward transmission ratio of up to 28 decibels within telecommunication wavelengths. Our device, which uses two silicon rings 5 micrometers in radius, is passive yet maintains optical nonreciprocity for a broad range of input power levels, and it performs equally well even if the backward input power is higher than the forward input. The silicon optical diode is ultracompact and is compatible with current complementary metal-oxide semiconductor processing.

All optical OFDM transmission for passive optical networks

Science.gov (United States)

Kachare, Nitin; Ashik T., J.; Bai, K. Kalyani; Kumar, D. Sriram

2017-06-01

This paper demonstrates the idea of data transmission at a very higher rate (Tbits/s) through optical fibers in a passive optical network using the most efficient data transmission technique widely used in wireless communication that is orthogonal frequency division multiplexing. With an increase in internet users, data traffic has also increased significantly and the current dense wavelength division multiplexing (DWDM) systems may not support the next generation passive optical networks (PONs) requirements. The approach discussed in this paper allows to increase the downstream data rate per user and extend the standard single-mode fiber reach for future long-haul applications. All-optical OFDM is a promising solution for terabit per second capable single wavelength transmission, with high spectral efficiency and high tolerance to chromatic dispersion.

Examining the impact of overlying aerosols on the retrieval of cloud optical properties from passive remote sensing

Science.gov (United States)

Coddington, O. M.; Pilewskie, P.; Redemann, J.; Platnick, S.; Russell, P. B.; Schmidt, K. S.; Gore, W. J.; Livingston, J.; Wind, G.; Vukicevic, T.

2010-05-01

Haywood et al. (2004) show that an aerosol layer above a cloud can cause a bias in the retrieved cloud optical thickness and effective radius. Monitoring for this potential bias is difficult because space-based passive remote sensing cannot unambiguously detect or characterize aerosol above cloud. We show that cloud retrievals from aircraft measurements above cloud and below an overlying aerosol layer are a means to test this bias. The data were collected during the Intercontinental Chemical Transport Experiment (INTEX-A) study based out of Portsmouth, New Hampshire, United States, above extensive, marine stratus cloud banks affected by industrial outflow. Solar Spectral Flux Radiometer (SSFR) irradiance measurements taken along a lower level flight leg above cloud and below aerosol were unaffected by the overlying aerosol. Along upper level flight legs, the irradiance reflected from cloud top was transmitted through an aerosol layer. We compare SSFR cloud retrievals from below-aerosol legs to satellite retrievals from the Moderate Resolution Imaging Spectroradiometer (MODIS) in order to detect an aerosol-induced bias. In regions of small variation in cloud properties, we find that SSFR and MODIS-retrieved cloud optical thickness compares within the uncertainty range for each instrument while SSFR effective radius tend to be smaller than MODIS values (by 1-2 μm) and at the low end of MODIS uncertainty estimates. In regions of large variation in cloud properties, differences in SSFR and MODIS-retrieved cloud optical thickness and effective radius can reach values of 10 and 10 μm, respectively. We include aerosols in forward modeling to test the sensitivity of SSFR cloud retrievals to overlying aerosol layers. We find an overlying absorbing aerosol layer biases SSFR cloud retrievals to smaller effective radii and optical thickness while nonabsorbing aerosols had no impact.

Examining the Impact of Overlying Aerosols on the Retrieval of Cloud Optical Properties from Passive Remote Sensing

Science.gov (United States)

Coddington, O. M.; Pilewskie, P.; Redemann, J.; Platnick, S.; Russell, P. B.; Schmidt, K. S.; Gore, W. J.; Livingston, J.; Wind, G.; Vukicevic, T.

2010-01-01

Haywood et al. (2004) show that an aerosol layer above a cloud can cause a bias in the retrieved cloud optical thickness and effective radius. Monitoring for this potential bias is difficult because space ]based passive remote sensing cannot unambiguously detect or characterize aerosol above cloud. We show that cloud retrievals from aircraft measurements above cloud and below an overlying aerosol layer are a means to test this bias. The data were collected during the Intercontinental Chemical Transport Experiment (INTEX-A) study based out of Portsmouth, New Hampshire, United States, above extensive, marine stratus cloud banks affected by industrial outflow. Solar Spectral Flux Radiometer (SSFR) irradiance measurements taken along a lower level flight leg above cloud and below aerosol were unaffected by the overlying aerosol. Along upper level flight legs, the irradiance reflected from cloud top was transmitted through an aerosol layer. We compare SSFR cloud retrievals from below ]aerosol legs to satellite retrievals from the Moderate Resolution Imaging Spectroradiometer (MODIS) in order to detect an aerosol ]induced bias. In regions of small variation in cloud properties, we find that SSFR and MODIS-retrieved cloud optical thickness compares within the uncertainty range for each instrument while SSFR effective radius tend to be smaller than MODIS values (by 1-2 microns) and at the low end of MODIS uncertainty estimates. In regions of large variation in cloud properties, differences in SSFR and MODIS ]retrieved cloud optical thickness and effective radius can reach values of 10 and 10 microns, respectively. We include aerosols in forward modeling to test the sensitivity of SSFR cloud retrievals to overlying aerosol layers. We find an overlying absorbing aerosol layer biases SSFR cloud retrievals to smaller effective radii and optical thickness while nonabsorbing aerosols had no impact.

Advances in passive-remote and extractive Fourier transform infrared spectroscopic systems

International Nuclear Information System (INIS)

Demirgian, J.C.; Hammer, C.; Hwang, E.; Mao, Zhuoxiong.

1993-01-01

The Clean Air Act of 1990 requires the monitoring of air toxics including those from incinerator emissions. Continuous emission monitors (CEM) would demonstrate the safety of incinerators and address public concern about emissions of hazardous organic compounds. Fourier transform infrared (FTIR) spectroscopy can provide the technology for continuous emission monitoring of stacks. Stack effluent can be extracted and analyzed in less than one minute with conventional FTIR spectrometers. Passive-remote FTIR spectrometers can detect certain emission gases over 1 km away from a stack. The authors discuss advances in both extractive and passive-remote FTIR technology. Extractive systems are being tested with EPA protocols, which will soon replace periodic testing methods. Standard operating procedures for extractive systems are being developed and tested. Passive-remote FTIR spectrometers have the advantage of not requiring an extracted sample; however, they have less sensitivity. We have evaluated the ability of commercially available systems to detect fugitive plumes and to monitor carbon monoxide at a coal-fired power plant

Simulation and Evaluation of Ethernet Passive Optical Network

Directory of Open Access Journals (Sweden)

Salah A. Jaro Alabady

2013-05-01

Full Text Available      This paper studies simulation and evaluation of Ethernet Passive Optical Network (EPON system, IEEE802.3ah based OPTISM 3.6 simulation program. The simulation program is used in this paper to build a typical ethernet passive optical network, and to evaluate the network performance when using the (1580, 1625 nm wavelength instead of (1310, 1490 nm that used in Optical Line Terminal (OLT and Optical Network Units (ONU's in system architecture of Ethernet passive optical network at different bit rate and different fiber optic length. The results showed enhancement in network performance by increase the number of nodes (subscribers connected to the network, increase the transmission distance, reduces the received power and reduces the Bit Error Rate (BER.   

Predictive modeling of hazardous waste landfill total above-ground biomass using passive optical and LIDAR remotely sensed data

Science.gov (United States)

Hadley, Brian Christopher

This dissertation assessed remotely sensed data and geospatial modeling technique(s) to map the spatial distribution of total above-ground biomass present on the surface of the Savannah River National Laboratory's (SRNL) Mixed Waste Management Facility (MWMF) hazardous waste landfill. Ordinary least squares (OLS) regression, regression kriging, and tree-structured regression were employed to model the empirical relationship between in-situ measured Bahia (Paspalum notatum Flugge) and Centipede [Eremochloa ophiuroides (Munro) Hack.] grass biomass against an assortment of explanatory variables extracted from fine spatial resolution passive optical and LIDAR remotely sensed data. Explanatory variables included: (1) discrete channels of visible, near-infrared (NIR), and short-wave infrared (SWIR) reflectance, (2) spectral vegetation indices (SVI), (3) spectral mixture analysis (SMA) modeled fractions, (4) narrow-band derivative-based vegetation indices, and (5) LIDAR derived topographic variables (i.e. elevation, slope, and aspect). Results showed that a linear combination of the first- (1DZ_DGVI), second- (2DZ_DGVI), and third-derivative of green vegetation indices (3DZ_DGVI) calculated from hyperspectral data recorded over the 400--960 nm wavelengths of the electromagnetic spectrum explained the largest percentage of statistical variation (R2 = 0.5184) in the total above-ground biomass measurements. In general, the topographic variables did not correlate well with the MWMF biomass data, accounting for less than five percent of the statistical variation. It was concluded that tree-structured regression represented the optimum geospatial modeling technique due to a combination of model performance and efficiency/flexibility factors.

Optical Remote Sensing Laboratory

Data.gov (United States)

Federal Laboratory Consortium — The Optical Remote Sensing Laboratory deploys rugged, cutting-edge electro-optical instrumentation for the collection of various event signatures, with expertise in...

Assessment of Spacecraft Operational Status Using Electro-Optical Predictive Techniques

Science.gov (United States)

2010-09-01

panel appendages, may require enhanced preflight characterization processes to support monitoring by passive, remote, nonimaging optical sensors...observing and characterizing key spacecraft features. The simulation results are based on electro-optical signatures apparent to nonimaging sensors, along...and communication equipment, may require enhanced preflight characterization processes to support monitoring by passive, remote, nonimaging optical

Electronic band-gap modified passive silicon optical modulator at telecommunications wavelengths.

Science.gov (United States)

Zhang, Rui; Yu, Haohai; Zhang, Huaijin; Liu, Xiangdong; Lu, Qingming; Wang, Jiyang

2015-11-13

The silicon optical modulator is considered to be the workhorse of a revolution in communications. In recent years, the capabilities of externally driven active silicon optical modulators have dramatically improved. Self-driven passive modulators, especially passive silicon modulators, possess advantages in compactness, integration, low-cost, etc. Constrained by a large indirect band-gap and sensitivity-related loss, the passive silicon optical modulator is scarce and has been not advancing, especially at telecommunications wavelengths. Here, a passive silicon optical modulator is fabricated by introducing an impurity band in the electronic band-gap, and its nonlinear optics and applications in the telecommunications-wavelength lasers are investigated. The saturable absorption properties at the wavelength of 1.55 μm was measured and indicates that the sample is quite sensitive to light intensity and has negligible absorption loss. With a passive silicon modulator, pulsed lasers were constructed at wavelengths at 1.34 and 1.42 μm. It is concluded that the sensitive self-driven passive silicon optical modulator is a viable candidate for photonics applications out to 2.5 μm.

Modelisation et simulation d'un PON (Passive Optical Network) base ...

African Journals Online (AJOL)

English Title: Modeling and simulation of a PON (Passive Optical Network) Based on hybrid technology WDM/TDM. English Abstract. This development is part of dynamism of design for a model combining WDM and TDM multiplexing in the optical network of PON (Passive Optical Network) type, in order to satisfy the high bit ...

Experimental integration of quantum key distribution and gigabit-capable passive optical network

Science.gov (United States)

Sun, Wei; Wang, Liu-Jun; Sun, Xiang-Xiang; Mao, Yingqiu; Yin, Hua-Lei; Wang, Bi-Xiao; Chen, Teng-Yun; Pan, Jian-Wei

2018-01-01

Quantum key distribution (QKD) ensures information-theoretic security for the distribution of random bits between two remote parties. To extend QKD applications to fiber-to-the-home optical communications, such as gigabit-capable passive optical networks (GPONs), an effective method is the use of wavelength-division multiplexing. However, the Raman scattering noise from intensive classical traffic and the huge loss introduced by the beam splitter in a GPON severely limits the performance of QKD. Here, we demonstrate the integration of QKD and a commercial GPON system with fiber lengths up to 14 km, in which the maximum splitting ratio of the beam splitter reaches 1:64. By placing the QKD transmitter on the optical line terminal side, we reduce the Raman noise collected at the QKD receiver. Using a bypass structure, the loss of the beam splitter is circumvented effectively. Our results pave the way to extending the applications of QKD to last-mile communications.

Coherent detection passive optical access network enabling converged delivery of broadcast and dedicated broadband services

DEFF Research Database (Denmark)

Osadchiy, Alexey Vladimirovich; Prince, Kamau; Guerrero Gonzalez, Neil

2011-01-01

We propose a passive optical network architecture based on coherent detection for converged delivery of broadcast services from a dedicated remote broadcast server and user-specific services from a local central office. We experimentally demonstrate this architecture with mixed traffic types....... The broadcast channels were transmitted over 78 km of single mode fiber to a central office where they were multiplexed with the unicast channels for further fiber transmission over 34-km to reach the access network. Successful detection of all channels is demonstrated....

Optical/Infrared Signatures for Space-Based Remote Sensing

National Research Council Canada - National Science Library

Picard, R. H; Dewan, E. M; Winick, J. R; O'Neil, R. R

2007-01-01

This report describes work carried out under the Air Force Research Laboratory's basic research task in optical remote-sensing signatures, entitled Optical / Infrared Signatures for Space-Based Remote Sensing...

Passive New UV Polarimeter for Remote Surface and Atmospheric Sensing, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — Our imaging polarimeter concept makes available for the first time, the passive remote imagery of all four Stokes vector components at UV wavelengths shorter than...

Remote PECVD silicon nitride films with improved electrical properties for GaAs P-HEMT passivation

CERN Document Server

Sohn, M K; Kim, K H; Yang, S G; Seo, K S

1998-01-01

In order to obtain thin silicon nitride films with excellent electrical and mechanical properties, we employed RPECVD (Remote Plasma Enhanced Chemical Vapor Deposition) process which produces less plasma-induced damage than the conventional PECVD. Through the optical and electrical measurements of the deposited films, we optimized the various RPECVD process parameters. The optimized silicon nitride films showed excellent characteristics such as small etch rate (approx 33 A/min by 7:1 BHF), high breakdown field (>9 MV/cm), and low compressive stress (approx 3.3x10 sup 9 dyne/cm sup 2). We successfully applied thin RPECVD silicon nitride films to the surface passivation of GaAs pseudomorphic high electron mobility transistors (P-HEMTs) with negligible degradations in DC and RF characteristics.

Traffic Scheduling in WDM Passive Optical Network with Delay Guarantee

Institute of Scientific and Technical Information of China (English)

无

2005-01-01

WDM passive optical network becomes more favorable as the required bandwidth increases, but currently few media access control algorithms adapted to WDM access network. This paper presented a new scheduling algorithm for bandwidth sharing in WDM passive optical networks, which provides per-flow delay guarantee and supports variable-length packets scheduling. Through theoretical analysis and simulation, the end-to-end delay bound and throughput fairness of the algorithm was demonstrated.

Results from the July 1981 Workshop on Passive Remote Sensing of the Troposphere

International Nuclear Information System (INIS)

Keafer, L.S. Jr.; Reichle, H.G. Jr.

1982-01-01

Potential roles of passive remote sensors in the study of the chemistry and related dynamics of the lower atmosphere were defined by a Tropospheric Passive Remote Sensing Workshop, and technology advances required to implement these roles were identified. A promising role is in making global-scale, multilayer measurements of the more abundant trace tropospheric gaseous species (e.g., O 3 , CO, CH 4 , HNO 3 ) and of aerosol thickness and size distribution. It includes both nadirand limb-viewing measurements. Technology advances focus on both scanning- and fixed-spectra, nadir-viewing techniques with resolutions of 0.1 kaysers or better. Balloon- and Shuttle-borne experiments should be performed to study the effects of instrument noise and background fluctuations on data inversion and to determine the utility of simultaneously obtained nadir- and limb-viewing data

Active Ground Optical Remote Sensing for Improved Monitoring of Seedling Stress in Nurseries

Directory of Open Access Journals (Sweden)

Jan U. H. Eitel

2010-03-01

Full Text Available Active ground optical remote sensing (AGORS devices mounted on overhead irrigation booms could help to improve seedling quality by autonomously monitoring seedling stress. In contrast to traditionally used passive optical sensors, AGORS devices operate independently of ambient light conditions and do not require spectral reference readings. Besides measuring red (590–670 nm and near-infrared (>760 nm reflectance AGORS devices have recently become available that also measure red-edge (730 nm reflectance. We tested the hypothesis that the additional availability of red-edge reflectance information would improve AGORS of plant stress induced chlorophyll breakdown in Scots pine (Pinus sylvestris. Our results showed that the availability of red-edge reflectance information improved AGORS estimates of stress induced variation in chlorophyll concentration (r2 > 0.73, RMSE < 1.69 when compared to those without (r2 = 0.57, RMSE = 2.11.

Protection of Passive Optical Networks by Using Ring Topology and Tunable Splitters

Directory of Open Access Journals (Sweden)

Pavel Lafata

2013-01-01

Full Text Available This article proposes an innovative method for protecting of passive optical networks (PONs, especially the central optical unit – optical line termination (OLT. PON networks are typically used in modern high-speed access networks, but there are also several specific applications, such as in business, army or science sector, which require a complex protection and backup system against failures and malfunctions. A standard tree or star topologies, which are usually used for PON networks, are significantly vulnerable mainly against the malfunctions and failures of OLT unit or feeder optical cable. The method proposed in this paper is focused on forming PON network with ring topology using passive optical splitters. The main idea is based on the possibility of placing both OLT units (primary and secondary on the opposite sides of the ring, which can potentially increase the resistance of network. This method is described in the article and scenarios and calculations using symmetric or tunable asymmetric passive optical splitters are included as well.

Optical registration of spaceborne low light remote sensing camera

Science.gov (United States)

Li, Chong-yang; Hao, Yan-hui; Xu, Peng-mei; Wang, Dong-jie; Ma, Li-na; Zhao, Ying-long

2018-02-01

For the high precision requirement of spaceborne low light remote sensing camera optical registration, optical registration of dual channel for CCD and EMCCD is achieved by the high magnification optical registration system. System integration optical registration and accuracy of optical registration scheme for spaceborne low light remote sensing camera with short focal depth and wide field of view is proposed in this paper. It also includes analysis of parallel misalignment of CCD and accuracy of optical registration. Actual registration results show that imaging clearly, MTF and accuracy of optical registration meet requirements, it provide important guarantee to get high quality image data in orbit.

Modelling of passive heating for replication of sub-micron patterns in optical disk substrates

Energy Technology Data Exchange (ETDEWEB)

Kim, Youngmin; Bae, Jaecheol; Kim, Hongmin; Kang, Shinill [School of Mechanical Engineering, Yonsei University, 134 Shinchon-dong, Seodaemoon-ku, Seoul (Korea, Republic of)

2004-05-07

The transcribability of pit or land groove structures in replicating an optical disk substrate greatly affects the performance of a high-density optical disk. However, a solidified layer generated during the polymer filling worsens transcribability because the solidified layer prevents the polymer melt from filling the sub-micron patterns. Therefore, the development of the solidified layer during the filling stage of injection moulding must be delayed. For this delay, passive heating through an insulation layer has been used. In the present study, to examine the development of the solidified layer, delayed by passive heating, the flow of the polymer melt with passive heating was analysed. Passive heating delayed markedly the development of the solidified layer, reduced the viscosity of the polymer melt, and increased the fluidity of the polymer melt in the vicinity of the stamper surface with the sub-micron patterns. As a result, we predict that passive heating can improve the transcribability of an optical disk substrate. To verify our prediction, we fabricated an optical disk substrate by using passive heating of a mould and measured the transcribability of an optical disk substrate.

Modelling of passive heating for replication of sub-micron patterns in optical disk substrates

International Nuclear Information System (INIS)

Kim, Youngmin; Bae, Jaecheol; Kim, Hongmin; Kang, Shinill

2004-01-01

The transcribability of pit or land groove structures in replicating an optical disk substrate greatly affects the performance of a high-density optical disk. However, a solidified layer generated during the polymer filling worsens transcribability because the solidified layer prevents the polymer melt from filling the sub-micron patterns. Therefore, the development of the solidified layer during the filling stage of injection moulding must be delayed. For this delay, passive heating through an insulation layer has been used. In the present study, to examine the development of the solidified layer, delayed by passive heating, the flow of the polymer melt with passive heating was analysed. Passive heating delayed markedly the development of the solidified layer, reduced the viscosity of the polymer melt, and increased the fluidity of the polymer melt in the vicinity of the stamper surface with the sub-micron patterns. As a result, we predict that passive heating can improve the transcribability of an optical disk substrate. To verify our prediction, we fabricated an optical disk substrate by using passive heating of a mould and measured the transcribability of an optical disk substrate

Remote optical stethoscope and optomyography sensing device

Science.gov (United States)

Golberg, Mark; Polani, Sagi; Ozana, Nisan; Beiderman, Yevgeny; Garcia, Javier; Ruiz-Rivas Onses, Joaquin; Sanz Sabater, Martin; Shatsky, Max; Zalevsky, Zeev

2017-02-01

In this paper we present the usage of photonic remote laser based device for sensing nano-vibrations for detection of muscle contraction and fatigue, eye movements and in-vivo estimation of glucose concentration. The same concept is also used to realize a remote optical stethoscope. The advantage of doing the measurements from a distance is in preventing passage of infections as in the case of optical stethoscope or in the capability to monitor e.g. sleep quality without disturbing the patient. The remote monitoring of glucose concentration in the blood stream and the capability to perform opto-myography for the Messer muscles (chewing) is very useful for nutrition and weight control. The optical configuration for sensing the nano-vibrations is based upon analyzing the statistics of the secondary speckle patterns reflected from various tissues along the body of the subjects. Experimental results present the preliminary capability of the proposed configuration for the above mentioned applications.

Green Functions For Multiple Scattering As Mathematical Tools For Dense Cloud Remote Sensing: Theory, With Passive And Active Applications

International Nuclear Information System (INIS)

Davis, A.B.; Marshak, A.; Cahalan, R.F.

2001-01-01

We survey radiative Green function theory (1) in linear transport theory where numerical procedures are required to obtain specific results and (2) in the photon diffusion limit (large optical depths) where it is analytically tractable, at least for homogeneous plane-parallel media. We then describe two recent applications of Green function theory to passive cloud remote sensing in the presence of strong three-dimensional transport effects. Finally, we describe recent instrumental breakthroughs in 'off-beam' cloud lidar which is based on direct measurements of radiative Green functions with special attention to the data collected during the Shuttle-based Lidar In-space Technology Experiment (LITE) mission.

A STUDY OF SOLID STATE LASER PASSIVE OPTICAL Q-SWITCHING OPERATION REGIME (Part 1

Directory of Open Access Journals (Sweden)

Ion LĂNCRĂNJAN

2009-09-01

Full Text Available This paper is the first of a four series treating, theoretically with experimental comparison, the issue of solid state laser passive optical Q-switching regime. In this first paper the technique of solid state lasers passive optical Q-switching is numerically investigated considering the case of longitudinally and transversally uniform photon, population inversion and absorption centres densities. The coupled differential equations defining photon, population inversion and absorption centres densities are numerically solved being the basis of passively optical Q-switched laser functional simulation. The numerical simulations are performed using the several software packages, mostly SCILAB programs. The developed SCILAB programs can be used for a large range of saturable absorption centre and active media parameters, mainly the initial (low signal optical transmittance of the passive optical Q-switch. The developed FORTRAN and SCILAB programs can be applied for passively Q-switched solid state lasers of several types emitting at several NIR wavelengths, in domain 1 ÷ 2 μm. For validating the numerical simulation results are compared with The results of the numerical simulation are compared with experimentally obtained ones, in the case of a LiF:F2- passively Q-switched Nd:YAG. A good agreement between the two kinds of results is observed.

Optical and impedance characteristics of passive films on pure aluminium

International Nuclear Information System (INIS)

Krishnakumar, R.; Szklarska-Smialowska, Z.

1992-01-01

Optical and Impedance behavior of pure bulk aluminum and pure sputtered aluminum film were studied in order to gain a better understanding of their fundamental passivation and pitting characteristics. Constant potential experiments at the passivation and pitting potentials, and potentiostatic anodic polarization were conducted while simultaneously monitoring the current, impedance and optical behavior, in-situ. Noise characteristics in the current data during the pit incubation period indicate that Cl - ions migrate with little impediment to the metal surface through defects in the passive film. Impedance experiments indicate that the polarization resistance fluctuates continuously with time during the pit incubation period, suggesting that impedance spectroscopy is sensitive to localized processes. The interfacial capacitance increases continuously during this time. The smallest pits observed on the sample surface (less than 10μ) are clearly crystallographic, indicating activation controlled dissolution at pits. The film capacitance increases with exposure time at the passivation potential, while the polarization resistance decreases continuously. The decrease in the film resistance is thought to be due to chloride incorporation at defects in the passive film. The increase in film capacitance at the passivation and pitting potential is due to an increase in the film dielectric constant caused by either a compositional change or anion incorporation. Ellipsometry results indicate growth of a dual layered film on the pure aluminum surface, with the outer layer probably containing varying amounts of incorporated chloride depending on the applied potential. Preliminary experiments indicate that in the case of sputtered aluminum film, the passive film resistance is at least an order of magnitude higher than that of bulk aluminum. This is due to the fine grain structure of sputtered Al and hence a more defect free passive film than that formed on bulk aluminum. There is

Design issues for semi-passive optical communication devices

Science.gov (United States)

Glaser, I.

2007-09-01

Optical smart cards are devices containing a retro-reflector, light modulator, and some computing and data storage capabilities to affect semi-passive communication. They do not produce light; instead they modulate and send back light received from a stationary unit. These devices can replace contact-based smart cards as well as RF based ones for applications ranging from identification to transmitting and validating data. Since their transmission is essentially focused on the receiving unit, they are harder to eavesdrop than RF devices, yet need no physical contact or alignment. In this paper we explore optical design issues of these devices and estimate their optical behavior. Specifically, we analyze how these compact devices can be optimized for selected application profiles. Some of the key parameters addressed are effective light efficiency (how much modulated signal can be received by the stationary unit given the amount of light it transmits), range of tilt angles (angle between device surface normal to the line connecting the optical smart card with the stationary unit) through which the device would be effective, and power requirements of the semi-passive unit. In addition, issues concerning compact packaging of this device are discussed. Finally, results of the analysis are employed to produce a comparison of achievable capabilities of these optical smart cards, as opposed to alternative devices, and discuss potential applications were they can be best utilized.

Reactive granular optics for passive tracking of the sun

Science.gov (United States)

Frenkel, I.; Niv, A.

2017-08-01

The growing need for cost-effective renewable energy sources is hampered by the stagnation in solar cell technology, thus preventing a substantial reduction in the module and energy-production price. Lowering the energy-production cost could be achieved by using modules with efficiency. One of the possible means for increasing the module efficiency is concentrated photovoltaics (CPV). CPV, however, requires complex and accurate active tracking of the sun that reduces much of its cost-effectiveness. Here, we propose a passive tracking scheme based on a reactive optical device. The optical reaction is achieved by a new kind of light activated mechanical force that acts on micron-sized particles. This optical force allows the formation of granular disordered optical media that can be switched from being opaque to become transparent based on the intensity of light it interacts with. Such media gives rise to an efficient passive tracking scheme that when combined with an external optical cavity forms a new solar power conversion approach. Being external to the cell itself, this approach is indifferent to the type of semiconducting material that is used, as well as to other aspects of the cell design. This, in turn, liberates the cell layout from its optical constraints thus paving the way to higher efficiencies at lower module price.

Fiber-optic-coupled dosemeter for remote optical sensing of radiation

International Nuclear Information System (INIS)

Justus, B.L.; Huston, A.L.

1996-01-01

Remote sensing technologies for the detection and measurement of ionizing radiation exposure are of current interest for applications such as patient dose verification during radiotherapy and the monitoring of environmental contaminants. Fiberoptic-based sensing is attractive due to the advantages of small size, low cost, long life and freedom from electromagnetic interference. Several fiberoptic-based radiation sensing systems have been described that utilize radiation induced changes in the optical characteristics of the fiber such as reduced transmission as a result of darkening of the glass, optical phase shifts due to heating, or changes in the birefringence of a polarization-maintaining fiber. The measurement of radiation induced darkening is limited in both sensitivity and dynamic range and requires long fiber lengths. Phase shift measurements require the use of single-mode lasers, phase sensitive interferometric detection, long fiber lengths and complex signal processing techniques. Alternatively, thermoluminescent (TL) phosphor powders have been coated onto fiberoptic cables and remote dosimetry measurements performed using traditional laser heating techniques. The sensitivity is limited by the requirement for a very thin layer of phosphor material, due to problems associated with light scattering and efficient heating by thermal diffusion. In this paper we report the development of an all-optical, fiber-optic-coupled, thermoluminescence dosemeter for remote radiation sensing that offers significant advantages compared to previous technologies. We recently reported the development of an optically transparent, TL glass material having exceptionally good characteristics for traditional dosimetry applications. We also reported a modified TL glass incorporating a rare earth ion dopant in order to absorb light from a semiconductor laser and utilize the absorbed light energy to internally heat the glass and release the trapped electrons. (author)

Integrated Active and Passive Polymer Optical Components with nm to mm Features

DEFF Research Database (Denmark)

Christiansen, Mads Brøkner; Schøler, Mikkel; Kristensen, Anders

2007-01-01

We present wafer-scale fabrication of integrated active and passive polymer optics with nm to mm features. First order DFB lasers, defined in dye doped SU-8 resist are integrated with SU-8 waveguides.......We present wafer-scale fabrication of integrated active and passive polymer optics with nm to mm features. First order DFB lasers, defined in dye doped SU-8 resist are integrated with SU-8 waveguides....

Passive unmanned sky spectroscopy for remote bird classification

Science.gov (United States)

Lundin, Patrik; Brydegaard, Mikkel; Cocola, Lorenzo; Runemark, Anna; Åkesson, Susanne; Svanberg, Sune

2011-11-01

We present a method based on passive spectroscopy with aim to remotely study flying birds. A compact spectrometer is continuously recording spectra of a small section of the sky, waiting for birds to obscure part of the field-of-view when they pass the field in flight. In such situations the total light intensity received through the telescope, looking straight up, will change very rapidly as compared to the otherwise slowly varying sky light. On passage of a bird, both the total intensity and the spectral shape of the captured light changes notably. A camera aimed in the same direction as the telescope, although with a wider field-of-view, is triggered by the sudden intensity changes in the spectrometer to record additional information, which may be used for studies of migration and orientation. Example results from a trial are presented and discussed. The study is meant to explore the information that could be gathered and extracted with the help of a spectrometer connected to a telescope. Information regarding the color, size and height of flying birds is discussed. Specifically, an application for passive distance determination utilizing the atmospheric oxygen A-band absorption at around 760 nm is discussed.

Effects of the Ionosphere on Passive Microwave Remote Sensing of Ocean Salinity from Space

Science.gov (United States)

LeVine, D. M.; Abaham, Saji; Hildebrand, Peter H. (Technical Monitor)

2001-01-01

Among the remote sensing applications currently being considered from space is the measurement of sea surface salinity. The salinity of the open ocean is important for understanding ocean circulation and for modeling energy exchange with the atmosphere. Passive microwave remote sensors operating near 1.4 GHz (L-band) could provide data needed to fill the gap in current coverage and to complement in situ arrays being planned to provide subsurface profiles in the future. However, the dynamic range of the salinity signal in the open ocean is relatively small and propagation effects along the path from surface to sensor must be taken into account. In particular, Faraday rotation and even attenuation/emission in the ionosphere can be important sources of error. The purpose or this work is to estimate the magnitude of these effects in the context of a future remote sensing system in space to measure salinity in L-band. Data will be presented as a function of time location and solar activity using IRI-95 to model the ionosphere. The ionosphere presents two potential sources of error for the measurement of salinity: Rotation of the polarization vector (Faraday rotation) and attenuation/emission. Estimates of the effect of these two phenomena on passive remote sensing over the oceans at L-band (1.4 GHz) are presented.

Passive Optical Link Budget for LEO Space Surveillance

Science.gov (United States)

Wagner, P.; Hasenohr, T.; Hampf, D.; Sproll, F.; Humbert, L.; Rodmann, J.; Riede, W.

The rising space debris population is becoming an increasing risk for space assets. Even objects with the size of 10mm can cause major damages to active spacecraft. Especially the orbits around 800km high are densely populated with space debris objects. To assess the risk of collisions with active satellites, the Earth orbits need to be surveyed permanently. Space debris laser ranging systems for example can deliver highly accurate positional data for precise orbit determination. Therefor a priori information about the objects coarse trajectory is needed. Such initial orbit information can be provided by wide angle optical sensors. The Institute of Technical Physics at the German Aerospace Center in Stuttgart runs an observatory to perform passive as well as laser optical measurements to LEO objects. In order to detect unknown objects, a wide-angle imaging system with a field of view in the range of 5° to 15° equipped with an astronomical CCD camera and a commercial off the shelf (COTS) lens was designed to continuously observe the night sky for LEO objects. This paper presents the passive optical link budget for observing LEO objects to show the benefits and limits of the physical performance of an optical surveillance system. A compact COTS system is able to detect objects with a couple of decimeters in size while a large aperture telescope can detect objects with diameters below 10cm. Additionally, data captured by a passive optical staring system with a 10 cm aperture was analyzed. It is shown that 90% of all objects with a radar cross section larger than 2m² are detected with such a system during twilight conditions. The smallest detected LEO object with this system has a size of 0.32m x 0.32m x 0.26m. These measurements are compared to the developed link budget which allows an estimation of the performance of larger systems.

Use of passive microwave remote sensing to monitor soil moisture

International Nuclear Information System (INIS)

Wigneron, J.P.; Schmugge, T.; Chanzy, A.; Calvet, J.C.; Kerr, Y.

1998-01-01

Surface soil moisture is a key variable to describe the water and energy exchanges at the land surface/atmosphere interface. However, soil moisture is highly variable both spatially and temporally. Passive microwave remotely sensed data have great potential for providing estimates of soil moisture with good temporal repetition (on a daily basis) and at regional scale (∼ 10 km). This paper reviews the various methods for remote sensing of soil moisture from microwave radiometric systems. Potential applications from both airborne and spatial observations are discussed in the fields of agronomy, hydrology and meteorology. Emphasis in this paper is given to relatively new aspects of microwave techniques and of temporal soil moisture information analysis. In particular, the aperture synthesis technique allows us now to a address the soil moisture information needs on a global basis, from space instruments. (author) [fr

Dorzolamide Loaded Niosomal Vesicles: Comparison of Passive and Remote Loading Methods.

Science.gov (United States)

Hashemi Dehaghi, Mohadeseh; Haeri, Azadeh; Keshvari, Hamid; Abbasian, Zahra; Dadashzadeh, Simin

2017-01-01

Glaucoma is a common progressive eye disorder and the treatment strategies will benefit from nanoparticulate delivery systems with high drug loading and sustained delivery of intraocular pressure lowering agents. Niosomes have been reported as a novel approach to improve drug low corneal penetration and bioavailability characteristics. Along with this, poor entrapment efficiency of hydrophilic drug in niosomal formulation remains as a major formulation challenge. Taking this perspective into consideration, dorzolamide niosomes were prepared employing two different loading methodologies (passive and remote loading methods) and the effects of various formulation variables (lipid to drug ratio, cholesterol percentage, drug concentration, freeze/thaw cycles, TPGS content, and external and internal buffer molarity and pH) on encapsulation efficiency were assessed. Encapsulation of dorzolamide within niosomes increased remarkably by the incorporation of higher cholesterol percentage as well as increasing the total lipid concentration. Remote loading method showed higher efficacy for drug entrapment compared to passive loading technique. Incorporation of TPGS in bilayer led to decrease in EE; however, retarded drug release rate. Scanning electron microscopy (SEM) studies confirmed homogeneous particle distribution, and spherical shape with smooth surface. In conclusion, the highest encapsulation can be obtained using phosphate gradient method and 50% cholesterol in Span 60 niosomal formulation.

Resource management research in Passive Optical Networks (PON)

OpenAIRE

Garfias Hernández, Paola

2013-01-01

Next Generation Access Networks (NGAN) are the new step forward to deliver broadband services and to facilitate the integration of different technologies. It is plausible to assume that, from a technological standpoint, the Future Internet will be composed of long-range high-speed optical networks; a number of wireless networks at the edge; and, in between, several access technologies, among which, the Passive Optical Networks (xPON) are very likely to succeed, due to their simplicity, low-co...

A passive-active neutron device for assaying remote-handled transuranic waste

International Nuclear Information System (INIS)

Estep, R.J.; Coop, K.L.; Deane, T.M.; Lujan, J.E.

1990-01-01

A combined passive-active neutron assay device was constructed for assaying remote-handled transuranic waste. A study of matrix and source position effects in active assays showed that a knowledge of the source position alone is not sufficient to correct for position-related errors in highly moderating or absorbing matrices. An alternate function for the active assay of solid fuel pellets was derived, although the efficacy of this approach remains to be established

A Passive Optical Location with Limited Range

Directory of Open Access Journals (Sweden)

Pavel Fiala

2008-01-01

Full Text Available We know active and passive methods of a location. This article deals only with a passive location of dynamic targets. The passive optics location is suitable just for tracking of targets with mean velocity which is limited by the hardware basis. The aim of this work is to recognize plasma, particles etc. It is possible to propose such kind of evaluation methods which improve the capture probability markedly. Suggested method is dealing with the short-distance evaluation of targets. We suppose the application of three independent principles how to recognize an object in a scanned picture. These principles use similar stochastic functions in order to evaluate an object location by means of simple mathematical operations. Methods are based on direct evaluation of picture sequence by the help of the histogram and frequency spectrum. We find out the probability of unidentified moving object in pictures. If the probability reaches a setting value we will get a signal.

Space remote sensing systems an introduction

CERN Document Server

Chen, H S

1985-01-01

Space Remote Sensing Systems: An Introduction discusses the space remote sensing system, which is a modern high-technology field developed from earth sciences, engineering, and space systems technology for environmental protection, resource monitoring, climate prediction, weather forecasting, ocean measurement, and many other applications. This book consists of 10 chapters. Chapter 1 describes the science of the atmosphere and the earth's surface. Chapter 2 discusses spaceborne radiation collector systems, while Chapter 3 focuses on space detector and CCD systems. The passive space optical rad

No-go theorem for passive single-rail linear optical quantum computing.

Science.gov (United States)

Wu, Lian-Ao; Walther, Philip; Lidar, Daniel A

2013-01-01

Photonic quantum systems are among the most promising architectures for quantum computers. It is well known that for dual-rail photons effective non-linearities and near-deterministic non-trivial two-qubit gates can be achieved via the measurement process and by introducing ancillary photons. While in principle this opens a legitimate path to scalable linear optical quantum computing, the technical requirements are still very challenging and thus other optical encodings are being actively investigated. One of the alternatives is to use single-rail encoded photons, where entangled states can be deterministically generated. Here we prove that even for such systems universal optical quantum computing using only passive optical elements such as beam splitters and phase shifters is not possible. This no-go theorem proves that photon bunching cannot be passively suppressed even when extra ancilla modes and arbitrary number of photons are used. Our result provides useful guidance for the design of optical quantum computers.

Data acquisition remote node powered over the communications optical fiber

International Nuclear Information System (INIS)

Batista, Antonio J.N.; Sousa, Jorge; Gonçalves, Bruno

2015-01-01

Large nuclear fusion reactors, like ITER, will have harsh electromagnetic environments nearby the machine. Foreseeing the necessity for special data acquisition remote nodes, on difficult access locations and as close as possible to the experimental devices, motivated the system design. The architecture is based on the power-over-fiber technology recent advancements and respective implementation aim is to attain a proof of concept for the fusion technology field and others, e.g., high energy physics, industry, etc. The design intends the replacement of traditional copper cables and power supplies, vulnerable to electromagnetic interference, by the communications optical fiber of the data acquisition remote node. Optical fibers provide galvanic isolation, immunity to noisy electromagnetic environments and simultaneously can supply power to the remote node electronics. System architecture uses a laser power converter (array of photovoltaic cells) to convert the laser light, from the optical fiber, into electricity. The generated electrical power is enough for powering the remote node electronics and optoelectronics, such as an ADC, a low power FPGA and an optical transmitter. The laser power converter is also used as the communications receiver and from which the acquisition clock is recovered, providing synchronism between remote data acquisition nodes. Descriptions of the system architecture, tested implementations and future improvements are presented.

Multi-power-level Energy Saving Management for Passive Optical Networks

OpenAIRE

Taheri, Mina; Ansari, Nirwan

2014-01-01

Environmental concerns have motivated network designers to further reduce energy consumption of access networks. This paper focuses on reducing energy consumption of Ethernet passive optical network (EPON) as one of the most efficient transmission technologies for broadband access. In EPON, the downstream traffic is sent from the optical line terminal (OLT) located at the central office to all optical network units (ONUs). Each ONU checks all arrival downstream packets and selects the downstr...

A droplet-based passive force sensor for remote tactile sensing applications

Science.gov (United States)

Nie, Baoqing; Yao, Ting; Zhang, Yiqiu; Liu, Jian; Chen, Xinjian

2018-01-01

A droplet-based flexible wireless force sensor has been developed for remote tactile-sensing applications. By integration of a droplet-based capacitive sensing unit and two circular planar coils, this inductor-capacitor (LC) passive sensor offers a platform for the mechanical force detection in a wireless transmitting mode. Under external loads, the membrane surface of the sensor deforms the underlying elastic droplet uniformly, introducing a capacitance response in tens of picofarads. The LC circuit transduces the applied force into corresponding variations of its resonance frequency, which is detected by an external electromagnetic coupling coil. Specifically, the liquid droplet features a mechanosensitive plasticity, which results in an increased device sensitivity as high as 2.72 MHz N-1. The high dielectric property of the droplet endows our sensor with high tolerance for noise and large capacitance values (20-40 pF), the highest value in the literature for the LC passive devices in comparable dimensions. It achieves excellent reproducibility under periodical loads ranging from 0 to 1.56 N and temperature fluctuations ranging from 10 °C to 55 °C. As an interesting conceptual demonstration, the flexible device has been configured into a fingertip-amounted setting in a highly compact package (of 11 mm × 11 mm × 0.25 mm) for remote contact force sensing in the table tennis game.

Measurement of rain intensity by means of active-passive remote sensing

Science.gov (United States)

Linkova, Anna; Khlopov, Grygoriy

2014-05-01

Measurement of rain intensity is of great interest for municipal services and agriculture, particularly because of increasing number of floods and landslides. At that monitoring of amount of liquid precipitation allows to schedule work of hydrological services to inform the relevant public authorities about violent weather in time. That is why development of remote sensing methods for monitoring of rains is quite important task. The inverse problem solution of rain remote sensing is based on the measurements of scattering or radiation characteristics of rain drops. However liquid precipitation has a difficult structure which depends on many parameters. So using only scattering or radiation characteristics obtained by active and passive sensing at a single frequency does not allow to solve the inverse problem. Therefore double frequency sensing is widely used now for precipitation monitoring. Measurement of reflected power at two frequencies allows to find two parameters of drop size distribution of rain drops. However three-parameter distributions (for example gamma distribution) are the most prevalent now as a rain model, so in this case solution of the inverse problem requires the measurement of at least three uncorrelated variables. That is why a priori statistical meteorological data obtained by contact methods are used additionally to the double frequency sensing to solve the inverse problem. In particular, authors proposed and studied the combined method of double frequency sensing of rains based on dependence of the parameters of gamma distribution on rain intensity. The numerical simulation and experimental study shown that the proposed method allows to retrieve the profile of microstructure and integral parameters of rain with accuracy less than 15%. However, the effectiveness of the proposed method essentially depends on the reliability of the used statistical data which are tend to have a strong seasonal and regional variability led to significant

Optical Passive Sensor Calibration for Satellite Remote Sensing and the Legacy of NOAA and NIST Cooperation.

Science.gov (United States)

Datla, Raju; Weinreb, Michael; Rice, Joseph; Johnson, B Carol; Shirley, Eric; Cao, Changyong

2014-01-01

This paper traces the cooperative efforts of scientists at the National Oceanic and Atmospheric Administration (NOAA) and the National Institute of Standards and Technology (NIST) to improve the calibration of operational satellite sensors for remote sensing of the Earth's land, atmosphere and oceans. It gives a chronological perspective of the NOAA satellite program and the interactions between the two agencies' scientists to address pre-launch calibration and issues of sensor performance on orbit. The drive to improve accuracy of measurements has had a new impetus in recent years because of the need for improved weather prediction and climate monitoring. The highlights of this cooperation and strategies to achieve SI-traceability and improve accuracy for optical satellite sensor data are summarized.

An overview of passive remote sensing for post-fire monitoring

Directory of Open Access Journals (Sweden)

2005-01-01

Full Text Available Monitoring of forest burnt areas has several aims: to locate and estimate the extent of such areas; to assess the damages suffered by the forest stands; to check the ability of the ecosystem to naturally recover after the fire; to support the planning of reclamation interventions; to assess the dynamics (pattern and speed of the natural recovery; to check the outcome of any eventual restoration intervention. Remote sensing is an important source of information to support all such tasks. In the last decades, the effectiveness of remotely sensed imagery is increasing due to the advancement of tools and techniques, and to the lowering of the costs, in relative terms. For an effective support to post-fire management (burnt scar perimeter mapping, damage severity assessment, post-fire vegetation monitoring, a mapping scale of at least 1:10000-1:20000 is required: hence, the selection of remotely sensed data is restricted to aerial imagery and to satellite imagery characterized by high (HR and, above all, very high (VHR spatial resolution. In the last decade, HR and VHR passive remote sensing has widespread, providing affordable multitemporal and multispectral pictures of the considered phenomena, at different scales (spatial, temporal and spectral resolutions with reference to the monitoring needs. In the light of such a potential, the integration of GPS field survey and HR (Landsat 7, Spot HVR and VHR satellite imagery (Ikonos, Quickbird, Spot 5 is currently sought as a highly viable option for the post-fire monitoring.

All-optical, thermo-optical path length modulation based on the vanadium-doped fibers.

Science.gov (United States)

Matjasec, Ziga; Campelj, Stanislav; Donlagic, Denis

2013-05-20

This paper presents an all-fiber, fully-optically controlled, optical-path length modulator based on highly absorbing optical fiber. The modulator utilizes a high-power 980 nm pump diode and a short section of vanadium-co-doped single mode fiber that is heated through absorption and a non-radiative relaxation process. The achievable path length modulation range primarily depends on the pump's power and the convective heat-transfer coefficient of the surrounding gas, while the time response primarily depends on the heated fiber's diameter. An absolute optical length change in excess of 500 µm and a time-constant as short as 11 ms, were demonstrated experimentally. The all-fiber design allows for an electrically-passive and remote operation of the modulator. The presented modulator could find use within various fiber-optics systems that require optical (remote) path length control or modulation.

Integration of active and passive polymer optics

DEFF Research Database (Denmark)

Christiansen, Mads Brøkner; Schøler, Mikkel; Kristensen, Anders

2007-01-01

We demonstrate a wafer scale fabrication process for integration of active and passive polymer optics: Polymer DFB lasers and waveguides. Polymer dye DFB lasers are fabricated by combined nanoimprint and photolithography (CNP). The CNP fabrication relies on an UV transparent stamp with nm sized...... wavelength from temperature and refractive index changes in the surroundings is investigated, pointing towards the use of the described fabrication method for on-chip polymer sensor systems....

Delivery of video-on-demand services using local storages within passive optical networks.

Science.gov (United States)

Abeywickrama, Sandu; Wong, Elaine

2013-01-28

At present, distributed storage systems have been widely studied to alleviate Internet traffic build-up caused by high-bandwidth, on-demand applications. Distributed storage arrays located locally within the passive optical network were previously proposed to deliver Video-on-Demand services. As an added feature, a popularity-aware caching algorithm was also proposed to dynamically maintain the most popular videos in the storage arrays of such local storages. In this paper, we present a new dynamic bandwidth allocation algorithm to improve Video-on-Demand services over passive optical networks using local storages. The algorithm exploits the use of standard control packets to reduce the time taken for the initial request communication between the customer and the central office, and to maintain the set of popular movies in the local storage. We conduct packet level simulations to perform a comparative analysis of the Quality-of-Service attributes between two passive optical networks, namely the conventional passive optical network and one that is equipped with a local storage. Results from our analysis highlight that strategic placement of a local storage inside the network enables the services to be delivered with improved Quality-of-Service to the customer. We further formulate power consumption models of both architectures to examine the trade-off between enhanced Quality-of-Service performance versus the increased power requirement from implementing a local storage within the network.

Heuristic approach to the passive optical network with fibre duct ...

African Journals Online (AJOL)

Integer programming, network flow optimisation, passive optical network, ... This paper uses concepts from network flow optimisation to incorporate fibre duct shar ... [4] studied the survivable constrained ConFL problem and solved a number of.

Remote online process measurements by a fiber optic diode array spectrometer

International Nuclear Information System (INIS)

Van Hare, D.R.; Prather, W.S.; O'Rourke, P.E.

1986-01-01

The development of remote online monitors for radioactive process streams is an active research area at the Savannah River Laboratory (SRL). A remote offline spectrophotometric measurement system has been developed and used at the Savannah River Plant (SRP) for the past year to determine the plutonium concentration of process solution samples. The system consists of a commercial diode array spectrophotometer modified with fiber optic cables that allow the instrument to be located remotely from the measurement cell. Recently, a fiber optic multiplexer has been developed for this instrument, which allows online monitoring of five locations sequentially. The multiplexer uses a motorized micrometer to drive one of five sets of optical fibers into the optical path of the instrument. A sixth optical fiber is used as an external reference and eliminates the need to flush out process lines to re-reference the spectrophotometer. The fiber optic multiplexer has been installed in a process prototype facility to monitor uranium loading and breakthrough of ion exchange columns. The design of the fiber optic multiplexer is discussed and data from the prototype facility are presented to demonstrate the capabilities of the measurement system

Space Object Radiometric Modeling for Hardbody Optical Signature Database Generation

Science.gov (United States)

2009-09-01

Introduction This presentation summarizes recent activity in monitoring spacecraft health status using passive remote optical nonimaging ...Approved for public release; distribution is unlimited. Space Object Radiometric Modeling for Hardbody Optical Signature Database Generation...It is beneficial to the observer/analyst to understand the fundamental optical signature variability associated with these detection and

Parallel Void Thread in Long-Reach Ethernet Passive Optical Networks

KAUST Repository

Elrasad, Amr; Shihada, Basem

2015-01-01

This work investigates void filling (idle periods) in long-reach Ethernet passive optical networks. We focus on reducing grant delays and hence reducing the average packet delay. We introduce a novel approach called parallel void thread (PVT), which

Approach of the T-CONT Allocation to Increase the Bandwidth in Passive Optical Networks

Directory of Open Access Journals (Sweden)

Z. Bosternak

2017-12-01

Full Text Available This paper works with the simulation of T-CONT allocation and delay analysis in passive optical networks PON. Building our networks with the PON technology we can achieve increased data rates, however we need to ensure that the idle gaps between the particular transmissions are minimal. The primary method for the upstream time slot allocation in passive optical networks is via Multi Point Control Protocol. The baseline standard of this protocol clearly defines the use of the REPORT and GATE control messages. The two optical network elements used here, the optical network unit ONT and the optical line termination OLT, located at the central office CO, can be scheduled to allocate the time slots. Using the control messages, a more accurate scheduling algorithm can be developed, hence we can directly improve the utilization of the bandwidth as well. In this work, we introduce the basic topology of the passive optical networks, how PON works and what basic principles of bandwidth allocation have been applied. Subsequently, we suggest a selection of methods for time slot allocation and we make an analysis on the achieved results. Our main focus is on the system load, transfer delay and the analysis of the effectivity.

Experimental demonstration of SCMA-OFDM for passive optical network

Science.gov (United States)

Lin, Bangjiang; Tang, Xuan; Shen, Xiaohuan; Zhang, Min; Lin, Chun; Ghassemlooy, Zabih

2017-12-01

We introduces a novel architecture for next generation passive optical network (PON) based on the employment of sparse code multiple access (SCMA) combined with orthogonal frequency division multiplexing (OFDM) modulation, in which the binary data is directly encoded to multi-dimensional codewords and then spread over OFDM subcarriers. The feasibility of SCMA-OFDM-PON is verified with experimental demonstration. We show that the SCMA-OFDM offers 150% overloading gain in the number of optical network units compared with the orthogonal frequency division multiplexing access.

Design of Distortion-Invariant Optical ID Tags for Remote Identification and Verification of Objects

Science.gov (United States)

Pérez-Cabré, Elisabet; Millán, María Sagrario; Javidi, Bahram

Optical identification (ID) tags [1] have a promising future in a number of applications such as the surveillance of vehicles in transportation, control of restricted areas for homeland security, item tracking on conveyor belts or other industrial environment, etc. More specifically, passive optical ID tag [1] was introduced as an optical code containing a signature (that is, a characteristic image or other relevant information of the object), which permits its real-time remote detection and identification. Since their introduction in the literature [1], some contributions have been proposed to increase their usefulness and robustness. To increase security and avoid counterfeiting, the signature was introduced in the optical code as an encrypted function [2-5] following the double-phase encryption technique [6]. Moreover, the design of the optical ID tag was done in such a way that tolerance to variations in scale and rotation was achieved [2-5]. To do that, the encrypted information was multiplexed and distributed in the optical code following an appropriate topology. Further studies were carried out to analyze the influence of different sources of noise. In some proposals [5, 7], the designed ID tag consists of two optical codes where the complex-valued encrypted signature was separately introduced in two real-valued functions according to its magnitude and phase distributions. This solution was introduced to overcome some difficulties in the readout of complex values in outdoors environments. Recently, the fully phase encryption technique [8] has been proposed to increase noise robustness of the authentication system.

Remote nano-optical beam focusing lens by illusion optics

Science.gov (United States)

Margousi, David; Shoorian, Hamed Reza

2014-08-01

In this paper, as a new application of illusion optics, a nano-optical plasmonic focusing lens structure is proposed to manipulate the light remotely by employing illusion optics theory. Plasmonic nano-optic lenses that enable super-focusing beyond the diffraction limit have been proposed as an alternative to the conventional dielectric-based refractive lenses. In the presence of an illusion device, the electromagnetic plane-waves can penetrate into a metal layer and a clear focus appears. When the illusion device is removed, waves are blocked to transmit through the metal wall. In comparison with conventional methods, our proposed method avoids any physical changes or damages in the original structure. The proposed structure can be realized by isotropic layered materials, using effective medium theory. The special feature of the proposed structure and the device concepts introduced in this work gives it an opportunity to be used as a flexible element in ultrahigh nano-scale integrated circuits for miniaturization and tuning purposes.

Proceedings of the 1986 international geoscience and remote sensing symposium (IGARSS' 86) on remote sensing: today's solutions for tomorrow's information needs, volume 2

Energy Technology Data Exchange (ETDEWEB)

Guyenne, T.D.; Hunt, J.J.

1986-08-01

Remote sensing applications to agriculture; image processing methodology; active microwave sensing of the ocean; passive microwave sensing of vegetation and soils; radar forestry; hydrology; imaging radar missions; SAR observation of ocean waves; land analysis with optical sensors; and SAR system considerations were discussed.

