WorldWideScience

Sample records for optical feedback signal

  1. Reconfigurable Optical Signal Processing Based on a Distributed Feedback Semiconductor Optical Amplifier.

    Science.gov (United States)

    Li, Ming; Deng, Ye; Tang, Jian; Sun, Shuqian; Yao, Jianping; Azaña, José; Zhu, Ninghua

    2016-01-27

    All-optical signal processing has been considered a solution to overcome the bandwidth and speed limitations imposed by conventional electronic-based systems. Over the last few years, an impressive range of all-optical signal processors have been proposed, but few of them come with reconfigurability, a feature highly needed for practical signal processing applications. Here we propose and experimentally demonstrate an analog optical signal processor based on a phase-shifted distributed feedback semiconductor optical amplifier (DFB-SOA) and an optical filter. The proposed analog optical signal processor can be reconfigured to perform signal processing functions including ordinary differential equation solving and temporal intensity differentiation. The reconfigurability is achieved by controlling the injection currents. Our demonstration provitdes a simple and effective solution for all-optical signal processing and computing.

  2. Reconfigurable Optical Signal Processing Based on a Distributed Feedback Semiconductor Optical Amplifier

    Science.gov (United States)

    Li, Ming; Deng, Ye; Tang, Jian; Sun, Shuqian; Yao, Jianping; Azaña, José; Zhu, Ninghua

    2016-01-01

    All-optical signal processing has been considered a solution to overcome the bandwidth and speed limitations imposed by conventional electronic-based systems. Over the last few years, an impressive range of all-optical signal processors have been proposed, but few of them come with reconfigurability, a feature highly needed for practical signal processing applications. Here we propose and experimentally demonstrate an analog optical signal processor based on a phase-shifted distributed feedback semiconductor optical amplifier (DFB-SOA) and an optical filter. The proposed analog optical signal processor can be reconfigured to perform signal processing functions including ordinary differential equation solving and temporal intensity differentiation. The reconfigurability is achieved by controlling the injection currents. Our demonstration provitdes a simple and effective solution for all-optical signal processing and computing.

  3. Real-time optical signal processors employing optical feedback: amplitude and phase control.

    Science.gov (United States)

    Gallagher, N C

    1976-04-01

    The development of real-time coherent optical signal processors has increased the appeal of optical computing techniques in signal processing applications. A major limitation of these real-time systems is the. fact that the optical processing material is generally of a phase-only type. The result is that the spatial filters synthesized with these systems must be either phase-only filters or amplitude-only filters. The main concern of this paper is the application of optical feedback techniques to obtain simultaneous and independent amplitude and phase control of the light passing through the system. It is shown that optical feedback techniques may be employed with phase-only spatial filters to obtain this amplitude and phase control. The feedback system with phase-only filters is compared with other feedback systems that employ combinations of phase-only and amplitude-only filters; it is found that the phase-only system is substantially more flexible than the other two systems investigated.

  4. Optical feedback signal for ultrashort laser pulse ablation of tissue

    Energy Technology Data Exchange (ETDEWEB)

    Kim, B.-M.; Feit, M.D.; Rubenchik, A.M.; Mammini, B.M.; Da Silva, L.B.

    1997-07-01

    An optical feedback system for controlled precise tissue ablation is discussed. Our setup includes an ultrashort pulse laser (USPL), and a diagnostic system using analysis of either tissue fluorescence or plasma emission luminescence. Current research is focused on discriminating hard and soft tissues such as bone and spinal cord during surgery using either technique. Our experimental observations exhibit considerable spectroscopic contrast between hard and soft tissue, and both techniques offer promise for a practical diagnostic system.

  5. Compact optical displacement sensing by detection of microwave signals generated from a monolithic passively mode-locked laser under feedback

    Science.gov (United States)

    Simos, Christos; Simos, Hercules; Nikas, Thomas; Syvridis, Dimitris

    2015-05-01

    A monolithic passively mode-locked laser is proposed as a compact optical sensor for displacements and vibrations of a reflecting object. The sensing principle relies on the change of the laser repetition frequency that is induced by optical feedback from the object under measurement. It has been previously observed that, when a semiconductor passively mode locked laser receives a sufficient level of optical feedback from an external reflecting surface it exhibits a repetition frequency that is no more determined by the mode-locking rule of the free-running operation but is imposed by the length of the external cavity. Therefore measurement of the resulting laser repetition frequency under self-injection permits the accurate and straightforward determination of the relative position of the reflecting object. The system has an inherent wireless capability since the repetition rate of the laser can be wirelessly detected by means of a simple antenna which captures the microwave signal generated by the saturable absorber and is emitted through the wiring of the laser. The sensor setup is very simple as it requires few optical components besides the laser itself. Furthermore, the deduction of the relative position of the reflecting object is straightforward and does not require any processing of the detected signal. The proposed sensor has a theoretical sub-wavelength resolution and its performance depends on the RF linewidth of the laser and the resolution of the repetition frequency measurement. Other physical parameters that induce phase changes of the external cavity could also be quantified.

  6. Optical generation of microwave signals with a dual-phase-shifted Al2O3:Yb3+ distributed-feedback laser

    NARCIS (Netherlands)

    Bernhardi, E.H.; Khan, M.R.H.; Roeloffzen, C.G.H.; Wolferen, van H.A.G.M.; Wörhoff, K.; Ridder, de R.M.; Pollnau, M.

    2012-01-01

    We demonstrate the optical generation of stable microwave signals from a dual-wavelength distributed-feedback waveguide laser in ytterbium-doped alumina. The microwave beat signal was produced at ~15 GHz with a frequency stability of ±2.5 MHz.

  7. Signature analysis of microwave signal generator with a fiber optic delay line in a feedback loop

    Science.gov (United States)

    Biryukov, Vladimir V.; Grachev, Vladimir A.; Kapustin, Sergey A.; Lukoyanova, Tatyana S.; Lobin, Sergey G.; Raevskii, Alexey S.

    2016-03-01

    The authors deal with advantages and disadvantages of optoelectronic microwave generators in comparison with "traditional" solid-state microwave signal generators. The article contains the experimental results of spectral characteristics of a single-stage optoelectronic microwave signal generator (frequency range from 15 up to 22 GHz).

  8. Acousto-optic laser optical feedback imaging

    CERN Document Server

    Jacquin, Olivier; Lacot, Eric; Hugon, Olivier; De Chatellus, Hugues Guillet; François, Ramaz

    2012-01-01

    We present a photon noise and diffraction limited imaging method combining the imaging laser and ultrasonic waves. The laser optical feedback imaging (LOFI) technique is an ultrasensitive imaging method for imaging objects through or embedded within a scattering medium. However, LOFI performances are dramatically limited by parasitic optical feedback occurring in the experimental setup. In this work, we have tagged the ballistic photons by an acousto-optic effect in order to filter the parasitic feedback effect and to reach the theoretical and ultimate sensitivity of the LOFI technique. We present the principle and the experimental setup of the acousto-optic laser optical feedback imaging (AO-LOFI) technique, and we demonstrate the suppression of the parasitic feedback.

  9. Optical feedback structures and methods of making

    Science.gov (United States)

    Snee, Preston T; Chan, Yin Thai; Nocera, Daniel G; Bawendi, Moungi G

    2014-11-18

    An optical resonator can include an optical feedback structure disposed on a substrate, and a composite including a matrix including a chromophore. The composite disposed on the substrate and in optical communication with the optical feedback structure. The chromophore can be a semiconductor nanocrystal. The resonator can provide laser emission when excited.

  10. Acousto-optic collinear filter with optoelectronic feedback

    Science.gov (United States)

    Mantsevich, S. N.; Balakshy, V. I.; Kuznetsov, Yu. I.

    2017-04-01

    A spectral optoelectronic system combining a collinear acousto-optic cell fabricated of calcium molybdate single crystal and a positive electronic feedback is proposed first and examined theoretically and experimentally. The feedback signal is formed at the cell output due to the optical heterodyning effect with the use of an unconventional regime of cell operation. It is shown that the feedback enables controlling spectral characteristics of the acousto-optic cell, resulting in enhancing the spectral resolution and the accuracy of optical wavelength determination. In the experiment, maximal filter passband narrowing was as great as 37 times.

  11. Searching for Prototypical Facial Feedback Signals

    NARCIS (Netherlands)

    Heylen, Dirk K.J.; Bevacqua, E.; Tellier, M.; Pelachaud, C.; Pelachaud, C.; Martin, J-C.; André, E.; Chollet, G.; Pelé, D.

    2007-01-01

    Embodied conversational agents should be able to provide feedback on what a human interlocutor is saying. We are compiling a list of facial feedback expressions that signal attention and interest, grounding and attitude. As expressions need to serve many functions at the same time and most of the

  12. All-Optical WDM Buffer System Realized by NOLM and Feedback Loop Structure

    Institute of Scientific and Technical Information of China (English)

    Seungwoo Yi; Kyeong-Mo Yoon; Yong-Gi Lee; Jinseob Eom

    2003-01-01

    We propose an all-optical WDM buffer for optical packet switching system, which consists of NOLM and feedback loop. The proposed structure provides more than 40 turn buffering and nice output of buffered data when selected by control signal.

  13. Plenoptic microscope based on laser optical feedback imaging (LOFI)

    CERN Document Server

    Glastre, W; Jacquin, O; de Chatellus, H Guillet; Lacot, E

    2015-01-01

    We present an overview of the performances of a plenoptic microscope which combines the high sensitivity of a laser optical feedback imaging setup , the high resolution of optical synthetic aperture and a shot noise limited signal to noise ratio by using acoustic photon tagging. By using an adapted phase filtering, this microscope allows phase drift correction and numerical aberration compensation (defocusing, coma, astigmatism ...). This new kind of microscope seems to be well adapted to make deep imaging through scattering and heterogeneous media.

  14. OLED lightings with optical feedback for luminance difference compensation

    Science.gov (United States)

    Shin, D. K.; Park, J. W.

    2013-12-01

    We have employed an optical feedback circuit in an organic light-emitting diode (OLED) lighting system to ensure uniform light output across large-area OLED lighting tiles. In a lighting system with several large-area OLED lighting tiles involved, the panel aging (luminance decrease) may appear differently in each, resulting in a falling-off in lighting quality. To tackle this, light output from each OLED tile is monitored by the optical feedback circuit that consists of a photodetector, I-V converter, 10-bit analogue-digital converter (ADC), and comparator. A photodetector mounted on a glass side generates a feedback signal (current) by detecting side-emitting OLED light. To monitor bottom-emitting output light by detecting side-emitting OLED light, a mapping table between the ADC value and the luminance of bottom emission has been established. If the ADC value is lower or higher than the reference one corresponding to the target luminance of OLED tiles, a micro controller unit adjusts the pulse width modulation used for the control of the power supplied to OLED tiles in such a way that the ADC value obtained from optical feedback is the same as the reference one. As a result, the target luminance of each individual OLED tile is kept unchanged. With the optical feedback circuit included in the lighting system, we have observed less than 2% difference in relative intensity of neighboring OLED tiles.

  15. Influence of Feedback Levels on Polarized Optical Feedback Characteristics in Zeeman-Birefringence Dual Frequency Lasers

    Institute of Scientific and Technical Information of China (English)

    MAO Wei; ZHANG Shu-Lian; ZHOU Lu-Fei; LIU Xiao-Yan; WANG Ming-Ming

    2007-01-01

    The influence of Feedback levels on the intensity and polarization properties of polarized optical feedback in a Zeeman-birefringence dual frequency laser is systematically investigated. By changing the feedback power ratio, different feedback levels are obtained. Three distinct regimes of polarized optical feedback effects are found and defined as regimes Ⅰ, Ⅱand Ⅲ. The feedback level boundaries among the regimes are acquired experimentally. The theoretical analysis is presented to be in good agreement with the experimental results.

  16. Optical Feedback Control and Electrical-Optical Costimulation of Peripheral Nerves.

    Science.gov (United States)

    Kapur, Sahil K; Richner, Thomas J; Brodnick, Sarah K; Williams, Justin C; Poore, Samuel O

    2016-09-01

    Optogenetics is an emerging technology that enables the expression of light-activated ion channels in mammalian cells. Neurons expressing light-activated ion channels can be depolarized using the appropriate wavelength of light. Optical stimulation of neurons could have important implications for further understanding and managing peripheral nerve deficits leading to paresis or paralysis. This study examines the utility of this technology in a feedback-controlled system and the advantages of coupling this technology with conventional electrical stimulation. The sciatic nerves of transgenic mice expressing blue light-activated ion channels (channelrhodopsin-2) were optically manipulated to generate electromyographic responses in the gastrocnemius muscle and to develop two potential applications of this technology: feedback-controlled optical stimulation using a proportional-integral controller, and simultaneous electrical-optical stimulation. The authors observed repeatable and predictable behavior of the optical controller in over 200 trials and a statistically significant decreased error when using optical feedback control as opposed to non-feedback controlled stimulation (n = 6 limbs). A second application of this technology was the amplification of electrically generated peripheral nerve signals using an optical source. Amplification of electrical activity was observed even when subthreshold electrical stimulation was used. Optical feedback control and optical amplification of subthreshold activity extend the versatility of optogenetics in peripheral nerve applications. Optical feedback control is a new application of an approach originally developed for functional electrical stimulation. Optical amplification of subthreshold electrical stimulation motivates future investigations into the optical amplification of endogenous subthreshold peripheral nerve activity (e.g., following spinal cord injury).

  17. Optical feedback-induced light modulation for fiber-based laser ablation.

    Science.gov (United States)

    Kang, Hyun Wook

    2014-11-01

    Optical fibers have been used as a minimally invasive tool in various medical fields. However, due to excessive heat accumulation, the distal end of a fiber often suffers from severe melting or devitrification, leading to the eventual fiber failure during laser treatment. In order to minimize thermal damage at the fiber tip, an optical feedback sensor was developed and tested ex vivo. Porcine kidney tissue was used to evaluate the feasibility of optical feedback in terms of signal activation, ablation performance, and light transmission. Testing various signal thresholds demonstrated that 3 V was relatively appropriate to trigger the feedback sensor and to prevent the fiber deterioration during kidney tissue ablation. Based upon the development of temporal signal signatures, full contact mode rapidly activated the optical feedback sensor possibly due to heat accumulation. Modulated light delivery induced by optical feedback diminished ablation efficiency by 30% in comparison with no feedback case. However, long-term transmission results validated that laser ablation assisted with optical feedback was able to almost consistently sustain light delivery to the tissue as well as ablation efficiency. Therefore, an optical feedback sensor can be a feasible tool to protect optical fiber tips by minimizing debris contamination and delaying thermal damage process and to ensure more efficient and safer laser-induced tissue ablation.

  18. All-optical noninvasive delayed feedback control of semiconductor lasers

    CERN Document Server

    Schikora, Sylvia

    2013-01-01

    The stabilization of unstable states hidden in the dynamics of a system, in particular the control of chaos, has received much attention in the last years. Sylvia Schikora for the first time applies a well-known control method called delayed feedback control entirely in the all-optical domain. A multisection semiconductor laser receives optical feedback from an external Fabry-Perot interferometer. The control signal is a phase-tunable superposition of the laser signal and provokes the laser to operate in an otherwise unstable periodic state with a period equal to the time delay. The control is noninvasive, because the reflected signal tends to zero when the target state is reached.   The work has been awarded the Carl-Ramsauer-Prize 2012.   Contents ·         All-Optical Control Setup ·         Stable States with Resonant Fabry-Perot Feedback ·         Control of an Unstable Stationary State and of Unstable Selfpulsations ·         Controlling Chaos ·         Con...

  19. Bandwidth enhancement and time-delay signature suppression of chaotic signal from an optical feedback semiconductor laser by using cross phase modulation in a highly nonlinear fiber loop mirror

    Science.gov (United States)

    Wang, Liang-Yan; Zhong, Zhu-Qiong; Wu, Zheng-Mao; Lu, Dong; Chen, Xi; Chen, Jun; Xia, Guang-Qiong

    2016-11-01

    Based on a nonlinear fiber loop mirror (NOLM) composed of a fiber coupler (FC) and a highly nonlinear fiber (HNLF), a scheme is proposed to simultaneously realize the bandwidth enhancement and the time-delay signature (TDS) suppression of a chaotic signal generated from an external cavity optical feedback semiconductor laser. The simulation results show that, after passing through the NOLM, the bandwidth of chaotic signal can be efficiently enhanced and the TDS can be well suppressed under suitable operation parameters. Furthermore, the influences of the power-splitting ratio of the FC, the averaged power of the chaotic signal entering into the FC and the length of the HNLF on the chaotic bandwidth and TDS are analyzed, and the optimized parameters are determined.

  20. Stereoscopic Optical Signal Processor

    Science.gov (United States)

    Graig, Glenn D.

    1988-01-01

    Optical signal processor produces two-dimensional cross correlation of images from steroscopic video camera in real time. Cross correlation used to identify object, determines distance, or measures movement. Left and right cameras modulate beams from light source for correlation in video detector. Switch in position 1 produces information about range of object viewed by cameras. Position 2 gives information about movement. Position 3 helps to identify object.

  1. Semiconductor laser with filtered optical feedback: bridge between conventional feedback and optical injection.

    NARCIS (Netherlands)

    Hek, G.M.; Rottschäfer, V.

    2005-01-01

    We study a model for a semiconductor laser subject to filtered optical feedback, i.e. a system of delay differential equations (DDEs). In this model, the filter is characterized by a mean frequency Omega(m) and a filter width A. In the limit of a narrow filter (lambda -> 0), the laser equations redu

  2. Semiconductor laser with filtered optical feedback: from optical injection to conventional feedback.

    NARCIS (Netherlands)

    Hek, G.M.; Rottschäfer, V.

    2007-01-01

    Abstract We study a model for a semiconductor laser subject to filtered optical feedback, that is a system of delay differential equations (DDEs). In this model the filter is characterised by a mean frequency Ωm and a filter width λ. In the limit of a narrow filter (λ → 0) the laser equations reduce

  3. Semiconductor laser with filtered optical feedback: bridge between conventional feedback and optical injection.

    NARCIS (Netherlands)

    Hek, G.M.; Rottschäfer, V.

    2005-01-01

    We study a model for a semiconductor laser subject to filtered optical feedback, i.e. a system of delay differential equations (DDEs). In this model, the filter is characterized by a mean frequency Omega(m) and a filter width A. In the limit of a narrow filter (lambda -> 0), the laser equations

  4. Relaxation oscillations and hierarchy of feedbacks in MAPK signaling

    Science.gov (United States)

    Kochańczyk, Marek; Kocieniewski, Paweł; Kozłowska, Emilia; Jaruszewicz-Błońska, Joanna; Sparta, Breanne; Pargett, Michael; Albeck, John G.; Hlavacek, William S.; Lipniacki, Tomasz

    2017-01-01

    We formulated a computational model for a MAPK signaling cascade downstream of the EGF receptor to investigate how interlinked positive and negative feedback loops process EGF signals into ERK pulses of constant amplitude but dose-dependent duration and frequency. A positive feedback loop involving RAS and SOS, which leads to bistability and allows for switch-like responses to inputs, is nested within a negative feedback loop that encompasses RAS and RAF, MEK, and ERK that inhibits SOS via phosphorylation. This negative feedback, operating on a longer time scale, changes switch-like behavior into oscillations having a period of 1 hour or longer. Two auxiliary negative feedback loops, from ERK to MEK and RAF, placed downstream of the positive feedback, shape the temporal ERK activity profile but are dispensable for oscillations. Thus, the positive feedback introduces a hierarchy among negative feedback loops, such that the effect of a negative feedback depends on its position with respect to the positive feedback loop. Furthermore, a combination of the fast positive feedback involving slow-diffusing membrane components with slower negative feedbacks involving faster diffusing cytoplasmic components leads to local excitation/global inhibition dynamics, which allows the MAPK cascade to transmit paracrine EGF signals into spatially non-uniform ERK activity pulses.

  5. Absolute small-angle measurement based on optical feedback interferometry

    Institute of Scientific and Technical Information of China (English)

    Jingang Zhong; Xianhua Zhang; Zhixiang Ju

    2008-01-01

    We present a simple but effective method for small-angle measurement based on optical feedback inter-ferometry (or laser self-mixing interferometry). The absolute zero angle can be defined at the biggest fringe amplitude point, so this method can also achieve absolute angle measurement. In order to verify the method, we construct an angle measurement system. The Fourier-transform method is used to analysis the interference signal. Rotation angles are experimentally measured with a resolution of 10-6 rad and a measurement range of approximately from -0.0007 to +0.0007 rad.

  6. Effects of unwanted feedback on synchronized chaotic optical communications.

    Science.gov (United States)

    Li, Xiaofeng; Pan, Wei; Luo, Bin; Ma, Dong

    2006-04-10

    The effects of unwanted external optical feedback on synchronized chaotic optical communication systems are studied numerically. We consider an open-loop configuration consisting of a transmitter laser with double external optical feedbacks and a receiver laser with optical injection from the transmitter laser. First, including the effects of unwanted optical feedback, the synchronization performances of both the complete synchronization and the generalized synchronization are examined. Then the encoding and decoding performances of the generalized synchronization and the effects of the introduced feedback are investigated, respectively. Finally, we study the control of the unwanted feedback on the dynamics of the transmitter laser and briefly discuss the system security when the transmitter laser is driven to operate in a steady state or periodic oscillation state by the additional feedback.

  7. Lyapunov exponent of chaos generated by acousto-optic modulators with feedback

    Science.gov (United States)

    Ghosh, Anjan K.; Verma, Pramode

    2011-01-01

    Generation of chaos from acousto-optic modulators with an electronic feedback has been studied for several years. Such chaotic signals have an important application in providing secure encryption in free-space optical communication systems. Lyapunov exponent is an important parameter for analysis of chaos generated by a nonlinear system. The Lyapunov exponent of an acousto-optic system is determined and calculated in this paper to understand the dependence of the chaotic response on the system parameters such as bias, feedback gain, input intensity and initial condition exciting the cell. Analysis of chaos using Lyapunov exponent is consistent with bifurcation analysis and is useful in encrypting data signals.

  8. Effect of External Optical Feedback for Nano-laser Structures

    DEFF Research Database (Denmark)

    Taghizadeh, Alireza; Mørk, Jesper; Chung, Il-Sug

    2013-01-01

    We theoretically investigated the effect of optical feedback on a photonic crystal nanolaser, comparing with conventional in-plane and vertical-cavity lasers.......We theoretically investigated the effect of optical feedback on a photonic crystal nanolaser, comparing with conventional in-plane and vertical-cavity lasers....

  9. Optical feedback in dfb quantum cascade laser for mid-infrared cavity ring-down spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Terabayashi, Ryohei, E-mail: terabayashi.ryouhei@h.mbox.nagoya-u.ac.jp; Sonnenschein, Volker, E-mail: volker@nagoya-u.jp; Tomita, Hideki, E-mail: tomita@nagoya-u.jp; Hayashi, Noriyoshi, E-mail: hayashi.noriyoshi@h.mbox.nagoya-u.ac.jp; Kato, Shusuke, E-mail: katou.shuusuke@f.mbox.nagoya-u.ac.jp; Jin, Lei, E-mail: kin@nuee.nagoya-u.ac.jp; Yamanaka, Masahito, E-mail: yamanaka@nuee.nagoya-u.ac.jp; Nishizawa, Norihiko, E-mail: nishizawa@nuee.nagoya-u.ac.jp [Nagoya University, Department of Quantum Engineering, Graduate School of Engineering (Japan); Sato, Atsushi, E-mail: atsushi.sato@sekisui.com; Nozawa, Kohei, E-mail: kohei.nozawa@sekisui.com; Hashizume, Kenta, E-mail: kenta.hashizume@sekisui.com; Oh-hara, Toshinari, E-mail: toshinari.ohara@sekisui.com [Sekisui Medical Co., Ltd., Drug Development Solutions Center (Japan); Iguchi, Tetsuo, E-mail: t-iguchi@nucl.nagoya-u.ac.jp [Nagoya University, Department of Quantum Engineering, Graduate School of Engineering (Japan)

    2017-11-15

    A simple external optical feedback system has been applied to a distributed feedback quantum cascade laser (DFB QCL) for cavity ring-down spectroscopy (CRDS) and a clear effect of feedback was observed. A long external feedback path length of up to 4m can decrease the QCL linewidth to around 50kHz, which is of the order of the transmission linewidth of our high finesse ring-down cavity. The power spectral density of the transmission signal from high finesse cavity reveals that the noise at frequencies above 20kHz is reduced dramatically.

  10. Reliability of high power laser diodes with external optical feedback

    Science.gov (United States)

    Bonsendorf, Dennis; Schneider, Stephan; Meinschien, Jens; Tomm, Jens W.

    2016-03-01

    Direct diode laser systems gain importance in the fields of material processing and solid-state laser pumping. With increased output power, also the influence of strong optical feedback has to be considered. Uncontrolled optical feedback is known for its spectral and power fluctuation effects, as well as potential emitter damage. We found that even intended feedback by use of volume Bragg gratings (VBG) for spectral stabilization may result in emitter lifetime reduction. To provide stable and reliable laser systems design, guidelines and maximum feedback ratings have to be found. We present a model to estimate the optical feedback power coupled back into the laser diode waveguide. It includes several origins of optical feedback and wide range of optical elements. The failure thresholds of InGaAs and AlGaAs bars have been determined not only at standard operation mode but at various working points. The influence of several feedback levels to laser diode lifetime is investigated up to 4000h. The analysis of the semiconductor itself leads to a better understanding of the degradation process by defect spread. Facet microscopy, LBIC- and electroluminescence measurements deliver detailed information about semiconductor defects before and after aging tests. Laser diode protection systems can monitor optical feedback. With this improved understanding, the emergency shutdown threshold can be set low enough to ensure laser diode reliability but also high enough to provide better machine usability avoiding false alarms.

  11. Optical time-lens signal processing

    DEFF Research Database (Denmark)

    Oxenløwe, Leif Katsuo; Galili, Michael; Mulvad, Hans Christian Hansen;

    2014-01-01

    This paper describes the use of optical time lenses for optical signal processing of advanced optical data signals. Examples given include 1.28 Tbaud Nyquist channel serial-to-parallel conversion and spectral magnification of OFDM signals.......This paper describes the use of optical time lenses for optical signal processing of advanced optical data signals. Examples given include 1.28 Tbaud Nyquist channel serial-to-parallel conversion and spectral magnification of OFDM signals....

  12. Experimental research on dual polarized laser optical feedback microscope

    Institute of Scientific and Technical Information of China (English)

    MAO Wei; ZHANG Shu-lian; TAN Yi-dong

    2005-01-01

    The principle of laser optical feedback microscope was presented and demonstrated. Three methods to advance the vertical resolution of laser optical feedback microscope were experimentally studied. The first one is to detect the two polarized lights' intensities separately with a Wollaston prism instead of to detect the whole light's intensity. The second is that both of the two orthogonally polarized lights of a birefringent dual frequency laser are fed back. The third one is that only one of the orthogonally polarized lights is fed back. The experimental results show that the modes competition between orthogonally polarized lights can be used to improve the vertical resolution of laser optical feedback microscope effectively.

  13. An optical analog signal transmitter

    Energy Technology Data Exchange (ETDEWEB)

    Fudzita, K.; Itida, T.; Tanaka, Kh.

    1984-01-11

    An optical laser analog signal transmitter employing an amplitude modulated subcarrier is patented; this transmitter performs stable and high quality transmission of information signals over great distances. A feature of the proposed transmitter is a special transmitter operational mode in which the light emission reflected off the connection point to the fiber optic conduit is sent back to the laser diode in a transient period. As a result, the critical mode of the generated emission is not influenced by the reflected signal. The transmitter consists of a laser diode with biasing near the cutoff point, an amplitude modulator with a subcarrier frequency oscillator, a section of flexible fiber-optic cable of length L, which connects the laser diode to the primary optical fiber conduit, and the connector itself. The subcarrier frequency may vary over wide ranges to establish the necessary correlation between the length of the light conduit section L and the return propagation time of the reflected light signal from the connection point to the laser diode. The difference between the lasing time of the light signal and the return time to the laser diode of the signal reflected off the connector is determined by the relation tau equals 2nL/c - mtauc, where L is the length of the connecting section; n is the refractivity of the optical fiber; c is the velocity of light; tauc is the period of the high frequency subcarrier signal; and m is an integer.

  14. Experimental demonstration of coherent feedback control on optical field squeezing

    CERN Document Server

    Iida, Sanae; Yonezawa, Hidehiro; Yamamoto, Naoki; Furusawa, Akira

    2011-01-01

    Coherent feedback is a non-measurement based, hence a back-action free, method of control for quantum systems. A typical application of this control scheme is squeezing enhancement, a purely non-classical effect in quantum optics. In this paper we report its first experimental demonstration that well agrees with the theory taking into account time delays and losses in the coherent feedback loop. The results clarify both the benefit and the limitation of coherent feedback control in a practical situation.

  15. Optical Signal Processing

    Science.gov (United States)

    1990-02-28

    compatible with the laser cation in the on-line inspection of products such as source. Thus, if the laser wavelength is z850 nm, hypodermic needles ...agreer.nt with the theory , and support our claims concerning the high performance level of our acousto-optir. architecture. We recognized the opportunity to...systems have always required a high degree of complexity, and, with the advent of fiber-optic communication , these systems are now becoming information flow

  16. Tuning positive feedback for signal detection in noisy dynamic environments.

    Science.gov (United States)

    Johansson, Anders; Ramsch, Kai; Middendorf, Martin; Sumpter, David J T

    2012-09-21

    Learning from previous actions is a key feature of decision-making. Diverse biological systems, from neuronal assemblies to insect societies, use a combination of positive feedback and forgetting of stored memories to process and respond to input signals. Here we look how these systems deal with a dynamic two-armed bandit problem of detecting a very weak signal in the presence of a high degree of noise. We show that by tuning the form of positive feedback and the decay rate to appropriate values, a single tracking variable can effectively detect dynamic inputs even in the presence of a large degree of noise. In particular, we show that when tuned appropriately a simple positive feedback algorithm is Fisher efficient, in that it can track changes in a signal on a time of order L(h)=(|h|/σ)(-2), where |h| is the magnitude of the signal and σ the magnitude of the noise.

  17. Strong optical feedback in birefringent dual frequency laser

    Institute of Scientific and Technical Information of China (English)

    Mao Wei; Zhang Shu-Lian

    2006-01-01

    Strong optical feedback in a birefringent dual frequency He-Ne laser with a high reflectivity feedback mirror has been investigated for the first time. The output characteristics of two orthogonally polarized modes are demonstrated in two different optical feedback cases: one is for both modes being fed back and the other is for only one of the modes being fed back. Strong mode competition can be observed between the two modes with strong optical feedback. And when one mode's intensity is near its maximum, the other mode is nearly extinguished. When both modes are fed back into the laser cavity, the mode competition is stronger than when only one mode is fed back. The difference in initial intensity between the two orthogonally polarized modes plays an important role in the mode competition, which has been experimentally and theoretically demonstrated.

  18. Sinusoidal phase-modulating fiber-optic interferometer fringe with a feedback control system.

    Science.gov (United States)

    Lv, Changrong; Duan, Fajie; Bo, En; Duan, Xiaojie; Feng, Fan; Fu, Xiao

    2014-09-20

    A displacement measurement system using a fiber-optic interferometer fringe projector with a feedback control system is presented and demonstrated. The system utilizes the integrating bucket method to detect the desired phase or the displacement and Fresnel reflection signal to realize measurement of the disturbance and feed it back to the modulated signal of the laser at the same time. The continuous signal truly reflects the error information, as the output light and reflected light share the same optical path. Practical experiments validate the feasibility of this method.

  19. Optical feedback characteristics in a dual-frequency laser during laser cavity tuning

    Institute of Scientific and Technical Information of China (English)

    Liu Gang; Zhang Shu-Lian; Li Yan; Zhu Jun

    2005-01-01

    The optical feedback characteristics in a Zeeman-birefringence dual-frequency laser are studied during the laser cavity tuning in three different kinds of optical feedback conditions: (i) only //-light is fed back; (ii) only (┴)-light is fed back; (iii) both lights are fed back. A compact displacement sensor is designed using the experimental result that there is a nearly 90 degrees phase delay between the two lights' cosine optical feedback signals when both lights are fed back into the laser cavity. The priority order that the two lights' intensity curves appear can be used for direction discrimination. The resolution of the displacement sensor is at least 79 nm, and the sensor can discriminate the target's moving direction easily.

  20. Coherent feedback control of multipartite quantum entanglement for optical fields

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Zhihui; Jia, Xiaojun; Xie, Changde; Peng, Kunchi [State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan, 030006 (China)

    2011-12-15

    Coherent feedback control (CFC) of multipartite optical entangled states produced by a nondegenerate optical parametric amplifier is theoretically studied. The features of the quantum correlations of amplitude and phase quadratures among more than two entangled optical modes can be controlled by tuning the transmissivity of the optical beam splitter in the CFC loop. The physical conditions to enhance continuous variable multipartite entanglement of optical fields utilizing the CFC loop are obtained. The numeric calculations based on feasible physical parameters of realistic systems provide direct references for the design of experimental devices.

  1. Current Developments on Optical Feedback Interferometry as an All-Optical Sensor for Biomedical Applications

    Directory of Open Access Journals (Sweden)

    Julien Perchoux

    2016-05-01

    Full Text Available Optical feedback interferometry (OFI sensors are experiencing a consistent increase in their applications to biosensing due to their contactless nature, low cost and compactness, features that fit very well with current biophotonics research and market trends. The present paper is a review of the work in progress at UPC-CD6 and LAAS-CNRS related to the application of OFI to different aspects of biosensing, both in vivo and ex vivo. This work is intended to present the variety of opportunities and potential applications related to OFI that are available in the field. The activities presented are divided into two main sensing strategies: The measurement of optical path changes and the monitoring of flows, which correspond to sensing strategies linked to the reconstruction of changes of amplitude from the interferometric signal, and to classical Doppler frequency measurements, respectively. For optical path change measurements, measurements of transient pulses, usual in biosensing, together with the measurement of large displacements applied to designing palliative care instrumentation for Parkinson disease are discussed. Regarding the Doppler-based approach, progress in flow-related signal processing and applications in real-time monitoring of non-steady flows, human blood flow monitoring and OFI pressure myograph sensing will be presented. In all cases, experimental setups are discussed and results presented, showing the versatility of the technique. The described applications show the wide capabilities in biosensing of the OFI sensor, showing it as an enabler of low-cost, all-optical, high accuracy biomedical applications.

  2. A birefringent cavity He-Ne laser and optical feedback

    Institute of Scientific and Technical Information of China (English)

    Liu Gang; Zhang Shu-Lian; Li Yan; Zhu Jun

    2004-01-01

    Strong modes competition makes only one of o-light and e-light oscillate in a birefringent dual-frequency laser when the angle between the crystalline axis and the laser beam is nearly zero. When the oscillated mode is in a different part of the gain curve, the detected intensity curves of o-light and e-light are quite different in the existence of optical feedback. The curves are divided into five cases. Three cases of the experimental results can be used for direction discrimination. The polarization characteristics of the birefringent cavity He-Ne laser are also discussed without optical feedback.

  3. Sensitivity of quantum-dot semiconductor lasers to optical feedback.

    Science.gov (United States)

    O'Brien, D; Hegarty, S P; Huyet, G; Uskov, A V

    2004-05-15

    The sensitivity of quantum-dot semiconductor lasers to optical feedback is analyzed with a Lang-Kobayashi approach applied to a standard quantum-dot laser model. The carriers are injected into a quantum well and are captured by, or escape from, the quantum dots through either carrier-carrier or phonon-carrier interaction. Because of Pauli blocking, the capture rate into the dots depends on the carrier occupancy level in the dots. Here we show that different carrier capture dynamics lead to a strong modification of the damping of the relaxation oscillations. Regions of increased damping display reduced sensitivity to optical feedback even for a relatively large alpha factor.

  4. Return-map for semiconductor lasers with optical feedback

    DEFF Research Database (Denmark)

    Mørk, Jesper; Tromborg, Bjarne; Sabbatier, H.;

    1999-01-01

    It is well known that a semiconductor laser exposed to moderate optical feedback and biased near threshold exhibits the phenomenon of low-frequency intensity fluctuations (LFF). While this behavior can be numerically simulated using the so-called Lang-Kobayshi model, the interpretation of the phe......It is well known that a semiconductor laser exposed to moderate optical feedback and biased near threshold exhibits the phenomenon of low-frequency intensity fluctuations (LFF). While this behavior can be numerically simulated using the so-called Lang-Kobayshi model, the interpretation...

  5. Imaging of acoustic fields using optical feedback interferometry.

    Science.gov (United States)

    Bertling, Karl; Perchoux, Julien; Taimre, Thomas; Malkin, Robert; Robert, Daniel; Rakić, Aleksandar D; Bosch, Thierry

    2014-12-01

    This study introduces optical feedback interferometry as a simple and effective technique for the two-dimensional visualisation of acoustic fields. We present imaging results for several pressure distributions including those for progressive waves, standing waves, as well as the diffraction and interference patterns of the acoustic waves. The proposed solution has the distinct advantage of extreme optical simplicity and robustness thus opening the way to a low cost acoustic field imaging system based on mass produced laser diodes.

  6. Multichannel decision feedback equalizer for high track density in optical recording

    Science.gov (United States)

    Gopalaswamy, Srinivasan; Kumar, B. V. K.

    1996-08-01

    A possible approach to high track density in optical recording is to reduce the track widths and eliminate the spacing between consecutive tracks. Parallel readback of several tracks and combined equalization of the multitrack readback signals is a viable approach toward reducing the deteriorating effects of interference in such a high-track- density system. Multichannel readback using laser diode arrays has been reported in optical recording. An additional advantage of multitrack readback is a high data rate. A novel multichannel decision feedback equalizer to reduce interference both within and across the tracks using 2D feedback is presented. Simulation results shows good improvement in error-rate performance by using multichannel decision feedback equalization. By this readback method, tracks can be brought closer, thus increasing the areal density.

  7. Diversity of optical signal processing led by optical signal form conversion

    Energy Technology Data Exchange (ETDEWEB)

    Konishi, Tsuyoshi, E-mail: konishi@mls.eng.osaka-u.ac.j [Osaka University, 2-1 Yamadaoka, Suita Osaka 565-0871 (Japan)

    2010-02-01

    This paper reviews opportunities of optical signal form conversion as typified by time-space conversion in optical signal processing. Several examples of typical ultra-fast optical signal processing using optical signal form conversion are described and their applications are introduced in respect to photonic networks, ultra-fast measurement, and so on.

  8. Delta- Sigma Modulator with Signal Dependant Feedback Gain

    Directory of Open Access Journals (Sweden)

    K.Diwakar

    2015-02-01

    Full Text Available Higher order Delta-Sigma Modulator (DSM is basically an unstable system. The approximate conditions for stability cannot be used for the design of a DSM for industrial applications where risk is involved. The conventional second order, single stage, single bit, unity feedback gain, discrete DSM cannot be used for the normalized full range (-1 to +1 of input signal since the DSM becomes unstable when the modulus of the input signal is above 0.55. The stability is also not guaranteed for amplitude of input signal less than 0.55. In this proposal, the conventional second order DSM is modified with input signal dependant feedback path gain. The proposed DSM is suitable for industrial applications where one needs the digital representation of the analog input signal, during each sampling period. This first configuration of proposed DSM can operate for the full range of input signal without causing instability. In order to improve the SNR of first configuration, it is combined with conventional second order DSM and proposed the second configuration of DSM.

  9. THE DETERMINATION OF A CRITICAL VALUE FOR DYNAMIC STABILITY OF SEMICONDUCTOR LASER DIODE WITH EXTERNAL OPTICAL FEEDBACK

    Directory of Open Access Journals (Sweden)

    Remzi YILDIRIM

    1998-01-01

    Full Text Available In this study, dynamic stability analysis of semiconductor laser diodes with external optical feedback has been realized. In the analysis the frequency response of the transfer function of laser diode H jw( , the transfer m function of laser diode with external optical feedback TF jw( , and optical feedback transfer function m K jw( obtained from small signal equations has been m accomplished using Nyquist stability analysis in complex domain. The effect of optical feedback on the stability of the system has been introduced and to bring the laser diode to stable condition the working critical boundary range of dampig frequency and reflection power constant (R has been determined. In the study the reflection power has been taken as ( .

  10. Nonlinear modification of the laser noise power spectrum induced by a frequency-shifted optical feedback

    CERN Document Server

    Lacot, Eric; Girardeau, Vadim; Hugon, Olivier; Jacquin, Olivier

    2016-01-01

    In this article, we study the non-linear coupling between the stationary (i.e. the beating modulation signal) and transient (i.e. the laser quantum noise) dynamics of a laser subjected to frequency shifted optical feedback. We show how the noise power spectrum and more specifically the relaxation oscillation frequency of the laser are modified under different optical feedback condition. Specifically we study the influence of (i) the amount of light returning to the laser cavity and (ii) the initial detuning between the frequency shift and intrinsic relaxation frequency. The present work shows how the relaxation frequency is related to the strength of the beating signal and the shape of the noise power spectrum gives an image of the Transfer Modulation Function (i.e. of the amplification gain) of the nonlinear-laser dynamics.The theoretical predictions, confirmed by numerical resolutions, are in good agreements with the experimental data.

  11. Energy-Efficient Optical Signal Processing Using Optical Time Lenses

    DEFF Research Database (Denmark)

    Oxenløwe, Leif Katsuo; Galili, Michael; Mulvad, Hans Christian Hansen;

    2015-01-01

    This chapter describes advanced functionalities for optical signal processing using optical time lenses. A special focus is devoted to functionalities that allow for energy-savings. In particular, we find that optical signal processing, where the processing is broadband and capable of handling ma...

  12. Narrow-linewidth photonic microwave generation based on an optically injected 1550 nm VCSEL subject to optoelectronic feedback

    Science.gov (United States)

    Liang, Qing; Fan, Li; Yang, Ji-Yun; Wang, Zhen-Zhen; Wu, Zheng-Mao; Xia, Guang-Qiong

    2016-11-01

    High-quality photonic microwave generation is experimentally demonstrated based on the period-one (P1) dynamical state output from an optically injected 1550 nm vertical-cavity surface-emitting laser (1550 nm-VCSEL) subject to optoelectronic negative feedback. The experimental results show that, under suitable injection condition, the 1550 nm-VCSEL can generate a photonic microwave signal with single sideband optical spectrum structure, but the linewidth of the microwave signal is relatively wide (on the order of MHz). After further introducing optoelectronic negative feedback, the linewidth of the microwave signal can be narrowed two orders of magnitude to 105.7 kHz. Furthermore, for the case that the feedback strength is set at an optimized value, the frequency of the microwave signal can be tuned continuously within a certain range through simply adjusting the injection strength.

  13. Feedback Regulation of Kinase Signaling Pathways by AREs and GREs.

    Science.gov (United States)

    Vlasova-St Louis, Irina; Bohjanen, Paul R

    2016-01-25

    In response to environmental signals, kinases phosphorylate numerous proteins, including RNA-binding proteins such as the AU-rich element (ARE) binding proteins, and the GU-rich element (GRE) binding proteins. Posttranslational modifications of these proteins lead to a significant changes in the abundance of target mRNAs, and affect gene expression during cellular activation, proliferation, and stress responses. In this review, we summarize the effect of phosphorylation on the function of ARE-binding proteins ZFP36 and ELAVL1 and the GRE-binding protein CELF1. The networks of target mRNAs that these proteins bind and regulate include transcripts encoding kinases and kinase signaling pathways (KSP) components. Thus, kinase signaling pathways are involved in feedback regulation, whereby kinases regulate RNA-binding proteins that subsequently regulate mRNA stability of ARE- or GRE-containing transcripts that encode components of KSP.

  14. Feedback Regulation of Kinase Signaling Pathways by AREs and GREs

    Directory of Open Access Journals (Sweden)

    Irina Vlasova-St. Louis

    2016-01-01

    Full Text Available In response to environmental signals, kinases phosphorylate numerous proteins, including RNA-binding proteins such as the AU-rich element (ARE binding proteins, and the GU-rich element (GRE binding proteins. Posttranslational modifications of these proteins lead to a significant changes in the abundance of target mRNAs, and affect gene expression during cellular activation, proliferation, and stress responses. In this review, we summarize the effect of phosphorylation on the function of ARE-binding proteins ZFP36 and ELAVL1 and the GRE-binding protein CELF1. The networks of target mRNAs that these proteins bind and regulate include transcripts encoding kinases and kinase signaling pathways (KSP components. Thus, kinase signaling pathways are involved in feedback regulation, whereby kinases regulate RNA-binding proteins that subsequently regulate mRNA stability of ARE- or GRE-containing transcripts that encode components of KSP.

  15. Feedback control of optical beam spatial profiles using thermal lensing

    CERN Document Server

    Liu, Zhanwei; Arain, Muzammil A; Williams, Luke; Mueller, Guido; Tanner, David B; Reitze, David H

    2013-01-01

    A method for active control of the spatial profile of a laser beam using adaptive thermal lensing is described. A segmented electrical heater was used to generate thermal gradients across a transmissive optical element, resulting in a controllable thermal lens. The segmented heater also allows the generation of cylindrical lenses, and provides the capability to steer the beam in both horizontal and vertical planes. Using this device as an actuator, a feedback control loop was developed to stabilize the beam size and position.

  16. All-optical signal processing technique for secure optical communication

    Science.gov (United States)

    Qian, Feng-chen; Su, Bing; Ye, Ya-lin; Zhang, Qian; Lin, Shao-feng; Duan, Tao; Duan, Jie

    2015-10-01

    Secure optical communication technologies are important means to solve the physical layer security for optical network. We present a scheme of secure optical communication system by all-optical signal processing technique. The scheme consists of three parts, as all-optical signal processing unit, optical key sequence generator, and synchronous control unit. In the paper, all-optical signal processing method is key technology using all-optical exclusive disjunction (XOR) gate based on optical cross-gain modulation effect, has advantages of wide dynamic range of input optical signal, simple structure and so on. All-optical XOR gate composed of two semiconductor optical amplifiers (SOA) is a symmetrical structure. By controlling injection current, input signal power, delay and filter bandwidth, the extinction ratio of XOR can be greater than 8dB. Finally, some performance parameters are calculated and the results are analyzed. The simulation and experimental results show that the proposed method can be achieved over 10Gbps optical signal encryption and decryption, which is simple, easy to implement, and error-free diffusion.

  17. A hidden feedback in signaling cascades is revealed.

    Directory of Open Access Journals (Sweden)

    Alejandra C Ventura

    2008-03-01

    Full Text Available Cycles involving covalent modification of proteins are key components of the intracellular signaling machinery. Each cycle is comprised of two interconvertable forms of a particular protein. A classic signaling pathway is structured by a chain or cascade of basic cycle units in such a way that the activated protein in one cycle promotes the activation of the next protein in the chain, and so on. Starting from a mechanistic kinetic description and using a careful perturbation analysis, we have derived, to our knowledge for the first time, a consistent approximation of the chain with one variable per cycle. The model we derive is distinct from the one that has been in use in the literature for several years, which is a phenomenological extension of the Goldbeter-Koshland biochemical switch. Even though much has been done regarding the mathematical modeling of these systems, our contribution fills a gap between existing models and, in doing so, we have unveiled critical new properties of this type of signaling cascades. A key feature of our new model is that a negative feedback emerges naturally, exerted between each cycle and its predecessor. Due to this negative feedback, the system displays damped temporal oscillations under constant stimulation and, most important, propagates perturbations both forwards and backwards. This last attribute challenges the widespread notion of unidirectionality in signaling cascades. Concrete examples of applications to MAPK cascades are discussed. All these properties are shared by the complete mechanistic description and our simplified model, but not by previously derived phenomenological models of signaling cascades.

  18. Feedback control in quantum optics: an overview of experimental breakthroughs and areas of application

    CERN Document Server

    Serafini, Alessio

    2012-01-01

    We present a broad summary of research involving the application of quantum feedback control techniques to optical set-ups, from the early enhancement of optical amplitude squeezing to the recent stabilisation of photon number states in a microwave cavity, dwelling mostly on the latest experimental advances. Feedback control of quantum optical continuous variables, quantum non-demolition memories, feedback cooling, quantum state control, adaptive quantum measurements and coherent feedback strategies will all be touched upon in our discussion.

  19. Feedback control in quantum optics: an overview of experimental breakthroughs and areas of application

    OpenAIRE

    Alessio Serafini

    2012-01-01

    We present a broad summary of research involving the application of quantum feedback control techniques to optical set-ups, from the early enhancement of optical amplitude squeezing to the recent stabilisation of photon number states in a microwave cavity, dwelling mostly on the latest experimental advances. Feedback control of quantum optical continuous variables, quantum non-demolition memories, feedback cooling, quantum state control, adaptive quantum measurements and coherent feedback str...

  20. Maxwell's demon in biochemical signal transduction with feedback loop.

    Science.gov (United States)

    Ito, Sosuke; Sagawa, Takahiro

    2015-06-23

    Signal transduction in living cells is vital to maintain life itself, where information transfer in noisy environment plays a significant role. In a rather different context, the recent intensive research on 'Maxwell's demon'-a feedback controller that utilizes information of individual molecules-have led to a unified theory of information and thermodynamics. Here we combine these two streams of research, and show that the second law of thermodynamics with information reveals the fundamental limit of the robustness of signal transduction against environmental fluctuations. Especially, we find that the degree of robustness is quantitatively characterized by an informational quantity called transfer entropy. Our information-thermodynamic approach is applicable to biological communication inside cells, in which there is no explicit channel coding in contrast to artificial communication. Our result could open up a novel biophysical approach to understand information processing in living systems on the basis of the fundamental information-thermodynamics link.

  1. Optical Performance Monitoring and Signal Optimization in Optical Networks

    DEFF Research Database (Denmark)

    Petersen, Martin Nordal

    2006-01-01

    -optical-electrical regeneration points decreases. This thesis evaluates the impact of signal degrading effects that are becoming of increasing concern in all-optical high-speed networks due to all-optical switching and higher bit-rates. Especially group-velocity-dispersion (GVD) and a number of nonlinear effects will require......The thesis studies performance monitoring for the next generation optical networks. The focus is on all-optical networks with bit-rates of 10 Gb/s or above. Next generation all-optical networks offer large challenges as the optical transmitted distance increases and the occurrence of electrical...... enhanced attention to avoid signal degradations. The requirements for optical performance monitoring features are discussed, and the thesis evaluates the advantages and necessity of increasing the level of performance monitoring parameters in the physical layer. In particular, methods for optical...

  2. Dynamics of semiconductor microring lasers subject to on-chip filtered optical feedback

    Science.gov (United States)

    Khoder, Mulham; Friart, Gaetan; Danckaert, Jan; Erneux, Thomas; Van der Sande, Guy; Verschaffelt, Guy

    2016-04-01

    Tunable laser diodes are needed in a range of applications including wavelength division multiplexing, optical instrument testing, optical sensing and tera hertz generation. In this work, we investigate the stability of lasers which use filtered optical feedback for wavelength tuning. We investigate experimentally the dynamics induced by this on-chip filtered optical feedback. In this study, we choose to use a compact device which combines a semiconductor ring laser with on-chip filtered optical feedback to achieve wavelength tunability. The filtered optical feedback is realized by employing two arrayed waveguide gratings to split/recombine light into different wavelength channels. Semiconductor optical amplifiers are placed in the feedback loop in order to control the feedback of each wavelength channel independently. Experimental observations show that the stability of the clockwise and counterclockwise propagation modes depends on the feedback strength. Experiments also show that for a specific range of the feedback strength, anti-phase oscillations in the intensity of the clockwise and counterclockwise propagating modes can be induced. These oscillations could not be seen in the same semiconductor ring laser without filtered optical feedback. We investigate how the frequency and the amplitude of these oscillations change under the effect of filtered optical feedback. We also discuss how these anti-phase oscillations can be suppressed by properly choosing the feedback strength.

  3. All-Optical Flip-Flop Based on an SOA/DFB-Laser Diode Optical Feedback Scheme

    DEFF Research Database (Denmark)

    D'Oosterlinck, W.; Buron, Jakob Due; Öhman, Filip;

    2007-01-01

    We report on the dynamic all-optical flip-flop (AOFF) operation of an optical feedback scheme consisting of a semiconductor optical amplifier (SOA) and a distributed feedback laser diode (DFB-LD), bidirectionally coupled to each other. The operation of the AOFF relies on the interplay between...

  4. Pulse operation of semiconductor laser with nonlinear optical feedback

    Science.gov (United States)

    Guignard, Celine; Besnard, Pascal; Mihaescu, Adrian; MacDonald, K. F.; Pochon, Sebastien; Zheludev, Nikolay I.

    2004-09-01

    A semiconductor laser coupled to a gallium-made non linear mirror may exhibit pulse regime. In order to better understand this coupled cavity, stationary solutions and dynamics are described following the standard Lang and Kobayashi equations for a semiconductor laser submitted to nonlinear optical feedback. It is shown that the nonlinearity distorts the ellipse on which lied the stationary solutions, with a ``higher'' part corresponding to lower reflectivity and a ``lower'' part to higher reflectivity. Bifurcation diagrams and nonlinear analysis are presented while the conditions for pulsed operation are discussed.

  5. Limitations of synthetic aperture laser optical feedback imaging

    CERN Document Server

    Glastre, Wilfried; Hugon, Olivier; De Chatellus, Hugues Guillet; Lacot, Eric

    2012-01-01

    In this paper we present the origin and the effect of amplitude and phase noise on Laser Optical Feedback Imaging (LOFI) associated with Synthetic Aperture (SA) imaging system. Amplitude noise corresponds to photon noise and acts as an additive noise, it can be reduced by increasing the global measurement time. Phase noise can be divided in three families: random, sinusoidal and drift phase noise; we show that it acts as a multiplicative noise. We explain how we can reduce it by making oversampling or multiple measurements depending on its type. This work can easily be extended to all SA systems (Radar, Laser or Terahertz), especially when raw holograms are acquired point by point.

  6. Negative Avalanche Feedback Detectors for Photon-Counting Optical Communications

    Science.gov (United States)

    Farr, William H.