Optical RAM row access using WDM-enabled all-passive row/column decoders

Science.gov (United States)

Papaioannou, Sotirios; Alexoudi, Theoni; Kanellos, George T.; Miliou, Amalia; Pleros, Nikos

2014-03-01

Towards achieving a functional RAM organization that reaps the advantages offered by optical technology, a complete set of optical peripheral modules, namely the Row (RD) and Column Decoder (CD) units, is required. In this perspective, we demonstrate an all-passive 2×4 optical RAM RD with row access operation and subsequent all-passive column decoding to control the access of WDM-formatted words in optical RAM rows. The 2×4 RD exploits a WDM-formatted 2-bit-long memory WordLine address along with its complementary value, all of them encoded on four different wavelengths and broadcasted to all RAM rows. The RD relies on an all-passive wavelength-selective filtering matrix (λ-matrix) that ensures a logical `0' output only at the selected RAM row. Subsequently, the RD output of each row drives the respective SOA-MZI-based Row Access Gate (AG) to grant/block the entry of the incoming data words to the whole memory row. In case of a selected row, the data word exits the row AG and enters the respective CD that relies on an allpassive wavelength-selective Arrayed Waveguide Grating (AWG) for decoding the word bits into their individual columns. Both RD and CD procedures are carried out without requiring any active devices, assuming that the memory address and data word bits as well as their inverted values will be available in their optical form by the CPU interface. Proof-of-concept experimental verification exploiting cascaded pairs of AWGs as the λ-matrix is demonstrated at 10Gb/s, providing error-free operation with a peak power penalty lower than 0.2dB for all optical word channels.

Method of remote powering and detecting multiple UWB passive tags in an RFID system

Science.gov (United States)

Dowla, Farid U [Castro Valley, CA; Nekoogar, Faranak [San Ramon, CA; Benzel, David M [Livermore, CA; Dallum, Gregory E [Livermore, CA; Spiridon, Alex [Palo Alto, CA

2012-05-29

A new Radio Frequency Identification (RFID), tracking, powering apparatus/system and method using coded Ultra-wideband (UWB) signaling is introduced. The proposed hardware and techniques disclosed herein utilize a plurality of passive UWB transponders in a field of an RFID-radar system. The radar system itself enables multiple passive tags to be remotely powered (activated) at about the same time frame via predetermined frequency UWB pulsed formats. Once such tags are in an activated state, an UWB radar transmits specific "interrogating codes" to put predetermined tags in an awakened status. Such predetermined tags can then communicate by a unique "response code" so as to be detected by an UWB system using radar methods.

Optical near-field lithography on hydrogen-passivated silicon surfaces

DEFF Research Database (Denmark)

Madsen, Steen; Müllenborn, Matthias; Birkelund, Karen

1996-01-01

by the optical near field, were observed after etching in potassium hydroxide. The uncoated fibers can also induce oxidation without light exposure, in a manner similar to an atomic force microscope, and linewidths of 50 nm have been achieved this way. (C) 1996 American Institute of Physics.......We report on a novel lithography technique for patterning of hydrogen-passivated amorphous silicon surfaces. A reflection mode scanning near-field optical microscope with uncoated fiber probes has been used to locally oxidize a thin amorphous silicon layer. Lines of 110 nm in width, induced...

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

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.

Passive Optical Access Networks: State of the Art and Future Evolution

Directory of Open Access Journals (Sweden)

Tommaso Muciaccia

2014-10-01

Full Text Available In the very last years, optical access networks are growing very rapidly, from both the network operators and the research interests points of view. Fiber To The Home (FTTH is already a reality in plenty of real contexts and there has been a further stimulus to the proposal of new solutions and the investigation of new possibilities, in order to optimize network performance and reduce capital and operational expenditure. A complete and systematic overview of passive optical access networks is presented in this paper, concerning both the hot research topics and the main operative issues about the design guidelines and the deployment of Passive Optical Networks (PON architectures, nowadays the most commonly implemented approach to realize optical fiber links in the access networks. A comparison of advantages and disadvantages of different multiplexing techniques is discussed, with specific reference to WDM-based networks, almost universally considered as the enabling technology for future proof bandwidth requirements. An exhaustive summary is also given about the-state-of-the-art of modulation and encoding techniques recently proposed by the scientific community, as well as the open challenges (such as colorless and coolerless ONUs for telecom companies and international standardization compliance.

Development of a NDI system using the magneto-optical method. 2. Remote sensing using the novel magneto-optical inspection system

International Nuclear Information System (INIS)

Lee, Jinyi; Shoji, Tetsuo

1999-01-01

A new remote sensing system using the magneto-optical method is developed for inspection of flaws introduced during service operation where routine inspection is difficult because of difficult inaccessibility to the components. Among the advantages of non-destructive inspection (NDI) based on the magneto-optical sensor are: real time inspection, elimination of electrical noise and high spatial resolution. Remote sensing of flaws is achieved using the basic principles of Faraday effect, optical permeability, and diffraction of a laser by the domain walls. This paper describes a novel remote NDI system using the principles of optics and LMF. The main characteristic of the system is that image data and LMF information can be obtained simultaneously. It is possible to carry out remote and high speed inspection of cracks from the intensity of reflected light, and to estimate the size of a crack effectively with their diverse data. The advantages of this NDI system are demonstrated using two specimens. (author)

Remote in-situ laser-induced breakdown spectroscopy using optical fibers

Science.gov (United States)

Marquardt, Brian James

The following dissertation describes the development of methods for performing remote Laser-Induced Breakdown Spectroscopy (LIBS) using optical fibers. Studies were performed to determine the optimal excitation and collection parameters for remote LIBS measurements of glasses, soils and paint. A number of fiber-optic LIBS probes were developed and used to characterize various samples by plasma emission spectroscopy. A novel method for launching high-power laser pulses into optical fibers without causing catastrophic failure is introduced. A systematic study of a number of commercially available optical fibers was performed to determine which optical fibers were best suited for delivering high-power laser pulses. The general design of an all fiber-optic LIBS probe is described and applied to the determination of Pb in soil. A fiber-optic probe was developed for the microanalysis of solid samples remotely by LIBS, Raman spectroscopy and Raman imaging. The design of the probe allows for real-time sample imaging in-situ using coherent imaging fibers. This allows for precise atomic emission and Raman measurements to be performed remotely on samples in hostile or inaccessible environments. A novel technique was developed for collecting spectral plasma images using an acousto-optic tunable filter (AOTF). The spatial and temporal characteristics of the plasma were studied as a function of delay time. From the plasma images the distribution of Pb emission could be determined and fiber-optic designs could be optimized for signal collection. The performance of a two fiber LIBS probe is demonstrated for the determination of the amount of lead in samples of dry paint. It is shown that dry paint samples can be analyzed for their Pb content in-situ using a fiber-optic LIBS probe with detection limits well below the levels currently regulated by the Consumer Products Safety Commission. It is also shown that these measurements can be performed on both latex and enamel paints, and

Using optical remote sensing model to estimate oil slick thickness based on satellite image

International Nuclear Information System (INIS)

Lu, Y C; Tian, Q J; Lyu, C G; Fu, W X; Han, W C

2014-01-01

An optical remote sensing model has been established based on two-beam interference theory to estimate marine oil slick thickness. Extinction coefficient and normalized reflectance of oil are two important parts in this model. Extinction coefficient is an important inherent optical property and will not vary with the background reflectance changed. Normalized reflectance can be used to eliminate the background differences between in situ measured spectra and remotely sensing image. Therefore, marine oil slick thickness and area can be estimated and mapped based on optical remotely sensing image and extinction coefficient

Remote optically-tunable transimpedance amplifiers for quantum well diodes

Energy Technology Data Exchange (ETDEWEB)

Carraresi, L.; Landi, G.; Rocchi, S.; Vignoli, V

1999-08-01

In a previous paper we discussed the advantages in using linear optical transmission systems based on quantum well diodes in modern high energy physics experiments. In this paper, after a short summary of the quantum well theory, the electronics section of the above optical transmission system is presented. In particular the basic configuration of a transimpedance amplifier and the arrangement of an optical remote control system for the amplifier gain and bandwidth tuning are discussed.

Remote optically-tunable transimpedance amplifiers for quantum well diodes

International Nuclear Information System (INIS)

Carraresi, L.; Landi, G.; Rocchi, S.; Vignoli, V.

1999-01-01

In a previous paper we discussed the advantages in using linear optical transmission systems based on quantum well diodes in modern high energy physics experiments. In this paper, after a short summary of the quantum well theory, the electronics section of the above optical transmission system is presented. In particular the basic configuration of a transimpedance amplifier and the arrangement of an optical remote control system for the amplifier gain and bandwidth tuning are discussed

Passive (self-powered) fiber-optic sensors

International Nuclear Information System (INIS)

McElhaney, S.A.; Falter, D.D.; Todd, R.A.; Simpson, M.L.; Mihalczo, J.T.

1992-01-01

ORNL is developing new group of fiber-optic sensors for characterizing physical aspects such as ambient temperature. These sensors exploit the inherent property of thermographic materials that the lifetime and/or intensity of the emitted fluorescence decreases with increasing temperature. Unlike current fluorescent temperature sensors that use a light source for excitation, these sensors are totally passive (self-powered) and use either an embedded or external radiation source. A proof-of-principle temperature sensor was developed, based on this concept, using a well-known thermographic material, magnesium fluorogermanate. Experimental results showed that the radiation-induced fluorescence resulted in an intensity change but no significant decay rate change with increasing temperature

Reliable clarity automatic-evaluation method for optical remote sensing images

Science.gov (United States)

Qin, Bangyong; Shang, Ren; Li, Shengyang; Hei, Baoqin; Liu, Zhiwen

2015-10-01

Image clarity, which reflects the sharpness degree at the edge of objects in images, is an important quality evaluate index for optical remote sensing images. Scholars at home and abroad have done a lot of work on estimation of image clarity. At present, common clarity-estimation methods for digital images mainly include frequency-domain function methods, statistical parametric methods, gradient function methods and edge acutance methods. Frequency-domain function method is an accurate clarity-measure approach. However, its calculation process is complicate and cannot be carried out automatically. Statistical parametric methods and gradient function methods are both sensitive to clarity of images, while their results are easy to be affected by the complex degree of images. Edge acutance method is an effective approach for clarity estimate, while it needs picking out the edges manually. Due to the limits in accuracy, consistent or automation, these existing methods are not applicable to quality evaluation of optical remote sensing images. In this article, a new clarity-evaluation method, which is based on the principle of edge acutance algorithm, is proposed. In the new method, edge detection algorithm and gradient search algorithm are adopted to automatically search the object edges in images. Moreover, The calculation algorithm for edge sharpness has been improved. The new method has been tested with several groups of optical remote sensing images. Compared with the existing automatic evaluation methods, the new method perform better both in accuracy and consistency. Thus, the new method is an effective clarity evaluation method for optical remote sensing images.

Soil Moisture Retrieval Using Convolutional Neural Networks: Application to Passive Microwave Remote Sensing

Science.gov (United States)

Hu, Z.; Xu, L.; Yu, B.

2018-04-01

A empirical model is established to analyse the daily retrieval of soil moisture from passive microwave remote sensing using convolutional neural networks (CNN). Soil moisture plays an important role in the water cycle. However, with the rapidly increasing of the acquiring technology for remotely sensed data, it's a hard task for remote sensing practitioners to find a fast and convenient model to deal with the massive data. In this paper, the AMSR-E brightness temperatures are used to train CNN for the prediction of the European centre for medium-range weather forecasts (ECMWF) model. Compared with the classical inversion methods, the deep learning-based method is more suitable for global soil moisture retrieval. It is very well supported by graphics processing unit (GPU) acceleration, which can meet the demand of massive data inversion. Once the model trained, a global soil moisture map can be predicted in less than 10 seconds. What's more, the method of soil moisture retrieval based on deep learning can learn the complex texture features from the big remote sensing data. In this experiment, the results demonstrates that the CNN deployed to retrieve global soil moisture can achieve a better performance than the support vector regression (SVR) for soil moisture retrieval.

SOIL MOISTURE RETRIEVAL USING CONVOLUTIONAL NEURAL NETWORKS: APPLICATION TO PASSIVE MICROWAVE REMOTE SENSING

Directory of Open Access Journals (Sweden)

Z. Hu

2018-04-01

Full Text Available A empirical model is established to analyse the daily retrieval of soil moisture from passive microwave remote sensing using convolutional neural networks (CNN. Soil moisture plays an important role in the water cycle. However, with the rapidly increasing of the acquiring technology for remotely sensed data, it's a hard task for remote sensing practitioners to find a fast and convenient model to deal with the massive data. In this paper, the AMSR-E brightness temperatures are used to train CNN for the prediction of the European centre for medium-range weather forecasts (ECMWF model. Compared with the classical inversion methods, the deep learning-based method is more suitable for global soil moisture retrieval. It is very well supported by graphics processing unit (GPU acceleration, which can meet the demand of massive data inversion. Once the model trained, a global soil moisture map can be predicted in less than 10 seconds. What's more, the method of soil moisture retrieval based on deep learning can learn the complex texture features from the big remote sensing data. In this experiment, the results demonstrates that the CNN deployed to retrieve global soil moisture can achieve a better performance than the support vector regression (SVR for soil moisture retrieval.

Sea Ice Concentration Estimation Using Active and Passive Remote Sensing Data Fusion

Science.gov (United States)

Zhang, Y.; Li, F.; Zhang, S.; Zhu, T.

2017-12-01

In this abstract, a decision-level fusion method by utilizing SAR and passive microwave remote sensing data for sea ice concentration estimation is investigated. Sea ice concentration product from passive microwave concentration retrieval methods has large uncertainty within thin ice zone. Passive microwave data including SSM/I, AMSR-E, and AMSR-2 provide daily and long time series observations covering whole polar sea ice scene, and SAR images provide rich sea ice details with high spatial resolution including deformation and polarimetric features. In the proposed method, the merits from passive microwave data and SAR data are considered. Sea ice concentration products from ASI and sea ice category label derived from CRF framework in SAR imagery are calibrated under least distance protocol. For SAR imagery, incident angle and azimuth angle were used to correct backscattering values from slant range to ground range in order to improve geocoding accuracy. The posterior probability distribution between category label from SAR imagery and passive microwave sea ice concentration product is modeled and integrated under Bayesian network, where Gaussian statistical distribution from ASI sea ice concentration products serves as the prior term, which represented as an uncertainty of sea ice concentration. Empirical model based likelihood term is constructed under Bernoulli theory, which meets the non-negative and monotonically increasing conditions. In the posterior probability estimation procedure, final sea ice concentration is obtained using MAP criterion, which equals to minimize the cost function and it can be calculated with nonlinear iteration method. The proposed algorithm is tested on multiple satellite SAR data sets including GF-3, Sentinel-1A, RADARSAT-2 and Envisat ASAR. Results show that the proposed algorithm can improve the accuracy of ASI sea ice concentration products and reduce the uncertainty along the ice edge.

Applications of optical fiber to remote laser fluorescence analysis

International Nuclear Information System (INIS)

Kim, Cheol Jung; Shin, Jang Soo; Lee, Sang Mock; Kim, Jeong Moog; Kim, Duk Heon; Hong, Seok Kyung

1991-12-01

Fluorescence analysis using time-resolved laser fluorimetry has been used for trace uranium analysis because this method shows high sensitivity and low detection limit and is less matrix dependent than any other fluorimetric measurement. By this time, the uranium analyses in the solution of reprocessing process or high radioactive area have been primarily analyzed by sampling of the solution, but recently, a study on a remote uranium fluorescence analysis using optical fiber has been setting out based on the development of an optical fiber with radiation resistivity and of an advanced laser excitation source. Laser fluorimetry developed by our laboratory for trace uranium analyses in uranium handling process or in urine samples of workers in a nuclear facility has been used in our institute since 1988. A development of the system for remote control of uranium fluorescence analysis will be expected to contribute to an on-line uranium concentration monitoring in the cooling water of reconversion stream. In this report, we summarize the information related to fluorescence analyses and remote fluorescence monitoring methods established by foreign countries and our laboratory. We also present a future research direction for remote on-line monitoring of uranium in conversion or reconversion process. (Author)

Including 10-Gigabit-capable Passive Optical Network under End-to-End Generalized Multi-Protocol Label Switching Provisioned Quality of Service

DEFF Research Database (Denmark)

Brewka, Lukasz Jerzy; Gavler, Anders; Wessing, Henrik

2012-01-01

of the network where quality of service signaling is bridged. This article proposes strategies for generalized multi-protocol label switching control over next emerging passive optical network standard, i.e., the 10-gigabit-capable passive optical network. Node management and resource allocation approaches...... are discussed, and possible issues are raised. The analysis shows that consideration of a 10-gigabit-capable passive optical network as a generalized multi-protocol label switching controlled domain is valid and may advance end-to-end quality of service provisioning for passive optical network based customers.......End-to-end quality of service provisioning is still a challenging task despite many years of research and development in this area. Considering a generalized multi-protocol label switching based core/metro network and resource reservation protocol capable home gateways, it is the access part...

Cost-effective parallel optical interconnection module based on fully passive-alignment process

Science.gov (United States)

Son, Dong Hoon; Heo, Young Soon; Park, Hyoung-Jun; Kang, Hyun Seo; Kim, Sung Chang

2017-11-01

In optical interconnection technology, high-speed and large data transitions with low error rate and cost reduction are key issues for the upcoming 8K media era. The researchers present notable types of optical manufacturing structures of a four-channel parallel optical module by fully passive alignment, which are able to reduce manufacturing time and cost. Each of the components, such as vertical-cavity surface laser/positive-intrinsic negative-photodiode array, microlens array, fiber array, and receiver (RX)/transmitter (TX) integrated circuit, is integrated successfully using flip-chip bonding, die bonding, and passive alignment with a microscope. Clear eye diagrams are obtained by 25.78-Gb/s (for TX) and 25.7-Gb/s (for RX) nonreturn-to-zero signals of pseudorandom binary sequence with a pattern length of 231 to 1. The measured responsivity and minimum sensitivity of the RX are about 0.5 A/W and ≤-6.5 dBm at a bit error rate (BER) of 10-12, respectively. The optical power margin at a BER of 10-12 is 7.5 dB, and cross talk by the adjacent channel is ≤1 dB.

Machine Learning on Images: Combining Passive Microwave and Optical Data to Estimate Snow Water Equivalent

Science.gov (United States)

Dozier, J.; Tolle, K.; Bair, N.

2014-12-01

We have a problem that may be a specific example of a generic one. The task is to estimate spatiotemporally distributed estimates of snow water equivalent (SWE) in snow-dominated mountain environments, including those that lack on-the-ground measurements. Several independent methods exist, but all are problematic. The remotely sensed date of disappearance of snow from each pixel can be combined with a calculation of melt to reconstruct the accumulated SWE for each day back to the last significant snowfall. Comparison with streamflow measurements in mountain ranges where such data are available shows this method to be accurate, but the big disadvantage is that SWE can only be calculated retroactively after snow disappears, and even then only for areas with little accumulation during the melt season. Passive microwave sensors offer real-time global SWE estimates but suffer from several issues, notably signal loss in wet snow or in forests, saturation in deep snow, subpixel variability in the mountains owing to the large (~25 km) pixel size, and SWE overestimation in the presence of large grains such as depth and surface hoar. Throughout the winter and spring, snow-covered area can be measured at sub-km spatial resolution with optical sensors, with accuracy and timeliness improved by interpolating and smoothing across multiple days. So the question is, how can we establish the relationship between Reconstruction—available only after the snow goes away—and passive microwave and optical data to accurately estimate SWE during the snow season, when the information can help forecast spring runoff? Linear regression provides one answer, but can modern machine learning techniques (used to persuade people to click on web advertisements) adapt to improve forecasts of floods and droughts in areas where more than one billion people depend on snowmelt for their water resources?

Short pulse generation from a passively mode-locked fiber optical parametric oscillator with optical time-stretch.

Science.gov (United States)

Qiu, Yi; Wei, Xiaoming; Du, Shuxin; Wong, Kenneth K Y; Tsia, Kevin K; Xu, Yiqing

2018-04-16

We propose a passively mode-locked fiber optical parametric oscillator assisted with optical time-stretch. Thanks to the lately developed optical time-stretch technique, the onset oscillating spectral components can be temporally dispersed across the pump envelope and further compete for the parametric gain with the other parts of onset oscillating sidebands within the pump envelope. By matching the amount of dispersion in optical time-stretch with the pulse width of the quasi-CW pump and oscillating one of the parametric sidebands inside the fiber cavity, we numerically show that the fiber parametric oscillator can be operated in a single pulse regime. By varying the amount of the intracavity dispersion, we further verify that the origin of this single pulse mode-locking regime is due to the optical pulse stretching and compression.

A Survivable Wavelength Division Multiplexing Passive Optical Network with Both Point-to-Point Service and Broadcast Service Delivery

Science.gov (United States)

Ma, Xuejiao; Gan, Chaoqin; Deng, Shiqi; Huang, Yan

2011-11-01

A survivable wavelength division multiplexing passive optical network enabling both point-to-point service and broadcast service is presented and demonstrated. This architecture provides an automatic traffic recovery against feeder and distribution fiber link failure, respectively. In addition, it also simplifies the protection design for multiple services transmission in wavelength division multiplexing passive optical networks.

Continuous Water Vapor Profiles from Operational Ground-Based Active and Passive Remote Sensors

Science.gov (United States)

Turner, D. D.; Feltz, W. F.; Ferrare, R. A.

2000-01-01

The Atmospheric Radiation Measurement program's Southern Great Plains Cloud and Radiation Testbed site central facility near Lamont, Oklahoma, offers unique operational water vapor profiling capabilities, including active and passive remote sensors as well as traditional in situ radiosonde measurements. Remote sensing technologies include an automated Raman lidar and an automated Atmospheric Emitted Radiance Interferometer (AERI), which are able to retrieve water vapor profiles operationally through the lower troposphere throughout the diurnal cycle. Comparisons of these two water vapor remote sensing methods to each other and to radiosondes over an 8-month period are presented and discussed, highlighting the accuracy and limitations of each method. Additionally, the AERI is able to retrieve profiles of temperature while the Raman lidar is able to retrieve aerosol extinction profiles operationally. These data, coupled with hourly wind profiles from a 915-MHz wind profiler, provide complete specification of the state of the atmosphere in noncloudy skies. Several case studies illustrate the utility of these high temporal resolution measurements in the characterization of mesoscale features within a 3-day time period in which passage of a dryline, warm air advection, and cold front occurred.

A novel WDM passive optical network architecture supporting two independent multicast data streams

Science.gov (United States)

Qiu, Yang; Chan, Chun-Kit

2012-01-01

We propose a novel scheme to perform optical multicast overlay of two independent multicast data streams on a wavelength-division-multiplexed (WDM) passive optical network. By controlling a sinusoidal clock signal and shifting the wavelength at the optical line terminal (OLT), the delivery of the two multicast data, being carried by the generated optical tones, can be independently and flexibly controlled. Simultaneous transmission of 10-Gb/s unicast downstream and upstream data as well as two independent 10-Gb/s multicast data was successfully demonstrated.

Study of passive optical network monitoring based on non-OTDR

Science.gov (United States)

Li, Chuan-qi; Wang, Da-chi; Hu, Jin-lin

2014-03-01

Aiming at the defects of passive optical network (PON) monitoring based on optical time domain reflectometry (OTDR) technology, we research the non-OTDR monitoring technology. The coding scheme based on periodic encoder monitoring is discussed, and its limitation is analyzed. On this basis, the monitoring technology based on optical code division multiple access (OCDMA) is put forward. We analyze the feasibility of monitoring scheme based on PON of OCDMA, design a monitoring plan, and then use OptiSystem to simulate the design. The results of simulation and bit error rate (BER) analysis show that this monitoring technology can overcome the deficiencies of OTDR and distinguish the monitoring signals of different fiber branches clearly, which meets the demands for high beam split ratio of multi-user communication.

Application of velocity filtering to optical-flow passive ranging

Science.gov (United States)

Barniv, Yair

1992-01-01

The performance of the velocity filtering method as applied to optical-flow passive ranging under real-world conditions is evaluated. The theory of the 3-D Fourier transform as applied to constant-speed moving points is reviewed, and the space-domain shift-and-add algorithm is derived from the general 3-D matched filtering formulation. The constant-speed algorithm is then modified to fit the actual speed encountered in the optical flow application, and the passband of that filter is found in terms of depth (sensor/object distance) so as to cover any given range of depths. Two algorithmic solutions for the problems associated with pixel interpolation and object expansion are developed, and experimental results are presented.

Gigabit Access Passive Optical Network Using Wavelength Division Multiplexing—GigaWaM

DEFF Research Database (Denmark)

Iglesias Olmedo, Miguel; Suhr, Lau; Prince, Kamau

2014-01-01

passive optical network (WDM-PON) architecture that can deliver symmetric 1 Gb/s to 64 users over 20 km standard single mode fiber using the L and C bands for down and upstream, respectively. During the course of the project, a number of key enabling technologies were developed including tunable......This paper summarizes the research and technical achievements done under the EU project GigaWaM. The goal of this project was to develop a cost-effective solution that can meet the increasing bandwidth demands in access networks. The approach was to use a novel wavelength division multiplexing...... transceivers, athermal 50 GHz spaced arrayed waveguide grating multiplexer devices, novel hybridization technologies for integration of passive and active electro-optic devices, and system-level algorithms that ensure the quality of service. The outcome of the project proved a reliable, cost...

New all-passive 4x4 planar optical phase diversity network

NARCIS (Netherlands)

Soldano, L.B.; Smit, M.K.; Vreede, De A.H.; Uffelen, van J.W.M.; Verbeek, B.H.; Bennekom, van P.K.; Krom, de W.H.C.; Etten, van W.C.

1991-01-01

The realisation and performance of an all-passive silicon-based 4*4 planar optical hybrid receiver for operation at 1.55- mu m wavelength is reported here for the first time. Measurements show 5 degrees /12 degrees /12 degrees /9 degrees output phase deviations, without tuning or trimming. Network

Modeling illumination performance of plastic optical fiber passive daylighting system

Energy Technology Data Exchange (ETDEWEB)

Sulaiman, F; Ahmad, A [Universiti Teknologi MARA, Shah Alam (Malaysia). Faculty of Electrical Engineering; Ahmed, A Z [Universiti Teknologi MARA, Shah Alam (Malaysia). Bureau of Reseaarch and Consultancy

2006-12-15

of the most direct methods of utilizing solar energy for energy conservation is to bring natural light indoors to light up an area. This paper reports on the investigation of the feasibility to utilize large core optical fibers to convey and distribute solar light passively throughout residential or commercial structures. The focus of this study is on the mathematical modeling of the illumination performance and the light transmission efficiency of solid core end light fiber for optical day lighting systems. The Meatball simulations features the optical fiber transmittance for glass and plastic fibers, illumination performance over lengths of plastic end-lit fiber, spectral transmission, light intensity loss through the large diameter solid core optical fibers as well as the transmission efficiency of the optical fiber itself. It was found that plastic optical fiber has less transmission loss over the distance of the fiber run which clearly shows that the Plastic Optical Fiber should be optimized for emitting visible light. The findings from the analysis on the performance of large diameter optical fibers for day lighting systems seems feasible for energy efficient lighting system in commercial or residential buildings.

Modeling illumination performance of plastic optical fiber passive daylighting system

International Nuclear Information System (INIS)

Sulaiman, F.; Ahmad, A.; Ahmed, A.Z.

2006-01-01

One of the most direct methods of utilizing solar energy for energy conservation is to bring natural light indoors to light up an area. This paper reports on the investigation of the feasibility to utilize large core optical fibers to convey and distribute solar light passively throughout residential or commercial structures. The focus of this study is on the mathematical modeling of the illumination performance and the light transmission efficiency of solid core end light fiber for optical day lighting systems. The Meatball simulations features the optical fiber transmittance for glass and plastic fibers, illumination performance over lengths of plastic end-lit fiber, spectral transmission, light intensity loss through the large diameter solid core optical fibers as well as the transmission efficiency of the optical fiber itself. It was found that plastic optical fiber has less transmission loss over the distance of the fiber run which clearly shows that the Plastic Optical Fiber should be optimized for emitting visible light. The findings from the analysis on the performance of large diameter optical fibers for day lighting systems seems feasible for energy efficient lighting system in commercial or residential buildings

Evaluation of remote delivery of Passive Integrated Transponder (PIT technology to mark large mammals.

Directory of Open Access Journals (Sweden)

W David Walter

Full Text Available Methods to individually mark and identify free-ranging wildlife without trapping and handling would be useful for a variety of research and management purposes. The use of Passive Integrated Transponder technology could be an efficient method for collecting data for mark-recapture analysis and other strategies for assessing characteristics about populations of various wildlife species. Passive Integrated Transponder tags (PIT have unique numbered frequencies and have been used to successfully mark and identify mammals. We tested for successful injection of PIT and subsequent functioning of PIT into gelatin blocks using 4 variations of a prototype dart. We then selected the prototype dart that resulted in the least depth of penetration in the gelatin block to assess the ability of PIT to be successfully implanted into muscle tissue of white-tailed deer (Odocoileus virginianus post-mortem and long-term in live, captive Rocky Mountain elk (Cervus elaphus. The prototype dart with a 12.7 mm (0.5 inch needle length and no powder charge resulted in the shallowest mean (± SD penetration depth into gelatin blocks of 27.0 mm (± 5.6 mm with 2.0 psi setting on the Dan-Inject CO(2-pressured rifle. Eighty percent of PIT were successfully injected in the muscle mass of white-tailed deer post-mortem with a mean (± SD penetration depth of 22.2 mm (± 3.8 mm; n = 6. We injected PIT successfully into 13 live, captive elk by remote delivery at about 20 m that remained functional for 7 months. We successfully demonstrated that PIT could be remotely delivered in darts into muscle mass of large mammals and remain functional for >6 months. Although further research is warranted to fully develop the technique, remote delivery of PIT technology to large mammals is possible using prototype implant darts.

A fiber optic link for the remote handling in nuclear environment

International Nuclear Information System (INIS)

Breuze, G.; Carnet, B.; Friant, A.; Blanc, F.; Lordet, J.; Boisde, G.

1988-01-01

At CEA a R/D program is running to improve performances of servomanipulators used in nuclear fuel reprocessing plants. Present work gives the main environmental parameters (gamma rays exposition, temperature) and shows the basis of the digital link designed to remote-handle such a manipulator. Up to 10 5 Gy behavior of optical fibers and electronic components was studied. Two different optical cables were built, one for the long link (100 m), the second to set in an especially designed winding unwinding wheel. Six way permanent or remote-handle connectors were developed to connect optical interfaces and a leaktight penetration. Measured budget of the link taking into account efficient photoblesching of the pure silica core fiber and influence of gamma rays on the slave interface is presented [fr

NASA Fluid Lensing & MiDAR: Next-Generation Remote Sensing Technologies for Aquatic Remote Sensing

Science.gov (United States)

Chirayath, Ved

2018-01-01

We present two recent instrument technology developments at NASA, Fluid Lensing and MiDAR, and their application to remote sensing of Earth's aquatic systems. Fluid Lensing is the first remote sensing technology capable of imaging through ocean waves in 3D at sub-cm resolutions. MiDAR is a next-generation active hyperspectral remote sensing and optical communications instrument capable of active fluid lensing. Fluid Lensing has been used to provide 3D multispectral imagery of shallow marine systems from unmanned aerial vehicles (UAVs, or drones), including coral reefs in American Samoa and stromatolite reefs in Hamelin Pool, Western Australia. MiDAR is being deployed on aircraft and underwater remotely operated vehicles (ROVs) to enable a new method for remote sensing of living and nonliving structures in extreme environments. MiDAR images targets with high-intensity narrowband structured optical radiation to measure an objectâ€"TM"s non-linear spectral reflectance, image through fluid interfaces such as ocean waves with active fluid lensing, and simultaneously transmit high-bandwidth data. As an active instrument, MiDAR is capable of remotely sensing reflectance at the centimeter (cm) spatial scale with a signal-to-noise ratio (SNR) multiple orders of magnitude higher than passive airborne and spaceborne remote sensing systems with significantly reduced integration time. This allows for rapid video-frame-rate hyperspectral sensing into the far ultraviolet and VNIR wavelengths. Previously, MiDAR was developed into a TRL 2 laboratory instrument capable of imaging in thirty-two narrowband channels across the VNIR spectrum (400-950nm). Recently, MiDAR UV was raised to TRL4 and expanded to include five ultraviolet bands from 280-400nm, permitting UV remote sensing capabilities in UV A, B, and C bands and enabling mineral identification and stimulated fluorescence measurements of organic proteins and compounds, such as green fluorescent proteins in terrestrial and

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

Science.gov (United States)

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

2017-03-01

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 airborne field campaigns: the North Atlantic Rainfall VALidation (NARVAL) mission, the Mid-Latitude Cirrus Experiment (ML-CIRRUS) and the Aerosol, Cloud, Precipitation, and Radiation Interactions and Dynamics of Convective Cloud Systems (ACRIDICON) campaign. Radiative transfer simulations are used to quantify the sensitivity of measured upward radiance I with respect to τ, ice crystal effective radius reff, viewing angle of the sensor θV, spectral surface albedo α, and ice crystal shape. From the calculations it is concluded that sideward viewing measurements are generally better suited than radiance data from the nadir direction to retrieve τ of optically thin cirrus, especially at wavelengths larger than λ = 900 nm. Using sideward instead of nadir-directed spectral radiance measurements significantly improves the sensitivity and accuracy in retrieving τ, in particular for optically thin cirrus of τ ≤ 2. The comparison of retrievals of τ based on nadir and sideward viewing radiance measurements from SMART, mini-DOAS and independent estimates of τ from an additional active remote sensing instrument, the Water Vapor Lidar Experiment in Space (WALES), shows general agreement within the range of measurement uncertainties. For the selected example a mean τ of 0.54 ± 0.2 is derived from SMART, and 0.49 ± 0.2 by mini-DOAS nadir channels, while WALES obtained a mean value of τ = 0.32 ± 0.02 at 532 nm wavelength, respectively. The mean of τ derived from the sideward viewing mini

Mechanism and look-alikes analysis of oil spill monitoring with optical remote sensing

Science.gov (United States)

Lan, Guoxin; Ma, Long; Li, Ying; Liu, Bingxin

2011-12-01

Remote Sensing surveillance constitutes an important component of oil spill disaster management system, but subject to monitoring accuracy and ability, which suffered from resolution, environmental conditions, and look-alikes. So this article aims to provide information of identification and distinguishing of look-alikes for optical sensors, and then improve the monitoring precision. Although limited by monitoring conditions of the atmosphere and night, optical satellite remote sensing can provide the intrinsic spectral information of the film and the background sea, then affords the potentiality for detailed identification of the film thickness, oil type classification (crude/light oil), trends, and sea surface roughness by multi-type data products. This paper focused on optical sensors and indicated that these false targets of sun glint, bottom feature, cloud shadow, suspend bed sediment and surface bioorganic are the main factors for false alarm in optical images. Based on the detailed description of the theory of oil spill detection in optical images, depending on the preliminary summary of the feature of look-alikes in visible-infrared bands, a discriminate criteria and work-flow for slicks identification are proposed. The results are helpful to improve the remote sensing monitoring ability and the contingency planning.

Sleep-time sizing and scheduling in green passive optical networks

KAUST Repository

Elrasad, Amr

2012-08-01

Next-generation passive optical network (PON) has been widely considered as a cost-effective broadband access technology. With the ever-increasing power saving concern, energy efficiency has been an important issue for its operations. In this paper, we present a novel sleep time sizing and scheduling framework that satisfies power efficient bandwidth allocation in PONs. We consider the downstream links from an optical line terminal (OLT) to an optical network unit (ONU). The ONU has two classes of traffic, control and data. Control traffic are delay intolerant with higher priority than the data traffic. Closed form model for average ONU sleeping time and end-to-end data traffic delay are presented and evaluated. Our framework decouples the dependency between ONU sleeping time and the QoS of the traffic.

Coherence Effects in L-Band Active and Passive Remote Sensing of Quasi-Periodic Corn Canopies

Science.gov (United States)

Utku, Cuneyt; Lang, Roger H.

2011-01-01

Due to their highly random nature, vegetation canopies can be modeled using the incoherent transport theory for active and passive remote sensing applications. Agricultural vegetation canopies however are generally more structured than natural vegetation. The inherent row structure in agricultural canopies induces coherence effects disregarded by the transport theory. The objective of this study is to demonstrate, via Monte-Carlo simulations, these coherence effects on L-band scattering and thermal emission from corn canopies consisting of only stalks.

A study on the multiple dynamic wavelength distribution for gigabit capable passive optical networks

Directory of Open Access Journals (Sweden)

Gustavo Adolfo Puerto Leguizamón

2014-04-01

Full Text Available This paper presents a data traffic based study aiming at evaluating the impact of dynamic wavelength allocation on a Gigabit capable Passive Optical Network (GPON. In Passive Optical Networks (PON, an Optical Line Terminal (OLT feeds different PONs in such a way that a given wavelength channel is evenly distributed between the Optical Network Units (ONU at each PON. However, PONs do not specify any kind of dynamic behavior on the way the wavelengths are allocated in the network, a completely static distribution is implemented instead. In thispaper we evaluate the network performance in terms of packet losses and throughput for a number of ONUs being out-of-profile while featuring a given percentage of traffic in excess for a fixed wavelength distribution and for multiple dynamic wavelength allocation. Results show that for a multichannel operation with four wavelengths, the network throughput increases up to a rough value of 19% while the packet losses drop from 22 % to 1.8 % as compared with a static wavelength distribution.

Experimental demonstration of time- and mode-division multiplexed passive optical network

Science.gov (United States)

Ren, Fang; Li, Juhao; Tang, Ruizhi; Hu, Tao; Yu, Jinyi; Mo, Qi; He, Yongqi; Chen, Zhangyuan; Li, Zhengbin

2017-07-01

A time- and mode-division multiplexed passive optical network (TMDM-PON) architecture is proposed, in which each optical network unit (ONU) communicates with the optical line terminal (OLT) independently utilizing both different time slots and switched optical linearly polarized (LP) spatial modes. Combination of a mode multiplexer/demultiplexer (MUX/DEUX) and a simple N × 1 optical switch is employed to select the specific LP mode in each ONU. A mode-insensitive power splitter is used for signal broadcast/combination between OLT and ONUs. We theoretically propose a dynamic mode and time slot assignment scheme for TMDM-PON based on inter-ONU priority rating, in which the time delay and packet loss ratio's variation tendency are investigated by simulation. Moreover, we experimentally demonstrate 2-mode TMDM-PON transmission over 10 km FMF with 10-Gb/s on-off keying (OOK) signal and direct detection.

MEMS acceleration sensor with remote optical readout for continuous power generator monitoring

Directory of Open Access Journals (Sweden)

Tormen Maurizio

2015-01-01

Full Text Available Miniaturized accelerometers with remote optical readout are required devices for the continuous monitoring of vibrations inside power generators. In turbo and hydro generators, end-winding vibrations are present during operation causing in the long term undesirable out-of-service repairs. Continuous monitoring of these vibrations is therefore mandatory. The high electromagnetic fields in the generators impose the use of devices immune to electromagnetic interferences. In this paper a MEMS based accelerometer with remote optical readout is presented. Advantages of the proposed device are the use of a differential optical signal to reject the common mode signal and noise, the reduced number of steps for the MEMS chip fabrication and for the system assembly, and the reduced package volume.

A light and faster regional convolutional neural network for object detection in optical remote sensing images

Science.gov (United States)

Ding, Peng; Zhang, Ye; Deng, Wei-Jian; Jia, Ping; Kuijper, Arjan

2018-07-01

Detection of objects from satellite optical remote sensing images is very important for many commercial and governmental applications. With the development of deep convolutional neural networks (deep CNNs), the field of object detection has seen tremendous advances. Currently, objects in satellite remote sensing images can be detected using deep CNNs. In general, optical remote sensing images contain many dense and small objects, and the use of the original Faster Regional CNN framework does not yield a suitably high precision. Therefore, after careful analysis we adopt dense convoluted networks, a multi-scale representation and various combinations of improvement schemes to enhance the structure of the base VGG16-Net for improving the precision. We propose an approach to reduce the test-time (detection time) and memory requirements. To validate the effectiveness of our approach, we perform experiments using satellite remote sensing image datasets of aircraft and automobiles. The results show that the improved network structure can detect objects in satellite optical remote sensing images more accurately and efficiently.

Self-match based on polling scheme for passive optical network monitoring

Science.gov (United States)

Zhang, Xuan; Guo, Hao; Jia, Xinhong; Liao, Qinghua

2018-06-01

We propose a self-match based on polling scheme for passive optical network monitoring. Each end-user is equipped with an optical matcher that exploits only the specific length patchcord and two different fiber Bragg gratings with 100% reflectivity. The simple and low-cost scheme can greatly simplify the final recognition processing of the network link status and reduce the sensitivity of the photodetector. We analyze the time-domain relation between reflected pulses and establish the calculation model to evaluate the false alarm rate. The feasibility of the proposed scheme and the validity of the time-domain relation analysis are experimentally demonstrated.

Remote artificial eyes using micro-optical circuit for long-distance 3D imaging perception.

Science.gov (United States)

Thammawongsa, Nopparat; Yupapin, Preecha P

2016-01-01

A small-scale optical device incorporated with an optical nano-antenna is designed to operate as the remote artificial eye using a tiny conjugate mirror. A basic device known as a conjugate mirror can be formed using the artificial eye device, the partially reflected light intensities from input source are interfered and the 3D whispering gallery modes formed within the ring centers, which can be modulated and propagated to the object. The image pixel is obtained at the center ring and linked with the optic nerve in the remote area via the nano-antenna, which is useful for blind people.

Development of optical apparatus with remote analysis in nuclear industry

Energy Technology Data Exchange (ETDEWEB)

Kim, Sung Ho; Cha, Byung Heon; Ko, Do Kyeong; Cha, Hyeong Ky

1999-12-01

Optical apparatus with remote analysis was developed. It is composed with Dye laser, optical fiber and optical transmitter, and optical corrector. Laser light is arming in untested sample, and there is back scattered fluorescence. Material is identified by detecting and analysis of this fluorescence. Liquid and solid dye laser was carry out. The maximum efficiency was up to 34 percent. and the divergency and bandwidth of laser light are 2 mrad and 4.2 GHz, respectively. A dye laser with two wavelength was also carry out. 3 inch optical transmitter with fluorite lens was developed and the spatial resolution was less than 2 arc sec. And large optical corrector with 6 inch was developed and that mirror was coated by enhanced aluminum. Thus the efficiency was up to 92 percent. (author)

Semiconductor optical amplifier-based heterodyning detection for resolving optical terahertz beat-tone signals from passively mode-locked semiconductor lasers

International Nuclear Information System (INIS)

Latkowski, Sylwester; Maldonado-Basilio, Ramon; Carney, Kevin; Parra-Cetina, Josue; Philippe, Severine; Landais, Pascal

2010-01-01

An all-optical heterodyne approach based on a room-temperature controlled semiconductor optical amplifier (SOA) for measuring the frequency and linewidth of the terahertz beat-tone signal from a passively mode-locked laser is proposed. Under the injection of two external cavity lasers, the SOA acts as a local oscillator at their detuning frequency and also as an optical frequency mixer whose inputs are the self-modulated spectrum of the device under test and the two laser beams. Frequency and linewidth of the intermediate frequency signal (and therefore, the beat-tone signal) are resolved by using a photodiode and an electrical spectrum analyzer.

Optical and electrical study of CdZnTe surfaces passivated by KOH and NH{sub 4}F solutions

Energy Technology Data Exchange (ETDEWEB)

Zázvorka, J., E-mail: zazvorka.jakub@gmail.com [Institute of Physics, Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 5, 121 16 Prague (Czech Republic); Franc, J.; Statelov, M.; Pekárek, J.; Veis, M.; Moravec, P. [Institute of Physics, Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 5, 121 16 Prague (Czech Republic); Mašek, K. [Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University in Prague, V Holešovičkách 2, CZ, 18000 Prague (Czech Republic)

2016-12-15

Highlights: • Surface of CdZnTe samples was passivated after chemical etching. • KOH and NH{sub 4}F solutions were used as passivation agents. • Growth of surface oxide after passivation is observed. • Surface oxide thickness was evaluated over time after chemical treatment. • Oxidation of the sample correlates with decreased leakage current. - Abstract: Performance of CdZnTe-based detectors is highly related to surface preparation. Mechanical polishing, chemical etching and passivation are routinely employed for this purpose. However, the relation between these processes and the detector performance in terms of underlying physical phenomena has not been fully explained. The dynamics and properties of CdZnTe surface oxide layers, created by passivation with KOH and NH4F/H2O2 solutions, were studied by optical ellipsometry and X-ray photoelectron spectroscopy (XPS). Thicknesses and growth rates of the surface oxide layers differed for each of the passivation methods. Leakage currents which influence the final spectral resolution of the detector were measured simultaneously with ellipsometry. Results of both optical and electrical investigation showed the same trends in the time evolution and correlated to each other. NH4F/H2O2 passivation showed to be a method which produces the most desirable properties of the surface oxide layer.

Experimental demonstration of IDMA-OFDM for passive optical network

Science.gov (United States)

Lin, Bangjiang; Tang, Xuan; Li, Yiwei; Zhang, Min; Lin, Chun; Ghassemlooy, Zabih

2017-11-01

We present interleave division multiple access (IDMA) scheme combined with orthogonal frequency division multiplexing (OFDM) for passive optical network, which offers improved transmission performance and good chromatic dispersion tolerance. The interleavers are employed to separate different users and the generated chips are modulated on OFDM subcarriers. The feasibility of IDMA-OFDM-PON is experimentally verified with a bitrate of 3.3 Gb/s per user. Compared with OFDMA, IDMA-OFDM offers 8 and 6 dB gains in term of receiver sensitivity in the cases of 2 and 4 users, respectively.

Estimating dissolved organic carbon concentration in turbid coastal waters using optical remote sensing observations

Science.gov (United States)

Cherukuru, Nagur; Ford, Phillip W.; Matear, Richard J.; Oubelkheir, Kadija; Clementson, Lesley A.; Suber, Ken; Steven, Andrew D. L.

2016-10-01

Dissolved Organic Carbon (DOC) is an important component in the global carbon cycle. It also plays an important role in influencing the coastal ocean biogeochemical (BGC) cycles and light environment. Studies focussing on DOC dynamics in coastal waters are data constrained due to the high costs associated with in situ water sampling campaigns. Satellite optical remote sensing has the potential to provide continuous, cost-effective DOC estimates. In this study we used a bio-optics dataset collected in turbid coastal waters of Moreton Bay (MB), Australia, during 2011 to develop a remote sensing algorithm to estimate DOC. This dataset includes data from flood and non-flood conditions. In MB, DOC concentration varied over a wide range (20-520 μM C) and had a good correlation (R2 = 0.78) with absorption due to coloured dissolved organic matter (CDOM) and remote sensing reflectance. Using this data set we developed an empirical algorithm to derive DOC concentrations from the ratio of Rrs(412)/Rrs(488) and tested it with independent datasets. In this study, we demonstrate the ability to estimate DOC using remotely sensed optical observations in turbid coastal waters.

Passive sensor systems for nuclear material monitoring

International Nuclear Information System (INIS)

Simpson, M.L.; Boatner, L.A.; Holcomb, D.E.; McElhaney, S.A.; Mihalczo, J.T.; Muhs, J.D.; Roberts, M.R.; Hill, N.W.

1993-01-01

Passive fiber optic sensor systems capable of confirming the presence of special nuclear materials in storage or process facilities are being developed at Oak Ridge National Laboratory (ORNL). These sensors provide completely passive, remote measurement capability. No power supplies, amplifiers, or other active components that could degrade system reliability are required at the sensor location. ORNL, through its research programs in scintillator materials, has developed a variety of materials for use in alpha-, beta-, gamma-, and neutron-sensitive scintillator detectors. In addition to sensors for measuring radiation flux, new sensor materials have been developed which are capable of measuring weight, temperature, and source location. An example of a passive sensor for temperature measurement is the combination of a thermophosphor (e.g., rare-earth activated Y 2 O 3 ) with 6 LiF (95% 6 Li). This combination results in a new class of scintillators for thermal neutrons that absorb energy from the radiation particles and remit the energy as a light pulse, the decay rate of which, over a specified temperature range, is temperature dependent. Other passive sensors being developed include pressure-sensitive triboluminescent materials, weight-sensitive silicone rubber fibers, scintillating fibers, and other materials for gamma and neutron detection. The light from the scintillator materials of each sensor would be sent through optical fibers to a monitoring station, where the attribute quantity could be measured and compared with previously recorded emission levels. Confirmatory measurement applications of these technologies are being evaluated to reduce the effort, costs, and employee exposures associated with inventorying stockpiles of highly enriched uranium at the Oak Ridge Y-12 Plant

Surface Passivation of Silicon Using HfO2 Thin Films Deposited by Remote Plasma Atomic Layer Deposition System.

Science.gov (United States)

Zhang, Xiao-Ying; Hsu, Chia-Hsun; Lien, Shui-Yang; Chen, Song-Yan; Huang, Wei; Yang, Chih-Hsiang; Kung, Chung-Yuan; Zhu, Wen-Zhang; Xiong, Fei-Bing; Meng, Xian-Guo

2017-12-01

Hafnium oxide (HfO 2 ) thin films have attracted much attention owing to their usefulness in equivalent oxide thickness scaling in microelectronics, which arises from their high dielectric constant and thermodynamic stability with silicon. However, the surface passivation properties of such films, particularly on crystalline silicon (c-Si), have rarely been reported upon. In this study, the HfO 2 thin films were deposited on c-Si substrates with and without oxygen plasma pretreatments, using a remote plasma atomic layer deposition system. Post-annealing was performed using a rapid thermal processing system at different temperatures in N 2 ambient for 10 min. The effects of oxygen plasma pretreatment and post-annealing on the properties of the HfO 2 thin films were investigated. They indicate that the in situ remote plasma pretreatment of Si substrate can result in the formation of better SiO 2 , resulting in a better chemical passivation. The deposited HfO 2 thin films with oxygen plasma pretreatment and post-annealing at 500 °C for 10 min were effective in improving the lifetime of c-Si (original lifetime of 1 μs) to up to 67 μs.

Tunable optical frequency comb enabled scalable and cost-effective multiuser orthogonal frequency-division multiple access passive optical network with source-free optical network units.

Science.gov (United States)

Chen, Chen; Zhang, Chongfu; Liu, Deming; Qiu, Kun; Liu, Shuang

2012-10-01

We propose and experimentally demonstrate a multiuser orthogonal frequency-division multiple access passive optical network (OFDMA-PON) with source-free optical network units (ONUs), enabled by tunable optical frequency comb generation technology. By cascading a phase modulator (PM) and an intensity modulator and dynamically controlling the peak-to-peak voltage of a PM driven signal, a tunable optical frequency comb source can be generated. It is utilized to assist the configuration of a multiple source-free ONUs enhanced OFDMA-PON where simultaneous and interference-free multiuser upstream transmission over a single wavelength can be efficiently supported. The proposed multiuser OFDMA-PON is scalable and cost effective, and its feasibility is successfully verified by experiment.

Remote sensing systems – Platforms and sensors: Aerial, satellites, UAVs, optical, radar, and LiDAR: Chapter 1

Science.gov (United States)

Panda, Sudhanshu S.; Rao, Mahesh N.; Thenkabail, Prasad S.; Fitzerald, James E.

2015-01-01

The American Society of Photogrammetry and Remote Sensing defined remote sensing as the measurement or acquisition of information of some property of an object or phenomenon, by a recording device that is not in physical or intimate contact with the object or phenomenon under study (Colwell et al., 1983). Environmental Systems Research Institute (ESRI) in its geographic information system (GIS) dictionary defines remote sensing as “collecting and interpreting information about the environment and the surface of the earth from a distance, primarily by sensing radiation that is naturally emitted or reflected by the earth’s surface or from the atmosphere, or by sending signals transmitted from a device and reflected back to it (ESRI, 2014).” The usual source of passive remote sensing data is the measurement of reflected or transmitted electromagnetic radiation (EMR) from the sun across the electromagnetic spectrum (EMS); this can also include acoustic or sound energy, gravity, or the magnetic field from or of the objects under consideration. In this context, the simple act of reading this text is considered remote sensing. In this case, the eye acts as a sensor and senses the light reflected from the object to obtain information about the object. It is the same technology used by a handheld camera to take a photograph of a person or a distant scenic view. Active remote sensing, however, involves sending a pulse of energy and then measuring the returned energy through a sensor (e.g., Radio Detection and Ranging [RADAR], Light Detection and Ranging [LiDAR]). Thermal sensors measure emitted energy by different objects. Thus, in general, passive remote sensing involves the measurement of solar energy reflected from the Earth’s surface, while active remote sensing involves synthetic (man-made) energy pulsed at the environment and the return signals are measured and recorded.

Multifunctional fiber-optic microwave links based on remote heterodyne detection

DEFF Research Database (Denmark)

Gliese, Ulrik Bo; Nielsen, Torben Nørskov; Nielsen, Søren Nørskov

1998-01-01

The multifunctionality of microwave links based on remote heterodyne detection (RHD) of signals from a dual-frequency laser transmitter is discussed and experimentally demonstrated in this paper. Typically, direct detection (DD) in conjunction with optical intensity modulation is used to implement...... fiber-optic microwave links. The resulting links are inherently transparent. As opposed to DD links, RHD links can perform radio-system functionalities such as modulation and frequency conversion in addition to transparency. All of these three functionalities are presented and experimentally...

Architecture and Design of IP Broadcasting System Using Passive Optical Network

Science.gov (United States)

Ikeda, Hiroki; Sugawa, Jun; Ashi, Yoshihiro; Sakamoto, Kenichi

We propose an IP broadcasting system architecture using passive optical networks (PON) utilizing the optical broadcast links of a PON with a downstream bandwidth allocation algorithm to provide a multi-channel IP broadcasting service to home subscribers on single broadband IP network infrastructures. We introduce the design and adaptation of the optical broadcast links to effectively broadcast video contents to home subscribers. We present a performance analysis that includes the downstream bandwidth utilization efficiency of the broadcast link and the bandwidth control of the IP broadcasting and Internet data. Our analysis and simulation results show that the proposed system can provide 100 HDTV channels to every user over fiber lines. We also propose an IPTV channel selection mechanism in an ONT by selecting a broadcast stream. We developed and evaluated a prototype that can achieve a 15-msec IPTV channel selection speed.

Excellent Silicon Surface Passivation Achieved by Industrial Inductively Coupled Plasma Deposited Hydrogenated Intrinsic Amorphous Silicon Suboxide

Directory of Open Access Journals (Sweden)

Jia Ge

2014-01-01

Full Text Available We present an alternative method of depositing a high-quality passivation film for heterojunction silicon wafer solar cells, in this paper. The deposition of hydrogenated intrinsic amorphous silicon suboxide is accomplished by decomposing hydrogen, silane, and carbon dioxide in an industrial remote inductively coupled plasma platform. Through the investigation on CO2 partial pressure and process temperature, excellent surface passivation quality and optical properties are achieved. It is found that the hydrogen content in the film is much higher than what is commonly reported in intrinsic amorphous silicon due to oxygen incorporation. The observed slow depletion of hydrogen with increasing temperature greatly enhances its process window as well. The effective lifetime of symmetrically passivated samples under the optimal condition exceeds 4.7 ms on planar n-type Czochralski silicon wafers with a resistivity of 1 Ωcm, which is equivalent to an effective surface recombination velocity of less than 1.7 cms−1 and an implied open-circuit voltage (Voc of 741 mV. A comparison with several high quality passivation schemes for solar cells reveals that the developed inductively coupled plasma deposited films show excellent passivation quality. The excellent optical property and resistance to degradation make it an excellent substitute for industrial heterojunction silicon solar cell production.

Feasibility Study on Fiber-optic Radiation Sensor for Remote Gamma-ray Spectroscopy

International Nuclear Information System (INIS)

Jeon, Hyesu; Jang, Kyoung Won; Shin, Sang Hun and others

2014-01-01

In this study, we fabricated a fiber-optic radiation sensor using an optical fiber and various scintillators. To select an adequate inorganic scintillator for the sensing probe of fiber-optic radiation sensor, 5 types of scintillators were evaluated. The spectra of gamma-rays emitted from a Na-22 radiation source were measured by using the manufactured sensors. As a result, the BGO was suitable for the sensing probe of fiber-optic radiation sensor due to its high scintillation output and exact photoelectric peak for the gamma-ray energy. The basic principle of radiation detection is to detect the signals caused by interactions between radiations and materials. There are various types of radiation detectors depending on types of radiation to be detected and physical quantities to be measured. As one of the radiation detectors, a fiber-optic radiation sensor using a scintillator and an optical fiber has two advantages such as no space restraint and remote sensing. Moreover, in nuclear environments, this kind of sensor has immunities for electromagnetic field, temperature, and pressure. Thus, the fiber-optic radiation sensor can be used in various fields including nondestructive inspection, radioactive waste management, nuclear safety, radiodiagnosis and radiation therapy. As a fundamental study of the fiber-optic radiation sensor for remote gamma-ray spectroscopy, in this study, we fabricated a fiber-optic radiation sensor using an optical fiber and various scintillators. To select an adequate inorganic scintillator for the sensing probe of fiber-optic radiation sensor, 5 types of scintillators were evaluated. The spectra of gamma-rays emitted from a Na-22 radiation source were measured by using the manufactured sensors

Proceedings of the 1986 international geoscience and remote sensing symposium (IGARSS '86) on remote sensing: today's solutions for tomorrow's information needs, volume 1

Energy Technology Data Exchange (ETDEWEB)

Guyenne, T.D.; Hunt, J.J.

1986-08-01

New instruments with enormous information gathering abilities are being planned to provide data from all parts of the spectrum. New data processing and storage hardware, combined with fundamental advances in information systems concepts and algorithms are awaiting the research efforts to mold them for special use. Some topics covered in the proceedings are: Optical and infrared remote sensing systems; information transfer and Third World development; wave target interaction mechanisms; microwave remote sensing of sea ice; ERS-1 sensor performance, calibration, and data validation; geophysics; imaging spectrometry; image analysis systems; ocean radar scattering; marginal ice zone remote sensing; geomorphology; SAR applications; geology; multispectral image analysis; ocean wind scatterometry; passive microwave sensing; radar mapping and land use; meteorology and atmospheric sounding; and radar instrumentation.

Nonimaging optical designs for maximum-power-density remote irradiation.

Science.gov (United States)

Feuermann, D; Gordon, J M; Ries, H

1998-04-01

Designs for flexible, high-power-density, remote irradiation systems are presented. Applications include industrial infrared heating such as in semiconductor processing, alternatives to laser light for certain medical procedures, and general remote high-brightness lighting. The high power densities in herent to the small active radiating regions of conventional metal-halide, halogen, xenon, microwave-sulfur, and related lamps can be restored with nonimaging concentrators with little loss of power. These high fluxlevels can then be transported at high transmissivity with light channels such as optical fibers or lightpipes, and reshaped into luminaires that can deliver prescribed angular and spatial flux distributions onto desired targets. Details for nominally two- and three-dimensional systems are developed, along with estimates ofoptical performance.

Macrophysical properties of continental cumulus clouds from active and passive remote sensing

Energy Technology Data Exchange (ETDEWEB)

Kassianov, Evgueni I.; Riley, Erin A.; Kleiss, Jessica; Long, Charles N.; Riihimaki, Laura D.; Flynn, Donna M.; Flynn, Connor J M.; Berg, Larry K.

2017-10-06

Cloud amount is an essential and extensively used macrophysical parameter of cumulus clouds. It is commonly defined as a cloud fraction (CF) from zenith-pointing ground-based active and passive remote sensing. However, conventional retrievals of CF from the remote sensing data with very narrow field-of-view (FOV) may not be representative of the surrounding area. Here we assess its representativeness using an integrated dataset collected at the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) program's Southern Great Plains (SGP) site in Oklahoma, USA. For our assessment with focus on selected days with single-layer cumulus clouds (2005-2016), we include the narrow-FOV ARM Active Remotely Sensed Clouds Locations (ARSCL) and large-FOV Total Sky Imager (TSI) cloud products, the 915-MHz Radar Wind Profiler (RWP) measurements of wind speed and direction, and also high-resolution satellite images from Landsat and the Moderate Resolution Imaging Spectroradiometer (MODIS). We demonstrate that a root-mean-square difference (RMSD) between the 15-min averaged ARSCL cloud fraction (CF) and the 15-min averaged TSI fractional sky cover (FSC) is large (up to 0.3). We also discuss how the horizontal distribution of clouds can modify the obtained large RMSD using a new uniformity metric. The latter utilizes the spatial distribution of the FSC over the 100° FOV TSI images obtained with high temporal resolution (30 sec sampling). We demonstrate that cases with more uniform spatial distribution of FSC show better agreement between the narrow-FOV CF and large-FOV FSC, reducing the RMSD by up to a factor of 2.

First-principle study on optical properties of spherical and cylindrical hydrogen-passivated Si nanoparticles with different sizes

NARCIS (Netherlands)

Wang, Yinglong; Chen, Chao; Wu, Zhuanhua; Liang, Weihua; Wang, Xiuli; Ding, Xuecheng; Chu, Lizhi; Deng, Zechao; Chen, Jinzhong; Fu, Guangsheng

To investigate the size dependence of the optical properties of the hydrogen-passivated Si nanoparticles (Hp-SiNPs), the energy bands and optical dielectric functions for two types of nanostructures, that is, the spherical Hp-SiNPs (SHp-SiNPs) with various diameters and the cylindrical Hp-SiNPs

Remote-controlled optics experiment for supporting senior high school and undergraduate teaching

Science.gov (United States)

Choy, S. H.; Jim, K. L.; Mak, C. L.; Leung, C. W.

2017-08-01

This paper reports the development of a remote laboratory (RemoteLab) platform for practising technologyenhanced learning of optics. The development of RemoteLab enhances students' understanding of experimental methodologies and outcomes, and enable students to conduct experiments everywhere at all times. While the initial goal of the system was for physics major undergradutes, the sytem was also made available for senior secondary school students. To gauge the impact of the RemoteLab, we evaluated two groups of students, which included 109 physics 1st-year undergraduates and 11 students from a local secondary school. After the experiments, evaluation including questionnaire survey and interviews were conducted to collect data on students' perceptions on RemoteLab and implementation issues related to the platform. The surveys focused on four main topics, including user interface, experiment setup, booking system and learning process. The survey results indicated that most of the participants' views towards RemoteLab was positive.

The potential of the synergistic use of passive and active remote sensing measurements for the validation of a regional dust model

Directory of Open Access Journals (Sweden)

V. Amiridis

2009-08-01

Full Text Available A long-lasting Saharan dust event affected Europe on 18–23 May 2008. Dust was present in the free troposphere over Greece, in height ranges between the surface and approximately 4–5 km above sea level. The event was monitored by ground-based CIMEL sunphotometric and multi-wavelength combined backscatter/Raman lidar measurements over Athens, Greece. The dust event had the maximum of its intensity on 20 May. Three-dimensional dust spatial distribution over Greece on that day is presented through satellite synergy of passive and active remote sensing using MODIS and CALIPSO data, respectively. For the period under study, the ground-based measurements are used to characterize the dust event and evaluate the latest version of the BSC Dust Regional Atmospheric Modeling (BSC-DREAM system. Comparisons of modeled and measured aerosol optical depths over Athens show that the Saharan dust outbreak is fairly well captured by BSC-DREAM simulations. Evaluation of BSC-DREAM using Raman lidar measurements on 20 May shows that the model consistently reproduces the dust vertical distribution over Athens.

The Design of Passive Optical Networking+Ethernet over Coaxial Cable Access Networking and Video-on-Demand Services Carrying

Science.gov (United States)

Ji, Wei

2013-07-01

Video on demand is a very attractive service used for entertainment, education, and other purposes. The design of passive optical networking+Ethernet over coaxial cable accessing and a home gateway system is proposed. The network integrates the passive optical networking and Ethernet over coaxial cable to provide high dedicated bandwidth for the metropolitan video-on-demand services. Using digital video broadcasting, IP television protocol, unicasting, and broadcasting mechanisms maximizes the system throughput. The home gateway finishes radio frequency signal receiving and provides three kinds of interfaces for high-definition video, voice, and data, which achieves triple-play and wire/wireless access synchronously.

Overflow control mechanism (OCM) for Ethernet passive optical networks (EPONs)

Science.gov (United States)

Hajduczenia, Marek; da Silva, Henrique J. A.; Monteiro, Paulo P.

2007-05-01

The nonfragmentable nature of Ethernet data frames, as well as operation of the priority oriented packet schedulers in the optical network units, in conjunction with heavy network load conditions and the lack of detailed knowledge about the queue's composition at the optical line terminal (OLT) level, result in the creation of upstream channel slot remainders. The existing methods, in the form of nonpreemptive packet schedulers and multithreshold reporting process defined vaguely by the IEEE 802.3-2005 standard, result in either increased packet delay or Ethernet passive optical network (EPON) system incompatibility, respectively, since threshold processing was never officially defined in the scope of the respective EPON standard. We propose an alternative approach, based on basic modifications of the standard and extended GATE multipoint control protocol data unit format and meaning, allowing for the OLT packet scheduling agent to grant always exactly the requested slot size, thus preventing creation of any upstream channel slot remainders. It is estimated that, on average, ˜3% of upstream channel bandwidth can be salvaged when slot remainders are absent in the upstream channel transmission.

AIRBORNE, OPTICAL REMOTE SENSING OF METHANE AND ETHANE FOR NATURAL GAS PIPELINE LEAK DETECTION

Energy Technology Data Exchange (ETDEWEB)

Jerry Myers

2003-11-12

Ophir Corporation was awarded a contract by the U. S. Department of Energy, National Energy Technology Laboratory under the Project Title ''Airborne, Optical Remote Sensing of Methane and Ethane for Natural Gas Pipeline Leak Detection'' on October 14, 2002. This second six-month technical report summarizes the progress made towards defining, designing, and developing the hardware and software segments of the airborne, optical remote methane and ethane sensor. The most challenging task to date has been to identify a vendor capable of designing and developing a light source with the appropriate output wavelength and power. This report will document the work that has been done to identify design requirements, and potential vendors for the light source. Significant progress has also been made in characterizing the amount of light return available from a remote target at various distances from the light source. A great deal of time has been spent conducting laboratory and long-optical path target reflectance measurements. This is important since it helps to establish the overall optical output requirements for the sensor. It also reduces the relative uncertainty and risk associated with developing a custom light source. The data gathered from the optical path testing has been translated to the airborne transceiver design in such areas as: fiber coupling, optical detector selection, gas filters, and software analysis. Ophir will next, summarize the design progress of the transceiver hardware and software development. Finally, Ophir will discuss remaining project issues that may impact the success of the project.

Extractive Sampling and Optical Remote Sensing of F-100 Aircraft Engine Emissions (PREPRINT)

National Research Council Canada - National Science Library

Cowen, Kenneth; Goodwin, Bradley; Satola, Jan; Kagann, Robert; Hashmonay, Ram; Spicer, Chester; Holdren, Michael; Mayfield, Howard T

2008-01-01

... from military aircraft, in order to meet increasingly stringent regulatory requirements. This paper describes the results of a recent field study using extractive and optical remote sensing (ORS...

Optical Remote Sensing Algorithm Validation using High-Frequency Underway Biogeochemical Measurements in Three Large Global River Systems

Science.gov (United States)

Kuhn, C.; Richey, J. E.; Striegl, R. G.; Ward, N.; Sawakuchi, H. O.; Crawford, J.; Loken, L. C.; Stadler, P.; Dornblaser, M.; Butman, D. E.

2017-12-01

More than 93% of the world's river-water volume occurs in basins impacted by large dams and about 43% of river water discharge is impacted by flow regulation. Human land use also alters nutrient and carbon cycling and the emission of carbon dioxide from inland reservoirs. Increased water residence times and warmer temperatures in reservoirs fundamentally alter the physical settings for biogeochemical processing in large rivers, yet river biogeochemistry for many large systems remains undersampled. Satellite remote sensing holds promise as a methodology for responsive regional and global water resources management. Decades of ocean optics research has laid the foundation for the use of remote sensing reflectance in optical wavelengths (400 - 700 nm) to produce satellite-derived, near-surface estimates of phytoplankton chlorophyll concentration. Significant improvements between successive generations of ocean color sensors have enabled the scientific community to document changes in global ocean productivity (NPP) and estimate ocean biomass with increasing accuracy. Despite large advances in ocean optics, application of optical methods to inland waters has been limited to date due to their optical complexity and small spatial scale. To test this frontier, we present a study evaluating the accuracy and suitability of empirical inversion approaches for estimating chlorophyll-a, turbidity and temperature for the Amazon, Columbia and Mississippi rivers using satellite remote sensing. We demonstrate how riverine biogeochemical measurements collected at high frequencies from underway vessels can be used as in situ matchups to evaluate remotely-sensed, near-surface temperature, turbidity, chlorophyll-a derived from the Landsat 8 (NASA) and Sentinel 2 (ESA) satellites. We investigate the use of remote sensing water reflectance to infer trophic status as well as tributary influences on the optical characteristics of the Amazon, Mississippi and Columbia rivers.

Toward green next-generation passive optical networks

Science.gov (United States)

Srivastava, Anand

2015-01-01

Energy efficiency has become an increasingly important aspect of designing access networks, due to both increased concerns for global warming and increased network costs related to energy consumption. Comparing access, metro, and core, the access constitutes a substantial part of the per subscriber network energy consumption and is regarded as the bottleneck for increased network energy efficiency. One of the main opportunities for reducing network energy consumption lies in efficiency improvements of the customer premises equipment. Access networks in general are designed for low utilization while supporting high peak access rates. The combination of large contribution to overall network power consumption and low Utilization implies large potential for CPE power saving modes where functionality is powered off during periods of idleness. Next-generation passive optical network, which is considered one of the most promising optical access networks, has notably matured in the past few years and is envisioned to massively evolve in the near future. This trend will increase the power requirements of NG-PON and make it no longer coveted. This paper will first provide a comprehensive survey of the previously reported studies on tackling this problem. A novel solution framework is then introduced, which aims to explore the maximum design dimensions and achieve the best possible power saving while maintaining the QoS requirements for each type of service.

Internet Group Management Protocol for IPTV Services in Passive Optical Network

Science.gov (United States)

Lee, Eunjo; Park, Sungkwon

We propose a new Internet group management protocol (IGMP) which can be used in passive optical network (PON) especially for IPTV services which dramatically reduces the channel change response time caused by traditional IGMP. In this paper, the newly proposed IGMP is introduced in detail and performance analysis is also included. Simulation results demonstrated the performance of the newly proposed IGMP, whereby, viewers can watch the shared IPTV channels without the channel change response time when channel request reaches a threshold.

An empirical InSAR-optical fusion approach to mapping vegetation canopy height

Science.gov (United States)

Wayne S. Walker; Josef M. Kellndorfer; Elizabeth LaPoint; Michael Hoppus; James Westfall

2007-01-01

Exploiting synergies afforded by a host of recently available national-scale data sets derived from interferometric synthetic aperture radar (InSAR) and passive optical remote sensing, this paper describes the development of a novel empirical approach for the provision of regional- to continental-scale estimates of vegetation canopy height. Supported by data from the...

Tunnel-Site Selection by Remote Sensing Techniques

Science.gov (United States)

A study of the role of remote sensing for geologic reconnaissance for tunnel-site selection was commenced. For this study, remote sensing was defined...conventional remote sensing . Future research directions are suggested, and the extension of remote sensing to include airborne passive microwave

Optical Remote Sensing of Electric Fields Above Thunderstorms

Science.gov (United States)

Burns, B. M.; Carlson, B. E.; Lauben, D.; Cohen, M.; Smith, D.; Inan, U. S.

2010-12-01

Measurement of thunderstorm electric fields typically require balloon-borne measurements in the region of interest. Such measurements are cumbersome and provide limited information at a single point. Remote sensing of electric fields by Kerr-effect induced optical polarization changes of background skylight circumvents many of these difficulties and can in principle provide a high-speed movie of electric field behavior. Above-thundercloud 100 kV/m quasi-static electric fields are predicted to produce polarization changes at above the part in one million level that should be detectable at a ground instrument featuring 1 cm2sr geometric factor and 1 kHz bandwidth (though more sensitivity is nonetheless desired). Currently available optical and electronic components may meet these requirements. We review the principles of this measurement and discuss the current status of a field-ready prototype instrument currently in construction.

Next generation passive optical networks based on orthogonal frequency division multiplexing techniques

OpenAIRE

Escayola Elias, Francesc Xavier

2015-01-01

In recent decades, the industry of communications has acquired huge significance, and nowadays constitutes an essential tool for the society information. Thus, the exponential growth in demand of broadband services and the increasing amount of information to be transmitted have spurred the evolution of the access network infrastructure to effectively meet the user needs in an effective way in terms of costs of both installation and maintenance. Passive optical networks (PON) are current...

On the passive probing of fiber optic quantum communication channels

International Nuclear Information System (INIS)

Korol'kov, A. V.; Katamadze, K. G.; Kulik, S. P.; Molotkov, S. N.

2010-01-01

Avalanche photodetectors based on InGaAs:P are the most sensitive and only detectors operating in the telecommunication wavelength range 1.30-1.55 μm in the fiber optic quantum cryptography systems that can operate in the single photon count mode. In contrast to the widely used silicon photodetectors for wavelengths up to 1 μm operating in a waiting mode, these detectors always operate in a gated mode. The production of an electron-hole pair in the process of the absorption of a photon and the subsequent appearance of an avalanche of carriers can be accompanied by the inverse processes of the recombination and emission of photons. Such a backward emission can present a potential serious problem for the stability of fiber optic quantum cryptography systems against passive probing. The results of analyzing the detection of backscattered radiation are reported. The probability of such an emission has been estimated.

Passive Optical Networks for the Distribution of Timed Signals in Particle Physics Experiments

CERN Document Server

Papakonstantinou, I; Papadopoulos,S; Troska, J; Vasey, F; Baron, S; Santos, L; Silva, S; Stejskal, P; Sigaud, C; Detraz, S; Moreira, P; Darwazeh, I

2009-01-01

A passive optical network for timing distribution applications based on FPGAs has been successfully demonstrated. Deterministic latency was achieved in the critical downstream direction where triggers are distributed while a burst mode receiver was successfully implemented in the upstream direction. Finally, a simple and efficient protocol was introduced for the communication between the OLT and the ONUs in the network that maximizes bandwidth utilization.

Improvement of robustness of optical see-through AR for a remote maintenance support system

International Nuclear Information System (INIS)

Nagamatsu, Takashi; Kaieda, Yohei; Kitagawa, Yuki; Shimada, Hiroyuki; Otsuji, Tomoo; Yoshikawa, Hidekazu

2005-01-01

A remote maintenance support system using optical see-through AR has been developed to keep safety and reliability in preparation for old experts' retirement. It enables plant workers to collaborate with a remote expert (supervisor) by using a wearable computer, an optical see-through AR (Augmented Reality) technology and eye-gaze information. The optical see-through AR enables a user to see the real world through a transparent display and it contributes to keeping safety of plant workers and acquiring detail information of machines. On the contrary, the registration between computer-generated objects and the real world is difficult, so we developed a method to correct the geometrical consistency for practical use of optical see-through AR. The developed method has two steps: (1) detection of the shift amount of HMD by the eye camera image and (2) adjustment of the display position on the HMD screen. This method made it possible to allow user's moving and physical shift of HMD, so it is capable of wide application to practical works

Estimating forest and woodland aboveground biomass using active and passive remote sensing

Science.gov (United States)

Wu, Zhuoting; Dye, Dennis G.; Vogel, John M.; Middleton, Barry R.

2016-01-01

Aboveground biomass was estimated from active and passive remote sensing sources, including airborne lidar and Landsat-8 satellites, in an eastern Arizona (USA) study area comprised of forest and woodland ecosystems. Compared to field measurements, airborne lidar enabled direct estimation of individual tree height with a slope of 0.98 (R2 = 0.98). At the plot-level, lidar-derived height and intensity metrics provided the most robust estimate for aboveground biomass, producing dominant species-based aboveground models with errors ranging from 4 to 14Mg ha –1 across all woodland and forest species. Landsat-8 imagery produced dominant species-based aboveground biomass models with errors ranging from 10 to 28 Mg ha –1. Thus, airborne lidar allowed for estimates for fine-scale aboveground biomass mapping with low uncertainty, while Landsat-8 seems best suited for broader spatial scale products such as a national biomass essential climate variable (ECV) based on land cover types for the United States.

Physical-layer network coding for passive optical interconnect in datacenter networks.

Science.gov (United States)

Lin, Rui; Cheng, Yuxin; Guan, Xun; Tang, Ming; Liu, Deming; Chan, Chun-Kit; Chen, Jiajia

2017-07-24

We introduce physical-layer network coding (PLNC) technique in a passive optical interconnect (POI) architecture for datacenter networks. The implementation of the PLNC in the POI at 2.5 Gb/s and 10Gb/s have been experimentally validated while the gains in terms of network layer performances have been investigated by simulation. The results reveal that in order to realize negligible packet drop, the wavelengths usage can be reduced by half while a significant improvement in packet delay especially under high traffic load can be achieved by employing PLNC over POI.

Development of a passive and remote magnetic microsensor with thin-film giant magnetoimpedance element and surface acoustic wave transponder

KAUST Repository

Al Rowais, Hommood; Li, Bodong; Liang, Cai; Green, Scott Ryan; Gianchandani, Yogesh B.; Kosel, Jü rgen

2011-01-01

This paper presents the development of a wireless magnetic field sensor consisting of a three-layer thin-film giant magnetoimpedance sensor and a surface acoustic wave device on one substrate. The goal of this integration is a passive and remotely interrogated sensor that can be easily mass fabricated using standard microfabrication tools. The design parameters, fabrication process, and a model of the integrated sensor are presented together with experimental results of the sensor. © 2011 American Institute of Physics.

Chip-integrated optical power limiter based on an all-passive micro-ring resonator

Science.gov (United States)

Yan, Siqi; Dong, Jianji; Zheng, Aoling; Zhang, Xinliang

2014-10-01

Recent progress in silicon nanophotonics has dramatically advanced the possible realization of large-scale on-chip optical interconnects integration. Adopting photons as information carriers can break the performance bottleneck of electronic integrated circuit such as serious thermal losses and poor process rates. However, in integrated photonics circuits, few reported work can impose an upper limit of optical power therefore prevent the optical device from harm caused by high power. In this study, we experimentally demonstrate a feasible integrated scheme based on a single all-passive micro-ring resonator to realize the optical power limitation which has a similar function of current limiting circuit in electronics. Besides, we analyze the performance of optical power limiter at various signal bit rates. The results show that the proposed device can limit the signal power effectively at a bit rate up to 20 Gbit/s without deteriorating the signal. Meanwhile, this ultra-compact silicon device can be completely compatible with the electronic technology (typically complementary metal-oxide semiconductor technology), which may pave the way of very large scale integrated photonic circuits for all-optical information processors and artificial intelligence systems.

Final Report: Laser-Based Optical Trap for Remote Sampling of Interplanetary and Atmospheric Particulate Matter

Science.gov (United States)

Stysley, Paul

2016-01-01

Applicability to Early Stage Innovation NIAC Cutting edge and innovative technologies are needed to achieve the demanding requirements for NASA origin missions that require sample collection as laid out in the NRC Decadal Survey. This proposal focused on fully understanding the state of remote laser optical trapping techniques for capturing particles and returning them to a target site. In future missions, a laser-based optical trapping system could be deployed on a lander that would then target particles in the lower atmosphere and deliver them to the main instrument for analysis, providing remote access to otherwise inaccessible samples. Alternatively, for a planetary mission the laser could combine ablation and trapping capabilities on targets typically too far away or too hard for traditional drilling sampling systems. For an interstellar mission, a remote laser system could gather particles continuously at a safe distance; this would avoid the necessity of having a spacecraft fly through a target cloud such as a comet tail. If properly designed and implemented, a laser-based optical trapping system could fundamentally change the way scientists designand implement NASA missions that require mass spectroscopy and particle collection.

Using optical remote sensing techniques to track the development of ozone-induced stress

Energy Technology Data Exchange (ETDEWEB)

Meroni, Michele, E-mail: michele.meroni@unimib.i [Remote Sensing of Environmental Dynamics Laboratory, DISAT, University of Milan-Bicocca, Piazza della Scienza, 1, 20126 Milan (Italy); Panigada, Cinzia; Rossini, Micol [Remote Sensing of Environmental Dynamics Laboratory, DISAT, University of Milan-Bicocca, Piazza della Scienza, 1, 20126 Milan (Italy); Picchi, Valentina [CNR, Plant Virology Institute, Milan Unit, Milan (Italy); Department of Tree Science, Entomology and Plant Pathology ' G. Scaramuzzi' , University of Pisa, Pisa (Italy); Cogliati, Sergio; Colombo, Roberto [Remote Sensing of Environmental Dynamics Laboratory, DISAT, University of Milan-Bicocca, Piazza della Scienza, 1, 20126 Milan (Italy)

2009-05-15

In this paper, a literature review about optical remote sensing (RS) of O{sub 3} stress is presented. Studies on O{sub 3}-induced effects on vegetation reflectance have been conducted since late '70s based on the analysis of optical RS data. Literature review reveals that traditional RS techniques were able to detect changes in leaf and canopy reflectance related to O{sub 3}-induced stress when visible symptoms already occurred. Only recently, advanced RS techniques using hyperspectral sensors, demonstrated the feasibility of detecting the stress in its early phase by monitoring excess energy dissipation pathways such as chlorophyll fluorescence and non-photochemical quenching (NPQ). Steady-state fluorescence (Fs), measured by exploiting the Fraunhofer line depth principle and NPQ related xanthophyll-cycle, estimated through the photochemical reflectance index (PRI) responded to O{sub 3} fumigation before visible symptoms occurred. This opens up new possibilities for the early detection of vegetation O{sub 3} stress by means of hyperspectral RS. - Possibilities for the early detection of vegetation O{sub 3} stress by means of optical remote sensing are discussed.

Using optical remote sensing techniques to track the development of ozone-induced stress

International Nuclear Information System (INIS)

Meroni, Michele; Panigada, Cinzia; Rossini, Micol; Picchi, Valentina; Cogliati, Sergio; Colombo, Roberto

2009-01-01

In this paper, a literature review about optical remote sensing (RS) of O 3 stress is presented. Studies on O 3 -induced effects on vegetation reflectance have been conducted since late '70s based on the analysis of optical RS data. Literature review reveals that traditional RS techniques were able to detect changes in leaf and canopy reflectance related to O 3 -induced stress when visible symptoms already occurred. Only recently, advanced RS techniques using hyperspectral sensors, demonstrated the feasibility of detecting the stress in its early phase by monitoring excess energy dissipation pathways such as chlorophyll fluorescence and non-photochemical quenching (NPQ). Steady-state fluorescence (Fs), measured by exploiting the Fraunhofer line depth principle and NPQ related xanthophyll-cycle, estimated through the photochemical reflectance index (PRI) responded to O 3 fumigation before visible symptoms occurred. This opens up new possibilities for the early detection of vegetation O 3 stress by means of hyperspectral RS. - Possibilities for the early detection of vegetation O 3 stress by means of optical remote sensing are discussed.

Remote spectrometry with optical fibers, ten years of development and prospects for on-line control

International Nuclear Information System (INIS)

Boisde, G.; Perez, J.J.

1984-09-01

This paper describes, with examples uranium and plutonium spectra, how optical fibers have raised new concepts in spectrometry, such as the internal spectral reference, instantaneous measurements on the sides of the absorption spectra, and the modelling of spectral variations. With optical fibers, original technical solutions are used for remote chemical analysis

Vertical‐cavity surface‐emitting laser based digital coherent detection for multigigabit long reach passive optical links

DEFF Research Database (Denmark)

Rodes Lopez, Roberto; Jensen, Jesper Bevensee; Zibar, Darko

2011-01-01

We report on experimental demonstration of digital coherent detection based on a directly modulated vertical‐cavity surface‐emitting laser with bit rate up to 10 Gbps. This system allows a cooler‐less, free running, and unamplified transmission without optical dispersion compensation up to 105 km...... at 5 Gbps long reach passive optical links. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:2462–2464, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26331...

Applications of optical fiber to the remote fluorescence analysis

International Nuclear Information System (INIS)

Shin, Jang Soo; Kim, Duck Hueon; Lee, Soo Ho

1992-12-01

The laser fluorometer developed in 1987 has been used in real circumstances for trace uranium analysis. And, we have been trying to improve the instrument to be able to apply in analytical circumstances of remote measurement using optical fiber. The N 2 laser beam and the resulting fluorescence light could be successfully transmitted through a quartz-made optical fiber. The wavelength resolution and the fluorescence decay time resolution induced by pulsed N 2 laser were used to the uranium fluorescence analyses. The fluorescence of uranium in nitric acid medium was measured successfully using the system. The fluorescence signal was analysed using simplex method which is useful to deconvolute the mixed signals. An analytical method using thermal lens effect was developed. The method will be a complementary one for the fluorescence measurement. (Author)

Retrieving Leaf Area Index (LAI) Using Remote Sensing: Theories, Methods and Sensors.

Science.gov (United States)

Zheng, Guang; Moskal, L Monika

2009-01-01

The ability to accurately and rapidly acquire leaf area index (LAI) is an indispensable component of process-based ecological research facilitating the understanding of gas-vegetation exchange phenomenon at an array of spatial scales from the leaf to the landscape. However, LAI is difficult to directly acquire for large spatial extents due to its time consuming and work intensive nature. Such efforts have been significantly improved by the emergence of optical and active remote sensing techniques. This paper reviews the definitions and theories of LAI measurement with respect to direct and indirect methods. Then, the methodologies for LAI retrieval with regard to the characteristics of a range of remotely sensed datasets are discussed. Remote sensing indirect methods are subdivided into two categories of passive and active remote sensing, which are further categorized as terrestrial, aerial and satellite-born platforms. Due to a wide variety in spatial resolution of remotely sensed data and the requirements of ecological modeling, the scaling issue of LAI is discussed and special consideration is given to extrapolation of measurement to landscape and regional levels.

SciLab Based Remote Control of Thermo-Optical Plant

Directory of Open Access Journals (Sweden)

Miroslav Jano

2011-11-01

Full Text Available The paper deals with the web-based implementation of the control system of a thermo-optical plant. The control of the plant is based on the SciLab software which originally is not designed for web-based applications. The paper shows a possible way to circumvent this limitation. The ultimate goal is to enable remote controlled experiment using SciLab. The paper also describes possible tools for communication and control of the real plant and visualization of results.

Remote measurement of microwave distribution based on optical detection

Energy Technology Data Exchange (ETDEWEB)

Ji, Zhong; Ding, Wenzheng; Yang, Sihua; Chen, Qun, E-mail: redrocks-chenqun@hotmail.com, E-mail: xingda@scnu.edu.cn; Xing, Da, E-mail: redrocks-chenqun@hotmail.com, E-mail: xingda@scnu.edu.cn [MOE Key Laboratory of Laser Life Science and Institute of Laser Life Science, South China Normal University, Guangzhou 510631 (China)

2016-01-04

In this letter, we present the development of a remote microwave measurement system. This method employs an arc discharge lamp that serves as an energy converter from microwave to visible light, which can propagate without transmission medium. Observed with a charge coupled device, quantitative microwave power distribution can be achieved when the operators and electronic instruments are in a distance from the high power region in order to reduce the potential risk. We perform the experiments using pulsed microwaves, and the results show that the system response is dependent on the microwave intensity over a certain range. Most importantly, the microwave distribution can be monitored in real time by optical observation of the response of a one-dimensional lamp array. The characteristics of low cost, a wide detection bandwidth, remote measurement, and room temperature operation make the system a preferred detector for microwave applications.

Remote measurement of high preeruptive water vapor emissions at Sabancaya volcano by passive differential optical absorption spectroscopy

Science.gov (United States)

Kern, Christoph; Masias, Pablo; Apaza, Fredy; Reath, Kevin; Platt, Ulrich

2017-01-01

Water (H2O) is by far the most abundant volcanic volatile species and plays a predominant role in driving volcanic eruptions. However, numerous difficulties associated with making accurate measurements of water vapor in volcanic plumes have limited their use as a diagnostic tool. Here we present the first detection of water vapor in a volcanic plume using passive visible-light differential optical absorption spectroscopy (DOAS). Ultraviolet and visible-light DOAS measurements were made on 21 May 2016 at Sabancaya Volcano, Peru. We find that Sabancaya's plume contained an exceptionally high relative water vapor abundance 6 months prior to its November 2016 eruption. Our measurements yielded average sulfur dioxide (SO2) emission rates of 800–900 t/d, H2O emission rates of around 250,000 t/d, and an H2O/SO2 molecular ratio of 1000 which is about an order of magnitude larger than typically found in high-temperature volcanic gases. We attribute the high water vapor emissions to a boiling-off of Sabancaya's hydrothermal system caused by intrusion of magma to shallow depths. This hypothesis is supported by a significant increase in the thermal output of the volcanic edifice detected in infrared satellite imagery leading up to and after our measurements. Though the measurement conditions encountered at Sabancaya were very favorable for our experiment, we show that visible-light DOAS systems could be used to measure water vapor emissions at numerous other high-elevation volcanoes. Such measurements would provide observatories with additional information particularly useful for forecasting eruptions at volcanoes harboring significant hydrothermal systems.

Variations in global land surface phenology: a comparison of satellite optical and passive microwave data

Science.gov (United States)

Tong, X.; Tian, F.; Brandt, M.; Zhang, W.; Liu, Y.; Fensholt, R.

2017-12-01

Changes in vegetation phenological events are among the most sensitive biological responses to climate change. In last decades, facilitating by satellite remote sensing techniques, land surface phenology (LSP) have been monitored at global scale using proxy approaches as tracking the temporal change of a satellite-derived vegetation index. However, the existing global assessments of changes in LSP are all established on the basis of leaf phenology using NDVI derived from optical sensors, being responsive to vegetation canopy cover and greenness. Instead, the vegetation optical depth (VOD) parameter from passive microwave sensors, which is sensitive to the aboveground vegetation water content by including as well the woody components in the observations, provides an alternative, independent and comprehensive means for global vegetation phenology monitoring. We used the unique long-term global VOD record available for the period 1992-2012 to monitoring the dynamics of LSP metrics (length of season, start of season and end of season) in comparison with the dynamics of LSP metrics derived from the latest GIMMS NDVI3G V1. We evaluated the differences in the linear trends of LSP metrics between two datasets. Currently, our results suggest that the level of seasonality variation of vegetation water content is less than the vegetation greenness. We found significant phenological changes in vegetation water content in African woodlands, where has been reported with little leaf phenological change regardless of the delays in rainfall onset. Therefore, VOD might allow us to detect temporal shifts in the timing difference of vegetation water storage vs. leaf emergence and to see if some ecophysiological thresholds seem to be reached, that could cause species turnover as climate change-driven alterations to the African monsoon proceed.

Polarization-insensitive all-optical dual pump-phase transmultiplexing from 2 x 10-GBd OOKs to 10-GBd RZ-QPSK using cross-phase modulation in a passive nonlinear birefringent photonic crystal fiber

Science.gov (United States)

Mahmood, Tanvir

Considering the network size, bit rate, spectral and channel capacity limitations, different modulation formats may be selectively used in future optical networks. Although the traditional metropolitan area networks (MANs) still uses the non-return-to-zero on-off keying (NRZ-OOK) modulation format due to its technical simplicity and therefore low cost, QPSK format is more advantageous in spectrally efficient long-haul fiber optic transmission systems because of its constant power envelope, and robustness to various transmission impairments. Consequently, an important problem may arise, in particular how to route the OOK-data streams from MANs to long-haul backbone networks when the state of polarization (SOP) of the remotely generated OOK is unpredictable. Hence, the focus of this dissertation was to investigate a polarization insensitive (PI) all-optical nonlinear optical signal processing (NOSP) method that can be implemented at the network cross-connect (X-connect) to transfer data from a remotely and a locally generated OOK data simultaneously to more effectual QPSK format for long-haul transmission. By utilizing cross-phase modulation (XPM) and inherent birefringence of the device, the work demonstrated, for the first time, PI all-optical data transfer utilizing dual pump-phase transmultiplexing (DPTM) from 2 x 10-GBd OOKs to 10-GBd RZ-QPSK in a passive nonlinear birefringent photonic crystal fiber (PCF). Polarization insensitivity was achieved by scrambling the SOP of the remotely generated OOK pump and launching the locally generated OOK pump and the probe off-axis. To mitigate polarization induced power fluctuations and detrimental effects due to nearby partially degenerate and non-degenerate four wave mixings, an optimum pump-probe detuning was also utilized. The PI DPTM RZ-QPSK demonstrated a pre-amplified receiver sensitivity penalty < 5.5 dB at 10--9 bit-error-rate (BER), relative to relative to the FPGA-precoded RZ-DQPSK baseline in ASE

REMOTE SENSING IN OCEANOGRAPHY.

Science.gov (United States)

remote sensing from satellites. Sensing of oceanographic variables from aircraft began with the photographing of waves and ice. Since then remote measurement of sea surface temperatures and wave heights have become routine. Sensors tested for oceanographic applications include multi-band color cameras, radar scatterometers, infrared spectrometers and scanners, passive microwave radiometers, and radar imagers. Remote sensing has found its greatest application in providing rapid coverage of large oceanographic areas for synoptic and analysis and

On-Board, Real-Time Preprocessing System for Optical Remote-Sensing Imagery.

Science.gov (United States)

Qi, Baogui; Shi, Hao; Zhuang, Yin; Chen, He; Chen, Liang

2018-04-25

With the development of remote-sensing technology, optical remote-sensing imagery processing has played an important role in many application fields, such as geological exploration and natural disaster prevention. However, relative radiation correction and geometric correction are key steps in preprocessing because raw image data without preprocessing will cause poor performance during application. Traditionally, remote-sensing data are downlinked to the ground station, preprocessed, and distributed to users. This process generates long delays, which is a major bottleneck in real-time applications for remote-sensing data. Therefore, on-board, real-time image preprocessing is greatly desired. In this paper, a real-time processing architecture for on-board imagery preprocessing is proposed. First, a hierarchical optimization and mapping method is proposed to realize the preprocessing algorithm in a hardware structure, which can effectively reduce the computation burden of on-board processing. Second, a co-processing system using a field-programmable gate array (FPGA) and a digital signal processor (DSP; altogether, FPGA-DSP) based on optimization is designed to realize real-time preprocessing. The experimental results demonstrate the potential application of our system to an on-board processor, for which resources and power consumption are limited.

On-Board, Real-Time Preprocessing System for Optical Remote-Sensing Imagery

Science.gov (United States)

Qi, Baogui; Zhuang, Yin; Chen, He; Chen, Liang

2018-01-01

With the development of remote-sensing technology, optical remote-sensing imagery processing has played an important role in many application fields, such as geological exploration and natural disaster prevention. However, relative radiation correction and geometric correction are key steps in preprocessing because raw image data without preprocessing will cause poor performance during application. Traditionally, remote-sensing data are downlinked to the ground station, preprocessed, and distributed to users. This process generates long delays, which is a major bottleneck in real-time applications for remote-sensing data. Therefore, on-board, real-time image preprocessing is greatly desired. In this paper, a real-time processing architecture for on-board imagery preprocessing is proposed. First, a hierarchical optimization and mapping method is proposed to realize the preprocessing algorithm in a hardware structure, which can effectively reduce the computation burden of on-board processing. Second, a co-processing system using a field-programmable gate array (FPGA) and a digital signal processor (DSP; altogether, FPGA-DSP) based on optimization is designed to realize real-time preprocessing. The experimental results demonstrate the potential application of our system to an on-board processor, for which resources and power consumption are limited. PMID:29693585

Optical fibers for remote spectrometry of alkali elements in the dc arc

International Nuclear Information System (INIS)

Faires, L.M.; Bieniewski, T.M.; Apel, C.T.; Niemczyk, T.M.

1985-01-01

An optical fiber cable is designed, characterized, and applied to the remote spectrometric analysis of alkali elements as impurities in plutonium by dc arc emission. The analytical performance of the dc arc/optical fiber/polychromator system is tested by the establishment of analytical working curves for sodium, potassium, and rubidium from a set of standards. Accuracy, determined by the use of control samples of known concentration, is found to be 10% or better. The new analytical system provides improvement in both accuracy and efficiency compared to the previously used spectrographic technique

AIRBORNE, OPTICAL REMOTE SENSNG OF METHANE AND ETHANE FOR NATURAL GAS PIPELINE LEAK DETECTION

Energy Technology Data Exchange (ETDEWEB)

Jerry Myers

2005-04-15

Ophir Corporation was awarded a contract by the U. S. Department of Energy, National Energy Technology Laboratory under the Project Title ''Airborne, Optical Remote Sensing of Methane and Ethane for Natural Gas Pipeline Leak Detection'' on October 14, 2002. The scope of the work involved designing and developing an airborne, optical remote sensor capable of sensing methane and, if possible, ethane for the detection of natural gas pipeline leaks. Flight testing using a custom dual wavelength, high power fiber amplifier was initiated in February 2005. Ophir successfully demonstrated the airborne system, showing that it was capable of discerning small amounts of methane from a simulated pipeline leak. Leak rates as low as 150 standard cubic feet per hour (scf/h) were detected by the airborne sensor.

The passive optical properties of a silicon nanoparticle-embedded benzocyclobutene polymer waveguide

International Nuclear Information System (INIS)

Chiu, J.-J.; Perng, Tsong P

2008-01-01

The passive optical properties of a silicon nanoparticle-embedded benzocyclobutene (BCB) waveguide were investigated. The silicon nanoparticles, of a size varying from 6 to 25 nm, were prepared by vapor condensation. The transmission modes and losses were examined by the prism coupler and cut-back methods. A He-Ne laser beam with a wavelength of 6328 A was used to measure the effective index and thickness of the waveguide. Laser light could be efficiently coupled into the BCB waveguide when the embedded Si nanoparticles were smaller than 6 nm. The film thickness and effective index of the Si-embedded BCB waveguide were measured to be 1.825 μm and 1.565, respectively. The optical transmission losses of the pure BCB and Si-embedded ridge waveguides measured by the cut-back method were 0.85 and 1.63 dB cm -1 , respectively. Although the optical loss was increased by the embedded Si, the disturbance of the output contour was quite small. This result demonstrates that the nanoparticle-embedded polymer waveguide may be used for optoelectronic integrated circuits

Energy-saving framework for passive optical networks with ONU sleep/doze mode.

Science.gov (United States)

Van, Dung Pham; Valcarenghi, Luca; Dias, Maluge Pubuduni Imali; Kondepu, Koteswararao; Castoldi, Piero; Wong, Elaine

2015-02-09

This paper proposes an energy-saving passive optical network framework (ESPON) that aims to incorporate optical network unit (ONU) sleep/doze mode into dynamic bandwidth allocation (DBA) algorithms to reduce ONU energy consumption. In the ESPON, the optical line terminal (OLT) schedules both downstream (DS) and upstream (US) transmissions in the same slot in an online and dynamic fashion whereas the ONU enters sleep mode outside the slot. The ONU sleep time is maximized based on both DS and US traffic. Moreover, during the slot, the ONU might enter doze mode when only its transmitter is idle to further improve energy efficiency. The scheduling order of data transmission, control message exchange, sleep period, and doze period defines an energy-efficient scheme under the ESPON. Three schemes are designed and evaluated in an extensive FPGA-based evaluation. Results show that whilst all the schemes significantly save ONU energy for different evaluation scenarios, the scheduling order has great impact on their performance. In addition, the ESPON allows for a scheduling order that saves ONU energy independently of the network reach.

Meta-Analysis of the Detection of Plant Pigment Concentrations Using Hyperspectral Remotely Sensed Data

Science.gov (United States)

Huang, Jingfeng; Wei, Chen; Zhang, Yao; Blackburn, George Alan; Wang, Xiuzhen; Wei, Chuanwen; Wang, Jing

2015-01-01

Passive optical hyperspectral remote sensing of plant pigments offers potential for understanding plant ecophysiological processes across a range of spatial scales. Following a number of decades of research in this field, this paper undertakes a systematic meta-analysis of 85 articles to determine whether passive optical hyperspectral remote sensing techniques are sufficiently well developed to quantify individual plant pigments, which operational solutions are available for wider plant science and the areas which now require greater focus. The findings indicate that predictive relationships are strong for all pigments at the leaf scale but these decrease and become more variable across pigment types at the canopy and landscape scales. At leaf scale it is clear that specific sets of optimal wavelengths can be recommended for operational methodologies: total chlorophyll and chlorophyll a quantification is based on reflectance in the green (550–560nm) and red edge (680–750nm) regions; chlorophyll b on the red, (630–660nm), red edge (670–710nm) and the near-infrared (800–810nm); carotenoids on the 500–580nm region; and anthocyanins on the green (550–560nm), red edge (700–710nm) and near-infrared (780–790nm). For total chlorophyll the optimal wavelengths are valid across canopy and landscape scales and there is some evidence that the same applies for chlorophyll a. PMID:26356842

Meta-Analysis of the Detection of Plant Pigment Concentrations Using Hyperspectral Remotely Sensed Data.

Directory of Open Access Journals (Sweden)

Jingfeng Huang

Full Text Available Passive optical hyperspectral remote sensing of plant pigments offers potential for understanding plant ecophysiological processes across a range of spatial scales. Following a number of decades of research in this field, this paper undertakes a systematic meta-analysis of 85 articles to determine whether passive optical hyperspectral remote sensing techniques are sufficiently well developed to quantify individual plant pigments, which operational solutions are available for wider plant science and the areas which now require greater focus. The findings indicate that predictive relationships are strong for all pigments at the leaf scale but these decrease and become more variable across pigment types at the canopy and landscape scales. At leaf scale it is clear that specific sets of optimal wavelengths can be recommended for operational methodologies: total chlorophyll and chlorophyll a quantification is based on reflectance in the green (550-560nm and red edge (680-750nm regions; chlorophyll b on the red, (630-660nm, red edge (670-710nm and the near-infrared (800-810nm; carotenoids on the 500-580nm region; and anthocyanins on the green (550-560nm, red edge (700-710nm and near-infrared (780-790nm. For total chlorophyll the optimal wavelengths are valid across canopy and landscape scales and there is some evidence that the same applies for chlorophyll a.

Simplified Fiber-Wireless Distribution of HD Video in Passive and Active W-band Close Proximity Terminals

DEFF Research Database (Denmark)

Lebedev, Alexander; Rodes Lopez, Roberto; Yu, Xianbin

2012-01-01

We experimentally demonstrate uncompressed high-definition (HD) video distribution at 84 GHz Radio over Fiber link achieving up to 3 meters of wireless transmission. We experimentally emulate Metro-Access architecture by deploying single/multimode fibers. Passive and active approaches for remote...... antenna unit (RAU) are experimentally investigated. The bit error rate (BER) performance of the optical and wireless channels is reported. A successful transmission of uncompressed HD video in the W-band wireless channel is demonstrated with prospects to pave the way for application-focused fiber-wireless...

Determining the Scattering Properties of Vertically-Structured Nepheloid Layers From the Fusion of Active and Passive Optical Sensors

National Research Council Canada - National Science Library

Bissett, W. P; Kohler, David D

2006-01-01

... from the bottom back toward the surface. The net result is that these layers reduce the ability of active and passive optical instruments to retrieve estimates of bathymetry and bottom classification, as well as reduce the abilities...

Remote Spectroscopy in the Visible Using Fibers on the Optical Internet Network

Science.gov (United States)

Ribeiro, Rafael A. S.; de Oliveira, Anderson R.; Zilio, Sergio C.

2010-01-01

The work presented here demonstrates the feasibility of using the single-mode fibers of an optical Internet network to deliver visible light between separate laboratories as a way to perform remote spectroscopy in the visible for teaching purposes. The coupling of a broadband light source into the single-mode fiber (SMF) and the characterization…

Twenty-four year record of Northern Hemisphere snow cover derived from passive microwave remote sensing

Science.gov (United States)

Armstrong, Richard L.; Brodzik, Mary Jo

2003-04-01

Snow cover is an important variable for climate and hydrologic models due to its effects on energy and moisture budgets. Seasonal snow can cover more than 50% of the Northern Hemisphere land surface during the winter resulting in snow cover being the land surface characteristic responsible for the largest annual and interannual differences in albedo. Passive microwave satellite remote sensing can augment measurements based on visible satellite data alone because of the ability to acquire data through most clouds or during darkness as well as to provide a measure of snow depth or water equivalent. It is now possible to monitor the global fluctuation of snow cover over a 24 year period using passive microwave data (Scanning Multichannel Microwave Radiometer (SMMR) 1978-1987 and Special Sensor Microwave/Imager (SSM/I), 1987-present). Evaluation of snow extent derived from passive microwave algorithms is presented through comparison with the NOAA Northern Hemisphere snow extent data. For the period 1978 to 2002, both passive microwave and visible data sets show a smiliar pattern of inter-annual variability, although the maximum snow extents derived from the microwave data are consistently less than those provided by the visible statellite data and the visible data typically show higher monthly variability. During shallow snow conditions of the early winter season microwave data consistently indicate less snow-covered area than the visible data. This underestimate of snow extent results from the fact that shallow snow cover (less than about 5.0 cm) does not provide a scattering signal of sufficient strength to be detected by the algorithms. As the snow cover continues to build during the months of January through March, as well as on into the melt season, agreement between the two data types continually improves. This occurs because as the snow becomes deeper and the layered structure more complex, the negative spectral gradient driving the passive microwave algorithm

Experimental mouse model of optic neuritis with inflammatory demyelination produced by passive transfer of neuromyelitis optica-immunoglobulin G

Science.gov (United States)

2014-01-01

Background Although optic neuritis (ON) is a defining feature of neuromyelitis optica (NMO), appropriate animal models of NMO ON are lacking. Most NMO patients are seropositive for immunoglobulin G autoantibodies (NMO-IgG) against the astrocyte water channel aquaporin-4 (AQP4). Methods Several approaches were tested to develop a robust, passive-transfer mouse model of NMO ON, including NMO-IgG and complement delivery by: (i) retrobulbar infusion; (ii) intravitreal injection; (iii) a single intracranial injection near the optic chiasm; and (iv) 3-days continuous intracranial infusion near the optic chiasm. Results Little ON or retinal pathology was seen using approaches (i) to (iii). Using approach (iv), however, optic nerves showed characteristic NMO pathology, with loss of AQP4 and glial fibrillary acidic protein immunoreactivity, granulocyte and macrophage infiltration, deposition of activated complement, demyelination and axonal injury. Even more extensive pathology was created in mice lacking complement inhibitor protein CD59, or using a genetically modified NMO-IgG with enhanced complement effector function, including significant loss of retinal ganglion cells. In control studies, optic nerve pathology was absent in treated AQP4-deficient mice, or in wild-type mice receiving control (non-NMO) IgG and complement. Conclusion Passive transfer of NMO-IgG and complement by continuous infusion near the optic chiasm in mice is sufficient to produce ON with characteristic NMO pathology. The mouse model of NMO ON should be useful in further studies of NMO pathogenesis mechanisms and therapeutics. PMID:24468108

Two-level modulation scheme to reduce latency for optical mobile fronthaul networks.

Science.gov (United States)

Sung, Jiun-Yu; Chow, Chi-Wai; Yeh, Chien-Hung; Chang, Gee-Kung

2016-10-31

A system using optical two-level orthogonal-frequency-division-multiplexing (OFDM) - amplitude-shift-keying (ASK) modulation is proposed and demonstrated to reduce the processing latency for the optical mobile fronthaul networks. At the proposed remote-radio-head (RRH), the high data rate OFDM signal does not need to be processed, but is directly launched into a high speed photodiode (HSPD) and subsequently emitted by an antenna. Only a low bandwidth PD is needed to recover the low data rate ASK control signal. Hence, it is simple and provides low-latency. Furthermore, transporting the proposed system over the already deployed optical-distribution-networks (ODNs) of passive-optical-networks (PONs) is also demonstrated with 256 ODN split-ratios.

Secure passive RFID tag with seal

Science.gov (United States)

Nekoogar, Faranak; Reynolds, Matthew; Lefton, Scott; Dowla, Farid; Twogood, Richard

2017-11-14

A secure passive RFID tag system comprises at least one base station and at least one passive RFID tag. The tag includes a fiber optic cable with the cable ends sealed within the tag and the middle portion forming an external loop. The loop may be secured to at least portions of an object. The tag transmits and receives an optical signal through the fiber optic cable, and the cable is configured to be damaged or broken in response to removal or tampering attempts, wherein the optical signal is significantly altered if the cable is damaged or broken. The tag transmits the optical signal in response to receiving a radio signal from the base station and compares the transmitted optical signal to the received optical signal. If the transmitted optical signal and the received optical signal are identical, the tag transmits an affirmative radio signal to the base station.

Remote detection and ecological monitoring of the industrial and natural nuclei activity of radioactive elements based on passive microwave radiometry

Science.gov (United States)

Chistyakova, Liliya K.; Chistyakov, Vyacheslav Y.; Losev, Dmitry V.; Penin, Sergei T.; Tarabrin, Yurij K.; Yakubov, Vladimir P.; Yurjev, Igor A.

1998-12-01

The passive remote method of microwave radiometry and its instrumental realization for express diagnostics of radioactive elements in the atmosphere have been discussed. Analysis of the microwave radiation due to ionization and dissociation of atmospheric components interacting with radioactive elements is carried out. The photochemical processes resulting in background microwave radiation power have been discussed. As an example, the results of natural experiment of detecting the atomic hydrogen radiation in the plume of emissions of nuclear cycle processing plants have been presented.

Active and Passive Remote Sensing Data Time Series for Flood Detection and Surface Water Mapping

Science.gov (United States)

Bioresita, Filsa; Puissant, Anne; Stumpf, André; Malet, Jean-Philippe

2017-04-01

Split Based Approach (MSBA) is used in order to focus on surface water areas automatically and facilitate the estimation of class models for water and non-water areas. A Finite Mixture Model is employed as the underlying statistical model to produce probabilistic maps. Subsequently, bilateral filtering is applied to take into account spatial neighborhood relationships in the generation of final map. The elimination of shadows effect is performed in a post-processing step. The processing chain is tested on three case studies. The first case is a flood event in central Ireland, the second case is located in Yorkshire county / Great Britain, and the third test case covers a recent flood event in northern Italy. The tests showed that the modified SBA step and the Finite Mixture Models can be applied for the automatic surface water detection in a variety of test cases. An evaluation again Copernicus products derived from very-high resolution imagery was performed, and showed a high overall accuracy and F-measure of the obtained maps. This evaluation also showed that the use of probability maps and bilateral filtering improved the accuracy of classification results significantly. Based on this quantitative evaluation, it is concluded that the processing chain can be applied for flood mapping from Sentinel-1 data. To estimate robust statistical distributions the method requires sufficient surface waters areas in the observed zone and sufficient contrast between surface waters and other land use classes. Ongoing research addresses the fusion of Sentinel-1 and passive remote sensing data (e.g. Sentinel-2) in order to reduce the current shortcomings in the developed processing chain. In this work, fusion is performed at the feature level to better account for the difference image properties of SAR and optical sensors. Further, the processing chain is currently being optimized in terms of calculation time for a further integration as a flood mapping service on the A2S (Alsace Aval

Passive and Portable Polymer Optical Fiber Cleaver

DEFF Research Database (Denmark)

Saez-Rodriguez, D.; Min, R.; Ortega, B.

2016-01-01

opening up the possibility of an electrically passive cleaver. In this letter, we describe the implementation and testing of a high quality cleaver based on a mechanical system formed by a constant force spring and a damper, which leads to the first reported electrical passive and portable cleaver....

Remote measurement of ozone in Tuxtla Gutierrez, Chiapas, Mexico, using the DOAS technique

International Nuclear Information System (INIS)

Garcia, C.; Najera, H.; Camas, J.