    2009-01-01

    Negative Avalanche Feedback photon counting detectors with near-infrared spectral sensitivity offer an alternative to conventional Geiger mode avalanche photodiode or phototube detectors for free space communications links at 1 and 1.55 microns. These devices demonstrate linear mode photon counting without requiring any external reset circuitry and may even be operated at room temperature. We have now characterized the detection efficiency, dark count rate, after-pulsing, and single photon jitter for three variants of this new detector class, as well as operated these uniquely simple to use devices in actual photon starved free space optical communications links.

  7. Negative Avalanche Feedback Detectors for Photon-Counting Optical Communications

    Science.gov (United States)

    Farr, William H.

    2009-01-01

    Negative Avalanche Feedback photon counting detectors with near-infrared spectral sensitivity offer an alternative to conventional Geiger mode avalanche photodiode or phototube detectors for free space communications links at 1 and 1.55 microns. These devices demonstrate linear mode photon counting without requiring any external reset circuitry and may even be operated at room temperature. We have now characterized the detection efficiency, dark count rate, after-pulsing, and single photon jitter for three variants of this new detector class, as well as operated these uniquely simple to use devices in actual photon starved free space optical communications links.

  8. Feedback control of Layerwise Laser Melting using optical sensors

    Science.gov (United States)

    Craeghs, Tom; Bechmann, Florian; Berumen, Sebastian; Kruth, Jean-Pierre

    Layerwise Laser Melting (LLM) is a layerwise production technique enabling the production of complex metallic parts. Thin powder layers are molten according to a predefined scan pattern by means of a laser source. Nowadays constant process parameters are used throughout the build, leading for some geometries to an overly thick feature size or overheating at downfacing surfaces. In this paper a monitoring and control system is presented which enables monitoring the melt pool continously at high speed throughout the building process. The signals from the sensors can be incorporated in a real-time control loop, in this way enabling feedback control of the process parameters. In this paper the experimental set-up will be first shown. Next the dynamic relation between the melt pool and the process parameters is identified. Finally the proof of concept for feedback control is demonstrated with experimental results.

  9. A Case Study of Representing Signal Transduction in Liver Cells as a Feedback Control Problem

    Science.gov (United States)

    Singh, Abhay; Jayaraman, Arul; Hahn, Juergen

    2007-01-01

    Cell signaling pathways often contain feedback loops where proteins are produced that regulate signaling. While feedback regulatory mechanisms are commonly found in signaling pathways, there is no example available in the literature that is simple enough to be presented in an undergraduate control class. This paper presents a simulation study of…

  10. Feedback-free optical cavity with self-resonating mechanism

    CERN Document Server

    Uesugi, Y; Honda, Y; Kosuge, A; Omori, T; Takahashi, T; Urakawa, J; Washio, M

    2015-01-01

    We demonstrated the operation of a high finesse optical cavity without utilizing an active feedback system to stabilize the resonance. The finesse of the cavity was measured to be $465,000 \\pm 3,000$, and the laser power stored in the cavity was $2.52 \\pm 0.13$ kW, which is about 187,000 times greater than the incident power to the cavity. The stored power was stabilized with a fluctuation of $1.7 \\%$, and we confirmed continuous cavity operation for more than two hours. This result relaxes the technical requirement of stabilizing of the optical resonant cavity and expands possibilities for various applications such as laser-Compton scattering.

  11. Effect of optoelectronic feedback on the characteristics of acousto-optical collinear filtering

    Energy Technology Data Exchange (ETDEWEB)

    Balakshy, V I; Kuznetsov, Yu I; Mantsevich, S N [Department of Physics, M.V. Lomonosov Moscow State University (Russian Federation)

    2016-02-28

    The first results of the theoretical and experimental studies of an acousto-optical system with feedback based on a collinear cell made of a calcium molybdate crystal are presented. It is shown that the positive electronic feedback allows essential sharpening of the instrument function of the acousto-optical collinear filter, thus increasing the precision of measuring the optical radiation wavelength. (acoustooptics)

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

    DEFF Research Database (Denmark)

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

    2014-01-01

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

  13. Optical Processing of High Dimensionality Signals

    DEFF Research Database (Denmark)

    Da Ros, Francesco

    signal processing, including wavelength conversion, optical phase conjugation (OPC), and signal regeneration. This project focuses precisely on the applications of OPAs for all-optical signal processing with a two-fold focus: on the one hand, processing the advanced modulation formats required......) waveguides, are investigated. The limits of parametric amplification for 16-quadrature amplitude modulation (QAM) signals are first characterized. The acquired knowledge is then applied to the design of a black-box OPC-device used to provide Kerr nonlinearity compensation for a 5-channel polarization......-division multiplexing (PDM) 16-QAM signal at 1.12 Tbps with significant improvements in received signal quality. Furthermore, the first demonstration of phase regeneration for binary phase-shift keying (BPSK) signals using the silicon platform is presented. The silicon-based OPA relies on a novel design where a reverse...

  14. Fast photonic information processing using semiconductor lasers with delayed optical feedback: role of phase dynamics.

    Science.gov (United States)

    Nguimdo, Romain Modeste; Verschaffelt, Guy; Danckaert, Jan; Van der Sande, Guy

    2014-04-01

    Semiconductor lasers subject to delayed optical feedback have recently shown great potential in solving computationally hard tasks. By optically implementing a neuro-inspired computational scheme, called reservoir computing, based on the transient response to optical data injection, high processing speeds have been demonstrated. While previous efforts have focused on signal bandwidths limited by the semiconductor laser's relaxation oscillation frequency, we demonstrate numerically that the much faster phase response makes significantly higher processing speeds attainable. Moreover, this also leads to shorter external cavity lengths facilitating future on-chip implementations. We numerically benchmark our system on a chaotic time-series prediction task considering two different feedback configurations. The results show that a prediction error below 4% can be obtained when the data is processed at 0.25 GSamples/s. In addition, our insight into the phase dynamics of optical injection in a semiconductor laser also provides a clear understanding of the system performance at different pump current levels, even below solitary laser threshold. Considering spontaneous emission noise and noise in the readout layer, we obtain good prediction performance at fast processing speeds for realistic values of the noise strength.

  15. Serial optical communications and ultra-fast optical signal processing of Tbit/s data signals

    DEFF Research Database (Denmark)

    Oxenløwe, Leif Katsuo; Galili, Michael; Hu, Hao;

    2010-01-01

    This paper reviews our recent advances in ultra-high speed serial optical communications. It describes Tbit/s optical signal processing and various materials allowing for this, as well as network scenarios embracing this technology......This paper reviews our recent advances in ultra-high speed serial optical communications. It describes Tbit/s optical signal processing and various materials allowing for this, as well as network scenarios embracing this technology...

  16. Parametric Amplification For Detecting Weak Optical Signals

    Science.gov (United States)

    Hemmati, Hamid; Chen, Chien; Chakravarthi, Prakash

    1996-01-01

    Optical-communication receivers of proposed type implement high-sensitivity scheme of optical parametric amplification followed by direct detection for reception of extremely weak signals. Incorporates both optical parametric amplification and direct detection into optimized design enhancing effective signal-to-noise ratios during reception in photon-starved (photon-counting) regime. Eliminates need for complexity of heterodyne detection scheme and partly overcomes limitations imposed on older direct-detection schemes by noise generated in receivers and by limits on quantum efficiencies of photodetectors.

  17. Amplitude Noise Reduction of Ion Lasers with Optical Feedback

    Science.gov (United States)

    Herring, Gregory C.

    2011-01-01

    A reduction in amplitude noise on the output of a multi-mode continuous-wave Ar-ion laser was previously demonstrated when a fraction of the output power was retroreflected back into the laser cavity. This result was reproduced in the present work and a Fabry-Perot etalon was used to monitor the longitudinal mode structure of the laser. A decrease in the number of operating longitudinal cavity modes was observed simultaneously with the introduction of the optical feedback and the onset of the amplitude noise reduction. The noise reduction is a result of a reduced number of lasing modes, resulting in less mode beating and amplitude fluctuations of the laser output power.

  18. Microcantilever Displacement Measurement Using a Mechanically Modulated Optical Feedback Interferometer

    Directory of Open Access Journals (Sweden)

    Francisco J. Azcona

    2016-06-01

    Full Text Available Microcantilever motion detection is a useful tool for the characterization of the physical, chemical and biological properties of materials. In the past, different approaches have been proposed and tested to enhance the behavior, size and simplicity of microcantilever motion detectors. In this paper, a new approach to measure microcantilever motion with nanometric resolution is presented. The proposed approach is based on the concept of mechanically-modulated optical feedback interferometry, a technique that has shown displacement measurement capabilities well within the nanometric scale and that, due to its size, compactness and low cost, may be a suitable choice for measuring nanometric motions in cantilever-like sensors. It will be shown that the sensor, in its current state of development, is capable of following a cantilever sinusoidal trajectory at different sets of frequencies ranging up to 200 Hz and peak to peak amplitudes up to λ / 2 with experimental resolutions in the λ / 100 range.

  19. Radio Science from an Optical Communications Signal

    Science.gov (United States)

    Moision, Bruce; Asmar, Sami; Oudrhiri, Kamal

    2013-01-01

    NASA is currently developing the capability to deploy deep space optical communications links. This creates the opportunity to utilize the optical link to obtain range, doppler, and signal intensity estimates. These may, in turn, be used to complement or extend the capabilities of current radio science. In this paper we illustrate the achievable precision in estimating range, doppler, and received signal intensity of an non-coherent optical link (the current state-of-the-art for a deep-space link). We provide a joint estimation algorithm with performance close to the bound. We draw comparisons to estimates based on a coherent radio frequency signal, illustrating that large gains in either precision or observation time are possible with an optical link.

  20. Optical Wavelet Signals Processing and Multiplexing

    Science.gov (United States)

    Cincotti, Gabriella; Moreolo, Michela Svaluto; Neri, Alessandro

    2005-12-01

    We present compact integrable architectures to perform the discrete wavelet transform (DWT) and the wavelet packet (WP) decomposition of an optical digital signal, and we show that the combined use of planar lightwave circuits (PLC) technology and multiresolution analysis (MRA) can add flexibility to current multiple access optical networks. We furnish the design guidelines to synthesize wavelet filters as two-port lattice-form planar devices, and we give some examples of optical signal denoising and compression/decompression techniques in the wavelet domain. Finally, we present a fully optical wavelet packet division multiplexing (WPDM) scheme where data signals are waveform-coded onto wavelet atom functions for transmission, and numerically evaluate its performances.

  1. Time-Delay Signature of Chaotic Vertical-Cavity Surface-Emitting Lasers with Polarization-Rotated Optical Feedback

    Institute of Scientific and Technical Information of China (English)

    XIANG Shui-Ying; PAN Wei; YAN Lian-Shan; LUO Bin; ZOU Xi-Hua; JIANG Ning; WEN Kun-Hua

    2011-01-01

    To quantitatively evaluate the time-delay (TD) signatures of chaotic signals generated by vertical-cavity surface-emitting lasers (VCSELs) with polarization-rotated optical feedback (PROF), we propose four cases of resolution coefficients R based on correlation functions. The resolution coefficient characteristics for the x-polarization (XP) mode, y-polarization (YP) mode and the total output are considered. The dependences of R on the feedback strength and feedback delay are discussed and compared carefully. The two-dimensional maps of R show that the TD signatures for the single polarization mode (I.e., XP or YP mode) are much more difficult to retrieve than those for the total output in the entire parameter space. Thus, by using single polarization mode as a chaotic carrier, the TD signatures are extremely difficult to be identified, which contributes a lot in the security-enhanced VCSELs-based chaotic optical communication systems.

  2. Signal Processing for Optical Networks

    Science.gov (United States)

    2007-11-02

    understanding and enhancing a number of important recent wavelet-based and DCT- based image coders. We show that Shapiro’s well-known EZW scheme, Said and...comparable to Shapiro’s EZW coder (J. M. Shapiro, "Embedded image coding using zerotrees of wavelet coefficients", IEEE Trans, on Signal Processing, v. 41

  3. Optical feedback characteristics in a helium neon laser with a birefringent internal cavity

    Institute of Scientific and Technical Information of China (English)

    Mao Wei; Zhang Shu-Lian; Xu Ting; Wan Xin-Jun; Liu Gang

    2007-01-01

    The output characteristics of optical feedback in a helium-neon laser with a birefringent internal cavity are studied systematically in five different regions of the gain curve for the two orthogonally polarized modes. When the laser operates in the two end regions of the laser gain curve, one of the two orthogonally polarized modes will be a leading one in optical feedback. Strong mode competition can be observed. However, when the laser operates in the middle region of the laser gain curve, the two modes can oscillate equally with optical feedback. Besides the intensity of the two polarized lights, the total light intensity is also studied at the same time. M-shaped optical feedback curves are found. Particularly, when the average intensities of the two lights are comparable, the intensity modulation curve of the total light is doubled, which can be used to improve the resolution of an optical feedback system.

  4. Information Feedback Strategies in a Signal Controlled Network with Overlapped Routes

    Institute of Scientific and Technical Information of China (English)

    TIAN Li-Jun; HUANG Hai-Jun; LIU Tian-Liang

    2009-01-01

    We investigate the effects of four different information feedback strategies on the dynamics of traffic, travel-ers' route choice and the resultant system performance in a signal controlled network with overlapped routes.Simulation results given by the cellular automaton model show that the system purpose-based mean velocity feedback strategy and the congestion coefficient feedback strategy have more advantages in improving network utilization efficiency and reducing travelers' travel times. The travel time feedback strategy and the individual purposed-based mean velocity feedback strategy behave slightly better to ensure user equity.

  5. Frequency and time domain analysis of an external cavity laser with strong filtered optical feedback

    DEFF Research Database (Denmark)

    Detoma, Enrico; Tromborg, Bjarne; Montrosset, Ivo

    -signal analysis in the frequency domain allows a calculation of the range of operation without mode hopping around the grating reflectivity peak. This region should be as large as possible for proper operation of the tunable laser source. The analysis shows this stabilizing effect of mode coupling and gain......The stability properties of an external cavity laser with strong grating-filtered optical feedback to an anti-reflection coated facet are studied with a general frequency domain model. The model takes into account non-linear effects like four wave mixing and gain compression. A small...... copression in the lasing mode. An integral equation for the electrical field is derived from the frequency domain model and used for time domain simulations of large-signal behavior....

  6. Implementation and Tuning of an Optical Tweezers Force-Clamp Feedback System.

    Science.gov (United States)

    Bugiel, Michael; Jannasch, Anita; Schäffer, Erik

    2017-01-01

    Feedback systems can be used to control the value of a system variable. In optical tweezers, active feedback is often implemented to either keep the position or tension applied to a single biomolecule constant. Here, we describe the implementation of the latter: an optical force-clamp setup that can be used to study the motion of processive molecular motors under a constant load. We describe the basics of a software-implemented proportional-integral-derivative (PID) controller, how to tune it, and how to determine its optimal feedback rate. Limitations, possible feed-forward applications, and extensions into two- and three-dimensional optical force clamps are discussed. The feedback is ultimately limited by thermal fluctuations and the compliance of the involved molecules. To investigate a particular mechanical process, understanding the basics and limitations of the feedback system will be helpful for choosing the proper feedback hardware, for optimizing the system parameters, and for the design of the experiment.

  7. Quantum Dot Devices for Optical Signal Processing

    DEFF Research Database (Denmark)

    Chen, Yaohui

    . Additional to the static linear amplication properties, we focus on exploring the gain dynamics on the time scale ranging from sub-picosecond to nanosecond. In terms of optical signals that have been investigated, one is the simple sinusoidally modulated optical carrier with a typical modulation frequency...... range of 1-100 gigahertz. Our simulations reveal the role of ultrafast intradot carrier dynamics in enhancing modulation bandwidth of quantum dot semiconductor optical ampliers. Moreover, the corresponding coherent gain response also provides rich dispersion contents over a broad bandwidth. One...... important implementation is recently boosted by the research in slow light. The idea is to migrate such dynamical gain knowledge for the investigation of microwave phase shifter based on semiconductor optical waveguide. Our study reveals that phase shifting based on the conventional semiconductor optical...

  8. Clustering in Cell Cycle Dynamics with General Response/Signaling Feedback

    CERN Document Server

    Young, Todd; Buckalew, Richard; Moses, Gregory; Boczko, Erik; 10.1016/j.jtbi.2011.10.002.

    2011-01-01

    Motivated by experimental and theoretical work on autonomous oscillations in yeast, we analyze ordinary differential equations models of large populations of cells with cell-cycle dependent feedback. We assume a particular type of feedback that we call Responsive/Signaling (RS), but do not specify a functional form of the feedback. We study the dynamics and emergent behaviour of solutions, particularly temporal clustering and stability of clustered solutions. We establish the existence of certain periodic clustered solutions as well as "uniform" solutions and add to the evidence that cell-cycle dependent feedback robustly leads to cell-cycle clustering. We highlight the fundamental differences in dynamics between systems with negative and positive feedback. For positive feedback systems the most important mechanism seems to be the stability of individual isolated clusters. On the other hand we find that in negative feedback systems, clusters must interact with each other to reinforce coherence. We conclude fr...

  9. SDN-Enabled Dynamic Feedback Control and Sensing in Agile Optical Networks

    Science.gov (United States)

    Lin, Likun

    monitoring sensors. In order to maintain signal quality while optimizing network resources, we find that it is essential to model and update estimates of the physical link impairments in real-time. In this thesis, we consider the key elements required to enable an agile optical network, with contributions as follows: • Control Framework: extended the SDN concept to include the optical transport network through extensions to the OpenFlow (OF) protocol. A unified SDN control plane is built to facilitate control and management capability across the electrical/packet-switched and optical/circuit-switched portions of the network seamlessly. The SDN control plane serves as a platform to abstract the resources of multilayer/multivendor networks. Through this platform, applications can dynamically request the network resources to meet their service requirements. • Use of In-situ Monitors: enabled real-time physical impairment sensing in the control plane using in-situ Optical Performance Monitoring (OPM) and bit error rate (BER) analyzers. OPM and BER values are used as quantitative indicators of the link status and are fed to the control plane through a high-speed data collection interface to form a closed-loop feedback system to enable adaptive resource allocation. • Predictive Network Model: used a network model embedded in the control layer to study the link status. The estimated results of network status is fed into the control decisions to precompute the network resources. The performance of the network model can be enhanced by the sensing results. • Real-Time Control Algorithms: investigated various dynamic resource allocation mechanisms supporting an agile optical network. Intelligent routing and wavelength switching for recovering from traffic impairments is achieved experimentally in the agile optical network within one second. A distance-adaptive spectrum allocation scheme to address transmission impairments caused by cascaded Wavelength Selective Switches (WSS

  10. Electro-optical techniques for signal conditioning

    Science.gov (United States)

    Helfrich, R. W.

    1981-01-01

    Electro-optical (EO) processing is discussed as a potential alternative to the all-digital approach to signal processing. Nonuniformity compensation can be done by normalizing all the single element detectors outputs in a staring array for both gain and level. Distortion correction can be accomplished with blackbodies, scene statistics or defocused optics. An algorithm used in digital signal conditioning that can be closely approximated by EO techniques is Local Area Brightness Control (LABC). In a digital processor, LABC is performed on a pixel-by-pixel basis, resulting in an enormous amount of calculation. A partially defocused optical system can be used in an EO analog to the digital system. For both nonuniformity compensation and LABC, the EO technique can result in great simplification.

  11. COMPENSATION OF OUTPUT SIGNAL TEMPERATURE DEPENDENCE IN HOMODYNE DEMODULATION TECHNIQUE FOR PHASE FIBER-OPTIC SENSORS

    Directory of Open Access Journals (Sweden)

    M. V. Mekhrengin

    2015-03-01

    Full Text Available Modified phase-generated carrier homodyne demodulation technique for fiber-optic sensors is presented. Nowadays phase-generated carrier homodyne demodulation technique is one of the most widespread. One of its drawbacks is the temperature dependence of the output signal because of the modulator scale factor temperature dependence. In order to compensate this dependence an automatic adjustment of the phase modulation depth is necessary. To achieve the result, additional harmonics analysis is used with the help of the Bessel functions. For this purpose the known demodulation scheme is added with the branch, where interferometric signal is multiplied by the third harmonic of the modulation signal. The deviation of optimal ratio of odd harmonics is used as a feedback signal for adjusting the modulation depth. Unwanted emissions arise in the feedback signal, when the third harmonic possesses a value close to zero. To eliminate unwanted emission in the feedback signal, the principle scheme is added with one more branch, where interferometric signal is multiplied by the forth harmonic of the modulation signal. The deviation of optimal ratio of even harmonics is used as a feedback signal alternately with the deviation of optimal ratio of odd harmonics. A mathematical model of the algorithm is designed using the MATLAB package. Results of modeling have confirmed that suggested method gives the possibility for an automatic adjustment of the phase modulation depth and makes it possible to compensate temperature dependence for the modulator scale factor and output signal magnitude.

  12. Optically tunable microwave, millimeter-wave and submillimeter-wave utilizing single-mode Fabry-Pérot laser diode subject to optical feedback.

    Science.gov (United States)

    Wu, Jian-Wei; Nakarmi, Bikash; Won, Yong Hyub

    2016-02-01

    In this paper, we use optical feedback injection technique to generate tunable microwave, millimeter-wave and submillimeter-wave signals using single-mode Fabry-Pérot laser diode. The beat frequency of the proposed generator ranges from 30.4 GHz to 3.40 THz. The peak power ratio between two resonating modes at the output spectrum of can be less than 0.5 dB by judiciously selecting feedback wavelength. In the stabilization test, the peak fluctuation of photonic signal is as low as 0.19 dB within half hour. Aside from locking regions, where the laser is easily locked by the injection beam, the side-mode suppression ratio is well over 25 dB with the maximum value of 36.6 dB at 30.4 GHz beat frequency. In addition, the minimum beat frequency interval between two adjacent photonic signals is as low as 10 GHz.

  13. Mesolimbic confidence signals guide perceptual learning in the absence of external feedback.

    Science.gov (United States)

    Guggenmos, Matthias; Wilbertz, Gregor; Hebart, Martin N; Sterzer, Philipp

    2016-03-29

    It is well established that learning can occur without external feedback, yet normative reinforcement learning theories have difficulties explaining such instances of learning. Here, we propose that human observers are capable of generating their own feedback signals by monitoring internal decision variables. We investigated this hypothesis in a visual perceptual learning task using fMRI and confidence reports as a measure for this monitoring process. Employing a novel computational model in which learning is guided by confidence-based reinforcement signals, we found that mesolimbic brain areas encoded both anticipation and prediction error of confidence-in remarkable similarity to previous findings for external reward-based feedback. We demonstrate that the model accounts for choice and confidence reports and show that the mesolimbic confidence prediction error modulation derived through the model predicts individual learning success. These results provide a mechanistic neurobiological explanation for learning without external feedback by augmenting reinforcement models with confidence-based feedback.

  14. Randomised prior feedback modulates neural signals of outcome monitoring.

    Science.gov (United States)

    Mushtaq, Faisal; Wilkie, Richard M; Mon-Williams, Mark A; Schaefer, Alexandre

    2016-01-15

    Substantial evidence indicates that decision outcomes are typically evaluated relative to expectations learned from relatively long sequences of previous outcomes. This mechanism is thought to play a key role in general learning and adaptation processes but relatively little is known about the determinants of outcome evaluation when the capacity to learn from series of prior events is difficult or impossible. To investigate this issue, we examined how the feedback-related negativity (FRN) is modulated by information briefly presented before outcome evaluation. The FRN is a brain potential time-locked to the delivery of decision feedback and it is widely thought to be sensitive to prior expectations. We conducted a multi-trial gambling task in which outcomes at each trial were fully randomised to minimise the capacity to learn from long sequences of prior outcomes. Event-related potentials for outcomes (Win/Loss) in the current trial (Outcomet) were separated according to the type of outcomes that occurred in the preceding two trials (Outcomet-1 and Outcomet-2). We found that FRN voltage was more positive during the processing of win feedback when it was preceded by wins at Outcomet-1 compared to win feedback preceded by losses at Outcomet-1. However, no influence of preceding outcomes was found on FRN activity relative to the processing of loss feedback. We also found no effects of Outcomet-2 on FRN amplitude relative to current feedback. Additional analyses indicated that this effect was largest for trials in which participants selected a decision different to the gamble chosen in the previous trial. These findings are inconsistent with models that solely relate the FRN to prediction error computation. Instead, our results suggest that if stable predictions about future events are weak or non-existent, then outcome processing can be determined by affective systems. More specifically, our results indicate that the FRN is likely to reflect the activity of positive

  15. Quantitative identification of dynamical transitions in a semiconductor laser with optical feedback

    Science.gov (United States)

    Quintero-Quiroz, C.; Tiana-Alsina, J.; Romà, J.; Torrent, M. C.; Masoller, C.

    2016-01-01

    Identifying transitions to complex dynamical regimes is a fundamental open problem with many practical applications. Semi- conductor lasers with optical feedback are excellent testbeds for studying such transitions, as they can generate a rich variety of output signals. Here we apply three analysis tools to quantify various aspects of the dynamical transitions that occur as the laser pump current increases. These tools allow to quantitatively detect the onset of two different regimes, low-frequency fluctuations and coherence collapse, and can be used for identifying the operating conditions that result in specific dynamical properties of the laser output. These tools can also be valuable for analyzing regime transitions in other complex systems. PMID:27857229

  16. Information transfer through a signaling module with feedback: a perturbative approach

    CERN Document Server

    Aquino, Gerardo

    2015-01-01

    Signal transduction in biological cells is effected by signaling pathways that typically include multiple feedback loops. Here we analyze information transfer through a prototypical signaling module with biochemical feedback. The module switches stochastically between an inactive and active state; the input to the module governs the activation rate while the output (i.e., the product concentration) perturbs the inactivation rate. Using a novel perturbative approach, we compute the rate with which information about the input is gained from observation of the output. We obtain an explicit analytical result valid to first order in feedback strength and to second order in the strength of input. The total information gained during an extended time interval is found to depend on the feedback strength only through the total number of activation/inactivation events.

  17. Differential growth triggers mechanical feedback that elevates Hippo signaling.

    Science.gov (United States)

    Pan, Yuanwang; Heemskerk, Idse; Ibar, Consuelo; Shraiman, Boris I; Irvine, Kenneth D

    2016-10-26

    Mechanical stress can influence cell proliferation in vitro, but whether it makes a significant contribution to growth control in vivo, and how it is modulated and experienced by cells within developing tissues, has remained unclear. Here we report that differential growth reduces cytoskeletal tension along cell junctions within faster-growing cells. We propose a theoretical model to explain the observed reduction of tension within faster-growing clones, supporting it by computer simulations based on a generalized vertex model. This reduced tension modulates a biomechanical Hippo pathway, decreasing recruitment of Ajuba LIM protein and the Hippo pathway kinase Warts, and decreasing the activity of the growth-promoting transcription factor Yorkie. These observations provide a specific mechanism for a mechanical feedback that contributes to evenly distributed growth, and we show that genetically suppressing mechanical feedback alters patterns of cell proliferation in the developing Drosophila wing. By providing experimental support for the induction of mechanical stress by differential growth, and a molecular mechanism linking this stress to the regulation of growth in developing organs, our results confirm and extend the mechanical feedback hypothesis.

  18. 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.

  19. Amplified feedback DFB laser for 40 Gb/s all-optical clock recovery

    Science.gov (United States)

    Chen, Cheng; Sun, Yu; Zhao, Lingjuan; Pan, Jiaoqing; Qiu, Jifang; Liang, Song; Wang, Wei; Lou, Caiyun

    2011-12-01

    A monolithic integrated amplified feedback semiconductor laser (AFL) was fabricated based on quantum well intermixing (QWI) technique. The AFL works as a self-pulsation laser. It consists of a gain-coupled multiple quantum well distribute feedback (DFB) laser diode (LD) section, a passive phase section and an amplified feedback section. The free-running repetition frequency of the AFL can be tuned from 32 GHz to 51 GHz via controlling the feedback strength. All-optical 40 Gb/s clock recovery was experimentally demonstrated using the AFL with a low timing jitter.

  20. Effects of Signal Spectrum Bandwidth on Different PMD Compensation Feedback Methods

    Institute of Scientific and Technical Information of China (English)

    Na Young Kim; Duckey Lee; Sangin Kim; Namkyoo Park

    2003-01-01

    We compared efficiencies of different PMD compensation feedback methods against transmission signal bandwidth,including NRZ, RZ, CRZ format under various duty cycles. We found that the critical factor determining the efficiency of PMD compensation is not the modulation format, but the spectral bandwidth of the transmission signal.

  1. Effects of Signal Spectrum Bandwidth on Different PMD Compensation Feedback Methods

    Institute of Scientific and Technical Information of China (English)

    Na; Young; Kim; Duckey; Lee; Sangin; Kim; Namkyoo; Park

    2003-01-01

    We compared efficiencies of different PMD compensation feedback methods against transmission signal bandwidth, including NRZ, RZ, CRZ format under various duty cycles. We found that the critical factor determining the efficiency of PMD compensation is not the modulation format, but the spectral bandwidth of the transmission signal.

  2. Theoretical modeling of the dynamics of a semiconductor laser subject to double-reflector optical feedback

    Science.gov (United States)

    Bakry, A.; Abdulrhmann, S.; Ahmed, M.

    2016-06-01

    We theoretically model the dynamics of semiconductor lasers subject to the double-reflector feedback. The proposed model is a new modification of the time-delay rate equations of semiconductor lasers under the optical feedback to account for this type of the double-reflector feedback. We examine the influence of adding the second reflector to dynamical states induced by the single-reflector feedback: periodic oscillations, period doubling, and chaos. Regimes of both short and long external cavities are considered. The present analyses are done using the bifurcation diagram, temporal trajectory, phase portrait, and fast Fourier transform of the laser intensity. We show that adding the second reflector attracts the periodic and perioddoubling oscillations, and chaos induced by the first reflector to a route-to-continuous-wave operation. During this operation, the periodic-oscillation frequency increases with strengthening the optical feedback. We show that the chaos induced by the double-reflector feedback is more irregular than that induced by the single-reflector feedback. The power spectrum of this chaos state does not reflect information on the geometry of the optical system, which then has potential for use in chaotic (secure) optical data encryption.

  3. Theoretical modeling of the dynamics of a semiconductor laser subject to double-reflector optical feedback

    Energy Technology Data Exchange (ETDEWEB)

    Bakry, A. [King Abdulaziz University, 80203, Department of Physics, Faculty of Science (Saudi Arabia); Abdulrhmann, S. [Jazan University, 114, Department of Physics, Faculty of Sciences (Saudi Arabia); Ahmed, M., E-mail: mostafa.farghal@mu.edu.eg [King Abdulaziz University, 80203, Department of Physics, Faculty of Science (Saudi Arabia)

    2016-06-15

    We theoretically model the dynamics of semiconductor lasers subject to the double-reflector feedback. The proposed model is a new modification of the time-delay rate equations of semiconductor lasers under the optical feedback to account for this type of the double-reflector feedback. We examine the influence of adding the second reflector to dynamical states induced by the single-reflector feedback: periodic oscillations, period doubling, and chaos. Regimes of both short and long external cavities are considered. The present analyses are done using the bifurcation diagram, temporal trajectory, phase portrait, and fast Fourier transform of the laser intensity. We show that adding the second reflector attracts the periodic and perioddoubling oscillations, and chaos induced by the first reflector to a route-to-continuous-wave operation. During this operation, the periodic-oscillation frequency increases with strengthening the optical feedback. We show that the chaos induced by the double-reflector feedback is more irregular than that induced by the single-reflector feedback. The power spectrum of this chaos state does not reflect information on the geometry of the optical system, which then has potential for use in chaotic (secure) optical data encryption.

  4. All-Optical flip-flop operation using a SOA and DFB laser diode optical feedback combination

    DEFF Research Database (Denmark)

    D'Oosterlinck, W.; Öhman, Filip; Buron, Jakob Due;

    2007-01-01

    We report on the switching of an all-optical flip-flop consisting of a semiconductor optical amplifier (SOA) and a distributed feedback laser diode (DFB), bidirectionally coupled to each other. Both simulation and experimental results are presented. Switching times as low as 50ps, minimal required...

  5. Beam shaping in high-power broad-area quantum cascade lasers using optical feedback

    Science.gov (United States)

    Ferré, Simon; Jumpertz, Louise; Carras, Mathieu; Ferreira, Robson; Grillot, Frédéric

    2017-03-01

    Broad-area quantum cascade lasers with high output powers are highly desirable sources for various applications including infrared countermeasures. However, such structures suffer from strongly deteriorated beam quality due to multimode behavior, diffraction of light and self-focusing. Quantum cascade lasers presenting high performances in terms of power and heat-load dissipation are reported and their response to a nonlinear control based on optical feedback is studied. Applying optical feedback enables to efficiently tailor its near-field beam profile. The different cavity modes are sequentially excited by shifting the feedback mirror angle. Further control of the near-field profile is demonstrated using spatial filtering. The impact of an inhomogeneous gain as well as the influence of the cavity width are investigated. Compared to existing technologies, that are complex and costly, beam shaping with optical feedback is a more flexible solution to obtain high-quality mid-infrared sources.

  6. Two-dimensional optical feedback control of Euglena confined in closed-type microfluidic channels.

    Science.gov (United States)

    Ozasa, Kazunari; Lee, Jeesoo; Song, Simon; Hara, Masahiko; Maeda, Mizuo

    2011-06-07

    We examined two-dimensional (2D) optical feedback control of phototaxis flagellate Euglena cells confined in closed-type microfluidic channels (microaquariums), and demonstrated that the 2D optical feedback enables the control of the density and position of Euglena cells in microaquariums externally, flexibly, and dynamically. Using three types of feedback algorithms, the density of Euglena cells in a specified area can be controlled arbitrarily and dynamically, and more than 70% of the cells can be concentrated into a specified area. Separation of photo-sensitive/insensitive Euglena cells was also demonstrated. Moreover, Euglena-based neuro-computing has been achieved, where 16 imaginary neurons were defined as Euglena-activity levels in 16 individual areas in microaquariums. The study proves that 2D optical feedback control of photoreactive flagellate microbes is promising for microbial biology studies as well as applications such as microbe-based particle transportation in microfluidic channels or separation of photo-sensitive/insensitive microbes.

  7. Beam shaping in high-power broad-area quantum cascade lasers using optical feedback

    Science.gov (United States)

    Ferré, Simon; Jumpertz, Louise; Carras, Mathieu; Ferreira, Robson; Grillot, Frédéric

    2017-01-01

    Broad-area quantum cascade lasers with high output powers are highly desirable sources for various applications including infrared countermeasures. However, such structures suffer from strongly deteriorated beam quality due to multimode behavior, diffraction of light and self-focusing. Quantum cascade lasers presenting high performances in terms of power and heat-load dissipation are reported and their response to a nonlinear control based on optical feedback is studied. Applying optical feedback enables to efficiently tailor its near-field beam profile. The different cavity modes are sequentially excited by shifting the feedback mirror angle. Further control of the near-field profile is demonstrated using spatial filtering. The impact of an inhomogeneous gain as well as the influence of the cavity width are investigated. Compared to existing technologies, that are complex and costly, beam shaping with optical feedback is a more flexible solution to obtain high-quality mid-infrared sources. PMID:28287175

  8. Response and fluctuations of a two-state signaling module with feedback

    CERN Document Server

    Gopalakrishnan, Manoj; Jülicher, Frank; Zapotocky, Martin

    2007-01-01

    We study the stochastic kinetics of a signaling module consisting of a two-state stochastic point process with negative feedback. In the active state, a product is synthesized which increases the active-to-inactive transition rate of the process. We analyze this simple autoregulatory module using a path-integral technique based on the temporal statistics of state flips of the process. We develop a systematic framework to calculate averages, autocorrelations, and response functions by treating the feedback as a weak perturbation. Explicit analytical results are obtained to first order in the feedback strength. Monte Carlo simulations are performed to test the analytical results in the weak feedback limit and to investigate the strong feedback regime. We conclude by relating some of our results to experimental observations in the olfactory and visual sensory systems.

  9. Two-dimensional dissipative rogue waves due to time-delayed feedback in cavity nonlinear optics

    Science.gov (United States)

    Tlidi, Mustapha; Panajotov, Krassimir

    2017-01-01

    We demonstrate a way to generate two-dimensional rogue waves in two types of broad area nonlinear optical systems subject to time-delayed feedback: in the generic Lugiato-Lefever model and in the model of a broad-area surface-emitting laser with saturable absorber. The delayed feedback is found to induce a spontaneous formation of rogue waves. In the absence of delayed feedback, spatial pulses are stationary. The rogue waves are exited and controlled by the delay feedback. We characterize their formation by computing the probability distribution of the pulse height. The long-tailed statistical contribution, which is often considered as a signature of the presence of rogue waves, appears for sufficiently strong feedback. The generality of our analysis suggests that the feedback induced instability leading to the spontaneous formation of two-dimensional rogue waves is a universal phenomenon.

  10. OUTPUT FEEDBACK CONTROL FOR MIMO NONLINEAR SYSTEMS WITH EXOGENOUS SIGNALS

    Institute of Scientific and Technical Information of China (English)

    Ying ZHOU; Yuqiang WU

    2006-01-01

    The paper addresses the global output tracking of a class of multi-input multi-output(MIMO) nonlinear systems affected by disturbances, which are generated by a known exosystem. An adaptive controller is designed based on the proposed observer and the backstepping approach to asymptotically track arbitrary reference signal and to guarantee the boundedness of all the signals in the closed loop system. Finally, the numerical simulation results illustrate the effectiveness of the proposed scheme.

  11. Method for high-speed Manchester encoded optical signal generation

    DEFF Research Database (Denmark)

    Zhang, Jianfeng; Chi, Nan; Holm-Nielsen, Pablo Villanueva

    2004-01-01

    A method for high-speed Manchester encoded optical signal generation is proposed and demonstrated with a specially configured electro-optical modulator. A 10 Gb/s Manchester encoded optical signal was generated, and its bit-error-ratio (BER) performance was evaluated.......A method for high-speed Manchester encoded optical signal generation is proposed and demonstrated with a specially configured electro-optical modulator. A 10 Gb/s Manchester encoded optical signal was generated, and its bit-error-ratio (BER) performance was evaluated....

  12. Feedback.

    Science.gov (United States)

    Richardson, Barbara K

    2004-12-01

    The emergency department provides a rich environment for diverse patient encounters, rapid clinical decision making, and opportunities to hone procedural skills. Well-prepared faculty can utilize this environment to teach residents and medical students and gain institutional recognition for their incomparable role and teamwork. Giving effective feedback is an essential skill for all teaching faculty. Feedback is ongoing appraisal of performance based on direct observation aimed at changing or sustaining a behavior. Tips from the literature and the author's experience are reviewed to provide formats for feedback, review of objectives, and elements of professionalism and how to deal with poorly performing students. Although the following examples pertain to medical student education, these techniques are applicable to the education of all adult learners, including residents and colleagues. Specific examples of redirection and reflection are offered, and pitfalls are reviewed. Suggestions for streamlining verbal and written feedback and obtaining feedback from others in a fast-paced environment are given. Ideas for further individual and group faculty development are presented.

  13. Bubbling effect in the electro-optic delayed feedback oscillator coupled network

    Science.gov (United States)

    Liu, Lingfeng; Lin, Jun; Miao, Suoxia

    2017-03-01

    Synchronization in the optical systems coupled network always suffers from bubbling events. In this paper, we numerically investigate the statistical properties of the synchronization characteristics and bubbling effects in the electro-optic delayed feedback oscillator coupled network with different coupling strength, delay time and gain coefficient. Furthermore, we compare our results with the synchronization properties of semiconductor laser (SL) coupled network, which indicates that the electro-optic delayed feedback oscillator can be better to suppress the bubbling effects in the synchronization of coupled network under the same conditions.

  14. High frequency optoelectronic oscillators based on the optical feedback of semiconductor mode-locked laser diodes.

    Science.gov (United States)

    Haji, Mohsin; Hou, Lianping; Kelly, Anthony E; Akbar, Jehan; Marsh, John H; Arnold, John M; Ironside, Charles N

    2012-01-30

    Optical self seeding feedback techniques can be used to improve the noise characteristics of passively mode-locked laser diodes. External cavities such as fiber optic cables can increase the memory of the phase and subsequently improve the timing jitter. In this work, an improved optical feedback architecture is proposed using an optical fiber loop delay as a cavity extension of the mode-locked laser. We investigate the effect of the noise reduction as a function of the loop length and feedback power. The well known composite cavity technique is also implemented for suppressing supermode noise artifacts presented due to harmonic mode locking effects. Using this method, we achieve a record low radio frequency linewidth of 192 Hz for any high frequency (>1 GHz) passively mode-locked laser to date (to the best of the authors' knowledge), making it promising for the development of high frequency optoelectronic oscillators.

  15. Acousto-optic filtering of lidar signals

    Science.gov (United States)

    Kolarov, G.; Deleva, A.; Mitsev, TS.

    1992-01-01

    The predominant part of the noise in lidar receivers is created by the background radiation; therefore, one of the most important elements of the receiving optics is a spectrally selecting filter placed in front of the photodetector. Interference filters are usually used to transmit a given wavelength. Specific properties of the interference filters, such as simple design, reliability, small size, and large aperture, combined with high transmission coefficient and narrow spectral band, make them the preferred spectral device in many cases. However, problems arise in applications such as the Differential Absorption Lidar (DIAL) technique, where fast tuning within a wide spectral region is necessary. Tunable acousto-optical filters (TAOF), used recently in astrophysical observations to suppress the background radiation, can be employed with success in lidar sounding. They are attractive due to the possibility for fast spectral scanning with a narrow transmission band. The TAOF's advantages are fully evident in DIAL lidars where one must simultaneously receive signals at two laser frequencies.

  16. Acousto-optic filtering of lidar signals

    Science.gov (United States)

    Kolarov, G.; Deleva, A.; Mitsev, Ts.

    1992-07-01

    The predominant part of the noise in lidar receivers is created by the background radiation; therefore, one of the most important elements of the receiving optics is a spectrally selecting filter placed in front of the photodetector. Interference filters are usually used to transmit a given wavelength. Specific properties of the interference filters, such as simple design, reliability, small size, and large aperture, combined with high transmission coefficient and narrow spectral band, make them the preferred spectral device in many cases. However, problems arise in applications such as the Differential Absorption Lidar (DIAL) technique, where fast tuning within a wide spectral region is necessary. Tunable acousto-optical filters (TAOF), used recently in astrophysical observations to suppress the background radiation, can be employed with success in lidar sounding. They are attractive due to the possibility for fast spectral scanning with a narrow transmission band. The TAOF's advantages are fully evident in DIAL lidars where one must simultaneously receive signals at two laser frequencies.

  17. 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.

  18. Endogenous field feedback promotes the detectability for exogenous electric signal in the hybrid coupled population

    Energy Technology Data Exchange (ETDEWEB)

    Wei, Xile; Zhang, Danhong; Wang, Jiang; Yu, Haitao, E-mail: htyu@tju.edu.cn [Tianjin Key Laboratory of Process Measurement and Control, School of Electrical Engineering and Automation, Tianjin University, Tianjin 300072 (China); Lu, Meili [School of Informational Technology and Engineering, Tianjin University of Technology and Education, Tianjin 300222 (China); Che, Yanqiu [School of Automation and Electrical Engineering, Tianjin University of Technology and Education, Tianjin 300222 (China)

    2015-01-15

    This paper presents the endogenous electric field in chemical or electrical synaptic coupled networks, aiming to study the role of endogenous field feedback in the signal propagation in neural systems. It shows that the feedback of endogenous fields to network activities can reduce the required energy of the noise and enhance the transmission of input signals in hybrid coupled populations. As a common and important nonsynaptic interactive method among neurons, particularly, the endogenous filed feedback can not only promote the detectability of exogenous weak signal in hybrid coupled neural population but also enhance the robustness of the detectability against noise. Furthermore, with the increasing of field coupling strengths, the endogenous field feedback is conductive to the stochastic resonance by facilitating the transition of cluster activities from the no spiking to spiking regions. Distinct from synaptic coupling, the endogenous field feedback can play a role as internal driving force to boost the population activities, which is similar to the noise. Thus, it can help to transmit exogenous weak signals within the network in the absence of noise drive via the stochastic-like resonance.

  19. Parallel Distribution of Asynchronous Optical Signals

    CERN Document Server

    White, R J; Bradbury, S M; Marshall, P

    2007-01-01

    An eleven channel digital asynchronous transceiver (DAT) employing parallel optical link technology has been developed for trigger signal distribution across the Very Energetic Radiation Imaging Telescope Array System (VERITAS). Combinatorial logic functions are implemented in Xilinx Spartan 3 FPGAs, providing a versatile solution adaptable for use in future atmospheric Cerenkov detectors and other high-energy astroparticle experiments. The device is dead-time free and introduces a minimal skew of 1.6 ns between channels. The jitter on each DAT channel is less than 0.8 ns 95% of the time, allowing communication between telescopes and a central trigger system separated by hundreds of meters, without limiting array performance.

  20. 10 Gb/s full-duplex bidirectional transmission with RSOA-based ONU using detuned optical filtering and decision feedback equalization.

    Science.gov (United States)

    Omella, M; Papagiannakis, I; Schrenk, B; Klonidis, D; Lázaro, J A; Birbas, A N; Kikidis, J; Prat, J; Tomkos, I

    2009-03-30

    Full-duplex bidirectional transmission at 10 Gb/s is demonstrated for extended wavelength division multiplexed passive optical network (WDM-PON) applications, achieving transmission distances up to 25 km of standard single mode fiber (SSMF) when using a low-bandwidth (approximately 1.2 GHz) reflective semiconductor optical amplifier (RSOA) for signal re-modulation at the optical network unit (ONU). The system is assisted by optimum offset filtering at the optical line terminal (OLT)-receiver and the performance is further improved with the use of decision-feedback equalization (DFE). Chromatic dispersion (CD) and Rayleigh Backscattering (RB) effects are considered and analyzed.

  1. Quantum optical feedback control for creating strong correlations in many-body systems

    CERN Document Server

    Mazzucchi, Gabriel; Ivanov, Denis A; Mekhov, Igor B

    2016-01-01

    Light enables manipulating many-body states of matter, and atoms trapped in optical lattices is a prominent example. However, quantum properties of light are completely neglected in all quantum gas experiments. Extending methods of quantum optics to many-body physics will enable phenomena unobtainable in classical optical setups. We show how using the quantum optical feedback creates strong correlations in bosonic and fermionic systems. It balances two competing processes, originating from different fields: quantum backaction of weak optical measurement and many-body dynamics, resulting in stabilized density waves, antiferromagnetic and NOON states. Our approach is extendable to other systems promising for quantum technologies.

  2. The anti-waggle dance: use of the stop signal as negative feedback

    Directory of Open Access Journals (Sweden)

    Parry Macdonald Kietzman

    2015-02-01

    Full Text Available Numerous activities within honey bee (Apis mellifera L. colonies rely on feedback loops for organization at the group level. Classic examples of these self-organizing behaviors occur during foraging and swarm nest site selection. The waggle dance provides positive feedback, promoting foraging at a specific location or increased scouting at a potential nest site. Rather less well known than the waggle dance, the stop signal, a short vibration often delivered while butting against a dancing bee, is currently best understood as a counter to the waggle dance, offering negative feedback towards the advertised foraging location or nest site. When the stop signal is received by a waggle dancer she is more likely to terminate her dance early and retire from the dance floor. Bees that experienced danger or overcrowding at a food source are more likely to perform the stop signal upon their return to the colony, resulting in an inhibition of foraging at that location. During a swarm’s nest site selection process, scout bees that visited a different site than the one being advertised are more likely to stop-signal the waggle dancer than are scouts that had visited the same site. Over time, the scout bees build recruitment to a single site until a quorum is reached and the swarm can move to it. The balance between the positive feedback from the waggle dance and the negative feedback from the stop signal allows for a more sensitive adjustment of response from the colony as a unit. Many of the processes associated with the feedback loops organizing a honey bee colony’s activities are in striking parallel to other systems, such as intercellular interactions involved in motor neuron function.

  3. Delay signatures in the chaotic intensity output of a quantum dot laser with optical feedback

    Indian Academy of Sciences (India)

    VARGHESE BEJOY; JOHN MANU P; NANDAKUMARAN V M

    2016-05-01

    Delay identification from the chaotic intensity output of a quantum dot laser with optical feedback is done using numerical and information theoretic techniques. Four quantifiers, namely autocorrelation function, delayed mutual information, permutation entropy and permutation statistical complexity, are employed in delay estimation. A detailed comparison of these quantifiers with different feedback rates and delay is undertaken. Permutation entropy and permutation statistical complexity are calculated with different dimensions of symbolic reconstruction to obtain the best results.

  4. Recurrent state-switching of a two-state quantum dot laser by optical feedback

    Science.gov (United States)

    Virte, Martin; Breuer, Stefan; Sciamanna, Marc; Panajotov, Krassimir

    2016-04-01

    In this contribution, we experimentally report recurrent switching between ground and excited state emission in a quantum dot laser controlled by optical feedback. We demonstrate that changing the phase of the optical feedback can efficiently induce switching between the two emission processes of the laser. Experimentally, by using an external mirror placed on a piezo-actuator, we were able to achieve incomplete switching between ground and excited state emission, i.e. without complete extinction of the modes. The switching takes place for variations of the external cavity length at the wavelength scale, i.e. around 1.2 um. Theoretically, we successfully link this switching behaviour with the evolution of the modal gain difference between the two modes induced by the variations of the optical feedback phase.

  5. The impact of external optical feedback on the degradation behavior of high-power diode lasers

    DEFF Research Database (Denmark)

    Hempel, Martin; Chi, Mingjun; Petersen, Paul Michael;

    2013-01-01

    The impact of external feedback on high-power diode laser degradation is studied. For this purpose early stages of gradual degradation are prepared by accelerated aging of 808-nm-emitting AlGaAs-based devices. While the quantum well that actually experiences the highest total optical load remains...... unaffected, severe impact is observed to the cladding layers and the waveguide. Consequently hardening of diode lasers for operation under external optical feedback must necessarily involve claddings and waveguide, into which the quantum well is embedded.......The impact of external feedback on high-power diode laser degradation is studied. For this purpose early stages of gradual degradation are prepared by accelerated aging of 808-nm-emitting AlGaAs-based devices. While the quantum well that actually experiences the highest total optical load remains...

  6. Feasibility of a feedback control of atomic self-organization in an optical cavity

    Energy Technology Data Exchange (ETDEWEB)

    Ivanov, D. A., E-mail: ivanov-den@yandex.ru; Ivanova, T. Yu. [St. Petersburg State University (Russian Federation)

    2015-08-15

    Many interesting nonlinear effects are based on the strong interaction of motional degrees of freedom of atoms with an optical cavity field. Among them is the spatial self-organization of atoms in a pattern where the atoms group in either odd or even sites of the cavity-induced optical potential. An experimental observation of this effect can be simplified by using, along with the original cavity-induced feedback, an additional electronic feedback based on the detection of light leaking the cavity and the control of the optical potential for the atoms. Following our previous study, we show that this approach is more efficient from the laser power perspective than the original scheme without the electronic feedback.

  7. Influence of optical feedback on laser frequency spectrum and threshold conditions

    DEFF Research Database (Denmark)

    Osmundsen, Jens Henrik; Gade, Niels

    1983-01-01

    The steady state behavior of the external cavity operated laser has been analyzed, taking into account multiple reflections. The effect of optical feedback is included in the phase- and gain-conditions by a factor which is shown to have a simple geometrical representation. From this representation...... it is easily seen how the laser frequency spectrum and the threshold gain depend on external parameters such as distance to the reflection point and the amount of optical feedback. Furthermore, by inserting a variable attenuator in the external cavity and measuring the threshold current versus transmittance we...... have simultaneously determined the photon lifetime and the absolute amount of optical feedback. For the laser considered we found the photon lifetimetau_{p} = 1.55ps....

  8. All-Optical envelope detection and fiber transmission of wireless signals by external injection of a DFB laser

    DEFF Research Database (Denmark)

    Prince, Kamau; Tafur Monroy, Idelfonso

    2008-01-01

    We outline a novel method for all-optical envelope detection of wireless signals by exploiting cross-gain modulation effects in a distributed feedback laser operating with optical injection. We successfully demonstrate envelope detection of a 20-GHz carrier amplitude-shift-keying modulated signal...... at 2.5 Gb/s and its transmission over a 70-km optical fiber link. We present results including bit-error-rate measurements, signal waveforms, and receiver sensitivity penalties associated with envelope detection and fiber transmission....

  9. All-optical clock recovery of NRZ-DPSK signals using optical resonator-type filters

    DEFF Research Database (Denmark)

    Peucheret, Christophe; Seoane, Jorge; Ji, Hua

    2009-01-01

    It is shown how introducing a limited rise time to the driving signal enables all-optical clock recovery of NRZ-DPSK signals generated using a phase modulator. A Fabry-Perot filter is used to generate the optical clock.......It is shown how introducing a limited rise time to the driving signal enables all-optical clock recovery of NRZ-DPSK signals generated using a phase modulator. A Fabry-Perot filter is used to generate the optical clock....

  10. Ultra-wideband signal generator based on cross gain modulation effect in a distributed feedback laser

    Science.gov (United States)

    Chen, Dalei; Wang, Rong; Xiang, Peng; Pu, Tao; Fang, Tao; Li, Yuandong; Su, Yang; Zheng, Jiling; Huang, Long; Zhu, Huatao; Huang, Jie

    2016-10-01

    In this paper, a novel scheme to generate ultra-wideband (UWB) signals based on cross-gain modulation (XGM) effect in a DFB laser is proposed and experimentally demonstrated, and the modulation and transmission of the UWB signals are also experimentally investigated. In the proposed system, a gain-switched laser (GSL) is used as master laser (ML) and the optical pulses from the ML are optically injected into a DFB laser, which is used as slave laser (SL). By proper system configuration, UWB monocycle, doublet or triplet UWB signals can be generated after the balanced photodiode (BPD) detection. Besides, other modulation formats can also be realized, such as on-off keying (OOK) and pulse amplitude modulation (PAM) by properly modulating the ML optical pulses. Finally, fiber transmission of the modulated UWB signals is experimentally investigated, and it is shown that the UWB signals can be well maintained after 40 km optical fiber transmission.