2012-01-01

A brief description of a remote pollutants monitoring system based on passive differential optical absorption spectroscopy, which detects atmospheric trace gases. This system was placed in the campus facilities of the UNICACH, monitoring a linear extension approximately 2.9 km. We determined the concentration of ozone in the area of interest, also evaluating the influence of climatic conditions with the results obtained at the end were compared with a detection system used by the SEMAVIH, dependence government, observing a good correlation between them. (Author)

Demonstration of hybrid orbital angular momentum multiplexing and time-division multiplexing passive optical network.

Science.gov (United States)

Wang, Andong; Zhu, Long; Liu, Jun; Du, Cheng; Mo, Qi; Wang, Jian

2015-11-16

Mode-division multiplexing passive optical network (MDM-PON) is a promising scheme for next-generation access networks to further increase fiber transmission capacity. In this paper, we demonstrate the proof-of-concept experiment of hybrid mode-division multiplexing (MDM) and time-division multiplexing (TDM) PON architecture by exploiting orbital angular momentum (OAM) modes. Bidirectional transmissions with 2.5-Gbaud 4-level pulse amplitude modulation (PAM-4) downstream and 2-Gbaud on-off keying (OOK) upstream are demonstrated in the experiment. The observed optical signal-to-noise ratio (OSNR) penalties for downstream and upstream transmissions at a bit-error rate (BER) of 2 × 10(-3) are less than 2.0 dB and 3.0 dB, respectively.

Deterministically entangling multiple remote quantum memories inside an optical cavity

Science.gov (United States)

Yan, Zhihui; Liu, Yanhong; Yan, Jieli; Jia, Xiaojun

2018-01-01

Quantum memory for the nonclassical state of light and entanglement among multiple remote quantum nodes hold promise for a large-scale quantum network, however, continuous-variable (CV) memory efficiency and entangled degree are limited due to imperfect implementation. Here we propose a scheme to deterministically entangle multiple distant atomic ensembles based on CV cavity-enhanced quantum memory. The memory efficiency can be improved with the help of cavity-enhanced electromagnetically induced transparency dynamics. A high degree of entanglement among multiple atomic ensembles can be obtained by mapping the quantum state from multiple entangled optical modes into a collection of atomic spin waves inside optical cavities. Besides being of interest in terms of unconditional entanglement among multiple macroscopic objects, our scheme paves the way towards the practical application of quantum networks.

Frequency transfer via a two-way optical phase comparison on a multiplexed fiber network.

Science.gov (United States)

Calosso, C E; Bertacco, E; Calonico, D; Clivati, C; Costanzo, G A; Frittelli, M; Levi, F; Mura, A; Godone, A

2014-03-01

We performed a two-way remote optical phase comparison on optical fiber. Two optical frequency signals were launched in opposite directions in an optical fiber and their phases were simultaneously measured at the other end. In this technique, the fiber noise is passively canceled, and we compared two optical frequencies at the ultimate 10(-21) stability level. The experiment was performed on a 47 km fiber that is part of the metropolitan network for Internet traffic. The technique relies on the synchronous measurement of the optical phases at the two ends of the link, which is here performed by digital electronics. This scheme offers some advantages with respect to active noise cancellation schemes, as the light travels only once in the fiber.

Optical and electrical characterization of n-GaAs surfaces passivated by N{sub 2}-H{sub 2} plasma

Energy Technology Data Exchange (ETDEWEB)

Augelli, V.; Ligonzo, T.; Minafra, A.; Schiavulli, L.; Capozzi, V. E-mail: capozzi@ba.infn.it; Perna, G.; Ambrico, M.; Losurdo, M

2003-05-01

The passivation of GaAs (1 0 0) surface has been performed by using remote N{sub 2}-H{sub 2} (3% in H{sub 2}) RF plasma nitridation. The samples, consisting of n-doped GaAs wafers, show photoluminescence enhancement when the nitridation time and exposure to the plasma are in a narrow temporal window, so that a very thin (about 10 A) GaN layer is deposited on the GaAs surface. Pure N{sub 2} nitridation does not provide an efficient passivation, because it results in GaN layers with As and AsN{sub x} segregation at the GaN/GaAs interface. Increase of Au-GaAs Schottky barrier with the insertion of GaN interlayer and improvement of current-voltage characteristic have been observed.

Passive millimeter wave imaging and spectroscopy system for terrestrial remote sensing

Science.gov (United States)

Gopalsami, Nachappa; Liao, Shaolin; Koehl, Eugene R.; Elmer, Thomas W.; Heifetz, Alexander; Chien, Hual-Te; Raptis, Apostolos C.

2010-04-01

We have built a passive millimeter wave imaging and spectroscopy system with a 15-channel filter bank in the 146-154 GHz band for terrestrial remote sensing. We had built the spectroscopy system first and have now retrofitted an imaging element to it as a single pixel imager. The imaging element consisted of a 15-cm-diameter imaging lens fed to a corrugated scalar horn. Image acquisition is carried out by scanning the lens with a 2-axis translation stage. A LabVIEW-based software program integrates the imaging and spectroscopy systems with online display of spectroscopic information while the system scans each pixel position. The software also allows for integrating the image intensity of all 15 channels to increase the signal-to-noise ratio by a factor of ~4 relative to single channel image. The integrated imaging and spectroscopy system produces essentially 4-D data in which spatial data are along 2 dimensions, spectral data are in the 3rd dimension, and time is the 4th dimension. The system performance was tested by collecting imaging and spectral data with a 7.5-cm-diameter and 1m long gas cell in which test chemicals were introduced against a liquid nitrogen background.

Classification of remotely sensed data using OCR-inspired neural network techniques. [Optical Character Recognition

Science.gov (United States)

Kiang, Richard K.

1992-01-01

Neural networks have been applied to classifications of remotely sensed data with some success. To improve the performance of this approach, an examination was made of how neural networks are applied to the optical character recognition (OCR) of handwritten digits and letters. A three-layer, feedforward network, along with techniques adopted from OCR, was used to classify Landsat-4 Thematic Mapper data. Good results were obtained. To overcome the difficulties that are characteristic of remote sensing applications and to attain significant improvements in classification accuracy, a special network architecture may be required.

Advances in estimation methods of vegetation water content based on optical remote sensing techniques

Institute of Scientific and Technical Information of China (English)

无

2010-01-01

Quantitative estimation of vegetation water content(VWC) using optical remote sensing techniques is helpful in forest fire as-sessment,agricultural drought monitoring and crop yield estimation.This paper reviews the research advances of VWC retrieval using spectral reflectance,spectral water index and radiative transfer model(RTM) methods.It also evaluates the reli-ability of VWC estimation using spectral water index from the observation data and the RTM.Focusing on two main definitions of VWC-the fuel moisture content(FMC) and the equivalent water thickness(EWT),the retrieval accuracies of FMC and EWT using vegetation water indices are analyzed.Moreover,the measured information and the dataset are used to estimate VWC,the results show there are significant correlations among three kinds of vegetation water indices(i.e.,WSI,NDⅡ,NDWI1640,WI/NDVI) and canopy FMC of winter wheat(n=45).Finally,the future development directions of VWC detection based on optical remote sensing techniques are also summarized.

Remote Raman microimaging using an AOTF and a spatially coherent microfiber optical probe

International Nuclear Information System (INIS)

Trey Skinner, H.; Cooney, T.F.; Sharma, S.K.; Angel, S.M.

1996-01-01

A fiber-optic Raman microimaging probe is described that is suitable for acquiring high-spatial-resolution Raman images in sampling situations with no clear line of sight. A high-power near-infrared diode laser combined with an acousto-optic tunable filter and a spatially coherent optical fiber bundle allow fluorescence-free Raman images of remotely located samples to be acquired at distances up to several meters. The feasibility of this technique is demonstrated with Raman images of (1) a pellet containing a mixture of a highly scattering sample, bis-methylstyrylbenzene (BMSB), KCl, and graphite, and (2) a partially graphitized diamond. These images clearly show phase boundaries over an area of approximately 0.1 mm 2 with ∼4-μm resolution. copyright 1996 Society for Applied Spectroscopy

Conjugate adaptive optics with remote focusing in multiphoton microscopy

Science.gov (United States)

Tao, Xiaodong; Lam, Tuwin; Zhu, Bingzhao; Li, Qinggele; Reinig, Marc R.; Kubby, Joel

2018-02-01

The small correction volume for conventional wavefront shaping methods limits their application in biological imaging through scattering media. In this paper, we take advantage of conjugate adaptive optics (CAO) and remote focusing (CAORF) to achieve three-dimensional (3D) scanning through a scattering layer with a single correction. Our results show that the proposed system can provide 10 times wider axial field of view compared with a conventional conjugate AO system when 16,384 segments are used on a spatial light modulator. We demonstrate two-photon imaging with CAORF through mouse skull. The fluorescent microspheres embedded under the scattering layers can be clearly observed after applying the correction.

Passive components of NPP safety-related systems

International Nuclear Information System (INIS)

Ionaytis Romuald, R.; Bubnova Tatyana, A.

2005-01-01

This paper presents a new passive components with having drives: fast-response cutoff valves; modular actuators with opposite cocking pneumatic drives and actuation spring drives; voting electromagnetic valve units for control of pneumatic drives; passive initiators of actuation; visual diagnostics . All these devices have been developed and tested at mock-ups. This paper presents also the following direct-action passive safety components: modular pressure-relief safety valves; pilot safety valves with passive action; check valves with remote position indicator and after-tightening; modular inserts for limiting emergency coolant flow; vortex rectifier; critical weld fasteners; gas-liquid valves; fast-removable seal assembly; seal spring loaders; grooves for increasing hydraulic resistance. Replacement of active safety system components for passive ones improves the general reliability NPP by 1.5 or 2 orders of magnitudes. (authors)

A novel all-fiber optic flow cytometer technology for Point-of Care and Remote Environments

Science.gov (United States)

Mermut, Ozzy

Traditional flow cytometry designs tend to be bulky systems with a complex optical-fluidic sub-system and often require trained personnel for operation. This makes them difficult to readily translate to remote site testing applications. A new compact and portable fiber-optic flow cell (FOFC) technology has been developed at INO. We designed and engineered a specialty optical fiber through which a square hole is transversally bored by laser micromachining. A capillary is fitted into that hole to flow analyte within the fiber square cross-section for detection and counting. With demonstrated performance benchmarks potentially comparable to commercial flow cytometers, our FOFC provides several advantages compared to classic free-space con-figurations, e.g., sheathless flow, low cost, reduced number of optical components, no need for alignment (occurring in the fabrication process only), ease-of-use, miniaturization, portability, and robustness. This sheathless configuration, based on a fiber optic flow module, renders this cytometer amenable to space-grade microgravity environments. We present our recent results for an all-fiber approach to achieve a miniature FOFC to translate flow cytometry from bench to a portable, point-of-care device for deployment in remote settings. Our unique fiber approach provides the capability to illuminate a large surface with a uniform intensity distri-bution, independently of the initial shape originating from the light source, and without loss of optical power. The CVs and sensitivities are measured and compared to industry benchmarks. Finally, integration of LEDs enable several advantages in cost, compactness, and wavelength availability.

Observation of phase noise reduction in photonically synthesized sub-THz signals using a passively mode-locked laser diode and highly selective optical filtering

DEFF Research Database (Denmark)

Criado, A. R.; Acedo, P.; Carpintero, G.

2012-01-01

A Continuous Wave (CW) sub-THz photonic synthesis setup based on a single Passively Mode-Locked Laser Diode (PMLLD) acting as a monolithic Optical Frequency Comb Generator (OFCG) and highly selective optical filtering has been implemented to evaluate the phase noise performance of the generated sub...

Photonic synthesis of continuous‐wave millimeter‐wave signals using a passively mode‐locked laser diode and selective optical filtering

DEFF Research Database (Denmark)

Acedo, P.; Carpintero, G.; Criado, A.R.

2012-01-01

We report a photonic synthesis scheme for continuous wave millimeter‐wave signal generation using a single passively mode‐locked laser diode (PMLLD), optical filtering and photomixing in a fast photodiode.The phase noise of the photonically synthesized signals is evaluated and inherits...

Optical absorption and oxygen passivation of surface states in III-nitride photonic devices

Science.gov (United States)

Rousseau, Ian; Callsen, Gordon; Jacopin, Gwénolé; Carlin, Jean-François; Butté, Raphaël; Grandjean, Nicolas

2018-03-01

III-nitride surface states are expected to impact high surface-to-volume ratio devices, such as nano- and micro-wire light-emitting diodes, transistors, and photonic integrated circuits. In this work, reversible photoinduced oxygen desorption from III-nitride microdisk resonator surfaces is shown to increase optical attenuation of whispering gallery modes by 100 cm-1 at λ = 450 nm. Comparison of photoinduced oxygen desorption in unintentionally and n+-doped microdisks suggests that the spectral changes originate from the unpinning of the surface Fermi level, likely taking place at etched nonpolar III-nitride sidewalls. An oxygen-rich surface prepared by thermal annealing results in a broadband Q improvement to state-of-the-art values exceeding 1 × 104 at 2.6 eV. Such findings emphasize the importance of optically active surface states and their passivation for future nanoscale III-nitride optoelectronic and photonic devices.

Through the optical combiner monitoring in remote fiber laser welding of zinc coated steels

Science.gov (United States)

Colombo, Daniele; Colosimo, Bianca M.; Previtali, Barbara; Bassan, Daniele; Lai, Manuel; Masotti, Giovanni

2012-03-01

Thanks to the recent affirmation of the active fiber lasers, remote laser welding of zinc coated steels is under investigation with a particular emphasis on the overlap joint geometry. Due to the high power and high beam quality offered by these lasers, the remote laser welding process has become more practicable. However laser welding of lap zinc coated steels is still problematic because of the violent vaporisation of zinc. The presence of a gap between the plates allowing vapour degassing has been proven to avoid defects due to zinc vaporization. On the other hand variation in the gap value can lead to the welding defect formation. Therefore constant gap values should be ensured and deviation from the reference gap value has to be monitored during the execution of the welding process. Furthermore, the on-line monitoring of the gap values between the plates can be helpful for the on-line quality control of the welding process. The paper proposes a new monitoring solution for the measurement of the gap in remote fiber laser welding of overlapped zinc coated steels. In this solution, referred as Through the Optical Combiner Monitoring (TOCM) , the optical emissions from the welding process are directly observed through the optical combiner of the fiber laser source with spectroscopic equipment. The TOCM solution presented in the paper is integrated in an IPG YLS 3000 fiber laser source whose beam is deflected and focused by means of an El.En. ScanFiber scanning system with an equivalent focal length of 300 mm. After the definition of the right welding process conditions, spectroscopic tests are exploited to evaluate the optical emission from the welding plasma/plume. Acquired spectra are then analysed with multivariate data analysis approach in order to ensure gap monitoring. Results showed that with the proposed method it is possible to evaluate not only the gap between the plates but also the location inside the weld at which the variation occurs. Furthermore

Simultaneous retrieval of sea ice thickness and snow depth using concurrent active altimetry and passive L-band remote sensing data

Science.gov (United States)

Zhou, L.; Xu, S.; Liu, J.

2017-12-01

The retrieval of sea ice thickness mainly relies on satellite altimetry, and the freeboard measurements are converted to sea ice thickness (hi) under certain assumptions over snow loading. The uncertain in snow depth (hs) is a major source of uncertainty in the retrieved sea ice thickness and total volume for both radar and laser altimetry. In this study, novel algorithms for the simultaneous retrieval of hi and hs are proposed for the data synergy of L-band (1.4 GHz) passive remote sensing and both types of active altimetry: (1) L-band (1.4GHz) brightness temperature (TB) from Soil Moisture Ocean Salinity (SMOS) satellite and sea ice freeboard (FBice) from radar altimetry, (2) L-band TB data and snow freeboard (FBsnow) from laser altimetry. Two physical models serve as the forward models for the retrieval: L-band radiation model, and the hydrostatic equilibrium model. Verification with SMOS and Operational IceBridge (OIB) data is carried out, showing overall good retrieval accuracy for both sea ice parameters. Specifically, we show that the covariability between hs and FBsnow is crucial for the synergy between TB and FBsnow. Comparison with existing algorithms shows lower uncertainty in both sea ice parameters, and that the uncertainty in the retrieved sea ice thickness as caused by that of snow depth is spatially uncorrelated, with the potential reduction of the volume uncertainty through spatial sampling. The proposed algorithms can be applied to the retrieval of sea ice parameters at basin-scale, using concurrent active and passive remote sensing data based on satellites.

Formation of SiNx:H by PECVD: optimization of the optical, bulk passivation and structural properties for photovoltaic applications

International Nuclear Information System (INIS)

Lelievre, J.F.

2007-04-01

The hydrogenated silicon nitride SiNx:H is widely used as antireflection coating and passivation layer in the manufacture of silicon photovoltaic cells. The aim of this work was to implement a low frequency (440 kHz) PECVD reactor and to characterize the obtained SiN layers. After having determined the parameters of the optimal deposition, the physico-chemical structure of the layers has been studied. The optical properties have been studied with the aim to improve the antireflection coating of the photovoltaic cells. The surface and bulk passivation properties, induced by the SiN layer in terms of its stoichiometry, have been analyzed and have revealed the excellent passivating efficiency of this material. At last, have been studied the formation conditions of the silicon nano-crystals in the SiN matrix. (O.M.)

Developments for a passive optical node network for deployment in deep sea enabling time synchronous data readout

International Nuclear Information System (INIS)

Heine, Eric; Hoek, Mar van der; Hogenbirk, Jelle; Jansweijer, Peter; Mos, Sander; Peek, Henk

2009-01-01

An overview of an optical network design for a Very Large Volume neutrino Telescope (VLVnT) [Proceedings of the Workshop on Technical aspects of a VLVnT in the Mediterranean Sea, ISBN90-6488-026-3] residing on the seabed is presented. The passive optical network transports all data to shore in a synchronous way without data congestion. Due to fixed propagation delay and low jitter over the fiber network an accurate event time stamp can be generated onshore. The determined signal propagation can also serve for detector calibration. The results of a proto type vertical cable test are presented.

Towards attosecond synchronization of remote mode-locked lasers using stabilized transmission of optical comb frequencies

Science.gov (United States)

Wilcox, R. B.; Byrd, J. M.; Doolittle, L. R.; Holzwarth, R.; Huang, G.

2011-09-01

We propose a method of synchronizing mode-locked lasers separated by hundreds of meters with the possibility of achieving sub-fs performance by locking the phases of corresponding lines in the optical comb spectrum. The optical phase from one comb line is transmitted to the remote laser over an interferometrically stabilized link by locking a single frequency laser to a comb line with high phase stability. We describe how these elements are integrated into a complete system and estimate the potential performance.

Cybernetic group method of data handling (GMDH) statistical learning for hyperspectral remote sensing inverse problems in coastal ocean optics

Science.gov (United States)

Filippi, Anthony Matthew

For complex systems, sufficient a priori knowledge is often lacking about the mathematical or empirical relationship between cause and effect or between inputs and outputs of a given system. Automated machine learning may offer a useful solution in such cases. Coastal marine optical environments represent such a case, as the optical remote sensing inverse problem remains largely unsolved. A self-organizing, cybernetic mathematical modeling approach known as the group method of data handling (GMDH), a type of statistical learning network (SLN), was used to generate explicit spectral inversion models for optically shallow coastal waters. Optically shallow water light fields represent a particularly difficult challenge in oceanographic remote sensing. Several algorithm-input data treatment combinations were utilized in multiple experiments to automatically generate inverse solutions for various inherent optical property (IOP), bottom optical property (BOP), constituent concentration, and bottom depth estimations. The objective was to identify the optimal remote-sensing reflectance Rrs(lambda) inversion algorithm. The GMDH also has the potential of inductive discovery of physical hydro-optical laws. Simulated data were used to develop generalized, quasi-universal relationships. The Hydrolight numerical forward model, based on radiative transfer theory, was used to compute simulated above-water remote-sensing reflectance Rrs(lambda) psuedodata, matching the spectral channels and resolution of the experimental Naval Research Laboratory Ocean PHILLS (Portable Hyperspectral Imager for Low-Light Spectroscopy) sensor. The input-output pairs were for GMDH and artificial neural network (ANN) model development, the latter of which was used as a baseline, or control, algorithm. Both types of models were applied to in situ and aircraft data. Also, in situ spectroradiometer-derived Rrs(lambda) were used as input to an optimization-based inversion procedure. Target variables

Design of optical switches by illusion optics

International Nuclear Information System (INIS)

Shoorian, H R; Abrishamian, M S

2013-01-01

In this paper, illusion optics theory is employed to form Bragg gratings in an optical waveguide in order to design an optical switch. By using an illusion device at a certain distance from the waveguide, the effective refractive index of the waveguide is remotely modulated, turning the waveguide into a distributed Bragg reflector (DBR) which blocks the waves at a stop band. By removing the illusion device, the waves propagate through the waveguide again. In addition, this method is used to remotely tune DBR optical properties such as resonant frequency and bandwidth in a wide range, which leads to a tunable filter for optical switching applications. Finally, using an illusion device at a distance, an optical cavity is created by inserting defects remotely in a DBR without any physical damage in the primary device. (paper)

Design of optical switches by illusion optics

Science.gov (United States)

Shoorian, H. R.; Abrishamian, M. S.

2013-05-01

In this paper, illusion optics theory is employed to form Bragg gratings in an optical waveguide in order to design an optical switch. By using an illusion device at a certain distance from the waveguide, the effective refractive index of the waveguide is remotely modulated, turning the waveguide into a distributed Bragg reflector (DBR) which blocks the waves at a stop band. By removing the illusion device, the waves propagate through the waveguide again. In addition, this method is used to remotely tune DBR optical properties such as resonant frequency and bandwidth in a wide range, which leads to a tunable filter for optical switching applications. Finally, using an illusion device at a distance, an optical cavity is created by inserting defects remotely in a DBR without any physical damage in the primary device.

Focusing over Optical Fiber Using Time Reversal

DEFF Research Database (Denmark)

Piels, Molly; Porto da Silva, Edson; Estaran Tolosa, Jose Manuel

2015-01-01

A time-reversal array in multimode fiber is proposed for lossless remotely controlled switching using passive optical splitters. The signal to be transmitted is digitally pre-distorted so that it is routed through the physical layer in order to arrive at only one receiver in an array. System...... performance in the presence of additive white gaussian noise, modal group delay, and timing error is investigated numerically for single-mode and 10-mode fiber. Focusing using a two-transmitter array and 44 km of single- mode fiber is demonstrated experimentally for 3 GBd QPSK signals with a bit error rate...

Link Power Budget and Traffict QoS Performance Analysis of Gygabit Passive Optical Network

Science.gov (United States)

Ubaidillah, A.; Alfita, R.; Toyyibah

2018-01-01

Data service of telecommunication network is needed widely in the world; therefore extra wide bandwidth must be provided. For this case, PT. Telekomunikasi Tbk. applies GPON (Gigabit Passive Optical Network) as optical fibre based on telecommunication network system. GPON is a point to a multipoint technology of FTTx (Fiber to The x) that transmits information signals to the subscriber over optical fibre. In GPON trunking system, from OLT (Optical Line Terminal), the network is split to many ONT (Optical Network Terminal) of the subscribers, so it causes path loss and attenuation. In this research, the GPON performance is measured from the link power budget system and the Quality of Service (QoS) of the traffic. And the observation result shows that the link power budget system of this GPON is in good condition. The link power budget values from the mathematical calculation and direct measurement are satisfy the ITU-T G984 Class B standard, that the power level must be between -8 dBm to -27 dBm. While from the traffic performance, the observation result shows that the network resource utility of the subscribers of the observed area is not optimum. The mean of subscriber utility rate is 27.985 bps for upstream and 79.687 bps for downstream. While maximally, It should be 60.800 bps for upstream and 486.400 bps for downstream.

AT89S52 Microcontroller Based Remote Room Monitoring System Using Passive Infrared Sensor

Directory of Open Access Journals (Sweden)

Albert Gifson

2009-12-01

Full Text Available This research describes about the design of the room detection system using a Passive Infrared sensors (PIR controlled by Microcontroller AT89S52 for remote control application. The output of the PIR is a low logic when it captures the heat waves of the human body. The output PIR is connected to the port 1.7 on Microcontroller in high logic. The maximum distance is 5 meters for the sensor to detect an object. When there is a signal sent by PIR, the Microcontroller processes the data and activates the buzzer to beep and the stepper motor to stop. Microcontroller also sends data through the RS-232 that continues a signal to the personal mobile phone. In order that the message is able to be sent, then first, messages must be programmed and stored in the Microcontroller AT89S52. The average message delivery time is 8.8 seconds. The recipient can turn the alarm of system on or off by a missed call.

18-THz-wide optical frequency comb emitted from monolithic passively mode-locked semiconductor quantum-well laser

Science.gov (United States)

Lo, Mu-Chieh; Guzmán, Robinson; Ali, Muhsin; Santos, Rui; Augustin, Luc; Carpintero, Guillermo

2017-10-01

We report on an optical frequency comb with 14nm (~1.8 THz) spectral bandwidth at -3 dB level that is generated using a passively mode-locked quantum-well (QW) laser in photonic integrated circuits (PICs) fabricated through an InP generic photonic integration technology platform. This 21.5-GHz colliding-pulse mode-locked laser cavity is defined by on-chip reflectors incorporating intracavity phase modulators followed by an extra-cavity SOA as booster amplifier. A 1.8-THz-wide optical comb spectrum is presented with ultrafast pulse that is 0.35-ps-wide. The radio frequency beat note has a 3-dB linewidth of 450 kHz and 35-dB SNR.

Classification of Several Optically Complex Waters in China Using in Situ Remote Sensing Reflectance

Directory of Open Access Journals (Sweden)

Qian Shen

2015-11-01

Full Text Available Determining the dominant optically active substances in water bodies via classification can improve the accuracy of bio-optical and water quality parameters estimated by remote sensing. This study provides four robust centroid sets from in situ remote sensing reflectance (Rrs (λ data presenting typical optical types obtained by plugging different similarity measures into fuzzy c-means (FCM clustering. Four typical types of waters were studied: (1 highly mixed eutrophic waters, with the proportion of absorption of colored dissolved organic matter (CDOM, phytoplankton, and non-living particulate matter at approximately 20%, 20%, and 60% respectively; (2 CDOM-dominated relatively clear waters, with approximately 45% by proportion of CDOM absorption; (3 nonliving solids-dominated waters, with approximately 88% by proportion of absorption of nonliving particulate matter; and (4 cyanobacteria-composed scum. We also simulated spectra from seven ocean color satellite sensors to assess their classification ability. POLarization and Directionality of the Earth's Reflectances (POLDER, Sentinel-2A, and MEdium Resolution Imaging Spectrometer (MERIS were found to perform better than the rest. Further, a classification tree for MERIS, in which the characteristics of Rrs (709/Rrs (681, Rrs (560/Rrs (709, Rrs (560/Rrs (620, and Rrs (709/Rrs (761 are integrated, is also proposed in this paper. The overall accuracy and Kappa coefficient of the proposed classification tree are 76.2% and 0.632, respectively.

Analisis Redaman Pada Jaringan FTTH (Fiber To The Home Dengan Teknologi GPON (Gigabit Passive Optical Network Di PT MNC Kabel Mediacom

Directory of Open Access Journals (Sweden)

Minal Abral

2017-06-01

Full Text Available iber optic merupakan teknologi yang menyediakan kapasitas bandwith besar dengan kecepatan tinggi, tidak dipengaruhi interferensi gelombang elektromagnetik, Sejalan dengan berkembang secara pesatnya penggunaan serat optik sebagai medium penghantar, ada kemungkinan terjadinya hilang informasi akibat kerugian dari pemanjangan kabel fiber optic ataupun penyambungan kabel fiber optic, kerugian tersebut yaitu redaman. Dalam penerapan metode link power budget, perhitungan redaman dilakukan dengan data yang diperoleh berdasarkan standarisasi dan pengukuran menggunakan perangkat optical power meter. Hasil analisa perhitungan, sistem mampu dalam keadaan normal menggunakan layanan gigabit passive optical network dapat diterima oleh perangkat akhir jaringan fiber to the home pada pelanggan perusahaan PT MNC Kabel Mediacom yang berada di Kelurahan Jati RW 02 Pulo Gadung Jakarta Timur.

Classification of bottom composition and bathymetry of shallow waters by passive remote sensing

Science.gov (United States)

Spitzer, D.; Dirks, R. W. J.

The use of remote sensing data in the development of algorithms to remove the influence of the watercolumn on upwelling optical signals when mapping the bottom depth and composition in shallow waters. Calculations relating the reflectance spectra to the parameters of the watercolumn and the diverse bottom types are performed and measurements of the underwater reflection coefficient of sandy, mud, and vegetation-type seabottoms are taken. The two-flow radiative transfer model is used. Reflectances within the spectral bands of the Landsat MSS, the Landsat TM, SPOT HVR, and the TIROS-N series AVHRR were computed in order to develop appropriate algorithms suitable for the bottom depth and type mapping. Bottom depth and features appear to be observable down to 3-20 m depending on the water composition and bottom type.

Optical telescope refocussing mechanism concept design on remote sensing satellite

Science.gov (United States)

Kuo, Jen-Chueh; Ling, Jer

2017-09-01

The optical telescope system in remote sensing satellite must be precisely aligned to obtain high quality images during its mission life. In practical, because the telescope mirrors could be misaligned due to launch loads, thermal distortion on supporting structures or hygroscopic distortion effect in some composite materials, the optical telescope system is often equipped with refocussing mechanism to re-align the optical elements while optical element positions are out of range during image acquisition. This paper is to introduce satellite Refocussing mechanism function model design development process and the engineering models. The design concept of the refocussing mechanism can be applied on either cassegrain type telescope or korsch type telescope, and the refocussing mechanism is located at the rear of the secondary mirror in this paper. The purpose to put the refocussing mechanism on the secondary mirror is due to its higher sensitivity on MTF degradation than other optical elements. There are two types of refocussing mechanism model to be introduced: linear type model and rotation type model. For the linear refocussing mechanism function model, the model is composed of ceramic piezoelectric linear step motor, optical rule as well as controller. The secondary mirror is designed to be precisely moved in telescope despace direction through refocussing mechanism. For the rotation refocussing mechanism function model, the model is assembled with two ceramic piezoelectric rotational motors around two orthogonal directions in order to adjust the secondary mirror attitude in tilt angle and yaw angle. From the validation test results, the linear type refocussing mechanism function model can be operated to adjust the secondary mirror position with minimum 500 nm resolution with close loop control. For the rotation type model, the attitude angle of the secondary mirror can be adjusted with the minimum 6 sec of arc resolution and 5°/sec of angle velocity.

On the Ability of Space- Based Passive and Active Remote Sensing Observations of CO2 to Detect Flux Perturbations to the Carbon Cycle

Science.gov (United States)

Crowell, Sean M. R.; Kawa, S. Randolph; Browell, Edward V.; Hammerling, Dorit M.; Moore, Berrien; Schaefer, Kevin; Doney, Scott C.

2018-01-01

Space-borne observations of CO2 are vital to gaining understanding of the carbon cycle in regions of the world that are difficult to measure directly, such as the tropical terrestrial biosphere, the high northern and southern latitudes, and in developing nations such as China. Measurements from passive instruments such as GOSAT (Greenhouse Gases Observing Satellite) and OCO-2 (Orbiting Carbon Observatory 2), however, are constrained by solar zenith angle limitations as well as sensitivity to the presence of clouds and aerosols. Active measurements such as those in development for the Active Sensing of CO2 Emissions over Nights, Days and Seasons (ASCENDS) mission show strong potential for making measurements in the high-latitude winter and in cloudy regions. In this work we examine the enhanced flux constraint provided by the improved coverage from an active measurement such as ASCENDS. The simulation studies presented here show that with sufficient precision, ASCENDS will detect permafrost thaw and fossil fuel emissions shifts at annual and seasonal time scales, even in the presence of transport errors, representativeness errors, and biogenic flux errors. While OCO-2 can detect some of these perturbations at the annual scale, the seasonal sampling provided by ASCENDS provides the stronger constraint. Plain Language Summary: Active and passive remote sensors show the potential to provide unprecedented information on the carbon cycle. With the all-season sampling, active remote sensors are more capable of constraining high-latitude emissions. The reduced sensitivity to cloud and aerosol also makes active sensors more capable of providing information in cloudy and polluted scenes with sufficient accuracy. These experiments account for errors that are fundamental to the top-down approach for constraining emissions, and even including these sources of error, we show that satellite remote sensors are critical for understanding the carbon cycle.

Advanced Optics for the Remote Steering ITER ECRH Upper Launcher

International Nuclear Information System (INIS)

Bruschi, A; Cirant, S; Moro, A; Platania, P; Sozzi, C

2005-01-01

The optics of the ECRH Upper Launcher in ITER based on the Remote Steering concept needs special attention, since any focussing element in front of the waveguide has combined effects on the range of steering angles achievable and the beam width in the plasma region. The effects are studied in detail for a setup composed by 8 beams per port (three ports), for a spherical and a hyperbolic mirror surface. Gaussian beam analysis is compared to beam pattern calculations with the optical physics code GRASP, in order to verify the validity of gaussian optics approximation. The standard description with simply astigmatic beams, not adequate in more complex systems as the proposed two-mirror set-up, requires approximations, which are compared with the generalized astigmatic beam description. The ohmic losses at the end mirrors and the related localized heating due to the very large power density cause deformations that depends on the design of the cooling circuit. The distortion of the beam shape has been evaluated in a realistic case of mirror cooling with a small-channel system. The quantification of the effect depends on the precise evaluation ohmic losses and their enhancement in the long term due to the surface deterioration

CoMet: an airborne mission to simultaneously measure CO2 and CH4 using lidar, passive remote sensing, and in-situ techniques

Science.gov (United States)

Fix, Andreas; Amediek, Axel; Bovensmann, Heinrich; Ehret, Gerhard; Gerbig, Christoph; Gerilowski, Konstantin; Pfeilsticker, Klaus; Roiger, Anke; Zöger, Martin

2018-04-01

TIn order to improve our current knowledge on the budgets of the two most important anthropogenic greenhouse gases, CO2 and CH4, an airborne mission on board the German research aircraft HALO in coordination with two smaller Cessna aircraft is going to be conducted in April/May 2017. The goal of CoMet is to combine a suite of the best currently available active (lidar) and passive remote sensors as well as in-situ instruments to provide regional-scale data of greenhouse gases which are urgently required.

Estimation of Hydraulic properties of a sandy soil using ground-based active and passive microwave remote sensing

KAUST Repository

Jonard, François

2015-06-01

In this paper, we experimentally analyzed the feasibility of estimating soil hydraulic properties from 1.4 GHz radiometer and 0.8-2.6 GHz ground-penetrating radar (GPR) data. Radiometer and GPR measurements were performed above a sand box, which was subjected to a series of vertical water content profiles in hydrostatic equilibrium with a water table located at different depths. A coherent radiative transfer model was used to simulate brightness temperatures measured with the radiometer. GPR data were modeled using full-wave layered medium Green\\'s functions and an intrinsic antenna representation. These forward models were inverted to optimally match the corresponding passive and active microwave data. This allowed us to reconstruct the water content profiles, and thereby estimate the sand water retention curve described using the van Genuchten model. Uncertainty of the estimated hydraulic parameters was quantified using the Bayesian-based DREAM algorithm. For both radiometer and GPR methods, the results were in close agreement with in situ time-domain reflectometry (TDR) estimates. Compared with radiometer and TDR, much smaller confidence intervals were obtained for GPR, which was attributed to its relatively large bandwidth of operation, including frequencies smaller than 1.4 GHz. These results offer valuable insights into future potential and emerging challenges in the development of joint analyses of passive and active remote sensing data to retrieve effective soil hydraulic properties.

Remote sensing reflectance simulation of coastal optical complex water in the East China Sea

Science.gov (United States)

He, Shuo; Lou, Xiulin; Zhang, Huaguo; Zheng, Gang

2018-02-01

In this work, remote sensing reflectance (Rrs) spectra of the Zhejiang coastal water in the East China Sea (ECS) were simulated by using the Hydrolight software with field data as input parameters. The seawater along the Zhejiang coast is typical Case II water with complex optical properties. A field observation was conducted in the Zhejiang coastal region in late May of 2016, and the concentration of ocean color constituents (pigment, SPM and CDOM), IOPs (absorption and backscattering coefficients) and Rrs were measured at 24 stations of 3 sections covering the turbid to clear inshore coastal waters. Referring to these ocean color field data, an ocean color model suitable for the Zhejiang coastal water was setup and applied in the Hydrolight. A set of 11 remote sensing reflectance spectra above water surface were modeled and calculated. Then, the simulated spectra were compared with the filed measurements. Finally, the spectral shape and characteristics of the remote sensing reflectance spectra were analyzed and discussed.

Remote measurements of actinide species in aqueous solutions using an optical fiber photoacoustic spectrometer

International Nuclear Information System (INIS)

Russo, R.E.; Robouch, P.B.; Silva, R.J.

1990-01-01

A photoacoustic spectrometer, equipped with an 85 meter optical fiber, was used to perform absorption measurements of lanthanide and actinide samples, located in a glovebox. The spectrometer was tested using aqueous solutions of praseodymium and americium ions; the sensitivity for remote measurements was found to be similar to that achieved in the laboratory without the fiber. 14 refs., 3 figs

Oxidation of hydrogen-passivated silicon surfaces by scanning near-field optical lithography using uncoated and aluminum-coated fiber probes

DEFF Research Database (Denmark)

Madsen, Steen; Bozhevolnyi, Sergey I.; Birkelund, Karen

1997-01-01

Optically induced oxidation of hydrogen-passivated silicon surfaces using a scanning near-field optical microscope was achieved with both uncoated and aluminum-coated fiber probes. Line scans on amorphous silicon using uncoated fiber probes display a three-peak profile after etching in potassium...... hydroxide. Numerical simulations of the electromagnetic field around the probe-sample interaction region are used to explain the experimental observations. With an aluminum-coated fiber probe, lines of 35 nm in width were transferred into the amorphous silicon layer. (C) 1997 American Institute of Physics....

Comprehensive study of electro-optic and passive Q-switching in solid state lasers for altimeter applications

Science.gov (United States)

Bhardwaj, Atul; Agrawal, Lalita; Pal, Suranjan; Kumar, Anil

2006-12-01

Laser Science and Technology Center (LASTEC), Delhi, is developing a space qualified diode pumped Nd: YAG laser transmitter capable of generating 10 ns pulses of 30 mJ energy @ 10 pps. This paper presents the results of experiments for comparative studies between electro-optic and passively Q-switched Nd: YAG laser in a crossed porro prism based laser resonator. Experimental studies have been performed by developing an economical bench model of flash lamp pumped Nd: YAG laser (rod dimension, \

Development of radio frequency interference detection algorithms for passive microwave remote sensing

Science.gov (United States)

Misra, Sidharth

Radio Frequency Interference (RFI) signals are man-made sources that are increasingly plaguing passive microwave remote sensing measurements. RFI is of insidious nature, with some signals low power enough to go undetected but large enough to impact science measurements and their results. With the launch of the European Space Agency (ESA) Soil Moisture and Ocean Salinity (SMOS) satellite in November 2009 and the upcoming launches of the new NASA sea-surface salinity measuring Aquarius mission in June 2011 and soil-moisture measuring Soil Moisture Active Passive (SMAP) mission around 2015, active steps are being taken to detect and mitigate RFI at L-band. An RFI detection algorithm was designed for the Aquarius mission. The algorithm performance was analyzed using kurtosis based RFI ground-truth. The algorithm has been developed with several adjustable location dependant parameters to control the detection statistics (false-alarm rate and probability of detection). The kurtosis statistical detection algorithm has been compared with the Aquarius pulse detection method. The comparative study determines the feasibility of the kurtosis detector for the SMAP radiometer, as a primary RFI detection algorithm in terms of detectability and data bandwidth. The kurtosis algorithm has superior detection capabilities for low duty-cycle radar like pulses, which are more prevalent according to analysis of field campaign data. Most RFI algorithms developed have generally been optimized for performance with individual pulsed-sinusoidal RFI sources. A new RFI detection model is developed that takes into account multiple RFI sources within an antenna footprint. The performance of the kurtosis detection algorithm under such central-limit conditions is evaluated. The SMOS mission has a unique hardware system, and conventional RFI detection techniques cannot be applied. Instead, an RFI detection algorithm for SMOS is developed and applied in the angular domain. This algorithm compares

Fiber optic sensor based on Mach-Zehnder interferometer for securing entrance areas of buildings

Science.gov (United States)

Nedoma, Jan; Fajkus, Marcel; Martinek, Radek; Mec, Pavel; Novak, Martin; Bednarek, Lukas; Vasinek, Vladimir

2017-10-01

Authors of this article focused on the utilization of fiber optic sensors based on interferometric measurements for securing entrance areas of buildings such as windows and doors. We described the implementation of the fiber-optic interferometer (type Mach-Zehnder) into the window frame or door, sensor sensitivity, analysis of the background noise and methods of signal evaluation. The advantage of presented solution is the use of standard telecommunication fiber standard G.652.D, high sensitivity, immunity of sensor to electromagnetic interference (EMI) and passivity of the sensor regarding power supply. Authors implemented the Graphical User Interface (GUI) which offers the possibility of remote monitoring presented sensing solution.

Comparison of Small-Scale Actively and Passively Q-Switched Eye-Safe Intracavity Optical Parametric Oscillators at 1.57 μm

International Nuclear Information System (INIS)

Miao Jie-Guang; Pan Yu-Zhai; Qu Shi-Liang

2012-01-01

The first experimental comparison between the actively and passively Q-switched intracavity optical parametric oscillators (IOPOs) at 1.57 μm driven by a small-scale diode-pumped Nd:YVO 4 laser are thoroughly presented. It is found that the performances of the two types of IOPOs are complementary. The actively Q-switched IOPO features a shorter pulse duration, a higher peak power, and a superior power and pulse stability. However, in terms of compactness, operation threshold and conversion efficiency, passively Q-switched IOPOs are more attractive. It is further indicated that the passively Q-switched IOPO at 1.57μm is a promising and cost-effective eye-safe laser source, especially at the low and moderate output levels. In addition, instructional improvement measures for the two types of IOPOs are also summarized. (fundamental areas of phenomenology(including applications))

Hydraulic description of a flood event with optical remote sensors: a constructive constraint on modelling uncertainties

Science.gov (United States)

Battiston, Stéphanie; Allenbach, Bernard

2010-05-01

The exceptional characteristics of the December 2003 Rhône flood event (particularly high water flows, extent of the affected area, important damages especially in the region of Arles) make it be considered as a reference flood episode of this French river and a very well-known event. During the crisis, the International Charter "Space and Major Disasters" was triggered by the French Civil Protection for the rapid mapping of the flooding using Earth Observation imagery in order to facilitate crisis operations. As a result, more than 60 satellite images covering the flood were acquired over a 10 days period following the peak flow. Using the opportunity provided by this incomparable data coverage, the French Ministry of the Environment ordered a study on the evaluation of remote sensing's potential benefits for flood management. One of the questions asked by the risk managers was: what type of flood information can be provided by the different remote sensing platforms? Elements of response were delivered mainly in the form of a comprehensive compilation of maps and illustrations, displaying the main hydraulic elements (static ones as well as dynamic ones), initially listed and requested by hydrologists (more precisely, by a regional engineering society specialised in hydraulics and hydrology and in charge of a field campaign during the event), observed on different optical images of the flood event having affected the plain between Tarascon (upstream) and Arles (downstream). It is seen that a careful mapping of all flood traces visible on remote sensing event imagery - apparent water, moisture traces, breaches, overflows, stream directions, impermeable boundaries … - delivers a valuable vision of the flood's occurrence combining accuracy and comprehensiveness. In fact, optical imagery offers a detailed vision of the event : moisture traces complete flood traces extent; the observation of draw-off directions through waterproof barriers reveals hydraulic

Micro-vision servo control of a multi-axis alignment system for optical fiber assembly

International Nuclear Information System (INIS)

Chen, Weihai; Yu, Fei; Qu, Jianliang; Chen, Wenjie; Zhang, Jianbin

2017-01-01

This paper describes a novel optical fiber assembly system featuring a multi-axis alignment function based on micro-vision feedback control. It consists of an active parallel alignment mechanism, a passive compensation mechanism, a micro-gripper and a micro-vision servo control system. The active parallel alignment part is a parallelogram-based design with remote-center-of-motion (RCM) function to achieve precise rotation without fatal lateral motion. The passive mechanism, with five degrees of freedom (5-DOF), is used to implement passive compensation for multi-axis errors. A specially designed 1-DOF micro-gripper mounted onto the active parallel alignment platform is adopted to grasp and rotate the optical fiber. A micro-vision system equipped with two charge-coupled device (CCD) cameras is introduced to observe the small field of view and obtain multi-axis errors for servo feedback control. The two CCD cameras are installed in an orthogonal arrangement—thus the errors can be easily measured via the captured images. Meanwhile, a series of tracking and measurement algorithms based on specific features of the target objects are developed. Details of the force and displacement sensor information acquisition in the assembly experiment are also provided. An experiment demonstrates the validity of the proposed visual algorithm by achieving the task of eliminating errors and inserting an optical fiber to the U-groove accurately. (paper)

Sensor Performance Requirements for the Retrieval of Atmospheric Aerosols by Airborne Optical Remote Sensing

Directory of Open Access Journals (Sweden)

Klaus I. Itten

2008-03-01

Full Text Available This study explores performance requirements for the retrieval of the atmospheric aerosol optical depth (AOD by airborne optical remote sensing instruments. Independent of any retrieval techniques, the calculated AOD retrieval requirements are compared with the expected performance parameters of the upcoming hyperspectral sensor APEX at the reference wavelength of 550nm. The AOD accuracy requirements are defined to be capable of resolving transmittance differences of 0.01 to 0.04 according to the demands of atmospheric corrections for remote sensing applications. For the purposes of this analysis, the signal at the sensor level is simulated by radiation transfer equations. The resulting radiances are translated into the AOD retrieval sensitivity (Δτλaer and compared to the available measuring sensitivity of the sensor (NE ΔLλsensor. This is done for multiple signal-to-noise ratios (SNR and surface reflectance values. It is shown that an SNR of 100 is adequate for AOD retrieval at 550nm under typical remote sensing conditions and a surface reflectance of 10% or less. Such dark surfaces require the lowest SNR values and therefore offer the best sensitivity for measuring AOD. Brighter surfaces with up to 30% reflectance require an SNR of around 300. It is shown that AOD retrieval for targets above 50% surface reflectance is more problematic with the current sensor performance as it may require an SNR larger than 1000. In general, feasibility is proven for the analyzed cases under simulated conditions.

Deploying Monitoring Trails for Fault Localization in All- Optical Networks and Radio-over-Fiber Passive Optical Networks

Science.gov (United States)

Maamoun, Khaled Mohamed

Fault localization is the process of realizing the true source of a failure from a set of collected failure notifications. Isolating failure recovery within the network optical domain is necessary to resolve alarm storm problems. The introduction of the monitoring trail (m-trail) has been proven to deliver better performance by employing monitoring resources in a form of optical trails - a monitoring framework that generalizes all the previously reported counterparts. In this dissertation, the m-trail design is explored and a focus is given to the analysis on using m-trails with established lightpaths to achieve fault localization. This process saves network resources by reducing the number of the m-trails required for fault localization and therefore the number of wavelengths used in the network. A novel approach based on Geographic Midpoint Technique, an adapted version of the Chinese Postman's Problem (CPP) solution and an adapted version of the Traveling Salesman's Problem (TSP) solution algorithms is introduced. The desirable features of network architectures and the enabling of innovative technologies for delivering future millimeter-waveband (mm-WB) Radio-over-Fiber (RoF) systems for wireless services integrated in a Dense Wavelength Division Multiplexing (DWDM) is proposed in this dissertation. For the conceptual illustration, a DWDM RoF system with channel spacing of 12.5 GHz is considered. The mm-WB Radio Frequency (RF) signal is obtained at each Optical Network Unit (ONU) by simultaneously using optical heterodyning photo detection between two optical carriers. The generated RF modulated signal has a frequency of 12.5 GHz. This RoF system is easy, cost-effective, resistant to laser phase noise and also reduces maintenance needs, in principle. A revision of related RoF network proposals and experiments is also included. A number of models for Passive Optical Networks (PON)/ RoF-PON that combine both innovative and existing ideas along with a number of

Surface-passivation-induced optical changes in Ge quantum dots

International Nuclear Information System (INIS)

Reboredo, F. A.; Zunger, Alex

2001-01-01

One of the most interesting properties of quantum dots is the possibility to tune the band gap as a function of their size. Here we explore the possibility of changing the lifetime of the lowest-energy excited state by altering the surface passivation. We show that a moderately electronegative passivation potential can induce long-lived excitons without appreciable changes to the band gap. In addition, for such passivation the symmetry of the valence-band maximum is γ 8# sub v# (t 1 derived) instead of the more usual γ 8v (t 2 derived). This reverses the effect of the exchange interaction on the bright-dark exciton splitting

Athermalization of resonant optical devices via thermo-mechanical feedback

Science.gov (United States)

Rakich, Peter; Nielson, Gregory N.; Lentine, Anthony L.

2016-01-19

A passively athermal photonic system including a photonic circuit having a substrate and an optical cavity defined on the substrate, and passive temperature-responsive provisions for inducing strain in the optical cavity of the photonic circuit to compensate for a thermo-optic effect resulting from a temperature change in the optical cavity of the photonic circuit. Also disclosed is a method of passively compensating for a temperature dependent thermo-optic effect resulting on an optical cavity of a photonic circuit including the step of passively inducing strain in the optical cavity as a function of a temperature change of the optical cavity thereby producing an elasto-optic effect in the optical cavity to compensate for the thermo-optic effect resulting on an optical cavity due to the temperature change.

Remote sensing estimation of colored dissolved organic matter (CDOM) in optically shallow waters

Science.gov (United States)

Li, Jiwei; Yu, Qian; Tian, Yong Q.; Becker, Brian L.

2017-06-01

It is not well understood how bottom reflectance of optically shallow waters affects the algorithm performance of colored dissolved organic matters (CDOM) retrieval. This study proposes a new algorithm that considers bottom reflectance in estimating CDOM absorption from optically shallow inland or coastal waters. The field sampling was conducted during four research cruises within the Saginaw River, Kawkawlin River and Saginaw Bay of Lake Huron. A stratified field sampling campaign collected water samples, determined the depth at each sampling location and measured optical properties. The sampled CDOM absorption at 440 nm broadly ranged from 0.12 to 8.46 m-1. Field sample analysis revealed that bottom reflectance does significantly change water apparent optical properties. We developed a CDOM retrieval algorithm (Shallow water Bio-Optical Properties algorithm, SBOP) that effectively reduces uncertainty by considering bottom reflectance in shallow waters. By incorporating the bottom contribution in upwelling radiances, the SBOP algorithm was able to explain 74% of the variance of CDOM values (RMSE = 0.22 and R2 = 0.74). The bottom effect index (BEI) was introduced to efficiently separate optically shallow and optically deep waters. Based on the BEI, an adaptive approach was proposed that references the amount of bottom effect in order to identify the most suitable algorithm (optically shallow water algorithm [SBOP] or optically deep water algorithm [QAA-CDOM]) to improve CDOM estimation (RMSE = 0.22 and R2 = 0.81). Our results potentially help to advance the capability of remote sensing in monitoring carbon pools at the land-water interface.

Remote sensing of atmospheric optical depth using a smartphone sun photometer.

Science.gov (United States)

Cao, Tingting; Thompson, Jonathan E

2014-01-01

In recent years, smart phones have been explored for making a variety of mobile measurements. Smart phones feature many advanced sensors such as cameras, GPS capability, and accelerometers within a handheld device that is portable, inexpensive, and consistently located with an end user. In this work, a smartphone was used as a sun photometer for the remote sensing of atmospheric optical depth. The top-of-the-atmosphere (TOA) irradiance was estimated through the construction of Langley plots on days when the sky was cloudless and clear. Changes in optical depth were monitored on a different day when clouds intermittently blocked the sun. The device demonstrated a measurement precision of 1.2% relative standard deviation for replicate photograph measurements (38 trials, 134 datum). However, when the accuracy of the method was assessed through using optical filters of known transmittance, a more substantial uncertainty was apparent in the data. Roughly 95% of replicate smart phone measured transmittances are expected to lie within ±11.6% of the true transmittance value. This uncertainty in transmission corresponds to an optical depth of approx. ±0.12-0.13 suggesting the smartphone sun photometer would be useful only in polluted areas that experience significant optical depths. The device can be used as a tool in the classroom to present how aerosols and gases effect atmospheric transmission. If improvements in measurement precision can be achieved, future work may allow monitoring networks to be developed in which citizen scientists submit acquired data from a variety of locations.

Remote sensing of atmospheric optical depth using a smartphone sun photometer.

Directory of Open Access Journals (Sweden)

Tingting Cao

Full Text Available In recent years, smart phones have been explored for making a variety of mobile measurements. Smart phones feature many advanced sensors such as cameras, GPS capability, and accelerometers within a handheld device that is portable, inexpensive, and consistently located with an end user. In this work, a smartphone was used as a sun photometer for the remote sensing of atmospheric optical depth. The top-of-the-atmosphere (TOA irradiance was estimated through the construction of Langley plots on days when the sky was cloudless and clear. Changes in optical depth were monitored on a different day when clouds intermittently blocked the sun. The device demonstrated a measurement precision of 1.2% relative standard deviation for replicate photograph measurements (38 trials, 134 datum. However, when the accuracy of the method was assessed through using optical filters of known transmittance, a more substantial uncertainty was apparent in the data. Roughly 95% of replicate smart phone measured transmittances are expected to lie within ±11.6% of the true transmittance value. This uncertainty in transmission corresponds to an optical depth of approx. ±0.12-0.13 suggesting the smartphone sun photometer would be useful only in polluted areas that experience significant optical depths. The device can be used as a tool in the classroom to present how aerosols and gases effect atmospheric transmission. If improvements in measurement precision can be achieved, future work may allow monitoring networks to be developed in which citizen scientists submit acquired data from a variety of locations.

Ship Detection and Classification on Optical Remote Sensing Images Using Deep Learning

Directory of Open Access Journals (Sweden)

Liu Ying

2017-01-01

Full Text Available Ship detection and classification is critical for national maritime security and national defense. Although some SAR (Synthetic Aperture Radar image-based ship detection approaches have been proposed and used, they are not able to satisfy the requirement of real-world applications as the number of SAR sensors is limited, the resolution is low, and the revisit cycle is long. As massive optical remote sensing images of high resolution are available, ship detection and classification on theses images is becoming a promising technique, and has attracted great attention on applications including maritime security and traffic control. Some digital image processing methods have been proposed to detect ships in optical remote sensing images, but most of them face difficulty in terms of accuracy, performance and complexity. Recently, an autoencoder-based deep neural network with extreme learning machine was proposed, but it cannot meet the requirement of real-world applications as it only works with simple and small-scaled data sets. Therefore, in this paper, we propose a novel ship detection and classification approach which utilizes deep convolutional neural network (CNN as the ship classifier. The performance of our proposed ship detection and classification approach was evaluated on a set of images downloaded from Google Earth at the resolution 0.5m. 99% detection accuracy and 95% classification accuracy were achieved. In model training, 75× speedup is achieved on 1 Nvidia Titanx GPU.

Using Metaheuristic Algorithms for Solving a Hub Location Problem: Application in Passive Optical Network Planning

Directory of Open Access Journals (Sweden)

Masoud Rabbani

2017-02-01

Full Text Available Nowadays, fiber-optic due to having greater bandwidth and being more efficient compared with other similar technologies, are counted as one the most important tools for data transfer. In this article, an integrated mathematical model for a three-level fiber-optic distribution network with consideration of simultaneous backbone and local access networks is presented in which the backbone network is a ring and the access networks has a star-star topology. The aim of the model is to determine the location of the central offices and splitters, how connections are made between central offices, and allocation of each demand node to a splitter or central office in a way that the wiring cost of fiber optical and concentrator installation are minimized. Moreover, each user’s desired bandwidth should be provided efficiently. Then, the proposed model is validated by GAMS software in small-sized problems, afterwards the model is solved by two meta-heuristic methods including differential evolution (DE and genetic algorithm (GA in large-scaled problems and the results of two algorithms are compared with respect to computational time and objective function obtained value. Finally, a sensitivity analysis is provided. Keyword: Fiber-optic, telecommunication network, hub-location, passive splitter, three-level network.

Virtual and remote experiments for radiometric and photometric measurements

International Nuclear Information System (INIS)

Thoms, L-J; Girwidz, R

2017-01-01

The analysis of spectra is fundamental to our modern understanding of wave optics and colour perception. Since spectrometers are expensive, and accurate calibration is necessary to achieve high quality spectra, we developed a remote lab on optical spectrometry. With this tool, students can carry out real experiments over the Internet. In this article the pros and cons of remote labs, the physical background of optical spectrometry, and the development and use of a radiometric remote lab for higher education are discussed. The remote lab is freely accessible to everyone at http://virtualremotelab.net. (paper)

Virtual and remote experiments for radiometric and photometric measurements

Science.gov (United States)

Thoms, L.-J.; Girwidz, R.

2017-09-01

The analysis of spectra is fundamental to our modern understanding of wave optics and colour perception. Since spectrometers are expensive, and accurate calibration is necessary to achieve high quality spectra, we developed a remote lab on optical spectrometry. With this tool, students can carry out real experiments over the Internet. In this article the pros and cons of remote labs, the physical background of optical spectrometry, and the development and use of a radiometric remote lab for higher education are discussed. The remote lab is freely accessible to everyone at http://virtualremotelab.net.

Communication Network Architectures Based on Ethernet Passive Optical Network for Offshore Wind Power Farms

Directory of Open Access Journals (Sweden)

Mohamed A. Ahmed

2016-03-01

Full Text Available Nowadays, with large-scale offshore wind power farms (WPFs becoming a reality, more efforts are needed to maintain a reliable communication network for WPF monitoring. Deployment topologies, redundancy, and network availability are the main items to enhance the communication reliability between wind turbines (WTs and control centers. Traditional communication networks for monitoring and control (i.e., supervisory control and data acquisition (SCADA systems using switched gigabit Ethernet will not be sufficient for the huge amount of data passing through the network. In this paper, the optical power budget, optical path loss, reliability, and network cost of the proposed Ethernet Passive Optical Network (EPON-based communication network for small-size offshore WPFs have been evaluated for five different network architectures. The proposed network model consists of an optical network unit device (ONU deployed on the WT side for collecting data from different internal networks. All ONUs from different WTs are connected to a central optical line terminal (OLT, placed in the control center. There are no active electronic elements used between the ONUs and the OLT, which reduces the costs and complexity of maintenance and deployment. As fiber access networks without any protection are characterized by poor reliability, three different protection schemes have been configured, explained, and discussed. Considering the cost of network components, the total implementation expense of different architectures with, or without, protection have been calculated and compared. The proposed network model can significantly contribute to the communication network architecture for next generation WPFs.

Remote sensing science for the Nineties; Proceedings of IGARSS '90 - 10th Annual International Geoscience and Remote Sensing Symposium, University of Maryland, College Park, May 20-24, 1990. Vols. 1, 2, & 3

Science.gov (United States)

1990-01-01

Various papers on remote sensing (RS) for the nineties are presented. The general topics addressed include: subsurface methods, radar scattering, oceanography, microwave models, atmospheric correction, passive microwave systems, RS in tropical forests, moderate resolution land analysis, SAR geometry and SNR improvement, image analysis, inversion and signal processing for geoscience, surface scattering, rain measurements, sensor calibration, wind measurements, terrestrial ecology, agriculture, geometric registration, subsurface sediment geology, radar modulation mechanisms, radar ocean scattering, SAR calibration, airborne radar systems, water vapor retrieval, forest ecosystem dynamics, land analysis, multisensor data fusion. Also considered are: geologic RS, RS sensor optical measurements, RS of snow, temperature retrieval, vegetation structure, global change, artificial intelligence, SAR processing techniques, geologic RS field experiment, stochastic modeling, topography and Digital Elevation model, SAR ocean waves, spaceborne lidar and optical, sea ice field measurements, millimeter waves, advanced spectroscopy, spatial analysis and data compression, SAR polarimetry techniques. Also discussed are: plant canopy modeling, optical RS techniques, optical and IR oceanography, soil moisture, sea ice back scattering, lightning cloud measurements, spatial textural analysis, SAR systems and techniques, active microwave sensing, lidar and optical, radar scatterometry, RS of estuaries, vegetation modeling, RS systems, EOS/SAR Alaska, applications for developing countries, SAR speckle and texture.

EVALUATION OF A FORMER LANDFILL SITE IN FORT COLLINS, COLORADO USING GROUND-BASED OPTICAL REMOTE SENSING TECHNOLOGY

Science.gov (United States)

This report details a measurement campaign conducted using the Radial Plume Mapping (RPM) method and optical remote sensing technologies to characterize fugitive emissions. This work was funded by EPA′s Monitoring and Measurement for the 21st Century Initiative, or 21M2. The si...

Remote Sensing of Submerged Aquatic Vegetation in a Shallow Non-Turbid River Using an Unmanned Aerial Vehicle

Directory of Open Access Journals (Sweden)

Kyle F. Flynn

2014-12-01

Full Text Available A passive method for remote sensing of the nuisance green algae Cladophora glomerata in rivers is presented using an unmanned aerial vehicle (UAV. Included are methods for UAV operation, lens distortion correction, image georeferencing, and spectral analysis to support algal cover mapping. Eighteen aerial photography missions were conducted over the summer of 2013 using an off-the-shelf UAV and three-band, wide-angle, red, green, and blue (RGB digital camera sensor. Images were post-processed, mosaicked, and georeferenced so automated classification and mapping could be completed. An adaptive cosine estimator (ACE and spectral angle mapper (SAM algorithm were used to complete the algal identification. Digital analysis of optical imagery correctly identified filamentous algae and background coverage 90% and 92% of the time, and tau coefficients were 0.82 and 0.84 for ACE and SAM, respectively. Thereafter, algal cover was characterized for a one-kilometer channel segment during each of the 18 UAV flights. Percent cover ranged from <5% to >50%, and increased immediately after vernal freshet, peaked in midsummer, and declined in the fall. Results indicate that optical remote sensing with UAV holds promise for completing spatially precise, and multi-temporal measurements of algae or submerged aquatic vegetation in shallow rivers with low turbidity and good optical transmission.

Performance analysis of bi-directional broadband passive optical network using erbium-doped fiber amplifier

Science.gov (United States)

Almalaq, Yasser; Matin, Mohammad A.

2014-09-01

The broadband passive optical network (BPON) has the ability to support high-speed data, voice, and video services to home and small businesses customers. In this work, the performance of bi-directional BPON is analyzed for both down and up streams traffic cases by the help of erbium doped fiber amplifier (EDFA). The importance of BPON is reduced cost. Because PBON uses a splitter the cost of the maintenance between the providers and the customers side is suitable. In the proposed research, BPON has been tested by the use of bit error rate (BER) analyzer. BER analyzer realizes maximum Q factor, minimum bit error rate, and eye height.

Electrochemical and optical characterisation of passive films on stainless steels

International Nuclear Information System (INIS)

Wijesighe, T L Sudesh L; Blackwood, D J

2006-01-01

The formation and breakdown of the passive film are mainly controlled by ionic and electronic transport processes; processes that are in turn controlled by the electronic properties of the film. Consequently a comprehensive understanding of mechanisms behind passivity and localised corrosion require a detailed perception of the electronic properties of the passive films together with compositional and structural information. As a step towards this goal the passive film on austenitic stainless steel, AISI 316L, formed in borate solution was characterised by in situ Raman spectroscopy and photocurrent spectroscopy coupled with electrochemical measurements. The composition, structure and semiconductivity of the passive films depended on the potential; Fe rich n-type oxide and a Cr rich p-type oxide dominated at more positive potentials and more negative potentials respectively whilst n-type dual layered film formed at intermediate potentials. Analyses of the bandgap determined for these oxides suggested their structures to be Fe 2 O 3 and a Fe-Cr spinel. This hypothesis was supported by the results of in situ Raman spectroscopy

Radio requestable passive SAW water content sensor

NARCIS (Netherlands)

Reindl, L.; Ruppel, C.C.W.; Kirmayr, A.; Stockhausen, N.; Hilhorst, M.A.; Balendonk, J.

2001-01-01

A new passive sensor for remote measurement of water content in sandy soil was designed, using a surface acoustic wave (SAW) reflective delay line. Information from this sensor can be obtained by an interrogation device via a radio link operating in the European 434-MHz industrial-scientific-medical

Optical and passivating properties of hydrogenated amorphous silicon nitride deposited by plasma enhanced chemical vapour deposition for application on silicon solar cells

Energy Technology Data Exchange (ETDEWEB)

Wight, Daniel Nilsen

2008-07-01

Within this thesis, several important subjects related to the use of amorphous silicon nitride made by plasma enhanced chemical vapour deposition as an anti-reflective coating on silicon solar cells are presented. The first part of the thesis covers optical simulations to optimise single and double layer anti-reflective coatings with respect to optical performance when situated on a silicon solar cell. The second part investigates the relationship between important physical properties of silicon nitride films when deposited under different conditions. The optical simulations were either based on minimising the reflectance off a silicon nitride/silicon wafer stack or maximising the transmittance through the silicon nitride into the silicon wafer. The former method allowed consideration of the reflectance off the back surface of the wafer, which occurs typically at wavelengths above 1000 nm due to the transparency of silicon at these wavelengths. However, this method does not take into consideration the absorption occurring in the silicon nitride, which is negligible at low refractive indexes but quite significant when the refractive index increases above 2.1. For high-index silicon nitride films, the latter method is more accurate as it considers both reflectance and absorbance in the film to calculate the transmittance into the Si wafer. Both methods reach similar values for film thickness and refractive index for optimised single layer anti-reflective coatings, due to the negligible absorption occurring in these films. For double layer coatings, though, the reflectance based simulations overestimated the optimum refractive index for the bottom layer, which would have lead to excessive absorption if applied to real anti-reflective coatings. The experimental study on physical properties for silicon nitride films deposited under varying conditions concentrated on the estimation of properties important for its applications, such as optical properties, passivation

Improving Oil Palm Classification in the Peruvian Amazon by Combining Active and Passive Remote Sensing Data

Science.gov (United States)

Gutierrez-Velez, V. H.; DeFries, R. S.

2011-12-01

Oil palm expansion has led to clearing of extensive forest areas in the tropics. However quantitative assessments of the magnitude of oil palm expansion to deforestation have been challenging due in large part to the limitations presented by conventional optical data sets for discriminating plantations from forests and other tree cover vegetations. Recently available information from active remote sensors has opened the possibility of using these data sources to overcome these limitations. The purpose of this analysis is to evaluate the accuracy of oil palm classification when using ALOS/PALSAR active satellite data in conjunction with Landsat information, compared to the use of Landsat data only. The analysis takes place in a focused region around the city of Pucallpa in the Ucayali province of the Peruvian Amazon for the year 2010. Oil palm plantations were separated in five categories consisting of four age classes (0-3, 3-5, 5-10 and > 10 yrs) and an additional class accounting for degraded plantations older than 15 yr. Other land covers were water bodies, unvegetated land, short and tall grass, fallow, secondary vegetation, and forest. Classifications were performed using random forests. Training points for calibration and validation consisted of 411 polygons measured in areas representative of the land covers of interest and totaled 6,367 ha. Overall classification accuracy increased from 89.9% using only Landsat data sets to 94.3% using both Landast and ALOS/PALSAR. Both user's and producer's accuracy increased in all classes when using both data sets except for producer's accuracy in short grass which decreased by 1%. The largest increase in user's accuracy was obtained in oil palm plantations older than 10 years from 62 to 80% while producer's accuracy improved the most in plantations in age class 3-5 from 63 to 80%. Results demonstrate the suitability of data from ALOS/PALSAR and other active remote sensors to improve classification of oil palm

Laser based analysis using a passively Q-switched laser employing analysis electronics and a means for detecting atomic optical emission of the laser media

Science.gov (United States)

Woodruff, Steven D.; Mcintyre, Dustin L.

2016-03-29

A device for Laser based Analysis using a Passively Q-Switched Laser comprising an optical pumping source optically connected to a laser media. The laser media and a Q-switch are positioned between and optically connected to a high reflectivity mirror (HR) and an output coupler (OC) along an optical axis. The output coupler (OC) is optically connected to the output lens along the optical axis. A means for detecting atomic optical emission comprises a filter and a light detector. The optical filter is optically connected to the laser media and the optical detector. A control system is connected to the optical detector and the analysis electronics. The analysis electronics are optically connected to the output lens. The detection of the large scale laser output production triggers the control system to initiate the precise timing and data collection from the detector and analysis.

RFI and Remote Sensing of the Earth from Space

Science.gov (United States)

Le Vine, D. M.; Johnson, J. T.; Piepmeier, J.

2016-01-01

Passive microwave remote sensing of the Earth from space provides information essential for understanding the Earth's environment and its evolution. Parameters such as soil moisture, sea surface temperature and salinity, and profiles of atmospheric temperature and humidity are measured at frequencies determined by the physics (e.g. sensitivity to changes in desired parameters) and by the availability of suitable spectrum free from interference. Interference from manmade sources (radio frequency interference) is an impediment that in many cases limits the potential for accurate measurements from space. A review is presented here of the frequencies employed in passive microwave remote sensing of the Earth from space and the associated experience with RFI.

Signal Processing Algorithms for Down-Stream Traffic in Next Generation 10 Gbit/s Fixed-Grid Passive Optical Networks

Directory of Open Access Journals (Sweden)

Rameez Asif

2014-01-01

Full Text Available We have analyzed the impact of digital and optical signal processing algorithms, that is, Volterra equalization (VE, digital backpropagation (BP, and optical phase conjugation with nonlinearity module (OPC-NM, in next generation 10 Gbit/s (also referred to as XG DP-QPSK long haul WDM (fixed-grid passive optical network (PON without midspan repeaters over 120 km standard single mode fiber (SMF link for downstream signals. Due to the compensation of optical Kerr effects, the sensitivity penalty is improved by 2 dB by implementing BP algorithm, 1.5 dB by VE algorithm, and 2.69 dB by OPC-NM. Moreover, with the implementation of NL equalization technique, we are able to get the transmission distance of 126.6 km SMF for the 1 : 1024 split ratio at 5 GHz channel spacing in the nonlinear region.

Estimation of areal soil water content through microwave remote sensing

NARCIS (Netherlands)

Oevelen, van P.J.

2000-01-01

In this thesis the use of microwave remote sensing to estimate soil water content is investigated. A general framework is described which is applicable to both passive and active microwave remote sensing of soil water content. The various steps necessary to estimate areal soil water content

Optical remote sensing for monitoring flying mosquitoes, gender identification and discussion on species identification

Science.gov (United States)

Genoud, Adrien P.; Basistyy, Roman; Williams, Gregory M.; Thomas, Benjamin P.

2018-03-01

Mosquito-borne diseases are a major challenge for Human health as they affect nearly 700 million people every year and result in over 1 million deaths. Reliable information on the evolution of population and spatial distribution of key insects species is of major importance in the development of eco-epidemiologic models. This paper reports on the remote characterization of flying mosquitoes using a continuous-wave infrared optical remote sensing system. The system is setup in a controlled environment to mimic long-range lidars, mosquitoes are free flying at a distance of 4 m from the collecting optics. The wing beat frequency is retrieved from the backscattered light from mosquitoes transiting through the laser beam. A total of 427 transit signals have been recorded from three mosquito species, males and females. Since the mosquito species and gender are known a priori, we investigate the use of wing beat frequency as the sole predictor variable for two Bayesian classifications: gender alone (two classes) and species/gender (six classes). The gender of each mosquito is retrieved with a 96.5% accuracy while the species/gender of mosquitoes is retrieved with a 62.3% accuracy. Known to be an efficient mean to identify insect family, we discuss the limitations of using wing beat frequency alone to identify insect species.

Remote sensing of stratospheric O3 and NO2 using a portable and compact DOAS spectrometer

International Nuclear Information System (INIS)

Raponi, M M; Wolfram, E; Quel, E J; Jimenez, R; Tocho, J O

2011-01-01

The use of passive and active remote sensing systems has largely contributed to advance our understanding of important atmospheric phenomena. Here we present a compact and portable passive DOAS (Differential Optical Absorption Spectroscopy) system, developed for measuring the vertical column density (VCD) of multiple atmospheric trace gases. We highlight the main characteristics of the system components: a mini-spectrometer (HR4000, Ocean Optics), two optical fibers (400 μm of core, 6 m and 25 cm of longitude), an external shutter and the control/data processing software. Nitrogen dioxide (NO 2 ) and ozone (O 3 ) VCDs are derived from solar spectra acquired during twilights (87 0 - 91 0 zenithal angles) using the DOAS technique. The analysis is carried out by solving the Beer-Lambert-Bouger (BLB) law for the main atmospheric absorbers at selected wavelength ranges. The algorithm minimizes the fitting residuals to the BLB law, having as unknown the slant column density (SCD) of the species to determine. We present measurements carried out at the Marambio Antarctic Base (64 0 14' 25'' S; 56 0 37' 21'' W, 197 m asl) during January - February 2008. In addition, we compare our results with co-located measurements performed with EVA, a visible absorption spectrometer of Instituto Nacional de Tecnica Aeroespacial (INTA, Spain), a Dobson spectrophotometer of Servicio Meteorologico Nacional (SMN, Argentine) and the Ozone Monitoring Instrument (OMI), on board AURA satellite.

MeerKAT time and frequency reference optical network: Preliminary design analysis

Directory of Open Access Journals (Sweden)

Enoch K. Rotich Kipnoo

2017-05-01

Full Text Available The MeerKAT telescope is a precursor to the Square Kilometre Array, which will rely on optical fibres to link the telescope receivers to a central processor point. The main aspects to consider for the fibre transport are astronomical data transmission as well as timing, monitoring and control. The astronomical data streams from individual dishes to a central building, while the clock signal is distributed from a central point to remote dishes in the telescope array. The MeerKAT telescope, for instance, demands highly accurate and stable clock distribution over up to 12 km of optical fibre to remote dishes. The clock distribution is required for digitisation of astronomical signals. Phase stability is thus critical both for short-term and long-term requirements. In this work, we focused on the short-term stability. Phase noise measurements were performed on optical transmitters used to distribute the clock signals so as to ascertain their contribution to the overall clock jitter of the system. A maximum jitter requirement of 130 fs for a 1.712-GHz clock signal for MeerKAT time and reference is achieved using a distributed feedback laser. We found that with optimised modulation depth, additional passive optical components in the link do not significantly degrade the phase noise response. A distributed feedback laser was proven to be a suitable optical source that will meet the performance and link budget requirements for the MeerKAT telescope.

A review on substances and processes relevant for optical remote sensing of extremely turbid marine areas, with a focus on the Wadden Sea

NARCIS (Netherlands)

Hommersom, A.; Wernand, M.R.; Peters, S.W.M.; de Boer, J.

2010-01-01

The interpretation of optical remote sensing data of estuaries and tidal flat areas is hampered by optical complexity and often extreme turbidity. Extremely high concentrations of suspended matter, chlorophyll and dissolved organic matter, local differences, seasonal and tidal variations and

Non-invasive assessment of hemispheric language dominance by optical topography during a brief passive listening test: a pilot study.

Science.gov (United States)

Bembich, Stefano; Demarini, Sergio; Clarici, Andrea; Massaccesi, Stefano; Grasso, Domenico Loenardo

2011-12-01

The Wada test is usually used for pre-surgical assessment of language lateralization. Considering its invasiveness and risk of complications, alternative methods have been proposed but they are not always applicable to non-cooperative patients. In this study we explored the possibility of using optical topography (OT)--a multichannel near-infrared system--for non-invasive assessment of hemispheric language dominance during passive listening. Cortical activity was monitored in a sample of healthy, adult Italian native speakers, all right-handed. We assessed changes in oxy-haemoglobin concentration in temporal, parietal and posterior frontal lobes during a passive listening of bi-syllabic words and vowel-consonant-vowel syllables lasting less then 3 minutes. Activated channels were identified by t tests. Left hemisphere showed significant activity only during the passive listening of bi-syllabic words. Specifically, the superior temporal gyrus, the supramarginal gyrus and the posterior inferior parietal lobe were activated. During passive listening of bi-syllabic words, right handed healthy adults showed a significant activation in areas already known to be involved in speech comprehension. Although more research is needed, OT proved to be a promising alternative to the Wada test for non-invasive assessment of hemispheric language lateralization, even if using a particularly brief trial, which has been designed for future applications with non-cooperative subjects.

An Optical Fibre Depth (Pressure) Sensor for Remote Operated Vehicles in Underwater Applications

Science.gov (United States)

Duraibabu, Dinesh Babu; Poeggel, Sven; Omerdic, Edin; Capocci, Romano; Lewis, Elfed; Newe, Thomas; Leen, Gabriel; Toal, Daniel; Dooly, Gerard

2017-01-01

A miniature sensor for accurate measurement of pressure (depth) with temperature compensation in the ocean environment is described. The sensor is based on an optical fibre Extrinsic Fabry-Perot interferometer (EFPI) combined with a Fibre Bragg Grating (FBG). The EFPI provides pressure measurements while the Fibre Bragg Grating (FBG) provides temperature measurements. The sensor is mechanically robust, corrosion-resistant and suitable for use in underwater applications. The combined pressure and temperature sensor system was mounted on-board a mini remotely operated underwater vehicle (ROV) in order to monitor the pressure changes at various depths. The reflected optical spectrum from the sensor was monitored online and a pressure or temperature change caused a corresponding observable shift in the received optical spectrum. The sensor exhibited excellent stability when measured over a 2 h period underwater and its performance is compared with a commercially available reference sensor also mounted on the ROV. The measurements illustrates that the EFPI/FBG sensor is more accurate for depth measurements (depth of ~0.020 m). PMID:28218727

24-channel dual microcontroller-based voltage controller for ion optics remote control

Science.gov (United States)

Bengtsson, L.

2018-05-01

The design of a 24-channel voltage control instrument for Wenzel Elektronik N1130 NIM modules is described. This instrument is remote controlled from a LabVIEW GUI on a host Windows computer and is intended for ion optics control in electron affinity measurements on negative ions at the CERN-ISOLDE facility. Each channel has a resolution of 12 bits and has a normally distributed noise with a standard deviation of <1 mV. The instrument is designed as a standard 2-unit NIM module where the electronic hardware consists of a printed circuit board with two asynchronously operating microcontrollers.

New radiological material detection technologies for nuclear forensics: Remote optical imaging and graphene-based sensors.

Energy Technology Data Exchange (ETDEWEB)

Harrison, Richard Karl [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Martin, Jeffrey B. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Wiemann, Dora K. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Choi, Junoh [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Howell, Stephen W. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2015-09-01

We developed new detector technologies to identify the presence of radioactive materials for nuclear forensics applications. First, we investigated an optical radiation detection technique based on imaging nitrogen fluorescence excited by ionizing radiation. We demonstrated optical detection in air under indoor and outdoor conditions for alpha particles and gamma radiation at distances up to 75 meters. We also contributed to the development of next generation systems and concepts that could enable remote detection at distances greater than 1 km, and originated a concept that could enable daytime operation of the technique. A second area of research was the development of room-temperature graphene-based sensors for radiation detection and measurement. In this project, we observed tunable optical and charged particle detection, and developed improved devices. With further development, the advancements described in this report could enable new capabilities for nuclear forensics applications.

Microwave Remote Sensing Modeling of Ocean Surface Salinity and Winds Using an Empirical Sea Surface Spectrum

Science.gov (United States)

Yueh, Simon H.

2004-01-01

Active and passive microwave remote sensing techniques have been investigated for the remote sensing of ocean surface wind and salinity. We revised an ocean surface spectrum using the CMOD-5 geophysical model function (GMF) for the European Remote Sensing (ERS) C-band scatterometer and the Ku-band GMF for the NASA SeaWinds scatterometer. The predictions of microwave brightness temperatures from this model agree well with satellite, aircraft and tower-based microwave radiometer data. This suggests that the impact of surface roughness on microwave brightness temperatures and radar scattering coefficients of sea surfaces can be consistently characterized by a roughness spectrum, providing physical basis for using combined active and passive remote sensing techniques for ocean surface wind and salinity remote sensing.

Passive infrared motion sensing technology

International Nuclear Information System (INIS)

Doctor, A.P.

1994-01-01

In the last 10 years passive IR based (8--12 microns) motion sensing has matured to become the dominant method of volumetric space protection and surveillance. These systems currently cost less than $25 to produce and yet use traditionally expensive IR optics, filters, sensors and electronic circuitry. This IR application is quite interesting in that the volumes of systems produced and the costs and performance level required prove that there is potential for large scale commercial applications of IR technology. This paper will develop the basis and principles of operation of a staring motion sensor system using a technical approach. A model for the motion of the target is developed and compared to the background. The IR power difference between the target and the background as well as the optical requirements are determined from basic principles and used to determine the performance of the system. Low cost reflective and refractive IR optics and bandpass IR filters are discussed. The pyroelectric IR detector commonly used is fully discussed and characterized. Various schemes for ''false alarms'' have been developed and are also explained. This technology is also used in passive IR based motion sensors for other applications such as lighting control. These applications are also discussed. In addition the paper will discuss new developments in IR surveillance technology such as the use of linear motion sensing arrays. This presentation can be considered a ''primer'' on the art of Passive IR Motion Sensing as applied to Surveillance Technology

SAW passive wireless sensor-RFID tags with enhanced range, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — This proposal describes the development of passive wireless surface acoustic wave (SAW) RFID sensor-tags with enhanced range for remote monitoring of large groups of...

Space-Based CO2 Active Optical Remote Sensing using 2-μm Triple-Pulse IPDA Lidar

Science.gov (United States)

Singh, Upendra; Refaat, Tamer; Ismail, Syed; Petros, Mulugeta

2017-04-01

Sustained high-quality column CO2 measurements from space are required to improve estimates of regional and global scale sources and sinks to attribute them to specific biogeochemical processes for improving models of carbon-climate interactions and to reduce uncertainties in projecting future change. Several studies show that space-borne CO2 measurements offer many advantages particularly over high altitudes, tropics and southern oceans. Current satellite-based sensing provides rapid CO2 monitoring with global-scale coverage and high spatial resolution. However, these sensors are based on passive remote sensing, which involves limitations such as full seasonal and high latitude coverage, poor sensitivity to the lower atmosphere, retrieval complexities and radiation path length uncertainties. CO2 active optical remote sensing is an alternative technique that has the potential to overcome these limitations. The need for space-based CO2 active optical remote sensing using the Integrated Path Differential Absorption (IPDA) lidar has been advocated by the Advanced Space Carbon and Climate Observation of Planet Earth (A-Scope) and Active Sensing of CO2 Emission over Nights, Days, and Seasons (ASCENDS) studies in Europe and the USA. Space-based IPDA systems can provide sustained, high precision and low-bias column CO2 in presence of thin clouds and aerosols while covering critical regions such as high latitude ecosystems, tropical ecosystems, southern ocean, managed ecosystems, urban and industrial systems and coastal systems. At NASA Langley Research Center, technology developments are in progress to provide high pulse energy 2-μm IPDA that enables optimum, lower troposphere weighted column CO2 measurements from space. This system provides simultaneous ranging; information on aerosol and cloud distributions; measurements over region of broken clouds; and reduces influences of surface complexities. Through the continual support from NASA Earth Science Technology Office

Enhanced Codeset Passive Wireless SAW Sensor-Tags and System, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — The proposed project will develop a set of at least 100 passive wireless surface acoustic wave (SAW) RFID sensor-tags for near-simultaneous remote monitoring of...

All-Optical Frequency Modulated High Pressure MEMS Sensor for Remote and Distributed Sensing

DEFF Research Database (Denmark)

Reck, Kasper; Thomsen, Erik Vilain; Hansen, Ole

2011-01-01

We present the design, fabrication and characterization of a new all-optical frequency modulated pressure sensor. Using the tangential strain in a circular membrane, a waveguide with an integrated nanoscale Bragg grating is strained longitudinally proportional to the applied pressure causing...... a shift in the Bragg wavelength. The simple and robust design combined with the small chip area of 1 × 1.8 mm2 makes the sensor ideally suited for remote and distributed sensing in harsh environments and where miniaturized sensors are required. The sensor is designed for high pressure applications up...

Software defined multi-OLT passive optical network for flexible traffic allocation

Science.gov (United States)

Zhang, Shizong; Gu, Rentao; Ji, Yuefeng; Zhang, Jiawei; Li, Hui

2016-10-01

With the rapid growth of 4G mobile network and vehicular network services mobile terminal users have increasing demand on data sharing among different radio remote units (RRUs) and roadside units (RSUs). Meanwhile, commercial video-streaming, video/voice conference applications delivered through peer-to-peer (P2P) technology are still keep on stimulating the sharp increment of bandwidth demand in both business and residential subscribers. However, a significant issue is that, although wavelength division multiplexing (WDM) and orthogonal frequency division multiplexing (OFDM) technology have been proposed to fulfil the ever-increasing bandwidth demand in access network, the bandwidth of optical fiber is not unlimited due to the restriction of optical component properties and modulation/demodulation technology, and blindly increase the wavelength cannot meet the cost-sensitive characteristic of the access network. In this paper, we propose a software defined multi-OLT PON architecture to support efficient scheduling of access network traffic. By introducing software defined networking technology and wavelength selective switch into TWDM PON system in central office, multiple OLTs can be considered as a bandwidth resource pool and support flexible traffic allocation for optical network units (ONUs). Moreover, under the configuration of the control plane, ONUs have the capability of changing affiliation between different OLTs under different traffic situations, thus the inter-OLT traffic can be localized and the data exchange pressure of the core network can be released. Considering this architecture is designed to be maximum following the TWDM PON specification, the existing optical distribution network (ODN) investment can be saved and conventional EPON/GPON equipment can be compatible with the proposed architecture. What's more, based on this architecture, we propose a dynamic wavelength scheduling algorithm, which can be deployed as an application on control plane

Advances in hybrid optics physical sensors for extreme environments

Science.gov (United States)

Riza, Nabeel A.

2010-04-01

Highlighted are novel innovations in hybrid optical design physical sensors for extreme environments. Various hybrid design compositions are proposed that are suited for a particular sensor application. Examples includes combining freespace (wireless) and fiber-optics (wired) for gas turbine sensing and combining single crystal and sintered Silicon Carbide (SiC) materials for robust extreme environment Coefficent of Thermal Expansion (CTE) matched frontend probe design. Sensor signal processing also includes the hybrid theme where for example Black-Body radiation thermometry (pyrometry) is combined with laser interferometry to provide extreme temperature measurements. The hybrid theme also operates on the optical device level where a digital optical device such as a Digital Micromirror Device (DMD) is combined with an analog optical device such as an Electronically Controlled Variable Focal Length Lens (ECVFL) to deliver a smart and compressive Three Dimensional (3-D) imaging sensor for remote scene and object shape capture including both ambient light (passive) mode and active laser targeting and receive processing. Within a device level, the hybrid theme also operates via combined analog and digital control such as within a wavelength-coded variable optical delay line. These powerful hybrid design optical sensors have numerous applications in engineering and science applications from the military to the commercial/industrial sectors.

Investigation of remote sensing scale up for hot cell waste tank applications. CPAC optical moisture monitoring

International Nuclear Information System (INIS)

Jones, P.L.

1994-01-01

This report discusses work done to investigate the feasibility of using non-contact optical absorption to remotely sense the surface moisture content of salt cake materials. Optical measurements were made in a dimensionally scaled setup to investigate this technique for in-situ waste tank applications. Moisture measurements were obtained from BY-104 simulant samples with 0 wt%, 10 wt%, and 20 wt% moisture content using the back-scattered light from a pulsed infrared optical parametric converter (OPC) laser source operating from 1.51 to 2.12 micron. An InGaAs detector, with 0.038 steradian solid angle (hemisphere = 6.28 steradians) collection angle was used to detect the back-scattered light. This work indicated that there was sufficient back-scatter from the BY-104 material to provide an indication of the surface moisture content

Quantum-Noise-Limited Sensitivity Enhancement of a Passive Optical Cavity by a Fast-Light Medium

Science.gov (United States)

Smith, David D.; Luckay, H. A.; Chang, Hongrok; Myneni, Krishna

2016-01-01

We demonstrate for a passive optical cavity containing a dispersive atomic medium, the increase in scale factor near the critical anomalous dispersion is not cancelled by mode broadening or attenuation, resulting in an overall increase in the predicted quantum-noise-limited sensitivity. Enhancements of over two orders of magnitude are measured in the scale factor, which translates to greater than an order-of-magnitude enhancement in the predicted quantum-noise-limited measurement precision, by temperature tuning a low-pressure vapor of non-interacting atoms in a low-finesse cavity close to the critical anomalous dispersion condition. The predicted enhancement in sensitivity is confirmed through Monte-Carlo numerical simulations.

Quantum-Noise-Limited Sensitivity-Enhancement of a Passive Optical Cavity by a Fast-Light Medium

Science.gov (United States)

Smith, David D.; Luckay, H. A.; Chang, Hongrok; Myneni, Krishna

2016-01-01

We demonstrate for a passive optical cavity containing an intracavity dispersive atomic medium, the increase in scale factor near the critical anomalous dispersion is not cancelled by mode broadening or attenuation, resulting in an overall increase in the predicted quantum-noiselimited sensitivity. Enhancements of over two orders of magnitude are measured in the scale factor, which translates to greater than an order-of-magnitude enhancement in the predicted quantumnoise- limited measurement precision, by temperature tuning a low-pressure vapor of noninteracting atoms in a low-finesse cavity close to the critical anomalous dispersion condition. The predicted enhancement in sensitivity is confirmed through Monte-Carlo numerical simulations.

Optical bistability controlling light with light

CERN Document Server

Gibbs, Hyatt

1985-01-01

Optical Bistability: Controlling Light with Light focuses on optical bistability in nonlinear optical systems. Emphasis is on passive (non-laser) systems that exhibit reversible bistability with input intensity as the hysteresis variable, along with the physics and the potential applications of such systems for nonlinear optical signal processing. This book consists of seven chapters and begins with a historical overview of optical bistability in lasers and passive systems. The next chapter describes steady-state theories of optical bistability, including the Bonifacio-Lugiato model, as we

Probability theory for 3-layer remote sensing radiative transfer model: univariate case.

Science.gov (United States)

Ben-David, Avishai; Davidson, Charles E

2012-04-23

A probability model for a 3-layer radiative transfer model (foreground layer, cloud layer, background layer, and an external source at the end of line of sight) has been developed. The 3-layer model is fundamentally important as the primary physical model in passive infrared remote sensing. The probability model is described by the Johnson family of distributions that are used as a fit for theoretically computed moments of the radiative transfer model. From the Johnson family we use the SU distribution that can address a wide range of skewness and kurtosis values (in addition to addressing the first two moments, mean and variance). In the limit, SU can also describe lognormal and normal distributions. With the probability model one can evaluate the potential for detecting a target (vapor cloud layer), the probability of observing thermal contrast, and evaluate performance (receiver operating characteristics curves) in clutter-noise limited scenarios. This is (to our knowledge) the first probability model for the 3-layer remote sensing geometry that treats all parameters as random variables and includes higher-order statistics. © 2012 Optical Society of America

Deterministic joint remote preparation of an equatorial hybrid state via high-dimensional Einstein-Podolsky-Rosen pairs: active versus passive receiver

Science.gov (United States)

Bich, Cao Thi; Dat, Le Thanh; Van Hop, Nguyen; An, Nguyen Ba

2018-04-01

Entanglement plays a vital and in many cases non-replaceable role in the quantum network communication. Here, we propose two new protocols to jointly and remotely prepare a special so-called bipartite equatorial state which is hybrid in the sense that it entangles two Hilbert spaces with arbitrary different dimensions D and N (i.e., a type of entanglement between a quDit and a quNit). The quantum channels required to do that are however not necessarily hybrid. In fact, we utilize four high-dimensional Einstein-Podolsky-Rosen pairs, two of which are quDit-quDit entanglements, while the other two are quNit-quNit ones. In the first protocol the receiver has to be involved actively in the process of remote state preparation, while in the second protocol the receiver is passive as he/she needs to participate only in the final step for reconstructing the target hybrid state. Each protocol meets a specific circumstance that may be encountered in practice and both can be performed with unit success probability. Moreover, the concerned equatorial hybrid entangled state can also be jointly prepared for two receivers at two separated locations by slightly modifying the initial particles' distribution, thereby establishing between them an entangled channel ready for a later use.

Wide-area remote-sensing system of pollution and gas dispersal by near-infrared absorption based on low-loss optical fiber network

Science.gov (United States)

Inaba, H.

1986-01-01

An all optical remote sensing system utilizing long distance, ultralow loss optical fiber networks is studied and discussed for near infrared absorption measurements of combustible and/or explosive gases such as CH4 and C3H8 in our environment, including experimental results achieved in a diameter more than 20 km. The use of a near infrared wavelength range is emphasized.

Electrical and optical characterization of surface passivation in GaAs nanowires.

Science.gov (United States)

Chang, Chia-Chi; Chi, Chun-Yung; Yao, Maoqing; Huang, Ningfeng; Chen, Chun-Chung; Theiss, Jesse; Bushmaker, Adam W; Lalumondiere, Stephen; Yeh, Ting-Wei; Povinelli, Michelle L; Zhou, Chongwu; Dapkus, P Daniel; Cronin, Stephen B

2012-09-12

We report a systematic study of carrier dynamics in Al(x)Ga(1-x)As-passivated GaAs nanowires. With passivation, the minority carrier diffusion length (L(diff)) increases from 30 to 180 nm, as measured by electron beam induced current (EBIC) mapping, and the photoluminescence (PL) lifetime increases from sub-60 ps to 1.3 ns. A 48-fold enhancement in the continuous-wave PL intensity is observed on the same individual nanowire with and without the Al(x)Ga(1-x)As passivation layer, indicating a significant reduction in surface recombination. These results indicate that, in passivated nanowires, the minority carrier lifetime is not limited by twin stacking faults. From the PL lifetime and minority carrier diffusion length, we estimate the surface recombination velocity (SRV) to range from 1.7 × 10(3) to 1.1 × 10(4) cm·s(-1), and the minority carrier mobility μ is estimated to lie in the range from 10.3 to 67.5 cm(2) V(-1) s(-1) for the passivated nanowires.

Future European and Japanese remote-sensing sensors and programs; Proceedings of the Meeting, Orlando, FL, Apr. 1, 2, 1991

Science.gov (United States)

Slater, Philip N.

Consideration is given to the METEOSAT second-generation program, the ESA earth observation polar platform program, a new satellite for a climatology study in the tropics, a medium-resolution imaging spectrometer, a Michelson interferometer for passive atmosphere sounding, an optical mapping instrument, an optical sensor system for Japanese earth resources satellite 1, a synthetic aperture radar of JERS-1, an ocean color and temperature scanner for Advanced Earth-Observing Satellite (ADEOS), an interferometric monitor for greenhouse gasses for ADEOS. Attention is also given to Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) for EOS-A, short-wave infrared subsystem design status of ASTER, ASTER calibration concept, Japanese polar orbit platform program, and airborne and spaceborne thermal multispectral remote sensing. (For individual items see A93-20427 to A93-20452)

The development of remote teaching laboratory access software for multi-slice computed optical tomography for use in undergraduate nuclear education

International Nuclear Information System (INIS)

Price, T.J.; Nichita, E.

2013-01-01

Internet-based laboratory exercises were developed for a course on biomedical imaging at the University of Ontario Institute of Technology. These exercises used a multi-slice computed optical tomography machine named DeskCAT to instruct students on the principals of computed tomography. User management software was developed which enabled course instructors to quickly set up a computer to accept a series of scheduled remote user connections for a classroom. Laboratory exercises using the DeskCAT machine were developed to be conducted remotely. (author)

The development of remote teaching laboratory access software for multi-slice computed optical tomography for use in undergraduate nuclear education

Energy Technology Data Exchange (ETDEWEB)

Price, T.J.; Nichita, E., E-mail: Terry.Price@gmail.com [Univ. of Ontario Inst. of Technology, Oshawa, Ontario (Canada)

2013-07-01

Internet-based laboratory exercises were developed for a course on biomedical imaging at the University of Ontario Institute of Technology. These exercises used a multi-slice computed optical tomography machine named DeskCAT to instruct students on the principals of computed tomography. User management software was developed which enabled course instructors to quickly set up a computer to accept a series of scheduled remote user connections for a classroom. Laboratory exercises using the DeskCAT machine were developed to be conducted remotely. (author)

Development of remote laser welding technology

International Nuclear Information System (INIS)

Kim, Soo-Sung; Kim, Woong-Ki; Lee, Jung-Won; Yang, Myung-Seung; Park, Hyun-Soo

1999-01-01

Various welding processes are now available for end cap closure of nuclear fuel element such as TIG(Tungsten Inert Gas) welding, magnetic resistance welding and laser welding. Even though the resistance and TIG welding process are widely used for manufacturing of the commercial fuel elements, it can not be recommended for the remote seal welding of fuel element at PIE facility due to its complexity of the electrode alignment, difficulty in the replacement of parts in the remote manner and its large heat input for thin sheath. Therefore, Nd:YAG laser system using the optical fiber transmission was selected for Zircaloy-4 end cap welding. Remote laser welding apparatus is developed using a pulsed Nd:YAG laser of 500 watt average power with optical fiber transmission. The laser weldability is satisfactory in respect of the microstructures and mechanical properties comparing with the TIG and resistance welding. The optimum operation processes of laser welding and the optical fiber transmission system for hot cell operation in remote manner have been developed. (author)

Energy Efficiency in TDMA-Based Next-Generation Passive Optical Access Networks

KAUST Repository

Dhaini, Ahmad R.; Ho, Pin-Han; Shen, Gangxiang; Shihada, Basem

2014-01-01

Next-generation passive optical network (PON) has been considered in the past few years as a cost-effective broadband access technology. With the ever-increasing power saving concern, energy efficiency has been an important issue in its operations. In this paper, we propose a novel sleep-time sizing and scheduling framework for the implementation of green bandwidth allocation (GBA) in TDMA-PONs. The proposed framework leverages the batch-mode transmission feature of GBA to minimize the overhead due to frequent ONU on-off transitions. The optimal sleeping time sequence of each ONU is determined in every cycle without violating the maximum delay requirement. With multiple ONUs possibly accessing the shared media simultaneously, a collision may occur. To address this problem, we propose a new sleep-time sizing mechanism, namely Sort-And-Shift (SAS), in which the ONUs are sorted according to their expected transmission start times, and their sleep times are shifted to resolve any possible collision while ensuring maximum energy saving. Results show the effectiveness of the proposed framework and highlight the merits of our solutions.

Energy Efficiency in TDMA-Based Next-Generation Passive Optical Access Networks

KAUST Repository

Dhaini, Ahmad R.

2014-06-01

Next-generation passive optical network (PON) has been considered in the past few years as a cost-effective broadband access technology. With the ever-increasing power saving concern, energy efficiency has been an important issue in its operations. In this paper, we propose a novel sleep-time sizing and scheduling framework for the implementation of green bandwidth allocation (GBA) in TDMA-PONs. The proposed framework leverages the batch-mode transmission feature of GBA to minimize the overhead due to frequent ONU on-off transitions. The optimal sleeping time sequence of each ONU is determined in every cycle without violating the maximum delay requirement. With multiple ONUs possibly accessing the shared media simultaneously, a collision may occur. To address this problem, we propose a new sleep-time sizing mechanism, namely Sort-And-Shift (SAS), in which the ONUs are sorted according to their expected transmission start times, and their sleep times are shifted to resolve any possible collision while ensuring maximum energy saving. Results show the effectiveness of the proposed framework and highlight the merits of our solutions.

A review of the application of optical and radar remote sensing data fusion to land use mapping and monitoring

NARCIS (Netherlands)

Joshi, Neha; Baumann, Matthias; Ehammer, Andrea; Reiche, Johannes

2016-01-01

The wealth of complementary data available from remote sensing missions can hugely aid efforts towards accurately determining land use and quantifying subtle changes in land use management or intensity. This study reviewed 112 studies on fusing optical and radar data, which offer unique spectral

Diffuse reflectance spectroscopy for optical soft tissue differentiation as remote feedback control for tissue-specific laser surgery.

Science.gov (United States)

Stelzle, Florian; Tangermann-Gerk, Katja; Adler, Werner; Zam, Azhar; Schmidt, Michael; Douplik, Alexandre; Nkenke, Emeka

2010-04-01

Laser surgery does not provide haptic feedback for operating layer-by-layer and thereby preserving vulnerable anatomical structures like nerve tissue or blood vessels. Diffuse reflectance spectra can facilitate remote optical tissue differentiation. It is the aim of the study to use this technique on soft tissue samples, to set a technological basis for a remote optical feedback system for tissue-specific laser surgery. Diffuse reflectance spectra (wavelength range: 350-650 nm) of ex vivo types of soft tissue (a total of 10,800 spectra) of the midfacial region of domestic pigs were remotely measured under reduced environmental light conditions and analyzed in order to differentiate between skin, mucosa, muscle, subcutaneous fat, and nerve tissue. We performed a principal components (PC) analysis (PCA) to reduce the number of variables. Linear discriminant analysis (LDA) was utilized for classification. For the tissue differentiation, we calculated the specificity and sensitivity by receiver operating characteristic (ROC) analysis and the area under curve (AUC). Six PCs were found to be adequate for tissue differentiation with diffuse reflectance spectra using LDA. All of the types of soft tissue could be differentiated with high specificity and sensitivity. Only the tissue pairs nervous tissue/fatty tissue and nervous tissue/mucosa showed a decline of differentiation due to bio-structural similarity. However, both of these tissue pairs could still be differentiated with a specificity and sensitivity of more than 90%. Analyzing diffuse reflectance spectroscopy with PCA and LDA allows for remote differentiation of biological tissue. Considering the limitations of the ex vivo conditions, the obtained results are promising and set a basis for the further development of a feedback system for tissue-specific laser surgery. (c) 2010 Wiley-Liss, Inc.

Satellite Remote Sensing in Offshore Wind Energy

DEFF Research Database (Denmark)

Hasager, Charlotte Bay; Badger, Merete; Astrup, Poul

2013-01-01

Satellite remote sensing of ocean surface winds are presented with focus on wind energy applications. The history on operational and research-based satellite ocean wind mapping is briefly described for passive microwave, scatterometer and synthetic aperture radar (SAR). Currently 6 GW installed...

Energy-efficient orthogonal frequency division multiplexing-based passive optical network based on adaptive sleep-mode control and dynamic bandwidth allocation

Science.gov (United States)

Zhang, Chongfu; Xiao, Nengwu; Chen, Chen; Yuan, Weicheng; Qiu, Kun

2016-02-01

We propose an energy-efficient orthogonal frequency division multiplexing-based passive optical network (OFDM-PON) using adaptive sleep-mode control and dynamic bandwidth allocation. In this scheme, a bidirectional-centralized algorithm named the receiver and transmitter accurate sleep control and dynamic bandwidth allocation (RTASC-DBA), which has an overall bandwidth scheduling policy, is employed to enhance the energy efficiency of the OFDM-PON. The RTASC-DBA algorithm is used in an optical line terminal (OLT) to control the sleep mode of an optical network unit (ONU) sleep and guarantee the quality of service of different services of the OFDM-PON. The obtained results show that, by using the proposed scheme, the average power consumption of the ONU is reduced by ˜40% when the normalized ONU load is less than 80%, compared with the average power consumption without using the proposed scheme.

Design of a mutual authentication based on NTRUsign with a perturbation and inherent multipoint control protocol frames in an Ethernet-based passive optical network

Science.gov (United States)

Yin, Aihan; Ding, Yisheng

2014-11-01

Identity-related security issues inherently present in passive optical networks (PON) still exist in the current (1G) and next-generation (10G) Ethernet-based passive optical network (EPON) systems. We propose a mutual authentication scheme that integrates an NTRUsign digital signature algorithm with inherent multipoint control protocol (MPCP) frames over an EPON system between the optical line terminal (OLT) and optical network unit (ONU). Here, a primitive NTRUsign algorithm is significantly modified through the use of a new perturbation so that it can be effectively used for simultaneously completing signature and authentication functions on the OLT and the ONU sides. Also, in order to transmit their individual sensitive messages, which include public key, signature, and random value and so forth, to each other, we redefine three unique frames according to MPCP format frame. These generated messages can be added into the frames and delivered to each other, allowing the OLT and the ONU to go ahead with a mutual identity authentication process to verify their legal identities. Our simulation results show that this proposed scheme performs very well in resisting security attacks and has low influence on the registration efficiency to to-be-registered ONUs. A performance comparison with traditional authentication algorithms is also presented. To the best of our knowledge, no detailed design of mutual authentication in EPON can be found in the literature up to now.

Pattern Recognition in Optical Remote Sensing Data Processing

Science.gov (United States)

Kozoderov, Vladimir; Kondranin, Timofei; Dmitriev, Egor; Kamentsev, Vladimir

Computational procedures of the land surface biophysical parameters retrieval imply that modeling techniques are available of the outgoing radiation description together with monitoring techniques of remote sensing data processing using registered radiances between the related optical sensors and the land surface objects called “patterns”. Pattern recognition techniques are a valuable approach to the processing of remote sensing data for images of the land surface - atmosphere system. Many simplified codes of the direct and inverse problems of atmospheric optics are considered applicable for the imagery processing of low and middle spatial resolution. Unless the authors are not interested in the accuracy of the final information products, they utilize these standard procedures. The emerging necessity of processing data of high spectral and spatial resolution given by imaging spectrometers puts forward the newly defined pattern recognition techniques. The proposed tools of using different types of classifiers combined with the parameter retrieval procedures for the forested environment are maintained to have much wider applications as compared with the image features and object shapes extraction, which relates to photometry and geometry in pixel-level reflectance representation of the forested land cover. The pixel fraction and reflectance of “end-members” (sunlit forest canopy, sunlit background and shaded background for a particular view and solar illumination angle) are only a part in the listed techniques. It is assumed that each pixel views collections of the individual forest trees and the pixel-level reflectance can thus be computed as a linear mixture of sunlit tree tops, sunlit background (or understory) and shadows. Instead of these photometry and geometry constraints, the improved models are developed of the functional description of outgoing spectral radiation, in which such parameters of the forest canopy like the vegetation biomass density for

Passive and Self-Powered Autonomous Sensors for Remote Measurements

Directory of Open Access Journals (Sweden)

Mauro Serpelloni

2009-02-01

Full Text Available Autonomous sensors play a very important role in the environmental, structural, and medical fields. The use of this kind of systems can be expanded for several applications, for example in implantable devices inside the human body where it is impossible to use wires. Furthermore, they enable measurements in harsh or hermetic environments, such as under extreme heat, cold, humidity or corrosive conditions. The use of batteries as a power supply for these devices represents one solution, but the size, and sometimes the cost and unwanted maintenance burdens of replacement are important drawbacks. In this paper passive and self-powered autonomous sensors for harsh or hermetical environments without batteries are discussed. Their general architectures are presented. Sensing strategies, communication techniques and power management are analyzed. Then, general building blocks of an autonomous sensor are presented and the design guidelines that such a system must follow are given. Furthermore, this paper reports different proposed applications of autonomous sensors applied in harsh or hermetic environments: two examples of passive autonomous sensors that use telemetric communication are proposed, the first one for humidity measurements and the second for high temperatures. Other examples of self-powered autonomous sensors that use a power harvesting system from electromagnetic fields are proposed for temperature measurements and for airflow speeds.

Passive and self-powered autonomous sensors for remote measurements.

Science.gov (United States)

Sardini, Emilio; Serpelloni, Mauro

2009-01-01

Autonomous sensors play a very important role in the environmental, structural, and medical fields. The use of this kind of systems can be expanded for several applications, for example in implantable devices inside the human body where it is impossible to use wires. Furthermore, they enable measurements in harsh or hermetic environments, such as under extreme heat, cold, humidity or corrosive conditions. The use of batteries as a power supply for these devices represents one solution, but the size, and sometimes the cost and unwanted maintenance burdens of replacement are important drawbacks. In this paper passive and self-powered autonomous sensors for harsh or hermetical environments without batteries are discussed. Their general architectures are presented. Sensing strategies, communication techniques and power management are analyzed. Then, general building blocks of an autonomous sensor are presented and the design guidelines that such a system must follow are given. Furthermore, this paper reports different proposed applications of autonomous sensors applied in harsh or hermetic environments: two examples of passive autonomous sensors that use telemetric communication are proposed, the first one for humidity measurements and the second for high temperatures. Other examples of self-powered autonomous sensors that use a power harvesting system from electromagnetic fields are proposed for temperature measurements and for airflow speeds.

Remote handling in ZEPHYR

International Nuclear Information System (INIS)

Andelfinger, C.; Lackner, E.; Ulrich, M.; Weber, G.; Schilling, H.B.

1982-04-01

A conceptual design of the ZEPHYR building is described. The listed radiation data show that remote handling devices will be necessary in most areas of the building. For difficult repair and maintenance works it is intended to transfer complete units from the experimental hall to a hot cell which provides better working conditions. The necessary crane systems and other transport means are summarized as well as suitable commercially available manipulators and observation devices. The conept of automatic devices for cutting and welding and other operations inside the vacuum vessel and the belonging position control system is sketched. Guidelines for the design of passive components are set up in order to facilitate remote operation. (orig.)

Remote Optical Imagery of Obscured Objects in Low-Visibility Environments Using Parametric Amplification

Energy Technology Data Exchange (ETDEWEB)

Asher, R.B.; Bliss, D.E.; Cameron, S.M.; Hamil, R.A.

1998-10-14

The development of unconventional active optical sensors to remotely detect and spatially resolve suspected threats obscured by low-visibility observation conditions (adverse weather, clouds, dust, smoke, precipitation, etc.) is fundamental to maintaining tactical supremacy in the battlespace. In this report, the authors describe an innovative frequency-agile image intensifier technology based on time-gated optical parametic amplification (OPA) for enhanced light-based remote sensing through pervasive scattering and/or turbulent environments. Improved dynamic range characteristics derived from the amplified passband of the OPA receiver combined with temporal discrimination in the image capture process will offset radiant power extinction losses, while defeating the deugradative effects & multipath dispersion and ,diffuse backscatter noise along the line-of-sight on resultant image contrast and range resolution. Our approach extends the operational utility of the detection channel in existing laser radar systems by increasing sensitivity to low-level target reffectivities, adding ballistic rejection of scatter and clutter in the range coordinate, and introducing multispectral and polarization discrimination capability in a wavelen~h-tunable, high gain nonlinear optical component with strong potential for source miniaturization. A key advantage of integrating amplification and tlequency up-conversion functions within a phasematched three-wave mixing parametric device is the ability to petiorm background-free imaging with eye-safe or longer inilared illumination wavelengths (idler) less susceptible to scatter without sacrificing quantum efficiency in the detection process at the corresponding signal wavelength. We report benchmark laboratory experiments in which the OPA gating process has been successfidly demonstrated in both transillumination and reflection test geometries with extended pathlengths representative of realistic coastal sea water and cumulus cloud

Criteria for the optimal selection of remote sensing optical images to map event landslides

Science.gov (United States)

Fiorucci, Federica; Giordan, Daniele; Santangelo, Michele; Dutto, Furio; Rossi, Mauro; Guzzetti, Fausto

2018-01-01

Landslides leave discernible signs on the land surface, most of which can be captured in remote sensing images. Trained geomorphologists analyse remote sensing images and map landslides through heuristic interpretation of photographic and morphological characteristics. Despite a wide use of remote sensing images for landslide mapping, no attempt to evaluate how the image characteristics influence landslide identification and mapping exists. This paper presents an experiment to determine the effects of optical image characteristics, such as spatial resolution, spectral content and image type (monoscopic or stereoscopic), on landslide mapping. We considered eight maps of the same landslide in central Italy: (i) six maps obtained through expert heuristic visual interpretation of remote sensing images, (ii) one map through a reconnaissance field survey, and (iii) one map obtained through a real-time kinematic (RTK) differential global positioning system (dGPS) survey, which served as a benchmark. The eight maps were compared pairwise and to a benchmark. The mismatch between each map pair was quantified by the error index, E. Results show that the map closest to the benchmark delineation of the landslide was obtained using the higher resolution image, where the landslide signature was primarily photographical (in the landslide source and transport area). Conversely, where the landslide signature was mainly morphological (in the landslide deposit) the best mapping result was obtained using the stereoscopic images. Albeit conducted on a single landslide, the experiment results are general, and provide useful information to decide on the optimal imagery for the production of event, seasonal and multi-temporal landslide inventory maps.