  11. Nonlinear signal-based control with an error feedback action for nonlinear substructuring control

    Science.gov (United States)

    Enokida, Ryuta; Kajiwara, Koichi

    2017-01-01

    A nonlinear signal-based control (NSBC) method utilises the 'nonlinear signal' that is obtained from the outputs of a controlled system and its linear model under the same input signal. Although this method has been examined in numerical simulations of nonlinear systems, its application in physical experiments has not been studied. In this paper, we study an application of NSBC in physical experiments and incorporate an error feedback action into the method to minimise the error and enhance the feasibility in practice. Focusing on NSBC in substructure testing methods, we propose nonlinear substructuring control (NLSC), that is a more general form of linear substructuring control (LSC) developed for dynamical substructured systems. In this study, we experimentally and numerically verified the proposed NLSC via substructuring tests on a rubber bearing used in base-isolated structures. In the examinations, NLSC succeeded in gaining accurate results despite significant nonlinear hysteresis and unknown parameters in the substructures. The nonlinear signal feedback action in NLSC was found to be notably effective in minimising the error caused by nonlinearity or unknown properties in the controlled system. In addition, the error feedback action in NLSC was found to be essential for maintaining stability. A stability analysis based on the Nyquist criterion, which is used particularly for linear systems, was also found to be efficient for predicting the instability conditions of substructuring tests with NLSC and useful for the error feedback controller design.

  12. Coherent signal processing in optical coherence tomography

    Science.gov (United States)

    Kulkarni, Manish Dinkarrao

    1999-09-01

    Optical coherence tomography (OCT) is a novel method for non-invasive sub-surface imaging of biological tissue micro-structures. OCT achieves high spatial resolution ( ~ 15 m m in three dimensions) using a fiber-optically integrated system which is suitable for application in minimally invasive diagnostics, including endoscopy. OCT uses an optical heterodyne detection technique based on white light interferometry. Therefore extremely faint reflections ( ~ 10 fW) are routinely detected with high spatial localization. The goal of this thesis is twofold. The first is to present a theoretical model for describing image formation in OCT, and attempt to enhance the current level of understanding of this new modality. The second objective is to present signal processing methods for improving OCT image quality. We present deconvolution algorithms to obtain improved longitudinal resolution in OCT. This technique may be implemented without increasing system complexity as compared to current clinical OCT systems. Since the spectrum of the light backscattered from bio-scatterers is closely associated with ultrastructural variations in tissue, we propose a new technique for measuring spectra as a function of depth. This advance may assist OCT in differentiating various tissue types and detecting abnormalities within a tissue. In addition to depth resolved spectroscopy, Doppler processing of OCT signals can also improve OCT image contrast. We present a new technique, termed color Doppler OCT (CDOCT). It is an innovative extension of OCT for performing spatially localized optical Doppler velocimetry. Micron-resolution imaging of blood flow in sub-surface vessels in living tissue using CDOCT is demonstrated. The fundamental issues regarding the trade- off between the velocity estimation precision and image acquisition rate are presented. We also present novel algorithms for high accuracy velocity estimation. In many blood vessels velocities tend to be on the order of a few cm

  13. Optical signal monitoring in phase modulated optical fiber transmission systems

    Science.gov (United States)

    Zhao, Jian

    Optical performance monitoring (OPM) is one of the essential functions for future high speed optical networks. Among the parameters to be monitored, chromatic dispersion (CD) is especially important since it has a significant impact on overall system performance. In this thesis effective CD monitoring approaches for phase-shift keying (PSK) based optical transmission systems are investigated. A number of monitoring schemes based on radio frequency (RF) spectrum analysis and delay-tap sampling are proposed and their performance evaluated. A method for dispersion monitoring of differential phase-shift keying (DPSK) signals based on RF power detection is studied. The RF power spectrum is found to increase with the increase of CD and decrease with polarization mode dispersion (PMD). The spectral power density dependence on CD is studied theoretically and then verified through simulations and experiments. The monitoring sensitivity for nonreturn-to-zero differential phase-shift keying (NRZ-DPSK) and return-to-zero differential phase-shift keying (RZ-DPSK) based systems can reach 80ps/nm/dB and 34ps/nm/dB respectively. The scheme enables the monitoring of differential group delay (DGD) and CD simultaneously. The monitoring sensitivity of CD and DGD can reach 56.7ps/nm/dB and 3.1ps/dB using a bandpass filter. The effects of optical signal-to-noise ratio (OSNR), DGD, fiber nonlinearity and chirp on the monitoring results are investigated. Two RF pilot tones are employed for CD monitoring of DPSK signals. Specially selected pilot tone frequencies enable good monitoring sensitivity with minimum influence on the received signals. The dynamic range exceeding 35dB and monitoring sensitivity up to 9.5ps/nm/dB are achieved. Asynchronous sampling technique is employed for CD monitoring. A signed CD monitoring method for 10Gb/s NRZ-DPSK and RZ-DPSK systems using asynchronous delay-tap sampling technique is studied. The demodulated signals suffer asymmetric waveform distortion if

  14. Quantum optical signal processing in diamond

    CERN Document Server

    Fisher, Kent A G; Maclean, Jean-Phillipe W; Bustard, Philip J; Resch, Kevin J; Sussman, Benjamin J

    2015-01-01

    Controlling the properties of single photons is essential for a wide array of emerging optical quantum technologies spanning quantum sensing, quantum computing, and quantum communications. Essential components for these technologies include single photon sources, quantum memories, waveguides, and detectors. The ideal spectral operating parameters (wavelength and bandwidth) of these components are rarely similar; thus, frequency conversion and spectral control are key enabling steps for component hybridization. Here we perform signal processing of single photons by coherently manipulating their spectra via a modified quantum memory. We store 723.5 nm photons, with 4.1 nm bandwidth, in a room-temperature diamond crystal; upon retrieval we demonstrate centre frequency tunability over 4.2 times the input bandwidth, and bandwidth modulation between 0.5 to 1.9 times the input bandwidth. Our results demonstrate the potential for diamond, and Raman memories in general, to be an integrated platform for photon storage ...

  15. Spatio-temporal dynamcis of a cell signal cascade with negative feedback

    Science.gov (United States)

    Maya Bernal, Jose Luis; Ramirez-Santiago, Guillermo

    2014-03-01

    We studied the spatio-temporal dynamics of a system of reactio-diffusion equations that models a cell signal transduction pathway with six cycles and negative feedback. The basic cycle consists of the phosphorylation-dephosphorylation of two antagonic proteins. We found two regimes of saturation of the enzimatic reaction in the kinetic parameters space and determined the conditions for the signal propagation in the steady state. The trajectories for which transduction occurs are defined in terms of the ratio of the enzimatic activities. We found that in spite of the negative feedback the cell signal cascade behaves as an amplifier and produces phosphoprotein concentration gradients within the cell. This model behaves also as a noise filter and as a switch. Supported by DGAPA-UNAM Contract IN118410-3.

  16. Ultra-broadband and ultra-fast optical signal processing

    DEFF Research Database (Denmark)

    Oxenløwe, Leif Katsuo

    2015-01-01

    We have recently seen that nanowires can provide unparalleled optical signal processing (OSP) bandwidth and provide ultra-fast operation as well. Utilising the ultra-broad OSP bandwidth for e.g. optical time lenses allows for energy-efficient optical switching. © 2015 OSA.......We have recently seen that nanowires can provide unparalleled optical signal processing (OSP) bandwidth and provide ultra-fast operation as well. Utilising the ultra-broad OSP bandwidth for e.g. optical time lenses allows for energy-efficient optical switching. © 2015 OSA....

  17. Microwave oscillator with reduced phase noise by negative feedback incorporating microwave signals with suppressed carrier

    Science.gov (United States)

    Dick, G. J.; Saunders, J.

    1989-01-01

    Oscillator configurations which reduce the effect of 1/f noise sources for both direct feedback and stabilized local oscillator (STALO) circuits are developed and analyzed. By appropriate use of carrier suppression, a small signal is generated which suffers no loss of loop phase information or signal-to-noise ratio. This small signal can be amplified without degradation by multiplicative amplifier noise, and can be detected without saturation of the detector. Together with recent advances in microwave resonator Qs, these circuit improvements will make possible lower phase noise than can be presently achieved without the use of cryogenic devices.

  18. Real-time wavefront-shaping through scattering media by all optical feedback

    CERN Document Server

    Nixon, Micha; Small, Eran; Bromberg, Yaron; Friesem, Asher A; Silberberg, Yaron; Davidson, Nir

    2013-01-01

    Focusing light through dynamically varying heterogeneous media is a sought-after goal with important applications ranging from free-space communication to nano-surgery. The underlying challenge is to control the optical wavefront with a large number of degrees-of-freedom (DOF) at timescales shorter than the medium dynamics. Recently, many advancements have been reported following the demonstration of focusing through turbid samples by wavefront-shaping, using spatial light modulators (SLMs) having >1000 DOF. Unfortunately, SLM-based wavefront-shaping requires feedback from a detector/camera and is limited to slowly-varying samples. Here, we demonstrate a novel approach for wavefront-shaping using all-optical feedback. We show that the complex wavefront required to focus through highly scattering samples, including thin biological tissues, can be generated at sub-microsecond timescales by the process of field self-organization inside a multimode laser cavity, without requiring electronic feedback or SLMs. This...

  19. Ultra-high-speed optical signal processing of Tbaud data signals

    DEFF Research Database (Denmark)

    Oxenløwe, Leif Katsuo; Galili, Michael; Mulvad, Hans Christian Hansen;

    2010-01-01

    We describe methods to generate and optically signal process Tbaud serial optical data signals. We present sub-systems making serial optical Tbit/s systems compatible with standard Ethernet data for data centre applications, and present Tbit/s results using a.o. silicon nanowires....

  20. Degradation Processes in High-Power Diode Lasers under External Optical Feedback

    DEFF Research Database (Denmark)

    Tomm, Jens. W.; Hempel, Martin; Petersen, Paul Michael;

    2013-01-01

    The effect of moderate external feedback on the gradual degradation of 808 nm emitting AlGaAs-based high-power broad-area diode lasers is analyzed. Eventually the quantum well that actually experiences the highest total optical load remains unaffected by the aging, while severe impact...

  1. Bistability and low-frequency fluctuations in semiconductor lasers with optical feedback: a theoretical analysis

    DEFF Research Database (Denmark)

    Mørk, Jesper; Tromborg, Bjarne; Christiansen, Peter Leth

    1988-01-01

    Near-threshold operation of a semiconductor laser exposed to moderate optical feedback may lead to low-frequency fluctuations. In the same region, a kink is observed in the light-current characteristic. Here it is demonstrated that these nonlinear phenomena are predicted by a noise driven multimode...

  2. Linewidth broadening in a distributed feedback laser integrated with a semiconductor optical amplifier

    DEFF Research Database (Denmark)

    Champagne, A.; Camel, J.; Maciejko, R.

    2002-01-01

    The problem of the linewidth degradation in systems using distributed-feedback lasers together with strained-layer multi-quantum-well semiconductor optical amplifiers (SOAs) is examined. A modified expression for the linewidth in the case of antireflection-coated SOA output facets is derived...

  3. All-optical signal processing data communication and storage applications

    CERN Document Server

    Eggleton, Benjamin

    2015-01-01

    This book provides a comprehensive review of the state-of-the art of optical signal processing technologies and devices. It presents breakthrough solutions for enabling a pervasive use of optics in data communication and signal storage applications. It presents presents optical signal processing as solution to overcome the capacity crunch in communication networks. The book content ranges from the development of innovative materials and devices, such as graphene and slow light structures, to the use of nonlinear optics for secure quantum information processing and overcoming the classical Shannon limit on channel capacity and microwave signal processing. Although it holds the promise for a substantial speed improvement, today’s communication infrastructure optics remains largely confined to the signal transport layer, as it lags behind electronics as far as signal processing is concerned. This situation will change in the near future as the tremendous growth of data traffic requires energy efficient and ful...

  4. Controlling traffic jams on a two-lane road using delayed-feedback signals

    Institute of Scientific and Technical Information of China (English)

    Liang ZHENG; Shi-quan ZHONG; Shou-feng MA

    2012-01-01

    This paper focuses mainly on the stability analysis of two-lane traffic flow with lateral friction,which may be caused by irregular driving behavior or poorly visible road markings,and also attempts to reveal the formation mechanism of traffic jams.Firstly,a two-lane optimal velocity (OV) model without control signals is proposed and its stability condition is obtained from the viewpoint of control theory.Then delayed-feedback control signals composed of distance headway information from both lanes are added to each vehicle and a vehicular control system is designed to suppress the traffic jams.Lane change behaviors are also incorporated into the two-lane OV model and the corresponding information about distance headway and feedback signals is revised.Finally,the results of numerical experiments are shown to verify that when the stability condition is not met,the position disturbances and resulting lane change behaviors do indeed deteriorate traffic performance and cause serious traffic jams.However,once the proper delayed-feedback control signals are implemented,the traffic jams can be suppressed efficiently.

  5. Recent Advances in Ultra-High-Speed Optical Signal Processing

    DEFF Research Database (Denmark)

    Mulvad, Hans Christian Hansen; Palushani, Evarist; Hu, Hao;

    2012-01-01

    We review recent advances in the optical signal processing of ultra-high-speed serial data signals up to 1.28 Tbit/s, with focus on applications of time-domain optical Fourier transformation. Experimental methods for the generation of symbol rates up to 1.28 Tbaud are also described....

  6. Ultra-Fast Optical Signal Processing in Nonlinear Silicon Waveguides

    DEFF Research Database (Denmark)

    Oxenløwe, Leif Katsuo; Galili, Michael; Pu, Minhao;

    2011-01-01

    We describe recent demonstrations of exploiting highly nonlinear silicon nanowires for processing Tbit/s optical data signals. We perform demultiplexing and optical waveform sampling of 1.28 Tbit/s and wavelength conversion of 640 Gbit/s data signals....

  7. A novel approach for generating flat optical frequency comb based on externally injected gain-switching distributed feedback semiconductor laser

    Science.gov (United States)

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

    2017-02-01

    In this paper, a novel approach for generating flat optical frequency comb (OFC) based on externally injected gain-switched distributed feedback (DFB) semiconductor laser is proposed and experimentally demonstrated. In the proposed system, the flatness, the number of OFC spectral lines, and the spectral line to background noise ratio can be tuned to their optimized values by adjusting the current of the modulation signal, the injection ratio and the detuning frequency. Since the frequency of the modulation signal decides the frequency spacing of the output spectral lines, OFC spectral lines of different spacing can be achieved. In the experiment, 10 spectral lines with 1.5 dB power variation are demonstrated to verify the proposed approach. In addition, the expansion of the spectral line is investigated.

  8. Improved optical packet switching structure with recirculation buffer and feedback tunable wavelength converter

    Institute of Scientific and Technical Information of China (English)

    Cheng Wu; Shilin Xiao

    2009-01-01

    The performance of an optical switching network is mainly determined by its core node structure.An improved optical packet switching(OPS)node structure based on recirculation optical fiber delay line(FDL)and feedback tunable wavelength converter(TWC),and a specific scheduling algorithm for the node structure are presented.This switching structure supports both point-to-point and point-to-multi-points broadcasting transmission with superior capacity expansion performance.Its superiority in packet loss probability is proved by simulation.

  9. Simulation of chaotic synchronization communication system based on incoherent optical feedback and injection

    Institute of Scientific and Technical Information of China (English)

    MA Jun-shan; GU Wen-hua

    2006-01-01

    In this paper,we numerically study chaotic synchronization communication system based on incoherent optical feedback and incoherent optical injection.The characteristics of the system,such as synchronization time,synchronization error,chaos shift keying encoding/decoding and modulation rate are analyzed.The results of simulation show that the system has good synchronization quality and good abilities of robust secure.The synchronization time is 1ns and the chaos shift keying encoding can reach a high rate of 1 Gbit/s.The system has a good ability of robust secure.It proves the feasibility of the optical secure communication.

  10. High-speed signal processing using highly nonlinear optical fibres

    DEFF Research Database (Denmark)

    Peucheret, Christophe; Oxenløwe, Leif Katsuo; Mulvad, Hans Christian Hansen

    2009-01-01

    relying on the phase of the optical field. Topics covered include all-optical switching of 640 Gbit/s and 1.28 Tbit/s serial data, wavelength conversion at 640 Gbit/s, optical amplitude regeneration of differential phase shift keying (DPSK) signals, as well as midspan spectral inversion for differential 8......We review recent progress in all-optical signal processing techniques making use of conventional silica-based highly nonlinear fibres. In particular, we focus on recent demonstrations of ultra-fast processing at 640 Gbit/s and above, as well as on signal processing of novel modulation formats...

  11. Inner structure detection by optical tomography technology based on feedback of microchip Nd:YAG lasers.

    Science.gov (United States)

    Xu, Chunxin; Zhang, Shulian; Tan, Yidong; Zhao, Shijie

    2013-05-20

    We describe a new optical tomography technology based on feedback of microchip Nd:YAG lasers. In the case of feedback light frequency-shifted, light can be magnified by a fact of 10(6) in the Nd:YAG microchip lasers, which makes it possible to realize optical tomography with a greater depth than current optical tomography. The results of the measuring and imaging of kinds of samples are presented, which demonstrate the feasibility and potential of this approach in the inner structure detection. The system has a lateral resolution of ~1 μm, a vertical resolution of 15 μm and a longitudinal scanning range of over 10mm.

  12. Effects of speed bottleneck on traffic flow with feedback control signal

    Science.gov (United States)

    Zhu, Kangli; Bi, Jiantao; Wu, Jianjun; Li, Shubin

    2016-09-01

    Various car-following models (CMs) have been developed to capture the complex characteristics of microscopic traffic flow, among which the coupled map CM can better reveal and reflect various phenomena of practical traffic flow. Capacity change at bottleneck contributes to high-density traffic flow upstream the bottleneck and contains very complex dynamic behavior. In this paper, we analyze the effect of speed bottleneck on the spatial-temporal evolution characteristics of traffic flow, and propose a method to reduce traffic congestion with the feedback control signal based on CM. Simulation results highlight the potential of using the feedback signal to control the stop-and-go wave and furthermore to alleviate the traffic congestion effectively.

  13. Neuromorphic opto-electronic integrated circuits for optical signal processing

    Science.gov (United States)

    Romeira, B.; Javaloyes, J.; Balle, S.; Piro, O.; Avó, R.; Figueiredo, J. M. L.

    2014-08-01

    The ability to produce narrow optical pulses has been extensively investigated in laser systems with promising applications in photonics such as clock recovery, pulse reshaping, and recently in photonics artificial neural networks using spiking signal processing. Here, we investigate a neuromorphic opto-electronic integrated circuit (NOEIC) comprising a semiconductor laser driven by a resonant tunneling diode (RTD) photo-detector operating at telecommunication (1550 nm) wavelengths capable of excitable spiking signal generation in response to optical and electrical control signals. The RTD-NOEIC mimics biologically inspired neuronal phenomena and possesses high-speed response and potential for monolithic integration for optical signal processing applications.

  14. An insulin signaling feedback loop regulates pancreas progenitor cell differentiation during islet development and regeneration.

    Science.gov (United States)

    Ye, Lihua; Robertson, Morgan A; Mastracci, Teresa L; Anderson, Ryan M

    2016-01-15

    As one of the key nutrient sensors, insulin signaling plays an important role in integrating environmental energy cues with organism growth. In adult organisms, relative insufficiency of insulin signaling induces compensatory expansion of insulin-secreting pancreatic beta (β) cells. However, little is known about how insulin signaling feedback might influence neogenesis of β cells during embryonic development. Using genetic approaches and a unique cell transplantation system in developing zebrafish, we have uncovered a novel role for insulin signaling in the negative regulation of pancreatic progenitor cell differentiation. Blocking insulin signaling in the pancreatic progenitors hastened the expression of the essential β cell genes insulin and pdx1, and promoted β cell fate at the expense of alpha cell fate. In addition, loss of insulin signaling promoted β cell regeneration and destabilization of alpha cell character. These data indicate that insulin signaling constitutes a tunable mechanism for β cell compensatory plasticity during early development. Moreover, using a novel blastomere-to-larva transplantation strategy, we found that loss of insulin signaling in endoderm-committed blastomeres drove their differentiation into β cells. Furthermore, the extent of this differentiation was dependent on the function of the β cell mass in the host. Altogether, our results indicate that modulation of insulin signaling will be crucial for the development of β cell restoration therapies for diabetics; further clarification of the mechanisms of insulin signaling in β cell progenitors will reveal therapeutic targets for both in vivo and in vitro β cell generation.

  15. All Optical Signal-Processing Techniques Utilizing Four Wave Mixing

    Directory of Open Access Journals (Sweden)

    Refat Kibria

    2015-02-01

    Full Text Available Four Wave Mixing (FWM based optical signal-processing techniques are reviewed. The use of FWM in arithmetical operation like subtraction, wavelength conversion and pattern recognition are three key parts discussed in this paper after a brief introduction on FWM and its comparison with other nonlinear mixings. Two different approaches to achieve correlation are discussed, as well as a novel technique to realize all optical subtraction of two optical signals.

  16. All-optical signal processing using dynamic Brillouin gratings

    Science.gov (United States)

    Santagiustina, Marco; Chin, Sanghoon; Primerov, Nicolay; Ursini, Leonora; Thévenaz, Luc

    2013-01-01

    The manipulation of dynamic Brillouin gratings in optical fibers is demonstrated to be an extremely flexible technique to achieve, with a single experimental setup, several all-optical signal processing functions. In particular, all-optical time differentiation, time integration and true time reversal are theoretically predicted, and then numerically and experimentally demonstrated. The technique can be exploited to process both photonic and ultra-wide band microwave signals, so enabling many applications in photonics and in radio science. PMID:23549159

  17. A Self-regulatory System of Interlinked Signaling Feedback Loops Controls Mouse Limb Patterning

    Science.gov (United States)

    Benazet, Jean-Denis; Bischofberger, Mirko; Tiecke, Eva; Gonalves, Alexandre; Martin, James F.; Zuniga, Aime; Naef, Felix; Zeller, Rolf

    Developmental pathways need to be robust against environmental and genetic variation to enable reliable morphogenesis. Here, we take a systems biology approach to explain how robustness is achieved in the developing mouse limb, a classical model of organogenesis. By combining quantitative genetics with computational modeling we established a computational model of multiple interlocked feedback modules, involving sonic hedgehog (SHH) morphogen, fibroblast growth factor (FGFs) signaling, bone morphogenetic protein (BMP) and its antagonist GREM1. Earlier modeling work had emphasized the versatile kinetic characteristics of interlocked feedback loops operating at different time scales. Here we develop and then validate a similar computational model to show how BMP4 first initiates and SHH then propagates feedback in the network through differential transcriptional regulation of Grem1 to control digit specification. This switch occurs by linking a fast BMP4/GREM1 module to a slower SHH/GREM1/FGF feedback loop. Simulated gene expression profiles modeled normal limb development as well those of single-gene knockouts. Sensitivity analysis showed how the model was robust and insensitive to variability in parameters. A surprising prediction of the model was that an early Bmp4 signal is essential to kick-start Grem1 expression and the digit specification system. We experimentally validated the prediction using inducible alleles and showed that early, but not late, removal of Bmp4 dramatically disrupted limb development. Sensitivity analysis showed how robustness emerges from this circuitry. This study shows how modeling and computation can help us understand how self-regulatory signaling networks achieve robust regulation of limb development, by exploiting interconnectivity among the three signaling pathways. We expect that similar computational analyses will shed light on the origins of robustness in other developmental systems, and I will discuss some recent examples from

  18. Designing a Signal Conditioning System with Software Calibration for Resistor-feedback Patch Clamp Amplifier.

    Science.gov (United States)

    Hu, Gang; Zhu, Quanhui; Qu, Anlian

    2005-01-01

    In this paper, a programmable signal conditioning system based on software calibration for resistor-feedback patch clamp amplifier (PCA) has been described, this system is mainly composed of frequency correction, programmable gain and filter whose parameters are configured by software automatically to minimize the errors, A lab-designed data acquisition system (DAQ) is used to implement data collections and communications with PC. The laboratory test results show good agreement with design specifications.

  19. Integrated packaging of 2D MOEMS mirrors with optical position feedback

    Science.gov (United States)

    Baumgart, M.; Lenzhofer, M.; Kremer, M. P.; Tortschanoff, A.

    2015-02-01

    Many applications of MOEMS microscanners rely on accurate position feedback. For MOEMS devices which do not have intrinsic on-chip feedback, position information can be provided with optical methods, most simply by using a reflection from the backside of a MOEMS scanner. By measuring the intensity distribution of the reflected beam across a quadrant diode, one can precisely detect the mirror's deflection angles. Previously, we have presented a position sensing device, applicable to arbitrary trajectories, which is based on the measurement of the position of the reflected laser beam with a quadrant diode. In this work, we present a novel setup, which comprises the optical position feedback functionality integrated into the device package itself. The new device's System-in-Package (SiP) design is based on a flip-folded 2.5D PCB layout and fully assembled as small as 9.2×7×4 mm³ in total. The device consists of four layers, which supply the MOEMS mirror, a spacer to provide the required optical path length, the quadrant photo-diode and a laser diode to serve as the light source. In addition to describing the mechanical setup of the novel device, we will present first experimental results and optical simulation studies. Accurate position feedback is the basis for closed-loop control of the MOEMS devices, which is crucial for some applications as image projection for example. Position feedback and the possibility of closed-loop control will significantly improve the performance of these devices.

  20. Micromachined force-balance feedback accelerometer with optical displacement detection

    Science.gov (United States)

    Nielson, Gregory N.; Langlois, Eric; Baker, Michael; Okandan, Murat; Anderson, Robert

    2014-07-22

    An accelerometer includes a proof mass and a frame that are formed in a handle layer of a silicon-on-an-insulator (SOI). The proof mass is separated from the frame by a back-side trench that defines a boundary of the proof mass. The accelerometer also includes a reflector coupled to a top surface of the proof mass. An optical detector is located above the reflector at the device side. The accelerometer further includes at least one suspension spring. The suspension spring has a handle anchor that extends downwards from the device side to the handle layer to mechanically support upward and downward movement of the proof mass relative to a top surface of the proof mass.

  1. Photonic Applications Using Electrooptic Optical Signal Processors

    Science.gov (United States)

    2011-11-16

    DPMZM transmitter, the laser source of 1550nm, the erbium-doped fiber amplifier ( EDFA ), the local oscillator (LO), and the optical filter (FBG). The LO...is generated using an optical modulator, operating at 12.25278 GHz along with an optical filter (FBG) to separate the sideband. The EDFA was used to

  2. Coherent detection and digital signal processing for fiber optic communications

    Science.gov (United States)

    Ip, Ezra

    The drive towards higher spectral efficiency in optical fiber systems has generated renewed interest in coherent detection. We review different detection methods, including noncoherent, differentially coherent, and coherent detection, as well as hybrid detection methods. We compare the modulation methods that are enabled and their respective performances in a linear regime. An important system parameter is the number of degrees of freedom (DOF) utilized in transmission. Polarization-multiplexed quadrature-amplitude modulation maximizes spectral efficiency and power efficiency as it uses all four available DOF contained in the two field quadratures in the two polarizations. Dual-polarization homodyne or heterodyne downconversion are linear processes that can fully recover the received signal field in these four DOF. When downconverted signals are sampled at the Nyquist rate, compensation of transmission impairments can be performed using digital signal processing (DSP). Software based receivers benefit from the robustness of DSP, flexibility in design, and ease of adaptation to time-varying channels. Linear impairments, including chromatic dispersion (CD) and polarization-mode dispersion (PMD), can be compensated quasi-exactly using finite impulse response filters. In practical systems, sampling the received signal at 3/2 times the symbol rate is sufficient to enable an arbitrary amount of CD and PMD to be compensated for a sufficiently long equalizer whose tap length scales linearly with transmission distance. Depending on the transmitted constellation and the target bit error rate, the analog-to-digital converter (ADC) should have around 5 to 6 bits of resolution. Digital coherent receivers are naturally suited for the implementation of feedforward carrier recovery, which has superior linewidth tolerance than phase-locked loops, and does not suffer from feedback delay constraints. Differential bit encoding can be used to prevent catastrophic receiver failure due

  3. Remote Synchronization Experiments for Quasi-Zenith Satellite System Using Multiple Navigation Signals as Feedback Control

    Directory of Open Access Journals (Sweden)

    Toshiaki Iwata

    2011-01-01

    Full Text Available The remote synchronization system for the onboard crystal oscillator (RESSOX is a remote control method that permits synchronization between a ground station atomic clock and Japanese quasi-zenith satellite system (QZSS crystal oscillators. To realize the RESSOX of the QZSS, the utilization of navigation signals of QZSS for feedback control is an important issue. Since QZSS transmits seven navigation signals (L1C/A, L1CP, L1CD, L2CM, L2CL, L5Q, and L5I, all combinations of these signals should be evaluated. First, the RESSOX algorithm will be introduced. Next, experimental performance will be demonstrated. If only a single signal is available, ionospheric delay should be input from external measurements. If multiple frequency signals are available, any combination, except for L2 and L5, gives good performance with synchronization error being within two nanoseconds that of RESSOX. The combination of L1CD and L5Q gives the best synchronization performance (synchronization error within 1.14 ns. Finally, in the discussion, comparisons of long-duration performance, computer simulation, and sampling number used in feedback control are considered. Although experimental results do not correspond to the simulation results, the tendencies are similar. For the overlapping Allan deviation of long duration, the stability of 1.23×10−14 at 100,160 s is obtained.

  4. Encoding an Optical Signal using a Wireless Radio-Freqency Signal

    DEFF Research Database (Denmark)

    2011-01-01

    Source: US2012148252A The present invention provides a method for modulating an optical signal in a semiconductor device. A wireless radio frequency modulation signal is used to provide a time-dependent electric field in a semiconductor nanostructure region, which causes a change in the absorption...... in the semiconductor device. An optical signal propagating in the semiconductor device will be modulated in accordance with the properties of the wireless radio frequency modulation signal, thus providing a method for encoding information from a wireless radio frequency signal onto an optical carrier....

  5. A new output feedback synchronization theorem for a class of chaotic systems with a scalar transmitted signal

    Institute of Scientific and Technical Information of China (English)

    Lu Jun-Guo

    2006-01-01

    This paper proposes a new, simple and yet applicable output feedback synchronization theorem for a large class of chaotic systems. We take a linear combination of drive system state variables as a scale-driving signal. It is proved that synchronization between the drive and the response systems can be obtained via a simple linear output error feedback control. The linear feedback gain is a function of a free parameter. The approach is illustrated using the Rossler hyperchaotic systems and Chua's chaotic oscillators.

  6. Advanced Optical Signal Processing using Time Lens based Optical Fourier Transformation

    DEFF Research Database (Denmark)

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

    2016-01-01

    An overview of recent progress on time lens based advanced optical signal processing is presented, with a special focus on all-optical ultrafast 640 Gbit/s all-channel serial-to-parallel conversion, and scalable WDM regeneration....

  7. Immune signal transduction in leishmaniasis from natural to artificial systems: role of feedback loop insertion.

    Science.gov (United States)

    Mol, Milsee; Patole, Milind S; Singh, Shailza

    2014-01-01

    Modulated immune signal (CD14-TLR and TNF) in leishmaniasis can be linked to EGFR pathway involved in wound healing, through crosstalk points. This signaling network can be further linked to a synthetic gene circuit acting as a positive feedback loop to elicit a synchronized intercellular communication among the immune cells which may contribute to a better understanding of signaling dynamics in leishmaniasis. Network reconstruction with positive feedback loop, simulation (ODE 15s solver) and sensitivity analysis of CD14-TLR, TNF and EGFR was done in SimBiology (MATLAB 7.11.1). Cytoscape and adjacency matrix were used to calculate network topology. PCA was extracted by using sensitivity coefficient in MATLAB. Model reduction was done using time, flux and sensitivity score. Network has five crosstalk points: NIK, IκB-NFκB and MKK (4/7, 3/6, 1/2) which show high flux and sensitivity. PI3K in EGFR pathway shows high flux and sensitivity. PCA score was high for cytoplasmic ERK1/2, PI3K, Atk, STAT1/3 and nuclear JNK. Of the 125 parameters, 20% are crucial as deduced by model reduction. EGFR can be linked to CD14-TLR and TNF through the MAPK crosstalk points. These pathways may be controlled through Ras and Raf that lie upstream of signaling components ERK ½ (c) and JNK (n) that have a high PCA score via a synthetic gene circuit for activating cell-cell communication to elicit an inflammatory response. Also a disease resolving effect may be achieved through PI3K in the EGFR pathway. The reconstructed signaling network can be linked to a gene circuit with a positive feedback loop, for cell-cell communication resulting in synchronized response in the immune cell population, for disease resolving effect in leishmaniasis. © 2013 Elsevier B.V. All rights reserved.

  8. Simulation of neurocomputing based on the photophobic reactions of Euglena with optical feedback stimulation.

    Science.gov (United States)

    Ozasa, Kazunari; Aono, Masashi; Maeda, Mizuo; Hara, Masahiko

    2010-05-01

    To explore possible forms of unconventional computers that have high capacities for adaptation and exploration, we propose a new approach to developing a biocomputer based on the photophobic reactions of microbes (Euglena gracilis), and perform the Monte-Carlo simulation of Euglena-based neural network computing, involving virtual optical feedback to the Euglena cells. The photophobic reactions of Euglena are obtained experimentally, and incorporated in the simulation, together with a feedback algorithm with a modified Hopfield-Tank model for solving a 4-city traveling salesman problem. The simulation shows high performances in terms of (1) reaching one of the best solutions of the problem, and (2) searching for a number of solutions via dynamic transition among the solutions. This dynamic transition is attributed to the fluctuation of state variables, global oscillation through feedback instability, and the one-by-one change of state variables.

  9. Optical Frequency Upconversion Technique for Transmission of Wireless MIMO-Type Signals over Optical Fiber

    OpenAIRE

    R. Q. Shaddad; Mohammad, A. B.; S. A. Al-Gailani; Al-Hetar, A. M.

    2014-01-01

    The optical fiber is well adapted to pass multiple wireless signals having different carrier frequencies by using radio-over-fiber (ROF) technique. However, multiple wireless signals which have the same carrier frequency cannot propagate over a single optical fiber, such as wireless multi-input multi-output (MIMO) signals feeding multiple antennas in the fiber wireless (FiWi) system. A novel optical frequency upconversion (OFU) technique is proposed to solve this problem. In this paper, the n...

  10. Micro-RNA Feedback Loops Modulating the Calcineurin/NFAT Signaling Pathway

    Directory of Open Access Journals (Sweden)

    Shichina Kannambath

    2016-05-01

    Full Text Available Nuclear factor of activated T cells (NFAT is a family of transcription factors important for innate and adaptive immune responses. NFAT activation is tightly regulated through the calcineurin/NFAT signaling pathway. There is increasing evidence on non-coding RNAs such as miRNAs playing a crucial role in regulating transcription factors and signaling pathways. However, not much is known about microRNAs (miRNAs targeting the calcineurin/NFAT signaling pathway involved in immune response in human. In this study, a comprehensive pathway level analysis has been carried out to identify miRNAs regulating the calcineurin/NFAT signaling pathway. Firstly, by incorporating experimental data and computational predictions, 191 unique miRNAs were identified to be targeting the calcineurin/NFAT signaling pathway in humans. Secondly, combining miRNA expression data from activated T cells and computational predictions, 32 miRNAs were observed to be induced by NFAT transcription factors. Finally, 11 miRNAs were identified to be involved in a feedback loop to modulate the calcineurin/NFAT signaling pathway activity. This data demonstrate the potential role of miRNAs as regulators of the calcineurin/NFAT signaling pathway. The present study thus emphasizes the importance of pathway level analysis to identify miRNAs and understands their role in modulating signaling pathways and transcription factor activity.

  11. All-optical WDM Regeneration of DPSK Signals using Optical Fourier Transformation and Phase Sensitive Amplification

    DEFF Research Database (Denmark)

    Guan, Pengyu; Røge, Kasper Meldgaard; Kjøller, Niels-Kristian;

    2015-01-01

    We propose a novel all-optical WDM regeneration scheme for DPSK signals based on optical Fourier transformation and phase sensitive amplification. Phase regeneration of a WDM signal consisting of 4x10-Gbit/s phase noise degraded DPSK channels is demonstrated for the first time.......We propose a novel all-optical WDM regeneration scheme for DPSK signals based on optical Fourier transformation and phase sensitive amplification. Phase regeneration of a WDM signal consisting of 4x10-Gbit/s phase noise degraded DPSK channels is demonstrated for the first time....

  12. Feedback-induced Bistability of an Optically Levitated Nanoparticle: A Fokker-Planck Treatment

    CERN Document Server

    Ge, Wenchao; Bhattacharya, M

    2016-01-01

    Optically levitated nanoparticles have recently emerged as versatile platforms for investigating macroscopic quantum mechanics and enabling ultrasensitive metrology. In this article we theoretically consider two damping regimes of an optically levitated nanoparticle cooled by cavityless parametric feedback. Our treatment is based on a generalized Fokker-Planck equation derived from the quantum master equation presented recently and shown to agree very well with experiment [1]. For low damping, we find that the resulting Wigner function yields the single-peaked oscillator position distribution and recovers the appropriate energy distribution derived earlier using a classical theory and verified experimentally [2]. For high damping, in contrast, we predict a double-peaked position distribution, which we trace to an underlying bistability induced by feedback. Unlike in cavity-based optomechanics, stochastic processes play a major role in determining the bistable behavior. To support our conclusions, we present a...

  13. Ultra-high-speed optical signal processing of serial data signals

    DEFF Research Database (Denmark)

    Clausen, Anders; Mulvad, Hans Christian Hansen; Palushani, Evarist;

    2012-01-01

    To ensure that ultra high-speed serial data signals can be utilised in future optical communication networks, it is indispensable to have all-optical signal processing elements at our disposal. In this paper, the most recent advances in our use of non-linear materials incorporated in different...

  14. System and Method for Multi-Wavelength Optical Signal Detection

    Science.gov (United States)

    McGlone, Thomas D. (Inventor)

    2017-01-01

    The system and method for multi-wavelength optical signal detection enables the detection of optical signal levels significantly below those processed at the discrete circuit level by the use of mixed-signal processing methods implemented with integrated circuit technologies. The present invention is configured to detect and process small signals, which enables the reduction of the optical power required to stimulate detection networks, and lowers the required laser power to make specific measurements. The present invention provides an adaptation of active pixel networks combined with mixed-signal processing methods to provide an integer representation of the received signal as an output. The present invention also provides multi-wavelength laser detection circuits for use in various systems, such as a differential absorption light detection and ranging system.

  15. Multimode distributed feedback laser emission in a dye-doped optically pumped polymer thin-film

    Science.gov (United States)

    Sobel, F.; Gindre, D.; Nunzi, J.-M.; Denis, C.; Dumarcher, V.; Fiorini-Debuisschert, C.; Kretsch, K. P.; Rocha, L.

    2004-11-01

    We report on particular features of thin film distributed feedback (DFB) lasers. Devices are optically pumped using a Lloyd-mirror interferometer. For a given DFB grating period, the number of lasing modes is film thickness dependent. Spectral content of the devices is analysed using planar waveguide theory. An excellent agreement between the theoretical transverse electric mode structure and the laser emission spectrum is found.

  16. Noise-Induced Phase Locking and Frequency Mixing in an Optical Bistable System with Delayed Feedback

    Science.gov (United States)

    Misono, Masatoshi; Miyakawa, Kenji

    2011-11-01

    The interplay between stochastic resonance (SR) and coherence resonance (CR) is experimentally studied in an optical bistable system with a time-delayed feedback loop. We demonstrate that the phase of the noise-induced motion is locked to that of the periodic input when the ratio of their frequencies is a simple rational number. We also demonstrate that the interplay between SR and CR generates frequency-mixed modes, and that the efficiency of frequency mixing is enhanced by the optimum noise.

  17. Chaos synchronization in injection-locked semiconductor lasers with optical feedback

    Institute of Scientific and Technical Information of China (English)

    Liu Yu-Jin; Zhang Sheng-Hai; Qian Xing-Zhong

    2007-01-01

    Based on the rate equations, we have investigated three types of chaos synchronizations in injection-locked semiconductor lasers with optical feedback. Numerical simulation shows that the synchronization can be realized by the symmetric or asymmetric laser systems. Also, the influence of parameter mismatches on chaos synchronization is investigated, and the results imply that these two lasers can achieve good synchronization, with smaller tolerance of parameter mismatch existing.

  18. Optical signal processing by silicon photonics

    CERN Document Server

    Ahmed, Jameel; Adeel, Freeha; Hussain, Ashiq

    2014-01-01

    The main objective of this book is to make respective graduate students understand the nonlinear effects inside SOI waveguide and possible applications of SOI waveguides in this emerging research area of optical fibre communication. This book focuses on achieving successful optical frequency shifting by Four Wave Mixing (FWM) in silicon-on-insulator (SOI) waveguide by exploiting a nonlinear phenomenon.

  19. Passive intrinsic-linewidth narrowing of ultraviolet extended-cavity diode laser by weak optical feedback

    CERN Document Server

    Samutpraphoot, Polnop; Lin, Qian; Gangloff, Dorian; Bylinskii, Alexei; Braverman, Boris; Kawasaki, Akio; Raab, Christoph; Kaenders, Wilhelm; Vuletić, Vladan

    2014-01-01

    We present a simple method for narrowing the intrinsic Lorentzian linewidth of a commercial ultraviolet grating extended-cavity diode laser (TOPTICA DL Pro) using weak optical feedback from a long external cavity. We achieve a suppression in frequency noise spectral density of 20 dB measured at frequencies around 1 MHz, corresponding to the narrowing of the intrinsic Lorentzian linewidth from 200 kHz to 2 kHz. The system is suitable for experiments requiring a tunable ultraviolet laser with narrow linewidth and low high-frequency noise, such as precision spectroscopy, optical clocks, and quantum information science experiments.

  20. Four distributed feedback laser array integrated with multimode-interference and semiconductor optical amplifier

    Institute of Scientific and Technical Information of China (English)

    Ma Li; Zhu Hong-Liang; Liang Song; Zhao Ling-Juan; Chen Ming-Hua

    2013-01-01

    Monolithic integration of four 1.55-μm-range InGaAsP/InP distributed feedback (DFB) lasers using varied ridge width with a 4 × 1-multimode-interference (MMI) optical combiner and a semiconductor optical amplifier (SOA) is demonstrated.The average output power and the threshold current are 1.8 mW and 35 mA,respectively,when the injection current of the SOA is 100 mA,with a side mode suppression ratio (SMSR) exceeding 40 dB.The four channels have a 1-nm average channel spacing and can operate separately or simultaneously.

  1. Front-end signal analysis of the transverse feedback system for SSRF

    Institute of Scientific and Technical Information of China (English)

    HAN Lifeng; YUAN Renxian; YU Luyang; YE Kairong

    2008-01-01

    Multi-bunch instabilities degrade beam quality through increased beam emittance, energy spread and even cause beam loss. A feedback system is used to suppress multi-bunch instabilities associated with resistive wall of the beam ducts, cavity-like structures, and trapped ions. A digital TFS (Transverse Feedback System) is in construction at the SSRF (Shanghai Synchrotron Radiation Facility), which is based on the latest generation of FPGA (Field Programmable Gate Array) processor. Before we get such FPGA digital board, investigation and simulation of the front-end were done in the first place. The signal flow was analyzed by SystemView. Construction and optimization of the entire system is our next goal.

  2. Prickle mediates feedback amplification to generate asymmetric planar cell polarity signaling.

    Science.gov (United States)

    Tree, David R P; Shulman, Joshua M; Rousset, Raphaël; Scott, Matthew P; Gubb, David; Axelrod, Jeffrey D

    2002-05-03

    Planar cell polarity signaling in Drosophila requires the receptor Frizzled and the cytoplasmic proteins Dishevelled and Prickle. From initial, symmetric subcellular distributions in pupal wing cells, Frizzled and Dishevelled become highly enriched at the distal portion of the cell cortex. We describe a Prickle-dependent intercellular feedback loop that generates asymmetric Frizzled and Dishevelled localization. In the absence of Prickle, Frizzled and Dishevelled remain symmetrically distributed. Prickle localizes to the proximal side of pupal wing cells and binds the Dishevelled DEP domain, inhibiting Dishevelled membrane localization and antagonizing Frizzled accumulation. This activity is linked to Frizzled activity on the adjacent cell surface. Prickle therefore functions in a feedback loop that amplifies differences between Frizzled levels on adjacent cell surfaces.

  3. Feedback correction of injection errors using digital signal-processing techniques

    Directory of Open Access Journals (Sweden)

    N. S. Sereno

    2007-01-01

    Full Text Available Efficient transfer of electron beams from one accelerator to another is important for 3rd-generation light sources that operate using top-up. In top-up mode, a constant amount of charge is injected at regular intervals into the storage ring to replenish beam lost primarily due to Touschek scattering. Top-up therefore requires that the complex of injector accelerators that fill the storage ring transport beam with a minimum amount of loss. Injection can be a source of significant beam loss if not carefully controlled. In this note we describe a method of processing injection transient signals produced by beam-position monitors and using the processed data in feedback. Feedback control using the technique described here has been incorporated in the Advanced Photon Source (APS booster synchrotron to correct injection transients.

  4. Feedback correction of injection errors using digital signal-processing techniques

    Science.gov (United States)

    Sereno, N. S.; Lenkszus, F. R.

    2007-01-01

    Efficient transfer of electron beams from one accelerator to another is important for 3rd-generation light sources that operate using top-up. In top-up mode, a constant amount of charge is injected at regular intervals into the storage ring to replenish beam lost primarily due to Touschek scattering. Top-up therefore requires that the complex of injector accelerators that fill the storage ring transport beam with a minimum amount of loss. Injection can be a source of significant beam loss if not carefully controlled. In this note we describe a method of processing injection transient signals produced by beam-position monitors and using the processed data in feedback. Feedback control using the technique described here has been incorporated in the Advanced Photon Source (APS) booster synchrotron to correct injection transients.

  5. All-optical signal processing and regeneration

    DEFF Research Database (Denmark)

    Wolfson, David

    2001-01-01

    for multi-channel operation. It is shown that the cascadability of GC-SOAs is superior at 2.5 Gbit/s compared to conventional SOAs for up to at least 16 wavelength channels, whereas the benefit is reduced at higher bit rates due to influence from relaxation oscillations in the GC-SOA. Furthermore, all......The trend in the industry today is that more and more complex functionalities are moving from the electrical domain and into the optical domain, demonstrating that all-optical networks are coming closer to realisation. In order for this progress to continue, there is a need for advanced optical...... amplifier (SOA)-based devices. The thesis starts out by giving a description of the motivations and driving forces for the current evolution of optical networks from point-to-point systems to all-otpical network topologies. The use of SOA-based devices for all-optical gating is investigated with the use...

  6. Real-time feedback based control of cardiac restitution using optical mapping.

    Science.gov (United States)

    Kulkarni, Kanchan; Tolkacheva, Elena G

    2015-01-01

    Cardiac restitution is the shortening of the action potential duration with an increase in the heart rate. A shorter action potential duration enables a longer diastolic interval which ensures that the heart gets adequate time to refill with blood. At higher rates however, restitution becomes steep and thus, can lead to unstable electrical activity (alternans) in the heart, leading to fatal cardiac rhythms. It has been proposed that maintaining a shallow slope of cardiac restitution could have potentially anti-arrhythmic effects. Previous studies involved the control of action potential duration (APD) or diastolic interval (DI) in isolated tissue samples based on the feedback from single microelectrode recordings. This limited the spatial resolution of the feedback system. Here, we aimed to develop a real time feedback control system that enabled the detection of APDs from various single pixels based on optical mapping recordings. Stimuli were applied after a predefined fixed DI after detection of an APD. We validated our algorithm using optical mapping movies from an ex-vivo rabbit heart. Thus, we provide an optical mapping based approach for the control of cardiac restitution and a potential means to validate its anti-arrhythmic effects.

  7. CMF Signal Processing Method Based on Feedback Corrected ANF and Hilbert Transformation

    Directory of Open Access Journals (Sweden)

    Tu Yaqing

    2014-02-01

    Full Text Available In this paper, we focus on CMF signal processing and aim to resolve the problems of precision sharp-decline occurrence when using adaptive notch filters (ANFs for tracking the signal frequency for a long time and phase difference calculation depending on frequency by the sliding Goertzel algorithm (SGA or the recursive DTFT algorithm with negative frequency contribution. A novel method is proposed based on feedback corrected ANF and Hilbert transformation. We design an index to evaluate whether the ANF loses the signal frequency or not, according to the correlation between the output and input signals. If the signal frequency is lost, the ANF parameters will be adjusted duly. At the same time, singular value decomposition (SVD algorithm is introduced to reduce noise. And then, phase difference between the two signals is detected through trigonometry and Hilbert transformation. With the frequency and phase difference obtained, time interval of the two signals is calculated. Accordingly, the mass flow rate is derived. Simulation and experimental results show that the proposed method always preserves a constant high precision of frequency tracking and a better performance of phase difference measurement compared with the SGA or the recursive DTFT algorithm with negative frequency contribution

  8. Ultrafast optical signal processing using semiconductor optical devices

    DEFF Research Database (Denmark)

    Mørk, Jesper; Bischoff, Svend; Berg, Tommy Winther;

    2002-01-01

    We discuss the operation principles of semiconductor devices for ultrafast optical processing, emphasizing the physical processes affecting the device characteristics and the approaches taken to simulate these.......We discuss the operation principles of semiconductor devices for ultrafast optical processing, emphasizing the physical processes affecting the device characteristics and the approaches taken to simulate these....

  9. Optical Frequency Upconversion Technique for Transmission of Wireless MIMO-Type Signals over Optical Fiber

    Directory of Open Access Journals (Sweden)

    R. Q. Shaddad

    2014-01-01

    Full Text Available The optical fiber is well adapted to pass multiple wireless signals having different carrier frequencies by using radio-over-fiber (ROF technique. However, multiple wireless signals which have the same carrier frequency cannot propagate over a single optical fiber, such as wireless multi-input multi-output (MIMO signals feeding multiple antennas in the fiber wireless (FiWi system. A novel optical frequency upconversion (OFU technique is proposed to solve this problem. In this paper, the novel OFU approach is used to transmit three wireless MIMO signals over a 20 km standard single mode fiber (SMF. The OFU technique exploits one optical source to produce multiple wavelengths by delivering it to a LiNbO3 external optical modulator. The wireless MIMO signals are then modulated by LiNbO3 optical intensity modulators separately using the generated optical carriers from the OFU process. These modulators use the optical single-sideband with carrier (OSSB+C modulation scheme to optimize the system performance against the fiber dispersion effect. Each wireless MIMO signal is with a 2.4 GHz or 5 GHz carrier frequency, 1 Gb/s data rate, and 16-quadrature amplitude modulation (QAM. The crosstalk between the wireless MIMO signals is highly suppressed, since each wireless MIMO signal is carried on a specific optical wavelength.

  10. Optical frequency upconversion technique for transmission of wireless MIMO-type signals over optical fiber.

    Science.gov (United States)

    Shaddad, R Q; Mohammad, A B; Al-Gailani, S A; Al-Hetar, A M

    2014-01-01

    The optical fiber is well adapted to pass multiple wireless signals having different carrier frequencies by using radio-over-fiber (ROF) technique. However, multiple wireless signals which have the same carrier frequency cannot propagate over a single optical fiber, such as wireless multi-input multi-output (MIMO) signals feeding multiple antennas in the fiber wireless (FiWi) system. A novel optical frequency upconversion (OFU) technique is proposed to solve this problem. In this paper, the novel OFU approach is used to transmit three wireless MIMO signals over a 20 km standard single mode fiber (SMF). The OFU technique exploits one optical source to produce multiple wavelengths by delivering it to a LiNbO3 external optical modulator. The wireless MIMO signals are then modulated by LiNbO3 optical intensity modulators separately using the generated optical carriers from the OFU process. These modulators use the optical single-sideband with carrier (OSSB+C) modulation scheme to optimize the system performance against the fiber dispersion effect. Each wireless MIMO signal is with a 2.4 GHz or 5 GHz carrier frequency, 1 Gb/s data rate, and 16-quadrature amplitude modulation (QAM). The crosstalk between the wireless MIMO signals is highly suppressed, since each wireless MIMO signal is carried on a specific optical wavelength.

  11. Semiconductor ring lasers with delayed optical feedback: low-frequency fluctuations

    Science.gov (United States)

    Van der Sande, Guy; Mashal, Lilia; Nguimdo, Romain Modeste; Cornelles-Soriano, Miguel C.; Danckaert, Jan; Verschaffelt, Guy

    2014-05-01

    Semiconductor lasers subject to external feedback are known to exhibit a wide variety of dynamical regimes desired for some applications such as chaos cryptography, random bit generation, and reservoir computing. Low-frequency fluctuations is one of the most frequently encountered regimes. It is characterized by a fast drop in laser intensity followed by a gradual recovery. The duration of this recovery process is irregular and of the order of hundred nanoseconds. The average time between dropouts is much larger than the laser system characteristic time-scales. Semiconductor ring lasers are currently the focus of a rapidly thriving research activity due to their unique feature of directional bistability. They can be employed in systems for all-optical switching, gating, wavelength-conversion functions, and all-optical memories. Semiconductor ring lasers do not require cleaved facets or gratings for optical feedback and are thus particularly suited for monolithic integration. We experimentally and numerically address the issue of low-frequency fluctuations considering a semiconductor ring laser in a feedback configuration where only one directional mode is re-injected into the same directional mode, a so-called single self-feedback. We have observed that the system is very sensitive to the feedback strength and the injection current. In particular, the power dropouts are more regular when the pump current is increased and become less frequent when the feedback strength is increased. In addition, we find two different recovery processes after the power dropouts of the low-frequency fluctuations. The recovery can either occur via pulses or in a stepwise manner. Since low-frequency fluctuations are not specific to semiconductor ring lasers, we expect these recovery processes to appear also in VCSELs and edge-emitting lasers under similar feedback conditions. The numerical simulations also capture these different behaviors, where the representation in the phase space of

  12. SCOOP - Semiconductor COmponents for Optical signal Processing

    DEFF Research Database (Denmark)

    Mørk, Jesper; Yvind, Kresten; Oxenløwe, Leif Katsuo;

    2001-01-01

    Opto-electronic semiconductor devices operating at very high bitrates play a central role in the continued expansion of the transmission capacity of optical communication systems. A number of different devices based on quantum well structures have been manufactured within the framework of the nat......Opto-electronic semiconductor devices operating at very high bitrates play a central role in the continued expansion of the transmission capacity of optical communication systems. A number of different devices based on quantum well structures have been manufactured within the framework...... of the national SCOOP programme. Results for a high-speed modulator, a short-pulse laser and an all-optical switch are presented....

  13. Recent Advancements in Semiconductor-based Optical Signal Processing

    DEFF Research Database (Denmark)

    Nielsen, M L; Mørk, Jesper

    2006-01-01

    Significant advancements in technology and basic understanding of device physics are bringing optical signal processing closer to a commercial breakthrough. In this paper we describe the main challenges in high-speed SOA-based switching....

  14. Optical signal processing using electro-absorption modulators

    DEFF Research Database (Denmark)

    Mørk, Jesper; Romstad, Francis Pascal; Højfeldt, Sune

    2003-01-01

    Reverse-biased semiconductor waveguides are efficient saturable absorbers and have a number of promising all-optical signal processing applications. Results on ultrafast modulator dynamics as well as demonstrations and investigations of wavelength conversion and regeneration are presented....

  15. A Nonlinear Distortion Compensation Method with Adaptive Predistorter and Negative Feed-Back for a Narrow-Band Signal

    Science.gov (United States)

    Zhang, Yitao; Muta, Osamu; Akaiwa, Yoshihiko

    The adaptive predistorter and the negative feedback system are known as methods to compensate for the nonlinear distortion of a power amplifier. Although the feedback method is a simple technique, its instability impedes the capability of high-feedback gain to achieve a high-compensation effect. On the other hand, the predistorter requires a long time for convergence of the adaptive predistorters. In this paper, we propose a nonlinear distortion compensation method for a narrow-band signal. In this method, an adaptive predistorter and negative feedback are combined. In addition, to shorten the convergence time to minimize nonlinear distortion, a variable step-size (VS) method is also applied to the algorithm to determine the parameters of the adaptive predistorter. Using computer simulations, we show that the proposed scheme achieves both five times faster convergence speed than that of the predistorter and three times higher permissible delay time in the feedback amplifier than that of a negative feedback only amplifier.

  16. Rescue effects in radiobiology: Unirradiated bystander cells assist irradiated cells through intercellular signal feedback

    Energy Technology Data Exchange (ETDEWEB)

    Chen, S. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong (Hong Kong); Key Laboratory of Ion Beam Bioengineering, Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Zhao, Y. [Key Laboratory of Ion Beam Bioengineering, Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Han, W. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong (Hong Kong); Chiu, S.K. [Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong (Hong Kong); Zhu, L. [Office of Admission and Careers Advisory Service, Shenzhen University, Shenzhen 518060 (China); Wu, L. [Key Laboratory of Ion Beam Bioengineering, Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Yu, K.N., E-mail: peter.yu@cityu.edu.hk [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong (Hong Kong)

    2011-01-10

    Mammalian cells respond to ionization radiation by sending out extracellular signals to affect non-irradiated neighboring cells, which is referred to as radiation induced bystander effect. In the present paper, we described a phenomenon entitled the 'rescue effects', where the bystander cells rescued the irradiated cells through intercellular signal feedback. The effect was observed in both human primary fibroblast (NHLF) and cancer cells (HeLa) using two-cell co-culture systems. After co-culturing irradiated cells with unirradiated bystander cells for 24 h, the numbers of 53BP1 foci, corresponding to the number of DNA double-strand breaks in the irradiated cells were less than those in the irradiated cells that were not co-cultured with the bystander cells (0.78 {+-} 0.04 foci/cell vs. 0.90 {+-} 0.04 foci/cell) at a statistically significant level. Similarly, both micronucleus formation and extent of apoptosis in the irradiated cells were different at statistically significant levels if they were co-cultured with the bystander cells. Furthermore, it was found that unirradiated normal cells would also reduce the micronucleus formation in irradiated cancer cells. These results suggested that the rescue effects could participate in repairing the radiation-induced DNA damages through a media-mediated signaling feedback, thereby mitigating the cytotoxicity and genotoxicity of ionizing radiation.

  17. New modulator for the optical signal in a fiber

    Institute of Scientific and Technical Information of China (English)

    ZHANG Tian-hao; JIA Feng; WANG Shun-li; MAN Jiang wei; NIU Kai; WANG Xu-cheng; YANG Jia

    2006-01-01

    A new modulator for the optical signal in a fiber based on multi-beam interference is designed. In the experiment,the distance of a couple of abutted fibers was modulated through a piezoelectric ceramic pipe driven by 50 Hz AC voltage, so that the amplitude of the transmitted optical signal was modulated. The modulation ratio is about 10% ,S/N ratio is about 60 dB and the bandwidth is about 200 KHz.

  18. High-speed optical signal processing using time lenses

    DEFF Research Database (Denmark)

    Galili, Michael; Hu, Hao; Guan, Pengyu;

    2015-01-01

    This paper will discuss time lenses and their broad range of applications. A number of recent demonstrations of complex high-speed optical signal processing using time lenses will be outlined with focus on the operating principle.......This paper will discuss time lenses and their broad range of applications. A number of recent demonstrations of complex high-speed optical signal processing using time lenses will be outlined with focus on the operating principle....

  19. Estimating the Spectral Width of a Narrowband Optical Signal

    DEFF Research Database (Denmark)

    Lading, Lars; Skov Jensen, A.

    1980-01-01

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

  20. Nonlinear Real-Time Optical Signal Processing.

    Science.gov (United States)

    1983-12-01

    8217 " University of Southern CaliforniaN JU Los Angeles, California 90089-0272 " --;984. ,’ I ’I Research Sponsored by the ., k Air Force Office of...concentrates on experimental results from the sixteen gate clocked master-slave optical flip-flop. A second paper " Architectures for a Sequential Optical Logic...purpose computer could permit the realization of a number of architectural advantages over semiconductor electronics [27]. These advantages include

  1. Nonlinear Optical Signal Processing for Tbit/s Ethernet Applications

    DEFF Research Database (Denmark)

    Oxenløwe, Leif Katsuo; Galili, Michael; Mulvad, Hans Christian Hansen;

    2012-01-01

    We review recent experimental demonstrations of Tbaud optical signal processing. In particular, we describe a successful 1.28 Tbit/s serial data generation based on single polarization 1.28 Tbaud symbol rate pulses with binary data modulation (OOK) and subsequent all-optical demultiplexing. We also...

  2. Fast optical signal processing in high bit rate OTDM systems

    DEFF Research Database (Denmark)

    Poulsen, Henrik Nørskov; Jepsen, Kim Stokholm; Clausen, Anders;

    1998-01-01

    As all-optical signal processing is maturing, optical time division multiplexing (OTDM) has also gained interest for simple networking in high capacity backbone networks. As an example of a network scenario we show an OTDM bus interconnecting another OTDM bus, a single high capacity user...

  3. All-Optical Signal Processing using Silicon Devices

    DEFF Research Database (Denmark)

    Oxenløwe, Leif Katsuo; Pu, Minhao; Ding, Yunhong;

    2014-01-01

    This paper presents an overview of recent wo rk on the use of silicon waveguides for processing optical data signals. We will describe ultra-fast, ultra-broadband, polarisation-insensitive and phase-sensitive applications including processing of spectrally-efficient data formats and optical phase...

  4. Nonlinear Dynamics of Photonics for Optical Signal Processing - Optical Frequency Conversion and Optical DSB-to-SSB Conversion

    Science.gov (United States)

    2015-09-17

    processing - optical frequency conversion and optical DSB -to-SSB conversion 5a. CONTRACT NUMBER FA2386-14-1-0006 5b. GRANT NUMBER Grant 134113...nonlinear dynamics of semiconductor lasers for certain optical signal processing functionalities, including optical DSB -to-SSB conversion, photonic...conversion and optical DSB -to-SSB conversion Performance Period May 30, 2014 ~ May 29, 2015 Principal Investigator Name: Sheng-Kwang Hwang Position

  5. Design, parametrization, and pole placement of stabilizing output feedback compensators via injective cogenerator quotient signal modules.

    Science.gov (United States)

    Blumthaler, Ingrid; Oberst, Ulrich

    2012-03-01

    Control design belongs to the most important and difficult tasks of control engineering and has therefore been treated by many prominent researchers and in many textbooks, the systems being generally described by their transfer matrices or by Rosenbrock equations and more recently also as behaviors. Our approach to controller design uses, in addition to the ideas of our predecessors on coprime factorizations of transfer matrices and on the parametrization of stabilizing compensators, a new mathematical technique which enables simpler design and also new theorems in spite of the many outstanding results of the literature: (1) We use an injective cogenerator signal module ℱ over the polynomial algebra [Formula: see text] (F an infinite field), a saturated multiplicatively closed set T of stable polynomials and its quotient ring [Formula: see text] of stable rational functions. This enables the simultaneous treatment of continuous and discrete systems and of all notions of stability, called T-stability. We investigate stabilizing control design by output feedback of input/output (IO) behaviors and study the full feedback IO behavior, especially its autonomous part and not only its transfer matrix. (2) The new technique is characterized by the permanent application of the injective cogenerator quotient signal module [Formula: see text] and of quotient behaviors [Formula: see text] of [Formula: see text]-behaviors B. (3) For the control tasks of tracking, disturbance rejection, model matching, and decoupling and not necessarily proper plants we derive necessary and sufficient conditions for the existence of proper stabilizing compensators with proper and stable closed loop behaviors, parametrize all such compensators as IO behaviors and not only their transfer matrices and give new algorithms for their construction. Moreover we solve the problem of pole placement or spectral assignability for the complete feedback behavior. The properness of the full feedback behavior

  6. Reflected Power Measurement of Antennas between 0 and 4 GHz Using Optical Mixing of Distributed Feedback Lasers

    Directory of Open Access Journals (Sweden)

    A. Garcia Juarez

    2013-12-01

    Full Text Available Reflected power measurement of antennas by using an alternative microwave photonic system is presented in this paper. The proposed experimental setup is based on optical mixing of two distributed feedback (DFB lasers, where combined beams are detected by a photo-detector. The resulting photocurrent corresponds to a microwave signal which is continuously tuned on bandwidths from 0 to 4 GHz. The obtained swept frequency is applied to an antenna in order to measure its reflected power. Error sources that limit the measurement accuracy of optical mixing such as effect of power deviation in the linewidth of the beat signal and errors introduced by extra fixture are studied. Results of the measurements obtained with the proposed photonic technique are calibrated and compared with traditional electrical measurements. The most important motivation on the use of the proposed technique in this paper lies in that with a simple configuration we were able to characterize microwave devices in a very wide frequency range, avoiding the use of a vector network analyzer (VNA, and thus, a complicated and tedious calibration procedure, contributing to the field of instrumentation and characterization by using photonic techniques.

  7. Negative feedback regulation of Wnt4 signaling by EAF1 and EAF2/U19.

    Directory of Open Access Journals (Sweden)

    Xiaoyang Wan

    Full Text Available Previous studies indicated that EAF (ELL-associated factor family members, EAF1 and EAF2/U19, play a role in cancer and embryogenesis. For example, EAF2/U19 may serve as a tumor suppressor in prostate cancer. At the same time, EAF2/U19 is a downstream factor in the non-canonical Wnt 4 signaling pathway required for eye development in Xenopus laevis, and along with EAF1, contributes to convergence and extension movements in zebrafish embryos through Wnt maintenance. Here, we used zebrafish embryos and mammalian cells to show that both EAF1 and EAF2/U19 were up-regulated by Wnt4 (Wnt4a. Furthermore, we found that EAF1 and EAF2/U19 suppressed Wnt4 expression by directly binding to the Wnt4 promoter as seen in chromatin immunoprecipitation assays. These findings indicate that an auto-regulatory negative feedback loop occurs between Wnt4 and the EAF family, which is conserved between zebrafish and mammalian. The rescue experiments in zebrafish embryos showed that early embryonic development required the maintenance of the appropriate levels of Wnt4a through the feedback loop. Others have demonstrated that the tumor suppressors p63, p73 and WT1 positively regulate Wnt4 expression while p21 has the opposite effect, suggesting that maintenance of appropriate Wnt4 expression may also be critical for adult tissue homeostasis and prevention against tumor initiation. Thus, the auto-regulatory negative feedback loop that controls expression of Wnt4 and EAF proteins may play an important role in both embryonic development and tumor suppression. Our findings provide the first convincing line of evidence that EAF and Wnt4 form an auto-regulatory negative feedback loop in vivo.

  8. Quantum Theory of Cavityless Feedback Cooling of An Optically Trapped Nanoparticle

    CERN Document Server

    Rodenburg, B; Vamivakas, A N; Bhattacharya, M

    2015-01-01

    We present a quantum theory of cavityless feedback cooling of an optically trapped harmonically oscillating subwavelength dielectric particle, a configuration recently realized in several experiments. Specifically, we derive a Markovian master equation that treats the mechanical as well as optical degrees of freedom quantum mechanically. Employing this equation, we solve for the nanoparticle phonon number dynamics exactly, and extract analytic expressions for the cooling timescale and the steady state phonon number. We present experimental data verifying the predictions of our model in the classical regime, and also demonstrate that quantum ground state preparation is within reach of ongoing experiments. Our work provides a quantitative framework for future theoretical modeling of the cavityless quantum optomechanics of optically trapped dielectric particles.

  9. Sampling impairments influence over stealthy fiber-optic signal decryption

    Science.gov (United States)

    Yeminy, Tomer; Sadot, Dan; Zalevsky, Zeev

    2013-03-01

    Recently we have proposed a method for temporal and spectral stealthy fiber-optic communications. In this technique the signal is spread in the time domain below the noise level and the power spectral density of the signal is spread beneath the noise level in the frequency domain. The power spectral density of the signal is reconstructed by means of sampling which results in coherent addition of the encrypted signal spectral replicas. Hence, the sampling quality plays a major role in the ability to successfully decrypt the received covert signal. In this paper, we mathematically and numerically analyze the effect of sampling impairments over the decryption performance.

  10. A study of spatial phenomena in semiconductor lasers: Beam filamentation and optical feedback effects

    Science.gov (United States)

    Marciante, John Robert

    1997-10-01

    In an effort to improve the performance of high-power semiconductor lasers to meet the demands of applications, this thesis contains work studying the issues which limit their performance: beam filamentation and spatial feedback effects. Through computer simulations, we investigate the role of three nonlinear mechanisms which can lead to filamentation, and determine the stability boundaries of the material parameters for which the device will not exhibit filamentary tendencies. We use an analytic theory to verify these findings, and to predict the spatio- temporal nature of the filaments through an analytic expression for the gain, in which contributions of the various mechanisms can clearly be seen. We experimentally verify the spatio-temporal characteristics of the filaments, discover effects of the stripe width and transitions to chaos, and discuss how to compare the relative severity of filamentation among different devices. We propose a new method of controlling filamentation using below-bandgap semiconductor nonlinearities. With simulations, we determine under what conditions this imposed nonlinearity can counteract the carrier-induced self-focusing inside the active region. We fabricate a prototype device using new epitaxial layers containing the below-bandgap nonlinearities, and compare the performance of these new devices to a control set. In studying the spatial effects of optical feedback, we use Fresnel diffraction theory to derive an expression for the field that is reflected back into the laser. This result is applied to our computer model and used to explore the effects of feedback on narrow-stripe, broad- area, and tapered-stripe semiconductor lasers. Re- examining feedback in narrow-stripe devices through experiments and analytic theory, we investigate the coupling effects between the narrow waveguide and the feedback field, and the changes in the operating characteristics of the laser due to this coupling. We experimentally examine the beam

  11. Advanced Optical Processing of Microwave Signals

    Directory of Open Access Journals (Sweden)

    Miguel V. Andrés

    2005-06-01

    Full Text Available The authors present a review on the recent approaches proposed to implement transversal RF filters. Different tunable transversal filters consisting of wavelength tunable optical taps and those employing the tunability of dispersive devices are presented showing their high-performance characteristics. A comprehensive review of the fundamentals and a discussion on the main limitation of these structures are also included.

  12. Variable-time-delay optical coherent transient signal processing.

    Science.gov (United States)

    Merkel, K D; Babbitt, W R; Anderson, K E; Wagner, K H

    1999-10-15

    A technique is proposed and experimentally demonstrated that achieves simultaneous optical pattern waveform storage and programmable time delay for continuous real-time signal processing by use of optical coherent transient technology. We achieve variable-time-delay and broadband signal processing by frequency shifting of two chirped programming pulses, the chirp rate of one being twice that of the other, without using brief reference pulses and without changing the timing of the programming sequence. We demonstrate the technique experimentally in Tm(3+): YAG at 5 K for 40-MHz chirps by performing temporal signal convolution with true-time delays that vary over a 250-ns range.

  13. Modeling of Nonlinear Signal Distortion in Fiber-Optical Networks

    CERN Document Server

    Johannisson, Pontus

    2013-01-01

    A low-complexity model for signal quality prediction in a nonlinear fiber-optical network is developed. The model, which builds on the Gaussian noise model, takes into account the signal degradation caused by a combination of chromatic dispersion, nonlinear signal distortion, and amplifier noise. The center frequencies, bandwidths, and transmit powers can be chosen independently for each channel, which makes the model suitable for analysis and optimization of resource allocation, routing, and scheduling in large-scale optical networks applying flexible-grid wavelength-division multiplexing.

  14. Simultaneous measurement of patterns in the signal and idler near and far fields from a confocal optical parametrical oscillator with applications in quantum optics

    DEFF Research Database (Denmark)

    Lassen, Mikael Østergaard; Tidemand-Lichtenberg, Peter; Buchhave, Preben

    2005-01-01

    investigation of quantum correlations in the transverse plane. We describe the experimental setup for simultaneous measurements of signal and idler near- and far-field patterns and analyze the effects of various experimental complications such as walk-off and thermal index changes on the generated patterns. We...... also show that the oscillator can be stabilized by optical feedback, indicating a possible route for controlling the generated intensity patterns....

  15. Nonlinear fiber applications for ultrafast all-optical signal processing

    Science.gov (United States)

    Kravtsov, Konstantin

    In the present dissertation different aspects of all-optical signal processing, enabled by the use of nonlinear fibers, are studied. In particular, we focus on applications of a novel heavily GeO2-doped (HD) nonlinear fiber, that appears to be superior to many other types of nonlinear fibers because of its high nonlinearity and suitability for the use in nonlinear optical loop mirrors (NOLMs). Different functions, such as all-optical switching, thresholding, and wavelength conversion, are demonstrated with the HD fibers in the NOLM configuration. These basic functions are later used for realization of ultrafast time-domain demultiplexers, clock recovery, detectors of short pulses in stealth communications, and primitive elements for analog computations. Another important technology that benefits from the use of nonlinear fiber-based signal processing is optical code-division multiple access (CDMA). It is shown in both theory and experiment that all-optical thresholding is a unique way of improving existing detection methods for optical CDMA. Also, it is the way of implementation of true asynchronous optical spread-spectrum networks, which allows full realization of optical CDMA potential. Some aspects of quantum signal processing and manipulation of quantum states are also studied in this work. It is shown that propagation and collisions of Thirring solitons lead to a substantial squeezing of quantum states, which may find applications for generation of squeezed light.

  16. Digital Signal Processing for Optical Coherent Communication Systems

    DEFF Research Database (Denmark)

    Zhang, Xu

    In this thesis, digital signal processing (DSP) algorithms are studied to compensate for physical layer impairments in optical fiber coherent communication systems. The physical layer impairments investigated in this thesis include optical fiber chromatic dispersion, polarization demultiplexing......, light sources frequency and phase offset and phase noise. The studied DSP algorithms are considered as key building blocks in digital coherent receivers for the next generation of optical communication systems such as 112-Gb/s dual polarization (DP) quadrature phase shift keying (QPSK) optical...... spectrum narrowing tolerance 112-Gb/s DP-QPSK optical coherent systems using digital adaptive equalizer. The demonstrated results show that off-line DSP algorithms are able to reduce the bit error rate (BER) penalty induced by signal spectrum narrowing. Third, we also investigate bi...

  17. Nonlinear Silicon Photonic Signal Processing Devices for Future Optical Networks

    Directory of Open Access Journals (Sweden)

    Cosimo Lacava

    2017-01-01

    Full Text Available In this paper, we present a review on silicon-based nonlinear devices for all optical nonlinear processing of complex telecommunication signals. We discuss some recent developments achieved by our research group, through extensive collaborations with academic partners across Europe, on optical signal processing using silicon-germanium and amorphous silicon based waveguides as well as novel materials such as silicon rich silicon nitride and tantalum pentoxide. We review the performance of four wave mixing wavelength conversion applied on complex signals such as Differential Phase Shift Keying (DPSK, Quadrature Phase Shift Keying (QPSK, 16-Quadrature Amplitude Modulation (QAM and 64-QAM that dramatically enhance the telecom signal spectral efficiency, paving the way to next generation terabit all-optical networks.

  18. Controlling Chaos in a Semiconductor Laser via Weak Optical Positive Feedback and Modulating Amplitude

    Institute of Scientific and Technical Information of China (English)

    YAN Sen-Lin

    2007-01-01

    Numerical analysis of weak optical positive feedback (OPF) controlling chaos is studied in a semiconductor laser.The physical model of controlling chaos produced via modulating the current of semiconductor laser is presented under the condition of OPF.We find the physical mechanism that the nonlinear gain coefficient and linewidth enhancement factor of the laser are affected by OPF so that the dynamical behaviour of the system can be efficiently controlled.Chaos is controlled into a single-periodic state,a dual-periodic state,a fri-periodic state,a quadr-periodic state,a pentaperiodic state,and the laser emitting powers are increased by OPF in simulations.Lastly,another chaos-control method with modulating the amplitude of the feedback light is presented and numerically simulated to control chaotic laser into multi-periodic states.

  19. Suppression of Classical and Quantum Radiation Pressure Noise via Electro-Optic Feedback

    CERN Document Server

    Buchler, B C; Shaddock, D A; Ralph, T C; McClelland, D E; Buchler, Ben C.; Gray, Malcolm B.; Shaddock, Daniel A.; Ralph, Timothy C.; Clelland, David E. Mc

    1998-01-01

    We present theoretical results that demonstrate a new technique to be used to improve the sensitivity of thermal noise measurements: intra-cavity intensity stabilisation. It is demonstrated that electro-optic feedback can be used to reduce intra-cavity intensity fluctuations, and the consequent radiation pressure fluctuations, by a factor of two below the quantum noise limit. We show that this is achievable in the presence of large classical intensity fluctuations on the incident laser beam. The benefits of this scheme are a consequence of the sub-Poissonian intensity statistics of the field inside a feedback loop, and the quantum non-demolition nature of radiation pressure noise as a readout system for the intra-cavity intensity fluctuations.

  20. Recovering Signals from Optical Fiber Interferometric Sensors

    Science.gov (United States)

    1991-06-01

    explained in numerous books on operational amplifiers (for example, see Sedra and Smith [Ref. 171) and so will not be further discussed here, except to say...618. 1 October 1982. 17. Sedra , A. S.. and Smith .- K. C.. Microelectronic CrciimHolt. Rinehart and Winston, 1982. 18. Abramowitz, M. and- Stegun. I.A...Interfcromctcrse, Applied Optics. Volume 21. Number 4. 689-693. 1982. 46. Smith , L. and Sheingold, D.H.. "Noise and Operational Amplifier Circuits’, Analog

  1. Enhancement of second-order nonlinear-optical signals by optical stimulation

    CERN Document Server

    Goodman, Aaron J

    2015-01-01

    Second-order nonlinear optical interactions such as sum- and difference-frequency generation are widely used for bioimaging and as selective probes of interfacial environments. However, inefficient nonlinear optical conversion often leads to poor signal-to-noise ratio and long signal acquisition times. Here, we demonstrate the dramatic enhancement of weak second-order nonlinear optical signals via stimulated sum- and difference-frequency generation. We present a conceptual framework to quantitatively describe the interaction and show that the process is highly sensitive to the relative optical phase of the stimulating field. To emphasize the utility of the technique, we demonstrate stimulated enhancement of second harmonic generation (SHG) from bovine collagen-I fibrils. Using a stimulating pulse fluence of only 3 nJ/cm2, we obtain an SHG enhancement >10^4 relative to the spontaneous signal. The stimulation enhancement is greatest in situations where spontaneous signals are the weakest - such as low laser pow...

  2. DEVELOPMENT OF A FAST MICRON-RESOLUTION BEAM POSITION MONITOR SIGNAL PROCESSOR FOR LINEAR COLLIDER BEAMBASED FEEDBACK SYSTEMS

    CERN Document Server

    Apsimon, R; Clarke, C; Constance, B; Dabiri Khah, H; Hartin, T; Perry, C; Resta Lopez, J; Swinson, C; Christian, G B; Kalinin, A

    2009-01-01

    We present the design of a prototype fast beam position monitor (BPM) signal processor for use in inter-bunch beam-based feedbacks for linear colliders and electron linacs. We describe the FONT4 intra-train beam-based digital position feedback system prototype deployed at the Accelerator test facility (ATF) extraction line at KEK, Japan. The system incorporates a fast analogue beam position monitor front-end signal processor, a digital feedback board, and a fast kicker-driver amplifier. The total feedback system latency is less than 150ns, of which less than 10ns is used for the BPM processor. We report preliminary results of beam tests using electron bunches separated by c. 150ns. Position resolution of order 1 micron was obtained.

  3. Optical switches for remote and noninvasive control of cell signaling.

    Science.gov (United States)

    Gorostiza, Pau; Isacoff, Ehud Y

    2008-10-17

    Although the identity and interactions of signaling proteins have been studied in great detail, the complexity of signaling networks cannot be fully understood without elucidating the timing and location of activity of individual proteins. To do this, one needs a means for detecting and controlling specific signaling events. An attractive approach is to use light, both to report on and control signaling proteins in cells, because light can probe cells in real time with minimal damage. Although optical detection of signaling events has been successful for some time, the development of the means for optical control has accelerated only recently. Of particular interest is the development of chemically engineered proteins that are directly sensitive to light.

  4. Decision feedback equalization with multichannel readback in high-density optical recording

    Science.gov (United States)

    Gopalaswamy, Srinivasan; Vijaya Kumar, Bhagavatula

    1995-12-01

    Multi-channel readback using array heads has been reported in optical recording. A method to reduce both interference along and across the tracks using multi-channel readback is presented. In this method, the non-linear multi-channel decision feedback equalization is used to remove both forms of interference. Simulation results show good improvement (in performance) by using the multi-channel equalization. By this readback method, tracks can be brought closer, thus increasing the areal density. Another advantage of this method is the high data rate possible.

  5. Anticipation in the synchronization of chaotic semiconductor lasers with optical feedback.

    Science.gov (United States)

    Masoller, C

    2001-03-26

    The synchronization of chaotic semiconductor lasers with optical feedback is studied numerically in a one-way coupling configuration, in which a small amount of the intensity of one laser (master laser) is injected coherently into the other (slave laser). A regime of anticipated synchronization is found, in which the intensity of the slave laser is synchronized to the future chaotic intensity of the master laser. Anticipation is robust to small noise and parameter mismatches, but in this case the synchronization is not complete. It is also shown that anticipated synchronization occurs in coupled time-delay systems, when the coupling has a delay that is less than the delay of the systems.

  6. Ab initio quantum-enhanced optical phase estimation using real-time feedback control

    DEFF Research Database (Denmark)

    Berni, Adriano; Gehring, Tobias; Nielsen, Bo Melholt

    2015-01-01

    as demonstrated in a variety of different optical systems(3-8). Most of these accounts, however, deal with the measurement of a very small shift of an already known phase, which is in stark contrast to ab initio phase estimation where the initial phase is unknown(9-12). Here, we report on the realization...... of a quantum-enhanced and fully deterministic ab initio phase estimation protocol based on real-time feedback control. Using robust squeezed states of light combined with a real-time Bayesian adaptive estimation algorithm, we demonstrate deterministic phase estimation with a precision beyond the quantum shot...

  7. Demonstration of optical steganography transmission using temporal phase coded optical signals with spectral notch filtering.

    Science.gov (United States)

    Hong, Xuezhi; Wang, Dawei; Xu, Lei; He, Sailing

    2010-06-07

    A novel approach is proposed and experimentally demonstrated for optical steganography transmission in WDM networks using temporal phase coded optical signals with spectral notch filtering. A temporal phase coded stealth channel is temporally and spectrally overlaid onto a public WDM channel. Direct detection of the public channel is achieved in the presence of the stealth channel. The interference from the public channel is suppressed by spectral notching before the detection of the optical stealth signal. The approach is shown to have good compatibility and robustness to the existing WDM network for optical steganography transmission.

  8. Time-Domain Large Signal Investigation on Dynamic Responses of the GDCC Quarterly Wavelength Shifted Distributed Feedback Semiconductor Laser

    Directory of Open Access Journals (Sweden)

    Hamza Bousseta

    2012-09-01

    Full Text Available A numerical investigation on the dynamic large-signal analysis using a time-domain traveling wave model of quarter wave-shifted distributed feedback semiconductor lasers diode with a Gaussian distribution of the coupling coefficient (GDCC is presented. It is found that the single-mode behavior and the more hole-burning effect corrections of quarter wave-shifted distributed feedback laser with large coupling coefficient can be improved significantly by this new proposed light source.

  9. Suppressor of cytokine signalling-6 promotes neurite outgrowth via JAK2/STAT5-mediated signalling pathway, involving negative feedback inhibition.

    Directory of Open Access Journals (Sweden)

    Sakshi Gupta

    Full Text Available BACKGROUND: Suppressors of cytokine signalling (SOCS protein family are key regulators of cellular responses to cytokines and play an important role in the nervous system. The SOCS6 protein, a less extensively studied SOCS family member, has been shown to induce insulin resistance in the retina and promote survival of the retinal neurons. But no reports are available about the role of SOCS6 in neuritogenesis. In this study, we examined the role of SOCS6 in neurite outgrowth and neuronal cell signalling. METHODOLOGY/PRINCIPAL FINDINGS: The effect of SOCS6 in neural stem cells differentiation was studied in neural stem cells and PC12 cell line. Highly elevated levels of SOCS6 were found upon neural cell differentiation both at the mRNA and protein level. Furthermore, SOCS6 over-expression lead to increase in neurite outgrowth and degree of branching, whereas SOCS6 knockdown with specific siRNAs, lead to a significant decrease in neurite initiation and extension. Insulin-like growth factor-1 (IGF-1 stimulation which enhanced neurite outgrowth of neural cells resulted in further enhancement of SOCS6 expression. Jak/Stat (Janus Kinase/Signal Transducer And Activator Of Transcription pathway was found to be involved in the SOCS6 mediated neurite outgrowth. Bioinformatics study revealed presence of putative Stat binding sites in the SOCS6 promoter region. Transcription factors Stat5a and Stat5b were involved in SOCS6 gene upregulation leading to neuronal differentiation. Following differentiation, SOCS6 was found to form a ternary complex with IGFR (Insulin Like Growth Factor-1 Receptor and JAK2 which acted in a negative feedback loop to inhibit pStat5 activation. CONCLUSION/SIGNIFICANCE: The current paradigm for the first time states that SOCS6, a SOCS family member, plays an important role in the process of neuronal differentiation. These findings define a novel molecular mechanism for Jak2/Stat5 mediated SOCS6 signalling.

  10. Nonlinear optical signal processing for high-speed, spectrally efficient fiber optic systems and networks

    Science.gov (United States)

    Zhang, Bo

    The past decade has witnessed astounding boom in telecommunication network traffic. With the emergence of multimedia over Internet, the high-capacity optical transport systems have started to shift focus from the core network towards the end users. This trend leads to diverse optical networks with transparency and reconfigurability requirement. As single channel data rate continues to increase and channel spacing continues to shrink for high capacity, high spectral efficiency, the workload on conventional electronic signal processing elements in the router nodes continues to build up. Performing signal processing functions in the optical domain can potentially alleviate the speed bottleneck if the unique optical properties are efficiently leveraged to assist electronic processing methodologies. Ultra-high bandwidth capability along with the promise for multi-channel and format-transparent operation make optical signal processing an attractive technology which is expected to have great impact on future optical networks. For optical signal processing applications in fiber-optic network and systems, a laudable goal would be to explore the unique nonlinear optical processes in novel photonic devices. This dissertation investigates novel optical signal processing techniques through simulations and experimental demonstrations, analyzes limitations of these nonlinear processing elements and proposes techniques to enhance the system performance or designs for functional photonic modules. Two key signal-processing building blocks for future optical networks, namely slow-light-based tunable optical delay lines and SOA-based high-speed wavelength converters, are presented in the first part of the dissertation. Phase preserving and spectrally efficient slow light are experimentally demonstrated using advanced modulation formats. Functional and novel photonic modules, such as multi-channel synchronizer and variable-bit-rate optical time division multiplexer are designed and

  11. Ultra-high-speed Optical Signal Processing using Silicon Photonics

    DEFF Research Database (Denmark)

    Oxenløwe, Leif Katsuo; Ji, Hua; Jensen, Asger Sellerup

    on silicon photonics. In particular we use nano-engineered silicon waveguides (nanowires) [1] enabling efficient phasematched four-wave mixing (FWM), cross-phase modulation (XPM) or self-phase modulation (SPM) for ultra-high-speed optical signal processing of ultra-high bit rate serial data signals. We show......— In supercomputers, the optical inter-connects are getting closer and closer to the processing cores. Today, a single supercomputer system has as many optical links as the whole worldwide web together, and it is envisaged that future computing chips will contain multiple electronic processor cores...... with a photonic layer on top to interconnect them. For such systems, silicon is an attractive candidate enabling both electronic and photonic control. For some network scenarios, it may be beneficial to use optical on-chip packet switching, and for high data-density environments one may take advantage...

  12. Localization and Imaging of Integrated Circuit Defect Using Simple Optical Feedback Detection

    Directory of Open Access Journals (Sweden)

    Vernon Julius Cemine

    2004-12-01

    Full Text Available High-contrast microscopy of semiconductor and metal edifices in integrated circuits is demonstrated by combining laser-scanning confocal reflectance microscopy, one-photon optical-beam-induced current (1P-OBIC imaging, and optical feedback detection via a commercially available semiconductor laser that also serves as the excitation source. The confocal microscope has a compact in-line arrangement with no external photodetector. Confocal and 1P-OBIC images are obtained simultaneously from the same focused beam that is scanned across the sample plane. Image pairs are processed to generate exclusive high-contrast distributions of the semiconductor, metal, and dielectric sites in a GaAs photodiode array sample. The method is then utilized to demonstrate defect localization and imaging in an integrated circuit.

  13. Collaborative Assembly Operation between Two Modular Robots Based on the Optical Position Feedback

    Directory of Open Access Journals (Sweden)

    Liying Su

    2009-01-01

    Full Text Available This paper studies the cooperation between two master-slave modular robots. A cooperative robot system is set up with two modular robots and a dynamic optical meter-Optotrak. With Optotrak, the positions of the end effectors are measured as the optical position feedback, which is used to adjust the robots' end positions. A tri-layered motion controller is designed for the two cooperative robots. The RMRC control method is adopted to adjust the master robot to the desired position. With the kinematics constraints of the two robots including position and pose, joint velocity, and acceleration constraints, the two robots can cooperate well. A bolt and nut assembly experiment is executed to verify the methods.

  14. Phase-locked Optical Signal Recovery

    Science.gov (United States)

    2009-01-01

    receiver was typically operated with the mean signal power at the input set to +13 dBm by the erbium-doped fibre amplifier ( EDFA ) at the input. This...stage EDFA which acts as a source of amplified spontaneous emission (ASE) noise. The first EDFA stage was run at constant output power of around 0 dBm...total ASE power and then amplified to typically 13 dBm. The EDFA after the filter was operated with a relatively high input power (around -4 dBm), so

  15. The digital traces of bubbles: feedback cycles between socio-economic signals in the Bitcoin economy

    Science.gov (United States)

    Garcia, David; Tessone, Claudio J.; Mavrodiev, Pavlin; Perony, Nicolas

    2014-01-01

    What is the role of social interactions in the creation of price bubbles? Answering this question requires obtaining collective behavioural traces generated by the activity of a large number of actors. Digital currencies offer a unique possibility to measure socio-economic signals from such digital traces. Here, we focus on Bitcoin, the most popular cryptocurrency. Bitcoin has experienced periods of rapid increase in exchange rates (price) followed by sharp decline; we hypothesize that these fluctuations are largely driven by the interplay between different social phenomena. We thus quantify four socio-economic signals about Bitcoin from large datasets: price on online exchanges, volume of word-of-mouth communication in online social media, volume of information search and user base growth. By using vector autoregression, we identify two positive feedback loops that lead to price bubbles in the absence of exogenous stimuli: one driven by word of mouth, and the other by new Bitcoin adopters. We also observe that spikes in information search, presumably linked to external events, precede drastic price declines. Understanding the interplay between the socio-economic signals we measured can lead to applications beyond cryptocurrencies to other phenomena that leave digital footprints, such as online social network usage. PMID:25100315

  16. The digital traces of bubbles: feedback cycles between socio-economic signals in the Bitcoin economy.

    Science.gov (United States)

    Garcia, David; Tessone, Claudio J; Mavrodiev, Pavlin; Perony, Nicolas

    2014-10-06

    What is the role of social interactions in the creation of price bubbles? Answering this question requires obtaining collective behavioural traces generated by the activity of a large number of actors. Digital currencies offer a unique possibility to measure socio-economic signals from such digital traces. Here, we focus on Bitcoin, the most popular cryptocurrency. Bitcoin has experienced periods of rapid increase in exchange rates (price) followed by sharp decline; we hypothesize that these fluctuations are largely driven by the interplay between different social phenomena. We thus quantify four socio-economic signals about Bitcoin from large datasets: price on online exchanges, volume of word-of-mouth communication in online social media, volume of information search and user base growth. By using vector autoregression, we identify two positive feedback loops that lead to price bubbles in the absence of exogenous stimuli: one driven by word of mouth, and the other by new Bitcoin adopters. We also observe that spikes in information search, presumably linked to external events, precede drastic price declines. Understanding the interplay between the socio-economic signals we measured can lead to applications beyond cryptocurrencies to other phenomena that leave digital footprints, such as online social network usage.

  17. Silicon technology compatible photonic molecules for compact optical signal processing

    Energy Technology Data Exchange (ETDEWEB)

    Barea, Luis A. M., E-mail: barea@ifi.unicamp.br; Vallini, Felipe; Jarschel, Paulo F.; Frateschi, Newton C. [Device Research Laboratory, Applied Physics Department, “GlebWataghin” Physics Institute, University of Campinas–UNICAMP, 13083-859 Campinas, SP (Brazil)

    2013-11-11

    Photonic molecules (PMs) based on multiple inner coupled microring resonators allow to surpass the fundamental constraint between the total quality factor (Q{sub T}), free spectral range (FSR), and resonator size. In this work, we use a PM that presents doublets and triplets resonance splitting, all with high Q{sub T}. We demonstrate the use of the doublet splitting for 34.2 GHz signal extraction by filtering the sidebands of a modulated optical signal. We also demonstrate that very compact optical modulators operating 2.75 times beyond its resonator linewidth limit may be obtained using the PM triplet splitting, with separation of ∼55 GHz.

  18. All-optical network coding for DPSK signals

    DEFF Research Database (Denmark)

    An, Yi; Da Ros, Francesco; Peucheret, Christophe

    2013-01-01

    All-optical network coding for path protection is experimentally demonstrated using four-wave mixing in SOAs for10 Gbit/s NRZ-DPSK signals with error free performance. The total power penalty after two cascaded XOR stage is only 2 dB.......All-optical network coding for path protection is experimentally demonstrated using four-wave mixing in SOAs for10 Gbit/s NRZ-DPSK signals with error free performance. The total power penalty after two cascaded XOR stage is only 2 dB....

  19. Activation of cell signaling via optical manipulation of gold-coated liposomes encapsulating signaling molecules

    Science.gov (United States)

    Orsinger, Gabriel V.; Leung, Sarah J.; Romanowski, Marek

    2013-02-01

    Many diseases involve changes in cell signaling cascades, as seen commonly in drug resistant cancers. To better understand these intricate signaling events in diseased cells and tissues, experimental methods of probing cellular communication at a single to multi-cell level are required. We recently introduced a general platform for activation of selected signaling pathways by optically controlled delivery and release of water soluble factors using gold-coated liposomes. In the example presented here, we encapsulated inositol trisphosphate (IP3), a ubiquitous intracellular secondary messenger involved in GPCR and Akt signaling cascades, within 100 nm gold-coated liposomes. The high polarizability of the liposome's unique gold pseudo-shell allows stable optical trapping for subcellular manipulation in the presence of cells. We take this optical manipulation further by optically injecting IP3-containing liposomes into the cytosol of a single cell to initiate localized cell signaling. Upon optical injection of liposomal IP3 into a single ovarian carcinoma cell, we observed localized activation as reported by changes in Indo-1 fluorescence intensity. With established gap junctions between the injected cell and neighboring cells, we monitored propagation of this signaling to and through nearby cells.

  20. Investigating dynamics of inhibitory and feedback loops in ERK signalling using power-law models.

    Science.gov (United States)

    Vera, Julio; Rath, Oliver; Balsa-Canto, Eva; Banga, Julio R; Kolch, Walter; Wolkenhauer, Olaf

    2010-11-01

    the existence of an intense feedback-loop control of the pathway by the activated ERK that maybe responsible for the damped oscillations we saw in the fraction of activated MEK both in the experiments and simulations. In addition, the model analysis suggested that phosphorylation/deactivation of RKIP during the transient stimulation may have a significant effect on the signalling peaks of both MEK and ERK. This later result suggests that dynamic modulation of signal inhibitors during stimulation may be a regulatory mechanism in ERK signalling and other pathways.

  1. New CMOS Compatible Platforms for Integrated Nonlinear Optical Signal Processing

    CERN Document Server

    Moss, D J

    2014-01-01

    Nonlinear photonic chips have succeeded in generating and processing signals all-optically with performance far superior to that possible electronically - particularly with respect to speed. Although silicon-on-insulator has been the leading platform for nonlinear optics, its high two-photon absorption at telecommunications wavelengths poses a fundamental limitation. This paper reviews some of the recent achievements in CMOS-compatible platforms for nonlinear optics, focusing on amorphous silicon and Hydex glass, highlighting their potential future impact as well as the challenges to achieving practical solutions for many key applications. These material systems have opened up many new capabilities such as on-chip optical frequency comb generation and ultrafast optical pulse generation and measurement.

  2. Recent Advances in Graphene-Assisted Nonlinear Optical Signal Processing

    Directory of Open Access Journals (Sweden)

    Jian Wang

    2016-01-01

    Full Text Available Possessing a variety of remarkable optical, electronic, and mechanical properties, graphene has emerged as an attractive material for a myriad of optoelectronic applications. The wonderful optical properties of graphene afford multiple functions of graphene based polarizers, modulators, transistors, and photodetectors. So far, the main focus has been on graphene based photonics and optoelectronics devices. Due to the linear band structure allowing interband optical transitions at all photon energies, graphene has remarkably large third-order optical susceptibility χ(3, which is only weakly dependent on the wavelength in the near-infrared frequency range. The graphene-assisted four-wave mixing (FWM based wavelength conversions have been experimentally demonstrated. So, we believe that the potential applications of graphene also lie in nonlinear optical signal processing, where the combination of its unique large χ(3 nonlinearities and dispersionless over the wavelength can be fully exploited. In this review article, we give a brief overview of our recent progress in graphene-assisted nonlinear optical device and their applications, including degenerate FWM based wavelength conversion of quadrature phase-shift keying (QPSK signal, phase conjugated wavelength conversion by degenerate FWM and transparent wavelength conversion by nondegenerate FWM, two-input and three-input high-base optical computing, and high-speed gate-tunable terahertz coherent perfect absorption (CPA using a split-ring graphene.

  3. BPSK optical mm-wave signal generation by septupling frequency via a single optical phase modulator

    Science.gov (United States)

    Wu, Peng; Ma, Jianxin

    2016-09-01

    In this paper, we have proposed a novel and simple scheme to generate the BPSK optical millimeter wave (MMW) signal with frequency septupling by using an optical phase modulator (PM) and a wavelength selective switch (WSS). In this scheme, the PM is driven by a radio frequency (RF) BPSK signal at the optimized modulation index of 4.89 to assure the 4th and 3rd-order sidebands have equal amplitudes. An wavelength selective switch (WSS) is used to abstract the -4th and +3rd-order sidebands from the spectrum generated by RF BPSK signal modulating the lightwave to form the BPSK optical MMW signal with frequency septupling the driving RF signal. In these two tones, only the +3rd-order sideband bears the BPSK signal while the -4th-order sideband is unmodulated since the phase information is canceled by the even times multiplication of the phase of BPSK signal. The MMW signal can avoid the pulse walk-off effect and the amplitude fading effect caused by the fiber chromatic dispersion. By adjusting the modulation index to assure the two tones have equal amplitude, the generated optical MMW signal has the maximal opto-electrical conversion efficiency and good transmission performance.

  4. Studies of beam expansion and distributed Bragg reflector lasers for fiber optics and optical signal processing

    Science.gov (United States)

    Garmire, E. M.

    1981-03-01

    Separate studies were performed on beam expansion and on distributed Bragg Reflector (DBR) lasers preliminary to monolithic integration on GaAs substrates. These components are proposed for use in optical signal processing, for fiber optic sources and for high brightness lasers.

  5. Reversible Gating of Plasmonic Coupling for Optical Signal Amplification.

    Science.gov (United States)

    Khoury, Christopher G; Fales, Andrew M; Vo-Dinh, Tuan

    2016-07-20

    Amplification of optical signals is useful for a wide variety of applications, ranging from data signal transmission to chemical sensing and biomedical diagnostics. One such application in chemical sensing is surface-enhanced Raman scattering (SERS), an important technique for increasing the Raman signal using the plasmonic effect of enhanced electromagnetic fields associated with metallic nanostructures. One of the most important limitations of SERS-based amplification is the difficulty to reproducibly control the SERS signal. Here, we describe the design and implementation of a unique hybrid system capable of producing reversible gating of plasmonic coupling for Raman signal amplification. The hybrid system is composed of two subsystems: (1) colloidal magneto-plasmonic nanoparticles for SERS enhancement and (2) a micromagnet substrate with an externally applied magnetic field to modulate the colloidal nanoparticles. For this proof of concept demonstration, the nanoparticles were labeled with a Raman-active dye, and it was shown that the detected SERS signal could be reproducibly modulated by controlling the externally applied magnetic field. The developed system provides a simple, robust, inexpensive, and reusable device for SERS signal modulation. These properties will open up new possibilities for optical signal amplification and gating as well for high-throughput, reproducible SERS detection.

  6. Simultaneous all-optical phase noise mitigation and automatically locked homodyne reception of an incoming QPSK data signal.

    Science.gov (United States)

    Mohajerin-Ariaei, Amirhossein; Ziyadi, Morteza; Almaiman, Ahmed; Cao, Yinwen; Alishahi, Fatemeh; Chitgarha, Mohammad Reza; Fallahpour, Ahmad; Yang, Jeng-Yuan; Bao, Changjing; Liao, Peicheng; Shamee, Bishara; Akasaka, Youichi; Sekiya, Motoyoshi; Touch, Joseph D; Tur, Moshe; Langrock, Carsten; Fejer, Martin M; Willner, Alan E

    2016-10-15

    Simultaneous phase noise mitigation and automatic phase/frequency-locked homodyne reception is demonstrated for a 20-32 Gbaud QPSK signal. A phase quantization function is realized to squeeze the phase noise of the signal by optical wave mixing of the signal, its third-order harmonic, and their corresponding delayed variant conjugates, converting the noisy input into a noise-mitigated signal. In a simultaneous nonlinear process, the noise-mitigated signal is automatically phase- and frequency-locked with a "local" pump laser, avoiding the need for feedback or phase/frequency tracking for homodyne detection. Open eye-diagrams are obtained for in-phase and quadrature-phase components of the signal and ∼2  dB OSNR gain is achieved at BER 10-3.

  7. Feedback effects in optical communication systems: characteristic curve for single-mode InGaAsP lasers.

    Science.gov (United States)

    Brivio, F; Reverdito, C; Sacchi, G; Chiaretti, G; Milani, M

    1992-08-20

    An experimental analysis of InGaAsP injection lasers shows an unexpected decrease of the differential quantum efficiency as a function of injected current when optical power is fed back into the active cavity of a diode inserted into a long transmission line. To investigate the response of laser diodes to optical feedback, we base our analysis on a microscopic model, resulting in a set of coupled equations that include the microscopic parameters that characterize the material and the device. This description takes into account the nonlinear dependence of the interband carrier lifetime on the level of optical feedback. Good agreement between the analytical description and experimental data is obtained for threshold current and differential quantum efficiency as functions of the feedback ratio.

  8. Detection and Correction of Under-/Overexposed Optical Soundtracks by Coupling Image and Audio Signal Processing

    Directory of Open Access Journals (Sweden)

    Etienne Decenciere

    2008-10-01

    Full Text Available Film restoration using image processing, has been an active research field during the last years. However, the restoration of the soundtrack has been mainly performed in the sound domain, using signal processing methods, despite the fact that it is recorded as a continuous image between the images of the film and the perforations. While the very few published approaches focus on removing dust particles or concealing larger corrupted areas, no published works are devoted to the restoration of soundtracks degraded by substantial underexposure or overexposure. Digital restoration of optical soundtracks is an unexploited application field and, besides, scientifically rich, because it allows mixing both image and signal processing approaches. After introducing the principles of optical soundtrack recording and playback, this contribution focuses on our first approaches to detect and cancel the effects of under and overexposure. We intentionally choose to get a quantification of the effect of bad exposure in the 1D audio signal domain instead of 2D image domain. Our measurement is sent as feedback value to an image processing stage where the correction takes place, building up a “digital image and audio signal” closed loop processing. The approach is validated on both simulated alterations and real data.

  9. Detection and Correction of Under-/Overexposed Optical Soundtracks by Coupling Image and Audio Signal Processing

    Science.gov (United States)

    Taquet, Jonathan; Besserer, Bernard; Hassaine, Abdelali; Decenciere, Etienne

    2008-12-01

    Film restoration using image processing, has been an active research field during the last years. However, the restoration of the soundtrack has been mainly performed in the sound domain, using signal processing methods, despite the fact that it is recorded as a continuous image between the images of the film and the perforations. While the very few published approaches focus on removing dust particles or concealing larger corrupted areas, no published works are devoted to the restoration of soundtracks degraded by substantial underexposure or overexposure. Digital restoration of optical soundtracks is an unexploited application field and, besides, scientifically rich, because it allows mixing both image and signal processing approaches. After introducing the principles of optical soundtrack recording and playback, this contribution focuses on our first approaches to detect and cancel the effects of under and overexposure. We intentionally choose to get a quantification of the effect of bad exposure in the 1D audio signal domain instead of 2D image domain. Our measurement is sent as feedback value to an image processing stage where the correction takes place, building up a "digital image and audio signal" closed loop processing. The approach is validated on both simulated alterations and real data.

  10. Series-nonuniform rational B-spline signal feedback: From chaos to any embedded periodic orbit or target point

    Science.gov (United States)

    Shao, Chenxi; Xue, Yong; Fang, Fang; Bai, Fangzhou; Yin, Peifeng; Wang, Binghong

    2015-07-01

    The self-controlling feedback control method requires an external periodic oscillator with special design, which is technically challenging. This paper proposes a chaos control method based on time series non-uniform rational B-splines (SNURBS for short) signal feedback. It first builds the chaos phase diagram or chaotic attractor with the sampled chaotic time series and any target orbit can then be explicitly chosen according to the actual demand. Second, we use the discrete timing sequence selected from the specific target orbit to build the corresponding external SNURBS chaos periodic signal, whose difference from the system current output is used as the feedback control signal. Finally, by properly adjusting the feedback weight, we can quickly lead the system to an expected status. We demonstrate both the effectiveness and efficiency of our method by applying it to two classic chaotic systems, i.e., the Van der Pol oscillator and the Lorenz chaotic system. Further, our experimental results show that compared with delayed feedback control, our method takes less time to obtain the target point or periodic orbit (from the starting point) and that its parameters can be fine-tuned more easily.

  11. Series-nonuniform rational B-spline signal feedback: From chaos to any embedded periodic orbit or target point

    Energy Technology Data Exchange (ETDEWEB)

    Shao, Chenxi, E-mail: cxshao@ustc.edu.cn; Xue, Yong; Fang, Fang; Bai, Fangzhou [Department of Computer Science and Technology, University of Science and Technology of China, Hefei 230027 (China); Yin, Peifeng [Department of Computer Science and Engineering, Pennsylvania State University, State College, Pennsylvania 16801 (United States); Wang, Binghong [Department of Modern Physics, University of Science and Technology of China, Hefei 230026 (China)

    2015-07-15

    The self-controlling feedback control method requires an external periodic oscillator with special design, which is technically challenging. This paper proposes a chaos control method based on time series non-uniform rational B-splines (SNURBS for short) signal feedback. It first builds the chaos phase diagram or chaotic attractor with the sampled chaotic time series and any target orbit can then be explicitly chosen according to the actual demand. Second, we use the discrete timing sequence selected from the specific target orbit to build the corresponding external SNURBS chaos periodic signal, whose difference from the system current output is used as the feedback control signal. Finally, by properly adjusting the feedback weight, we can quickly lead the system to an expected status. We demonstrate both the effectiveness and efficiency of our method by applying it to two classic chaotic systems, i.e., the Van der Pol oscillator and the Lorenz chaotic system. Further, our experimental results show that compared with delayed feedback control, our method takes less time to obtain the target point or periodic orbit (from the starting point) and that its parameters can be fine-tuned more easily.