Wave-optics modeling of the optical-transport line for passive optical stochastic cooling

Science.gov (United States)

Andorf, M. B.; Lebedev, V. A.; Piot, P.; Ruan, J.

2018-03-01

Optical stochastic cooling (OSC) is expected to enable fast cooling of dense particle beams. Transition from microwave to optical frequencies enables an achievement of stochastic cooling rates which are orders of magnitude higher than ones achievable with the classical microwave based stochastic cooling systems. A subsystemcritical to the OSC scheme is the focusing optics used to image radiation from the upstream "pickup" undulator to the downstream "kicker" undulator. In this paper, we present simulation results using wave-optics calculation carried out with the SYNCHROTRON RADIATION WORKSHOP (SRW). Our simulations are performed in support to a proof-of-principle experiment planned at the Integrable Optics Test Accelerator (IOTA) at Fermilab. The calculations provide an estimate of the energy kick received by a 100-MeV electron as it propagates in the kicker undulator and interacts with the electromagnetic pulse it radiated at an earlier time while traveling through the pickup undulator.

Light Optics for Optical Stochastic Cooling

Energy Technology Data Exchange (ETDEWEB)

Andorf, Matthew [NICADD, DeKalb; Lebedev, Valeri [Fermilab; Piot, Philippe [NICADD, DeKalb; Ruan, Jinhao [Fermilab

2016-06-01

In Optical Stochastic Cooling (OSC) radiation generated by a particle in a "pickup" undulator is amplified and transported to a downstream "kicker" undulator where it interacts with the same particle which radiated it. Fermilab plans to carry out both passive (no optical amplifier) and active (optical amplifier) tests of OSC at the Integrable Optics Test Accelerator (IOTA) currently in construction*. The performace of the optical system is analyzed with simulations in Synchrotron Radiation Workshop (SRW) accounting for the specific temporal and spectral properties of undulator radiation and being augmented to include dispersion of lens material.

Wave-Optics Modeling of the Optical-Transport Line for Passive Optical Stochastic Cooling

Energy Technology Data Exchange (ETDEWEB)

Andorf, M. B. [NICADD, DeKalb; Lebedev, V. A. [Fermilab; Piot, P. [Fermilab; Ruan, J. [Fermilab

2018-03-01

Optical stochastic cooling (OSC) is expected to enable fast cooling of dense particle beams. Transition from microwave to optical frequencies enables an achievement of stochastic cooling rates which are orders of magnitude higher than ones achievable with the classical microwave based stochastic cooling systems. A subsytem critical to the OSC scheme is the focusing optics used to image radiation from the upstream "pickup" undulator to the downstream "kicker" undulator. In this paper, we present simulation results using wave-optics calculation carried out with the {\\sc Synchrotron Radiation Workshop} (SRW). Our simulations are performed in support to a proof-of-principle experiment planned at the Integrable Optics Test Accelerator (IOTA) at Fermilab. The calculations provide an estimate of the energy kick received by a 100-MeV electron as it propagates in the kicker undulator and interacts with the electromagnetic pulse it radiated at an earlier time while traveling through the pickup undulator.

Technology of remote nuclear activity monitoring for national safeguards

International Nuclear Information System (INIS)

Kwack, Eun Ho; Kim, B. K.; Kim, J. S.; Yoon, W. K.; Kim, J. S.; Kim, J. S.; Cha, H. R.; Na, W. W.; Choi, Y. M.

2001-07-01

This project mainly focused on technical development on remote monitoring. It covers optical fiber scintillator to be used as NDA sensor to targets to be applied. Optical fiber scintillator was tested at the high radioactive environment. It is the first try in its kind for spent fuel measurement. It is confirmed that optical fiber sensor can be used for safeguards verification. Its feasibility for spent fuel storage silo at Wolsong reactor was studied. And to optimize remote transmission cost which can be regarded as a major barrier, virtual private network was studied for possible application for safeguards purpose. It can drastically reduce transmission cost and upgrade information surety. As target for remote monitoring, light water reactor and heavy water reactor were feasibly studied. Especially heavy water reactor has much potential for reduction of inspection efforts if remote monitoring is introduced. In overall remote monitoring can play a pivotal role to streamline safeguards inspection

Low-peak-to-average power ratio and low-complexity asymmetrically clipped optical orthogonal frequency-division multiplexing uplink transmission scheme for long-reach passive optical network.

Science.gov (United States)

Zhou, Ji; Qiao, Yaojun

2015-09-01

In this Letter, we propose a discrete Hartley transform (DHT)-spread asymmetrically clipped optical orthogonal frequency-division multiplexing (DHT-S-ACO-OFDM) uplink transmission scheme in which the multiplexing/demultiplexing process also uses the DHT algorithm. By designing a simple encoding structure, the computational complexity of the transmitter can be reduced from O(Nlog(2)(N)) to O(N). At the probability of 10(-3), the peak-to-average power ratio (PAPR) of 2-ary pulse amplitude modulation (2-PAM)-modulated DHT-S-ACO-OFDM is approximately 9.7 dB lower than that of 2-PAM-modulated conventional ACO-OFDM. To verify the feasibility of the proposed scheme, a 4-Gbit/s DHT-S-ACO-OFDM uplink transmission scheme with a 1∶64 way split has been experimentally implemented using 100-km standard single-mode fiber (SSMF) for a long-reach passive optical network (LR-PON).

High-order passive photonic temporal integrators.

Science.gov (United States)

Asghari, Mohammad H; Wang, Chao; Yao, Jianping; Azaña, José

2010-04-15

We experimentally demonstrate, for the first time to our knowledge, an ultrafast photonic high-order (second-order) complex-field temporal integrator. The demonstrated device uses a single apodized uniform-period fiber Bragg grating (FBG), and it is based on a general FBG design approach for implementing optimized arbitrary-order photonic passive temporal integrators. Using this same design approach, we also fabricate and test a first-order passive temporal integrator offering an energetic-efficiency improvement of more than 1 order of magnitude as compared with previously reported passive first-order temporal integrators. Accurate and efficient first- and second-order temporal integrations of ultrafast complex-field optical signals (with temporal features as fast as approximately 2.5ps) are successfully demonstrated using the fabricated FBG devices.

Passivation of black phosphorus saturable absorbers for reliable pulse formation of fiber lasers.

Science.gov (United States)

Na, Dongsoo; Park, Kichul; Park, Ki-Hwan; Song, Yong-Won

2017-11-24

Black phosphorus (BP) has attracted increasing attention due to its unique electrical properties. In addition, the outstanding optical nonlinearity of BP has been demonstrated in various ways. Its functionality as a saturable absorber, in particular, has been validated in demonstrations of passive mode-locked lasers. However, normally, the performance of BP is degraded eventually by both thermal and chemical damage in ambient conditions. The passivation of BP is the critical issue to guarantee a stable performance of the optical devices. We quantitatively characterized the mode-locked lasers operated by BP saturable absorbers with diversified passivation materials such as polydimethylsiloxane (PDMS) or Al 2 O 3 , considering the atomic structure of the materials, and therefore the hydro-permeability of the passivation layers. Unlike the BP layers without passivation, we demonstrated that the Al 2 O 3 -passivated BP layer was protected from the surface oxidation reaction in the long-term, and the PDMS-passivated one had a short-term blocking effect. The quantitative analysis showed that the time-dependent characteristics of the pulsed laser without passivation were changed with respect to the pulse duration, spectral width, and time-bandwidth product displaying 550 fs, 2.8 nm, and 0.406, respectively. With passivation, the changes were limited to <43 fs, <0.3 nm, and <0.012, respectively.

Passivation of black phosphorus saturable absorbers for reliable pulse formation of fiber lasers

Science.gov (United States)

Na, Dongsoo; Park, Kichul; Park, Ki-Hwan; Song, Yong-Won

2017-11-01

Black phosphorus (BP) has attracted increasing attention due to its unique electrical properties. In addition, the outstanding optical nonlinearity of BP has been demonstrated in various ways. Its functionality as a saturable absorber, in particular, has been validated in demonstrations of passive mode-locked lasers. However, normally, the performance of BP is degraded eventually by both thermal and chemical damage in ambient conditions. The passivation of BP is the critical issue to guarantee a stable performance of the optical devices. We quantitatively characterized the mode-locked lasers operated by BP saturable absorbers with diversified passivation materials such as polydimethylsiloxane (PDMS) or Al2O3, considering the atomic structure of the materials, and therefore the hydro-permeability of the passivation layers. Unlike the BP layers without passivation, we demonstrated that the Al2O3-passivated BP layer was protected from the surface oxidation reaction in the long-term, and the PDMS-passivated one had a short-term blocking effect. The quantitative analysis showed that the time-dependent characteristics of the pulsed laser without passivation were changed with respect to the pulse duration, spectral width, and time-bandwidth product displaying 550 fs, 2.8 nm, and 0.406, respectively. With passivation, the changes were limited to <43 fs, <0.3 nm, and <0.012, respectively.

UTag: Long-range Ultra-wideband Passive Radio Frequency Tags

Energy Technology Data Exchange (ETDEWEB)

Dowla, F

2007-03-14

Long-range, ultra-wideband (UWB), passive radio frequency (RF) tags are key components in Radio Frequency IDentification (RFID) system that will revolutionize inventory control and tracking applications. Unlike conventional, battery-operated (active) RFID tags, LLNL's small UWB tags, called 'UTag', operate at long range (up to 20 meters) in harsh, cluttered environments. Because they are battery-less (that is, passive), they have practically infinite lifetimes without human intervention, and they are lower in cost to manufacture and maintain than active RFID tags. These robust, energy-efficient passive tags are remotely powered by UWB radio signals, which are much more difficult to detect, intercept, and jam than conventional narrowband frequencies. The features of long range, battery-less, and low cost give UTag significant advantage over other existing RFID tags.

Optics equations for aero-optical analysis

Science.gov (United States)

Sutton, George W.; Pond, John E.

2011-05-01

Aero-optical effects occur around moving air vehicles and impact passive imaging or active systems. The air flow around the vehicle is compressed, and often there is a turbulent shear and/or boundary layer both of which cause variations in the index of refraction. Examples of these are reconnaissance aircraft, the Stratospheric Observatory for Infrared Optics (SOFIA), and optically homing hypersonic interceptors. In other applications, a laser beam can be formed within the vehicle, and projected outward and focused on an object. These include the Airborne Laser Laboratory, Airborne Laser and the Airborne Tactical Laser. There are many compressible fluid mechanics computer programs that can predict the air density distribution of the surrounding flow field including density fluctuations in turbulent shear and/or boundary layers. It is necessary for the physical optics to be used to predict the properties of the ensuing image plane intensity distribution, whether passive or active. These include the time-averaged image blur circle and instantaneous realizations. (Ray tracing is a poor approximation that gives erroneous results for small aberrations.)

REAL TIME DATA PROCESSING FOR OPTICAL REMOTE SENSING PAYLOADS

Directory of Open Access Journals (Sweden)

J. Wohlfeil

2012-07-01

Full Text Available The application of operational systems for remote sensing requires new approaches for data processing. It has to be the goal to derive user relevant information close the sensor itself and to downlink this information to a ground station or to provide them as input to an actuator of the space-borne platform. A complete automation of data processing is an essential first step for a thematic onboard data processing. In a second step, an appropriate onboard computer system has to be de-signed being able to fulfill the requirements. In this paper, standard data processing steps will be introduced correcting systematic errors during image capturing. A new hardware operating system, which is the interface between FPGA hardware and data processing algorithms, gives the opportunity to implement complex data processing modules in an effective way. As an example the derivation the camera's orientation based on data of an optical payload is described in detail. The thereby derived absolute or relative orientation is essential for high level data products. This will be illustrated by means of an onboard image matcher

Active and passive silica waveguide integration

DEFF Research Database (Denmark)

Hübner, Jörg; Guldberg-Kjær, Søren Andreas

2001-01-01

. The increasing complexity and functionality of optical networks prompts a demand for highly integrated optical circuits. On-board optical amplifiers, monolithically integrated with functionalities like switching or multiplexing/demultiplexing will allow flexible incorporation of optical integrated circuits...... in existing and future networks without affecting the power budget of the system. Silica on silicon technology offers a unique possibility to selectively dope sections of the integrated circuit with erbium where amplification is desired. Some techniques for active/passive integration are reviewed and a silica......Integrated optical amplifiers are currently regaining interest. Stand-alone single integrated amplifiers offer only limited advantage over current erbium doped fiber amplifiers, whereas arrays of integrated amplifiers are very attractive due to miniaturization and the possibility of mass production...

Remote Monitoring of Cardiac Implantable Electronic Devices.

Science.gov (United States)

Cheung, Christopher C; Deyell, Marc W

2018-01-08

Over the past decade, technological advancements have transformed the delivery of care for arrhythmia patients. From early transtelephonic monitoring to new devices capable of wireless and cellular transmission, remote monitoring has revolutionized device care. In this article, we review the current evolution and evidence for remote monitoring in patients with cardiac implantable electronic devices. From passive transmission of device diagnostics, to active transmission of patient- and device-triggered alerts, remote monitoring can shorten the time to diagnosis and treatment. Studies have shown that remote monitoring can reduce hospitalization and emergency room visits, and improve survival. Remote monitoring can also reduce the health care costs, while providing increased access to patients living in rural or marginalized communities. Unfortunately, as many as two-thirds of patients with remote monitoring-capable devices do not use, or are not offered, this feature. Current guidelines recommend remote monitoring and interrogation, combined with annual in-person evaluation in all cardiac device patients. Remote monitoring should be considered in all eligible device patients and should be considered standard of care. Copyright © 2018 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved.

Remote sensing of stratospheric O{sub 3} and NO{sub 2} using a portable and compact DOAS spectrometer

Energy Technology Data Exchange (ETDEWEB)

Raponi, M M; Wolfram, E; Quel, E J [Division LIDAR, Centro de Investigaciones en Laseres y Aplicaciones, CEILAP (CITEFA-CONICET), Juan B. de La Salle 4397 (B1603ALO), Villa Martelli, Buenos Aires (Argentina); Jimenez, R [Department of Chemical and Environmental Engineering, Universidad Nacional de Colombia, Bogota (Colombia); Tocho, J O, E-mail: mraponi@citefa.gov.ar [Centro de Investigaciones Opticas, CIOp (CONICET La Plata-CIC), Buenos Aires (Argentina)

2011-01-01

The use of passive and active remote sensing systems has largely contributed to advance our understanding of important atmospheric phenomena. Here we present a compact and portable passive DOAS (Differential Optical Absorption Spectroscopy) system, developed for measuring the vertical column density (VCD) of multiple atmospheric trace gases. We highlight the main characteristics of the system components: a mini-spectrometer (HR4000, Ocean Optics), two optical fibers (400 {mu}m of core, 6 m and 25 cm of longitude), an external shutter and the control/data processing software. Nitrogen dioxide (NO{sub 2}) and ozone (O{sub 3}) VCDs are derived from solar spectra acquired during twilights (87{sup 0} - 91{sup 0} zenithal angles) using the DOAS technique. The analysis is carried out by solving the Beer-Lambert-Bouger (BLB) law for the main atmospheric absorbers at selected wavelength ranges. The algorithm minimizes the fitting residuals to the BLB law, having as unknown the slant column density (SCD) of the species to determine. We present measurements carried out at the Marambio Antarctic Base (64{sup 0} 14' 25'' S; 56{sup 0} 37' 21'' W, 197 m asl) during January - February 2008. In addition, we compare our results with co-located measurements performed with EVA, a visible absorption spectrometer of Instituto Nacional de Tecnica Aeroespacial (INTA, Spain), a Dobson spectrophotometer of Servicio Meteorologico Nacional (SMN, Argentine) and the Ozone Monitoring Instrument (OMI), on board AURA satellite.

Applications of airborne remote sensing in atmospheric sciences research

Science.gov (United States)

Serafin, R. J.; Szejwach, G.; Phillips, B. B.

1984-01-01

This paper explores the potential for airborne remote sensing for atmospheric sciences research. Passive and active techniques from the microwave to visible bands are discussed. It is concluded that technology has progressed sufficiently in several areas that the time is right to develop and operate new remote sensing instruments for use by the community of atmospheric scientists as general purpose tools. Promising candidates include Doppler radar and lidar, infrared short range radiometry, and microwave radiometry.

A Method to Analyze the Potential of Optical Remote Sensing for Benthic Habitat Mapping

Directory of Open Access Journals (Sweden)

Rodrigo A. Garcia

2015-10-01

Full Text Available Quantifying the number and type of benthic classes that are able to be spectrally identified in shallow water remote sensing is important in understanding its potential for habitat mapping. Factors that impact the effectiveness of shallow water habitat mapping include water column turbidity, depth, sensor and environmental noise, spectral resolution of the sensor and spectral variability of the benthic classes. In this paper, we present a simple hierarchical clustering method coupled with a shallow water forward model to generate water-column specific spectral libraries. This technique requires no prior decision on the number of classes to output: the resultant classes are optically separable above the spectral noise introduced by the sensor, image based radiometric corrections, the benthos’ natural spectral variability and the attenuating properties of a variable water column at depth. The modeling reveals the effect reducing the spectral resolution has on the number and type of classes that are optically distinct. We illustrate the potential of this clustering algorithm in an analysis of the conditions, including clustering accuracy, sensor spectral resolution and water column optical properties and depth that enabled the spectral distinction of the seagrass Amphibolis antartica from benthic algae.

Signal to Noise Ratio (SNR Enhancement Comparison of Impulse-, Coding- and Novel Linear-Frequency-Chirp-Based Optical Time Domain Reflectometry (OTDR for Passive Optical Network (PON Monitoring Based on Unique Combinations of Wavelength Selective Mirrors

Directory of Open Access Journals (Sweden)

Christopher M. Bentz

2014-03-01

Full Text Available We compare optical time domain reflectometry (OTDR techniques based on conventional single impulse, coding and linear frequency chirps concerning their signal to noise ratio (SNR enhancements by measurements in a passive optical network (PON with a maximum one-way attenuation of 36.6 dB. A total of six subscribers, each represented by a unique mirror pair with narrow reflection bandwidths, are installed within a distance of 14 m. The spatial resolution of the OTDR set-up is 3.0 m.

Visible light communications using predistortion signal to enhance the response of passive optical receiver

Science.gov (United States)

Liu, Yang; Chen, Hung-Yu; Liang, Kevin; Wei, Liang-Yu; Chow, Chi-Wai; Yeh, Chien-Hung

2016-01-01

Traditional visible light communication (VLC) uses positive-intrinsic-negative photodiode (PD) or avalanche PD as the optical receivers (Rx). We demonstrate using a solar cell as the VLC Rx. The solar cell is flexible and low cost and converts the optical signal into an electrical signal directly without the need of external power supply. In addition to acting as the VLC passive Rx, the converted electrical signal from the solar cell can charge up the battery of the Rx nodes. Hence, the proposed scheme can be a promising candidate for the future Internet of Things network. However, a solar cell acting as a VLC Rx is very challenging, since the response of the solar cell is limited. Here, we propose and demonstrate using predistortion to significantly enhance the solar cell Rx response for the first time up to the authors' knowledge. Experimental results show that the response of the solar cell Rx is significantly enhanced; and the original 2-kHz detection bandwidth of the solar cell can be enhanced by 250 times for receiving 500-kbit/s VLC signal at a transmission distance of 1 m. The operation principle, the generated voltage by the solar cell, and the maximum data rates achieved at different transmission distances are also studied.

Remote sensing reflectance and inherent optical properties of oceanic waters derived from above-water measurements

Science.gov (United States)

Lee, Zhongping; Carder, Kendall L.; Steward, Robert G.; Peacock, Thomas G.; Davis, Curtiss O.; Mueller, James L.

1997-02-01

Remote-sensing reflectance and inherent optical properties of oceanic properties of oceanic waters are important parameters for ocean optics. Due to surface reflectance, Rrs or water-leaving radiance is difficult to measure from above the surface. It usually is derived by correcting for the reflected skylight in the measured above-water upwelling radiance using a theoretical Fresnel reflectance value. As it is difficult to determine the reflected skylight, there are errors in the Q and E derived Rrs, and the errors may get bigger for high chl_a coastal waters. For better correction of the reflected skylight,w e propose the following derivation procedure: partition the skylight into Rayleigh and aerosol contributions, remove the Rayleigh contribution using the Fresnel reflectance, and correct the aerosol contribution using an optimization algorithm. During the process, Rrs and in-water inherent optical properties are derived at the same time. For measurements of 45 sites made in the Gulf of Mexico and Arabian Sea with chl_a concentrations ranging from 0.07 to 49 mg/m3, the derived Rrs and inherent optical property values were compared with those from in-water measurements. These results indicate that for the waters studied, the proposed algorithm performs quite well in deriving Rrs and in- water inherent optical properties from above-surface measurements for clear and turbid waters.

Upstream vertical cavity surface-emitting lasers for fault monitoring and localization in WDM passive optical networks

Science.gov (United States)

Wong, Elaine; Zhao, Xiaoxue; Chang-Hasnain, Connie J.

2008-04-01

As wavelength division multiplexed passive optical networks (WDM-PONs) are expected to be first deployed to transport high capacity services to business customers, real-time knowledge of fiber/device faults and the location of such faults will be a necessity to guarantee reliability. Nonetheless, the added benefit of implementing fault monitoring capability should only incur minimal cost associated with upgrades to the network. In this work, we propose and experimentally demonstrate a fault monitoring and localization scheme based on a highly-sensitive and potentially low-cost monitor in conjunction with vertical cavity surface-emitting lasers (VCSELs). The VCSELs are used as upstream transmitters in the WDM-PON. The proposed scheme benefits from the high reflectivity of the top distributed Bragg reflector (DBR) mirror of optical injection-locked (OIL) VCSELs to reflect monitoring channels back to the central office for monitoring. Characterization of the fault monitor demonstrates high sensitivity, low bandwidth requirements, and potentially low output power. The added advantage of the proposed fault monitoring scheme incurs only a 0.5 dB penalty on the upstream transmissions on the existing infrastructure.

Assessing the relationship between microwave vegetation optical depth and gross primary production

Science.gov (United States)

Teubner, Irene E.; Forkel, Matthias; Jung, Martin; Liu, Yi Y.; Miralles, Diego G.; Parinussa, Robert; van der Schalie, Robin; Vreugdenhil, Mariette; Schwalm, Christopher R.; Tramontana, Gianluca; Camps-Valls, Gustau; Dorigo, Wouter A.

2018-03-01

At the global scale, the uptake of atmospheric carbon dioxide by terrestrial ecosystems through photosynthesis is commonly estimated through vegetation indices or biophysical properties derived from optical remote sensing data. Microwave observations of vegetated areas are sensitive to different components of the vegetation layer than observations in the optical domain and may therefore provide complementary information on the vegetation state, which may be used in the estimation of Gross Primary Production (GPP). However, the relation between GPP and Vegetation Optical Depth (VOD), a biophysical quantity derived from microwave observations, is not yet known. This study aims to explore the relationship between VOD and GPP. VOD data were taken from different frequencies (L-, C-, and X-band) and from both active and passive microwave sensors, including the Advanced Scatterometer (ASCAT), the Soil Moisture Ocean Salinity (SMOS) mission, the Advanced Microwave Scanning Radiometer for Earth Observation System (AMSR-E) and a merged VOD data set from various passive microwave sensors. VOD data were compared against FLUXCOM GPP and Solar-Induced chlorophyll Fluorescence (SIF) from the Global Ozone Monitoring Experiment-2 (GOME-2). FLUXCOM GPP estimates are based on the upscaling of flux tower GPP observations using optical satellite data, while SIF observations present a measure of photosynthetic activity and are often used as a proxy for GPP. For relating VOD to GPP, three variables were analyzed: original VOD time series, temporal changes in VOD (ΔVOD), and positive changes in VOD (ΔVOD≥0). Results show widespread positive correlations between VOD and GPP with some negative correlations mainly occurring in dry and wet regions for active and passive VOD, respectively. Correlations between VOD and GPP were similar or higher than between VOD and SIF. When comparing the three variables for relating VOD to GPP, correlations with GPP were higher for the original VOD time

Evaluation of passive samplers for the collection of dissolved organic matter in streams.

Science.gov (United States)

Warner, Daniel L; Oviedo-Vargas, Diana; Royer, Todd V

2015-01-01

Traditional sampling methods for dissolved organic matter (DOM) in streams limit opportunities for long-term studies due to time and cost constraints. Passive DOM samplers were constructed following a design proposed previously which utilizes diethylaminoethyl (DEAE) cellulose as a sampling medium, and they were deployed throughout a temperate stream network in Indiana. Two deployments of the passive samplers were conducted, during which grab samples were frequently collected for comparison. Differences in DOM quality between sites and sampling methods were assessed using several common optical analyses. The analyses revealed significant differences in optical properties between sampling methods, with the passive samplers preferentially collecting terrestrial, humic-like DOM. We assert that the differences in DOM composition from each sampling method were caused by preferential binding of complex humic compounds to the DEAE cellulose in the passive samplers. Nonetheless, the passive samplers may provide a cost-effective, integrated sample of DOM in situations where the bulk DOM pool is composed mainly of terrestrial, humic-like compounds.

Remote Optical Detection of Alpha Radiation

International Nuclear Information System (INIS)

Sand, J.; Hannuksela, V.; Toivonen, J.; Ihantola, S.; Peraejaervi, K.; Toivonen, H.

2010-01-01

Alpha emitting radiation sources are typically hard to detect with conventional detectors due to the short range of alpha particles in the air. However, previous studies have shown that remote detection of alpha radiation is possible by measuring the ionization-induced fluorescence of air molecules. The alpha-induced ultraviolet (UV) light is mainly emitted by molecular nitrogen and its fluorescence properties are well known. The benefit of this method is the long range of UV photons in the air. Secondly, the detection is possible also under a strong beta and gamma radiation backgrounds as they do not cause localized molecular excitation. In this work, the optical detection was studied using two different detection schemes; spectral separation of fluorescence from the background lighting and coincidence detection of UV photons originating from a single radiative decay event. Our spectrally integrated measurements have shown that one alpha decay event yields up to 400 fluorescence photons in the air and all these UV photons are induced in a 5 ns time-window. On the other hand, the probability of a background coincidence event in 5 ns scale is very rare compared to the number of background photons. This information can be applied in fluorescence coincidence filtering to discriminate the alpha radiation initiated fluorescence signal from much more intense background lighting. A device called HAUVA (Handheld Alpha UV Application) was built during this work for demonstration purposes. HAUVA utilizes spectral filtering and it is designed to detect alpha emitters from a distance of about 40 cm. Using specially selected room lighting, the device is able to separate 1 kBq alpha emitter from the background lighting with 1 second integration time. (author)

Remote sensing of high-latitude ionization profiles by ground-based and spaceborne instrumentation

International Nuclear Information System (INIS)

Vondrak, R.R.

1981-01-01

Ionospheric specification and modeling are now largely based on data provided by active remote sensing with radiowave techniques (ionosondes, incoherent-scatter radars, and satellite beacons). More recently, passive remote sensing techniques have been developed that can be used to monitor quantitatively the spatial distribution of high-latitude E-region ionization. These passive methods depend on the measurement, or inference, of the energy distribution of precipitating kilovolt electrons, the principal source of the nighttime E-region at high latitudes. To validate these techniques, coordinated measurements of the auroral ionosphere have been made with the Chatanika incoherent-scatter radar and a variety of ground-based and spaceborne sensors

Towards breaking the spatial resolution barriers: An optical flow and super-resolution approach for sea ice motion estimation

Science.gov (United States)

Petrou, Zisis I.; Xian, Yang; Tian, YingLi

2018-04-01

Estimation of sea ice motion at fine scales is important for a number of regional and local level applications, including modeling of sea ice distribution, ocean-atmosphere and climate dynamics, as well as safe navigation and sea operations. In this study, we propose an optical flow and super-resolution approach to accurately estimate motion from remote sensing images at a higher spatial resolution than the original data. First, an external example learning-based super-resolution method is applied on the original images to generate higher resolution versions. Then, an optical flow approach is applied on the higher resolution images, identifying sparse correspondences and interpolating them to extract a dense motion vector field with continuous values and subpixel accuracies. Our proposed approach is successfully evaluated on passive microwave, optical, and Synthetic Aperture Radar data, proving appropriate for multi-sensor applications and different spatial resolutions. The approach estimates motion with similar or higher accuracy than the original data, while increasing the spatial resolution of up to eight times. In addition, the adopted optical flow component outperforms a state-of-the-art pattern matching method. Overall, the proposed approach results in accurate motion vectors with unprecedented spatial resolutions of up to 1.5 km for passive microwave data covering the entire Arctic and 20 m for radar data, and proves promising for numerous scientific and operational applications.

Fibre-optic communications

CERN Document Server

Lecoy, Pierre

2010-01-01

This book describes in a comprehensive manner the components and systems of fiber optic communications and networks. The first section explains the theory of multimode and single-mode fibers, then the technological features, including manufacturing, cabling, and connecting. The second section describes the various components (passive and active optical components, integrated optics, opto-electronic transmitters and receivers, and optical amplifiers) used in fiber optic systems. Finally, the optical transmission system design is explained, and applications to optical networks and fiber optic se

LIDAR and atmosphere remote sensing [DST Space Science Initiatives

CSIR Research Space (South Africa)

Venkataraman, S

2009-04-01

Full Text Available Energy Source included in the measurement. Slide 2 © CSIR 2008 www.csir.co.za The observer can control the source Eg. Radar, Lidar, Sodar, Sonar etc. (b) Passive remote sensors. Energy source is not included in the measurement... Instrument Passive Slide 3 © CSIR 2008 www.csir.co.za Active LiDAR Principle • LIDAR (Light Detection and Ranging) • LiDAR employs a laser as a source of pulsed energy • Lasers are advantageous because – checkbld Monochromatic...

Peptide Integrated Optics.

Science.gov (United States)

Handelman, Amir; Lapshina, Nadezda; Apter, Boris; Rosenman, Gil

2018-02-01

Bio-nanophotonics is a wide field in which advanced optical materials, biomedicine, fundamental optics, and nanotechnology are combined and result in the development of biomedical optical chips. Silk fibers or synthetic bioabsorbable polymers are the main light-guiding components. In this work, an advanced concept of integrated bio-optics is proposed, which is based on bioinspired peptide optical materials exhibiting wide optical transparency, nonlinear and electrooptical properties, and effective passive and active waveguiding. Developed new technology combining bottom-up controlled deposition of peptide planar wafers of a large area and top-down focus ion beam lithography provides direct fabrication of peptide optical integrated circuits. Finding a deep modification of peptide optical properties by reconformation of biological secondary structure from native phase to β-sheet architecture is followed by the appearance of visible fluorescence and unexpected transition from a native passive optical waveguiding to an active one. Original biocompatibility, switchable regimes of waveguiding, and multifunctional nonlinear optical properties make these new peptide planar optical materials attractive for application in emerging technology of lab-on-biochips, combining biomedical photonic and electronic circuits toward medical diagnosis, light-activated therapy, and health monitoring. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Remote Participation tools at TEXTOR

International Nuclear Information System (INIS)

Kraemer-Flecken, A.; Krom, J.; Landgraf, B.; Lambertz, H.T.

2010-01-01

Remote Participation is a widely used term with different meanings. In the fusion community it has gained an increasing interest with the shut down of small experiments and participation of associations in larger experiments. Also at TEXTOR Remote Participation becomes more and more important with an increasing number of collaborations. At TEXTOR we differentiate between active and passive remote experiment participation. In addition potential users of TEXTOR like to be involved in the experiment preparation phase where the experiment schedule and the availability of diagnostic systems is discussed as well. After an experiment joint groups of users like to share the results and communicate with each other. The final step in publishing the results is also made more transparent for the users in a twofold process. Using a web based pinboard to spread the publication within the user community allows an extensive and early discussion of the results.

A Direct Comparison of Passive Polarimetry and Scatterometry Under Low- and High-Wind Conditions

National Research Council Canada - National Science Library

Swift, Calvin

1997-01-01

The University of Massachusetts Microwave Remote Sensing Laboratory (MIRSL) gathered coincident active and passive measurements of the ocean surface from the NASA Wallops P3 during the Ocean Wind Imaging (OWI) Experiment...

Passive water and ion transport by cotransporters

DEFF Research Database (Denmark)

Loo, D D; Hirayama, B A; Meinild, A K

1999-01-01

the Lp of control oocytes. Passive Na+ transport (Na+ leak) was obtained from the blocker-sensitive Na+ currents in the absence of substrates (glucose and GABA). 2. Passive Na+ and water transport through SGLT1 were blocked by phlorizin with the same sensitivity (inhibitory constant (Ki), 3-5 micro......1. The rabbit Na+-glucose (SGLT1) and the human Na+-Cl--GABA (GAT1) cotransporters were expressed in Xenopus laevis oocytes, and passive Na+ and water transport were studied using electrical and optical techniques. Passive water permeabilities (Lp) of the cotransporters were determined from......M). When Na+ was replaced with Li+, phlorizin also inhibited Li+ and water transport, but with a lower affinity (Ki, 100 microM). When Na+ was replaced by choline, which is not transported, the SGLT1 Lp was indistinguishable from that in Na+ or Li+, but in this case water transport was less sensitive...

An Uneven Illumination Correction Algorithm for Optical Remote Sensing Images Covered with Thin Clouds

Directory of Open Access Journals (Sweden)

Xiaole Shen

2015-09-01

Full Text Available The uneven illumination phenomenon caused by thin clouds will reduce the quality of remote sensing images, and bring adverse effects to the image interpretation. To remove the effect of thin clouds on images, an uneven illumination correction can be applied. In this paper, an effective uneven illumination correction algorithm is proposed to remove the effect of thin clouds and to restore the ground information of the optical remote sensing image. The imaging model of remote sensing images covered by thin clouds is analyzed. Due to the transmission attenuation, reflection, and scattering, the thin cloud cover usually increases region brightness and reduces saturation and contrast of the image. As a result, a wavelet domain enhancement is performed for the image in Hue-Saturation-Value (HSV color space. We use images with thin clouds in Wuhan area captured by QuickBird and ZiYuan-3 (ZY-3 satellites for experiments. Three traditional uneven illumination correction algorithms, i.e., multi-scale Retinex (MSR algorithm, homomorphic filtering (HF-based algorithm, and wavelet transform-based MASK (WT-MASK algorithm are performed for comparison. Five indicators, i.e., mean value, standard deviation, information entropy, average gradient, and hue deviation index (HDI are used to analyze the effect of the algorithms. The experimental results show that the proposed algorithm can effectively eliminate the influences of thin clouds and restore the real color of ground objects under thin clouds.

A Comparison of Novel Optical Remote Sensing-Based Technologies for Forest-Cover/Change Monitoring

Directory of Open Access Journals (Sweden)

Gillian V. Lui

2015-03-01

Full Text Available Remote sensing is gaining considerable traction in forest monitoring efforts, with the Carnegie Landsat Analysis System lite (CLASlite software package and the Global Forest Change dataset (GFCD being two of the most recently developed optical remote sensing-based tools for analysing forest cover and change. Due to the relatively nascent state of these technologies, their abilities to classify land cover and monitor forest dynamics have yet to be evaluated against more established approaches. Here, we compared maps of forest cover and change produced by the more traditional supervised classification approach with those produced by CLASlite and the GFCD, working with imagery collected over Sierra Leone, West Africa. CLASlite maps of forest change from 2001–2007 and 2007–2014 exhibited the highest overall accuracies (79.1% and 89.6%, respectively and, importantly, the greatest capacity to discriminate natural from planted mature forest growth. CLASlite’s comparative advantage likely derived from its more robust sub-pixel classification logic and numerous user-defined parameters, which resulted in classified products with greater site relevance than those of the two other classification approaches. In light of today’s continuously growing body of analytical toolsets for remotely sensed data, our study importantly elucidates the ways in which methodological processes and limitations inherent in certain classification tools can impact the maps they are capable of producing, and demonstrates the need to understand and weigh such factors before any one tool is selected for a given application.

PASSIVE WIRELESS MULTI-SENSOR TEMPERATURE AND PRESSURE SENSING SYSTEM USING ACOUSTIC WAVE DEVICES, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — This proposal describes the development of passive surface acoustic wave (SAW) sensors and multi-sensor systems for NASA application to remote wireless sensing of...

Evaluation of snow cover and snow depth on the Qinghai–Tibetan Plateau derived from passive microwave remote sensing

Directory of Open Access Journals (Sweden)

L. Dai

2017-08-01

Full Text Available Snow cover on the Qinghai–Tibetan Plateau (QTP plays a significant role in the global climate system and is an important water resource for rivers in the high-elevation region of Asia. At present, passive microwave (PMW remote sensing data are the only efficient way to monitor temporal and spatial variations in snow depth at large scale. However, existing snow depth products show the largest uncertainties across the QTP. In this study, MODIS fractional snow cover product, point, line and intense sampling data are synthesized to evaluate the accuracy of snow cover and snow depth derived from PMW remote sensing data and to analyze the possible causes of uncertainties. The results show that the accuracy of snow cover extents varies spatially and depends on the fraction of snow cover. Based on the assumption that grids with MODIS snow cover fraction > 10 % are regarded as snow cover, the overall accuracy in snow cover is 66.7 %, overestimation error is 56.1 %, underestimation error is 21.1 %, commission error is 27.6 % and omission error is 47.4 %. The commission and overestimation errors of snow cover primarily occur in the northwest and southeast areas with low ground temperature. Omission error primarily occurs in cold desert areas with shallow snow, and underestimation error mainly occurs in glacier and lake areas. With the increase of snow cover fraction, the overestimation error decreases and the omission error increases. A comparison between snow depths measured in field experiments, measured at meteorological stations and estimated across the QTP shows that agreement between observation and retrieval improves with an increasing number of observation points in a PMW grid. The misclassification and errors between observed and retrieved snow depth are associated with the relatively coarse resolution of PMW remote sensing, ground temperature, snow characteristics and topography. To accurately understand the variation in snow

Offshore winds mapped from satellite remote sensing

DEFF Research Database (Denmark)

Hasager, Charlotte Bay

2014-01-01

the uncertainty on the model results on the offshore wind resource, it is necessary to compare model results with observations. Observations from ground-based wind lidar and satellite remote sensing are the two main technologies that can provide new types of offshore wind data at relatively low cost....... The advantages of microwave satellite remote sensing are 1) horizontal spatial coverage, 2) long data archives and 3) high spatial detail both in the coastal zone and of far-field wind farm wake. Passive microwave ocean wind speed data are available since 1987 with up to 6 observations per day with near...

Passive athermalization of doublets in 8-13 micron waveband

Science.gov (United States)

Schuster, Norbert

2014-10-01

Passive athermalization of lenses has become a key-technology for automotive and other outdoor applications using modern uncooled 25, 17 and 12 micron pixel pitch bolometer arrays. Typical pixel counts for thermal imaging are 384x288 (qVGA), 640x480 (VGA), and 1024x768 (XGA). Two lens arrangements (called Doublets) represent a cost effective way to satisfy resolution requirements of these detectors with F-numbers 1.4 or faster. Thermal drift of index of refraction and the geometrical changes (in lenses and housing) versus temperature defocus the initial image plane from the detector plane. The passive athermalization restricts this drop of spatial resolution in a wide temperature range (typically -40°C…+80°C) to an acceptable value without any additional external refocus. In particular, lenses with long focal lengths and high apertures claim athermalization. A careful choice of lens and housing materials and a sophistical dimensioning lead to three different principles of passivation: The Passive Mechanical Athermalization (PMA) shifts the complete lens cell, the Passive Optical and Mechanical Athermalization (POMA) shifts only one lens inside the housing, the Passive Optical Athermalization (POA) works without any mechanism. All three principles will be demonstrated for a typical narrow-field lens (HFOV about 12°) with high aperture (aperture based F-number 1.3) for the actual uncooled reference detector (17micron VGA). Six design examples using different combinations of lens materials show the impact on spatial lens resolution, on overall length, and on weight. First order relations are discussed. They give some hints for optimization solutions. Pros and cons of different passive athermalization principles are evaluated in regards of housing design, availability of materials and costing. Examples with a convergent GASIR®1-lens in front distinguish by best resolution, short overall length, and lowest weight.

Remote Sensing of Irrigated Agriculture: Opportunities and Challenges

Directory of Open Access Journals (Sweden)

Chelsea Cervantes

2010-09-01

time and resources for ground-truthing. An additional challenge in mapping irrigation across large areas occurs in fragmented landscapes with small irrigated and cultivated fields, where the spatial scale of observations is pitted against the need for high frequency temporal acquisitions. Finally, this review identifies passive and active microwave observations, advanced image classification methods, and data fusion including optical and radar sensors or with information from sources with multiple spatial and temporal characteristics as key areas where additional research is needed.

Remote Detection of Covert Tactical Adversarial Intent of Individuals in Asymmetric Operations

Science.gov (United States)

2010-04-01

Hyperspectral imagers: Passive multiband imagers are optimized to select specific wavelengths of interest related to particular optical phenomena or...monitoring (either fluorescent imaging or nonimaging amplitude of a particular wavelength), can be used to inspect a portion of the body for sweat or...17 • Retroreflection: Active laser illumination and passive imaging of the collimated returns can be used for detecting optics /video cameras

3rd Symposium on Space Optical Instruments and Applications

CERN Document Server

Zhang, Guangjun

2017-01-01

This volume contains selected and expanded contributions presented at the 3rd Symposium on Space Optical Instruments and Applications in Beijing, China June 28 – 29, 2016. This conference series is organised by the Sino-Holland Space Optical Instruments Laboratory, a cooperation platform between China and the Netherlands. The symposium focused on key technological problems of optical instruments and their applications in a space context. It covered the latest developments, experiments and results regarding theory, instrumentation and applications in space optics. The book is split across five topical sections. The first section covers space optical remote sensing system design, the second advanced optical system design, the third remote sensor calibration and measurement. Remote sensing data processing and information extraction is then presented, followed by a final section on remote sensing data applications. .

Analysis on Target Detection and Classification in LTE Based Passive Forward Scattering Radar

Directory of Open Access Journals (Sweden)

Raja Syamsul Azmir Raja Abdullah

2016-09-01

Full Text Available The passive bistatic radar (PBR system can utilize the illuminator of opportunity to enhance radar capability. By utilizing the forward scattering technique and procedure into the specific mode of PBR can provide an improvement in target detection and classification. The system is known as passive Forward Scattering Radar (FSR. The passive FSR system can exploit the peculiar advantage of the enhancement in forward scatter radar cross section (FSRCS for target detection. Thus, the aim of this paper is to show the feasibility of passive FSR for moving target detection and classification by experimental analysis and results. The signal source is coming from the latest technology of 4G Long-Term Evolution (LTE base station. A detailed explanation on the passive FSR receiver circuit, the detection scheme and the classification algorithm are given. In addition, the proposed passive FSR circuit employs the self-mixing technique at the receiver; hence the synchronization signal from the transmitter is not required. The experimental results confirm the passive FSR system’s capability for ground target detection and classification. Furthermore, this paper illustrates the first classification result in the passive FSR system. The great potential in the passive FSR system provides a new research area in passive radar that can be used for diverse remote monitoring applications.

Analysis on Target Detection and Classification in LTE Based Passive Forward Scattering Radar.

Science.gov (United States)

Raja Abdullah, Raja Syamsul Azmir; Abdul Aziz, Noor Hafizah; Abdul Rashid, Nur Emileen; Ahmad Salah, Asem; Hashim, Fazirulhisyam

2016-09-29

The passive bistatic radar (PBR) system can utilize the illuminator of opportunity to enhance radar capability. By utilizing the forward scattering technique and procedure into the specific mode of PBR can provide an improvement in target detection and classification. The system is known as passive Forward Scattering Radar (FSR). The passive FSR system can exploit the peculiar advantage of the enhancement in forward scatter radar cross section (FSRCS) for target detection. Thus, the aim of this paper is to show the feasibility of passive FSR for moving target detection and classification by experimental analysis and results. The signal source is coming from the latest technology of 4G Long-Term Evolution (LTE) base station. A detailed explanation on the passive FSR receiver circuit, the detection scheme and the classification algorithm are given. In addition, the proposed passive FSR circuit employs the self-mixing technique at the receiver; hence the synchronization signal from the transmitter is not required. The experimental results confirm the passive FSR system's capability for ground target detection and classification. Furthermore, this paper illustrates the first classification result in the passive FSR system. The great potential in the passive FSR system provides a new research area in passive radar that can be used for diverse remote monitoring applications.

Development of a passive doas system to retrieve atmospheric pollution columns in the 200 to 355 nm region.

Science.gov (United States)

Mejía, Rubén Galicia; Vázquez, Josémanueldelarosa; Isakina, Suren Stolik; García, Edgard Moreno; Iglesias, Gustavo Sosa

2013-01-08

In recent years several techniques have been developed to measure and monitor the pollution of the air. Among these techniques, remote sensing using optical methods stands out due to several advantages for air quality control applications. A Passive Differential Optical Absorption Spectroscopy system that uses the ultraviolet region from 200 to 355 nm of the solar radiation is presented. The developed system is portable; therefore it is practical for real time and in situ measurements. The enhanced wavelength range of the system is intended to detect the ultraviolet light penetration in the Mexican Valley considering the solar zenith angle and the altitude. The system was applied to retrieve atmospheric SO2 columns emitted either by anthropogenic (power plant) or natural sources (volcano), reaching a detection limit of about 1 ppm. The measurement of the penetrating solar radiation on the earth surface at the UVC range is presented and the possibility to measure pollution traces of some contaminants as O3, NO2 and aromatic compounds in real time and in situ in the ultraviolet region is discussed.

Development of a passive doas system to retrieve atmospheric pollution columns in the 200 to 355 nm region

Directory of Open Access Journals (Sweden)

Mejía Rubén Galicia

2013-01-01

Full Text Available Abstract In recent years several techniques have been developed to measure and monitor the pollution of the air. Among these techniques, remote sensing using optical methods stands out due to several advantages for air quality control applications. A Passive Differential Optical Absorption Spectroscopy system that uses the ultraviolet region from 200 to 355 nm of the solar radiation is presented. The developed system is portable; therefore it is practical for real time and in situ measurements. The enhanced wavelength range of the system is intended to detect the ultraviolet light penetration in the Mexican Valley considering the solar zenith angle and the altitude. The system was applied to retrieve atmospheric SO2 columns emitted either by anthropogenic (power plant or natural sources (volcano, reaching a detection limit of about 1 ppm. The measurement of the penetrating solar radiation on the earth surface at the UVC range is presented and the possibility to measure pollution traces of some contaminants as O3, NO2 and aromatic compounds in real time and in situ in the ultraviolet region is discussed.

Four dimensional hybrid ultrasound and optoacoustic imaging via passive element optical excitation in a hand-held probe

Science.gov (United States)

Fehm, Thomas Felix; Deán-Ben, Xosé Luís; Razansky, Daniel

2014-10-01

Ultrasonography and optoacoustic imaging share powerful advantages related to the natural aptitude for real-time image rendering with high resolution, the hand-held operation, and lack of ionizing radiation. The two methods also possess very different yet highly complementary advantages of the mechanical and optical contrast in living tissues. Nonetheless, efficient integration of these modalities remains challenging owing to the fundamental differences in the underlying physical contrast, optimal signal acquisition, and image reconstruction approaches. We report on a method for hybrid acquisition and reconstruction of three-dimensional pulse-echo ultrasound and optoacoustic images in real time based on passive ultrasound generation with an optical absorber, thus avoiding the hardware complexity of active ultrasound generation. In this way, complete hybrid datasets are generated with a single laser interrogation pulse, resulting in simultaneous rendering of ultrasound and optoacoustic images at an unprecedented rate of 10 volumetric frames per second. Performance is subsequently showcased in phantom experiments and in-vivo measurements from a healthy human volunteer, confirming general clinical applicability of the method.

Four dimensional hybrid ultrasound and optoacoustic imaging via passive element optical excitation in a hand-held probe

International Nuclear Information System (INIS)

Fehm, Thomas Felix; Razansky, Daniel; Deán-Ben, Xosé Luís

2014-01-01

Ultrasonography and optoacoustic imaging share powerful advantages related to the natural aptitude for real-time image rendering with high resolution, the hand-held operation, and lack of ionizing radiation. The two methods also possess very different yet highly complementary advantages of the mechanical and optical contrast in living tissues. Nonetheless, efficient integration of these modalities remains challenging owing to the fundamental differences in the underlying physical contrast, optimal signal acquisition, and image reconstruction approaches. We report on a method for hybrid acquisition and reconstruction of three-dimensional pulse-echo ultrasound and optoacoustic images in real time based on passive ultrasound generation with an optical absorber, thus avoiding the hardware complexity of active ultrasound generation. In this way, complete hybrid datasets are generated with a single laser interrogation pulse, resulting in simultaneous rendering of ultrasound and optoacoustic images at an unprecedented rate of 10 volumetric frames per second. Performance is subsequently showcased in phantom experiments and in-vivo measurements from a healthy human volunteer, confirming general clinical applicability of the method.

Four dimensional hybrid ultrasound and optoacoustic imaging via passive element optical excitation in a hand-held probe

Energy Technology Data Exchange (ETDEWEB)

Fehm, Thomas Felix; Razansky, Daniel, E-mail: dr@tum.de [Institute for Biological and Medical Imaging (IBMI), Helmholtz Zentrum München, Neuherberg (Germany); Faculty of Medicine, Technische Universität München, Munich (Germany); Deán-Ben, Xosé Luís [Institute for Biological and Medical Imaging (IBMI), Helmholtz Zentrum München, Neuherberg (Germany)

2014-10-27

Ultrasonography and optoacoustic imaging share powerful advantages related to the natural aptitude for real-time image rendering with high resolution, the hand-held operation, and lack of ionizing radiation. The two methods also possess very different yet highly complementary advantages of the mechanical and optical contrast in living tissues. Nonetheless, efficient integration of these modalities remains challenging owing to the fundamental differences in the underlying physical contrast, optimal signal acquisition, and image reconstruction approaches. We report on a method for hybrid acquisition and reconstruction of three-dimensional pulse-echo ultrasound and optoacoustic images in real time based on passive ultrasound generation with an optical absorber, thus avoiding the hardware complexity of active ultrasound generation. In this way, complete hybrid datasets are generated with a single laser interrogation pulse, resulting in simultaneous rendering of ultrasound and optoacoustic images at an unprecedented rate of 10 volumetric frames per second. Performance is subsequently showcased in phantom experiments and in-vivo measurements from a healthy human volunteer, confirming general clinical applicability of the method.

Calculating Viewing Angles Pixel by Pixel in Optical Remote Sensing Satellite Imagery Using the Rational Function Model

OpenAIRE

Kai Xu; Guo Zhang; Qingjun Zhang; Deren Li

2018-01-01

In studies involving the extraction of surface physical parameters using optical remote sensing satellite imagery, sun-sensor geometry must be known, especially for sensor viewing angles. However, while pixel-by-pixel acquisitions of sensor viewing angles are of critical importance to many studies, currently available algorithms for calculating sensor-viewing angles focus only on the center-point pixel or are complicated and are not well known. Thus, this study aims to provide a simple and ge...

On-Chip All-Optical Passive 3.55 Gbit/s NRZ-to-PRZ Format Conversion Using a High-Q Silicon-Based Microring Resonator

International Nuclear Information System (INIS)

Yao, Zhai; Shao-Wu, Chen; Guang-Hui, Ren

2010-01-01

We report the experimental result of all-optical passive 3.55 Gbit/s non-return-to-zero (NRZ) to pseudo-return-to-zero (PRZ) format conversion using a high-quality-factor (Q-factor) silicon-based microring resonator notch filter on chip. The silicon-based microring resonator has 23800 Q-factor and 22 dB extinction ratio (ER), and the PRZ signals has about 108ps width and 4.98 dB ER

A Systematic Scheme for Multiple Access in Ethernet Passive Optical Access Networks

Science.gov (United States)

Ma, Maode; Zhu, Yongqing; Hiang Cheng, Tee

2005-11-01

While backbone networks have experienced substantial changes in the last decade, access networks have not changed much. Recently, passive optical networks (PONs) seem to be ready for commercial deployment as access networks, due to the maturity of a number of enabling technologies. Among the PON technologies, Ethernet PON (EPON) standardized by the IEEE 802.3ah Ethernet in the First Mile (EFM) Task Force is the most attractive one because of its high speed, low cost, familiarity, interoperability, and low overhead. In this paper, we consider the issue of upstream channel sharing in the EPONs. We propose a novel multiple-access control scheme to provide bandwidth-guaranteed service for high-demand customers, while providing best effort service to low-demand customers according to the service level agreement (SLA). The analytical and simulation results prove that the proposed scheme performs best in what it is designed to do compared to another well-known scheme that has not considered providing differentiated services. With business customers preferring premium services with guaranteed bandwidth and residential users preferring low-cost best effort services, our scheme could benefit both groups of subscribers, as well as the operators.

Integrating SAR with Optical and Thermal Remote Sensing for Operational Near Real-Time Volcano Monitoring

Science.gov (United States)

Meyer, F. J.; Webley, P.; Dehn, J.; Arko, S. A.; McAlpin, D. B.

2013-12-01

Volcanic eruptions are among the most significant hazards to human society, capable of triggering natural disasters on regional to global scales. In the last decade, remote sensing techniques have become established in operational forecasting, monitoring, and managing of volcanic hazards. Monitoring organizations, like the Alaska Volcano Observatory (AVO), are nowadays heavily relying on remote sensing data from a variety of optical and thermal sensors to provide time-critical hazard information. Despite the high utilization of these remote sensing data to detect and monitor volcanic eruptions, the presence of clouds and a dependence on solar illumination often limit their impact on decision making processes. Synthetic Aperture Radar (SAR) systems are widely believed to be superior to optical sensors in operational monitoring situations, due to the weather and illumination independence of their observations and the sensitivity of SAR to surface changes and deformation. Despite these benefits, the contributions of SAR to operational volcano monitoring have been limited in the past due to (1) high SAR data costs, (2) traditionally long data processing times, and (3) the low temporal sampling frequencies inherent to most SAR systems. In this study, we present improved data access, data processing, and data integration techniques that mitigate some of the above mentioned limitations and allow, for the first time, a meaningful integration of SAR into operational volcano monitoring systems. We will introduce a new database interface that was developed in cooperation with the Alaska Satellite Facility (ASF) and allows for rapid and seamless data access to all of ASF's SAR data holdings. We will also present processing techniques that improve the temporal frequency with which hazard-related products can be produced. These techniques take advantage of modern signal processing technology as well as new radiometric normalization schemes, both enabling the combination of

Simultaneous remote measurement of CO2 concentration, humidity and temperature with a matrix of optical fiber sensors

Science.gov (United States)

Wysokiński, Karol; Filipowicz, Marta; Stańczyk, Tomasz; Lipiński, Stanisław; Napierała, Marek; Murawski, Michał; Nasiłowski, Tomasz

2017-10-01

A matrix of optical fiber sensors eligible for remote measurements is reported in this paper. The aim of work was to monitor the air quality with a device, which does not need any electricity on site of the measurement. The matrix consists of several sensors detecting carbon dioxide concentration, relative humidity and temperature. Sensors utilize active optical materials, which change their color when exposed to varied conditions. All the sensors are powered with standard light emitting diodes. Light is transmitted by an optical fiber from the light source and then it reaches the active layer which changes its color, when the conditions change. This results in a change of attenuation of light passing through the active layer. Modified light is then transmitted by another optical fiber to the detector, where simple photoresistor is used. It is powered by a stabilized DC power supply and the current is measured. Since no expensive elements are needed to manufacture such a matrix of sensors, its price may be competitive to the price of the devices already available on the market, while the matrix also exhibits other valuable properties.