  12. Negative feedback regulation of auxin signaling by ATHB8/ACL5-BUD2 transcription module.

    Science.gov (United States)

    Baima, Simona; Forte, Valentina; Possenti, Marco; Peñalosa, Andrés; Leoni, Guido; Salvi, Sergio; Felici, Barbara; Ruberti, Ida; Morelli, Giorgio

    2014-06-01

    The role of auxin as main regulator of vascular differentiation is well established, and a direct correlation between the rate of xylem differentiation and the amount of auxin reaching the (pro)cambial cells has been proposed. It has been suggested that thermospermine produced by ACAULIS5 (ACL5) and bushy and dwarf2 (BUD2) is one of the factors downstream to auxin contributing to the regulation of this process in Arabidopsis. Here, we provide an in-depth characterization of the mechanism through which ACL5 modulates xylem differentiation. We show that an increased level of ACL5 slows down xylem differentiation by negatively affecting the expression of homeodomain-leucine zipper (HD-ZIP) III and key auxin signaling genes. This mechanism involves the positive regulation of thermospermine biosynthesis by the HD-ZIP III protein Arabidopsis thaliana homeobox8 tightly controlling the expression of ACL5 and BUD2. In addition, we show that the HD-ZIP III protein REVOLUTA contributes to the increased leaf vascularization and long hypocotyl phenotype of acl5 likely by a direct regulation of auxin signaling genes such as like auxin resistant2 (LAX2) and LAX3. We propose that proper formation and differentiation of xylem depend on a balance between positive and negative feedback loops operating through HD-ZIP III genes.

  13. The digital traces of bubbles: feedback cycles between socio-economic signals in the Bitcoin economy

    CERN Document Server

    Garcia, David; Mavrodiev, Pavlin; Perony, Nicolas

    2014-01-01

    What is the role of social interactions in the creation of price bubbles? Answering this question requires obtaining collective behavioural traces generated by the activity of a large number of actors. Digital currencies offer a unique possibility to measure socio-economic signals from such digital traces. Here, we focus on Bitcoin, the most popular cryptocurrency. Bitcoin has experienced periods of rapid increase in exchange rates (price) followed by sharp decline; we hypothesise that these fluctuations are largely driven by the interplay between different social phenomena. We thus quantify four socio-economic signals about Bitcoin from large data sets: price on on-line exchanges, volume of word-of-mouth communication in on-line social media, volume of information search, and user base growth. By using vector autoregression, we identify two positive feedback loops that lead to price bubbles in the absence of exogenous stimuli: one driven by word of mouth, and the other by new Bitcoin adopters. We also observ...

  14. Temperature feedback control for long-term carrier-envelope phase locking

    Science.gov (United States)

    Chang, Zenghu [Manhattan, KS; Yun, Chenxia [Manhattan, KS; Chen, Shouyuan [Manhattan, KS; Wang, He [Manhattan, KS; Chini, Michael [Manhattan, KS

    2012-07-24

    A feedback control module for stabilizing a carrier-envelope phase of an output of a laser oscillator system comprises a first photodetector, a second photodetector, a phase stabilizer, an optical modulator, and a thermal control element. The first photodetector may generate a first feedback signal corresponding to a first portion of a laser beam from an oscillator. The second photodetector may generate a second feedback signal corresponding to a second portion of the laser beam filtered by a low-pass filter. The phase stabilizer may divide the frequency of the first feedback signal by a factor and generate an error signal corresponding to the difference between the frequency-divided first feedback signal and the second feedback signal. The optical modulator may modulate the laser beam within the oscillator corresponding to the error signal. The thermal control unit may change the temperature of the oscillator corresponding to a signal operable to control the optical modulator.

  15. Silicon Nanowires for All-Optical Signal Processing in Optical Communication

    DEFF Research Database (Denmark)

    Pu, Minhao; Hu, Hao; Ji, Hua;

    2012-01-01

    to the large mode mismatch and index mismatch. Both end-coupling and grating-coupling solution utilizing nano-structures were demonstrated with optimized coupling efficiencies, which make the silicon on-chip nanowire devices more practical for real optical communication systems.......Silicon (Si), the second most abundant element on earth, has dominated in microelectronics for many decades. It can also be used for photonic devices due to its transparency in the range of optical telecom wavelengths which will enable a platform for a monolithic integration of optics...... process. In the last four years, we investigated and demonstrated different ultra-fast all-optical nonlinear signal processing applications in silicon nanowires for optical time domain multiplexing (OTDM) systems, including wavelength conversion, signal regeneration, ultra-fast waveform sampling...

  16. Demultiplexing of OTDM-DPSK signals based on a single semiconductor optical amplifier and optical filtering

    DEFF Research Database (Denmark)

    Xu, Jing; Ding, Yunhong; Peucheret, Christophe

    2011-01-01

    We propose and demonstrate the use of a single semiconductor optical amplifier (SOA) and optical filtering to time demultiplex tributaries from an optical time division multiplexing-differential phase shift keying (OTDM-DPSK) signal. The scheme takes advantage of the fact that phase variations...... as the bit period at 80 Gbit=s. Large dynamic ranges for the input power and SOA current are experimentally demonstrated. The scheme is expected to be scalable toward higher bit rates. © 2011 Optical Society of America....

  17. Traffic analysis and signal processing in optical packet switched networks

    DEFF Research Database (Denmark)

    Fjelde, Tina

    2002-01-01

    Gbit/s demultiplexing and 2x10 to 20 Gbit/s multiplexing. Lastly, the IWC’s capabilities as an optical logic gate for enabling more complex signal processing are demonstrated and four applications hereof are discussed. Logic OR and AND are verified in full at 10 Gbit/s using PRBS sequences coupled......This thesis focuses on functionalities that are important for the realisation of future all-optical packet switched networks, and which may be implemented using the interferometric wavelength converter. The European IST research project DAVID, with the aim of demonstrating the feasibility of a Tbit....../s optical packet switched network exploiting the best of optics and electronics, is used as a thread throughout the thesis. An overview of the DAVID network architecture is given, focussing on the MAN and WAN architecture as well as the MPLS-based network hierarchy. Subsequently, the traffic performance...

  18. Effects of a feedback signal in a computer mouse on movement behaviour, muscle load, productivity, comfort and user friendliness

    NARCIS (Netherlands)

    Korte, E.M. de; Kraker, H. de; Bongers, P.M.; Lingen, P. van

    2008-01-01

    To study the effects of a tactile feedback signal in a computer mouse on reduction of hovering behaviour and consequently on changes in muscle load, productivity, comfort and user friendliness, a comparative, experimental study with repeated measures was conducted. Fifteen subjects performed five

  19. Effects of a feedback signal in a computer mouse on movement behaviour, muscle load, productivity, comfort and user friendliness

    NARCIS (Netherlands)

    Korte, E.M. de; Kraker, H. de; Bongers, P.M.; Lingen, P. van

    2008-01-01

    To study the effects of a tactile feedback signal in a computer mouse on reduction of hovering behaviour and consequently on changes in muscle load, productivity, comfort and user friendliness, a comparative, experimental study with repeated measures was conducted. Fifteen subjects performed five tr

  20. Proton feedback mediates the cascade of color-opponent signals onto H3 horizontal cells in goldfish retina.

    Science.gov (United States)

    Kamiji, Nilton L; Yamamoto, Kazunori; Hirasawa, Hajime; Yamada, Masahiro; Usui, Shiro; Kurokawa, Makoto

    2012-04-01

    It has been postulated that horizontal cells (HCs) send feedback signals onto cones via a proton feedback mechanism, which generates the center-surround receptive field of bipolar cells, and color-opponent signals in many non-mammalian vertebrates. Here we used a strong pH buffer, HEPES, to reduce extracellular proton concentration changes and so determine whether protons mediate color-opponent signals in goldfish H3 (triphasic) HCs. Superfusion with 10mM HEPES-fortified saline elicited depolarization of H3 HCs' dark membrane potential and enhanced hyperpolarizing responses to blue stimuli, but suppressed both depolarization by yellow and orange and hyperpolarization by red stimuli. The response components suppressed by HEPES resembled the inverse of spectral responses of H2 (biphasic) HCs. These results are consistent with the Stell-Lightfoot cascade model, in which the HEPES-suppressed component of H3 HCs was calculated using light responses recorded experimentally in H1 (monophasic) and H2 HCs. Selective suppression of long- or long-+middle-wavelength cone signals by long-wavelength background enhanced the responses to short-wavelength stimuli. These results suggest that HEPES inhibited color opponent signals in H3 HCs, in which the source of opponent-color signals is primarily a feedback from H2 HCs and partly from H1 HCs onto short-wavelength cones, probably mediated by protons.

  1. A novel approach to photonic generate microwave signals based on optical injection locking and four-wave mixing

    Science.gov (United States)

    Zhu, Huatao; Wang, Rong; Xiang, Peng; Pu, Tao; Fang, Tao; Zheng, Jilin; Li, Yuandong

    2017-10-01

    In this paper, a novel approach for photonic generation of microwave signals based on frequency multiplication using an injected distributed-feedback (DFB) semiconductor laser is proposed and demonstrated by a proof-of-concept experiment. The proposed system is mainly made up of a dual-parallel Mach-Zehnder modulator (DPMZM) and an injected DFB laser. By properly setting the bias voltage of the DPMZM, ±2-order sidebands with carrier suppression are generated, which are then injected into the slave laser. Due to the optical sideband locking and four-wave mixing (FWM) nonlinearity in the slave laser, new sidebands are generated. Then these sidebands are sent to an optical notch filter where all the undesired sidebands are removed. Finally, after photodetector detection, frequency multiplied microwave signals can be generated. Thanks to the flexibility of the optical sideband locking and FWM, frequency octupling, 12-tupling, 14-tupling and 16-tupling can be obtained.

  2. Optical Feedback Interferometry for Velocity Measurement of Parallel Liquid-Liquid Flows in a Microchannel

    Directory of Open Access Journals (Sweden)

    Evelio E. Ramírez-Miquet

    2016-08-01

    Full Text Available Optical feedback interferometry (OFI is a compact sensing technique with recent implementation for flow measurements in microchannels. We propose implementing OFI for the analysis at the microscale of multiphase flows starting with the case of parallel flows of two immiscible fluids. The velocity profiles in each phase were measured and the interface location estimated for several operating conditions. To the authors knowledge, this sensing technique is applied here for the first time to multiphase flows. Theoretical profiles issued from a model based on the Couette viscous flow approximation reproduce fairly well the experimental results. The sensing system and the analysis presented here provide a new tool for studying more complex interactions between immiscible fluids (such as liquid droplets flowing in a microchannel.

  3. Compensation of focal plane image motion perturbations with optical correlator in feedback loop

    Science.gov (United States)

    Janschek, Klaus; Tchernykh, Valerij; Dyblenko, Serguei; Flandin, Gregory; Harnisch, Bernd

    2004-11-01

    The paper presents a concept of a smart pushbroom imaging system with compensation of attitude instability effects. The compensation is performed by active opto-mechatronic stabilization of the focal plane image motion in a closed loop system with visual feedback on base of an auxiliary matrix image sensor and an onboard optical correlator. In this way the effects of the attitude instability, vibrations and micro shocks can be neutralized, the image quality improved and the requirements to satellite attitude stability reduced. To prove the feasibility and to estimate the effectiveness of the image motion stabilization, a performance model of the smart imaging system has been developed and a simulation experiment has been carried out. The description of the performance model and the results of the simulation experiment are also given.

  4. Chaos synchronization based on a continuous chaos control method in semiconductor lasers with optical feedback.

    Science.gov (United States)

    Murakami, A; Ohtsubo, J

    2001-06-01

    Chaos synchronization using a continuous chaos control method was studied in two identical chaotic laser systems consisting of semiconductor lasers and optical feedback from an external mirror. Numerical calculations for rate equations indicate that the stability of chaos synchronization depends significantly on the external mirror position. We performed a linear stability analysis for the rate equations. Our results show that the stability of the synchronization is much influenced by the mode interaction between the relaxation oscillation frequency of the semiconductor laser and the external cavity frequency. Due to this interaction, an intensive mode competition between the two frequencies destroys the synchronization, but stable synchronization can be achieved when the mode competition is very weak.

  5. Bifurcation analysis of a semiconductor laser with saturable absorber and delayed optical feedback

    CERN Document Server

    Terrien, Soizic; Broderick, Neil G R

    2016-01-01

    Semiconductor lasers exhibit a wealth of dynamics, from emission of a constant beam of light, to periodic oscillations and excitability. Self-pulsing regimes, where the laser periodically releases a short pulse of light, are particularly interesting for many applications, from material science to telecommunications. Self-pulsing regimes need to produce pulses very regularly and, as such, they are also known to be particularly sensitive to perturbations, such as noise or light injection. We investigate the effect of delayed optical feedback on the dynamics of a self-pulsing semiconductor laser with saturable absorber (SLSA). More precisely, we consider the Yamada model with delay -- a system of three delay-differential equations (DDEs) for two slow and one fast variable -- which has been shown to reproduce accurately self-pulsing features as observed in SLSA experimentally. This model is also of broader interest because it is quite closely related to mathematical models of other self-pulsing systems, such as e...

  6. Analog signal processing for optical coherence imaging systems

    Science.gov (United States)

    Xu, Wei

    Optical coherence tomography (OCT) and optical coherence microscopy (OCM) are non-invasive optical coherence imaging techniques, which enable micron-scale resolution, depth resolved imaging capability. Both OCT and OCM are based on Michelson interferometer theory. They are widely used in ophthalmology, gastroenterology and dermatology, because of their high resolution, safety and low cost. OCT creates cross sectional images whereas OCM obtains en face images. In this dissertation, the design and development of three increasingly complicated analog signal processing (ASP) solutions for optical coherence imaging are presented. The first ASP solution was implemented for a time domain OCT system with a Rapid Scanning Optical Delay line (RSOD)-based optical signal modulation and logarithmic amplifier (Log amp) based demodulation. This OCT system can acquire up to 1600 A-scans per second. The measured dynamic range is 106dB at 200A-scan per second. This OCT signal processing electronics includes an off-the-shelf filter box with a Log amp circuit implemented on a PCB board. The second ASP solution was developed for an OCM system with synchronized modulation and demodulation and compensation for interferometer phase drift. This OCM acquired micron-scale resolution, high dynamic range images at acquisition speeds up to 45,000 pixels/second. This OCM ASP solution is fully custom designed on a perforated circuit board. The third ASP solution was implemented on a single 2.2 mm x 2.2 mm complementary metal oxide semiconductor (CMOS) chip. This design is expandable to a multiple channel OCT system. A single on-chip CMOS photodetector and ASP channel was used for coherent demodulation in a time domain OCT system. Cross-sectional images were acquired with a dynamic range of 76dB (limited by photodetector responsivity). When incorporated with a bump-bonded InGaAs photodiode with higher responsivity, the expected dynamic range is close to 100dB.

  7. Clustering and negative feedback by endocytosis in planar cell polarity signaling is modulated by ubiquitinylation of prickle.

    Science.gov (United States)

    Cho, Bomsoo; Pierre-Louis, Gandhy; Sagner, Andreas; Eaton, Suzanne; Axelrod, Jeffrey D

    2015-05-01

    The core components of the planar cell polarity (PCP) signaling system, including both transmembrane and peripheral membrane associated proteins, form asymmetric complexes that bridge apical intercellular junctions. While these can assemble in either orientation, coordinated cell polarization requires the enrichment of complexes of a given orientation at specific junctions. This might occur by both positive and negative feedback between oppositely oriented complexes, and requires the peripheral membrane associated PCP components. However, the molecular mechanisms underlying feedback are not understood. We find that the E3 ubiquitin ligase complex Cullin1(Cul1)/SkpA/Supernumerary limbs(Slimb) regulates the stability of one of the peripheral membrane components, Prickle (Pk). Excess Pk disrupts PCP feedback and prevents asymmetry. We show that Pk participates in negative feedback by mediating internalization of PCP complexes containing the transmembrane components Van Gogh (Vang) and Flamingo (Fmi), and that internalization is activated by oppositely oriented complexes within clusters. Pk also participates in positive feedback through an unknown mechanism promoting clustering. Our results therefore identify a molecular mechanism underlying generation of asymmetry in PCP signaling.

  8. Enhancement of Second-Order Nonlinear-Optical Signals by Optical Stimulation

    Science.gov (United States)

    Goodman, A. J.; Tisdale, W. A.

    2015-05-01

    Second-order nonlinear optical interactions such as sum- and difference-frequency generation are widely used for bioimaging and as selective probes of interfacial environments. However, inefficient nonlinear optical conversion often leads to poor signal-to-noise ratio and long signal acquisition times. Here, we demonstrate the dramatic enhancement of weak second-order nonlinear optical signals via stimulated sum- and difference-frequency generation. We present a conceptual framework to quantitatively describe the interaction and show that the process is highly sensitive to the relative optical phase of the stimulating field. To emphasize the utility of the technique, we demonstrate stimulated enhancement of second harmonic generation (SHG) from bovine collagen-I fibrils. Using a stimulating pulse fluence of only 3 nJ /cm2 , we obtain an SHG enhancement >104 relative to the spontaneous signal. The stimulation enhancement is greatest in situations where spontaneous signals are the weakest—such as low laser power, small sample volume, and weak nonlinear susceptibility—emphasizing the potential for this technique to improve signal-to-noise ratios in biological imaging and interfacial spectroscopy.

  9. Measurements of the linewidth enhancement factor of mid-infrared quantum cascade lasers by different optical feedback techniques

    Directory of Open Access Journals (Sweden)

    L. Jumpertz

    2016-01-01

    Full Text Available Precise knowledge of the linewidth enhancement factor of a semiconductor laser under actual operating conditions is of prime importance since this parameter dictates various phenomena such as linewidth broadening or optical nonlinearities enhancement. The above-threshold linewidth enhancement factor of a mid-infrared quantum cascade laser structure operated at 10∘C is determined experimentally using two different methods based on optical feedback. Both Fabry-Perot and distributed feedback quantum cascade lasers based on the same active area design are studied, the former by following the wavelength shift as a function of the feedback strength and the latter by self-mixing interferometry. The results are consistent and unveil a clear pump current dependence of the linewidth enhancement factor, with values ranging from 0.8 to about 3.

  10. Measurements of the linewidth enhancement factor of mid-infrared quantum cascade lasers by different optical feedback techniques

    Energy Technology Data Exchange (ETDEWEB)

    Jumpertz, L., E-mail: louise.jumpertz@telecom-paristech.fr [Université Paris-Saclay, Télécom ParisTech, CNRS LTCI, 46 rue Barrault, F-75013 Paris (France); MirSense, 8 avenue de la Vauve, F-91120 Palaiseau (France); Michel, F.; Pawlus, R.; Elsässer, W. [Technische Universität Darmstadt, Schlossgartenstr. 7, D-64289 Darmstadt (Germany); Schires, K. [Université Paris-Saclay, Télécom ParisTech, CNRS LTCI, 46 rue Barrault, F-75013 Paris (France); Carras, M. [MirSense, 8 avenue de la Vauve, F-91120 Palaiseau (France); Grillot, F. [Université Paris-Saclay, Télécom ParisTech, CNRS LTCI, 46 rue Barrault, F-75013 Paris (France); also with Center for High Technology Materials, University of New-Mexico, 1313 Goddard SE, Albuquerque, NM (United States)

    2016-01-15

    Precise knowledge of the linewidth enhancement factor of a semiconductor laser under actual operating conditions is of prime importance since this parameter dictates various phenomena such as linewidth broadening or optical nonlinearities enhancement. The above-threshold linewidth enhancement factor of a mid-infrared quantum cascade laser structure operated at 10{sup ∘}C is determined experimentally using two different methods based on optical feedback. Both Fabry-Perot and distributed feedback quantum cascade lasers based on the same active area design are studied, the former by following the wavelength shift as a function of the feedback strength and the latter by self-mixing interferometry. The results are consistent and unveil a clear pump current dependence of the linewidth enhancement factor, with values ranging from 0.8 to about 3.

  11. High-speed optical coherence tomography signal processing on GPU

    Energy Technology Data Exchange (ETDEWEB)

    Li Xiqi; Shi Guohua; Zhang Yudong, E-mail: lixiqi@yahoo.cn [Laboratory on Adaptive Optics, Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu 610209 (China)

    2011-01-01

    The signal processing speed of spectral domain optical coherence tomography (SD-OCT) has become a bottleneck in many medical applications. Recently, a time-domain interpolation method was proposed. This method not only gets a better signal-to noise ratio (SNR) but also gets a faster signal processing time for the SD-OCT than the widely used zero-padding interpolation method. Furthermore, the re-sampled data is obtained by convoluting the acquired data and the coefficients in time domain. Thus, a lot of interpolations can be performed concurrently. So, this interpolation method is suitable for parallel computing. An ultra-high optical coherence tomography signal processing can be realized by using graphics processing unit (GPU) with computer unified device architecture (CUDA). This paper will introduce the signal processing steps of SD-OCT on GPU. An experiment is performed to acquire a frame SD-OCT data (400A-linesx2048 pixel per A-line) and real-time processed the data on GPU. The results show that it can be finished in 6.208 milliseconds, which is 37 times faster than that on Central Processing Unit (CPU).

  12. Chronic Psychosocial Stress and Negative Feedback Inhibition: Enhanced Hippocampal Glucocorticoid Signaling despite Lower Cytoplasmic GR Expression.

    Science.gov (United States)

    Füchsl, Andrea M; Reber, Stefan O

    2016-01-01

    Chronic subordinate colony housing (CSC), a pre-clinically validated mouse model for chronic psychosocial stress, results in increased basal and acute stress-induced plasma adrenocorticotropic hormone (ACTH) levels. We assessed CSC effects on hippocampal glucocorticoid (GC) receptor (GR), mineralocorticoid receptor (MR), and FK506 binding protein (FKBP51) expression, acute heterotypic stressor-induced GR translocation, as well as GC effects on gene expression and cell viability in isolated hippocampal cells. CSC mice showed decreased GR mRNA and cytoplasmic protein levels compared with single-housed control (SHC) mice. Basal and acute stress-induced nuclear GR protein expression were comparable between CSC and SHC mice, as were MR and FKBP51 mRNA and/or cytoplasmic protein levels. In vitro the effect of corticosterone (CORT) on hippocampal cell viability and gene transcription was more pronounced in CSC versus SHC mice. In summary, CSC mice show an, if at all, increased hippocampal GC signaling capacity despite lower cytoplasmic GR protein expression, making negative feedback deficits in the hippocampus unlikely to contribute to the increased ACTH drive following CSC.

  13. Ultrafast optical signal processing on silicon-based platforms

    Science.gov (United States)

    Tan, Dawn T. H.

    2016-03-01

    The development of silicon - based photonic components and systems has advanced tremendously over the last decade, largely for applications in optical interconnects. The role of silicon - based platforms for both linear and nonlinear optics remains highly pertinent because of their ability to be integrated with CMOS - based electronics. In this paper, we present recent research progress pertaining to ultrafast optical signal processing on silicon - based platforms. Advances in on - chip multiplexing strategies with the potential for meeting 200GHz dense wavelength division multiplexing standards across the C - and L - bands will be discussed. In addition, the development of a silicon - based nonlinear optics platform with high nonlinear figures of merit will be presented. Nonlinear optical devices fabricated from the developed platform possess nonlinear parameters 500 times larger than that in silicon nitride waveguides, while possessing negligible nonlinear losses at 1.55μm. Ultra - broadband, low power nonlinear wavelength generation using these devices, as well as their potential for realizing advanced light sources for optical interconnect - based applications will be presented.

  14. Automatic irradiation control by an optical feedback technique for selective retina treatment (SRT) in a rabbit model

    Science.gov (United States)

    Seifert, Eric; Roh, Young-Jung; Fritz, Andreas; Park, Young Gun; Kang, Seungbum; Theisen-Kunde, Dirk; Brinkmann, Ralf

    2013-06-01

    Selective Retina Therapy (SRT) targets the Retinal Pigment Epithelium (RPE) without effecting neighboring layers as the photoreceptors or the choroid. SRT related RPE defects are ophthalmoscopically invisible. Owing to this invisibility and the variation of the threshold radiant exposure for RPE damage the treating physician does not know whether the treatment was successful or not. Thus measurement techniques enabling a correct dosing are a demanded element in SRT devices. The acquired signal can be used for monitoring or automatic irradiation control. Existing monitoring techniques are based on the detection of micro-bubbles. These bubbles are the origin of RPE cell damage for pulse durations in the ns and μs time regime 5μs. The detection can be performed by optical or acoustical approaches. Monitoring based on an acoustical approach has already been used to study the beneficial effects of SRT on diabetic macula edema and central serous retinopathy. We have developed a first real time feedback technique able to detect micro-bubble induced characteristics in the backscattered laser light fast enough to cease the laser irradiation within a burst. Therefore the laser energy within a burst of at most 30 pulses is increased linearly with every pulse. The laser irradiation is ceased as soon as micro-bubbles are detected. With this automatic approach it was possible to observe invisible lesions, an intact photoreceptor layer and a reconstruction of the RPE within one week.

  15. Ultrashort Optical Pulse Propagation in terms of Analytic Signal

    Directory of Open Access Journals (Sweden)

    Sh. Amiranashvili

    2011-01-01

    Full Text Available We demonstrate that ultrashort optical pulses propagating in a nonlinear dispersive medium are naturally described through incorporation of analytic signal for the electric field. To this end a second-order nonlinear wave equation is first simplified using a unidirectional approximation. Then the analytic signal is introduced, and all nonresonant nonlinear terms are eliminated. The derived propagation equation accounts for arbitrary dispersion, resonant four-wave mixing processes, weak absorption, and arbitrary pulse duration. The model applies to the complex electric field and is independent of the slowly varying envelope approximation. Still the derived propagation equation posses universal structure of the generalized nonlinear Schrödinger equation (NSE. In particular, it can be solved numerically with only small changes of the standard split-step solver or more complicated spectral algorithms for NSE. We present exemplary numerical solutions describing supercontinuum generation with an ultrashort optical pulse.

  16. Multi-functional optical signal processing using optical spectrum control circuit

    Science.gov (United States)

    Hayashi, Shuhei; Ikeda, Tatsuhiko; Mizuno, Takayuki; Takahashi, Hiroshi; Tsuda, Hiroyuki

    2015-02-01

    Processing ultra-fast optical signals without optical/electronic conversion is in demand and time-to-space conversion has been proposed as an effective solution. We have designed and fabricated an arrayed-waveguide grating (AWG) based optical spectrum control circuit (OSCC) using silica planar lightwave circuit (PLC) technology. This device is composed of an AWG, tunable phase shifters and a mirror. The principle of signal processing is to spatially decompose the signal's frequency components by using the AWG. Then, the phase of each frequency component is controlled by the tunable phase shifters. Finally, the light is reflected back to the AWG by the mirror and synthesized. Amplitude of each frequency component can be controlled by distributing the power to high diffraction order light. The spectral controlling range of the OSCC is 100 GHz and its resolution is 1.67 GHz. This paper describes equipping the OSCC with optical coded division multiplex (OCDM) encoder/decoder functionality. The encoding principle is to apply certain phase patterns to the signal's frequency components and intentionally disperse the signal. The decoding principle is also to apply certain phase patterns to the frequency components at the receiving side. If the applied phase pattern compensates the intentional dispersion, the waveform is regenerated, but if the pattern is not appropriate, the waveform remains dispersed. We also propose an arbitrary filter function by exploiting the OSCC's amplitude and phase control attributes. For example, a filtered optical signal transmitted through multiple optical nodes that use the wavelength multiplexer/demultiplexer can be equalized.

  17. Absolute frequency synthesis of pulsed coherent light waves through phase-modulation active optical feedback.

    Science.gov (United States)

    Shimizu, K; Horiguchi, T; Koyamada, Y

    1996-11-15

    A novel method for the broadband absolute frequency synthesis of pulsed coherent lightwaves is demonstrated. It is based on pulse recirculation around an active optical feedback ring containing a delay-line fiber, an external phase modulator, an acousto-optic frequency shifter (AOFS), and a high-finesse Fabry-Perot étalon. The modulation frequency F(M) and the frequency shift F(AO) that are due to AOFS are designed so that their sum or difference equals the free-spectral range of the étalon and F(AO) is set at larger than the half-width at full maximum of its resonant peaks. If one of the peak frequencies is tuned to the frequency of the initial pulse, the frequency of the recirculating pulse jumps to the next peak for each round trip. In the experiment the absolute frequency is synthesized over a frequency span of 700 GHz around the initial stabilized frequency of the master laser.

  18. Linear Amplification of Optical Signal in Coupled Photonic Crystal Waveguides

    CERN Document Server

    Jandieri, Vakhtang

    2015-01-01

    We introduce a weakly coupled photonic crystal waveguide as a promising and realistic model for all-optical amplification. A symmetric pillar type coupled photonic crystal waveguide consisting of dielectric rods periodically distributed in a free space is proposed as all-optical amplifier. Using the unique features of the photonic crystals to control and guide the light, we have properly chosen the frequency at which only one mode (odd mode) becomes the propagating mode in the coupled photonic crystal waveguide, whereas another mode (even mode) is completely reflected from the guiding structure. Under this condition, the all-optical amplification is fully realized. The amplification coefficient for the continuous signal and the Gaussian pulse is calculated.

  19. Embodiment of Learning in Electro-Optical Signal Processors

    Science.gov (United States)

    Hermans, Michiel; Antonik, Piotr; Haelterman, Marc; Massar, Serge

    2016-09-01

    Delay-coupled electro-optical systems have received much attention for their dynamical properties and their potential use in signal processing. In particular it has recently been demonstrated, using the artificial intelligence algorithm known as reservoir computing, that photonic implementations of such systems solve complex tasks such as speech recognition. Here we show how the backpropagation algorithm can be physically implemented on the same electro-optical delay-coupled architecture used for computation with only minor changes to the original design. We find that, compared when the backpropagation algorithm is not used, the error rate of the resulting computing device, evaluated on three benchmark tasks, decreases considerably. This demonstrates that electro-optical analog computers can embody a large part of their own training process, allowing them to be applied to new, more difficult tasks.

  20. Intrinsic optical signal imaging of retinal physiology: a review

    Science.gov (United States)

    Yao, Xincheng; Wang, Benquan

    2015-09-01

    Intrinsic optical signal (IOS) imaging promises to be a noninvasive method for high-resolution examination of retinal physiology, which can advance the study and diagnosis of eye diseases. While specialized optical instruments are desirable for functional IOS imaging of retinal physiology, in depth understanding of multiple IOS sources in the complex retinal neural network is essential for optimizing instrument designs. We provide a brief overview of IOS studies and relationships in rod outer segment suspensions, isolated retinas, and intact eyes. Recent developments of line-scan confocal and functional optical coherence tomography (OCT) instruments have allowed in vivo IOS mapping of photoreceptor physiology. Further improvements of the line-scan confocal and functional OCT systems may provide a feasible solution to pursue functional IOS mapping of human photoreceptors. Some interesting IOSs have already been detected in inner retinal layers, but better development of the IOS instruments and software algorithms is required to achieve optimal physiological assessment of inner retinal neurons.

  1. Optical notch filter design based on digital signal processing

    Institute of Scientific and Technical Information of China (English)

    GUO Sen; ZHANG Juan; LI Xue

    2011-01-01

    Based on digital signal processing theory, a novel method of designing optical notch filter is proposed for Mach-Zehnder interferometer with cascaded optical fiber rings coupled structure. The method is simple and effective, and it can be used to implement the designing of the optical notch filter which has arbitrary number of notch points in one free spectrum range (FSR). A design example of notch filter based on cascaded single-fiber-rings is given. On this basis, an improved cascaded double-fiber-rings structure is presented to eliminate the effect of phase shift caused by the single-fiber-ring structure. This new structure can improve the stability and applicability of system. The change of output intensity spectrum is finally investigated for each design parameter and the tuning characteristics of the notch filter are also discussed.

  2. Coherent optical array receiver for PPM signals under atmospheric turbulence

    Science.gov (United States)

    Munoz Fernandez, Michela

    The performance of a coherent free-space optical communications system operating in the presence of turbulence is investigated. Maximum Likelihood Detection techniques are employed to optimally detect Pulse Position Modulated signals with a focal-plane detector array and to reconstruct the turbulence-degraded signals. Laboratory equipment and experimental setup used to carry out these experiments at the Jet Propulsion Laboratory are described. The key components include two lasers operating at 1064 nm wavelength for use with coherent detection, a 16 element (4 X 4) InGaAs focal-plane detector array, and a data-acquisition and signal-processing assembly needed to sample and collect the data and analyze the results. The detected signals are combined using the least-mean-square (LMS) algorithm. In the first part of the experimental results we show convergence of the algorithm for experimentally obtained signal tones in the presence of atmospheric turbulence. The second part of the experimental results shows adaptive combining of experimentally obtained heterodyned pulse position modulated (PPM) signals with pulse-to-pulse coherence in the presence of simulated spatial distortions resembling atmospheric turbulence. The adaptively combined PPM signals are phased up via an LMS algorithm suitably optimized to operate with PPM in the presence of additive shot noise. A convergence analysis of the algorithm is presented, and results with both computer-simulated and experimentally obtained PPM signals are analyzed. The third part of the experimental results, in which the main goal of this thesis is achieved, includes an investigation of the performance of the Coherent Optical Receiver Experiment (CORE) at JPL. Bit Error Rate (BER) results are presented for single and multichannel optical receivers where quasi shot noise-limited performance is achieved under simulated turbulence conditions using noncoherent postdetection processing techniques. Theoretical BER expressions are

  3. Removal of pedestals and directional ambiguity of optical anemometer signals.

    Science.gov (United States)

    Durst, F; Zaré, M

    1974-11-01

    Laser Doppler anemometry permits, in principle, the measurement of both magnitude and direction of components of a particle's velocity vector. Most exiting anemometers, however, permit measurements only with a directional ambiguity of 180 degrees , resulting in errors in certain flow fields. Available methods of eliminating the directional ambiguity of Laser Doppler anemometers are reviewed, covering frequency shifting of the incident and scattered light beams, the use of beams with different polarization properties, and employment of multicolor laser beams. The advantages and disadvantages of existing methods are summarized, and suggestions for alterations are made. Different techniques used to remove the pedestal of laser Doppler anemometer signals are also reviewed. Optical techniques should be employed in any advanced optical anemometer system to avoid dynamic range limitations by electronic bandpass filters. Suggestions are made for advanced optical anemometers employing multielement avalanche photodiodes that can be used for simultaneous measurements of two velocity components. These anemometers incorporate devices to sense the direction of the velocity components and to eliminate optically the pedestal of laser Doppler signals.

  4. Applications of all optical signal processing for advanced optical modulation formats

    Science.gov (United States)

    Nuccio, Scott R.

    Increased data traffic demands, along with a continual push to minimize cost per bit, have recently motivated a paradigm shift away from traditional on-off keying (OOK) fiber transmission links towards systems utilizing more advanced modulation formats. In particular, modulation formats that utilize the phase of the optical signal, including differential phase shift keying (DPSK) and differential quadrature phase shift keying (DQPSK) along with polarization multiplexing (Pol-MUX), have recently emerged as the most popular means for transmitting information over long-haul and ultra-long haul fiber transmission systems. DPSK is motivated by an increase in receiver sensitivity compared to traditional OOK. DQPSK is motivated by a doubling of the spectral efficiency, along with increased tolerance to dispersion and nonlinear distortions. Coherent communications has also emerged as a primary means of transmitting and receiving optical data due to its support of formats that utilize both phase and amplitude to further increase the spectral efficiency (bits/sec/Hz) of the optical channel, including quadrature amplitude modulation (QAM). Polarization multiplexing of channels is a straight forward method to allow two channels to share the same wavelength by propagating on orthogonal polarization axis and is easily supported in coherent systems where the polarization tracking can be performed in the digital domain. Furthermore, the forthcoming IEEE 100 Gbit/s Ethernet Standard, 802.3ba, provides greater bandwidth, higher data rates, and supports a mixture of modulation formats. In particular, Pol-MUX (D)QPSK has grown in interest as the high spectral efficiency allows for 100 Gbit/s transmission while still occupying the current 50 GHz/channel allocation of current 10 Gbit/s OOK fiber systems. In this manner, 100 Gbit/s transfer speeds using current fiber links, amplifiers, and filters may be possible. In addition to advanced modulation formats, it is expected that optical

  5. Impact of unpredictability on chaos synchronization of vertical-cavity surface-emitting lasers with variable-polarization optical feedback.

    Science.gov (United States)

    Xiang, Shuiying; Pan, Wei; Yan, Lianshan; Luo, Bin; Zou, Xihua; Jiang, Ning; Yang, Lei

    2011-09-01

    The effects of unpredictability degree on the chaos synchronization properties of vertical-cavity surface-emitting lasers with variable-polarization optical feedback are investigated numerically. For variable-polarization optical injection, only low-unpredictability chaos can be well synchronized, while high-unpredictability chaos cannot be synchronized even with large injection strength. On the other hand, for the polarization-preserved optical injection, the synchronization quality is hardly affected by the unpredictability degree, and high-quality synchronization can be achieved for both low- and high-unpredictability chaos due to injection locking.

  6. Soft demodulation to the optical pulse position modulated signals

    Science.gov (United States)

    Zhou, Tian-hua; Chen, Wei-biao

    2009-07-01

    The optical Pulse Position Modulation (PPM) is applied widely in Free Space Optical communication (FSO) with the low average power and the high peak power. The transmitted PPM information depends on the location of the coming optical pulse signals in fixed period. Both receiver and transmitter should been kept in time slot synchronization and frame synchronization in demodulation. Because the channel is very complex, the received optical pulse width will be stretched randomly. We design and realize one digital PPM modulation receiver with high sensitivity using the technology of PMT, A/D converter, and DSP. It is suitable to the total digital optical receiver with random time slots and random pulse width. The paper will mainly discuss the realization of the soft demodulation behind A/D converter. The key of PPM digital soft modulation is the establishment of the synchronization that involves the segment synchronization, the fame synchronization and the bit synchronization. The synchronization can be obtained by seeking for the frame head in data frames. Based on the estimation of received waveform characteristics, we adopt a matched filter without the best factors firstly. Thereafter, their errors will be self-adapted while finding the synchronization head. Considering the real-time need, we choose the reduced mode of maximum likelihood function judgment finally. In the experiments, results with high sensitivity and low bit error rate have been achieved.

  7. All-optical signal processing at 10 GHz using a photonic crystal molecule

    Energy Technology Data Exchange (ETDEWEB)

    Combrié, Sylvain; Lehoucq, Gaëlle; Junay, Alexandra; De Rossi, Alfredo, E-mail: alfredo.derossi@thalesgroup.com [Thales Research and Technology, 1 Avenue A. Fresnel, 91767 Palaiseau (France); Malaguti, Stefania; Bellanca, Gaetano; Trillo, Stefano [Department of Engineering, Università di Ferrara, v. Saragat 1, 44122 Ferrara (Italy); Ménager, Loic [Thales Systèmes Aeroportés, 2 Av. Gay Lussac, 78851 Elancourt (France); Peter Reithmaier, Johann [Institute of Nanostructure Technologies and Analytics, CINSaT, University of Kassel, Heinrich-Plett-Str. 40, 34132 Kassel (Germany)

    2013-11-04

    We report on 10 GHz operation of an all-optical gate based on an Indium Phosphide Photonic Crystal Molecule. Wavelength conversion and all-optical mixing of microwave signals are demonstrated using the 2 mW output of a mode locked diode laser. The spectral separation of the optical pump and signal is crucial in suppressing optical cross-talk.

  8. Quantum-enhanced metrology with the single-mode coherent states of an optical cavity inside a quantum feedback loop

    Science.gov (United States)

    Clark, Lewis A.; Stokes, Adam; Beige, Almut

    2016-08-01

    In this paper, we use the nonlinear generator of dynamics of the individual quantum trajectories of an optical cavity inside an instantaneous quantum feedback loop to measure the phase shift between two pathways of light with a precision above the standard quantum limit. The feedback laser provides a reference frame and constantly increases the dependence of the state of the resonator on the unknown phase. Since our quantum metrology scheme can be implemented with current technology and does not require highly efficient single photon detectors, it should be of practical interest until highly entangled many-photon states become more readily available.

  9. Cellular origin of intrinsic optical signals in the rabbit retina.

    Science.gov (United States)

    Naderian, A; Bussières, L; Thomas, S; Lesage, F; Casanova, C

    2017-08-01

    Optical imaging of retinal intrinsic signals is a relatively new method that provides spatiotemporal patterns of retinal activity through activity-dependent changes in light reflectance of the retina. The exact physiological mechanisms at the origin of retinal intrinsic signals are poorly understood and there are significant inter-species differences in their characteristics and cellular origins. In this study, we re-examined this issue through pharmacological dissection of retinal intrinsic signals in the rabbit with simultaneous ERG recordings. Retinal intrinsic signals faithfully reflected retinal activity as their amplitude was strongly associated with stimulation intensity (r(2)=0.85). Further, a strong linear relation was found using linear regression (r(2)=0.98) between retinal intrinsic signal amplitude and the ERG b wave, which suggests common cellular origins. Intravitreal injections of pharmacological agents were performed to isolate the activity of the retina's major cell types. Retinal intrinsic signals were abolished when the photoreceptors' activity was isolated with aspartate, indicative that they are not at the origin of this signal. A small but significant decrease in intrinsic response (20%) was observed when ganglion and amacrine cells' activity was inhibited by TTX injections. The remaining intrinsic responses were abolished in a dose-dependent manner through the inhibition of ON-bipolar cells by APB. Our results indicate that, in rabbits, retinal intrinsic signals reflect stimulation intensity and originate from the inner retina with a major contribution of bipolar cells and a minor one from ganglion or amacrine cells. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. Detection, Evaluation, and Optimization of Optical Signals Generated by Fiber Optic Bragg Gratings Under Dynamic Excitations

    Science.gov (United States)

    Adamovsky, Grigory; Lekki, John; Lock, James A.

    2002-01-01

    The dynamic response of a fiber optic Bragg grating to mechanical vibrations is examined both theoretically and experimentally. The theoretical expressions describing the consequences of changes in the grating's reflection spectrum are derived for partially coherent beams in an interferometer. The analysis is given in terms of the dominant wavelength, optical bandwidth, and optical path difference of the interfering signals. Changes in the reflection spectrum caused by a periodic stretching and compression of the grating were experimentally measured using an unbalanced Michelson interferometer, a Michelson interferometer with a non-zero optical path difference. The interferometer's sensitivity to changes in dominant wavelength of the interfering beams was measured as a function of interferometer unbalance and was compared to theoretical predictions. The theoretical analysis enables the user to determine the optimum performance for an unbalanced interferometer.

  11. A feedback control system for real-time formant estimation. I--Static and dynamic analysis for sinusoidal input signals.

    Science.gov (United States)

    Zierhofer, C M; Hochmair, E S

    1993-09-01

    This paper presents a novel analog scheme suitable for the real-time estimation of formant frequencies. Formant tracking is based on a feedback technique which uses both the amplitude and phase characteristics of two stagger-tuned bandpass filters to give an improved dynamic behavior. The implementation of the system requires a small number of components, and is practical for low-power applications. An analysis of the static and dynamic behavior is given for sinusoidal input signals. The transient response is independent of the amplitude level of the input signal. The system is designed for second formant detection in a cochlear prosthesis system.

  12. Non-fragile state feedback H-infinity control for discrete-time systems with quantized signals

    Institute of Scientific and Technical Information of China (English)

    Weiwei CHE; Guanghong YANG

    2009-01-01

    This paper presents a study on the problem of non-fragile state feedback H-infinity controller design for linear discrete-time systems with quantized signals.The quantizers considered here are dynamic and time-varying.With the consideration of controller gain variations and quantized signals at the same time,a new non-fragile H-infinity control strategy is proposed with updating quantizer's parameters,such that the quantized closed-loop system is asymptotically stable and with a prescribed H-infinity performance bound.An example is presented to illustrate the effectiveness of the proposed control strategy.

  13. Polarization and wavelength insensitive optical feedback control systems for stabilizing CO2 lasers

    Science.gov (United States)

    Jebali, M. A.

    2016-03-01

    Power scaling of multi-kilowatt fiber lasers has been driving the development of glass and fiber processing technology. Designed for processing of large diameter fibers, this technology is used for the fabrication of fiber-based components such as end-pump and side pump combiners, large diameter endcaps, ball lenses for collimators and focusers… The use of 10.6um CO2 lasers as a heating element provides incomparable flexibility, process control and repeatability when compared to conventional heating methods. This low maintenance technology provides an accurate, adjustable and uniform heating area by absorption of fused silica of the 10.6m laser radiation. However, commercially available CO2 lasers can experience power, polarization and mode instability, which becomes important at 20W levels and higher of output power. This paper presents a polarization and wavelength insensitive optical feedback control system for stabilizing commercially available CO2 lasers. Less than 1% power fluctuation was achieved at different laser power levels, ranging from as 5 to 40W.

  14. Low cost heads-up virtual reality (HUVR) with optical tracking and haptic feedback

    Science.gov (United States)

    Margolis, Todd; DeFanti, Thomas A.; Dawe, Greg; Prudhomme, Andrew; Schulze, Jurgen P.; Cutchin, Steve

    2011-03-01

    Researchers at the University of California, San Diego, have created a new, relatively low-cost augmented reality system that enables users to touch the virtual environment they are immersed in. The Heads-Up Virtual Reality device (HUVR) couples a consumer 3D HD flat screen TV with a half-silvered mirror to project any graphic image onto the user's hands and into the space surrounding them. With his or her head position optically tracked to generate the correct perspective view, the user maneuvers a force-feedback (haptic) device to interact with the 3D image, literally 'touching' the object's angles and contours as if it was a tangible physical object. HUVR can be used for training and education in structural and mechanical engineering, archaeology and medicine as well as other tasks that require hand-eye coordination. One of the most unique characteristics of HUVR is that a user can place their hands inside of the virtual environment without occluding the 3D image. Built using open-source software and consumer level hardware, HUVR offers users a tactile experience in an immersive environment that is functional, affordable and scalable.

  15. Low cost heads-up virtual reality (HUVR) with optical tracking and haptic feedback

    KAUST Repository

    Margolis, Todd

    2011-01-23

    Researchers at the University of California, San Diego, have created a new, relatively low-cost augmented reality system that enables users to touch the virtual environment they are immersed in. The Heads-Up Virtual Reality device (HUVR) couples a consumer 3D HD flat screen TV with a half-silvered mirror to project any graphic image onto the user\\'s hands and into the space surrounding them. With his or her head position optically tracked to generate the correct perspective view, the user maneuvers a force-feedback (haptic) device to interact with the 3D image, literally \\'touching\\' the object\\'s angles and contours as if it was a tangible physical object. HUVR can be used for training and education in structural and mechanical engineering, archaeology and medicine as well as other tasks that require hand-eye coordination. One of the most unique characteristics of HUVR is that a user can place their hands inside of the virtual environment without occluding the 3D image. Built using open-source software and consumer level hardware, HUVR offers users a tactile experience in an immersive environment that is functional, affordable and scalable.

  16. Label-free imaging through nonlinear optical signals

    Directory of Open Access Journals (Sweden)

    Ling Tong

    2011-06-01

    Full Text Available Strong intrinsic nonlinear optical (NLO signals not only make nanostructures promising agents for bio-imaging, but also advance NLO microscopy for the study of interactions between nanomaterials and live cells. Single beam modalities such as multiphoton luminescence, second harmonic generation, and third harmonic generation provide a simple way to probe many types of nanostructures. As for more advanced modalities, photothermal heterodyne imaging provides improved detection sensitivity for smaller objects, and transient absorption microscopy provides structural information to distinguish metal from semiconducting carbon nanotubes, and eumelanin from pheomelanin. The four-wave mixing signal achieves chemical selectivity in the presence of either vibrational or electronic resonance, as used in coherent Raman scattering imaging of molecules and in electronically resonance enhanced four-wave mixing imaging of nanostructures.

  17. Symbol rate identification for auxiliary amplitude modulation optical signal

    Science.gov (United States)

    Wei, Junyu; Dong, Zhi; Huang, Zhiping; Zhang, Yimeng

    2016-09-01

    In this paper, we creatively propose and demonstrate a method for symbol rate identification (SRI) of auxiliary amplitude modulation (AAM) optical signal based on asynchronous delay-tap sampling (ADTS) and average magnitude difference function (AMDF). The method can accurately estimate symbol rate and has large transmission impairments tolerance. Furthermore, it can be realized in the digital signal processor (DSP) with low logical resources because of multiplication-free. In order to improve the accuracy of SRI, the peak to valley ratio (PTVR) of AMDF is introduced into our method for blind chromatic dispersion (CD) compensation. The results of the numerical simulations show that the overall maximum SRI error is smaller 0.079% for return-to-zero (RZ) on-off keying (OOK), RZ differential phase-shift keying (DPSK), RZ differential quadrature phase-shift keying (DQPSK) and RZ 16-ary quadrature amplitude modulation (QAM) with 50% duty cycles.

  18. Signal processing for all fiber optical current transducer

    Institute of Scientific and Technical Information of China (English)

    裴焕斗; 祖静; 陈鸿

    2008-01-01

    The work principle of all fiber optical current transducer (AFOCT) was introduced. By analyzing the characteristic of photo-detector’s output, a measurement and signal processing scheme based on sine wave modulation and demodulation was put forward for eliminating the influence of light intensity change and modulation degree change. A digital signal processing system and a calibration scheme were also advanced. The experimental data show that the mean ratio error is 0.016 74% for direct current and 0.035% for alternating current, and the correlation coefficient of linearity is up to 0.999 982 4, meeting the precision requirement of 0.2 grade. Stability experiments and temperature drift experiments show the AFOCT has a better stable capability.

  19. Nonlinear optical signals and spectroscopy with quantum light

    CERN Document Server

    Dorfman, Konstantin E; Mukamel, Shaul

    2016-01-01

    Conventional nonlinear spectroscopy uses classical light to detect matter properties through the variation of its response with frequencies or time delays. Quantum light opens up new avenues for spectroscopy by utilizing parameters of the quantum state of light as novel control knobs and through the variation of photon statistics by coupling to matter. We present an intuitive diagrammatic approach for calculating ultrafast spectroscopy signals induced by quantum light, focusing on applications involving entangled photons with nonclassical bandwidth properties - known as "time-energy entanglement". Nonlinear optical signals induced by quantized light fields are expressed using time ordered multipoint correlation functions of superoperators. These are different from Glauber's g- functions for photon counting which use normally ordered products of ordinary operators. Entangled photon pairs are not subjected to the classical Fourier limitations on the joint temporal and spectral resolution. After a brief survey o...

  20. Optical modulation techniques for analog signal processing and CMOS compatible electro-optic modulation

    Science.gov (United States)

    Gill, Douglas M.; Rasras, Mahmoud; Tu, Kun-Yii; Chen, Young-Kai; White, Alice E.; Patel, Sanjay S.; Carothers, Daniel; Pomerene, Andrew; Kamocsai, Robert; Beattie, James; Kopa, Anthony; Apsel, Alyssa; Beals, Mark; Mitchel, Jurgen; Liu, Jifeng; Kimerling, Lionel C.

    2008-02-01

    Integrating electronic and photonic functions onto a single silicon-based chip using techniques compatible with mass-production CMOS electronics will enable new design paradigms for existing system architectures and open new opportunities for electro-optic applications with the potential to dramatically change the management, cost, footprint, weight, and power consumption of today's communication systems. While broadband analog system applications represent a smaller volume market than that for digital data transmission, there are significant deployments of analog electro-optic systems for commercial and military applications. Broadband linear modulation is a critical building block in optical analog signal processing and also could have significant applications in digital communication systems. Recently, broadband electro-optic modulators on a silicon platform have been demonstrated based on the plasma dispersion effect. The use of the plasma dispersion effect within a CMOS compatible waveguide creates new challenges and opportunities for analog signal processing since the index and propagation loss change within the waveguide during modulation. We will review the current status of silicon-based electrooptic modulators and also linearization techniques for optical modulation.

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

    DEFF Research Database (Denmark)

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

    2016-01-01

    four-wave mixing (FWM), separated by a dispersive medium, which enables time-to-frequency and frequency-to-time conversions simultaneously, thus performing an exchange between the temporal and spectral profiles of the input signal. Using the proposed complete OFT, several advanced all-optical signal......We review recent progress in the use of time lens based optical Fourier transformation for advanced all-optical signal processing. A novel time lens based complete optical Fourier transformation (OFT) technique is introduced. This complete OFT is based on two quadratic phase-modulation stages using...... processing schemes for spectrally-efficient systems and networks have been achieved, including all-optical generation, detection and format conversion of spectrally-efficient signals. The spectrally-efficient signals in this paper mainly refer to efficiently multiplexed signals with a high symbol rate per Hz...

  2. Simultaneous Computation of Two Independent Tasks Using Reservoir Computing Based on a Single Photonic Nonlinear Node With Optical Feedback.

    Science.gov (United States)

    Nguimdo, Romain Modeste; Verschaffelt, Guy; Danckaert, Jan; Van der Sande, Guy

    2015-12-01

    In this brief, we numerically demonstrate a photonic delay-based reservoir computing system, which processes, in parallel, two independent computational tasks even when the two tasks have unrelated input streams. Our approach is based on a single-longitudinal mode semiconductor ring laser (SRL) with optical feedback. The SRL emits in two directional optical modes. Each directional mode processes one individual task to mitigate possible crosstalk. We illustrate the feasibility of our scheme by analyzing the performance on two benchmark tasks: 1) chaotic time series prediction and 2) nonlinear channel equalization. We identify some feedback configurations for which the results for simultaneous prediction/classification indicate a good performance, but with slight degradation (as compared with the performance obtained for single task processing) due to nonlinear and linear interactions between the two directional modes of the laser. In these configurations, the system performs well on both tasks for a broad range of the parameters.

  3. Stabilization of a fiber-optic two-arm interferometer for ultra-short pulse signal processing applications.

    Science.gov (United States)

    Park, Yongwoo; Ahn, Tae-Jung; Azaña, José

    2008-01-20

    We experimentally demonstrate a stable ultrafast first-order temporal differentiator using a fiber-optic Michelson interferometer incorporating a simple feedback stabilization control, which is based on dithering a single wavelength cw reference. Feedback control signals are acquired by a phase-lock-loop and used for automatically adjusting and maintaining the resonance wavelength of the differentiator at the pulse center wavelength without dithering or disturbing the interferometer arms. Picosecond odd-symmetry Hermite-Gaussian waveforms using the implemented first-order differentiator have been stably generated. The demonstrated stabilization system should prove useful for a wide range of ultrafast pulse processing and analysis applications based on the use of two-arm interferometers.

  4. Effectiveness of a feedback signal in a computer mouse on upper extremity musculoskeletal symptoms: a randomised controlled trial with an 8-month follow-up

    NARCIS (Netherlands)

    E.M. Meijer; J.K. Sluiter; M.H.W. Frings-Dresen

    2009-01-01

    OBJECTIVES: To study the effectiveness of using a computer mouse with a feedback signal for upper extremity musculoskeletal symptoms in office workers. METHODS: A randomised controlled trial with 8 months of follow-up was carried out. The intervention consisted of a computer mouse with a feedback si

  5. Generation of polarization-resolved wideband unpredictability-enhanced chaotic signals based on vertical-cavity surface-emitting lasers subject to chaotic optical injection.

    Science.gov (United States)

    Chen, Jian-Jun; Wu, Zheng-Mao; Tang, Xi; Deng, Tao; Fan, Li; Zhong, Zhu-Qiang; Xia, Guang-Qiong

    2015-03-23

    A system framework is proposed and analyzed for generating polarization-resolved wideband unpredictability-enhanced chaotic signals based on a slave vertical-cavity surface-emitting laser (S-VCSEL) driven by an injected optical chaos signal from a master VCSEL (M-VCSEL) under optical feedback. After calculating the time series outputs from the M-VCSEL under optical feedback and the S-VCSEL under chaotic optical injection by using the spin-flip model (SFM), the unpredictability degree (UD) is evaluated by permutation entropy (PE), and the bandwidth of the polarization-resolved outputs from the M-VCSEL and S-VCSEL are numerically investigated. The results show that, under suitable parameters, both the bandwidth and UD of two polarization components (PCs) outputs from the S-VCSEL can be enhanced significantly compared with that of the driving chaotic signals output from the M-VCSEL. By simulating the influences of the feedback and injection parameters on the bandwidth and UD of the polarization-resolved outputs from S-VCSEL, related operating parameters can be optimized.

  6. General Purpose Digital Signal Processing VME-Module for 1-Turn Delay Feedback Systems of the CERN Accelerator Chain

    CERN Document Server

    Rossi, V

    2010-01-01

    In the framework of the LHC project and the modifications of the SPS as its injector, the concept has been developed of a global digital signal processing unit (DSPU) that implements in numerical form the architecture of low-level RF systems. Since 2002 a Digital Notch Filter with programmable delay for the SPS Transverse Damper has been fully operational with fixed target and LHC-type beams circulating in the SPS. The approach, using an FPGA as core for the low-level system, is very flexible and allows the upgrade of the signal processing by modification of the original firmware. The development for the LHC 1-Turn delay Feedback has benefited from the same methodology and similar technology. The achieved performances of the LHC 1-Turn delay Feedback are compared with project requirements. The project flow for the recent LHC 1-T Feedback allows synergy with several other applications. The CERN PS Transverse Damper DSPU, with automatic delay compensation adapting the loop delay to the time of flight of the par...

  7. A positive feedback loop between Gli1 and tyrosine kinase Hck amplifies shh signaling activities in medulloblastoma.

    Science.gov (United States)

    Shi, X; Zhan, X; Wu, J

    2015-11-30

    Sonic hedgehog (Shh) signaling is critical during normal development, and the abnormal activation of the Shh pathway is involved in many human cancers. As a target gene of the Shh pathway and as a transcription activator downstream of Shh signaling, Gli1 autoregulates and increases Shh signaling output. Gli1 is one of the key oncogenic factors in Shh-induced tumors such as medulloblastoma. Gli1 is posttranslationally modified, but the nature of the active form of Gli1 was unclear. Here we identified a Src family kinase Hck as a novel activator of Gli1. In Shh-responsive NIH3T3 cells, Hck interacts with Gli1 and phosphorylates multiple tyrosine residues in Gli1. Gli1-mediated target gene activation was significantly enhanced by Hck with both kinase activity-dependent and -independent mechanisms. We provide evidence showing that Hck disrupts the interaction between Gli1 and its inhibitor Sufu. In both NIH3T3 cells and cerebellum granule neuron precursors, the Hck gene is also a direct target of Gli1. Therefore, Gli1 and Hck form a positive feedback loop that amplifies Shh signaling transcription outcomes. In Shh-induced medulloblastoma, Hck is highly expressed and Gli1 is tyrosine phosphorylated, which may enhance the tumorigenic effects of the Gli1 oncogene. RNAi-mediated inhibition of Hck expression significantly repressed medulloblastoma cell growth. In summary, a novel positive feedback loop contributes to maximal Gli1 oncogenic activities in Shh-induced tumors such as medulloblastoma.

  8. Multimode optical feedback dynamics of InAs/GaAs quantum-dot lasers emitting on different lasing states

    Science.gov (United States)

    Huang, H.; Arsenijević, D.; Schires, K.; Sadeev, T.; Bimberg, D.; Grillot, F.

    2016-12-01

    Quantum dot lasers are envisioned to be the next generation of optical transmitters used for short-reach communication links, owing to their low threshold current and high temperature operation. However, in a context of steady increase in both speed and reach, quantum dot lasers emitting on their upper energy levels have been recently of greater interest as they are touted for their faster modulation dynamics. This work aims at further evaluating the potential impact of such lasers in communication links by characterizing their long-delay optical feedback responses as well as the role of the lasing states on the multimode dynamics of InAs/GaAs quantum-dot Fabry-Perot devices sharing the same design. Results unveil that the excited-state laser shows a much larger sensitivity to optical feedback, with a more complex route to chaos, and a first destabilization point occurring at lower feedback strengths than for a comparable ground-state laser, which remains almost unaffected.

  9. Chaos synchronization in vertical-cavity surface-emitting laser based on rotated polarization-preserved optical feedback

    Science.gov (United States)

    Nazhan, Salam; Ghassemlooy, Zabih; Busawon, Krishna

    2016-01-01

    In this paper, the influence of the rotating polarization-preserved optical feedback on the chaos synchronization of a vertical-cavity surface-emitting laser (VCSEL) is investigated experimentally. Two VCSELs' polarization modes (XP) and (YP) are gradually rotated and re-injected back into the VCSEL. The anti-phase dynamics synchronization of the two polarization modes is evaluated using the cross-correlation function. For a fixed optical feedback, a clear relationship is found between the cross-correlation coefficient and the polarization angle θp. It is shown that high-quality anti-phase polarization-resolved chaos synchronization is achieved at higher values of θp. The maximum value of the cross-correlation coefficient achieved is -0.99 with a zero time delay over a wide range of θp beyond 65° with a poor synchronization dynamic at θp less than 65°. Furthermore, it is observed that the antiphase irregular oscillation of the XP and YP modes changes with θp. VCSEL under the rotating polarization optical feedback can be a good candidate as a chaotic synchronization source for a secure communication system.

  10. Chaos synchronization in vertical-cavity surface-emitting laser based on rotated polarization-preserved optical feedback

    Energy Technology Data Exchange (ETDEWEB)

    Nazhan, Salam; Ghassemlooy, Zabih; Busawon, Krishna [Optical Communications Research Group, NCRLab, Faculty of Engineering and Environment, Northumbria University, Newcastle upon Tyne (United Kingdom)

    2016-01-15

    In this paper, the influence of the rotating polarization-preserved optical feedback on the chaos synchronization of a vertical-cavity surface-emitting laser (VCSEL) is investigated experimentally. Two VCSELs' polarization modes (XP) and (YP) are gradually rotated and re-injected back into the VCSEL. The anti-phase dynamics synchronization of the two polarization modes is evaluated using the cross-correlation function. For a fixed optical feedback, a clear relationship is found between the cross-correlation coefficient and the polarization angle θ{sub p}. It is shown that high-quality anti-phase polarization-resolved chaos synchronization is achieved at higher values of θ{sub p}. The maximum value of the cross-correlation coefficient achieved is −0.99 with a zero time delay over a wide range of θ{sub p} beyond 65° with a poor synchronization dynamic at θ{sub p} less than 65°. Furthermore, it is observed that the antiphase irregular oscillation of the XP and YP modes changes with θ{sub p}. VCSEL under the rotating polarization optical feedback can be a good candidate as a chaotic synchronization source for a secure communication system.

  11. Time-domain model of quantum-dot semiconductor optical amplifiers for wideband optical signals.

    Science.gov (United States)

    Puris, D; Schmidt-Langhorst, C; Lüdge, K; Majer, N; Schöll, E; Petermann, K

    2012-11-19

    We present a novel theoretical time-domain model for a quantum dot semiconductor optical amplifier, that allows to simulate subpicosecond pulse propagation including power-based and phase-based effects. Static results including amplified spontaneous emission spectra, continuous wave amplification, and four-wave mixing experiments in addition to dynamic pump-probe simulations are presented for different injection currents. The model uses digital filters to describe the frequency dependent gain and microscopically calculated carrier-carrier scattering rates for the interband carrier dynamics. It can be used to calculate the propagation of multiple signals with different wavelengths or one wideband signal with high bitrate.

  12. Stochastic signalling rewires the interaction map of a multiple feedback network during yeast evolution

    Science.gov (United States)

    Hsu, Chieh; Scherrer, Simone; Buetti-Dinh, Antoine; Ratna, Prasuna; Pizzolato, Julia; Jaquet, Vincent; Becskei, Attila

    2012-01-01

    During evolution, genetic networks are rewired through strengthening or weakening their interactions to develop new regulatory schemes. In the galactose network, the GAL1/GAL3 paralogues and the GAL2 gene enhance their own expression mediated by the Gal4p transcriptional activator. The wiring strength in these feedback loops is set by the number of Gal4p binding sites. Here we show using synthetic circuits that multiplying the binding sites increases the expression of a gene under the direct control of an activator, but this enhancement is not fed back in the circuit. The feedback loops are rather activated by genes that have frequent stochastic bursts and fast RNA decay rates. In this way, rapid adaptation to galactose can be triggered even by weakly expressed genes. Our results indicate that nonlinear stochastic transcriptional responses enable feedback loops to function autonomously, or contrary to what is dictated by the strength of interactions enclosing the circuit. PMID:22353713

  13. Use of Fiber Optic Interconnects for Signal Integrity

    Science.gov (United States)

    Phal, Yamuna D.; Phal, Deovrat D.

    2016-05-01

    Signal integrity (SI) is always a concern when it comes to high-speed data transmission. Even in space, there is a need for high-speed data transmission such as in the communication systems, monitoring various sub- systems and for other on-board experiments and applications.From Electromagneticperspective, using fiber-optic interconnect is highly recommended to avoid interference issues. This field has been explored for quite some time now, but mostly limited to applications that are on earth. Using these interconnects for harsh and extreme environments i.e. in space, requires reliability and ruggedness of interconnects and the system.This study suggests methods for optical fiber based communication systems for internal unit communication, communication within various instruments, as well as inter-board communication. A conclusion in terms of what areas need to be explored for enabling high-speed data transmission for space applications would be discussed in details. This study also explores and compares the existing technologies in the fiber-optic interconnects for space applications.

  14. Digital signal processing techniques for coherent optical communication

    Science.gov (United States)

    Goldfarb, Gilad

    Coherent detection with subsequent digital signal processing (DSP) is developed, analyzed theoretically and numerically and experimentally demonstrated in various fiber-optic transmission scenarios. The use of DSP in conjunction with coherent detection unleashes the benefits of coherent detection which rely on the preservaton of full information of the incoming field. These benefits include high receiver sensitivity, the ability to achieve high spectral-efficiency and the use of advanced modulation formats. With the immense advancements in DSP speeds, many of the problems hindering the use of coherent detection in optical transmission systems have been eliminated. Most notably, DSP alleviates the need for hardware phase-locking and polarization tracking, which can now be achieved in the digital domain. The complexity previously associated with coherent detection is hence significantly diminished and coherent detection is once gain considered a feasible detection alternative. In this thesis, several aspects of coherent detection (with or without subsequent DSP) are addressed. Coherent detection is presented as a means to extend the dispersion limit of a duobinary signal using an analog decision-directed phase-lock loop. Analytical bit-error ratio estimation for quadrature phase-shift keying signals is derived. To validate the promise for high spectral efficiency, the orthogonal-wavelength-division multiplexing scheme is suggested. In this scheme the WDM channels are spaced at the symbol rate, thus achieving the spectral efficiency limit. Theory, simulation and experimental results demonstrate the feasibility of this approach. Infinite impulse response filtering is shown to be an efficient alternative to finite impulse response filtering for chromatic dispersion compensation. Theory, design considerations, simulation and experimental results relating to this topic are presented. Interaction between fiber dispersion and nonlinearity remains the last major challenge

  15. Silicon nanowires for ultra-fast and ultrabroadband optical signal processing

    DEFF Research Database (Denmark)

    Ji, Hua; Hu, Hao; Pu, Minhao;

    2015-01-01

    In this paper, we present recent research on silicon nanowires for ultra-fast and ultra-broadband optical signal processing at DTU Fotonik. The advantages and limitations of using silicon nanowires for optical signal processing are revealed through experimental demonstrations of various optical...

  16. Cell swelling and ion redistribution assessed with intrinsic optical signals

    Directory of Open Access Journals (Sweden)

    WITTE OTTO W.

    2001-01-01

    Full Text Available Cell volume changes are associated with alterations of intrinsic optical signals (IOS. In submerged brain slices in vitro, afferent stimulation induces an increase in light transmission. As assessed by measurement of the largely membrane impermeant ion tetramethylammonium (TMA in the extracellular space, these IOS correlate with the extent and time course of the change of the extracellular space size. They have a high signal to noise ratio and allow measurements of IOS changes in the order of a few percent. Under conditions of reduced net KCl uptake (low Cl solution a directed spatial buffer mechanism (K syphoning can be demonstrated in the neocortex with widening of the extracellular space in superficial layers associated with a reduced light transmission and an increase of extracellular K concentration. The nature of the IOS under pathophysiological conditions is less clear. Spreading depressions first cause an increase of light transmission, then a decrease. Such a decrease has also been observed following application of NMDA where it was associated with structural damage. Pharmacological analyses suggest that under physiological conditions changes of extracellular space size are mainly caused by astrocytic volume changes while with strong stimuli and under pathophysiological conditions also neuronal swelling occurs. With reflected light usually signals opposite to those observed with transmitted light are seen. Recording of IOS from interface slices gives very complex signals since under these conditions an increase of light transmission has been reported to be superimposed by a decrease of the signal due to mechanical lensing effects of the slice surface. Depending on the method of measurement and the exact conditions, several mechanisms may contribute to IOS. Under well defined conditions IOS are a useful supplementary tool to monitor changes of extracellular volume both in space and time.

  17. Linearized Optically Phase-Modulated Fiber Optic Links for Microwave Signal Transport

    Science.gov (United States)

    2009-03-03

    a number of external modulation techniques. For particularly long links, a single or small number of Erbium-Doped Fiber Amplifiers ( EDFA ) could...amplifier (Erbium-Doped Fiber Amplifier, or EDFA ) is present, its noise contribution is caused by beating between the signal and the...the absence of an EDFA , received optical powers that generate photocurrents below approximately 1 mA cause the system noise to be dominated by the

  18. Inhibition of Wnt signaling by Wise (Sostdc1) and negative feedback from Shh controls tooth number and patterning.

    Science.gov (United States)

    Ahn, Youngwook; Sanderson, Brian W; Klein, Ophir D; Krumlauf, Robb

    2010-10-01

    Mice carrying mutations in Wise (Sostdc1) display defects in many aspects of tooth development, including tooth number, size and cusp pattern. To understand the basis of these defects, we have investigated the pathways modulated by Wise in tooth development. We present evidence that, in tooth development, Wise suppresses survival of the diastema or incisor vestigial buds by serving as an inhibitor of Lrp5- and Lrp6-dependent Wnt signaling. Reducing the dosage of the Wnt co-receptor genes Lrp5 and Lrp6 rescues the Wise-null tooth phenotypes. Inactivation of Wise leads to elevated Wnt signaling and, as a consequence, vestigial tooth buds in the normally toothless diastema region display increased proliferation and continuous development to form supernumerary teeth. Conversely, gain-of-function studies show that ectopic Wise reduces Wnt signaling and tooth number. Our analyses demonstrate that the Fgf and Shh pathways are major downstream targets of Wise-regulated Wnt signaling. Furthermore, our experiments revealed that Shh acts as a negative-feedback regulator of Wnt signaling and thus determines the fate of the vestigial buds and later tooth patterning. These data provide insight into the mechanisms that control Wnt signaling in tooth development and into how crosstalk among signaling pathways controls tooth number and morphogenesis.

  19. Development and analysis of new type microresonator with electro-optic feedback

    Science.gov (United States)

    Janusas, Giedrius; Palevicius, Arvydas; Cekas, Elingas; Brunius, Alfredas; Bauce, Jokubas

    2016-04-01

    Micro-resonators are fundamental components integrated in a hosts of MEMS applications: safety and stability systems, biometric sensors, switches, mechanical filters, micro-mirror devices, material characterization, gyroscopes, etc. A constituent part of the micro-resonator is a diffractive optical element (DOE). Different methods and materials are used to produce diffraction gratings for DOEs. Two-dimensional or three-dimensional periodic structures of micrometer-scale period are widely used in microsystems or their components. They can be used as elements for micro-scale synthesis, processing, and analysis of chemical and biological samples. On the other hand micro-resonator was designed using composite piezoelectric material. In case when microscopes, vibrometers or other direct measurement methods are destructive and hardly can be employed for in-situ analysis, indirect measurement of electrical signal generated by composite piezoelectric layer allows to measure natural frequency changes. Also piezoelectric layer allows to create a novel micro-resonator with controllable parameters, which could assure much higher functionality of micro-electromechanical systems. The novel micro-resonator for pollution detection is proposed. Mathematical model of the micro-resonator and its dynamical, electrical and optical characteristics are presented.

  20. Comparative analysis of frequency and noise characteristics of Fabry – Perot and distributed feedback laser diodes with external optical injection locking

    Energy Technology Data Exchange (ETDEWEB)

    Afonenko, A A; Dorogush, E S [Belarusian State University, Minsk (Belarus); Malyshev, S A; Chizh, A L [B.I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, Minsk (Belarus)

    2015-11-30

    Using a system of coupled travelling wave equations, in the small-signal regime we analyse frequency and noise characteristics of index- or absorption-coupled distributed feedback laser diodes, as well as of Fabry – Perot (FP) laser diodes. It is shown that the weakest dependence of the direct modulation efficiency on the locking frequency in the regime of strong external optical injection locking is exhibited by a FP laser diode formed by highly reflective and antireflective coatings on the end faces of a laser structure. A reduction in the dependence of output characteristics of the laser diode on the locking frequency can be attained by decreasing the reflection coefficient of the antireflective FP mirror. (control of laser radiation parameters)

  1. FGF signaling enhances a sonic hedgehog negative feedback loop at the initiation of spinal cord ventral patterning.

    Science.gov (United States)

    Morales, Aixa V; Espeso-Gil, Sergio; Ocaña, Inmaculada; Nieto-Lopez, Francisco; Calleja, Elena; Bovolenta, Paola; Lewandoski, Mark; Diez Del Corral, Ruth

    2016-09-01

    A prevalent developmental mechanism for the assignment of cell identities is the production of spatiotemporal concentration gradients of extracellular signaling molecules that are interpreted by the responding cells. One of such signaling systems is the Shh gradient that controls neuronal subtype identity in the ventral spinal cord. Using loss and gain of function approaches in chick and mouse embryos, we show here that the fibroblast growth factor (FGF) signaling pathway is required to restrict the domains of ventral gene expression as neuroepithelial cells become exposed to Shh during caudal extension of the embryo. FGF signaling activates the expression of the Shh receptor and negative pathway regulator Patched 2 (Ptch2) and therefore can enhance a negative feedback loop that restrains the activity of the pathway. Thus, we identify one of the mechanisms by which FGF signaling acts as a modulator of the onset of Shh signaling activity in the context of coordination of ventral patterning and caudal axis extension. © 2015 Wiley Periodicals, Inc. Develop Neurobiol 76: 956-971, 2016.

  2. Noise and signal interference in optical fiber transmission systems an optimum design approach

    CERN Document Server

    Bottacchi, Stefano

    2008-01-01

    A comprehensive reference to noise and signal interference in optical fiber communications Noise and Signal Interference in Optical Fiber Transmission Systems is a compendium on specific topics within optical fiber transmission and the optimization process of the system design. It offers comprehensive treatment of noise and intersymbol interference (ISI) components affecting optical fiber communications systems, containing coverage on noise from the light source, the fiber and the receiver. The ISI is modeled with a statistical approach, leading to new useful computational m

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

    DEFF Research Database (Denmark)

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

    2016-01-01

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

  4. Continuous control of ionization wave chaos by spatially derived feedback signals

    CERN Document Server

    Mausbach, T; Piel, A; Atipo, A; Pierre, T; Bonhomme, G; Mausbach, Th.; Klinger, Th.; Pierre, Th.

    1997-01-01

    In the positive column of a neon glow discharge, two different types of ionization waves occur simultaneously. The low-dimensional chaos arising from the nonlinear interaction between the two waves is controlled by a continuous feedback technique. The control strategy is derived from the time-delayed autosynchronization method. Two spatially displaced points of observation are used to obtain the control information, using the propagation characteristics of the chaotic wave.

  5. Stochastic signalling rewires the interaction map of a multiple feedback network during yeast evolution

    OpenAIRE

    2012-01-01

    During evolution, genetic networks are rewired through strengthening or weakening their interactions to develop new regulatory schemes. In the galactose network, the GAL1/GAL3 paralogues and the GAL2 gene enhance their own expression mediated by the Gal4p transcriptional activator. The wiring strength in these feedback loops is set by the number of Gal4p binding sites. Here we show using synthetic circuits that multiplying the binding sites increases the expression of a gene under the direct ...

  6. Investigation of External Optical Feedback Resistance of IC-DFB and GC-DFB Lasers Using a Very Simple Experimental set-up

    Institute of Scientific and Technical Information of China (English)

    孙长征; 熊兵; 罗毅; 中野义昭

    2003-01-01

    We study the external optical feedback resistance of both index-coupled (IC) and gain-coupled distributed feedback (DFB) lasers using a very simple experimental set-up. Though IC-DFB lasers with large coupling coefficients are found to be less sensitive to external reflection, they suffer from mode instability at high injection level. On the other hand, the introduction of gain-coupling mechanism can significantly improve both the immunity to external optical feedback and the single mode yield of the device.

  7. Optical electronics

    CERN Document Server

    Yariv, Amnon

    1991-01-01

    This classic text introduces engineering students to the first principles of major phenomena and devices of optoelectronics and optical communication technology. Yariv's "first principles" approach employs real-life examples and extensive problems. The text includes separate chapters on quantum well and semiconductor lasers, as well as phase conjugation and its applications. Optical fiber amplification, signal and noise considerations in optical fiber systems, laser arrays and distributed feedback lasers all are covered extensively in major sections within chapters.

  8. The serpin PN1 is a feedback regulator of FGF signaling in germ layer and primary axis formation.

    Science.gov (United States)

    Acosta, Helena; Iliev, Dobromir; Grahn, Tan Hooi Min; Gouignard, Nadège; Maccarana, Marco; Griesbach, Julia; Herzmann, Svende; Sagha, Mohsen; Climent, Maria; Pera, Edgar M

    2015-03-15

    Germ layer formation and primary axis development rely on Fibroblast growth factors (FGFs). In Xenopus, the secreted serine protease HtrA1 induces mesoderm and posterior trunk/tail structures by facilitating the spread of FGF signals. Here, we show that the serpin Protease nexin-1 (PN1) is transcriptionally activated by FGF signals, suppresses mesoderm and promotes head development in mRNA-injected embryos. An antisense morpholino oligonucleotide against PN1 has the opposite effect and inhibits ectodermal fate. However, ectoderm and anterior head structures can be restored in PN1-depleted embryos when HtrA1 and FGF receptor activities are diminished, indicating that FGF signals negatively regulate their formation. We show that PN1 binds to and inhibits HtrA1, prevents degradation of the proteoglycan Syndecan 4 and restricts paracrine FGF/Erk signaling. Our data suggest that PN1 is a negative-feedback regulator of FGF signaling and has important roles in ectoderm and head development.

  9. Dysregulation of SOCS-Mediated Negative Feedback of Cytokine Signaling in Carcinogenesis and Its Significance in Cancer Treatment

    Science.gov (United States)

    Jiang, Mengmeng; Zhang, Wen-wen; Liu, Pengpeng; Yu, Wenwen; Liu, Ting; Yu, Jinpu

    2017-01-01

    Suppressor of cytokine signaling (SOCS) proteins are major negative feedback regulators of cytokine signaling mediated by the Janus kinase (JAK)-signal transducer and activator of transcription signaling pathway. In particular, SOCS1 and SOCS3 are strong inhibitors of JAKs and can play pivotal roles in the development and progression of cancers. The abnormal expression of SOCS1 and SOCS3 in cancer cells is associated with the dysregulation of cell growth, migration, and death induced by multiple cytokines and hormones in human carcinomas. In addition, the mechanisms involved in SOCS1- and SOCS3-regulated abnormal development and activation of immune cells in carcinogenesis, including T cells, macrophages, dendritic cells, and myeloid-derived suppressor cells, are still unclear. Therefore, this study aims to further discuss the molecules and signal pathways regulating the expression and function of SOCS1 and SOCS3 in various types of cancers and elucidate the feasibility and efficiency of SOCS-based target therapeutic strategy in anticancer treatment. PMID:28228755

  10. FGF signaling enhances a Shh negative feedback loop to control initiation of spinal cord ventral patterning

    OpenAIRE

    2015-01-01

    A prevalent developmental mechanism for the assignment of cell identities is the production of spatiotemporal concentration gradients of extracellular signaling molecules that are interpreted by the responding cells. One of such signaling systems is the Shh gradient that controls neuronal subtype identity in the ventral spinal cord. Using loss and gain of function approaches in chick and mouse embryos, we show here that the fibroblast growth factor (FGF) signaling pathway is required to restr...

  11. Experimental investigation on nonlinear dynamics of 1550 nm VCSEL simultaneously subject to orthogonal optical injection and negative optoelectronic feedback

    Science.gov (United States)

    Deng, Tao; Xia, Guang-Qiong; Chen, Jian-Jun; Tang, Xi; Lin, Xiao-Dong; Yang, Xin; Huang, Shou-Wen; Wu, Zheng-Mao

    2017-04-01

    Nonlinear dynamic characteristics of a 1550 nm vertical-cavity surface-emitting laser (1550 nm VCSEL) simultaneously subject to orthogonal optical injection and negative optoelectronic feedback are experimentally investigated. The results show that, under suitable orthogonal optical injection the VCSEL can exhibit rich nonlinear dynamic behaviors such as stable state (S), period-one (P1), period-two (P2), chaos (CO), stable injection locking (SIL) and polarization switching (PS). After further introducing negative optoelectronic feedback with a certain feedback delay time, the dynamic distribution of the orthogonal optical injection 1550 nm VCSEL is significantly affected, and some new phenomena including three-frequency quasiperiodic (Q3) state can be observed. With the increase of optoelectronic feedback strength, the S and SIL regions typically are shrank, while the quasiperiodic (QP) and CO regions are enlarged.

  12. In vivo optical coherence tomography of stimulus-evoked intrinsic optical signals in mouse retinas

    Science.gov (United States)

    Wang, Benquan; Lu, Yiming; Yao, Xincheng

    2016-09-01

    Intrinsic optical signal (IOS) imaging promises a noninvasive method for advanced study and diagnosis of eye diseases. Before pursuing clinical applications, it is essential to understand anatomic and physiological sources of retinal IOSs and to establish the relationship between IOS distortions and eye diseases. The purpose of this study was designed to demonstrate the feasibility of in vivo IOS imaging of mouse models. A high spatiotemporal resolution spectral domain optical coherence tomography (SD-OCT) was employed for depth-resolved retinal imaging. A custom-designed animal holder equipped with ear bar and bite bar was used to minimize eye movements. Dynamic OCT imaging revealed rapid IOS from the photoreceptor's outer segment immediately after the stimulation delivery, and slow IOS changes were observed from inner retinal layers. Comparative photoreceptor IOS and electroretinography recordings suggested that the fast photoreceptor IOS may be attributed to the early stage of phototransduction before the hyperpolarization of retinal photoreceptor.

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

    Science.gov (United States)

    Fazal, Muhammad Irfan

    may be possible. Recently, interest has increased in exploring the spatial dimension of light to increase capacity, both in fiber as well as free-space communication channels. The orbital angular momentum (OAM) of light, carried by Laguerre-Gaussian (LG) beams have the interesting property that, in theory, an infinite number of OAMs can be transmitted; which due to its inherent orthogonality will not affect each other. Thus, in theory, one can increase the channel capacity arbitrarily. However, in practice, the device dimensions will reduce the number of OAMs used. In addition to advanced modulation formats, it is expected that optical signal processing may play a role in the future development of more efficient optical transmission systems. The hope is that performing signal processing in the optical domain may reduce optical-to-electronic conversion inefficiencies, eliminate bottlenecks and take advantage of the ultrahigh bandwidth inherent in optics. While 40 to 50 Gbit/s electronic components are the peak of commercial technology and 100 Gbit/s capable RF components are still in their infancy, optical signal processing of these high-speed data signals may provide a potential solution. Furthermore, any optical processing system or sub-system must be capable of handling the wide array of data formats and data rates that networks may employ. The work presented in this Ph.D. dissertation attempts at addressing the issue of optical processing for advanced optical modulation formats, and particularly explores the state of the art in increasing the capacity of an optical link by a combination of wavelength/phase/polarization/OAM dimensions of light. Spatial multiplexing and demultiplexing of both coherently and directly detected signals at the 100 Gbit/s Ethernet standard is addressed. The application of a continuously tunable all-optical delay for all-optical functionality like time-slot interchange at high data-rates is presented. Moreover the interplay of chirp

  14. Machine Learning Techniques for Optical Performance Monitoring from Directly Detected PDM-QAM Signals

    DEFF Research Database (Denmark)

    Thrane, Jakob; Wass, Jesper; Piels, Molly

    2017-01-01

    Linear signal processing algorithms are effective in dealing with linear transmission channel and linear signal detection, while the nonlinear signal processing algorithms, from the machine learning community, are effective in dealing with nonlinear transmission channel and nonlinear signal...... detection. In this paper, a brief overview of the various machine learning methods and their application in optical communication is presented and discussed. Moreover, supervised machine learning methods, such as neural networks and support vector machine, are experimentally demonstrated for in-band optical...

  15. Activated PTHLH Coupling Feedback Phosphoinositide to G-Protein Receptor Signal-Induced Cell Adhesion Network in Human Hepatocellular Carcinoma by Systems-Theoretic Analysis

    Directory of Open Access Journals (Sweden)

    Lin Wang

    2012-01-01

    Full Text Available Studies were done on analysis of biological processes in the same high expression (fold change ≥2 activated PTHLH feedback-mediated cell adhesion gene ontology (GO network of human hepatocellular carcinoma (HCC compared with the corresponding low expression activated GO network of no-tumor hepatitis/cirrhotic tissues (HBV or HCV infection. Activated PTHLH feedback-mediated cell adhesion network consisted of anaphase-promoting complex-dependent proteasomal ubiquitin-dependent protein catabolism, cell adhesion, cell differentiation, cell-cell signaling, G-protein-coupled receptor protein signaling pathway, intracellular transport, metabolism, phosphoinositide-mediated signaling, positive regulation of transcription, regulation of cyclin-dependent protein kinase activity, regulation of transcription, signal transduction, transcription, and transport in HCC. We proposed activated PTHLH coupling feedback phosphoinositide to G-protein receptor signal-induced cell adhesion network. Our hypothesis was verified by the different activated PTHLH feedback-mediated cell adhesion GO network of HCC compared with the corresponding inhibited GO network of no-tumor hepatitis/cirrhotic tissues, or the same compared with the corresponding inhibited GO network of HCC. Activated PTHLH coupling feedback phosphoinositide to G-protein receptor signal-induced cell adhesion network included BUB1B, GNG10, PTHR2, GNAZ, RFC4, UBE2C, NRXN3, BAP1, PVRL2, TROAP, and VCAN in HCC from GEO dataset using gene regulatory network inference method and our programming.

  16. Improved performance of analog and digital acousto-optic modulation with feedback under profiled beam propagation for secure communication using chaos

    Science.gov (United States)

    Almehmadi, Fares S.; Chatterjee, Monish R.

    2014-12-01

    Using intensity feedback, the closed-loop behavior of an acousto-optic hybrid device under profiled beam propagation has been recently shown to exhibit wider chaotic bands potentially leading to an increase in both the dynamic range and sensitivity to key parameters that characterize the encryption. In this work, a detailed examination is carried out vis-à-vis the robustness of the encryption/decryption process relative to parameter mismatch for both analog and pulse code modulation signals, and bit error rate (BER) curves are used to examine the impact of additive white noise. The simulations with profiled input beams are shown to produce a stronger encryption key (i.e., much lower parametric tolerance thresholds) relative to simulations with uniform plane wave input beams. In each case, it is shown that the tolerance for key parameters drops by factors ranging from 10 to 20 times below those for uniform plane wave propagation. Results are shown to be at consistently lower tolerances for secure transmission of analog and digital signals using parameter tolerance measures, as well as BER performance measures for digital signals. These results hold out the promise for considerably greater information transmission security for such a system.

  17. Huwe1-mediated ubiquitylation of dishevelled defines a negative feedback loop in the Wnt signaling pathway

    NARCIS (Netherlands)

    de Groot, Reinoud E A; Ganji, Ranjani S; Bernatik, Ondrej; Lloyd-Lewis, Bethan; Seipel, Katja; Šedová, Kateřina; Zdráhal, Zbyněk; Dhople, Vishnu M; Dale, Trevor C; Korswagen, Hendrik C; Bryja, Vitezslav

    2014-01-01

    Wnt signaling plays a central role in development, adult tissue homeostasis, and cancer. Several steps in the canonical Wnt/β-catenin signaling cascade are regulated by ubiquitylation, a protein modification that influences the stability, subcellular localization, or interactions of target proteins.

  18. Nonlinear distortion evaluation in a directly modulated distributed feedback laser diode-based fiber-optic cable television transport system

    Science.gov (United States)

    Li, Chung-Yi; Ying, Cheng-Ling; Lin, Chun-Yu; Chu, Chien-An

    2015-12-01

    This study evaluated a directly modulated distributed feedback (DFB) laser diode (LD) for cable TV systems with respect to carrier-to-nonlinear distortion of LDs. The second-order distortion-to-carrier ratio is found to be proportional to that of the second-order coefficient-to-first-order coefficient of the DFB laser diode driving current and to the optical modulation index (OMI). Furthermore, the third-order distortion-to-carrier ratio is proportional to that of the third-order coefficient-to-first-order coefficient of the DFB laser diode driving current, and to the OMI2.

  19. Sideband locking of a single-section semiconductor distributed-feedback laser in an optical phase-lock loop.

    Science.gov (United States)

    Satyan, Naresh; Vasilyev, Arseny; Liang, Wei; Rakuljic, George; Yariv, Amnon

    2009-11-01

    The bandwidth and performance of optical phase-lock loops (OPLLs) using single-section semiconductor lasers (SCLs) are severely limited by the nonuniform frequency modulation response of the lasers. It is demonstrated that this restriction is eliminated by the sideband locking of a single-section distributed-feedback SCL to a master laser in a heterodyne OPLL, thus enabling a delay-limited loop bandwidth. The lineshape of the phase-locked SCL output is characterized using a delayed self-heterodyne measurement.

  20. Complex coupled distributed feedback laser monolithically integrated with electroabsorption modulator and semiconductor optical amplifier at 1.3-micrometer wavelength

    Science.gov (United States)

    Gerlach, Philipp; Peschke, Martin; Wenger, Thomas; Saravanan, Brem K.; Hanke, Christian; Lorch, Steffen; Michalzik, Rainer

    2006-04-01

    We report on the design and experimental results of monolithically integrated optoelectronic devices containing distributed feedback (DFB) laser, electroabsorption modulator (EAM), and semiconductor optical amplifier (SOA). Common InGaAlAs multiple quantum well (MQW) layers are used in all device sections. The incorporation of local lateral metal gratings in the DFB section enables device fabrication by single-step epitaxial growth. The emission wavelength is λ=1.3 micrometer. More than 2 mW single-mode fiber-coupled output power as well as 10 dB/2 V static extinction ratio have been achieved. Modulation experiments clearly show 10 Gbit/s capability.

  1. Photonic devices and systems for optical signal processing

    Science.gov (United States)

    Parker, Michael A.; Swanson, Paul D.; Libby, Stuart I.

    1993-08-01

    This report is a compilation of the preliminary designs, fabrication, and test results for multiquantum well optical amplifiers, stripe and square broad area lasers, mode switched optical memory elements, optical RS flip flops, NOR gates, photodetectors, and acousto-optic switches.

  2. Secure transmission of static and dynamic images via chaotic encryption in acousto-optic hybrid feedback with profiled light beams

    Science.gov (United States)

    Chatterjee, Monish R.; Almehmadi, Fares S.

    2015-01-01

    Secure information encryption via acousto-optic (AO) chaos with profiled optical beams indicates substantially better performance in terms of system robustness. This paper examines encryption of static and time-varying (video) images onto AO chaotic carriers using Gaussian-profile beams with diffracted data numerically generated using transfer functions. The use of profiled beams leads to considerable improvement in the encrypted signal. While static image encryption exhibits parameter tolerances within about +/-10% for uniform optical beams, profiled beams reduce the tolerance to less than 1%, thereby vastly improving both the overall security of the transmitted information as well as the quality of the image retrieval.

  3. Erbin loss promotes cancer cell proliferation through feedback activation of Akt-Skp2-p27 signaling

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Hao [Department of Pathophysiology, Institute of Basic Medical Sciences, Beijing 100850 (China); Laboratory of Cellular and Molecular Immunology, Medical School of Henan University, Kaifeng 475004 (China); Song, Yuhua [The Affiliated Hospital of Medical College, Qingdao University, Qingdao (China); Wu, Yan; Guo, Ning [Department of Pathophysiology, Institute of Basic Medical Sciences, Beijing 100850 (China); Ma, Yuanfang [Laboratory of Cellular and Molecular Immunology, Medical School of Henan University, Kaifeng 475004 (China); Qian, Lu, E-mail: mayf@henu.edu.cn [Department of Pathophysiology, Institute of Basic Medical Sciences, Beijing 100850 (China)

    2015-07-31

    Erbin localizes at the basolateral membrane to regulate cell junctions and polarity in epithelial cells. Dysregulation of Erbin has been implicated in tumorigenesis, and yet it is still unclear if and how disrupted Erbin regulates the biological behavior of cancer cells. We report here that depletion of Erbin leads to cancer cell excessive proliferation in vitro and in vivo. Erbin deficiency accelerates S-phase entry by down-regulating CDK inhibitors p21 and p27 via two independent mechanisms. Mechanistically, Erbin loss promotes p27 degradation by enhancing E3 ligase Skp2 activity though augmenting Akt signaling. Interestingly, we also show that Erbin is an unstable protein when the Akt-Skp2 signaling is aberrantly activated, which can be specifically destructed by SCF-Skp2 ligase. Erbin loss facilitates cell proliferation and migration in Skp2-dependent manner. Thus, our finding illustrates a novel negative feedback loop between Erbin and Akt-Skp2 signaling. It suggests disrupted Erbin links polarity loss, hyperproliferation and tumorigenesis. - Highlights: • Erbin loss leads to cancer cell excessive proliferation in vitro and in vivo. • Erbin loss accelerates cell cycle though down-regulating p21 and p27 expression. • Erbin is a novel negative modulator of Akt1-Skp2-p27 signaling pathway. • Our study suggests that Erbin loss contributes to Skp2 oncogenic function.

  4. Study of a distributed feedback diode laser based hygrometer combined Herriot-gas cell and waterless optical components

    Science.gov (United States)

    Wei, Yubin; Chang, Jun; Lian, Jie; Wang, Qiang; Wei, Wei

    2016-09-01

    A distributed feedback diode laser (DFB-DL) based hygrometer combined with a long-path-length Herriot gas cell and waterless optical components was proposed and investigated. The main function of this sensor was to simultaneously improve the measurement reliability and resolution. A comparison test between a 10-cm normal transmission-type gas cell and a 3-m Herriot gas cell was carried out to demonstrate the improvement. Reliability improvement was achieved by influence suppression of water vapor inside optical components (WVOC) through combined action of the Herriot gas cell and waterless optical components. The influence of WVOC was suppressed from 726 ppmv to 25 ppmv using the Herriot gas cell. Moreover, combined with waterless optical components, the influence of WVOC was further suppressed to no more than 4 ppmv. Resolution improvement from 11.7 ppmv to 0.32 ppmv was achieved mainly due to the application of the long-path-length Herriot gas cell. The results show that the proposed sensor has a good performance and considerable potential application in gas sensing, especially when probed gas possibly permeates into optical components.

  5. Experimental investigation of wavelength-selective optical feedback for a high-power quantum dot superluminescent device with two-section structure.

    Science.gov (United States)

    Li, Xinkun; Jin, Peng; An, Qi; Wang, Zuocai; Lv, Xueqin; Wei, Heng; Wu, Jian; Wu, Ju; Wang, Zhanguo

    2012-05-21

    In this work, a high-power and broadband quantum dot superluminescent diode (QD-SLD) is achieved by using a two-section structure. The QD-SLD device consists of a tapered titled ridge waveguide section supplying for high optical gain and a straight titled ridge waveguide section to tune optical feedback from the rear facet of the device. The key point of our design is to achieve the wavelength-selective optical feedback to the emission of the QDs' ground state (GS) and 1st excited state (ES) by tuning the current densities injected in the straight titled section. With GS-dominant optical feedback under proper current-injection of the straight titled region, a high output power of 338 mW and a broad bandwidth of 65 nm is obtained simultaneously by the contribution associated to the QDs' GS and 1st ES emission.

  6. Time to task failure varies with the gain of the feedback signal for women, but not for men.

    Science.gov (United States)

    Mottram, Carol J; Hunter, Sandra K; Rochette, Ludo; Anderson, Melissa K; Enoka, Roger M

    2006-10-01

    Varying the gain of the feedback signal during a target-matching task alters the synaptic input onto the motor neuron pool. The purpose was to determine the influence of the gain of the feedback signal on the time to failure for men and women when maintaining arm position while supporting a submaximal inertial load with the elbow flexor muscles. While seated with the upper arm vertical, 15 women and 14 men maintained a constant elbow angle (1.57 rad) and supported a load equal to 15% of maximal voluntary contraction (MVC) force until failure. The task was performed on separate days with either a low gain or a high gain for the joint-angle signal. The percent decline in MVC force after the fatiguing contraction was similar for the low- and high-gain conditions (P = 0.24), and did not differ for men and women (P = 0.11). The discharge of motor units in biceps brachii declined at a greater rate during the high-gain condition for men and women, but only the women experienced a briefer time to failure for the high-gain session (8.7 +/- 2.3 min) compared with the low-gain session (11.9 +/- 4.8; P = 0.003). The men had similar times to failure for the low- (6.0 +/- 2.2 min) and high-gain conditions (5.9 +/- 2.1 min; P = 0.35). Linear and stepwise, multiple-regression analyses revealed that the time to failure for the men was associated with the absolute target force, the standard deviation (SD) for the resultant wrist acceleration, and the brachialis aEMG (P women was associated with the rate of decline in motor unit discharge, the SD for the resultant wrist acceleration, and the changes in mean arterial pressure and heart rate (P men and women.

  7. Modeling of semiconductor devices for high-speed all-optical signal processing

    DEFF Research Database (Denmark)

    Bischoff, Svend; Højfeldt, Sune; Mørk, Jesper

    2001-01-01

    The all-optical signal processing performance of devices based on active semiconductor waveguides is investigated. A large signal model is used to analyse the physical mechanisms limiting the high-speed performance of both semiconductor optical amplifiers (SOAs) and electro-absorption modulators ...

  8. Control of chaos in an external-cavity multi-quantum-well laser subjected to dual-wedges and optical dual-feedback

    Institute of Scientific and Technical Information of China (English)

    YAN SenLin

    2009-01-01

    A multi-parameter chaos-control method used to control chaos in an external cavity multi-quantum-well (MQW) laser via the dual-wedges and external delayed optical dual-feedback is presented. The physical model of the laser dynamic is established under the conditions of the dual-wedges and dual-feedback light control. The frequency detuning and stable ranges of the control system are theoretically demon-strated. The optical-length of the feedback light may be adjusted by shifting horizontally or sliding the dual-wedges relatively in the external optical road, which will alter the delaying time and feedback in-tensity of the dual-feedback light. Accordingly, the multi-parameter chaos-control of the optical dual-feedback may be achieved physically. The numerical simulations approve that the chaotic laser may be controlled into a stable state, a single-periodic state and multi-periodic states, and the con-trolled periodic pulse power may be increased.

  9. Enhancing Performance of Optical Communication Systems with Advanced Optical Signal Processing

    Directory of Open Access Journals (Sweden)

    Ivan Glesk

    2010-11-01

    Full Text Available Growing needs to transport large amount of data, penetration of multimedia into our daily lives, and quickly expanding e-Commerce sector triggered an unparallel demand for the new generation of fast, secure, and energy savvy communication networks.Today we already benefit from many advances which revolutionized data and voice communication. Commercially deployed Dense Wavelength Division Multiple Access (DWDMA networks today are capable of transporting tens of Gigabits of data per second over a single WDM channel thus offering tremendous aggregate data throughputs over a single optical fibre. As a consequence, new bottlenecks have emerged at the fibre endpoints where data detection, routing, and switching must take place. Today's routers use electronics to process all incoming optical traffic. However the available bandwidth offered by current electronics can no longer keep up with these rapidly growing demands. To address these challenges and with goal in mind to eliminate this bottleneck, the research community has been looking long and hard for appropriate alternative solutions. One of taken approaches can be described as optical signal processing. As we will demonstrate it can be very powerful tool to improve performance of advanced communication networks especially when coupled with technologies and approaches which will enable device integration and packaging.

  10. Eavesdropping in chaotic optical communication using the feedback length of an external-cavity laser as a key.

    Science.gov (United States)

    Zhao, Qingchun; Wang, Yuncai; Wang, Anbang

    2009-06-20

    An external-cavity laser (ECL) operating in a chaotic state is usually used in a chaotic optical secure communication system and its feedback length (FL) is often regarded as an additional key. Our analyses show that an eavesdropper's (Eve) laser can synchronize with a transmitter (Alice) without any knowledge of the FL by simply increasing the injection strength. A sequence of a 1 Gbit/s nonreturn-to-zero message encoded by the FL as the key is successfully eavesdropped. The reason for the synchronization deviation between Alice's and Eve's lasers is given. Our results indicate that the FL as a key cannot enhance the security of chaotic optical communication using long-ECLs.

  11. Encryption and validation of multiple signals for optical identification systems

    Energy Technology Data Exchange (ETDEWEB)

    Perez-Cabre, E [Universitat PoliteGcnica de Catalunya, Department Optica i Optometria, Violinista Vellsola 37, 08222 Terrassa (Spain); Millan, M S [Universitat PoliteGcnica de Catalunya, Department Optica i Optometria, Violinista Vellsola 37, 08222 Terrassa (Spain); Javidi, B [University of Connecticut, Electrical and Computer Engineering Department, 371 Fairfield Road, CT 06269 Storrs (United States)

    2007-07-15

    Multifactor encryption-authentication technique reinforces optical security by allowing the simultaneous A N D-verification of more than one primary image. Instead of basing the identification on a unique signature or piece of information, our goal is to authenticate a given person, object, vehicle by the simultaneous recognition of several factors. Some of them are intrinsic to the person and object or vehicle under control. Other factors, act as keys of the authentication step. Such a system is proposed for situations such as the access control to restricted areas, where the demand of security is high. The multifactor identification method involves double random-phase encoding, fully phase-based encryption and a combined nonlinear joint transform correlator and a classical 4f-correlator for simultaneous recognition and authentication of multiple images. The encoded signal fulfils the general requirements of invisible content, extreme difficulty in counterfeiting and real-time automatic verification. Four reference double-phase encoded images are compared with the retrieved input images obtained in situ from the person or the vehicle whose authentication is wanted and from a database. A recognition step based on the correlation between the signatures and the stored references determines the authentication or rejection of the person and object under surveillance.

  12. In vivo intrinsic optical signal imaging of mouse retinas

    Science.gov (United States)

    Wang, Benquan; Yao, Xincheng

    2016-03-01

    Intrinsic optical signal (IOS) imaging is a promising noninvasive method for advanced study and diagnosis of eye diseases. Before pursuing clinical applications, more IOS studies employing animal models are necessary to establish the relationship between IOS distortions and eye diseases. Ample mouse models are available for investigating the relationship between IOS distortions and eye diseases. However, in vivo IOS imaging of mouse retinas is challenging due to the small ocular lens (compared to frog eyes) and inevitable eye movements. We report here in vivo IOS imaging of mouse retinas using a custom-designed functional OCT. The OCT system provided high resolution (3 μm) and high speed (up to 500 frames/s) imaging of mouse retinas. An animal holder equipped with a custom designed ear bar and bite bar was used to minimize eye movement due to breathing and heartbeats. Residual eye movement in OCT images was further compensated by accurate image registration. Dynamic OCT imaging revealed rapid IOSs from photoreceptor outer segments immediately (IOS changes were also observed from inner retinal layers with delayed time courses compared to that of photoreceptor IOSs.

  13. Studies of beam expansion and distributed Bragg reflector lasers for fiber optics and optical signal processing. Interim report

    Energy Technology Data Exchange (ETDEWEB)

    Garmire, E.M.

    1981-03-03

    Separate studies were performed on beam expansion and on Distributed Bragg Reflector (DBR) lasers preliminary to monolithic integration on GaAs substrates. These components are proposed for use in optical signal processing, for fiber optic sources and for high-brightness lasers.

  14. Optical Transmission of OFDM Ultra-wideband Signals beyond 40 Gb/s (Invited Paper

    Directory of Open Access Journals (Sweden)

    Y. Ben-Ezra

    2010-02-01

    Full Text Available We for the first time propose the highly efficient method of RF and optical signal mixing based on two different architectures: the parallel-RF/serial-optics architecture characterized by all-optical mixing for sub-carrier multiplexing, and the parallel-RF/parallel-optics architecture based on the array of 12x10 GHz components with directly modulated VCSELs and 12 multimode optical fibers. The main advantages of the both architectures are simplicity and low-cost implementation. We have carried out numerical simulations of ultra-wideband signals propagation in the proposed systems and proved the high efficiency and feasibility of the proposed method.

  15. Optical encryption/decryption of 8PSK signal using FWM-based modified XOR.

    Science.gov (United States)

    Zhang, Min; Cui, Yue; Zhan, Yueying; Zhang, Zhiguo; Chen, Xue

    2015-09-01

    A scheme for optical encryption/decryption of an eight-phase-shift keying (8PSK) signal is proposed, and this scheme applies modified optical XOR gates based on four-wave mixing (FWM) in a semiconductor optical amplifier (SOA). Theoretical analyses and simulations are conducted. Both the performance and the parameter design of a 40-Gbit/s all-optical encryption/decryption system under various key parameters are studied. The results are useful for designing optical encryption/decryption for complex modulated signals.

  16. Interleukin 6 promotes endometrial cancer growth through an autocrine feedback loop involving ERK–NF-κB signaling pathway

    Energy Technology Data Exchange (ETDEWEB)

    Che, Qi; Liu, Bin-Ya; Wang, Fang-Yuan; He, Yin-Yan; Lu, Wen; Liao, Yun [Department of Obstetrics and Gynecology, Shanghai First People’s Hospital Affiliated to Shanghai Jiao Tong University, Shanghai (China); Gu, Wei, E-mail: krisgu70@163.com [Department of Obstetrics and Gynecology, International Peace Maternity and Child Health Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai (China); Wan, Xiao-Ping, E-mail: wanxp@sjtu.edu.cn [Department of Obstetrics and Gynecology, Shanghai First Maternity and Infant Hospital Affiliated to Tong Ji University, Shanghai (China)

    2014-03-28

    Highlights: • IL-6 could promote endometrial cancer cells proliferation. • IL-6 promotes its own production through an autocrine feedback loop. • ERK and NF-κB pathway inhibitors inhibit IL-6 production and tumor growth. • IL-6 secretion relies on the activation of ERK–NF-κB pathway axis. • An orthotopic nude endometrial carcinoma model confirms the effect of IL-6. - Abstract: Interleukin (IL)-6 as an inflammation factor, has been proved to promote cancer proliferation in several human cancers. However, its role in endometrial cancer has not been studied clearly. Previously, we demonstrated that IL-6 promoted endometrial cancer progression through local estrogen biosynthesis. In this study, we proved that IL-6 could directly stimulate endometrial cancer cells proliferation and an autocrine feedback loop increased its production even after the withdrawal of IL-6 from the medium. Next, we analyzed the mechanism underlying IL-6 production in the feedback loop and found that its production and IL-6-stimulated cell proliferation were effectively blocked by pharmacologic inhibitors of nuclear factor-kappa B (NF-κB) and extra-cellular signal-regulated kinase (ERK). Importantly, activation of ERK was upstream of the NF-κB pathways, revealing the hierarchy of this event. Finally, we used an orthotopic nude endometrial carcinoma model to confirm the effects of IL-6 on the tumor progression. Taken together, these data indicate that IL-6 promotes endometrial carcinoma growth through an expanded autocrine regulatory loop and implicate the ERK–NF-κB pathway as a critical mediator of IL-6 production, implying IL-6 to be an important therapeutic target in endometrial carcinoma.

  17. Basal-subtype and MEK-Pl3K feedback signaling determine susceptibility of breast cancer cells to MEK inhibition

    Energy Technology Data Exchange (ETDEWEB)

    Mirzoeva, Olga K.; Das, Debopriya; Heiser, Laura M.; Bhattacharya, Sanchita; Siwak, Doris; Gendelman, Rina; Bayani, Nora; Wang, Nicholas J.; Neve, Richard M.; Knight, Zachary; Feiler, Heidi S.; Gascard, Philippe; Parvin, Bahram; Spellman, Paul T.; Shokat, Kevan M.; Wyrobek, Andrew J.; Bissell, Mina J.; McCormick, Frank; Kuo, Wen-Lin; Mills, Gordon B.; Gray, Joe W.; Korn, W. Michael

    2009-01-23

    Specific inhibitors of MEK have been developed that efficiently inhibit the oncogenic RAF-MEK-ERK pathway. We employed a systems-based approach to identify breast cancer subtypes particularly susceptible to MEK inhibitors and to understand molecular mechanisms conferring resistance to such compounds. Basal-type breast cancer cells were found to be particularly susceptible to growth-inhibition by small-molecule MEK inhibitors. Activation of the PI3 kinase pathway in response to MEK inhibition through a negative MEK-EGFR-PI3 kinase feedback loop was found to limit efficacy. Interruption of this feedback mechanism by targeting MEK and PI3 kinase produced synergistic effects, including induction of apoptosis and, in some cell lines, cell cycle arrest and protection from apoptosis induced by proapoptotic agents. These findings enhance our understanding of the interconnectivity of oncogenic signal transduction circuits and have implications for the design of future clinical trials of MEK inhibitors in breast cancer by guiding patient selection and suggesting rational combination therapies.