Efficient Bandwidth Management for Ethernet Passive Optical Networks

KAUST Repository

Elrasad, Amr Elsayed M.

2016-05-15

The increasing bandwidth demands in access networks motivates network operators, networking devices manufacturers, and standardization institutions to search for new approaches for access networks. These approaches should support higher bandwidth, longer distance between end user and network operator, and less energy consumption. Ethernet Passive Optical Network (EPON) is a favorable choice for broadband access networks. EPONs support transmission rates up to 10 Gbps. EPONs also support distance between end users and central office up to 20 Km. Moreover, optical networks have the least energy consumption among all types of networks. In this dissertation, we focus on reducing delay and saving energy in EPONs. Reducing delay is essential for delay-sensitive traffic, while minimizing energy consumption is an environmental necessity and also reduces the network operating costs. We identify five challenges, namely excess bandwidth allocation, frame delineation, congestion resolution, large round trip time delay in long-reach EPONs (LR-EPONs), and energy saving. We provide a Dynamic Bandwidth Allocation (DBA) approach for each challenge. We also propose a novel scheme that combines the features of the proposed approaches in one highly performing scheme. Our approach is to design novel DBA protocols that can further reduce the delay and be simultaneously simple and fair. We also present a dynamic bandwidth allocation scheme for Green EPONs taking into consideration maximizing energy saving under target delay constraints. Regarding excess bandwidth allocation, we develop an effective DBA scheme called Delayed Excess Scheduling (DES). DES achieves significant delay and jitter reduction and is more suitable for industrial deployment due to its simplicity. Utilizing DES in hybrid TDM/WDM EPONs (TWDM-EPONs) is also investigated. We also study eliminating the wasted bandwidth due to frame delineation. We develop an interactive DBA scheme, Efficient Grant Sizing Interleaved

Assessment of Wildfire Risk in Southern California with Live Fuel Moisture Measurement and Remotely Sensed Vegetation Water Content Proxies

Science.gov (United States)

Jia, S.; Kim, S. H.; Nghiem, S. V.; Kafatos, M.

2017-12-01

Live fuel moisture (LFM) is the water content of live herbaceous plants expressed as a percentage of the oven-dry weight of plant. It is a critical parameter in fire ignition in Mediterranean climate and routinely measured in sites selected by fire agencies across the U.S. Vegetation growing cycle, meteorological metrics, soil type, and topography all contribute to the seasonal and inter-annual variation of LFM, and therefore, the risk of wildfire. The optical remote sensing-based vegetation indices (VIs) have been used to estimate the LFM. Comparing to the VIs, microwave remote sensing products have advantages like less saturation effect in greenness and representing the water content of the vegetation cover. In this study, we established three models to evaluate the predictability of LFM in Southern California using MODIS NDVI, vegetation temperature condition index (VTCI) from downscaled Soil Moisture Active Passive (SMAP) products, and vegetation optical depth (VOD) derived by Land Parameter Retrieval Model. Other ancillary variables, such as topographic factors (aspects and slope) and meteorological metrics (air temperature, precipitation, and relative humidity), are also considered in the models. The model results revealed an improvement of LFM estimation from SMAP products and VOD, despite the uncertainties introduced in the downscaling and parameter retrieval. The estimation of LFM using remote sensing data can provide an assessment of wildfire danger better than current methods using NDVI-based growing seasonal index. Future study will test the VOD estimation from SMAP data using the multi-temporal dual channel algorithm (MT-DCA) and extend the LFM modeling to a regional scale.

Application of various surface passivation layers in solar cells

International Nuclear Information System (INIS)

Lee, Ji Youn; Lee, Soo Hong

2004-01-01

In this work, we have used different techniques for surface passivation: conventional thermal oxidation (CTO), rapid thermal oxidation (RTO), and plasma-enhanced chemical vapour deposition (PECVD). The surface passivation qualities of eight different single and combined double layers have been investigated both on phosphorus non-diffused p-type Float Zone (FZ) silicon wafers and on diffused emitters (100 Ω/□ and 40 Ω/□). CTO/SiN 1 passivates very well not only on a non-diffused surface (τ eff = 1361 μs) but also on an emitter (τ eff = 414 μs). However, we concluded that RTO/SiN 1 and RTO/SiN 2 stacks were more suitable than CTO/SiN stacks for surface passivation in solar cells since those stacks had relatively good passivation qualities and suitable optical reflections. RTO/SiN 1 for rear-surface passivation and RTO/SiN 2 for front-surface passivation were applied to the fabrication of solar cells. We achieved efficiencies of 18.5 % and 18.8 % on 0.5 Ω-cm (FZ) silicon with planar and textured front surfaces, respectively. An excellent open circuit voltage (V oc ) of 675.6 mV was obtained for the planar cell.

In situ passivation of GaAsP nanowires.

Science.gov (United States)

Himwas, C; Collin, S; Rale, P; Chauvin, N; Patriarche, G; Oehler, F; Julien, F H; Travers, L; Harmand, J-C; Tchernycheva, M

2017-12-08

We report on the structural and optical properties of GaAsP nanowires (NWs) grown by molecular-beam epitaxy. By adjusting the alloy composition in the NWs, the transition energy was tuned to the optimal value required for tandem III-V/silicon solar cells. We discovered that an unintentional shell was also formed during the GaAsP NW growth. The NW surface was passivated by an in situ deposition of a radial Ga(As)P shell. Different shell compositions and thicknesses were investigated. We demonstrate that the optimal passivation conditions for GaAsP NWs (with a gap of 1.78 eV) are obtained with a 5 nm thick GaP shell. This passivation enhances the luminescence intensity of the NWs by 2 orders of magnitude and yields a longer luminescence decay. The luminescence dynamics changes from single exponential decay with a 4 ps characteristic time in non-passivated NWs to a bi-exponential decay with characteristic times of 85 and 540 ps in NWs with GaP shell passivation.

In situ passivation of GaAsP nanowires

Science.gov (United States)

Himwas, C.; Collin, S.; Rale, P.; Chauvin, N.; Patriarche, G.; Oehler, F.; Julien, F. H.; Travers, L.; Harmand, J.-C.; Tchernycheva, M.

2017-12-01

We report on the structural and optical properties of GaAsP nanowires (NWs) grown by molecular-beam epitaxy. By adjusting the alloy composition in the NWs, the transition energy was tuned to the optimal value required for tandem III-V/silicon solar cells. We discovered that an unintentional shell was also formed during the GaAsP NW growth. The NW surface was passivated by an in situ deposition of a radial Ga(As)P shell. Different shell compositions and thicknesses were investigated. We demonstrate that the optimal passivation conditions for GaAsP NWs (with a gap of 1.78 eV) are obtained with a 5 nm thick GaP shell. This passivation enhances the luminescence intensity of the NWs by 2 orders of magnitude and yields a longer luminescence decay. The luminescence dynamics changes from single exponential decay with a 4 ps characteristic time in non-passivated NWs to a bi-exponential decay with characteristic times of 85 and 540 ps in NWs with GaP shell passivation.

Microwave and millimeter-wave remote sensing for security applications

CERN Document Server

Nanzer, Jeffrey

2012-01-01

Microwave and millimeter-wave remote sensing techniques are fast becoming a necessity in many aspects of security as detection and classification of objects or intruders becomes more difficult. This groundbreaking resource offers you expert guidance in this burgeoning area. It provides you with a thorough treatment of the principles of microwave and millimeter-wave remote sensing for security applications, as well as practical coverage of the design of radiometer, radar, and imaging systems. You learn how to design active and passive sensors for intruder detection, concealed object detection,

Perancancangan Jaringan Fiber To The Home (FTTH Menggunakan Teknologi Gigabyte Passive Optical Network (GPON pada Mall Park23 Tuban

Directory of Open Access Journals (Sweden)

I Putu Gede Yudha Pratama

2017-08-01

Full Text Available Abstrak-Perancangan jaringan ini berpusat pada sebuah mall baru yang akan dibangun pada daerah Tuban, Bali. Yang dimana mall berada pada pada luas tanah 6,981 m2. Perancangan ini menggunakan sistem IndiHome (100% fiber dengan menggunakan GPON (Gigabyte Passive Optical Network sebagai teknologinya. Perancangan jaringan ini, dimulai dengan perhitungan demand dan menghitung kebutuhan traffik tiap calon tenant yang akan dibagi menjadi 3 kategori jenis tenant. Dilanjutkan dengan proses merancang struktur jaringan yang dimulai dari penyambungan kabel pada closure sebanyak 48 core hingga sampai pada ONT (Optical Network Termination. Hasil analisis dengan menggunakan parameter Power Link Budget diperoleh total redaman untuk uplink dan downlink masing-masing sebesar 23,84 dB dan 23,574 dB. Margin Daya didapat sebesar 4,16 dBm. Sedangkan, Rise Time Budget diperoleh sebesar 0,25 ns untuk uplink dan 0,22 ns untuk downlink. Nilai tersebut masih dibawah standard maksimum rise time yaitu sebesar 0,5833 ns.

Optical luminescence from alkyl-passivated Si nanocrystals under vacuum ultraviolet excitation: Origin and temperature dependence of the blue and orange emissions

OpenAIRE

Chao, Y; Houlton, A; Horrocks, BR; Hunt, MRC; Poolton, NRJ; Yang, J; Šiller, L

2006-01-01

The origin and stability of luminescence are critical issues for Si nanocrystals which are intended for use as biological probes. The optical luminescence of alkyl-monolayer-passivated silicon nanocrystals was studied under excitation with vacuum ultraviolet photons (5.1–23 eV). Blue and orange emission bands were observed simultaneously, but the blue band only appeared at low temperatures (8.7 eV). At 8 K, the peak wavelengths of the emission bands were 430±2 nm (blue) and 600±2 nm (orange)....

ESA remote-sensing programme - Present activities and future plans

Energy Technology Data Exchange (ETDEWEB)

Plevin, J [ESA, Directorate of Planning and Future Programmes, Paris, France; Pryke, I [ESA, Directorate of Applications Programmes, Toulouse, France

1979-02-01

The present activities and future missions of the ESA program of spaceborne remote sensing of earth resources and environment are discussed. Program objectives have been determined to be the satisfaction of European regional needs by agricultural, land use, water resources, coastal and polar surveys, and meeting the requirements of developing nations in the areas of agricultural production, mineral exploration and disaster warning and assessment. The Earthnet system of data processing centers presently is used for the distribution of remote sensing data acquired by NASA satellites. Remote sensing experiments to be flown aboard Spacelab are the Metric Camera, to test high resolution mapping capabilities of a large format camera, and the Microwave Remote-Sensing Experiment, which operates as a two-frequency scatterometer, a synthetic aperture radar and a passive microwave radiometer. Studies carried out on the definition of future remote sensing satellite systems are described, including studies of system concepts for land applications and coastal monitoring satellites.

Inherent optical properties and remote sensing reflectance of Pomeranian lakes (Poland

Directory of Open Access Journals (Sweden)

Dariusz Ficek

2012-11-01

Full Text Available This paper describes the results of comprehensive empirical studies of theinherent optical properties (IOPs, the remote sensing reflectance Rrs(λ andthe contents of the principal optically active components (OAC i.e. coloureddissolved organic matter (CDOM, suspended particulate matter (SPM andchlorophyll a, in the waters of 15 lakes in Polish Pomerania in 2007-2010.It presents numerous spectra of the total absorption a(λ andscattering b(λ ≈ bp(λ of light in the visibleband (400-700 nm for surface waters, and separately, spectra of absorptionby CDOM aCDOM(λ and spectra of the mass-specificcoefficients of absorption ap*(SPM(λ and scatteringbp*(SPM(λ by SPM. The properties of these lake waters are highly diverse, but all of them can beclassified as Case 2 waters (according to the optical classification by Morel& Prieur 1977 and they all have a relatively high OAC content. The lakeswere conventionally divided into three types: Type I lakes have the lowestOAC concentrations (chlorophyll concentration Ca = (8.76 ± 7.4 mg m-3 and CDOM absorption coefficientsaCDOM(440 = (0.57 ± 0.22 m-1 (i.e. mean and standarddeviation, and optical properties (including spectra of Rrs(λresembling those of Baltic waters. Type II waters have exceptionally highcontents of CDOM (aCDOM(440 = (15.37 ± 1.54 m-1,and hence appear brown in daylight and have very low reflectancesRrs(λ (of the order of 0.001 sr-1. Type III waters arehighly eutrophic and contain large amounts of suspended matter, includingphytoplankton ((CSPM = (47.0 ± 39.4 g m-3,Ca = (86.6 ± 61.5 mg m-3; aCDOM(440 = (2.77 ± 0.86 m-1. Hence the reflectances Rrs(λof these type of waters are on average one order of magnitude higher thanthose of the other natural waters, reaching maximum values of 0.03 sr-1in λ bands 560-580 nm and 690-720 nm (see Ficek et al. 2011. Thearticle provides a number of empirical formulas approximating therelationships between the properties of these lake waters.

A low-cost, portable optical sensing system with wireless communication compatible of real-time and remote detection of dissolved ammonia

Science.gov (United States)

Deng, Shijie; Doherty, William; McAuliffe, Michael AP; Salaj-Kosla, Urszula; Lewis, Liam; Huyet, Guillaume

2016-06-01

A low-cost and portable optical chemical sensor based ammonia sensing system that is capable of detecting dissolved ammonia up to 5 ppm is presented. In the system, an optical chemical sensor is designed and fabricated for sensing dissolved ammonia concentrations. The sensor uses eosin as the fluorescence dye which is immobilized on the glass substrate by a gas-permeable protection layer. A compact module is developed to hold the optical components, and a battery powered micro-controller system is designed to read out and process the data measured. The system operates without the requirement of laboratory instruments that makes it cost effective and highly portable. Moreover, the calculated results in the system can be transmitted to a PC wirelessly, which allows the remote and real-time monitoring of dissolved ammonia.

LIDAR and atmosphere remote sensing

CSIR Research Space (South Africa)

Venkataraman, S

2008-05-01

Full Text Available using state of the art Light Detection And Ranging (LiDAR) instrumentation and other active and passive remote sensing tools. First “Lidar Field Campaign” • 2-day measurement campaign at University of Pretoria • First 23-hour continuous measurement... head2rightCirrus cloud morphology and dynamics. Atmospheric Research in Southern Africa and Indian Ocean (ARSAIO) Slide 24 © CSIR 2008 www.csir.co.za Middle atmosphere dynamics and thermal structure: comparative studies from...

[Retrieval of crown closure of moso bamboo forest using unmanned aerial vehicle (UAV) remotely sensed imagery based on geometric-optical model].

Science.gov (United States)

Wang, Cong; Du, Hua-qiang; Zhou, Guo-mo; Xu, Xiao-jun; Sun, Shao-bo; Gao, Guo-long

2015-05-01

This research focused on the application of remotely sensed imagery from unmanned aerial vehicle (UAV) with high spatial resolution for the estimation of crown closure of moso bamboo forest based on the geometric-optical model, and analyzed the influence of unconstrained and fully constrained linear spectral mixture analysis (SMA) on the accuracy of the estimated results. The results demonstrated that the combination of UAV remotely sensed imagery and geometric-optical model could, to some degrees, achieve the estimation of crown closure. However, the different SMA methods led to significant differentiation in the estimation accuracy. Compared with unconstrained SMA, the fully constrained linear SMA method resulted in higher accuracy of the estimated values, with the coefficient of determination (R2) of 0.63 at 0.01 level, against the measured values acquired during the field survey. Root mean square error (RMSE) of approximate 0.04 was low, indicating that the usage of fully constrained linear SMA could bring about better results in crown closure estimation, which was closer to the actual condition in moso bamboo forest.

An assessment of aerosol optical properties from remote-sensing observations and regional chemistry-climate coupled models over Europe

Science.gov (United States)

Palacios-Peña, Laura; Baró, Rocío; Baklanov, Alexander; Balzarini, Alessandra; Brunner, Dominik; Forkel, Renate; Hirtl, Marcus; Honzak, Luka; María López-Romero, José; Montávez, Juan Pedro; Pérez, Juan Luis; Pirovano, Guido; San José, Roberto; Schröder, Wolfram; Werhahn, Johannes; Wolke, Ralf; Žabkar, Rahela; Jiménez-Guerrero, Pedro

2018-04-01

Atmospheric aerosols modify the radiative budget of the Earth due to their optical, microphysical and chemical properties, and are considered one of the most uncertain climate forcing agents. In order to characterise the uncertainties associated with satellite and modelling approaches to represent aerosol optical properties, mainly aerosol optical depth (AOD) and Ångström exponent (AE), their representation by different remote-sensing sensors and regional online coupled chemistry-climate models over Europe are evaluated. This work also characterises whether the inclusion of aerosol-radiation (ARI) or/and aerosol-cloud interactions (ACI) help improve the skills of modelling outputs.Two case studies were selected within the EuMetChem COST Action ES1004 framework when important aerosol episodes in 2010 all over Europe took place: a Russian wildfire episode and a Saharan desert dust outbreak that covered most of the Mediterranean Sea. The model data came from different regional air-quality-climate simulations performed by working group 2 of EuMetChem, which differed according to whether ARI or ACI was included or not. The remote-sensing data came from three different sensors: MODIS, OMI and SeaWIFS. The evaluation used classical statistical metrics to first compare satellite data versus the ground-based instrument network (AERONET) and then to evaluate model versus the observational data (both satellite and ground-based data).Regarding the uncertainty in the satellite representation of AOD, MODIS presented the best agreement with the AERONET observations compared to other satellite AOD observations. The differences found between remote-sensing sensors highlighted the uncertainty in the observations, which have to be taken into account when evaluating models. When modelling results were considered, a common trend for underestimating high AOD levels was observed. For the AE, models tended to underestimate its variability, except when considering a sectional approach in

Análisis de prestaciones de láseres en redes de acceso ópticas pasivas de siguiente generación NG-PON2 (Next Generation Passive Optical Networks)

OpenAIRE

Martín González, Daniel

2017-01-01

Este trabajo se centra en el estudio a nivel físico de las redes ópticas de acceso de siguiente generación (NG-PON2, Next Generation Passive Optical Networks), con las que se llegan a conseguir velocidades de transmisión de datos no inferiores a 40Gbits/s. Esto es gracias a la introducción de 4 longitudes de onda en cada sentido de transmisión. Además, estas redes tienen la ventaja añadida de conseguir transmisiones entre el OLT (Optical Line Termination) y las ONUs (Optical Network Units) de...

Passive thermo-optic feedback for robust athermal photonic systems

Science.gov (United States)

Rakich, Peter T.; Watts, Michael R.; Nielson, Gregory N.

2015-06-23

Thermal control devices, photonic systems and methods of stabilizing a temperature of a photonic system are provided. A thermal control device thermally coupled to a substrate includes a waveguide for receiving light, an absorption element optically coupled to the waveguide for converting the received light to heat and an optical filter. The optical filter is optically coupled to the waveguide and thermally coupled to the absorption element. An operating point of the optical filter is tuned responsive to the heat from the absorption element. When the operating point is less than a predetermined temperature, the received light is passed to the absorption element via the optical filter. When the operating point is greater than or equal to the predetermined temperature, the received light is transmitted out of the thermal control device via the optical filter, without being passed to the absorption element.

An optical system with potential for remote health monitoring of subsea machinery

International Nuclear Information System (INIS)

Jackson, D A

2009-01-01

A prototype fibre-optic sensing system is described with potential to remotely monitor the condition of three-phase variable frequency subsea motors and electric submersible pumps. An indication that the integrity of a powerful electric motor may be compromised can be gained by spectral analysis of the stator drive current, the phases of the currents, the measurement of vibration at specific locations on the motor and the temperature of the bearings. The optical interrogation system is based on an imbalanced Mach–Zehnder fibre interferometer, illuminated with a broadband source with fibre Bragg gratings (FBGs) used as the basic transducers for the current and vibration measurements. Signals were recovered at a distance of 7 km, for the 'in house' current sensor at an effective ac current of 500 A at frequencies from 10 to 1000 Hz with a S/N ratio of 45 dB, together with the relative phases between the currents. These signals were generated with a simulated high power three-phase electric motor. A commercial accelerometer was incorporated into the system which demonstrated a sensitivity of 1 mg Hz −1/2 also from 10 to 1000 Hz. As the interrogation system can only be used to detect dynamic signals, a second interrogation for quasi-static temperature measurements is required; although this was not deployed, possible applications other than bearing temperature measurement are considered

Bio-optical profiling floats as new observational tools for biogeochemical and ecosystem studies: Potential synergies with ocean color remote sensing

Energy Technology Data Exchange (ETDEWEB)

Claustre, H.; Bishop, J.; Boss, E.; Bernard, S.; Berthon, J.-F.; Coatanoan, C.; Johnson, K.; Lotiker, A.; Ulloa, O.; Perry, M.J.; D' Ortenzio, F.; D' andon, O.H.F.; Uitz, J.

2009-10-01

Profiling floats now represent a mature technology. In parallel with their emergence, the field of miniature, low power bio-optical and biogeochemical sensors is rapidly evolving. Over recent years, the bio-geochemical and bio-optical community has begun to benefit from the increase in observational capacities by developing profiling floats that allow the measurement of key biooptical variables and subsequent products of biogeochemical and ecosystem relevance like Chlorophyll a (Chla), optical backscattering or attenuation coefficients which are proxies of Particulate Organic Carbon (POC), Colored Dissolved Organic Matter (CDOM). Thanks to recent algorithmic improvements, new bio-optical variables such as backscattering coefficient or absorption by CDOM, at present can also be extracted from space observations of ocean color. In the future, an intensification of in situ measurements by bio-optical profiling floats would permit the elaboration of unique 3D/4D bio-optical climatologies, linking surface (remotely detected) properties to their vertical distribution (measured by autonomous platforms), with which key questions in the role of the ocean in climate could be addressed. In this context, the objective of the IOCCG (International Ocean Color Coordinating Group) BIO-Argo working group is to elaborate recommendations in view of a future use of bio-optical profiling floats as part of a network that would include a global array that could be 'Argo-relevant', and specific arrays that would have more focused objectives or regional targets. The overall network, realizing true multi-scale sustained observations of global marine biogeochemistry and biooptics, should satisfy the requirements for validation of ocean color remote sensing as well as the needs of a wider community investigating the impact of global change on biogeochemical cycles and ecosystems. Regarding the global profiling float array, the recommendation is that Chla as well as POC should be the

LWIR Microgrid Polarimeter for Remote Sensing Studies

Science.gov (United States)

2010-02-28

Polarimeter for Remote Sensing Studies 5b. GRANT NUMBER FA9550-08-1-0295 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 1. Scott Tyo 5e. TASK...and tested at the University of Arizona, and preliminary images are shown in this final report. 15. SUBJECT TERMS Remote Sensing , polarimetry 16...7.0 LWIR Microgrid Polarimeter for Remote Sensing Studies J. Scott Tyo College of Optical Sciences University of Arizona Tucson, AZ, 85721 tyo

Tropical Forest Monitoring in Southeast Asia Using Remotely Sensed Optical Time Series

DEFF Research Database (Denmark)

Grogan, Kenneth Joseph

of forest cover using satellite remote sensing technology. Recently, there has been a shift in data protection policy where rich archives of satellite imagery are now freely available. This has spurred a new era in satellite-based forest monitoring leading to advancements in optical time series processing...... markets. At the Landsat 30-m resolution, annual time series coupled with linear segmentation using LandTrendr was found to be an effective approach for monitoring forest disturbance, with moderate to high accuracies, depending on forest type. At the MODIS 250-m resolution, intra-annual time series...... global rubber markets can be linked to forest cover change, the effects of land policy in Cambodia, and beyond, have also had a major influence. It remains to be seen if intervention initiatives such as REDD+ can materialise over the coming years to make a meaningful contribution to tropical forest...

Remote sensing image fusion

CERN Document Server

Alparone, Luciano; Baronti, Stefano; Garzelli, Andrea

2015-01-01

A synthesis of more than ten years of experience, Remote Sensing Image Fusion covers methods specifically designed for remote sensing imagery. The authors supply a comprehensive classification system and rigorous mathematical description of advanced and state-of-the-art methods for pansharpening of multispectral images, fusion of hyperspectral and panchromatic images, and fusion of data from heterogeneous sensors such as optical and synthetic aperture radar (SAR) images and integration of thermal and visible/near-infrared images. They also explore new trends of signal/image processing, such as

A Multi-Band Analytical Algorithm for Deriving Absorption and Backscattering Coefficients from Remote-Sensing Reflectance of Optically Deep Waters

Science.gov (United States)

Lee, Zhong-Ping; Carder, Kendall L.

2001-01-01

A multi-band analytical (MBA) algorithm is developed to retrieve absorption and backscattering coefficients for optically deep waters, which can be applied to data from past and current satellite sensors, as well as data from hyperspectral sensors. This MBA algorithm applies a remote-sensing reflectance model derived from the Radiative Transfer Equation, and values of absorption and backscattering coefficients are analytically calculated from values of remote-sensing reflectance. There are only limited empirical relationships involved in the algorithm, which implies that this MBA algorithm could be applied to a wide dynamic range of waters. Applying the algorithm to a simulated non-"Case 1" data set, which has no relation to the development of the algorithm, the percentage error for the total absorption coefficient at 440 nm a (sub 440) is approximately 12% for a range of 0.012 - 2.1 per meter (approximately 6% for a (sub 440) less than approximately 0.3 per meter), while a traditional band-ratio approach returns a percentage error of approximately 30%. Applying it to a field data set ranging from 0.025 to 2.0 per meter, the result for a (sub 440) is very close to that using a full spectrum optimization technique (9.6% difference). Compared to the optimization approach, the MBA algorithm cuts the computation time dramatically with only a small sacrifice in accuracy, making it suitable for processing large data sets such as satellite images. Significant improvements over empirical algorithms have also been achieved in retrieving the optical properties of optically deep waters.

Fusion of radar and optical data for mapping and monitoring of water bodies

Science.gov (United States)

Jenerowicz, Agnieszka; Siok, Katarzyn

2017-10-01

Remote sensing techniques owe their great popularity to the possibility to obtain of rapid, accurate and information over large areas with optimal time, spatial and spectral resolutions. The main areas of interest for remote sensing research had always been concerned with environmental studies, especially water bodies monitoring. Many methods that are using visible and near- an infrared band of the electromagnetic spectrum had been already developed to detect surface water reservoirs. Moreover, the usage of an image obtained in visible and infrared spectrum allows quality monitoring of water bodies. Nevertheless, retrieval of water boundaries and mapping surface water reservoirs with optical sensors is still quite demanding. Therefore, the microwave data could be the perfect complement to data obtained with passive optical sensors to detect and monitor aquatic environment especially surface water bodies. This research presents the methodology to detect water bodies with open- source satellite imagery acquired with both optical and microwave sensors. The SAR Sentinel- 1 and multispectral Sentinel- 2 imagery were used to detect and monitor chosen reservoirs in Poland. In the research Level, 1 Sentinel- 2 data and Level 1 SAR images were used. SAR data were mainly used for mapping water bodies. Next, the results of water boundaries extraction with Sentinel-1 data were compared to results obtained after application of modified spectral indices for Sentinel- 2 data. The multispectral optical data can be used in the future for the evaluation of the quality of the reservoirs. Preliminary results obtained in the research had shown, that the fusion of data obtained with optical and microwave sensors allow for the complex detection of water bodies and could be used in the future quality monitoring of water reservoirs.

A self-sustainable winery, an advanced passive building and remote monitoring of environments in wineries

Directory of Open Access Journals (Sweden)

Roger Boulton

2017-08-01

Full Text Available The self-sustainable winery was conceived in 2006 and the intention was to create a building and its related utility systems that would operate independently from the energy and water grids and to eliminate hydrocarbon fuels from its operation, capture and sequester the carbon dioxide from its fermentations and create a zero carbon footprint facility. The winery was the highest scoring LEED building at any university when it was completed and the first LEED Platinum Winery in the USA. The adjacent Jess Jackson sustainable winery building is a highly passive research and utility space that will house the advanced energy and water systems that make this off-grid performance possible. Together these buildings will operate every daily in energy and water positive modes and at capacities, which exceed the demands even during the harvest season. The data system incorporated into these buildings for one hundred and fifty research fermentors, fourteen teaching fermentors will also monitor all energy, water and building activities in a secure, cloud-based software system that supports both web and handheld access, with the potential for bidirectional date and control functions. This data network has been extended to include real time monitoring of temperature, humidity, carbon dioxide and volatile organic compounds in five production areas within two commercial winery sites and two creamery facilities, located more than 100 km from Davis. This now provides an example of a distributed dynamic network for the monitoring of the built environment in remote commercial food and wine facilities.

Photometric device using optical fibers

International Nuclear Information System (INIS)

Boisde, Gilbert; Perez, J.-J.

1981-02-01

Remote measurements in radioactive environment are now possible with optical fibers. Measurement instruments developed by CEA are constitued of: - an optical probe (5 mm to 1 meter optical path length), - a photometric measurement device, - optical fiber links. 'TELEPHOT' is a photometric device for industrial installations. It is uses interferentiel filters for 2 to 5 simultaneous wave lengths. 'CRUDMETER' measures the muddiness of water. It can be equipped with a high sensitivity cell of 50 cm optical path length tested up to 250 bars. Coupling a double beam spectrophotometer to a remote optical probe, up to 1 meter optical path length, is carried out by means of an optical device using optical fibers links, eventually several hundred meter long. For these equipments special step index large core fibers, 1 to 1.5 mm in diameter, have been developed as well connectors. For industrial control and research these instruments offer new prospect thanks to optical fibers use [fr

Structural, optical spectroscopy, optical conductivity, dielectric ...

Indian Academy of Sciences (India)

13

different methods of preparation [36-41]. The electrical insulator materials with low refractive index and low absorption are needed for various optical devices, such as low loss waveguides, resonators, photonic crystals, distributed Bragg reflectors, light-emitting diodes, passive splitters, biosensors, attenuators and filters ...

Remote sensing of ecosystem health: opportunities, challenges, and future perspectives.

Science.gov (United States)

Li, Zhaoqin; Xu, Dandan; Guo, Xulin

2014-11-07

Maintaining a healthy ecosystem is essential for maximizing sustainable ecological services of the best quality to human beings. Ecological and conservation research has provided a strong scientific background on identifying ecological health indicators and correspondingly making effective conservation plans. At the same time, ecologists have asserted a strong need for spatially explicit and temporally effective ecosystem health assessments based on remote sensing data. Currently, remote sensing of ecosystem health is only based on one ecosystem attribute: vigor, organization, or resilience. However, an effective ecosystem health assessment should be a comprehensive and dynamic measurement of the three attributes. This paper reviews opportunities of remote sensing, including optical, radar, and LiDAR, for directly estimating indicators of the three ecosystem attributes, discusses the main challenges to develop a remote sensing-based spatially-explicit comprehensive ecosystem health system, and provides some future perspectives. The main challenges to develop a remote sensing-based spatially-explicit comprehensive ecosystem health system are: (1) scale issue; (2) transportability issue; (3) data availability; and (4) uncertainties in health indicators estimated from remote sensing data. However, the Radarsat-2 constellation, upcoming new optical sensors on Worldview-3 and Sentinel-2 satellites, and improved technologies for the acquisition and processing of hyperspectral, multi-angle optical, radar, and LiDAR data and multi-sensoral data fusion may partly address the current challenges.

Remote Sensing of Ecosystem Health: Opportunities, Challenges, and Future Perspectives

Directory of Open Access Journals (Sweden)

Zhaoqin Li

2014-11-01

Full Text Available Maintaining a healthy ecosystem is essential for maximizing sustainable ecological services of the best quality to human beings. Ecological and conservation research has provided a strong scientific background on identifying ecological health indicators and correspondingly making effective conservation plans. At the same time, ecologists have asserted a strong need for spatially explicit and temporally effective ecosystem health assessments based on remote sensing data. Currently, remote sensing of ecosystem health is only based on one ecosystem attribute: vigor, organization, or resilience. However, an effective ecosystem health assessment should be a comprehensive and dynamic measurement of the three attributes. This paper reviews opportunities of remote sensing, including optical, radar, and LiDAR, for directly estimating indicators of the three ecosystem attributes, discusses the main challenges to develop a remote sensing-based spatially-explicit comprehensive ecosystem health system, and provides some future perspectives. The main challenges to develop a remote sensing-based spatially-explicit comprehensive ecosystem health system are: (1 scale issue; (2 transportability issue; (3 data availability; and (4 uncertainties in health indicators estimated from remote sensing data. However, the Radarsat-2 constellation, upcoming new optical sensors on Worldview-3 and Sentinel-2 satellites, and improved technologies for the acquisition and processing of hyperspectral, multi-angle optical, radar, and LiDAR data and multi-sensoral data fusion may partly address the current challenges.

Remote Sensing of Ecosystem Health: Opportunities, Challenges, and Future Perspectives

Science.gov (United States)

Li, Zhaoqin; Xu, Dandan; Guo, Xulin

2014-01-01

Maintaining a healthy ecosystem is essential for maximizing sustainable ecological services of the best quality to human beings. Ecological and conservation research has provided a strong scientific background on identifying ecological health indicators and correspondingly making effective conservation plans. At the same time, ecologists have asserted a strong need for spatially explicit and temporally effective ecosystem health assessments based on remote sensing data. Currently, remote sensing of ecosystem health is only based on one ecosystem attribute: vigor, organization, or resilience. However, an effective ecosystem health assessment should be a comprehensive and dynamic measurement of the three attributes. This paper reviews opportunities of remote sensing, including optical, radar, and LiDAR, for directly estimating indicators of the three ecosystem attributes, discusses the main challenges to develop a remote sensing-based spatially-explicit comprehensive ecosystem health system, and provides some future perspectives. The main challenges to develop a remote sensing-based spatially-explicit comprehensive ecosystem health system are: (1) scale issue; (2) transportability issue; (3) data availability; and (4) uncertainties in health indicators estimated from remote sensing data. However, the Radarsat-2 constellation, upcoming new optical sensors on Worldview-3 and Sentinel-2 satellites, and improved technologies for the acquisition and processing of hyperspectral, multi-angle optical, radar, and LiDAR data and multi-sensoral data fusion may partly address the current challenges. PMID:25386759

Multilayer Markov Random Field models for change detection in optical remote sensing images

Science.gov (United States)

Benedek, Csaba; Shadaydeh, Maha; Kato, Zoltan; Szirányi, Tamás; Zerubia, Josiane

2015-09-01

In this paper, we give a comparative study on three Multilayer Markov Random Field (MRF) based solutions proposed for change detection in optical remote sensing images, called Multicue MRF, Conditional Mixed Markov model, and Fusion MRF. Our purposes are twofold. On one hand, we highlight the significance of the focused model family and we set them against various state-of-the-art approaches through a thematic analysis and quantitative tests. We discuss the advantages and drawbacks of class comparison vs. direct approaches, usage of training data, various targeted application fields and different ways of Ground Truth generation, meantime informing the Reader in which roles the Multilayer MRFs can be efficiently applied. On the other hand we also emphasize the differences between the three focused models at various levels, considering the model structures, feature extraction, layer interpretation, change concept definition, parameter tuning and performance. We provide qualitative and quantitative comparison results using principally a publicly available change detection database which contains aerial image pairs and Ground Truth change masks. We conclude that the discussed models are competitive against alternative state-of-the-art solutions, if one uses them as pre-processing filters in multitemporal optical image analysis. In addition, they cover together a large range of applications, considering the different usage options of the three approaches.

Energy-saving scheme based on downstream packet scheduling in ethernet passive optical networks

Science.gov (United States)

Zhang, Lincong; Liu, Yejun; Guo, Lei; Gong, Xiaoxue

2013-03-01

With increasing network sizes, the energy consumption of Passive Optical Networks (PONs) has grown significantly. Therefore, it is important to design effective energy-saving schemes in PONs. Generally, energy-saving schemes have focused on sleeping the low-loaded Optical Network Units (ONUs), which tends to bring large packet delays. Further, the traditional ONU sleep modes are not capable of sleeping the transmitter and receiver independently, though they are not required to transmit or receive packets. Clearly, this approach contributes to wasted energy. Thus, in this paper, we propose an Energy-Saving scheme that is based on downstream Packet Scheduling (ESPS) in Ethernet PON (EPON). First, we design both an algorithm and a rule for downstream packet scheduling at the inter- and intra-ONU levels, respectively, to reduce the downstream packet delay. After that, we propose a hybrid sleep mode that contains not only ONU deep sleep mode but also independent sleep modes for the transmitter and the receiver. This ensures that the energy consumed by the ONUs is minimal. To realize the hybrid sleep mode, a modified GATE control message is designed that involves 10 time points for sleep processes. In ESPS, the 10 time points are calculated according to the allocated bandwidths in both the upstream and the downstream. The simulation results show that ESPS outperforms traditional Upstream Centric Scheduling (UCS) scheme in terms of energy consumption and the average delay for both real-time and non-real-time packets downstream. The simulation results also show that the average energy consumption of each ONU in larger-sized networks is less than that in smaller-sized networks; hence, our ESPS is better suited for larger-sized networks.

Mapping Daily and Maximum Flood Extents at 90-m Resolution During Hurricanes Harvey and Irma Using Passive Microwave Remote Sensing

Science.gov (United States)

Galantowicz, J. F.; Picton, J.; Root, B.

2017-12-01

Passive microwave remote sensing can provided a distinct perspective on flood events by virtue of wide sensor fields of view, frequent observations from multiple satellites, and sensitivity through clouds and vegetation. During Hurricanes Harvey and Irma, we used AMSR2 (Advanced Microwave Scanning Radiometer 2, JAXA) data to map flood extents starting from the first post-storm rain-free sensor passes. Our standard flood mapping algorithm (FloodScan) derives flooded fraction from 22-km microwave data (AMSR2 or NASA's GMI) in near real time and downscales it to 90-m resolution using a database built from topography, hydrology, and Global Surface Water Explorer data and normalized to microwave data footprint shapes. During Harvey and Irma we tested experimental versions of the algorithm designed to map the maximum post-storm flood extent rapidly and made a variety of map products available immediately for use in storm monitoring and response. The maps have several unique features including spanning the entire storm-affected area and providing multiple post-storm updates as flood water shifted and receded. From the daily maps we derived secondary products such as flood duration, maximum flood extent (Figure 1), and flood depth. In this presentation, we describe flood extent evolution, maximum extent, and local details as detected by the FloodScan algorithm in the wake of Harvey and Irma. We compare FloodScan results to other available flood mapping resources, note observed shortcomings, and describe improvements made in response. We also discuss how best-estimate maps could be updated in near real time by merging FloodScan products and data from other remote sensing systems and hydrological models.

An IoT Reader for Wireless Passive Electromagnetic Sensors.

Science.gov (United States)

Galindo-Romera, Gabriel; Carnerero-Cano, Javier; Martínez-Martínez, José Juan; Herraiz-Martínez, Francisco Javier

2017-03-28

In the last years, many passive electromagnetic sensors have been reported. Some of these sensors are used for measuring harmful substances. Moreover, the response of these sensors is usually obtained with laboratory equipment. This approach highly increases the total cost and complexity of the sensing system. In this work, a novel low-cost and portable Internet-of-Things (IoT) reader for passive wireless electromagnetic sensors is proposed. The reader is used to interrogate the sensors within a short-range wireless link avoiding the direct contact with the substances under test. The IoT functionalities of the reader allows remote sensing from computers and handheld devices. For that purpose, the proposed design is based on four functional layers: the radiating layer, the RF interface, the IoT mini-computer and the power unit. In this paper a demonstrator of the proposed reader is designed and manufactured. The demonstrator shows, through the remote measurement of different substances, that the proposed system can estimate the dielectric permittivity. It has been demonstrated that a linear approximation with a small error can be extracted from the reader measurements. It is remarkable that the proposed reader can be used with other type of electromagnetic sensors, which transduce the magnitude variations in the frequency domain.

Passive photonic alignment with submicrometer repeatability and accuracy

NARCIS (Netherlands)

Gurp, J.F.C.; Tichem, M; Staufer, U.; Zhao, J.

2013-01-01

In this paper, we report on passive alignment with submicrometer accuracy of two photonic chips on a silicon optical bench. An effective design principle to minimize the tolerance chain is presented and applied to a case study. The chips have been successfully manufactured and an experimental setup

Surface-enhanced Raman fiberoptic sensors for remote monitoring

Energy Technology Data Exchange (ETDEWEB)

Stokes, D.L.; Alarie, J.P.; Vo-Dinh, T. [Oak Ridge National Lab., TN (United States). Health Sciences Research Div.

1995-09-01

A new sensor design for remote surface-enhanced Raman scattering (SERS) measurements has been developed for environmental applications. The design features the modification of an optical fiber using layers of alumina microparticles and silver coatings for inducing the SERS effect at the sensing probe. A single fiber carries both the laser excitation and the SERS signal radiation, keeping optical parameters at the remote tip simple and consistent. The small tip size achievable with this configuration also demonstrates potential of this new design as a microsensor for in-situ measurement in microenvironments. Details of sensor tip fabrication and optical system design are described. SERS spectra of aqueous environmental samples acquired in-situ using the SERS sensor are also presented to illustrate the effectiveness of the SERS sensor.

Thermodynamic phase profiles of optically thin midlatitude cloud and their relation to temperature

Energy Technology Data Exchange (ETDEWEB)

Naud, C. M.; Del Genio, Anthony D.; Haeffelin, M.; Morille, Y.; Noel, V.; Dupont, Jean-Charles; Turner, David D.; Lo, Chaomei; Comstock, Jennifer M.

2010-06-03

Winter cloud phase and temperature profiles derived from ground-based lidar depolarization and radiosonde measurements are analyzed for two midlatitude locations: the United States Atmospheric Radiation Measurement Program Southern Great Plains (SGP) site and the Site Instrumental de Recherche par Télédétection Atmosphérique (SIRTA) in France. Because lidars are attenuated in optically thick clouds, the dataset only includes optically thin clouds (optical thickness < 3). At SGP, 57% of the clouds observed with the lidar in the temperature range 233-273 K are either completely liquid or completely glaciated, while at SIRTA only 42% of the observed clouds are single phase, based on a depolarization ratio threshold of 11% for differentiating liquid from ice. Most optically thin mixed phase clouds show an ice layer at cloud top, and clouds with liquid at cloud top are less frequent. The relationship between ice phase occurrence and temperature only slightly changes between cloud base and top. At both sites liquid is more prevalent at colder temperatures than has been found previously in aircraft flights through frontal clouds of greater optical thicknesses. Liquid in clouds persists to colder temperatures at SGP than SIRTA. This information on the average temperatures of mixed phase clouds at both locations complements earlier passive satellite remote sensing measurements that sample cloud phase near cloud top and for a wider range of cloud optical thicknesses.

Passive linear-optics 640 Gbit/s logic NOT gate

DEFF Research Database (Denmark)

Maram, Reza; Kong, Deming; Galili, Michael

2015-01-01

We experimentally demonstrate a 640 Gbit/s all-optical NOT gate for high-speed telecommunication on-off-keying (OOK) data signals. We employ linear optical signal processing based on spectral phase-only (all-pass) optical filtering to perform the target logic NOT operation....

Optical Communication System for Remote Monitoring and Adaptive Control of Distributed Ground Sensors Exhibiting Collective Intelligence

Energy Technology Data Exchange (ETDEWEB)

Cameron, S.M.; Stantz, K.M.; Trahan, M.W.; Wagner, J.S.

1998-11-01

Comprehensive management of the battle-space has created new requirements in information management, communication, and interoperability as they effect surveillance and situational awareness. The objective of this proposal is to expand intelligent controls theory to produce a uniquely powerful implementation of distributed ground-based measurement incorporating both local collective behavior, and interoperative global optimization for sensor fusion and mission oversight. By using a layered hierarchal control architecture to orchestrate adaptive reconfiguration of autonomous robotic agents, we can improve overall robustness and functionality in dynamic tactical environments without information bottlenecks. In this concept, each sensor is equipped with a miniaturized optical reflectance modulator which is interactively monitored as a remote transponder using a covert laser communication protocol from a remote mothership or operative. Robot data-sharing at the ground level can be leveraged with global evaluation criteria, including terrain overlays and remote imaging data. Information sharing and distributed intelli- gence opens up a new class of remote-sensing applications in which small single-function autono- mous observers at the local level can collectively optimize and measure large scale ground-level signals. AS the need for coverage and the number of agents grows to improve spatial resolution, cooperative behavior orchestrated by a global situational awareness umbrella will be an essential ingredient to offset increasing bandwidth requirements within the net. A system of the type described in this proposal will be capable of sensitively detecting, tracking, and mapping spatial distributions of measurement signatures which are non-stationary or obscured by clutter and inter- fering obstacles by virtue of adaptive reconfiguration. This methodology could be used, for example, to field an adaptive ground-penetrating radar for detection of underground structures in

Optical Remote Sensing Potentials for Looting Detection

Directory of Open Access Journals (Sweden)

Athos Agapiou

2017-10-01

Full Text Available Looting of archaeological sites is illegal and considered a major anthropogenic threat for cultural heritage, entailing undesirable and irreversible damage at several levels, such as landscape disturbance, heritage destruction, and adverse social impact. In recent years, the employment of remote sensing technologies using ground-based and/or space-based sensors has assisted in dealing with this issue. Novel remote sensing techniques have tackled heritage destruction occurring in war-conflicted areas, as well as illicit archeological activity in vast areas of archaeological interest with limited surveillance. The damage performed by illegal activities, as well as the scarcity of reliable information are some of the major concerns that local stakeholders are facing today. This study discusses the potential use of remote sensing technologies based on the results obtained for the archaeological landscape of Ayios Mnason in Politiko village, located in Nicosia district, Cyprus. In this area, more than ten looted tombs have been recorded in the last decade, indicating small-scale, but still systematic, looting. The image analysis, including vegetation indices, fusion, automatic extraction after object-oriented classification, etc., was based on high-resolution WorldView-2 multispectral satellite imagery and RGB high-resolution aerial orthorectified images. Google Earth© images were also used to map and diachronically observe the site. The current research also discusses the potential for wider application of the presented methodology, acting as an early warning system, in an effort to establish a systematic monitoring tool for archaeological areas in Cyprus facing similar threats.

A telescopic cinema sound camera for observing high altitude aerospace vehicles

Science.gov (United States)

Slater, Dan

2014-09-01

Rockets and other high altitude aerospace vehicles produce interesting visual and aural phenomena that can be remotely observed from long distances. This paper describes a compact, passive and covert remote sensing system that can produce high resolution sound movies at >100 km viewing distances. The telescopic high resolution camera is capable of resolving and quantifying space launch vehicle dynamics including plume formation, staging events and payload fairing jettison. Flight vehicles produce sounds and vibrations that modulate the local electromagnetic environment. These audio frequency modulations can be remotely sensed by passive optical and radio wave detectors. Acousto-optic sensing methods were primarily used but an experimental radioacoustic sensor using passive micro-Doppler radar techniques was also tested. The synchronized combination of high resolution flight vehicle imagery with the associated vehicle sounds produces a cinema like experience that that is useful in both an aerospace engineering and a Hollywood film production context. Examples of visual, aural and radar observations of the first SpaceX Falcon 9 v1.1 rocket launch are shown and discussed.

Design of all-optical flip-flop by using optical bistability in passive micro-rings

International Nuclear Information System (INIS)

Karimi, M.; Abolfazli, M. J.; Rouholamini Nejad, H.; Bahrampour, A.

2007-01-01

In this paper at first, Optical bistability in the micro ring resonators in the presence of Kerr and two-photon absorption effects is studied and also, attenuation in micro rings with these nonlinear effects is calculated. An all-optical R-S flip-flop is designed by using optical bistability. Conditions for SET and RESET signals are calculated and their dependences on the optical parameters of micro rings are investigated.

Directional amplifier in an optomechanical system with optical gain

Science.gov (United States)

Jiang, Cheng; Song, L. N.; Li, Yong

2018-05-01

Directional amplifiers are crucial nonreciprocal devices in both classical and quantum information processing. Here we propose a scheme for realizing a directional amplifier between optical and microwave fields based on an optomechanical system with optical gain, where an active optical cavity and two passive microwave cavities are coupled to a common mechanical resonator via radiation pressure. The two passive cavities are coupled via hopping interaction to facilitate the directional amplification between the active and passive cavities. We obtain the condition of achieving optical directional amplification and find that the direction of amplification can be controlled by the phase differences between the effective optomechanical couplings. The effects of the gain rate of the active cavity and the effective coupling strengths on the maximum gain of the amplifier are discussed. We show that the noise added to this amplifier can be greatly suppressed in the large cooperativity limit.

Design of the inboard passive stabilizer for TPX

International Nuclear Information System (INIS)

Hoffmann, E.; Boonstra, R.; Baxi, C.B.; Chin, E.; Drees, L.; Lee, W.; Redler, K.L.; Reis, E.E.; Bialek, J.

1995-01-01

The Inboard Passive Stabilizer (IPS) is part of the plasma stabilizing system built into the TPX. Its purpose is to provide passive stabilization of the plasma vertical instability on short time scales. With carbon fiber composite (CFC) armor tiles it serves as a startup limiter, protects the vacuum vessel from radiation heat load during steady state operation and also functions as Neutral Beam armor. The inboard passive stabilizer is a saddle coil, constructed of a ring of copper plates, armored with CFC tiles, that surrounds the inner vacuum vessel at the midplane. The design of the plates, the support structure, cooling lines, CFC tiles and tile attach method is described. Tiles that experience only the normal heat load of 0.4 MW/m 2 are attached with mechanical fasteners. Tiles in the neutral beam shine through area are exposed to as much as 1.7 MW/m 2 and are brazed to the IPS. Significant forces are generated in the plates by the stabilization currents as well as during the frequent bakeout cycles. These plates are required to be fully remotely handled, including tile replacement, and the influence of this requirement on the design is discussed

Impact of the Sun on Remote Sensing of Sea Surface Salinity from Space

National Research Council Canada - National Science Library

Le Vine, David M; Abraham, Saji; Wentz, F; Lagerloef, G. S

2005-01-01

... to monitor soil moisture and sea surface salinity. Radiation from the sun can impact passive remote sensing systems in several ways, including line-of-sight radiation that comes directly from the sun and enters through antenna side lobes...

Coastal High-resolution Observations and Remote Sensing of Ecosystems (C-HORSE)

Science.gov (United States)

Guild, Liane

2016-01-01

Coastal benthic marine ecosystems, such as coral reefs, seagrass beds, and kelp forests are highly productive as well as ecologically and commercially important resources. These systems are vulnerable to degraded water quality due to coastal development, terrestrial run-off, and harmful algal blooms. Measurements of these features are important for understanding linkages with land-based sources of pollution and impacts to coastal ecosystems. Challenges for accurate remote sensing of coastal benthic (shallow water) ecosystems and water quality are complicated by atmospheric scattering/absorption (approximately 80+% of the signal), sun glint from the sea surface, and water column scattering (e.g., turbidity). Further, sensor challenges related to signal to noise (SNR) over optically dark targets as well as insufficient radiometric calibration thwart the value of coastal remotely-sensed data. Atmospheric correction of satellite and airborne remotely-sensed radiance data is crucial for deriving accurate water-leaving radiance in coastal waters. C-HORSE seeks to optimize coastal remote sensing measurements by using a novel airborne instrument suite that will bridge calibration, validation, and research capabilities of bio-optical measurements from the sea to the high altitude remote sensing platform. The primary goal of C-HORSE is to facilitate enhanced optical observations of coastal ecosystems using state of the art portable microradiometers with 19 targeted spectral channels and flight planning to optimize measurements further supporting current and future remote sensing missions.

Four-port mode-selective silicon optical router for on-chip optical interconnect.

Science.gov (United States)

Jia, Hao; Zhou, Ting; Fu, Xin; Ding, Jianfeng; Zhang, Lei; Yang, Lin

2018-04-16

We propose and demonstrate a four-port mode-selective optical router on a silicon-on-insulator platform. The passive routing property ensures that the router consumes no power to establish the optical links. For each port, input signals with different modes are selectively routed to the target ports through the pre-designed architecture. In general, the device intrinsically supports broadcasting of multiplexed signals from one port to the other three ports through mode division multiplexing. In some applications, the input signal from one port would only be sent to another port as in reconfigurable optical routers. The prototype is constructed by mode multiplexers/de-multiplexers and single-mode interconnect waveguides between them. The insertion losses for all optical links are lower than 8.0 dB, and the largest optical crosstalk values are lower than -18.7 dB and -22.0 dB for the broadcasting and port-to-port routing modes, respectively, at the wavelength range of 1525-1565 nm. In order to verify the routing functionality, a 40-Gbps bidirectional data transmission experiment is performed. The device offers a promising building block for passive routing by utilizing the dimension of the modes.

MEMS: A new approach to micro-optics

Energy Technology Data Exchange (ETDEWEB)

Sniegowski, J.J.

1997-12-31

MicroElectroMechanical Systems (MEMS) and their fabrication technologies provide great opportunities for application to micro-optical systems (MOEMS). Implementing MOEMS technology ranges from simple, passive components to complicated, active systems. Here, an overview of polysilicon surface micromachining MEMS combined with optics is presented. Recent advancements to the technology, which may enhance its appeal for micro-optics applications are emphasized. Of all the MEMS fabrication technologies, polysilicon surface micromachining technology has the greatest basis in and leverages the most the infrastructure for silicon integrated circuit fabrication. In that respect, it provides the potential for very large volume, inexpensive production of MOEMS. This paper highlights polysilicon surface micromachining technology in regards to its capability to provide both passive and active mechanical elements with quality optical elements.

Traffic classification with passive measurement

OpenAIRE

Pham, Hoang Phong

2005-01-01

Abstract This is a master thesis from a collaboration between Oslo University College and Uninett Research. Uninett have a passive monitoring device on a 2.5 Gbps backbone link between Trondheim and Narvik. They uses measurement with optical splitters and specialized measuring interfaces to trace traffic with Gigabit speed. We would like to investigate the structure and patterns in these data. It is of special interest to classify the traffic belonging to different services and protocols. ...

Verifying Air Force Weather Passive Satellite Derived Cloud Analysis Products

Science.gov (United States)

Nobis, T. E.

2017-12-01

Air Force Weather (AFW) has developed an hourly World-Wide Merged Cloud Analysis (WWMCA) using imager data from 16 geostationary and polar-orbiting satellites. The analysis product contains information on cloud fraction, height, type and various optical properties including optical depth and integrated water path. All of these products are derived using a suite of algorithms which rely exclusively on passively sensed data from short, mid and long wave imager data. The system integrates satellites with a wide-range of capabilities, from the relatively simple two-channel OLS imager to the 16 channel ABI/AHI to create a seamless global analysis in real time. Over the last couple of years, AFW has started utilizing independent verification data from active sensed cloud measurements to better understand the performance limitations of the WWMCA. Sources utilized include space based lidars (CALIPSO, CATS) and radar (CloudSat) as well as ground based lidars from the Department of Energy ARM sites and several European cloud radars. This work will present findings from our efforts to compare active and passive sensed cloud information including comparison techniques/limitations as well as performance of the passive derived cloud information against the active.