  18. Integrated optical fiber lattice accumulators

    OpenAIRE

    Atherton, Adam F

    1997-01-01

    Approved for public release; distribution is unlimited. Sigma-delta modulators track a signal by accumulating the error between an input signal and a feedback signal. The accumulated energy is amplitude analyzed by a comparator. The comparator output signal is fed back and subtracted from the input signal. This thesis is primarily concerned with designing accumulators for inclusion in an optical sigma-delta modulator. Fiber lattice structures with optical amplifiers are used to perform the...

  19. Use of semiconductor optical amplifiers in signal processing applications

    OpenAIRE

    Manning, Robert J.; Webb, Rod P.; Dailey, James M.; Maxwell, Graeme D.; Poustie, Alistair J.; Lardenois, Sébastien; Cotter, David

    2010-01-01

    We describe a 42.6 Gbit/s all-optical pattern recognition system which uses semiconductor optical amplifiers (SOAs). A circuit with three SOA-based logic gates is used to identify the presence of specific port numbers in an optical packet header.

  20. Negative feedback regulation of Wnt signaling via N-linked fucosylation in zebrafish.

    Science.gov (United States)

    Feng, Lei; Jiang, Hao; Wu, Peng; Marlow, Florence L

    2014-11-15

    L-fucose, a monosaccharide widely distributed in eukaryotes and certain bacteria, is a determinant of many functional glycans that play central roles in numerous biological processes. The molecular mechanism, however, by which fucosylation mediates these processes remains largely elusive. To study how changes in fucosylation impact embryonic development, we up-regulated N-linked fucosylation via over-expression of a key GDP-Fucose transporter, Slc35c1, in zebrafish. We show that Slc35c1 overexpression causes elevated N-linked fucosylation and disrupts embryonic patterning in a transporter activity dependent manner. We demonstrate that patterning defects associated with enhanced N-linked fucosylation are due to diminished canonical Wnt signaling. Chimeric analyses demonstrate that elevated Slc35c1 expression in receiving cells decreases the signaling range of Wnt8a during zebrafish embryogenesis. Moreover, we provide biochemical evidence that this decrease is associated with reduced Wnt8 ligand and elevated Lrp6 coreceptor, which we show are both substrates for N-linked fucosylation in zebrafish embryos. Strikingly, slc35c1 expression is regulated by canonical Wnt signaling. These results suggest that Wnt limits its own signaling activity in part via up-regulation of a transporter, slc35c1 that promotes terminal fucosylation and thereby limits Wnt activity.

  1. Preliminary Investigation of an Integrated Optic Sampler for HF Signals

    Science.gov (United States)

    1994-04-01

    fibre optic links). The response is reasonably flat out to -3 GHz, dropping to -3 dBc at -4.8 GHz. The S1 1 reflection coefficient rapidly approaches 0...sampling rate can probably be extended to -8 GHz by using a 1 GHz SRD to gain-switch the laser, followed by a fibre optic multiplexing system to split...and the possibility of causing optical instability. This problem is easily avoided by inserting an optical isolator into the fibre optic line. 5

  2. Negative feedback from CaSR signaling to aquaporin-2 sensitizes vasopressin to extracellular Ca2.

    Science.gov (United States)

    Ranieri, Marianna; Tamma, Grazia; Di Mise, Annarita; Russo, Annamaria; Centrone, Mariangela; Svelto, Maria; Calamita, Giuseppe; Valenti, Giovanna

    2015-07-01

    We previously described that high luminal Ca(2+) in the renal collecting duct attenuates short-term vasopressin-induced aquaporin-2 (AQP2) trafficking through activation of the Ca(2+)-sensing receptor (CaSR). Here, we evaluated AQP2 phosphorylation and permeability, in both renal HEK-293 cells and in the dissected inner medullary collecting duct, in response to specific activation of CaSR with NPS-R568. In CaSR-transfected cells, CaSR activation drastically reduced the basal levels of AQP2 phosphorylation at S256 (AQP2-pS256), thus having an opposite effect to vasopressin action. When forskolin stimulation was performed in the presence of NPS-R568, the increase in AQP2-pS256 and in the osmotic water permeability were prevented. In the freshly isolated inner mouse medullar collecting duct, stimulation with forskolin in the presence of NPS-R568 prevented the increase in AQP2-pS256 and osmotic water permeability. Our data demonstrate that the activation of CaSR in the collecting duct prevents the cAMP-dependent increase in AQP2-pS256 and water permeability, counteracting the short-term vasopressin response. By extension, our results suggest the attractive concept that CaSR expressed in distinct nephron segments exerts a negative feedback on hormones acting through cAMP, conferring high sensitivity of hormone to extracellular Ca(2+). © 2015. Published by The Company of Biologists Ltd.

  3. The oncoprotein p28GANK establishes a positive feedback loop in β-catenin signaling

    Institute of Scientific and Technical Information of China (English)

    Li-wei Dong; Guang-zhen Yang; Yu-fei Pan; Yao Chen; Ye-xiong Tan; Rong-yang Dai; Yi-bin Ren; Jing Fu; Hong-yang Wang

    2011-01-01

    p28GANK (also known as PSMD10 or gankyrin) is a novel oncoprotein that is highly expressed in hepatocellular carcinoma (HCC). Through its interaction with various proteins, p28GANK mediates the degradation of the tumor suppressor proteins Rb and p53. Although p53 was reported to downregulate β-catenin, whether p28GANK is involved in the regulation of β-catenin remains uncertain. Here we report that both growth factors and Ras upregulate p28GANK expression through the activation of the phosphoinosttide 3-kinase-AKT pathway. Upregulation of p28GANK expression subsequently enhanced the transcription activity of β-catenin. This effect was observed in p53-deficient cells, suggesting a p53-independent mechanism for the p28GANK-mediated activation of β-catenin, p28GANK overexpression also reduced E-cadherin protein levels, leading to increased release of free β-catenin into the cytoplasm from the cadherin-bound pool. Interestingly, exogenous expression of p28GANK resulted in elevated expression of the endogenous protein. We also observed that both β-catenin and c-Myc were transcriptional activators of p28GANK, and a correlation between p28GANK overexpression and c-Myc, cyclin D1 and β-catenin activation in primary human HCC. Together, these results suggest that p28GANK expression is regulated by a positive feedback loop involving β-catenin, which may play a critical role in tumorigenesis and the progression of HCC.

  4. Feedback between intracellular flow, signaling and active stresses in Physarum plasmodial fragments

    Science.gov (United States)

    Zhang, Shun; Guy, Robert; Del Alamo, Juan Carlos

    2016-11-01

    Physarum polycephalum is a multinucleated slime mold whose endoplasm flows periodically driven by the contraction of its ectoplasm, a dense shell of F-actin cross-linked by myosin molecular motors and attached to the cell membrane. Ectoplasm contractions are regulated by calcium ions whose propagation is in turn governed by the flow. We study experimentally how this feedback leads to auto-oscillation by simultaneously measuring endoplasmic flow speed and rheological properties, the traction stresses between the ectoplasm and its substratum and the distribution of endoplasmic free calcium ions. We find that physarum fragments smaller than 100 microns remain round and stay in place. However, larger fragments break symmetry leading to sustained forward locomotion, in process that is reminiscent of an interfacial instability that seems to settle around two different limit cycles (traveling waves and standing waves). By using different adhesive coatings in the substratum we investigate the role of substratum friction in the emergence of coherent endoplasmic flow patterns and overall physarum fragment locomotion.

  5. Optical sampling of ultrahigh bitrate signals using highly nonlinear chalcogenide planar waveguides or tapered fibers

    Science.gov (United States)

    Van Erps, Jürgen; Luan, Feng; Pelusi, Mark D.; Mägi, Eric; Iredale, Tim; Madden, Steve; Choi, Duk Yong; Bulla, Douglas A.; Luther-Davies, Barry; Thienpont, Hugo; Eggleton, Benjamin J.

    2010-06-01

    As the bit rates of optical networks increase, the ability of accurate monitoring of optical waveforms has become increasingly important. In recent years, optical sampling has emerged as a technique to perform time-resolved measurements of optical data signals at high data rates with a bandwidth that cannot be reached by conventional photodetectors and oscilloscopes. In an optical sampling system, the optical signal is sampled in the optical domain by a nonlinear optical sampling gate before the resulting samples are converted to an electrical signal. This avoids the need for high bandwidth electronics if the optical sampling gate is operated with a modest repetition frequency. In this paper, we present an optical sampling system using the optical Kerr effect in a highly nonlinear chalcogenide device, enabling combined capability for femtosecond resolution and broadband signal wavelength tunability. A temporal resolution 450-fs is achieved using four-wave mixing (FWM) in dispersion-engineered chalcogenide waveguides: on one hand a 7-cm long planar waveguide (integrated on a photonic chip) and on the other hand a 5-cm long tapered fiber. The use of a short length, dispersion-shifted waveguide with ultrahigh nonlinearity (10000/W/km) enables high-resolution optical sampling without the detrimental effect of chromatic dispersion on the temporal distortion of the signal and sampling pulses, as well as their phase mismatch (which in turn would degrade the FWM efficiency and the sensitivity of the measurement). Using these chalcogenide devices, we successfully monitor a 640-Gb/s optical time-division multiplexing (OTDM) datastream, showcasing its potential for monitoring of signals at bitrates approaching and beyond Tb/s. We compare the advantages and disadvantages of both approaches and discuss fundamental limitations as well as potential improvements.

  6. Control of polarization signal distortion by frequency domain phase conjugation in optical fiber systems

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Optical frequency domain phase conjugation(FDPC) is based on phase conjuga-tion of spectrum of an input signal.It is equivalent to the phase conjugation and the time reversal of the temporal envelope of an input signal.The use of FDPC to con-trol polarization signal distortion in birefringent optical fiber systems is proposed.Evolution of polarization signals in the system using midway FDPC is analyzed theoretically and simulated numerically.It is shown that the distortion of polariza-tion signals can be controlled effectively by FDPC.The impairments due to disper-sion and nonlinear effects can be suppressed simultaneously.

  7. Control of polarization signal distortion by frequency domain phase conjusation in optical fiber systems

    Institute of Scientific and Technical Information of China (English)

    BU Yang; WANG XiangZhao

    2008-01-01

    Optical frequency domain phase conjugation (FDPC) is based on phase conjugation of spectrum of an input signal. It is equivalent to the phase conjugation and the time reversal of the temporal envelope of an input signal. The use of FDPC to con-trol polarization signal distortion in birefringent optical fiber systems is proposed. Evolution of polarization signals in the system using midway FDPC is analyzed theoretically and simulated numerically. It is shown that the distortion of polariza-tion signals can be controlled effectively by FDPC. The impairments due to disper-sion and nonlinear effects can be suppressed simultaneously.

  8. Optical Nerve Detection by Diffuse Reflectance Spectroscopy for Feedback Controlled Oral and Maxillofacial Laser Surgery

    Directory of Open Access Journals (Sweden)

    Douplik Alexandre

    2011-02-01

    Full Text Available Abstract Background Laser surgery lacks haptic feedback, which is accompanied by the risk of iatrogenic nerve damage. It was the aim of this study to investigate diffuse reflectance spectroscopy for tissue differentiation as the base of a feedback control system to enhance nerve preservation in oral and maxillofacial laser surgery. Methods Diffuse reflectance spectra of nerve tissue, salivary gland and bone (8640 spectra of the mid-facial region of ex vivo domestic pigs were acquired in the wavelength range of 350-650 nm. Tissue differentiation was performed using principal component (PC analysis followed by linear discriminant analysis (LDA. Specificity and sensitivity were calculated using receiver operating characteristic (ROC analysis and the area under curve (AUC. Results Five PCs were found to be adequate for tissue differentiation with diffuse reflectance spectra using LDA. Nerve tissue could be differed from bone as well as from salivary gland with AUC results of greater than 88%, sensitivity of greater than 83% and specificity in excess of 78%. Conclusions Diffuse reflectance spectroscopy is an adequate technique for nerve identification in the vicinity of bone and salivary gland. The results set the basis for a feedback system to prevent iatrogenic nerve damage when performing oral and maxillofacial laser surgery.

  9. In vivo Microscale Measurements of Light and Photosynthesis during Coral Bleaching: Evidence for the Optical Feedback Loop?

    Science.gov (United States)

    Wangpraseurt, Daniel; Holm, Jacob B; Larkum, Anthony W D; Pernice, Mathieu; Ralph, Peter J; Suggett, David J; Kühl, Michael

    2017-01-01

    Climate change-related coral bleaching, i.e., the visible loss of zooxanthellae from the coral host, is increasing in frequency and extent and presents a major threat to coral reefs globally. Coral bleaching has been proposed to involve accelerating light stress of their microalgal endosymbionts via a positive feedback loop of photodamage, symbiont expulsion and excess in vivo light exposure. To test this hypothesis, we used light and O2 microsensors to characterize in vivo light exposure and photosynthesis of Symbiodinium during a thermal stress experiment. We created tissue areas with different densities of Symbiodinium cells in order to understand the optical properties and light microenvironment of corals during bleaching. Our results showed that in bleached Pocillopora damicornis corals, Symbiodinium light exposure was up to fivefold enhanced relative to healthy corals, and the relationship between symbiont loss and light enhancement was well-described by a power-law function. Cell-specific rates of Symbiodinium gross photosynthesis and light respiration were enhanced in bleached P. damicornis compared to healthy corals, while areal rates of net photosynthesis decreased. Symbiodinium light exposure in Favites sp. revealed the presence of low light microniches in bleached coral tissues, suggesting that light scattering in thick coral tissues can enable photoprotection of cryptic symbionts. Our study provides evidence for the acceleration of in vivo light exposure during coral bleaching but this optical feedback mechanism differs between coral hosts. Enhanced photosynthesis in relation to accelerating light exposure shows that coral microscale optics exerts a key role on coral photophysiology and the subsequent degree of radiative stress during coral bleaching.

  10. In vivo Microscale Measurements of Light and Photosynthesis during Coral Bleaching: Evidence for the Optical Feedback Loop?

    Science.gov (United States)

    Wangpraseurt, Daniel; Holm, Jacob B.; Larkum, Anthony W. D.; Pernice, Mathieu; Ralph, Peter J.; Suggett, David J.; Kühl, Michael

    2017-01-01

    Climate change-related coral bleaching, i.e., the visible loss of zooxanthellae from the coral host, is increasing in frequency and extent and presents a major threat to coral reefs globally. Coral bleaching has been proposed to involve accelerating light stress of their microalgal endosymbionts via a positive feedback loop of photodamage, symbiont expulsion and excess in vivo light exposure. To test this hypothesis, we used light and O2 microsensors to characterize in vivo light exposure and photosynthesis of Symbiodinium during a thermal stress experiment. We created tissue areas with different densities of Symbiodinium cells in order to understand the optical properties and light microenvironment of corals during bleaching. Our results showed that in bleached Pocillopora damicornis corals, Symbiodinium light exposure was up to fivefold enhanced relative to healthy corals, and the relationship between symbiont loss and light enhancement was well-described by a power-law function. Cell-specific rates of Symbiodinium gross photosynthesis and light respiration were enhanced in bleached P. damicornis compared to healthy corals, while areal rates of net photosynthesis decreased. Symbiodinium light exposure in Favites sp. revealed the presence of low light microniches in bleached coral tissues, suggesting that light scattering in thick coral tissues can enable photoprotection of cryptic symbionts. Our study provides evidence for the acceleration of in vivo light exposure during coral bleaching but this optical feedback mechanism differs between coral hosts. Enhanced photosynthesis in relation to accelerating light exposure shows that coral microscale optics exerts a key role on coral photophysiology and the subsequent degree of radiative stress during coral bleaching. PMID:28174567

  11. [Measurement of Trace C2H6 Based on Optical-Feedback Cavity-Enhanced Absorption Spectroscopy].

    Science.gov (United States)

    Wan, Fu; Chen, Wei-gen; Gu, Zhao-liang; Zou, Jing-xin; DU, Ling-Ling; Qi, Wei; Zhou, Qu

    2015-10-01

    Ethane is one of major fault characteristic gases dissolved in power transformer, the detection of Ethane with high accuracy and sensitivity is the key of dissolved gas analysis. In this paper, based on optical feedback theory and cavity-enhanced absorption spectroscopy, combined with quantum cascade laser, a detection system for dissolved gas C2 H6 in transformer oil was built up. Based on the symmetry of the individual cavity modes, the phase matching of returning light in resonance with the cavity was achieved through LabVIEW codes. The optical feedback effect that the emitted light return to the laser cavity after a small delay time and lock to the resonance frequency of cavity, even and odd modes effect that the higher modes and lower modes structure will build up alternatively, and threshold current lowering effect of about 1.2 mA were studied and achieved. By cavity ring-down spectroscopy, the effective reflectivity of 99.978% and cavity finesse of 7 138.4 is obtained respectively. The frequency selectivity is 0.005 2 cm(-1). With an acquisition time of 1s, this optical system allows detection for the PQ3 band of C2 H6 with high accuracy of 95.72% ± 0.17% and detection limit of (1.97 ± 0.06) x 10(-3) μL x L(-1) at atmospheric pressure and temperature of 20 degrees C, which lays a foundation for fault diagnose from dissolved gas analysis.

  12. Suppression of phase-induced intensity noise in fibre optic delay line signal processors using an optical phase modulation technique.

    Science.gov (United States)

    Chan, Erwin H W

    2010-10-11

    A technique that can suppress the dominant phase-induced intensity noise in fibre optic delay line signal processors is presented. It is based on phase modulation of the optical carrier to distribute the phase noise at the information band into a high frequency band which can be filtered out. This technique is suitable for suppressing the phase noise in various delay line structures and for integrating in the conventional fibre optic links. It can also suppress the coherent interference effect at the same time. A model for predicting the amount of phase noise reduction in various delay line structures using the optical phase modulation technique is presented for the first time and is experimentally verified. Experimental results demonstrate the technique can achieve a large phase noise reduction in various fibre optic delay line signal processors.

  13. Real-time digital signal processing for live electro-optic imaging.

    Science.gov (United States)

    Sasagawa, Kiyotaka; Kanno, Atsushi; Tsuchiya, Masahiro

    2009-08-31

    We present an imaging system that enables real-time magnitude and phase detection of modulated signals and its application to a Live Electro-optic Imaging (LEI) system, which realizes instantaneous visualization of RF electric fields. The real-time acquisition of magnitude and phase images of a modulated optical signal at 5 kHz is demonstrated by imaging with a Si-based high-speed CMOS image sensor and real-time signal processing with a digital signal processor. In the LEI system, RF electric fields are probed with light via an electro-optic crystal plate and downconverted to an intermediate frequency by parallel optical heterodyning, which can be detected with the image sensor. The artifacts caused by the optics and the image sensor characteristics are corrected by image processing. As examples, we demonstrate real-time visualization of electric fields from RF circuits.

  14. Multi-band local microwave signal generation based on an optical frequency comb generator

    Science.gov (United States)

    Wang, Wen Ting; Liu, Jian Guo; Sun, Wen Hui; Chen, Wei; Zhu, Ning Hua

    2015-03-01

    We propose and experimental demonstrate a new method to generate multi-band local microwave signals based on an optical frequency comb generator (OFCG) by applying an optical sideband injection locking technique and an optical heterodyning technique. The generated microwave signal can cover multi bands from S band to Ka band. A tunable multiband microwave signal spanning from 5 GHz to 40 GHz can be generated by the beating between the optical carrier and injection locked modulation sidebands in a photodetector without an optical filter. The wavelength of the slave laser can be continuously and near-linearly adjusted by proper changing its bias current. By tuning the bias current of the slave laser, the wavelength of that is matched to one of the modulation sidebands of the OFCG. The performance of the arrangement in terms of the tunability and stability of the generated microwave signal is also studied.

  15. A Multi-Functional Planar Lightwave Circuit for Optical Signal Processing Applications

    Science.gov (United States)

    Samadi, Payman

    Ultrafast optical signal processing is now a necessary tool in several domains of science and technology such as high-speed telecommunication, biomedicine, microscopy and radar systems. Optical arbitrary waveform generation is an optical signal processing function which has applications in optical telecommunication networks, sampling, and photonically-assisted RF waveform generation. Furthermore, performing optical signal processing in photonic integrated circuits is crucial for system integration and overcoming the speed limitations in electrical to optical conversion. In this thesis, we introduce a silica-based planar lightwave circuit which performs several optical signal processing functions. We start by reviewing the material system used to fabricate the device. We justify the choice of the material for our application and explain the fabrication process and the experiments to characterize the device. Then we introduce the fundamental theory of our device which is based on pulse repetition rate multiplication (PRRM) and shaping. We review the theory of direct time-domain approach to perform the PRRM and shaping. Experiments to measure the impulse response of the device, perform PRRM and polarization dependence characterization is shown as well. Three main applications of our device is presented next. First we use the PLC device with non-linear optics to generate multiple pulse trains at different wavelengths and different repetition rates. Second, we use the fundamental of the previous application to perform demultiplexing of optical time division multiplexed signals. Our approach is flexible in a sense that it can demultiplex any tributary channel of lower rate data, also it works for both amplitude and phase modulated data. Finally, using the second generation of our PLC device, we photonically generate radio frequency waveforms. We are able to generate various pulse shapes which are generally hard to generate using electronics at frequencies up to 80 GHz

  16. [Changes in the power of cat EEG rhythms during training with acoustic feedback signals].

    Science.gov (United States)

    Fokina, Iu O; Kulichenko, A M; Pavlenko, V B

    2009-01-01

    Dynamics of power relation between beta and theta rhythms and activity of dopaminergic neurons in the ventral tegmentum were studied in chronic EEG biofeedback experiments in two waking cats. EEG biofeedback training was based on a developed scheme, in which the level of a presented sound signal decreased if the ratio of power of beta and theta rhythms recorded in the frontal area increased (due to the increase in the beta-rhythm power and decrease in the power of the theta rhythm). These changes were accompanied by the increase in the activity of tegmental neurons presumably dopaminergic.

  17. Power-efficient method for IM-DD optical transmission of multiple OFDM signals.

    Science.gov (United States)

    Effenberger, Frank; Liu, Xiang

    2015-05-18

    We propose a power-efficient method for transmitting multiple frequency-division multiplexed (FDM) orthogonal frequency-division multiplexing (OFDM) signals in intensity-modulation direct-detection (IM-DD) optical systems. This method is based on quadratic soft clipping in combination with odd-only channel mapping. We show, both analytically and experimentally, that the proposed approach is capable of improving the power efficiency by about 3 dB as compared to conventional FDM OFDM signals under practical bias conditions, making it a viable solution in applications such as optical fiber-wireless integrated systems where both IM-DD optical transmission and OFDM signaling are important.

  18. Interactions between Shh, Sostdc1 and Wnt signaling and a new feedback loop for spatial patterning of the teeth.

    Science.gov (United States)

    Cho, Sung-Won; Kwak, Sungwook; Woolley, Thomas E; Lee, Min-Jung; Kim, Eun-Jung; Baker, Ruth E; Kim, Hee-Jin; Shin, Jeon-Soo; Tickle, Cheryll; Maini, Philip K; Jung, Han-Sung

    2011-05-01

    Each vertebrate species displays specific tooth patterns in each quadrant of the jaw: the mouse has one incisor and three molars, which develop at precise locations and at different times. The reason why multiple teeth form in the jaw of vertebrates and the way in which they develop separately from each other have been extensively studied, but the genetic mechanism governing the spatial patterning of teeth still remains to be elucidated. Sonic hedgehog (Shh) is one of the key signaling molecules involved in the spatial patterning of teeth and other ectodermal organs such as hair, vibrissae and feathers. Sostdc1, a secreted inhibitor of the Wnt and Bmp pathways, also regulates the spatial patterning of teeth and hair. Here, by utilizing maternal transfer of 5E1 (an anti-Shh antibody) to mouse embryos through the placenta, we show that Sostdc1 is downstream of Shh signaling and suggest a Wnt-Shh-Sostdc1 negative feedback loop as a pivotal mechanism controlling the spatial patterning of teeth. Furthermore, we propose a new reaction-diffusion model in which Wnt, Shh and Sostdc1 act as the activator, mediator and inhibitor, respectively, and confirm that such interactions can generate the tooth pattern of a wild-type mouse and can explain the various tooth patterns produced experimentally.

  19. Pump-phase-noise-free optical wavelength data exchange between QAM signals with 50-GHz channel-spacing using coherent DFB pump.

    Science.gov (United States)

    Lu, Guo-Wei; Albuquerque, André; Puttnam, Benjamin J; Sakamoto, Takahide; Drummond, Miguel; Nogueira, Rogério; Kanno, Atsushi; Shinada, Satoshi; Wada, Naoya; Kawanishi, Tetsuya

    2016-02-22

    An important challenge for implementing optical signal processing functions such as wavelength conversion or wavelength data exchange (WDE) is to avoid the introduction of linear and nonlinear phase noise in the subsystem. This is particularly important for phase noise sensitive, high-order quadrature-amplitude modulation (QAM) signals. In this paper, we propose and experimentally demonstrate an optical data exchange scheme through cascaded 2nd-order nonlinearities in periodically-poled lithium niobate (PPLN) waveguides using coherent pumping. The proposed coherent pumping scheme enables noise from the coherent pumps to be cancelled out in the swapped data after WDE, even with broad linewidth distributed feedback (DFB) pump lasers. Hence, this scheme allows phase noise tolerant processing functions, enabling the low-cost implementation of WDE for high-order QAM signals. We experimentally demonstrate WDEs between 10-Gbaud 4QAM (4QAM) signal and 12.5-Gbaud 4QAM (16QAM) signal with 3.5-MHz linewidth DFB pump lasers and 50-GHz channel spacing. Error-free operation is observed for the swapped QAM signals with coherent DFB pumping whilst use of free-running DFB pumps leads to visible error floors and unrecoverable phase errors. The phase noise cancellation in the coherent pump scheme is further confirmed by study of the recovered carrier phase of the converted signals. In addition to pump phase noise, the influence of crosstalk caused by the finite extinction ratio in WDE is also experimentally investigated for the swapped QAM signals.

  20. Modeling of semiconductor devices for high-speed all-optical signal processing

    DEFF Research Database (Denmark)

    Bischoff, Svend; Højfeldt, Sune; Mørk, Jesper

    2001-01-01

    The all-optical signal processing performance of devices based on active semiconductor waveguides is investigated. A large signal model is used to analyse the physical mechanisms limiting the high-speed performance of both semiconductor optical amplifiers (SOAs) and electro-absorption modulators...... (EAMs). Wavelength conversion and signal regeneration in EAMs is discussed at 10 and 40 Gbit/s. The finite carrier sweep-out time is shown to limit the EAM performance. Four-wave mixing (FWM) in SOAs is almost instantaneous. However, with increasing bit rates and advanced processing functionalities some...... limitations arise. These limitations are elucidated by studying bi-directional simultaneous clear and drop (de-multiplexing) for a 4x40 Gbit/s signal. The simultaneous clearing and de-multiplexing (drop) of an optical time division multiplexing signal channel for an 8x40 Gbit/s signal is investigated...

  1. Detection of HO2 in an atmospheric pressure plasma jet using optical feedback cavity-enhanced absorption spectroscopy

    Science.gov (United States)

    Gianella, Michele; Reuter, Stephan; Lawry Aguila, Ana; Ritchie, Grant A. D.; van Helden, Jean-Pierre H.

    2016-11-01

    Cold non-equilibrium atmospheric pressure plasma jets are increasingly applied in material processing and plasma medicine. However, their small dimensions make diagnosing the fluxes of generated species a challenge. Here we report on the detection of the hydroperoxyl radical, HO2, in the effluent of a plasma jet by the use of optical feedback cavity-enhanced absorption spectroscopy. The spectrometer has a minimum detectable absorption coefficient {α }\\min of 2.25× {10}-10 cm-1 with a 100 second acquisition, equivalent to 5.5× {10}12 {{cm}}-3 of HO2 (under ideal conditions). Concentrations in the range of (3.1-7.8) × 1013 cm-3 were inferred in the 4 mm wide effluent of the plasma jet.

  2. The effect of a feedback signal in a computer mouse on hovering behaviour, productivity, comfort and usability in a field study

    NARCIS (Netherlands)

    Kraker, H. de; Korte, E. de; Mil, F. van; Rijs, B.; Bongers, P.

    2008-01-01

    The aim of this study was to determine the effect of a tactile feedback signal on hovering behaviour, productivity, usability and comfort after 1 week of using an experimental mouse. In a randomized controlled trial, a regular computer mouse was compared to a new developed mouse with a tactile, vibr

  3. Signal generation and processing at 100 Gb/s based on optical time division multiplexing

    Institute of Scientific and Technical Information of China (English)

    Li HUO; Qiang WANG; Yanfei XING; Caiyun LOU

    2013-01-01

    In this paper, we review our recent works in 100 Gb/s signal generation and processing. A high-speed 100 Gb/s system with on-off keying (0OK) modulation format is implemented by using optical time division multiplexing (OTDM) method. As modifications of this system, simultaneous multicolor optical signal generation and 100Gb/s return-to-zero (RZ)-to-non-return-to-zero (NRZ) format conversion are presented. We also demonstrate basic all-optical signal processing functions of 100 GHz clock recovery and 100 Gb/s all-optical 2R generation based on semiconductor optical amplifiers (SOAs).

  4. Techniques for labeling of optical signals in bust switched networks

    DEFF Research Database (Denmark)

    Tafur Monroy, Idelfonso; Koonen, A. M. J.; Zhang, Jianfeng

    2003-01-01

    multiplexed (WDM) networks due to its single forwarding algorithm, thus yielding low latency, and it enables scaling to terabit rates. Moreover, LOBS is compatible with the general multiprotocol label switching (GMPLS) framework for a unified control plane. We present a review on techniques for labeling......We present a review of significant issues related to labeled optical burst switched (LOBS) networks and technologies enabling future optical internet networks. Labeled optical burst switching provides a quick and efficient forwarding mechanism of IP packets/bursts over wavelength division...

  5. Vision feedback driven automated assembly of photopolymerized structures by parallel optical trapping and manipulation

    DEFF Research Database (Denmark)

    Dam, Jeppe Seidelin; Perch-Nielsen, Ivan Ryberg; Rodrigo, Peter John

    2007-01-01

    We demonstrate how optical trapping and manipulation can be used to assemble microstructures. The microstructures we show being automatically recognized and manipulated are produced using the two-photon polymerization (2PP) technique with submicron resolution. In this work, we show identical shap...... objects by optical trapping when combined with a computer controlled motorized sample stage.......-complementary puzzle pieces being manipulated in a fluidic environment forming space-filling tessellations. By implementation of image analysis to detect the puzzle pieces, we developed a system capable of assembling a puzzle with no user interaction required. This allows for automatic gathering of sparsely scattered...

  6. Machine Learning for Optical Performance Monitoring from Directly Detected PDM-QAM Signals

    DEFF Research Database (Denmark)

    Wass, J.; Thrane, Jakob; Piels, Molly

    2016-01-01

    Supervised machine learning methods are applied and demonstrated experimentally for inband OSNR estimation and modulation format classification in optical communication systems. The proposed methods accurately evaluate coherent signals up to 64QAM using only intensity information....

  7. Dispersion management for two-level optically labeled signals in IP-over-WDM networks 4

    DEFF Research Database (Denmark)

    Chi, Nan; Carlsson, Birger; Holm-Nielsen, Pablo Villanueva;

    2002-01-01

    The transmission characteristics of a two-level optically labeled signal with ASK/DPSK modulation are investigated under varying dispersion management. A limitation of extinction ratio and the resilience of fiber span, compensation ratio, and power level are obtained...

  8. Training-based Channel Estimation for Signal Equalization and OPM in 16-QAM Optical Transmission Systems

    DEFF Research Database (Denmark)

    Pittalà, Fabio; Hauske, Fabian N.; Ye, Yabin;

    2012-01-01

    Efficient channel estimation for signal equalization and OPM based on short CAZAC sequences with QPSK and 8PSK constellation formats is demonstrated in a 224-Gb/s PDM 16-QAM optical linear transmission system....

  9. Converged wireline and wireless signal transport over optical fibre access links

    DEFF Research Database (Denmark)

    Tafur Monroy, Idelfonso; Prince, Kamau; Osadchiy, Alexey Vladimirovich

    2009-01-01

    This article reviews emerging trends in converged optical-wireless communication systems and outline the role that photonic technologies are playing in making the vision of a wireline-wireless converged signal transport network a reality.......This article reviews emerging trends in converged optical-wireless communication systems and outline the role that photonic technologies are playing in making the vision of a wireline-wireless converged signal transport network a reality....

  10. Analysis of Optical Signal Transmission Characteristics in AWG Multi/Demultiplexer with Electromagnetic Field Theory

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Based on the electromagnetic field theory, the optical signal transmission characteristics in input/output waveguides, slab waveguides and arrayed waveguides of the arrayed waveguide grating (AWG) multi/demultiplexer are analyzed. The relationship between the physical parameters such as geometry sizes and relative refractive index in AWG multi/demultiplexer and the optical signal transmission characteristics are discussed. This theoretical study can be used for optimizing the design and improving the performance of the AWG multi/demultiplexer.

  11. Parametric Optical Signal Processing in Silicon Waveguides with Reverse-biased p-i-n Junctions

    DEFF Research Database (Denmark)

    Peucheret, C.; Da Ros, Francesco; Vukovic, Dragana;

    2014-01-01

    The use of silicon-on-insulator waveguides with free carriers removal using a reverse-biased p-i-n junction for parametric optical signal processing is reviewed. High-efficiency wavelength conversion and phase-sensitive regeneration are reported.......The use of silicon-on-insulator waveguides with free carriers removal using a reverse-biased p-i-n junction for parametric optical signal processing is reviewed. High-efficiency wavelength conversion and phase-sensitive regeneration are reported....

  12. Photonic integrated circuits for the generation of coherent optical signals

    OpenAIRE

    Morrissey, Padraic E.

    2014-01-01

    The demand for optical bandwidth continues to increase year on year and is being driven primarily by entertainment services and video streaming to the home. Current photonic systems are coping with this demand by increasing data rates through faster modulation techniques, spectrally efficient transmission systems and by increasing the number of modulated optical channels per fibre strand. Such photonic systems are large and power hungry due to the high number of discrete components required i...

  13. Optical feedback effects on terahertz quantum cascade lasers: modelling and applications

    Science.gov (United States)

    Rakić, Aleksandar D.; Lim, Yah Leng; Taimre, Thomas; Agnew, Gary; Qi, Xiaoqiong; Bertling, Karl; Han, She; Wilson, Stephen J.; Kundu, Iman; Grier, Andrew; Ikonić, Zoran; Valavanis, Alexander; Demić, Aleksandar; Keeley, James; Li, Lianhe H.; Linfield, Edmund H.; Davies, A. Giles; Harrison, Paul; Ferguson, Blake; Walker, Graeme; Prow, Tarl; Indjin, Dragan; Soyer, H. Peter

    2016-11-01

    Terahertz (THz) quantum cascade lasers (QCLs) are compact sources of radiation in the 1-5 THz range with significant potential for applications in sensing and imaging. Laser feedback interferometry (LFI) with THz QCLs is a technique utilizing the sensitivity of the QCL to the radiation reflected back into the laser cavity from an external target. We will discuss modelling techniques and explore the applications of LFI in biological tissue imaging and will show that the confocal nature of the QCL in LFI systems, with their innate capacity for depth sectioning, makes them suitable for skin diagnostics with the well-known advantages of more conventional confocal microscopes. A demonstration of discrimination of neoplasia from healthy tissue using a THz, LFI-based system in the context of melanoma is presented using a transgenic mouse model.

  14. Soliton generation from a multi-frequency optical signal

    Energy Technology Data Exchange (ETDEWEB)

    Panoiu, N-C [Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY 10027 (United States); Mel' nikov, I V [Center for Research in Engineering and Applied Sciences, Morelos State Autonomous University, Av. Universidad 1001, 62210 Cuernavaca (Mexico); Mihalache, D [Department of Theoretical Physics, Institute of Atomic Physics, PO Box MG-6, Bucharest (Romania); Etrich, C [Institute of Solid State Theory and Theoretical Optics, Friedrich Schiller University Jena, Max-Wien-Platz 1, Jena, D-07743 (Germany); Lederer, F [Institute of Solid State Theory and Theoretical Optics, Friedrich Schiller University Jena, Max-Wien-Platz 1, Jena, D-07743 (Germany)

    2002-10-01

    We present a comprehensive analysis of the generation of optical solitons in a monomode optical fibre from a superposition of soliton-like optical pulses at different frequencies. It is demonstrated that the structure of the emerging optical field is highly dependent on the number of input channels, the inter-channel frequency separation, the time shift between the pulses belonging to adjacent channels, and the polarization of the pulses. Also, it is found that there exists a critical frequency separation above which wavelength-division multiplexing with solitons is feasible and that this critical frequency increases with the number of transmission channels. Moreover, for the case in which only two channels are considered, we analyse the propagation of the emerging two-soliton solutions in the presence of several perturbations important for optical networks: bandwidth-limited amplification, nonlinear amplification, and amplitude and phase modulation. Finally, the influence of the birefringence of the fibre on the structure of the emerging optical field is discussed. (review article)

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

    Science.gov (United States)

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

    2016-08-01

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

  16. Effects of quantum noise on the nonlinear dynamics of a semiconductor laser subject to two spectrally filtered, time-delayed optical feedbacks

    Science.gov (United States)

    Suelzer, Joseph S.; Prasad, Awadhesh; Ghosh, Rupamanjari; Vemuri, Gautam

    2016-07-01

    We report on a theoretical and computational investigation of the complex dynamics that arise in a semiconductor laser that is subject to two external, time-delayed, filtered optical feedbacks with special attention to the effect of quantum noise. In particular, we focus on the dynamics of the instantaneous optical frequency (wavelength) and its behavior for a wide range of feedback strengths and filter parameters. In the case of two intermediate filter bandwidths, the most significant results are that in the presence of noise, the feedback strengths required for the onset of chaos in a period doubling route are higher than in the absence of noise. We find that the inclusion of noise changes the dominant frequency of the wavelength oscillations, and that certain attractors do not survive in the presence of noise for a range of filter parameters. The results are interpreted by use of a combination of phase portraits, rf spectra, and first return maps.

  17. How the optical timing system,the longitudinal diagnostics and the associated feedback systems provide femtosecond stable operation at the FERMI free electron laser

    Institute of Scientific and Technical Information of China (English)

    Mario Ferianis; Enrico Allaria; Eugenio Ferrari; Giulio Gaio; Giuseppe Penco; Fabio Rossi; Marco Veronese

    2016-01-01

    FERMI, the seeded free electron laser(FEL) in operation in Italy, is providing the User Community with unique fully coherent radiation, in the wavelength range 100–4 nm. FERMI is the first FEL fully synchronized by means of optical fibers. The optical timing system ensures an ultra-stable phase reference to its distributed clients. Several femtosecond longitudinal diagnostics verify the achieved performance; the bunch length monitor(BLM) and the bunch arrival monitor(BAM) will be presented in this paper. Feedback systems play a crucial role to guarantee the needed longterm electron beam stability. A real-time infrastructure allows shot-to-shot communication between front-end computers and the servers. Orbit feedbacks are useful in machine tuning, whereas longitudinal feedbacks control electron energy,compression and arrival time. A flexible software framework allows a rapid implementation of heterogeneous multiinput–multi-output(MIMO) longitudinal loops simply by selecting the appropriate sensors and actuators.

  18. Experimental demonstration of change of dynamical properties of a passively mode-locked semiconductor laser subject to dual optical feedback by dual full delay-range tuning.

    Science.gov (United States)

    Nikiforov, O; Jaurigue, L; Drzewietzki, L; Lüdge, K; Breuer, S

    2016-06-27

    In this contribution we experimentally demonstrate the change and improvement of dynamical properties of a passively mode-locked semiconductor laser subject to optical feedback from two external cavities by coupling the feedback pulses back into the gain segment. Hereby, we tune the full delay-phase of the pulse-to-pulse period of both external cavities separately and demonstrate the change of the repetition rate, timing jitter, multi-pulse formation and side-band suppression for the first time for such a dual feedback configuration. In addition, we thereby confirm modeling predictions by achieving both a good qualitative and quantitative agreement of experimental and simulated results. Our findings suggest a path towards the realization of side-band free all-optical photonic oscillators based on mode-locked lasers.

  19. Semiconductor quantum dot amplifiers for optical signal processing

    DEFF Research Database (Denmark)

    Berg, Tommy Winther; Uskov, A. V.; Bischoff, Svend

    2001-01-01

    The dynamics of quantum dot semiconductor amplifiers are investigated theoretically with respect to the potential for ultrafast signal processing. The high-speed signal processing capacity of these devices is found to be limited by the wetting layer dynamics in case of electrical pumping, while...

  20. Semiconductor quantum dot amplifiers for optical signal processing

    DEFF Research Database (Denmark)

    Berg, Tommy Winther; Uskov, A. V.; Bischoff, Svend

    2001-01-01

    The dynamics of quantum dot semiconductor amplifiers are investigated theoretically with respect to the potential for ultrafast signal processing. The high-speed signal processing capacity of these devices is found to be limited by the wetting layer dynamics in case of electrical pumping, while...

  1. Phytochrome Signaling in Green Arabidopsis Seedlings: Impact Assessment of a Mutually Negative phyB-PIF Feedback Loop

    Institute of Scientific and Technical Information of China (English)

    Pablo Leivar; Elena Monte; Megan M. Cohn; Peter H. Quail

    2012-01-01

    The reversibly red (R)/far-red (FR)-Iight-responsive phytoch rome (phy) photosensory system initiates both the deetiolation process in dark-germinated seedlings upon first exposure to light,and the shade-avoidance process in fully deetiolated seedlings upon exposure to vegetational shade.The intracellular signaling pathway from the light-activated photoreceptor conformer (Pfr) to the transcriptional network that drives these responses involves direct,physical interaction of Pfr with a small subfamily of bHLH transcription factors,termed Phy-lnteracting Factors (PIFs),which induces rapid PIF proteolytic degradation.In addition,there is evidence of further complexity in light-grown seedlings,whereby phyB-PIF interaction reciprocally induces phyB degradation,in a mutually-negative,feedback-loop configuration.Here,to assess the relative contributions of these antagonistic activities to the net phenotypic readout in light-grown seedlings,we have examined the magnitude of the light- and simulated-shade-induced responses of a pentuple phyBpif1pif3pif4pif5 (phyBpifq) mutant and various multiple pif-mutant combinations.The data (1) reaffirm that phyB is the predominant,if not exclusive,photoreceptor imposing the inhibition of hypocotyl elongation in deetiolating seedlings in response to prolonged continuous R irradiation and (2) show that the PIF quartet (PIF1,PIF3,PIF4,and PIF5) retain and exert a dual capacity to modulate hypocotyl elongation under these conditions,by concomitantly promoting cell elongation through intrinsic transcriptional-regulatory activity,and reducing phyB-inhibitory capacity through feedback-loop-induced phyB degradation.In shade-exposed seedlings,immunoblot analysis shows that the shade-imposed reduction in Pfr levels induces increases in the abundance of PIF3,and mutant analysis indicates that PIF3 acts,in conjunction with PIF4 and PIF5,to promote the known shade-induced acceleration of hypocotyl elongation.Conversely,although the quadruple pifq

  2. Universal Michelson Gires-Tournois interferometer optical interleaver based on digital signal processing.

    Science.gov (United States)

    Zhang, Juan; Yang, Xiaowei

    2010-03-01

    Optical interleavers based on Michelson Gires-Tournois interferometer (MGTI) with arbitrary cascaded reflectors for symmetrical or asymmetrical periodic frequency response with arbitrary duty cycles are defined as universal MGTI optical interleaver (UMGTIOI). It can significantly enhance flexibility and applicability of optical networks. A novel and simple method based on digital signal processing is proposed for the design of UMGTIOI. Different kinds of design examples are given to confirm effectiveness of the method.

  3. Capacity of optical communications over a lossy bosonic channel with a receiver employing the most general coherent electro-optic feedback control

    Science.gov (United States)

    Chung, Hye Won; Guha, Saikat; Zheng, Lizhong

    2017-07-01

    We study the problem of designing optical receivers to discriminate between multiple coherent states using coherent processing receivers—i.e., one that uses arbitrary coherent feedback control and quantum-noise-limited direct detection—which was shown by Dolinar to achieve the minimum error probability in discriminating any two coherent states. We first derive and reinterpret Dolinar's binary-hypothesis minimum-probability-of-error receiver as the one that optimizes the information efficiency at each time instant, based on recursive Bayesian updates within the receiver. Using this viewpoint, we propose a natural generalization of Dolinar's receiver design to discriminate M coherent states, each of which could now be a codeword, i.e., a sequence of N coherent states, each drawn from a modulation alphabet. We analyze the channel capacity of the pure-loss optical channel with a general coherent-processing receiver in the low-photon number regime and compare it with the capacity achievable with direct detection and the Holevo limit (achieving the latter would require a quantum joint-detection receiver). We show compelling evidence that despite the optimal performance of Dolinar's receiver for the binary coherent-state hypothesis test (either in error probability or mutual information), the asymptotic communication rate achievable by such a coherent-processing receiver is only as good as direct detection. This suggests that in the infinitely long codeword limit, all potential benefits of coherent processing at the receiver can be obtained by designing a good code and direct detection, with no feedback within the receiver.

  4. Feedback Activation of Basic Fibroblast Growth Factor Signaling via the Wnt/β-Catenin Pathway in Skin Fibroblasts.

    Science.gov (United States)

    Wang, Xu; Zhu, Yuting; Sun, Congcong; Wang, Tao; Shen, Yingjie; Cai, Wanhui; Sun, Jia; Chi, Lisha; Wang, Haijun; Song, Na; Niu, Chao; Shen, Jiayi; Cong, Weitao; Zhu, Zhongxin; Xuan, Yuanhu; Li, Xiaokun; Jin, Litai

    2017-01-01

    Skin wound healing is a complex process requiring the coordinated behavior of many cell types, especially in the proliferation and migration of fibroblasts. Basic fibroblast growth factor (bFGF) is a member of the FGF family that promotes fibroblast migration, but the underlying molecular mechanism remains elusive. The present RNA sequencing study showed that the expression levels of several canonical Wnt pathway genes, including Wnt2b, Wnt3, Wnt11, T-cell factor 7 (TCF7), and Frizzled 8 (FZD8) were modified by bFGF stimulation in fibroblasts. Enzyme-linked immunosorbent assay (ELISA) analysis also showed that Wnt pathway was activated under bFGF treatment. Furthermore, treatment of fibroblasts with lithium chloride or IWR-1, an inducer and inhibitor of the Wnt signaling pathway, respectively, promoted and inhibited cell migration. Also, levels of cytosolic glycogen synthase kinase 3 beta phosphorylated at serine(9) (pGSK3β Ser(9)) and nuclear β-catenin were increased upon exposure to bFGF. Molecular and biochemical assays indicated that phosphoinositide 3-kinase (PI3K) signaling activated the GSK3β/β-catenin/Wnt signaling pathway via activation of c-Jun N-terminal kinase (JNK), suggesting that PI3K and JNK act at the upstream of β-catenin. In contrast, knock-down of β-catenin delayed fibroblast cell migration even under bFGF stimulation. RNA sequencing analysis of β-catenin knock-down fibroblasts demonstrated that β-catenin positively regulated the transcription of bFGF and FGF21. Moreover, FGF21 treatment activated AKT and JNK, and accelerated fibroblast migration to a similar extent as bFGF does. In addition, ELISA analysis demonstrated that both of bFGF and FGF21 were auto secretion factor and be regulated by Wnt pathway stimulators. Taken together, our analyses define a feedback regulatory loop between bFGF (FGF21) and Wnt signaling acting through β-catenin in skin fibroblasts.

  5. Connectivity Reveals Sources of Predictive Coding Signals in Early Visual Cortex During Processing of Visual Optic Flow.

    Science.gov (United States)

    Schindler, Andreas; Bartels, Andreas

    2016-05-24

    Superimposed on the visual feed-forward pathway, feedback connections convey higher level information to cortical areas lower in the hierarchy. A prominent framework for these connections is the theory of predictive coding where high-level areas send stimulus interpretations to lower level areas that compare them with sensory input. Along these lines, a growing body of neuroimaging studies shows that predictable stimuli lead to reduced blood oxygen level-dependent (BOLD) responses compared with matched nonpredictable counterparts, especially in early visual cortex (EVC) including areas V1-V3. The sources of these modulatory feedback signals are largely unknown. Here, we re-examined the robust finding of relative BOLD suppression in EVC evident during processing of coherent compared with random motion. Using functional connectivity analysis, we show an optic flow-dependent increase of functional connectivity between BOLD suppressed EVC and a network of visual motion areas including MST, V3A, V6, the cingulate sulcus visual area (CSv), and precuneus (Pc). Connectivity decreased between EVC and 2 areas known to encode heading direction: entorhinal cortex (EC) and retrosplenial cortex (RSC). Our results provide first evidence that BOLD suppression in EVC for predictable stimuli is indeed mediated by specific high-level areas, in accord with the theory of predictive coding.

  6. Optically pumped distributed feedback dye lasing with slide-coated TiO₂ inverse-opal slab as Bragg reflector.

    Science.gov (United States)

    Han, Sung Gu; Lim, Jongchul; Shin, Jinsub; Lee, Sung-Min; Park, Taiho; Yoon, Jongseung; Woo, Kyoungja; Lee, Hyunjung; Lee, Wonmok

    2014-08-15

    We demonstrate an optical amplification of organic dye within a TiO2 inverse-opal (IO) distributed feedback (DFB) reflector prepared by a slide-coating method. Highly reflective TiO2 IO film was fabricated by slide coating the binary aqueous dispersions of polystyrene microspheres and charge-stabilized TiO2 nanoparticles on a glass slide and subsequently removing the polymer-opal template. TiO2 IO film was infiltrated, in turn, with the solutions of DCM, a fluorescent dye in various solvents with different indices of refraction. Optical pumping by frequency-doubled Nd:YAG laser resulted in amplified spontaneous emission in each dye solution. In accordance with the semi-empirical simulation by the FDTD method, DCM in ethanol showed the best emission/stopband matching for the TiO2 IO film used in this study. Therefore, photo excitation of a DCM/ethanol cavity showed a single-mode DFB lasing at 640 nm wavelength at moderate pump energy.

  7. Remote sensing of plant trait responses to field-based plant-soil feedback using UAV-based optical sensors

    Science.gov (United States)

    van der Meij, Bob; Kooistra, Lammert; Suomalainen, Juha; Barel, Janna M.; De Deyn, Gerlinde B.

    2017-02-01

    Plant responses to biotic and abiotic legacies left in soil by preceding plants is known as plant-soil feedback (PSF). PSF is an important mechanism to explain plant community dynamics and plant performance in natural and agricultural systems. However, most PSF studies are short-term and small-scale due to practical constraints for field-scale quantification of PSF effects, yet field experiments are warranted to assess actual PSF effects under less controlled conditions. Here we used unmanned aerial vehicle (UAV)-based optical sensors to test whether PSF effects on plant traits can be quantified remotely. We established a randomized agro-ecological field experiment in which six different cover crop species and species combinations from three different plant families (Poaceae, Fabaceae, Brassicaceae) were grown. The feedback effects on plant traits were tested in oat (Avena sativa) by quantifying the cover crop legacy effects on key plant traits: height, fresh biomass, nitrogen content, and leaf chlorophyll content. Prior to destructive sampling, hyperspectral data were acquired and used for calibration and independent validation of regression models to retrieve plant traits from optical data. Subsequently, for each trait the model with highest precision and accuracy was selected. We used the hyperspectral analyses to predict the directly measured plant height (RMSE = 5.12 cm, R2 = 0.79), chlorophyll content (RMSE = 0.11 g m-2, R2 = 0.80), N-content (RMSE = 1.94 g m-2, R2 = 0.68), and fresh biomass (RMSE = 0.72 kg m-2, R2 = 0.56). Overall the PSF effects of the different cover crop treatments based on the remote sensing data matched the results based on in situ measurements. The average oat canopy was tallest and its leaf chlorophyll content highest in response to legacy of Vicia sativa monocultures (100 cm, 0.95 g m-2, respectively) and in mixture with Raphanus sativus (100 cm, 1.09 g m-2, respectively), while the lowest values (76 cm, 0.41 g m-2, respectively

  8. Amplitude regeneration of RZ-DPSK signals in single-pump fiber-optic parametric amplifiers

    DEFF Research Database (Denmark)

    Peucheret, Christophe; Lorenzen, Michael Rodas; Seoane, Jorge

    2009-01-01

    to demonstrate amplitude regeneration of a distorted RZ-DPSK signal in a gain-saturated FOPA. An optical signal-to-noise ratio penalty of 3.5 dB after amplitude distortion is shown to be reduced to 0.2 dB after the FOPA, thus clearly demonstrating the regenerative nature of saturated FOPAs for RZ-DPSK modulation....

  9. Stimulus-Evoked Intrinsic Optical Signals in the Retina: Pharmacologic Dissection Reveals Outer Retinal Origins

    NARCIS (Netherlands)

    Schallek, Jesse; Kardon, Randy; Kwon, Young; Abramoff, Michael; Soliz, Peter; Ts’o, Daniel

    2009-01-01

    purpose. To elucidate the anatomic origins of stimulus-evoked intrinsic optical signals in the mammalian retina by using selective pharmacologic blockade of specific retinal layers. methods. Four adult cats were used to investigate the stimulus-evoked intrinsic signals. The retinas were visually s

  10. Integration of Optically Generated Impulse Radio UWB Signals into Baseband WDM-PON

    DEFF Research Database (Denmark)

    Pham, Tien Thang; Yu, Xianbin; Dittmann, Lars

    2011-01-01

    We propose a compact integration system to simultaneously provide wireline and wireless (baseband and ultra-wide band (UWB)) services to end-users in a WDM-PON. A 1-Gbps UWB signal is optically generated and shares the same wavelength with the baseband signal. Error-free performance was achieved ...