Underwater fiber-wireless communication with a passive front end

Science.gov (United States)

Xu, Jing; Sun, Bin; Lyu, Weichao; Kong, Meiwei; Sarwar, Rohail; Han, Jun; Zhang, Wei; Deng, Ning

2017-11-01

We propose and experimentally demonstrate a novel concept on underwater fiber-wireless (Fi-Wi) communication system with a fully passive wireless front end. A low-cost step-index (SI) plastic optical fiber (POF) together with a passive collimating lens at the front end composes the underwater Fi-Wi architecture. We have achieved a 1.71-Gb/s transmission at a mean BER of 4.97 × 10-3 (1.30 × 10-3 when using power loading) over a 50-m SI-POF and 2-m underwater wireless channel using orthogonal frequency division multiplexing (OFDM). Although the wireless part is very short, it actually plays a crucial role in practical underwater implementation, especially in deep sea. Compared with the wired solution (e.g. using a 52-m POF cable without the UWOC part), the proposed underwater Fi-Wi scheme can save optical wet-mate connectors that are sophisticated, very expensive and difficult to install in deep ocean. By combining high-capacity robust POF with the mobility and ubiquity of underwater wireless optical communication (UWOC), the proposed underwater Fi-Wi technology will find wide application in ocean exploration.

The theoretical study of passive and active optical devices via planewave based transfer (scattering) matrix method and other approaches

Energy Technology Data Exchange (ETDEWEB)

Zhuo, Ye [Iowa State Univ., Ames, IA (United States)

2011-01-01

In this thesis, we theoretically study the electromagnetic wave propagation in several passive and active optical components and devices including 2-D photonic crystals, straight and curved waveguides, organic light emitting diodes (OLEDs), and etc. Several optical designs are also presented like organic photovoltaic (OPV) cells and solar concentrators. The first part of the thesis focuses on theoretical investigation. First, the plane-wave-based transfer (scattering) matrix method (TMM) is briefly described with a short review of photonic crystals and other numerical methods to study them (Chapter 1 and 2). Next TMM, the numerical method itself is investigated in details and developed in advance to deal with more complex optical systems. In chapter 3, TMM is extended in curvilinear coordinates to study curved nanoribbon waveguides. The problem of a curved structure is transformed into an equivalent one of a straight structure with spatially dependent tensors of dielectric constant and magnetic permeability. In chapter 4, a new set of localized basis orbitals are introduced to locally represent electromagnetic field in photonic crystals as alternative to planewave basis. The second part of the thesis focuses on the design of optical devices. First, two examples of TMM applications are given. The first example is the design of metal grating structures as replacements of ITO to enhance the optical absorption in OPV cells (chapter 6). The second one is the design of the same structure as above to enhance the light extraction of OLEDs (chapter 7). Next, two design examples by ray tracing method are given, including applying a microlens array to enhance the light extraction of OLEDs (chapter 5) and an all-angle wide-wavelength design of solar concentrator (chapter 8). In summary, this dissertation has extended TMM which makes it capable of treating complex optical systems. Several optical designs by TMM and ray tracing method are also given as a full complement of this

Compact 84 GHz passive mode-locked fiber laser using dual-fiber coupled fused-quartz microresonator

Science.gov (United States)

Liu, Tze-An; Hsu, Yung; Chow, Chi-Wai; Chuang, Yi-Chen; Ting, Wei-Jo; Wang, Bo-Chun; Peng, Jin-Long; Chen, Guan-Hong; Chang, Yuan-Chia

2017-10-01

We propose and demonstrate a compact and portable-size 84-GHz passive mode-locked fiber laser, in which a dual-fiber coupled fused-quartz microresonator is employed as the intracavity optical comb filter as well as the optical nonlinear material for optical frequency comb generation. About eight coherent optical tones can be generated in the proposed fiber laser. The 20-dB bandwidth is larger than 588 GHz. The full-width half-maximum pulse-width of the proposed laser is 2.5 ps. We also demonstrate the feasibility of using the proposed passive mode-locked fiber laser to carry a 5-Gbit/s on-off-keying signal and transmit over 20-km standard single mode fiber. A 7% forward error correction requirement can be achieved, showing the proposed fiber laser can be a potential candidate for fiber-wireless applications.

Radicals and ions controlling by adjusting the antenna-substrate distance in a-Si:H deposition using a planar ICP for c-Si surface passivation

Energy Technology Data Exchange (ETDEWEB)

Zhou, H.P., E-mail: haipzhou@uestc.edu.cn [School of Energy Science and Engineering, University of Electronic Science and Technology of China, 2006 Xiyuan Ave., West High-Tech Zone, Chengdu, Sichuan, 611731 (China); Plasma Sources and Application Center, NIE, and Institute of Advanced Studies, Nanyang Technological University, 637616 (Singapore); Xu, S., E-mail: shuyan.xu@nie.edu.sg [Plasma Sources and Application Center, NIE, and Institute of Advanced Studies, Nanyang Technological University, 637616 (Singapore); Xu, M. [Key Laboratory of Information Materials of Sichuan Province & School of Electrical and Information Engineering, Southwest University for Nationalities, Chengdu, 610041 (China); Xu, L.X.; Wei, D.Y. [Plasma Sources and Application Center, NIE, and Institute of Advanced Studies, Nanyang Technological University, 637616 (Singapore); Xiang, Y. [School of Energy Science and Engineering, University of Electronic Science and Technology of China, 2006 Xiyuan Ave., West High-Tech Zone, Chengdu, Sichuan, 611731 (China); Xiao, S.Q. [Key Laboratory of Advanced Process Control for Light Industry (Ministry of Education), Department of Electronic Engineering, Jiangnan University, Wuxi, 214122 (China)

2017-02-28

Highlights: • A planar ICP was used to grow a-Si:H films for c-Si surface passivation. • The direct- and remote-plasma was compared for high-quality c-Si surface passivation. • The remote ICP with controlled plasma species and ion bombardments is preferable for the surface passivation of c-Si. - Abstract: Being a key issue in the research and fabrication of silicon heterojunction (SHJ) solar cells, crystalline silicon (c-Si) surface passivation is theoretically and technologically intricate due to its complicate dependence on plasma characteristics, material properties, and plasma-material interactions. Here amorphous silicon (a-Si:H) grown by a planar inductively coupled plasma (ICP) reactor working under different antenna-substrate distances of d was used for the surface passivation of low-resistivity p-type c-Si. It is found that the microstructures (i.e., the crystallinity, Si-H bonding configuration etc.) and passivation function on c-Si of the deposited a-Si:H were profoundly influenced by the parameter of d, which primarily determines the types of growing precursors of SiH{sub n}/H contributing to the film growth and the interaction between the plasma and growing surface. c-Si surface passivation is analyzed in terms of the d-dependent a-Si:H properties and plasma characteristics. The controlling of radical types and ion bombardment on the growing surface through adjusting parameter d is emphasized.

Compact fiber optic gyroscopes for platform stabilization

Science.gov (United States)

Dickson, William C.; Yee, Ting K.; Coward, James F.; McClaren, Andrew; Pechner, David A.

2013-09-01

SA Photonics has developed a family of compact Fiber Optic Gyroscopes (FOGs) for platform stabilization applications. The use of short fiber coils enables the high update rates required for stabilization applications but presents challenges to maintain high performance. We are able to match the performance of much larger FOGs by utilizing several innovative technologies. These technologies include source noise reduction to minimize Angular Random Walk (ARW), advanced digital signal processing that minimizes bias drift at high update rates, and advanced passive thermal packaging that minimizes temperature induced bias drift while not significantly affecting size, weight, or power. In addition, SA Photonics has developed unique distributed FOG packaging technologies allowing the FOG electronics and photonics to be packaged remotely from the sensor head or independent axis heads to minimize size, weight, and power at the sensing location(s). The use of these technologies has resulted in high performance, including ARW less than 0.001 deg/rt-hr and bias drift less than 0.004 deg/hr at an update rate of 10 kHz, and total packaged volume less than 30 cu. in. for a 6 degree of freedom FOG-based IMU. Specific applications include optical beam stabilization for LIDAR and LADAR, beam stabilization for long-range free-space optical communication, Optical Inertial Reference Units for HEL stabilization, and Ka band antenna pedestal pointing and stabilization. The high performance of our FOGs also enables their use in traditional navigation and positioning applications. This paper will review the technologies enabling our high-performance compact FOGs, and will provide performance test results.

A survey on object detection in optical remote sensing images

Science.gov (United States)

Cheng, Gong; Han, Junwei

2016-07-01

Object detection in optical remote sensing images, being a fundamental but challenging problem in the field of aerial and satellite image analysis, plays an important role for a wide range of applications and is receiving significant attention in recent years. While enormous methods exist, a deep review of the literature concerning generic object detection is still lacking. This paper aims to provide a review of the recent progress in this field. Different from several previously published surveys that focus on a specific object class such as building and road, we concentrate on more generic object categories including, but are not limited to, road, building, tree, vehicle, ship, airport, urban-area. Covering about 270 publications we survey (1) template matching-based object detection methods, (2) knowledge-based object detection methods, (3) object-based image analysis (OBIA)-based object detection methods, (4) machine learning-based object detection methods, and (5) five publicly available datasets and three standard evaluation metrics. We also discuss the challenges of current studies and propose two promising research directions, namely deep learning-based feature representation and weakly supervised learning-based geospatial object detection. It is our hope that this survey will be beneficial for the researchers to have better understanding of this research field.

Towards All-optical Light Robotics

DEFF Research Database (Denmark)

Glückstad, Jesper

In the Programmable Phase Optics (PPO) group at DTU Fotonik we pioneered the new and emerging research area of so-called Light Robotics including the new and disruptive 3D-printed micro-tools coined Wave-guided Optical Waveguides that can be real-time optically manipulated and “remote-controlled”......In the Programmable Phase Optics (PPO) group at DTU Fotonik we pioneered the new and emerging research area of so-called Light Robotics including the new and disruptive 3D-printed micro-tools coined Wave-guided Optical Waveguides that can be real-time optically manipulated and “remote......-controlled” in a volume with six-degrees-of-freedom. To be exploring the full potential of this new drone-like 3D light robotics approach in challenging microscopic geometries requires a versatile and real-time reconfigurable light coupling that can dynamically track a plurality of “light robots” in 3D to ensure...

Ship detection in optical remote sensing images based on deep convolutional neural networks

Science.gov (United States)

Yao, Yuan; Jiang, Zhiguo; Zhang, Haopeng; Zhao, Danpei; Cai, Bowen

2017-10-01

Automatic ship detection in optical remote sensing images has attracted wide attention for its broad applications. Major challenges for this task include the interference of cloud, wave, wake, and the high computational expenses. We propose a fast and robust ship detection algorithm to solve these issues. The framework for ship detection is designed based on deep convolutional neural networks (CNNs), which provide the accurate locations of ship targets in an efficient way. First, the deep CNN is designed to extract features. Then, a region proposal network (RPN) is applied to discriminate ship targets and regress the detection bounding boxes, in which the anchors are designed by intrinsic shape of ship targets. Experimental results on numerous panchromatic images demonstrate that, in comparison with other state-of-the-art ship detection methods, our method is more efficient and achieves higher detection accuracy and more precise bounding boxes in different complex backgrounds.

Active photonic sensor communication cable for field application of optical data and power transmission

Science.gov (United States)

Suthau, Eike; Rieske, Ralf; Zerna, Thomas

2014-10-01

Omitting electrically conducting wires for sensor communication and power supply promises protection for sensor systems and monitored structures against lightning or high voltages, prevention of explosion hazards, and reduction of susceptibility to tampering. The ability to photonically power remote systems opens up the full range of electrical sensors. Power-over-fiber is an attractive option in electromagnetically sensitive environments, particularly for longterm, maintenance-free applications. It can deliver uninterrupted power sufficient for elaborate sensors, data processing or even actuators alongside continuous high speed data communication for remote sensor application. This paper proposes an active photonic sensor communication system, which combines the advantages of optical data links in terms of immunity to electromagnetic interference (EMI), high bandwidth, hardiness against tampering or eavesdropping, and low cable weight with the robustness one has come to expect from industrial or military electrical connectors. An application specific integrated circuit (ASIC) is presented that implements a closed-loop regulation of the sensor power supply to guarantee continuous, reliable data communications while maintaining a highly efficient, adaptive sensor supply scheme. It is demonstrated that the resulting novel photonic sensor communication cable can handle sensors and actuators differing orders of magnitude with respect to power consumption. The miniaturization of the electro-optical converters and driving electronics is as important to the presented development as the energy efficiency of the detached, optically powered sensor node. For this reason, a novel photonic packaging technology based on wafer-level assembly of the laser power converters by means of passive alignment will be disclosed in this paper.

Pulsed Laser Deposition: passive and active waveguides

Czech Academy of Sciences Publication Activity Database

Jelínek, Miroslav; Flory, F.; Escoubas, L.

2009-01-01

Roč. 34, č. 4 (2009), s. 438-449 ISSN 0268-1900 R&D Projects: GA ČR GA202/06/0216 Institutional research plan: CEZ:AV0Z10100522 Keywords : PLD * pulsed laser deposition * laser ablation * passive waveguides * active waveguides * waveguide laser * sensors * thin films * butane detection Subject RIV: BH - Optics, Masers, Lasers Impact factor: 0.384, year: 2009

1999 IEEE international geoscience and remote sensing symposium

Energy Technology Data Exchange (ETDEWEB)

NONE

1999-07-01

The theme of IGARSS'99, ``Remote Sensing of the System Earth--A Challenge for the 21st Century,'' shows how earth observation based on satellite remote sensing can significantly contribute to the future study of the environment and the changes it is undergoing, whether from natural causes or human activities. The wide range of topics offers an interdisciplinary approach and suggests integrated techniques and theory in remote sensing are essential for modeling and understanding the environment. Topics covered include: new instrumentation and future systems; high resolution SAR/InSAR; earth system science educational initiative; data fusion; radar sensing of ice sheets; image processing techniques; clouds and ice particles; internal waves; natural hazards and disaster monitoring; advanced passive and active sensors and sensor calibration; radar assessment of rain, oil spills and natural slicks; data standards and distribution; and vegetation monitoring using BRDF approaches.

Optimizing the next generation optical access networks

DEFF Research Database (Denmark)

Amaya Fernández, Ferney Orlando; Soto, Ana Cardenas; Tafur Monroy, Idelfonso

2009-01-01

Several issues in the design and optimization of the next generation optical access network (NG-OAN) are presented. The noise, the distortion and the fiber optic nonlinearities are considered to optimize the video distribution link in a passive optical network (PON). A discussion of the effect...

Single-scattering properties of ice particles in the microwave regime: Temperature effect on the ice refractive index with implications in remote sensing

International Nuclear Information System (INIS)

Ding, Jiachen; Bi, Lei; Yang, Ping; Kattawar, George W.; Weng, Fuzhong; Liu, Quanhua; Greenwald, Thomas

2017-01-01

An ice crystal single-scattering property database is developed in the microwave spectral region (1 to 874 GHz) to provide the scattering, absorption, and polarization properties of 12 ice crystal habits (10-plate aggregate, 5-plate aggregate, 8-column aggregate, solid hexagonal column, hollow hexagonal column, hexagonal plate, solid bullet rosette, hollow bullet rosette, droxtal, oblate spheroid, prolate spheroid, and sphere) with particle maximum dimensions from 2 µm to 10 mm. For each habit, four temperatures (160, 200, 230, and 270 K) are selected to account for temperature dependence of the ice refractive index. The microphysical and scattering properties include projected area, volume, extinction efficiency, single-scattering albedo, asymmetry factor, and six independent nonzero phase matrix elements (i.e. P_1_1, P_1_2, P_2_2, P_3_3, P_4_3 and P_4_4). The scattering properties are computed by the Invariant Imbedding T-Matrix (II-TM) method and the Improved Geometric Optics Method (IGOM). The computation results show that the temperature dependence of the ice single-scattering properties in the microwave region is significant, particularly at high frequencies. Potential active and passive remote sensing applications of the database are illustrated through radar reflectivity and radiative transfer calculations. For cloud radar applications, ignoring temperature dependence has little effect on ice water content measurements. For passive microwave remote sensing, ignoring temperature dependence may lead to brightness temperature biases up to 5 K in the case of a large ice water path. - Highlights: • Single-scattering properties of ice crystals are computed from 1 to 874 GHz. • Ice refractive index temperature dependence is considered at 160, 200, 230 and 270 K. • Potential applications of the database to microwave remote sensing are illustrated. • Ignoring temperature dependence of ice refractive index can lead to 5 K difference in IWP retrieval

Aerosol optical properties over the Svalbard region of Arctic: ground-based measurements and satellite remote sensing

Science.gov (United States)

Gogoi, Mukunda M.; Babu, S. Suresh

2016-05-01

In view of the increasing anthropogenic presence and influence of aerosols in the northern polar regions, long-term continuous measurements of aerosol optical parameters have been investigated over the Svalbard region of Norwegian Arctic (Ny-Ålesund, 79°N, 12°E, 8 m ASL). This study has shown a consistent enhancement in the aerosol scattering and absorption coefficients during spring. The relative dominance of absorbing aerosols is more near the surface (lower single scattering albedo), compared to that at the higher altitude. This is indicative of the presence of local anthropogenic activities. In addition, long-range transported biomass burning aerosols (inferred from the spectral variation of absorption coefficient) also contribute significantly to the higher aerosol absorption in the Arctic spring. Aerosol optical depth (AOD) estimates from ground based Microtop sun-photometer measurements reveals that the columnar abundance of aerosols reaches the peak during spring season. Comparison of AODs between ground based and satellite remote sensing indicates that deep blue algorithm of Moderate Resolution Imaging Spectroradiometer (MODIS) retrievals over Arctic snow surfaces overestimate the columnar AOD.

Sidewall passivation for InGaN/GaN nanopillar light emitting diodes

Energy Technology Data Exchange (ETDEWEB)

Choi, Won Hyuck; Abraham, Michael; Yu, Shih-Ying [Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); You, Guanjun; Liu, Jie; Wang, Li; Xu, Jian, E-mail: jianxu@engr.psu.edu [Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Mohney, Suzanne E., E-mail: mohney@ems.psu.edu [Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

2014-07-07

We studied the effect of sidewall passivation on InGaN/GaN multiquantum well-based nanopillar light emitting diode (LED) performance. In this research, the effects of varying etch rate, KOH treatment, and sulfur passivation were studied for reducing nanopillar sidewall damage and improving device efficiency. Nanopillars prepared under optimal etching conditions showed higher photoluminescence intensity compared with starting planar epilayers. Furthermore, nanopillar LEDs with and without sulfur passivation were compared through electrical and optical characterization. Suppressed leakage current under reverse bias and four times higher electroluminescence (EL) intensity were observed for passivated nanopillar LEDs compared with unpassivated nanopillar LEDs. The suppressed leakage current and EL intensity enhancement reflect the reduction of non-radiative recombination at the nanopillar sidewalls. In addition, the effect of sulfur passivation was found to be very stable, and further insight into its mechanism was gained through transmission electron microscopy.

An equivalent method of mixed dielectric constant in passive microwave/millimeter radiometric measurement

Science.gov (United States)

Su, Jinlong; Tian, Yan; Hu, Fei; Gui, Liangqi; Cheng, Yayun; Peng, Xiaohui

2017-10-01

Dielectric constant is an important role to describe the properties of matter. This paper proposes This paper proposes the concept of mixed dielectric constant(MDC) in passive microwave radiometric measurement. In addition, a MDC inversion method is come up, Ratio of Angle-Polarization Difference(RAPD) is utilized in this method. The MDC of several materials are investigated using RAPD. Brightness temperatures(TBs) which calculated by MDC and original dielectric constant are compared. Random errors are added to the simulation to test the robustness of the algorithm. Keywords: Passive detection, microwave/millimeter, radiometric measurement, ratio of angle-polarization difference (RAPD), mixed dielectric constant (MDC), brightness temperatures, remote sensing, target recognition.

Evaluation of AMSR-E derived soil moisture over Australia, /Remote Sensing of Environment

NARCIS (Netherlands)

Draper, C.S.; Walker, J.P.; Steinle, P.J.; De Jeu, R.A.M.; Holmes, T.R.H.

2009-01-01

This paper assesses remotely sensed near-surface soil moisture over Australia, derived from the passive microwave Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E) instrument. Soil moisture fields generated by the AMSR-E soil moisture retrieval algorithm developed at the Vrije

Optical remote sensing of the Gulf of Gabès – relation between turbidity, Secchi depth and total suspended matter

OpenAIRE

R. Katlane Essersi; B. Nechad; K. Ruddick; F. Zargouni

2010-01-01

Optical remote sensing is used here in the Gulf of Gabès to provide scientific information to support environmental management. The Gulf of Gabès is located in the southern east coast of Tunisia. It is a shallow continental shelf with semi-diurnal tides with average amplitude of 2 m. Industrial activities in this area since the early 1970s may have contributed to the degradation of the biodiversity of the ecosystem with eutrophica...

Application of Spectral Analysis Techniques in the Intercomparison of Aerosol Data: 1. an EOF Approach to the Spatial-Temporal Variability of Aerosol Optical Depth Using Multiple Remote Sensing Data Sets

Science.gov (United States)

Li, Jing; Carlson, Barbara E.; Lacis, Andrew A.

2013-01-01

Many remote sensing techniques and passive sensors have been developed to measure global aerosol properties. While instantaneous comparisons between pixel-level data often reveal quantitative differences, here we use Empirical Orthogonal Function (EOF) analysis, also known as Principal Component Analysis, to demonstrate that satellite-derived aerosol optical depth (AOD) data sets exhibit essentially the same spatial and temporal variability and are thus suitable for large-scale studies. Analysis results show that the first four EOF modes of AOD account for the bulk of the variance and agree well across the four data sets used in this study (i.e., Aqua MODIS, Terra MODIS, MISR, and SeaWiFS). Only SeaWiFS data over land have slightly different EOF patterns. Globally, the first two EOF modes show annual cycles and are mainly related to Sahara dust in the northern hemisphere and biomass burning in the southern hemisphere, respectively. After removing the mean seasonal cycle from the data, major aerosol sources, including biomass burning in South America and dust in West Africa, are revealed in the dominant modes due to the different interannual variability of aerosol emissions. The enhancement of biomass burning associated with El Niño over Indonesia and central South America is also captured with the EOF technique.

Optical fronthauling for 5G mobile: A perspective of passive metro WDM technology

DEFF Research Database (Denmark)

Zou, Shihuan Jim; Wagner, Christoph; Eiselt, Michael

2017-01-01

We discuss the necessity of passive WDM technology in the 5G fronthaul application. The proof-of-concept field trial showed that the proposed system integrated seamlessly with the current wireless equipment and had no impact on services.......We discuss the necessity of passive WDM technology in the 5G fronthaul application. The proof-of-concept field trial showed that the proposed system integrated seamlessly with the current wireless equipment and had no impact on services....

Extractive sampling and optical remote sensing of F100 aircraft engine emissions.

Science.gov (United States)

Cowen, Kenneth; Goodwin, Bradley; Joseph, Darrell; Tefend, Matthew; Satola, Jan; Kagann, Robert; Hashmonay, Ram; Spicer, Chester; Holdren, Michael; Mayfield, Howard

2009-05-01

The Strategic Environmental Research and Development Program (SERDP) has initiated several programs to develop and evaluate techniques to characterize emissions from military aircraft to meet increasingly stringent regulatory requirements. This paper describes the results of a recent field study using extractive and optical remote sensing (ORS) techniques to measure emissions from six F-15 fighter aircraft. Testing was performed between November 14 and 16, 2006 on the trim-pad facility at Tyndall Air Force Base in Panama City, FL. Measurements were made on eight different F100 engines, and the engines were tested on-wing of in-use aircraft. A total of 39 test runs were performed at engine power levels that ranged from idle to military power. The approach adopted for these tests involved extractive sampling with collocated ORS measurements at a distance of approximately 20-25 nozzle diameters downstream of the engine exit plane. The emission indices calculated for carbon dioxide, carbon monoxide, nitric oxide, and several volatile organic compounds showed very good agreement when comparing the extractive and ORS sampling methods.

Optical Energy Transfer and Conversion System

Science.gov (United States)

Hogan, Bartholomew P. (Inventor); Stone, William C. (Inventor)

2018-01-01

An optical energy transfer and conversion system comprising a fiber spooler and an electrical power extraction subsystem connected to the spooler with an optical waveguide. Optical energy is generated at and transferred from a base station through fiber wrapped around the spooler, and ultimately to the power extraction system at a remote mobility platform for conversion to another form of energy. The fiber spooler may reside on the remote mobility platform which may be a vehicle, or apparatus that is either self-propelled or is carried by a secondary mobility platform either on land, under the sea, in the air or in space.

Hybridization of active and passive elements for planar photonic components and interconnects

Science.gov (United States)

Pearson, M.; Bidnyk, S.; Balakrishnan, A.

2007-02-01

The deployment of Passive Optical Networks (PON) for Fiber-to-the-Home (FTTH) applications currently represents the fastest growing sector of the telecommunication industry. Traditionally, FTTH transceivers have been manufactured using commodity bulk optics subcomponents, such as thin film filters (TFFs), micro-optic collimating lenses, TO-packaged lasers, and photodetectors. Assembling these subcomponents into a single housing requires active alignment and labor-intensive techniques. Today, the majority of cost reducing strategies using bulk subcomponents has been implemented making future reductions in the price of manufacturing FTTH transceivers unlikely. Future success of large scale deployments of FTTH depends on further cost reductions of transceivers. Realizing the necessity of a radically new packaging approach for assembly of photonic components and interconnects, we designed a novel way of hybridizing active and passive elements into a planar lightwave circuit (PLC) platform. In our approach, all the filtering components were monolithically integrated into the chip using advancements in planar reflective gratings. Subsequently, active components were passively hybridized with the chip using fully-automated high-capacity flip-chip bonders. In this approach, the assembly of the transceiver package required no active alignment and was readily suitable for large-scale production. This paper describes the monolithic integration of filters and hybridization of active components in both silica-on-silicon and silicon-on-insulator PLCs.

Optical technologies applied alongside on-site and remote approaches for climate gas emission quantification at a wastewater treatment plant

DEFF Research Database (Denmark)

Samuelsson, Jerker; Delre, Antonio; Tumlin, Susanne

2018-01-01

Plant-integrated and on-site gas emissions were quantified from a Swedish wastewater treatment plant by applying several optical analytical techniques and measurement methods. Plant-integrated CH4 emission rates, measured using mobile ground-based remote sensing methods, varied between 28.5 and 33.......5 kg CH4 h−1, corresponding to an average emission factor of 5.9% as kg CH4 (kg CH4production) −1, whereas N2O emissions varied between 4.0 and 6.4 kg h−1, corresponding to an average emission factor of 1.5% as kg N2O-N (kg TN influent) −1. Plant-integrated NH3 emissions were around 0.4 kg h−1...... quantifications were approximately two-thirds of the plant-integrated emission quantifications, which may be explained by the different timeframes of the approaches and that not all emission sources were identified during on-site investigation. Off-site gas emission quantifications, using ground-based remote...

Fiber optic sensor system for entrance areas monitoring

Science.gov (United States)

Fajkus, Marcel; Nedoma, Jan; Kepak, Stanislav; Cubik, Jakub; Jargus, Jan; Zboril, Ondřej; Martinek, Radek; Vasinek, Vladimir

2017-10-01

Authors of this article present the fiber-optic system based on fiber Bragg gratings (FBGs) which are used to secure the entrance areas such as buildings, halls, warehouses, etc. The system uses the specially encapsulated sensory array of fiber Bragg gratings which are implemented into the floor or on the floor and allows for monitoring the area of 1 m2 up to 100 m2 depending on the number of FBG sensors. The sensory array is characterized by immunity to electromagnetic interference (EMI), passivity regarding electrical power supply, the possibility of remote evaluation (up to units of km) and high sensitivity. Proposed sensor system has detection capability greater than 99 % and furthermore, provides information about the weight load to an accuracy of +/- 5 kg. The concept has been tested in a real environment within the test polygon for several weeks. As the reference devices, we used the CCTV (Closed Circuit Television).

Monitoring of Gangotri glacier using remote sensing and ground ...

Indian Academy of Sciences (India)

Dozier J 1989a Remote sensing of snow in the visible and near-infrared wavelengths; In: Theory and Applications of. Optical Remote Sensing (ed.) Asrar G (New York: John. Wiley and Sons), pp. 527–547. Dozier J 1989b Spectral signature of alpine snow cover from the Landsat Thematic Mapper; Rem. Sens. Environ. 28.

Remote handling concept for the neutral beam system

International Nuclear Information System (INIS)

Choi, Chang-Hwan; Palmer, Jim; Conesa, Carles; Friconneau, Jean-Pierre; Martins, Jean-Pierre; Subramanian, Rajendran; Jeannoutot, Thomas; Graceffa, Joseph; Schunke, Beatrix; Uffelen, MarcoVan; Damiani, Carlo; Tesini, Alessandro

2011-01-01

The NB ITER Remote Maintenance System (NB IRMS) provides the means for the remote maintenance within the NB Cell by removal and replacement of the plant equipment. The NB IRMS will be installed and removed with the assistance of human workers during the preparation, and post-operation phase. During the maintenance operation after opening the Passive Magnetic Shield (PMS) and vessels, the maintenance activity and recovery from failure should be conducted remotely. This paper describes the concept design of the NB IRMS operating inside the NB cell for maintenance of the plant equipment such as NB components, and Upper Port Plugs (UPP). The main tasks of the IRMS, the description of the sub-systems and their specification, and deployment/operation principles are presented. The transportation concept of the NB IRMS to the hot cell facility for storage and maintenance is presented, which is to avoid unnecessary exposure on the equipment inside the NB cell during the machine operation.

Active and Passive Optical Imaging Modality for Unobtrusive Cardiorespiratory Monitoring and Facial Expression Assessment.

Science.gov (United States)

Blazek, Vladimir; Blanik, Nikolai; Blazek, Claudia R; Paul, Michael; Pereira, Carina; Koeny, Marcus; Venema, Boudewijn; Leonhardt, Steffen

2017-01-01

Because of their obvious advantages, active and passive optoelectronic sensor concepts are being investigated by biomedical research groups worldwide, particularly their camera-based variants. Such methods work noninvasively and contactless, and they provide spatially resolved parameter detection. We present 2 techniques: the active photoplethysmography imaging (PPGI) method for detecting dermal blood perfusion dynamics and the passive infrared thermography imaging (IRTI) method for detecting skin temperature distribution. PPGI is an enhancement of classical pulse oximetry. Approved algorithms from pulse oximetry for the detection of heart rate, heart rate variability, blood pressure-dependent pulse wave velocity, pulse waveform-related stress/pain indicators, respiration rate, respiratory variability, and vasomotional activity can easily be adapted to PPGI. Although the IRTI method primarily records temperature distribution of the observed object, information on respiration rate and respiratory variability can also be derived by analyzing temperature change over time, for example, in the nasal region, or through respiratory movement. Combined with current research areas and novel biomedical engineering applications (eg, telemedicine, tele-emergency, and telemedical diagnostics), PPGI and IRTI may offer new data for diagnostic purposes, including assessment of peripheral arterial and venous oxygen saturation (as well as their differences). Moreover, facial expressions and stress and/or pain-related variables can be derived, for example, during anesthesia, in the recovery room/intensive care unit and during daily activities. The main advantages of both monitoring methods are unobtrusive data acquisition and the possibility to assess vital variables for different body regions. These methods supplement each other to enable long-term monitoring of physiological effects and of effects with special local characteristics. They also offer diagnostic advantages for

Enhanced Visible Transmittance of Thermochromic VO2 Thin Films by SiO2 Passivation Layer and Their Optical Characterization

Directory of Open Access Journals (Sweden)

Jung-Hoon Yu

2016-07-01

Full Text Available This paper presents the preparation of high-quality vanadium dioxide (VO2 thermochromic thin films with enhanced visible transmittance (Tvis via radio frequency (RF sputtering and plasma enhanced chemical vapor deposition (PECVD. VO2 thin films with high Tvis and excellent optical switching efficiency (Eos were successfully prepared by employing SiO2 as a passivation layer. After SiO2 deposition, the roughness of the films was decreased 2-fold and a denser structure was formed. These morphological changes corresponded to the results of optical characterization including the haze, reflectance and absorption spectra. In spite of SiO2 coating, the phase transition temperature (Tc of the prepared films was not affected. Compared with pristine VO2, the total layer thickness after SiO2 coating was 160 nm, which is an increase of 80 nm. Despite the thickness change, the VO2 thin films showed a higher Tvis value (λ 650 nm, 58% compared with the pristine samples (λ 650 nm, 43%. This enhancement of Tvis while maintaining high Eos is meaningful for VO2-based smart window applications.

Remote handling recognition and display device

International Nuclear Information System (INIS)

Kimura, Motohiko.

1979-01-01

Purpose: To surely recognize the movements of remote handling equipments in a reactor by the use of a device in a simple structure. Constitution: A light emission surface and a light reception surface are provided, for example, putting therebetween a hook of a nob of a control rod as a remote control equipment. Depending on the position of the hook, there are two possible cases where the light can not arrive the light reception surface inhibited by the hook and where the light can be received not inhibited by the hook. By visually monitoring the presence or absence of the light reception from the outside of the reactor, the movement of the nob for the control rod can be recognized. Optical fibers connect the optical source with the light emission surface, and the light reception surface with the display surface. (Ikeda, J.)

Educational activities of remote sensing archaeology (Conference Presentation)

Science.gov (United States)

Hadjimitsis, Diofantos G.; Agapiou, Athos; Lysandrou, Vasilki; Themistocleous, Kyriacos; Cuca, Branka; Nisantzi, Argyro; Lasaponara, Rosa; Masini, Nicola; Krauss, Thomas; Cerra, Daniele; Gessner, Ursula; Schreier, Gunter

2016-10-01

Remote sensing science is increasingly being used to support archaeological and cultural heritage research in various ways. Satellite sensors either passive or active are currently used in a systematic basis to detect buried archaeological remains and to systematic monitor tangible heritage. In addition, airborne and low altitude systems are being used for documentation purposes. Ground surveys using remote sensing tools such as spectroradiometers and ground penetrating radars can detect variations of vegetation and soil respectively, which are linked to the presence of underground archaeological features. Education activities and training of remote sensing archaeology to young people is characterized of highly importance. Specific remote sensing tools relevant for archaeological research can be developed including web tools, small libraries, interactive learning games etc. These tools can be then combined and aligned with archaeology and cultural heritage. This can be achieved by presenting historical and pre-historical records, excavated sites or even artifacts under a "remote sensing" approach. Using such non-form educational approach, the students can be involved, ask, read, and seek to learn more about remote sensing and of course to learn about history. The paper aims to present a modern didactical concept and some examples of practical implementation of remote sensing archaeology in secondary schools in Cyprus. The idea was built upon an ongoing project (ATHENA) focused on the sue of remote sensing for archaeological research in Cyprus. Through H2020 ATHENA project, the Remote Sensing Science and Geo-Environment Research Laboratory at the Cyprus University of Technology (CUT), with the support of the National Research Council of Italy (CNR) and the German Aerospace Centre (DLR) aims to enhance its performance in all these new technologies.

DARLA: Data Assimilation and Remote Sensing for Littoral Applications

Science.gov (United States)

Jessup, A.; Holman, R. A.; Chickadel, C.; Elgar, S.; Farquharson, G.; Haller, M. C.; Kurapov, A. L.; Özkan-Haller, H. T.; Raubenheimer, B.; Thomson, J. M.

2012-12-01

DARLA is 5-year collaborative project that couples state-of-the-art remote sensing and in situ measurements with advanced data assimilation (DA) modeling to (a) evaluate and improve remote sensing retrieval algorithms for environmental parameters, (b) determine the extent to which remote sensing data can be used in place of in situ data in models, and (c) infer bathymetry for littoral environments by combining remotely-sensed parameters and data assimilation models. The project uses microwave, electro-optical, and infrared techniques to characterize the littoral ocean with a focus on wave and current parameters required for DA modeling. In conjunction with the RIVET (River and Inlets) Project, extensive in situ measurements provide ground truth for both the remote sensing retrieval algorithms and the DA modeling. Our goal is to use remote sensing to constrain data assimilation models of wave and circulation dynamics in a tidal inlet and surrounding beaches. We seek to improve environmental parameter estimation via remote sensing fusion, determine the success of using remote sensing data to drive DA models, and produce a dynamically consistent representation of the wave, circulation, and bathymetry fields in complex environments. The objectives are to test the following three hypotheses: 1. Environmental parameter estimation using remote sensing techniques can be significantly improved by fusion of multiple sensor products. 2. Data assimilation models can be adequately constrained (i.e., forced or guided) with environmental parameters derived from remote sensing measurements. 3. Bathymetry on open beaches, river mouths, and at tidal inlets can be inferred from a combination of remotely-sensed parameters and data assimilation models. Our approach is to conduct a series of field experiments combining remote sensing and in situ measurements to investigate signature physics and to gather data for developing and testing DA models. A preliminary experiment conducted at

Structure and photoluminescence of Mn-passivated nanocrystalline ZnO:S thin films

International Nuclear Information System (INIS)

Tong, Y.H.; Tang, Q.X.; Liu, Y.C.; Shao, C.L.; Xu, C.S.; Liu, Y.X.

2005-01-01

Mn-passivated nanocrystalline ZnO:S thin films were fabricated by thermally oxidizing Mn-doped ZnS (ZnS:Mn) films prepared by electron beam evaporation. Mn was introduced to passivate the surface defects of ZnO and to improve the optical properties. X-ray diffraction (XRD) and photoluminescence (PL) spectra at 81.9 K indicated the S content in ZnO thin film gradually decreased with increasing annealing temperature. The fitted result of the temperature-dependent PL spectra in the range from 81.9 to 302.2 K showed that S dopant could broaden the optical band gap energy of ZnO. Room temperature PL spectra confirmed that the ultraviolet peak shifted to lower energy with the decrease of S content in the thin film because of the Burstein-Moss effect

Precision remote sensor for oxygen and carbon dioxide, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — Mesa Photonics proposes development of a passive optical sensor for simultaneous high-precision measurement of oxygen and carbon dioxide profiles within the full...

A Comparative Study of Multiplexing Schemes for Next Generation Optical Access Networks

Science.gov (United States)

Imtiaz, Waqas A.; Khan, Yousaf; Shah, Pir Mehar Ali; Zeeshan, M.

2014-09-01

Passive optical network (PON) is a high bandwidth, economical solution which can provide the necessary bandwidth to end-users. Wavelength division multiplexed passive optical networks (WDM PONs) and time division multiplexed passive optical networks (TDM PONs) are considered as an evolutionary step for next-generation optical access (NGOA) networks. However they fail to provide highest transmission capacity, efficient bandwidth access, and robust dispersion tolerance. Thus future PONs are considered on simpler, efficient and potentially scalable, optical code division multiplexed (OCDM) PONs. This paper compares the performance of existing PONs with OCDM PON to determine a suitable scheme for NGOA networks. Two system parameter are used in this paper: fiber length, and bit rate. Performance analysis using Optisystem shows that; for a sufficient system performance parameters i.e. bit error rate (BER) ≤ 10-9, and maximum quality factor (Q) ≥ 6, OCDMA PON efficiently performs upto 50 km with 10 Gbit/s per ONU.

Sensitization of erbium in silicon-rich silica : the effect of annealing temperature and hydrogen passivation

International Nuclear Information System (INIS)

Wilkinson, A.R.; Forcales, M.; Elliman, R.G.

2005-01-01

This paper reports on the effect of annealing temperature and hydrogen passivation on the excitation cross-section and photoluminescence of erbium in silicon-rich silica. Samples were prepared by co-implantation of Si and Er into SiO 2 followed by a single thermal anneal at temperatures ranging from 800 to 1100 degrees C, and with or without hydrogen passivation performed at 500 degrees C. Using time-resolved photoluminescence, the effective erbium excitation cross-section is shown to increase by a factor 3, while the number of optically active erbium ions decreases by a factor of 4 with increasing annealing temperature. Hydrogen passivation is shown to increase the luminescence intensity and to shorten the luminescence lifetime at 1.54 μm only in the presence of Si nanocrystals. The implications fo these results for realizing a silicon-based optical amplifier are also discussed. (author). 19 refs., 3 figs

Global-scale assessment and combination of SMAP with ASCAT (Active) and AMSR2 (Passive) soil moisture products

Science.gov (United States)

Global-scale surface soil moisture (SSM) products retrieved from active and passive microwave remote sensing provide an effective method for monitoring near-real-time SSM content with nearly daily temporal resolution. In the present study, we first inter-compared global-scale error patterns and comb...

DSP-Based Focusing over Optical Fiber Using Time Reversal

DEFF Research Database (Denmark)

Piels, Molly; Porto da Silva, Edson; Estaran Tolosa, Jose Manuel

2014-01-01

A time-reversal array in multimode fiber is proposed for lossless switching using passive optical splitters. Numerical investigations are performed, and a two-transmitter array that routes a 3GBd QPSK signal through the physical layer is demonstrated experimentally.......A time-reversal array in multimode fiber is proposed for lossless switching using passive optical splitters. Numerical investigations are performed, and a two-transmitter array that routes a 3GBd QPSK signal through the physical layer is demonstrated experimentally....

Remote participation for LHD experiments

International Nuclear Information System (INIS)

Emoto, M.; Yamamoto, T.; Komada, S.; Nagayama, Y.

2006-01-01

To accomplish a large-scale experiment, such as large helical device (LHD) experiment, effective cooperation among institutes is necessary. In order to establish such cooperation, the NIFS provides the following remote participation facilities for the LHD experiments. (1) Remote access: The user can use a virtual private network (VPN) to connect to the LAN. This is the most flexible technique to participate in the experiments. The users who are not familiar with the experiments can log into the remote server running MetaFrame and Linux. In these computers, the required software is already installed. Therefore, the user need not be concerned with installing software. (2) Remote data reference: A mirror server exists to provide physical data to remote users. Moreover, the users can retrieve summarized data via a web server, which provides summarized information of each discharge experiment and graphs of the principal physical data. These graphs are useful for finding the required data quickly. (3) Remote communication and monitoring: For effective remote cooperation, communication between researchers is very important. For this purpose, a video conferencing system and a video streaming service are available. In addition to these facilities, the NIFS introduced Super SINET in 2002. This is an optical-fiber-based network. The backbone speed of this network is 10 Gbps, and the speed is 1 Gbps for direct connections

Remote participation for LHD experiments

Energy Technology Data Exchange (ETDEWEB)

Emoto, M. [National Institute for Fusion Science, National Institutes of Natural Sciences, 322-6 Oroshi, Toki 509-5292 (Japan)]. E-mail: emoto.masahiko@LHD.nifs.ac.jp; Yamamoto, T. [National Institute for Fusion Science, National Institutes of Natural Sciences, 322-6 Oroshi, Toki 509-5292 (Japan); Komada, S. [National Institute for Fusion Science, National Institutes of Natural Sciences, 322-6 Oroshi, Toki 509-5292 (Japan); Nagayama, Y. [National Institute for Fusion Science, National Institutes of Natural Sciences, 322-6 Oroshi, Toki 509-5292 (Japan)

2006-07-15

To accomplish a large-scale experiment, such as large helical device (LHD) experiment, effective cooperation among institutes is necessary. In order to establish such cooperation, the NIFS provides the following remote participation facilities for the LHD experiments. (1) Remote access: The user can use a virtual private network (VPN) to connect to the LAN. This is the most flexible technique to participate in the experiments. The users who are not familiar with the experiments can log into the remote server running MetaFrame and Linux. In these computers, the required software is already installed. Therefore, the user need not be concerned with installing software. (2) Remote data reference: A mirror server exists to provide physical data to remote users. Moreover, the users can retrieve summarized data via a web server, which provides summarized information of each discharge experiment and graphs of the principal physical data. These graphs are useful for finding the required data quickly. (3) Remote communication and monitoring: For effective remote cooperation, communication between researchers is very important. For this purpose, a video conferencing system and a video streaming service are available. In addition to these facilities, the NIFS introduced Super SINET in 2002. This is an optical-fiber-based network. The backbone speed of this network is 10 Gbps, and the speed is 1 Gbps for direct connections.

Highly Reliable PON Optical Splitters for Optical Access Networks in Outside Environments

Science.gov (United States)

Watanabe, Hiroshi; Araki, Noriyuki; Fujimoto, Hisashi

Broadband optical access services are spreading throughout the world, and the number of fiber to the home (FTTH) subscribers is increasing rapidly. Telecom operators are constructing passive optical networks (PONs) to provide optical access services. Externally installed optical splitters for PONs are very important passive devices in optical access networks, and they must provide satisfactory performance as outdoor plant over long periods. Therefore, we calculate the failure rate of optical access networks and assign a failure rate to the optical splitters in optical access networks. The maximum cumulative failure rate of 1 × 8 optical splitters was calculated as 0.025 for an optical access fiber length of 2.1km and a 20-year operating lifetime. We examined planar lightwave circuit (PLC) type optical splitters for use as outside plant in terms of their optical characteristics and environmental reliability. We confirmed that PLC type optical splitters have sufficient optical performance for a PON splitter and sufficient reliability as outside plant in accordance with ITU-T standard values. We estimated the lifetimes of three kinds of PLC type optical splitters by using accelerated aging tests. The estimated failure rate of these splitters installed in optical access networks was below the target value for the cumulative failure rate, and we confirmed that they have sufficient reliability to maintain the quality of the network service. We developed 1 × 8 optical splitter modules with plug and socket type optical connectors and optical fiber cords for optical aerial closures designed for use as outside plant. These technologies make it easy to install optical splitters in an aerial optical closure. The optical splitter modules have sufficient optical performance levels for PONs because the insertion loss at the commercially used wavelengths of 1.31 and 1.55µm is less than the criterion established by ITU-T Recommendation G.671 for optical splitters. We performed a

Robust passive control for Internet-based switching systems with time-delay

Energy Technology Data Exchange (ETDEWEB)

Guan Zhihong [Department of Control Science and Engineering, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); Zhang Hao [Department of Control Science and Engineering, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China)], E-mail: ehao79@163.com; Yang Shuanghua [Department of Computer Science, Loughborough University, Loughborough LE11 3TU (United Kingdom)

2008-04-15

In this paper, based on remote control and local control strategy, a class of hybrid multi-rate control models with time-delay and switching controllers are formulated and the problem of robust passive control for this discrete system is investigated. By Lyapunov-Krasovskii function and applying it to a descriptor model transformation some new sufficient conditions in form of LMIs are derived. A numerical example is given to illustrate the effectiveness of the theoretical result.

Remote measurement of river discharge using thermal particle image velocimetry (PIV) and various sources of bathymetric information

Science.gov (United States)

Legleiter, Carl; Kinzel, Paul J.; Nelson, Jonathan M.

2017-01-01

Although river discharge is a fundamental hydrologic quantity, conventional methods of streamgaging are impractical, expensive, and potentially dangerous in remote locations. This study evaluated the potential for measuring discharge via various forms of remote sensing, primarily thermal imaging of flow velocities but also spectrally-based depth retrieval from passive optical image data. We acquired thermal image time series from bridges spanning five streams in Alaska and observed strong agreement between velocities measured in situ and those inferred by Particle Image Velocimetry (PIV), which quantified advection of thermal features by the flow. The resulting surface velocities were converted to depth-averaged velocities by applying site-specific, calibrated velocity indices. Field spectra from three clear-flowing streams provided strong relationships between depth and reflectance, suggesting that, under favorable conditions, spectrally-based bathymetric mapping could complement thermal PIV in a hybrid approach to remote sensing of river discharge; this strategy would not be applicable to larger, more turbid rivers, however. A more flexible and efficient alternative might involve inferring depth from thermal data based on relationships between depth and integral length scales of turbulent fluctuations in temperature, captured as variations in image brightness. We observed moderately strong correlations for a site-aggregated data set that reduced station-to-station variability but encompassed a broad range of depths. Discharges calculated using thermal PIV-derived velocities were within 15% of in situ measurements when combined with depths measured directly in the field or estimated from field spectra and within 40% when the depth information also was derived from thermal images. The results of this initial, proof-of-concept investigation suggest that remote sensing techniques could facilitate measurement of river discharge.

Spatiotemporal dynamics of snow cover based on multi-source remote sensing data in China

Science.gov (United States)

Huang, Xiaodong; Deng, Jie; Ma, Xiaofang; Wang, Yunlong; Feng, Qisheng; Hao, Xiaohua; Liang, Tiangang

2016-10-01

By combining optical remote sensing snow cover products with passive microwave remote sensing snow depth (SD) data, we produced a MODIS (Moderate Resolution Imaging Spectroradiometer) cloudless binary snow cover product and a 500 m snow depth product. The temporal and spatial variations of snow cover from December 2000 to November 2014 in China were analyzed. The results indicate that, over the past 14 years, (1) the mean snow-covered area (SCA) in China was 11.3 % annually and 27 % in the winter season, with the mean SCA decreasing in summer and winter seasons, increasing in spring and fall seasons, and not much change annually; (2) the snow-covered days (SCDs) showed an increase in winter, spring, and fall, and annually, whereas they showed a decrease in summer; (3) the average SD decreased in winter, summer, and fall, while it increased in spring and annually; (4) the spatial distributions of SD and SCD were highly correlated seasonally and annually; and (5) the regional differences in the variation of snow cover in China were significant. Overall, the SCD and SD increased significantly in south and northeast China, and decreased significantly in the north of Xinjiang province. The SCD and SD increased on the southwest edge and in the southeast part of the Tibetan Plateau, whereas it decreased in the north and northwest regions.

Exploring luminescence-based temperature sensing using protein-passivated gold nanoclusters

Science.gov (United States)

Chen, Xi; Essner, Jeremy B.; Baker, Gary A.

2014-07-01

We explore the analytical performance and limitations of optically monitoring aqueous-phase temperature using protein-protected gold nanoclusters (AuNCs). Although not reported elsewhere, we find that these bio-passivated AuNCs show pronounced hysteresis upon thermal cycling. This unwanted behaviour can be eliminated by several strategies, including sol-gel coating and thermal denaturation of the biomolecular template, introducing protein-templated AuNC probes as viable nanothermometers.We explore the analytical performance and limitations of optically monitoring aqueous-phase temperature using protein-protected gold nanoclusters (AuNCs). Although not reported elsewhere, we find that these bio-passivated AuNCs show pronounced hysteresis upon thermal cycling. This unwanted behaviour can be eliminated by several strategies, including sol-gel coating and thermal denaturation of the biomolecular template, introducing protein-templated AuNC probes as viable nanothermometers. Electronic supplementary information (ESI) available: Supplemental figures and experimental details. See DOI: 10.1039/c4nr02069c

Predicting Intra-Urban Population Densities in Africa using SAR and Optical Remote Sensing Data

Science.gov (United States)

Linard, C.; Steele, J.; Forget, Y.; Lopez, J.; Shimoni, M.

2017-12-01

The population of Africa is predicted to double over the next 40 years, driving profound social, environmental and epidemiological changes within rapidly growing cities. Estimations of within-city variations in population density must be improved in order to take urban heterogeneities into account and better help urban research and decision making, especially for vulnerability and health assessments. Satellite remote sensing offers an effective solution for mapping settlements and monitoring urbanization at different spatial and temporal scales. In Africa, the urban landscape is covered by slums and small houses, where the heterogeneity is high and where the man-made materials are natural. Innovative methods that combine optical and SAR data are therefore necessary for improving settlement mapping and population density predictions. An automatic method was developed to estimate built-up densities using recent and archived optical and SAR data and a multi-temporal database of built-up densities was produced for 48 African cities. Geo-statistical methods were then used to study the relationships between census-derived population densities and satellite-derived built-up attributes. Best predictors were combined in a Random Forest framework in order to predict intra-urban variations in population density in any large African city. Models show significant improvement of our spatial understanding of urbanization and urban population distribution in Africa in comparison to the state of the art.

Remote RemoteRemoteRemote sensing potential for sensing ...

African Journals Online (AJOL)

Remote RemoteRemoteRemote sensing potential for sensing potential for sensing potential for sensing potential for sensing potential for sensing potential for sensing potential for sensing potential for sensing potential for sensing potential for sensing p. A Ngie, F Ahmed, K Abutaleb ...

Error Characterisation and Merging of Active and Passive Microwave Soil Moisture Data Sets

Science.gov (United States)

Wagner, Wolfgang; Gruber, Alexander; de Jeu, Richard; Parinussa, Robert; Chung, Daniel; Dorigo, Wouter; Reimer, Christoph; Kidd, Richard

2015-04-01

As part of the Climate Change Initiative (CCI) programme of the European Space Agency (ESA) a data fusion system has been developed which is capable of ingesting surface soil moisture data derived from active and passive microwave sensors (ASCAT, AMSR-E, etc.) flown on different satellite platforms and merging them to create long and consistent time series of soil moisture suitable for use in climate change studies. The so-created soil moisture data records (latest version: ESA CCI SM v02.1 released on 5/12/2014) are freely available and can be obtained from http://www.esa-soilmoisture-cci.org/. As described by Wagner et al. (2012) the principle steps of the data fusion process are: 1) error characterisation, 2) matching to account for data set specific biases, and 3) merging. In this presentation we present the current data fusion process and discuss how new error characterisation methods, such as the increasingly popular triple collocation method as discussed for example by Zwieback et al. (2012) may be used to improve it. The main benefit of an improved error characterisation would be a more reliable identification of the best performing microwave soil moisture retrieval(s) for each grid point and each point in time. In case that two or more satellite data sets provides useful information, the estimated errors can be used to define the weights with which each satellite data set are merged, i.e. the lower its error the higher its weight. This is expected to bring a significant improvement over the current data fusion scheme which is not yet based on quantitative estimates of the retrieval errors but on a proxy measure, namely the vegetation optical depth (Dorigo et al., 2015): over areas with low vegetation passive soil moisture retrievals are used, while over areas with moderate vegetation density active retrievals are used. In transition areas, where both products correlate well, both products are being used in a synergistic way: on time steps where only one of

Morphology, chemical composition , and electrochemical characteristics of colored titanium passive layers

International Nuclear Information System (INIS)

Jerkiewicz, G.; Hrapovic, S.; Vatankhah, G.; Luan, B.L.

1999-01-01

Brightly and uniformly colored passive layers on Ti are formed by application of AC polarization in aqueous NH 4 BF 4 . A wide spectrum of well-defined colors is accomplished by varying the AC voltage. The passive films are stable in the ambient and in aqueous chloride, perchlorate, sulfate solutions. Optical microscopy and SEM analyses indicate that the passive layers are compact and do not reveal fractures or cracks. XPS characterization of the colored passive layers reveals that their surface-chemical composition depends on the AC polarization voltage. The main constituents of the passive layers are Ti z+ , O 2- , and F - (z varies from 4 to 2 depending on the depth). Fluoride in the film originates form decomposition of NH 4 BF 4 and it accumulates at the inner metal/passive-film interface. XPS depth profiling shows that the higher the AC voltage applied, the thicker the passive film formed. Electrochemical properties of the colored Ti passive layers are determined by recording polarization curves in the -0.8 - 3.2 V, RHE, range and Tafel plots in the hydrogen evolution reaction (HER) region in 1.0 M aqueous H 2 SO 4 solution. The polarization curves show that the corrosion potential of the colored passive layers shifts towards less-negative potential indicating that they are more stable than Ti under the same conditions. The Tafel plots for the HER demonstrate that the passive layers have much higher activity than Ti towards the HER. The Tafel relations reveal new features that can be associated with the partial breakdown/decomposition of the passive layers and with H absorption. (author)

An ultra-long cavity passively mode-locked fiber laser based on nonlinear polarization rotation in a semiconductor optical amplifier

International Nuclear Information System (INIS)