  11. Experimental investigation of chirp properties induced by signal amplification in quantum-dot semiconductor optical amplifiers.

    Science.gov (United States)

    Matsuura, Motoharu; Ohta, Hiroaki; Seki, Ryota

    2015-03-15

    We experimentally show the dynamic frequency chirp properties induced by signal amplification in a quantum-dot semiconductor optical amplifier (QD-SOA) for the first time. We also compare the red and blue chirp peak values and temporal chirp changes while changing the gain and injected signal powers of the QD-SOA with those of a common SOA.

  12. Partial Discharge Optical Pulse Signal Characteristics for Corona Defect in Oil Immersed Transformer

    Directory of Open Access Journals (Sweden)

    Jiabin Zhou

    2013-03-01

    Full Text Available Using fluorescent fiber sensor in transformer PD detection is a new method, based on the experimental platform for corona PD defect, the study has been carried out in order to show the typical corona PD defect optical pulse signal characteristics, PD single pulse waveform and pulses under industrial frequency cycle were acquired. The test results show that the optical method by using fluorescent fiber is effective in PD detection and corona PD optical pulse signals can accurately reflect the characteristics for this kind defect.

  13. Ultrafast optical signal processing using semiconductor quantum dot amplifiers

    DEFF Research Database (Denmark)

    Berg, Tommy Winther; Mørk, Jesper

    2002-01-01

    The linear and nonlinear properties of quantum dot amplifiers are discussed on the basis of an extensive theoretical model. These devices show great potential for linear amplification as well as ultrafast signal processing.......The linear and nonlinear properties of quantum dot amplifiers are discussed on the basis of an extensive theoretical model. These devices show great potential for linear amplification as well as ultrafast signal processing....

  14. Multifrequency Magneto-optic Bragg Diffraction and Radio Frequency Signal Parallel Processing

    Institute of Scientific and Technical Information of China (English)

    SHANG Dan; WU Bao-jian; QIU Kun

    2008-01-01

    Magneto-optic(MO) coupling of guided optical waves with microwave magnetostatic waves(MSWs) simultaneously excited by multiple radio frequency(RF) signals can lead to multifrequency diffraction effects and then parallel processing of RF signals can be realized by using of the characteristics that diffraction efficiencies(Des) are approximately in direct proportion to RF signals intensities and diffraction angles are related to frequencies of the corresponding RF signals within linear MO interaction region. In this paper, studied is the multifrequency MO Bragg diffraction in first-order MO interaction approximation, and obtained was the approximate analytical expression for principle diffraction efficiency(PDE). Also, put forward was a parallel imaging method of relative intensity of RF signals based on single-frequency diffraction. By calculation and analysis, it is shown that the relative error is not more than 0.3 dB for the case of three RF signals within the frequency space of 60 MHz.

  15. Low-frequency analog signal distribution on digital photonic networks by optical delta-sigma modulation

    Science.gov (United States)

    Kanno, Atsushi; Kawanishi, Tetsuya

    2013-12-01

    We propose a delta-sigma modulation scheme for low- and medium-frequency signal transmission in a digital photonic network system. A 10-Gb/s-class optical transceiver with a delta-sigma modulator utilized as a high-speed analog-to-digital converter (ADC) provides a binary optical signal. On the signal reception side, a low-cost and slow-speed photonic receiver directly converts the binary signal into an analog signal at frequencies from several hundreds of kilohertz several tens of megahertz. Further, by using a clock and data recovery circuit at the receiver to reduce jitters, the single-sideband phase noise of the generated signals can be significantly reduced.

  16. Photoacoustic correlation signal-to-noise ratio enhancement by coherent averaging and optical waveform optimization.

    Science.gov (United States)

    Telenkov, Sergey A; Alwi, Rudolf; Mandelis, Andreas

    2013-10-01

    Photoacoustic (PA) imaging of biological tissues using laser diodes instead of conventional Q-switched pulsed systems provides an attractive alternative for biomedical applications. However, the relatively low energy of laser diodes operating in the pulsed regime, results in generation of very weak acoustic waves, and low signal-to-noise ratio (SNR) of the detected signals. This problem can be addressed if optical excitation is modulated using custom waveforms and correlation processing is employed to increase SNR through signal compression. This work investigates the effect of the parameters of the modulation waveform on the resulting correlation signal and offers a practical means for optimizing PA signal detection. The advantage of coherent signal averaging is demonstrated using theoretical analysis and a numerical model of PA generation. It was shown that an additional 5-10 dB of SNR can be gained through waveform engineering by adjusting the parameters and profile of optical modulation waveforms.

  17. All-optical wavelength conversion and signal regeneration using an electroabsorption modulator

    DEFF Research Database (Denmark)

    Højfeldt, Sune; Bischoff, Svend; Mørk, Jesper

    2000-01-01

    All-optical wavelength conversion and signal regeneration based on cross-absorption modulation in an InGaAsP quantum well electroabsorption modulator (EAM) is studied at different bit rates. We present theoretical results showing wavelength conversion efficiency in agreement with existing...... experimental results, and the signal regeneration capability of the device is investigated. In particular, we demonstrate the dependence of the extinction ratio of both the converted signal and the control signal on the device length and on the power level of the control signal. We also show how the sweep...

  18. Mapping the spatiotemporal dynamics of calcium signaling in cellular neural networks using optical flow

    CERN Document Server

    Buibas, Marius; Nizar, Krystal; Silva, Gabriel A

    2009-01-01

    An optical flow gradient algorithm was applied to spontaneously forming networks of neurons and glia in culture imaged by fluorescence optical microscopy in order to map functional calcium signaling with single pixel resolution. Optical flow estimates the direction and speed of motion of objects in an image between subsequent frames in a recorded digital sequence of images (i.e. a movie). Computed vector field outputs by the algorithm were able to track the spatiotemporal dynamics of calcium signaling patterns. We begin by briefly reviewing the mathematics of the optical flow algorithm, describe how to solve for the displacement vectors, and how to measure their reliability. We then compare computed flow vectors with manually estimated vectors for the progression of a calcium signal recorded from representative astrocyte cultures. Finally, we applied the algorithm to preparations of primary astrocytes and hippocampal neurons and to the rMC-1 Muller glial cell line in order to illustrate the capability of the ...

  19. Real-time reception of multi-gigabit coherent optical OFDM signals.

    Science.gov (United States)

    Yang, Qi; Chen, Simin; Ma, Yiran; Shieh, William

    2009-05-11

    Coherent Optical OFDM (CO-OFDM) has been demonstrated for delivering superior performance in spectral efficiency, receiver sensitivity, and polarization-dispersion resilience. Fueled by the rapid advancement in semiconductor technology, high-speed field-programmable gate arrays (FPGA) and analogue-to-digital-converters/digital-to-analogue converters (ADC/DACs) have been increasingly adopted for digital signal processing in optical communications. In this paper, we report the first FPGA-based real-time implementation of coherent optical OFDM (CO-OFDM) receiver with a transmission rate up to 3.1 Gb/s. Several basic aspects of CO-OFDM signal processing are described in detail, and the BER sensitivity performance are evaluated in real-time. To the best of our knowledge, we have achieved the record real-time reception date rate for a single-input single-output (SISO) coherent OFDM signal, in either RF domain or optical domain.

  20. Self-motion Perception from Optic Flow and Rotation Signals

    NARCIS (Netherlands)

    J.A. Beintema (Jaap)

    2000-01-01

    textabstractThe value of optic flow for retrieving movement direction was recognised already two centuries ago by astronomers, searching the sky for meteorite showers. The point from which the shower appeared to emanate they termed the radiant, knowing it indicated the direction along which the mete

  1. Self-motion Perception from Optic Flow and Rotation Signals

    NARCIS (Netherlands)

    J.A. Beintema (Jaap)

    2000-01-01

    textabstractThe value of optic flow for retrieving movement direction was recognised already two centuries ago by astronomers, searching the sky for meteorite showers. The point from which the shower appeared to emanate they termed the radiant, knowing it indicated the direction along which the mete

  2. An analog modulation and demodulation method employing LVDT signal conditioner for fiber-optic interferometric sensors

    Science.gov (United States)

    Zhou, Kejiang; Rao, Qi; Zhang, Minjie; Hu, Keke; Ruan, Yefeng

    2017-09-01

    An analog method to modulate and demodulate fiber-optic interferometric sensors employing a linear variable differential transformer signal conditioner to generate sine modulation wave and demodulate phase-modulated signal from the photodetector’s output is presented in this letter. No external lock-in amplifiers or digital components are used in this design. All the necessary components for signal processing are integrated in a single analog electronic microchip AD698, which reduces the system’s complexity significantly. After implementation on an interferometric fiber-optic gyroscope as an example, this method demonstrates a bias stability of 0.063 deg h-1 (i.e. 0.220 µrad).

  3. Influence of Injection Molding Process on the Local Fluctuations of Magneto-Optical Signals

    Science.gov (United States)

    Umezawa, Tomokazu; Horiguchi, Toru; Tomie, Takashi

    2001-01-01

    The local fluctuations of magneto-optical (MO) signals were investigated in the vicinity of the preformat pits of polycarbonate (PC) substrates fabricated under different injection molding conditions and also using stampers which had different shapes of grooves and preformat pits. A strong correlation was observed between the substrate birefringence and the fluctuation of the MO signal. The rate-of-change of the fluctuations, as the phase shift of the optical head was varied, was attributed to the shapes of preformat pits and grooves. The fluctuation of the MO signal could be controlled by varying the injection molding conditions and the shapes of preformat pits and grooves.

  4. Alignment signal extraction of the optically degenerate RSE interferometer using the wave front sensing technique

    Science.gov (United States)

    Sato, S.; Kawamura, S.

    2008-07-01

    The alignment sensing and control scheme of the resonant sideband extraction interferometer is still an unsettled issue for the next-generation gravitational wave antennas. The issue is that it is difficult to extract separate error signals for all 12 angular degrees of freedom, which is mainly arising from the complexity of the optical system and cavity 'degeneracy'. We have suggested a new sensing scheme giving reasonably separated signals which is fully compatible with the length sensing scheme. The key of this idea is to resolve the 'degeneracy' of the optical cavities. By choosing an appropriate Gouy phase for the degenerate cavities, alignment error signals with much less admixtures can be extracted.

  5. Analog CMOS circuit design and characterization for optical coherence tomography signal processing.

    Science.gov (United States)

    Kariya, Rajesh; Mathine, David L; Barton, Jennifer K

    2004-12-01

    We have developed a custom analog CMOS circuit to perform the signal processing for an optical coherence tomography imaging system. The circuit is realized in a 1.5 microm low-noise analog CMOS technology. The circuitry extracts the Doppler frequency from the signal and electrically mixes this with the original signal to provide a filtered A-scan. The circuitry was used to produce a two-dimensional image of an onion.

  6. Highly stretchable electroluminescent skin for optical signaling and tactile sensing.

    Science.gov (United States)

    Larson, C; Peele, B; Li, S; Robinson, S; Totaro, M; Beccai, L; Mazzolai, B; Shepherd, R

    2016-03-04

    Cephalopods such as octopuses have a combination of a stretchable skin and color-tuning organs to control both posture and color for visual communication and disguise. We present an electroluminescent material that is capable of large uniaxial stretching and surface area changes while actively emitting light. Layers of transparent hydrogel electrodes sandwich a ZnS phosphor-doped dielectric elastomer layer, creating thin rubber sheets that change illuminance and capacitance under deformation. Arrays of individually controllable pixels in thin rubber sheets were fabricated using replica molding and were subjected to stretching, folding, and rolling to demonstrate their use as stretchable displays. These sheets were then integrated into the skin of a soft robot, providing it with dynamic coloration and sensory feedback from external and internal stimuli.

  7. Coherent Detection of Optical Quadrature Phase-Shift Keying Signals With Carrier Phase Estimation

    Science.gov (United States)

    Ly-Gagnon, Dany-Sebastien; Tsukamoto, Satoshi; Katoh, Kazuhiro; Kikuchi, Kazuro

    2006-01-01

    This paper describes a coherent optical receiver for demodulating optical quadrature phase-shift keying (QPSK) signals. At the receiver, a phase-diversity homodyne detection scheme is employed without locking the phase of the local oscillator (LO). To handle the carrier phase drift, the carrier phase is estimated with digital signal processing (DSP) on the homodyne-detected signal. Such a scheme presents the following major advantages over the conventional optical differential detection. First, its bit error rate (BER) performance is better than that of differential detection. This higher sensitivity can extend the reach of unrepeated transmission systems and reduce crosstalk between multiwavelength channels. Second, the optoelectronic conversion process is linear, so that the whole optical signal information can be postprocessed in the electrical domain. Third, this scheme is applicable to multilevel modulation formats such as M-array PSK and quadrature amplitude modulation (QAM). The performance of the receiver is evaluated through various simulations and experiments. As a result, an unrepeated transmission over 210 km with a 20-Gb/s optical QPSK signal is achieved. Moreover, in wavelength-division multiplexing (WDM) environment, coherent detection allows the filtering of a desired wavelength channel to reside entirely in the electrical domain, taking advantage of the sharp cutoff characteristics of electrical filters. The experiments show the feasibility to transmit polarization-multiplexed 40-Gb/s QPSK signals over 200 km with channel spacing of 16 GHz, leading to a spectral efficiency as high as 2.5 b/s/Hz.

  8. High speed all optical Nyquist signal generation and full-band coherent detection.

    Science.gov (United States)

    Zhang, Junwen; Yu, Jianjun; Fang, Yuan; Chi, Nan

    2014-08-21

    Spectrum efficient data transmission is of key interest for high capacity optical communication systems considering the limited available bandwidth. Transmission of the high speed signal with higher-order modulation formats within the Nyquist bandwidth using coherent detection brings attractive performance advantages. However, high speed Nyquist signal generation with high order modulation formats is challenging. Electrical Nyquist pulse generation is restricted by the limited sampling rate and processor capacities of digital-to-analog convertor devices, while the optical Nyquist signals can provide a much higher symbol rate using time domain multiplexing method. However, most optical Nyquist signals are based on direct detection with simple modulation formats. Here we report the first experimental demonstration of high speed all optical Nyquist signal generation based on Sinc-shaped pulse generation and time-division multiplexing with high level modulation format and full-band coherent detection. Our experiments demonstrate a highly flexible and compatible all optical high speed Nyquist signal generation and detection scheme for future fiber communication systems.

  9. Optical techniques for signal distribution and control in advanced radar and communication systems

    Science.gov (United States)

    Forrest, J. R.

    1985-03-01

    It is concluded that optical techniques offer some advantages for signal distribution and control in advanced radar and communication systems. They are clearly ideal for transporting microwave signals over considerable distances, as in remote positioning of radar receivers, provided high dynamic range is not required and an enclosed transmission path is essential. They are an elegant means of distributing low level r.f. or i.f. signals around an active phased array where these signals are of relatively constant amplitude (as in mixer local oscillator applications). However, there is currently a rather restrictive limit on the size of distribution network possible. Optical techniques are obviously suitable for distributing digital control signals to phased array modules and confer considerable immunity to interference. They are less suitable for high dynamic range signals, such as the received radar returns, either at r.f. or when downcovered to i.f. Future developments in coherent optics or in fast optical A/D technology could, however, influence this conclusion. Currently, the optimum applications for optical techniques appear to be i.f. beamformers for multibeam communication satellite systems and in calibration/monitoring systems for phased arrays.

  10. Canonical Wnt/β-catenin signalling is essential for optic cup formation.

    Directory of Open Access Journals (Sweden)

    Anna-Carin Hägglund

    Full Text Available A multitude of signalling pathways are involved in the process of forming an eye. Here we demonstrate that β-catenin is essential for eye development as inactivation of β-catenin prior to cellular specification in the optic vesicle caused anophthalmia in mice. By achieving this early and tissue-specific β-catenin inactivation we find that retinal pigment epithelium (RPE commitment was blocked and eye development was arrested prior to optic cup formation due to a loss of canonical Wnt signalling in the dorsal optic vesicle. Thus, these results show that Wnt/β-catenin signalling is required earlier and play a more central role in eye development than previous studies have indicated. In our genetic model system a few RPE cells could escape β-catenin inactivation leading to the formation of a small optic rudiment. The optic rudiment contained several neural retinal cell classes surrounded by an RPE. Unlike the RPE cells, the neural retinal cells could be β-catenin-negative revealing that differentiation of the neural retinal cell classes is β-catenin-independent. Moreover, although dorsoventral patterning is initiated in the mutant optic vesicle, the neural retinal cells in the optic rudiment displayed almost exclusively ventral identity. Thus, β-catenin is required for optic cup formation, commitment to RPE cells and maintenance of dorsal identity of the retina.

  11. All-Optical Signal processing using Highly Nonlinear Photonic Crystal Fiber

    DEFF Research Database (Denmark)

    Andersen, Peter Andreas

    2006-01-01

    The use of HNL-PCF in optical communication systems has been investigated in this thesis. The investigation has been done with respect to the future of telecommunications in an all-optical system. The PCFs used have all been used for all-optical signal processing as part of an optical component...... and the possibility of large differences between the refractive indices of the core and the cladding by using air-holes, makes PCFs suited for custom made components. By testing a HNL-PCF as a medium for supercontinuum generation at various dispersion values and at the same time using that supercontinuum...... of modulation format of the signal. The modulation format is also dependent on transmission in the optical system and dependent on the pulse source used to generate the supercontinuum. It is believed that by satisfying strict demands on the pulse sources and the fiber design, could the use of a supercontinuum...

  12. Research and implementation of the burst-mode optical signal bit-error test

    Science.gov (United States)

    Huang, Qiu-yuan; Ma, Chao; Shi, Wei; Chen, Wei

    2009-08-01

    On the basis of the characteristic of TDMA uplink optical signal of PON system, this article puts forward a method of high-speed optical burst bit-error rate testing based on FPGA. The article proposes a new method of generating the burst signal pattern include user-defined pattern and pseudo-random pattern, realizes the slip synchronization, self-synchronization of error detection using data decomposition technique and the traditional irrigation code synchronization technology, completes high-speed burst signal clock synchronization using the rapid synchronization technology of phase-locked loop delay in the external circuit and finishes the bit-error rate test of high-speed burst optical signal.

  13. FRET imaging and statistical signal processing reveal positive and negative feedback loops regulating the morphology of randomly migrating HT-1080 cells.

    Science.gov (United States)

    Kunida, Katsuyuki; Matsuda, Michiyuki; Aoki, Kazuhiro

    2012-05-15

    Cell migration plays an important role in many physiological processes. Rho GTPases (Rac1, Cdc42, RhoA) and phosphatidylinositols have been extensively studied in directional cell migration. However, it remains unclear how Rho GTPases and phosphatidylinositols regulate random cell migration in space and time. We have attempted to address this issue using fluorescence resonance energy transfer (FRET) imaging and statistical signal processing. First, we acquired time-lapse images of random migration of HT-1080 fibrosarcoma cells expressing FRET biosensors of Rho GTPases and phosphatidyl inositols. We developed an image-processing algorithm to extract FRET values and velocities at the leading edge of migrating cells. Auto- and cross-correlation analysis suggested the involvement of feedback regulations among Rac1, phosphatidyl inositols and membrane protrusions. To verify the feedback regulations, we employed an acute inhibition of the signaling pathway with pharmaceutical inhibitors. The inhibition of actin polymerization decreased Rac1 activity, indicating the presence of positive feedback from actin polymerization to Rac1. Furthermore, treatment with PI3-kinase inhibitor induced an adaptation of Rac1 activity, i.e. a transient reduction of Rac1 activity followed by recovery to the basal level. In silico modeling that reproduced the adaptation predicted the existence of a negative feedback loop from Rac1 to actin polymerization. Finally, we identified MLCK as the probable controlling factor in the negative feedback. These findings quantitatively demonstrate positive and negative feedback loops that involve actin, Rac1 and MLCK, and account for the ordered patterns of membrane dynamics observed in randomly migrating cells.

  14. Optical fibre multi-parameter sensing with secure cloud based signal capture and processing

    Science.gov (United States)

    Newe, Thomas; O'Connell, Eoin; Meere, Damien; Yuan, Hongwei; Leen, Gabriel; O'Keeffe, Sinead; Lewis, Elfed

    2016-05-01

    Recent advancements in cloud computing technologies in the context of optical and optical fibre based systems are reported. The proliferation of real time and multi-channel based sensor systems represents significant growth in data volume. This coupled with a growing need for security presents many challenges and presents a huge opportunity for an evolutionary step in the widespread application of these sensing technologies. A tiered infrastructural system approach is adopted that is designed to facilitate the delivery of Optical Fibre-based "SENsing as a Service- SENaaS". Within this infrastructure, novel optical sensing platforms, deployed within different environments, are interfaced with a Cloud-based backbone infrastructure which facilitates the secure collection, storage and analysis of real-time data. Feedback systems, which harness this data to affect a change within the monitored location/environment/condition, are also discussed. The cloud based system presented here can also be used with chemical and physical sensors that require real-time data analysis, processing and feedback.

  15. Photonic Devices and Systems for Optical Signal Processing

    Science.gov (United States)

    1993-08-01

    68 Figure 8.3: Spectra for the Gain Guided Arrayed Laser ...................................................................... 69 Figure 8.4...The GGA laser is extinguished in the direction F for reverse bias voltages Vf larger than -2.5 volts. Applying reverse 68 IN MA ID mAV ,& -05 WAVELENGTH...beam etching of GaAs," J. Vac. Sci. Technol., Vol. B8. No. 5, pp. 1075-1079, September/October 1990. 18. Marcuse , D., Theory of Dielectric Optical

  16. Joint digital signal processing for superchannel coherent optical communication systems.

    Science.gov (United States)

    Liu, Cheng; Pan, Jie; Detwiler, Thomas; Stark, Andrew; Hsueh, Yu-Ting; Chang, Gee-Kung; Ralph, Stephen E

    2013-04-01

    Ultra-high-speed optical communication systems which can support ≥ 1Tb/s per channel transmission will soon be required to meet the increasing capacity demand. However, 1Tb/s over a single carrier requires either or both a high-level modulation format (i.e. 1024QAM) and a high baud rate. Alternatively, grouping a number of tightly spaced "sub-carriers" to form a terabit superchannel increases channel capacity while minimizing the need for high-level modulation formats and high baud rate, which may allow existing formats, baud rate and components to be exploited. In ideal Nyquist-WDM superchannel systems, optical subcarriers with rectangular spectra are tightly packed at a channel spacing equal to the baud rate, thus achieving the Nyquist bandwidth limit. However, in practical Nyquist-WDM systems, precise electrical or optical control of channel spectra is required to avoid strong inter-channel interference (ICI). Here, we propose and demonstrate a new "super receiver" architecture for practical Nyquist-WDM systems, which jointly detects and demodulates multiple channels simultaneously and mitigates the penalties associated with the limitations of generating ideal Nyquist-WDM spectra. Our receiver-side solution relaxes the filter requirements imposed on the transmitter. Two joint DSP algorithms are developed for linear ICI cancellation and joint carrier-phase recovery. Improved system performance is observed with both experimental and simulation data. Performance analysis under different system configurations is conducted to demonstrate the feasibility and robustness of the proposed joint DSP algorithms.

  17. Providing haptic feedback in robot-assisted minimally invasive surgery: a direct optical force-sensing solution for haptic rendering of deformable bodies.

    Science.gov (United States)

    Ehrampoosh, Shervin; Dave, Mohit; Kia, Michael A; Rablau, Corneliu; Zadeh, Mehrdad H

    2013-01-01

    This paper presents an enhanced haptic-enabled master-slave teleoperation system which can be used to provide force feedback to surgeons in minimally invasive surgery (MIS). One of the research goals was to develop a combined-control architecture framework that included both direct force reflection (DFR) and position-error-based (PEB) control strategies. To achieve this goal, it was essential to measure accurately the direct contact forces between deformable bodies and a robotic tool tip. To measure the forces at a surgical tool tip and enhance the performance of the teleoperation system, an optical force sensor was designed, prototyped, and added to a robot manipulator. The enhanced teleoperation architecture was formulated by developing mathematical models for the optical force sensor, the extended slave robot manipulator, and the combined-control strategy. Human factor studies were also conducted to (a) examine experimentally the performance of the enhanced teleoperation system with the optical force sensor, and (b) study human haptic perception during the identification of remote object deformability. The first experiment was carried out to discriminate deformability of objects when human subjects were in direct contact with deformable objects by means of a laparoscopic tool. The control parameters were then tuned based on the results of this experiment using a gain-scheduling method. The second experiment was conducted to study the effectiveness of the force feedback provided through the enhanced teleoperation system. The results show that the force feedback increased the ability of subjects to correctly identify materials of different deformable types. In addition, the virtual force feedback provided by the teleoperation system comes close to the real force feedback experienced in direct MIS. The experimental results provide design guidelines for choosing and validating the control architecture and the optical force sensor.

  18. A method to remove residual signals in fibre optic luminescence dosimeters.

    Science.gov (United States)

    Lee, J J; Liu, P Z Y; McKenzie, D R; Suchowerska, N

    2013-03-07

    Whenever a fibre optic is used to convey a light signal through a radiation field, it is likely that an unwanted background signal will arise from Cerenkov or fluorescent light which will contaminate the signal. In luminescence dosimetry of high energy beams, when a fibre optic is used to convey the signal from the radiation field to the detector, Cerenkov light is the dominant contributor to the background signal and must be corrected for. In this work, a novel method is demonstrated to separate the signal from the unwanted background. A remotely operated shutter is used to block the signal, allowing the residual background in the fibre optic to be quantified. This background is subtracted from the total measurement acquired in a subsequent irradiation, enabling the luminescence signal to be extracted. Two types of shutter mechanism are considered: an electro-mechanical device to intercept the light path and an LCD device to block the light by cross-polarization. Both shutters were characterized and incorporated into a fibre optic dosimetry system used to measure the radiation dose produced by external beam radiation linear accelerators. The dosimeter using each of the shutters in turn was exposed to a 6 MV photon beam to determine their performance, including the measurement of field size dependent output factors. The mechanical shutter determined the output factors to within 0.29% of those measured with an ionization chamber, whereas the LCD shutter gave results that deviated by up to 2.4%. The switching precision of both shutters was good with standard deviations of less than 0.25% and both were able to completely block the light signal when closed. The use of shutters could therefore be applied to any fibre optic based system to quantify and remove a reproducible background arising from any source including ambient, fluorescent and Cerenkov light.

  19. TLR4 signaling promotes a COX-2/PGE2/STAT3 positive feedback loop in hepatocellular carcinoma (HCC) cells

    Science.gov (United States)

    Lin, Ang; Wang, Guan; Zhao, Huajun; Zhang, Yuyi; Han, Qiuju; Zhang, Cai; Tian, Zhigang; Zhang, Jian

    2016-01-01

    ABSTRACT Toll-like receptors (TLRs) can be expressed by tumor cells, and each TLR exhibits different biological functions. Evidences showed the activation of some certain TLRs could promote tumor progression. One of which TLR4 has been found to promote hepatocellular carcinoma (HCC) cells proliferation, but the detailed mechanism is still unknown. In the present study, we verified that TLR4 was functionally expressed on HCC cells, and TLR4 agonist lipopolysaccharide (LPS) could stimulate the proliferation and clone formation of HCC cells. Most importantly, we found a COX-2/PGE2/STAT3 positive feedback loop exists in HCC cells, which could be provoked by TLR4 activation. Consistently, the expression of TLR4, COX-2 and p-STAT3Y705 was positively correlated with each other in liver tumor tissues from patients with primary HCC. Further investigation demonstrated this loop played a dominant role in TLR4-induced HCC cell proliferation and multidrug resistance (MDR) to chemotherapy. Inhibition of TLR4 or COX-2/PGE2/STAT3 loop would attenuate LPS-induced inflammation and proliferation of HCC cells, and enhance the sensitivity of HCC cells to chemotherapeutics in vitro. By using a primary HCC model, we observed COX-2/PGE2/STAT3 loop was significantly blocked in TLR4−/− mice compared to wild type mice, and there was no obvious tumorgenesis sign in TLR4−/− mice. Therefore, these findings provided the precise molecular mechanism of TLR4 signaling pathway involved in HCC progress, and suggested that TLR4 may be a promising target for HCC treatment. PMID:27057441

  20. Analog CMOS design for optical coherence tomography signal detection and processing.

    Science.gov (United States)

    Xu, Wei; Mathine, David L; Barton, Jennifer K

    2008-02-01

    A CMOS circuit was designed and fabricated for optical coherence tomography (OCT) signal detection and processing. The circuit includes a photoreceiver, differential gain stage and lock-in amplifier based demodulator. The photoreceiver consists of a CMOS photodetector and low noise differential transimpedance amplifier which converts the optical interference signal into a voltage. The differential gain stage further amplifies the signal. The in-phase and quadrature channels of the lock-in amplifier each include an analog mixer and switched-capacitor low-pass filter with an external mixer reference signal. The interferogram envelope and phase can be extracted with this configuration, enabling Doppler OCT measurements. A sensitivity of -80 dB is achieved with faithful reproduction of the interferometric signal envelope. A sample image of finger tip is presented.

  1. Detection and processing of phase modulated optical signals at 40 Gbit/s and beyond

    DEFF Research Database (Denmark)

    Geng, Yan

    This thesis addresses demodulation in direct detection systems and signal processing of high speed phase modulated signals in future all-optical wavelength division multiplexing (WDM) communication systems where differential phase shift keying (DPSK) or differential quadrature phase shift keying...... labeling has been proposed as an efficient way to implement packet routing and forwarding functionalities in future IP-over-WDM networks. An in-band subcarrier multiplexing (SCM) labeled signal using 40 Gbit/s DSPK payload and 25 Mbit/s non return-to-zero(NRZ) SCM label, is successfully transmitted over 80...... noise, and consequently degrade the performance of systems making use of RZ-DPSK format. All-optical signal regeneration avoiding O-E-O conversion is desired to improve signal quality in ultra long-haul transmission systems. Proof-of-principle numerical simulation results are provided, that suggest...

  2. Wide bandwidth optical signals for high range resolution measurements in water

    Science.gov (United States)

    Nash, Justin; Lee, Robert; Mullen, Linda

    2016-05-01

    Measurements with high range resolution are needed to identify underwater threats, especially when two-dimensional contrast information is insufficient to extract object details. The challenge is that optical measurements are limited by scattering phenomena induced by the underwater channel. Back-scatter results in transmitted photons being directed back to the receiver before reaching the target of interest which induces a clutter signal for ranging and a reduction in contrast for imaging. Multiple small-angle scattering (forward-scatter) results in transmitted photons being directed to unintended regions of the target of interest (spatial spreading), while also stretching the temporal profile of a short optical pulse (temporal spreading). Spatial and temporal spreading of the optical signal combine to cause a reduction in range resolution in conventional laser imaging systems. NAVAIR has investigated ways in which wide bandwidth, modulated optical signals can be utilized to improve ranging and imaging performance in turbid water environments. Experimental efforts have been conducted to investigate channel effects on the propagated frequency content, as well as different filtering and processing techniques on the return signals to maximize range resolution. Of particular interest for the modulated pulses are coherent detection and processing techniques employed by the radar community, including methods to reduce sidelobe clutter. This paper will summarize NAVAIR's work and show that wideband optical signals, in combination with the CLEAN algorithm, can indeed provide enhancements to range resolution and 3D imagery in turbid water environments.

  3. Hydex Glass and Amorphous Silicon for Integrated Nonlinear Optical Signal Processing

    CERN Document Server

    Morandotti, Roberto

    2015-01-01

    Photonic integrated circuits that exploit nonlinear optics in order to generate and process signals all-optically have achieved performance far superior to that possible electronically - particularly with respect to speed. Although silicon-on-insulator has been the leading platform for nonlinear optics for some time, its high two-photon absorption at telecommunications wavelengths poses a fundamental limitation. We review the recent achievements based in new CMOS-compatible platforms that are better suited than SOI for nonlinear optics, focusing on amorphous silicon and Hydex glass. We highlight their potential as well as the challenges to achieving practical solutions for many key applications. These material systems have opened up many new capabilities such as on-chip optical frequency comb generation and ultrafast optical pulse generation and measurement.

  4. Optical Switching for Dynamic Distribution of Wireless-Over-Fiber Signals in Active Optical Networks

    DEFF Research Database (Denmark)

    Vegas Olmos, Juan José; Rodes, Guillermo; Tafur Monroy, Idelfonso

    2012-01-01

    of a four wavelength-division-multiplexed channel system operating on a WiMax frequency band and employing an orthogonal-frequency-division-multiplexing modulation at 625 Mbits/s per channel, transmission of the data over 20 km of optical fiber, and active switching in a 1 × 16 active optical switch...

  5. Optical methods for diagnostics and feedback control in laser-induced regeneration of spine disc and joint cartilages

    Science.gov (United States)

    Sobol, Emil; Sviridov, Alexander; Omeltchenko, Alexander; Baum, Olga; Baskov, Andrey; Borchshenko, Igor; Golubev, Vladimir; Baskov, Vladimir

    2011-03-01

    In 1999 we have introduced a new approach for treatment of spine diseases based on the mechanical effect of nondestructive laser radiation on the nucleus pulposus of the intervertebral disc. Laser reconstruction of spine discs (LRD) involves puncture of the disc and non-destructive laser irradiation of the nucleus pulposus to activate reparative processes in the disc tissues. In vivo animal study has shown that LRD allows activate the growth of hyaline type cartilage in laser affected zone. The paper considers physical processes and mechanisms of laser regeneration, presents results of investigations aimed to optimize laser settings and to develop feedback control system for laser reparation in cartilages of spine and joints. The results of laser reconstruction of intervertebral discs for 510 patients have shown substantial relief of back pain for 90% of patients. Laser technology has been experimentally tested for reparation of traumatic and degenerative diseases in joint cartilage of 20 minipigs. It is shown that laser regeneration of cartilage allows feeling large (more than 5 mm) defects which usually never repair on one's own. Optical techniques have been used to promote safety and efficacy of the laser procedures.

  6. Linear and Nonlinear Impairment Compensation in Coherent Optical Transmission with Digital Signal Processing

    DEFF Research Database (Denmark)

    Porto da Silva, Edson

    Digital signal processing (DSP) has become one of the main enabling technologies for the physical layer of coherent optical communication networks. The DSP subsystems are used to implement several functionalities in the digital domain, from synchronization to channel equalization. Flexibility...... nonlinearity compensation, (II) spectral shaping, and (III) adaptive equalization. For (I), original contributions are presented to the study of the nonlinearity compensation (NLC) with digital backpropagation (DBP). Numerical and experimental performance investigations are shown for different application...... scenarios. Concerning (II), it is demonstrated how optical and electrical (digital) pulse shaping can be allied to improve the spectral confinement of a particular class of optical time-division multiplexing (OTDM) signals that can be used as a building block for fast signaling single-carrier transceivers...

  7. Optical encryption with protection against Dirac delta and plain signal attacks.

    Science.gov (United States)

    Falaggis, Konstantinos; Ramírez Andrade, Ana Hiza; Gaxiola Luna, José Gabriel; Ojeda, Carina Gutierrez; Porras-Aguilar, Rosario

    2016-10-15

    This Letter proposes an optical encryption technique that disguises the information with modular arithmetic concepts and time-varying noise components that are unknown to the receiver. Optical encryption systems that use these techniques produce a nondeterministic system response, as well as noise like image data that can easily be generated with ordinary spatial light modulators. The principle of this technique is demonstrated for the double random phase encoding (DRPE) method. The conventional DRPE method has major vulnerabilities for Dirac signal and plain signal attacks, making them impractical for secure encryption. It is shown that the proposed encryption technique provides a robustness against these types of attacks, allowing optical DRPE to be employed in secure encryptions. Moreover, applications of this Letter are not limited to DRPE alone but can also be adopted by other optical encryption techniques such as fractional Fourier transform and Fresnel-transform-based techniques.

  8. Novel scheme enabling broadcast signal transmission in WDM passive optical network

    Institute of Scientific and Technical Information of China (English)

    Xuejiao Ma; Chaoqin Gan

    2011-01-01

    @@ We present a novel method for providing broadcast signal transmission in a wavelength division multiplex-ing passive optical network (WDM-PON).An unmodulated optical carrier for downstream transmission and a pair of unmodulated single-side band subcarriers are utilized for broadcast delivery and upstream transmission, respectively.System performance at 2.5-Gb/s downlupstream and 2.5-Gb/s broadcast trans-mission is also investigated.%We present a novel method for providing broadcast signal transmission in a wavelength division multiplexing passive optical network (WDM-PON).An unmodulated optical carrier for downstream transmission and a pair of unmodulated single-side band subcarriers are utilized for broadcast delivery and upstream transmission, respectively.System performance at 2.5-Gb/s down/upstream and 2.5-Gb/s broadcast transmission is also investigated.

  9. Compensation of chromatic and polarization mode dispersion in fiber-optic communication lines in microwave signals transmittion.

    Science.gov (United States)

    Ermolaev, A. N.; Krishpents, G. P.; Davydov, V. V.; Vysoczkiy, M. G.

    2016-08-01

    Methods of dispersion compensation in fiber-optic communication lines. A new proposed method of electronic dispersion compensation in the transmission of microwave signals through fiber-optic lines. Represents is proposed the results of experimental studies of this method.

  10. Pulsed injection of the feedback signal to a cw and pulsed RF excited CO II slab-waveguide laser

    Science.gov (United States)

    Wojaczek, Dorota A.; Plinski, Edward F.; Rosinski, Lukasz; Trawinski, Robert; Dobrucki, Andrzej B.

    2007-05-01

    The experiment is performed on a three-mirror laser resonator. The injection is arranged in two ways: by a feedback from the movable third mirror, and by chopping the running back laser beam when the third mirror is stable.

  11. Significant Performance Advantage of Electroabsorption Modulator Integrated Distributed Feedback Laser (EML) Transmitter in Transporting Multicarrier QAM Signals

    NARCIS (Netherlands)

    Chand, Naresh; Bakker, Laurens; Veen, van Dora; Yadvish, Robert D.

    2001-01-01

    Data are presented that show that, for transporting quadrature amplitude modulated (QAM) radiofrequency (RF) subcarriers in suboctave frequency range, electroabsorption modulator integrated distributed feedback lasers (EMLs) can he modulated with significantly higher (2.5 times) modulation index wit

  12. Implementation of an optical S-R flip-flop with polarization encoded light signal

    Institute of Scientific and Technical Information of China (English)

    Debajyoti; Samanta; Sourangshu; Mukhopadhyay

    2009-01-01

    A new method is proposed to implement an optical S-R flip-flop by polarization encoded light signal,necessary optical nonlinear material and half-wave plate.In this system the real time speed of operation can be achieved,and at the time of transmission the average power of a byte remains constant.This polarization encoded flip-flop can act as a memory cell.

  13. Signal Processing for Fibre-optic Distributed Sensing Techniques Employing Brillouin Scattering

    Institute of Scientific and Technical Information of China (English)

    XIAO Shang-hui; LI Li

    2009-01-01

    As fibre optic distributed scattering sensing systems are providing innovative solutions for the monitoring of large structures, Brillouin-based distributed scattering sensing techniques represent a new physical approach for structures health monitoring, which seems extremely promising and is receiving most attentions. This paper comprehensively presents some methods of signal interrogation for fibre optic Brillouin-based distributed scattering sensing technology, especially establishes an accurate Pseudo-Voigt model of Brillouin gain spectrum and gives some results on spectrum analysis and data processing.

  14. Kalman filtering to suppress spurious signals in Adaptive Optics control

    Energy Technology Data Exchange (ETDEWEB)

    Poyneer, L; Veran, J P

    2010-03-29

    In many scenarios, an Adaptive Optics (AO) control system operates in the presence of temporally non-white noise. We use a Kalman filter with a state space formulation that allows suppression of this colored noise, hence improving residual error over the case where the noise is assumed to be white. We demonstrate the effectiveness of this new filter in the case of the estimated Gemini Planet Imager tip-tilt environment, where there are both common-path and non-common path vibrations. We discuss how this same framework can also be used to suppress spatial aliasing during predictive wavefront control assuming frozen flow in a low-order AO system without a spatially filtered wavefront sensor, and present experimental measurements from Altair that clearly reveal these aliased components.

  15. Kalman filtering to suppress spurious signals in Adaptive Optics control

    Energy Technology Data Exchange (ETDEWEB)

    Poyneer, L; Veran, J P

    2010-03-29

    In many scenarios, an Adaptive Optics (AO) control system operates in the presence of temporally non-white noise. We use a Kalman filter with a state space formulation that allows suppression of this colored noise, hence improving residual error over the case where the noise is assumed to be white. We demonstrate the effectiveness of this new filter in the case of the estimated Gemini Planet Imager tip-tilt environment, where there are both common-path and non-common path vibrations. We discuss how this same framework can also be used to suppress spatial aliasing during predictive wavefront control assuming frozen flow in a low-order AO system without a spatially filtered wavefront sensor, and present experimental measurements from Altair that clearly reveal these aliased components.

  16. Nonlinear Optical Microscopy Signal Processing Strategies in Cancer

    Science.gov (United States)

    Adur, Javier; Carvalho, Hernandes F; Cesar, Carlos L; Casco, Víctor H

    2014-01-01

    This work reviews the most relevant present-day processing methods used to improve the accuracy of multimodal nonlinear images in the detection of epithelial cancer and the supporting stroma. Special emphasis has been placed on methods of non linear optical (NLO) microscopy image processing such as: second harmonic to autofluorescence ageing index of dermis (SAAID), tumor-associated collagen signatures (TACS), fast Fourier transform (FFT) analysis, and gray level co-occurrence matrix (GLCM)-based methods. These strategies are presented as a set of potential valuable diagnostic tools for early cancer detection. It may be proposed that the combination of NLO microscopy and informatics based image analysis approaches described in this review (all carried out on free software) may represent a powerful tool to investigate collagen organization and remodeling of extracellular matrix in carcinogenesis processes. PMID:24737930

  17. Quantum-limited measurements of optical signals from a geostationary satellite

    CERN Document Server

    Günthner, Kevin; Elser, Dominique; Stiller, Birgit; Bayraktar, Ömer; Müller, Christian R; Saucke, Karen; Tröndle, Daniel; Heine, Frank; Seel, Stefan; Greulich, Peter; Zech, Herwig; Gütlich, Björn; Richter, Ines; Lutzer, Michael; Philipp-May, Sabine; Meyer, Rolf; Marquardt, Christoph; Leuchs, Gerd

    2016-01-01

    The measurement of quantum signals that traveled through long distances is of fundamental and technical interest. We present quantum-limited coherent measurements of optical signals, sent from a satellite in geostationary Earth orbit to an optical ground station. We bound the excess noise that the quantum states could have acquired after having propagated 38600 km through Earth's gravitational potential as well as its turbulent atmosphere. Our results indicate that quantum communication is feasible in principle in such a scenario, highlighting the possibility of a global quantum key distribution network for secure communication.

  18. Improving the All-Optical Response of SOAs Using a Modulated Holding Signal

    DEFF Research Database (Denmark)

    Bischoff, Svend; Nielsen, Mads Lønstrup; Mørk, Jesper

    2004-01-01

    A method for increasing the all-optical modulation bandwidth of semiconductor optical amplifiers (SOAs) by use of a cross-gain-modulated (XGM) holding signal is suggested and analyzed. The bandwidth improvement is numerically demonstrated by studying wavelength conversion in an SOA-based Mach......-Zehnder interferometer (MZI) at 160 and 40 Gb/s. The new scheme is predicted to improve the extinction ratio and the minimum mark output power, as well as to reduce the amplitude jitter of the wavelength converted signal....

  19. Signal measurement system for intra-body communication using optical isolation method

    Science.gov (United States)

    Matsumoto, Kazuki; Katsuyama, Jun; Sugiyama, Ryo; Takizawa, Yasuaki; Ishii, Seita; Shinagawa, Mitsuru; Kado, Yuichi

    2014-09-01

    In this paper, we describe an induced signal measurement on the human body for developing a high-performance transceiver of an intra-body communication system. It is important to isolate awearable transceiver from an electrical instrument for precise measurement. We have developed a probe system using an optical isolation method including a laser diode, photo-diode, and optical fiber. The probe system can be successfully applied to the precise measurement of a receiving signal power at a wearable transceiver. We verify that the experimental results agree with the simulation results based on our previous channel model of intra-body communication.

  20. 1.28 Tbaud Nyquist Signal Transmission using Time-Domain Optical Fourier Transformation based Receiver

    DEFF Research Database (Denmark)

    Hu, Hao; Kong, Deming; Palushani, Evarist

    2013-01-01

    We demonstrate transmission of a 1.28-Tbaud Nyquist-OTDM signal over a record distance of 100 km with detection by time-domain optical Fourier transformation followed by FEC decoding, resulting in error-free performance for all tributaries.......We demonstrate transmission of a 1.28-Tbaud Nyquist-OTDM signal over a record distance of 100 km with detection by time-domain optical Fourier transformation followed by FEC decoding, resulting in error-free performance for all tributaries....

  1. System Impact of Cascaded All-Optical Wavelength Conversion of D(QPSK Signals in Transparent Optical Networks

    Directory of Open Access Journals (Sweden)

    Robert Elschner

    2010-02-01

    Full Text Available We will compare techniques for all-optical wavelength conversion of differentially phase-modulated signals using four-wave mixing and super-continuum generation. For the super-continuum generation, a relation between the conversion efficieny and the nonlinear phase distortion will be derived and it will be shown that this technique is not suitable for the conversion of phase-modulated signals. For the four-wave mixing, techniques for the improvement of the conversion efficiency will be studied. Mainly the suppression of Brillouin scattering and its impact on phase-distortions will be discussed. A detailed discussion of its cascadability in transparent optical networks will conclude the contribution. The introduction of a maximum outage probability can significantly relax the OSNR requirements.

  2. EXPERIMENTAL STUDIES OF ERROR COMPENSATION FOR OPTICAL SIGNAL COORDINATE DETERMINATION BY DOUBLE SYNTHESIZED APERTURE

    Directory of Open Access Journals (Sweden)

    A. G. Obolenskov

    2016-09-01

    Full Text Available Subject of Research. The paper presents theoretical and experimental analysis of dependence of the determination error of a modulated optical signal under intense background illumination on the value of mutual shift of two current-voltage characteristics if using a double synthesized aperture on multiscan position-sensitive detector. Method. The studies have been carried out on a specially designed setup, that allows scanning photosensitive area of multiscan position-sensitive detector by an optical beam that imitates intense solar illumination. At the same time the position error of determination of weak modulated optical signal coordinate is measured at different relative position of signal and background illumination, and background power. Main Results. Experimental studies have confirmed the theoretical conclusions. It is shown that the use of double synthesized aperture of multiscan position-sensitive detector with the voltage shift of the current-voltage characteristics equal to 0.4 V enables to reduce position determination error of a weak modulated signal by an order of magnitude. Practical Relevance. Research results have opened the opportunity of accuracy increase for position-sensitive systems operating under background illuminations exceeding the level of information optical signal.

  3. Stabilization of Phase of a Sinusoidal Signal Transmitted Over Optical Fiber

    Science.gov (United States)

    DAddario, Larry R.; Trink, Joseph T.

    2010-01-01

    In the process of connecting widely distributed antennas into a coherent array, it is necessary to synchronize the timing of signals at the various locations. This can be accomplished by distributing a common reference signal from a central source, usually over optical fiber. A high-frequency (RF or microwave) tone is a good choice for the reference. One difficulty is that the effective length of the optical fiber changes with temperature and mechanical stress, leading to phase instability in the received tone. This innovation provides a new way to stabilize the phase of the received tone, in spite of variations in the electrical length of the fiber. Stabilization is accomplished by two-way transmission in which part of the received signal is returned to the transmitting end over an identical fiber. The returned signal is detected and used to close an electrical servo loop whose effect is to keep constant the phase of the tone at the receiving end.

  4. Electroabsorption modulators used for all-optical signal processing and labelling

    DEFF Research Database (Denmark)

    Xu, Lin

    2004-01-01

    -optical demultiplexing experiment from 160 Gb/s to 10 Gb/s using a single EAM with a very simple waveguide structure is presented. All 16 demultiplexed tributary channels are error free with an average receiver sensitivity of –25.3 dBm. An improvement of up to 6 dB in the receiver sensitivity by regeneration...... impacts on the extinction ratio, average power and pulse width of the wavelength-converted signal. Other wavelength conversion schemes such as fibre-based cross phase modulation (XPM) and optical filtering, fibre-based Kerr switch, fibre based four-wave-mixing (FWM) and semiconductor optical amplifier...

  5. Nonlinear Transient Dynamics of Photoexcited Silicon Nanoantenna for Ultrafast All-Optical Signal Processing

    CERN Document Server

    Baranov, Denis G; Milichko, Valentin A; Kudryashov, Sergey I; Krasnok, Alexander E; Belov, Pavel A

    2016-01-01

    Optically generated electron-hole plasma in high-index dielectric nanostructures was demonstrated as a means of tuning of their optical properties. However, until now an ultrafast operation regime of such plasma driven nanostructures has not been attained. Here, we perform pump-probe experiments with resonant silicon nanoparticles and report on dense optical plasma generation near the magnetic dipole resonance with ultrafast (about 2.5 ps) relaxation rate. Basing on experimental results, we develop an analytical model describing transient response of a nanocrystalline silicon nanoparticle to an intense laser pulse and show theoretically that plasma induced optical nonlinearity leads to ultrafast reconfiguration of the scattering power pattern. We demonstrate 100 fs switching to unidirectional scattering regime upon irradiation of the nanoparticle by an intense femtosecond pulse. Our work lays the foundation for developing ultracompact and ultrafast all-optical signal processing devices.

  6. High-frequency signal generation using 1550 nm VCSEL subject to two-frequency optical injection

    Science.gov (United States)

    Consoli, Antonio; Quirce, Ana; Valle, Angel; Esquivias, Ignacio; Pesquera, Luis; García Tijero, Jose Manuel

    2013-03-01

    We experimentally investigate high-frequency microwave signal generation using a 1550 nm single-mode VCSEL subject to two-frequency optical injection. We first consider a situation in which the injected signals come from two similar VCSELs. The polarization of the injected light is parallel to that of the injected VCSEL. We obtain that the VCSEL can be locked to one of the injected signals, but the observed microwave signal is originated by beating at the photodetector. In a second situation we consider injected signals that come from two external cavity tunable lasers with a significant increase of the injected power with respect to the VCSEL-by-VCSEL injection case. The polarization of the injected light is orthogonal to that of the free-running slave VCSEL. We show that in this case it is possible to generate a microwave signal inside the VCSEL cavity.

  7. Audio Feedback -- Better Feedback?

    Science.gov (United States)

    Voelkel, Susanne; Mello, Luciane V.

    2014-01-01

    National Student Survey (NSS) results show that many students are dissatisfied with the amount and quality of feedback they get for their work. This study reports on two case studies in which we tried to address these issues by introducing audio feedback to one undergraduate (UG) and one postgraduate (PG) class, respectively. In case study one…

  8. Re-configurable digital receiver for optically envelope detected half cycle BPSK and MSK radio-on-fiber signals

    DEFF Research Database (Denmark)

    Guerrero Gonzalez, Neil; Prince, Kamau; Zibar, Darko

    2011-01-01

    novel digital receiver consists of a digital signal processing unit integrating functions such as filtering, peak-powers detection, symbol synchronization and signal demodulation for optically envelope detected half-cycle binary phase-shift-keying and minimum-shift-keying signals. Furthermore, radio......We present the first known integration of a digital receiver into optically envelope detection radio-on-fiber systems. We also present a re-configurable scheme for two different types of optically envelope detected wireless signals while keeping the complexity of used optical components low. Our......-frequency signal down-conversion is not required in our proposed approach; simplifying evens more the optical receiver front-end. We experimentally demonstrate error-free optical transmission (bit-error rate corresponding to 10−3 related to FEC-compatible levels) for both 416.6 Mbit/s half-cycle binary phase...

  9. Optical coherence tomography for blood glucose monitoring through signal attenuation

    Science.gov (United States)

    De Pretto, Lucas R.; Yoshimura, Tania M.; Ribeiro, Martha S.; de Freitas, Anderson Z.

    2016-03-01

    Development of non-invasive techniques for glucose monitoring is crucial to improve glucose control and treatment adherence in patients with diabetes. Hereafter, Optical Coherence Tomography (OCT) may offer a good alternative for portable glucometers, since it uses light to probe samples. Changes in the object of interest can alter the intensity of light returning from the sample and, through it, one can estimate the sample's attenuation coefficient (μt) of light. In this work, we aimed to explore the behavior of μt of mouse's blood under increasing glucose concentrations. Different samples were prepared in four glucose concentrations using a mixture of heparinized blood, phosphate buffer saline and glucose. Blood glucose concentrations were measured with a blood glucometer, for reference. We have also prepared other samples diluting the blood in isotonic saline solution to check the effect of a higher multiple-scattering component on the ability of the technique to differentiate glucose levels based on μt. The OCT system used was a commercial Spectral Radar OCT with 930 nm central wavelength and spectral bandwidth (FWHM) of 100 nm. The system proved to be sensitive for all blood glucose concentrations tested, with good correlations with the obtained attenuation coefficients. A linear tendency was observed, with an increase in attenuation with higher values of glucose. Statistical difference was observed between all groups (p<0.001). This work opens the possibility towards a non-invasive diagnostic modality using OCT for glycemic control, which eliminates the use of analytes and/or test strips, as in the case with commercially available glucometers.

  10. Review of Brain-Machine Interfaces Used in Neural Prosthetics with New Perspective on Somatosensory Feedback through Method of Signal Breakdown.

    Science.gov (United States)

    Vidal, Gabriel W Vattendahl; Rynes, Mathew L; Kelliher, Zachary; Goodwin, Shikha Jain

    2016-01-01

    The brain-machine interface (BMI) used in neural prosthetics involves recording signals from neuron populations, decoding those signals using mathematical modeling algorithms, and translating the intended action into physical limb movement. Recently, somatosensory feedback has become the focus of many research groups given its ability in increased neural control by the patient and to provide a more natural sensation for the prosthetics. This process involves recording data from force sensitive locations on the prosthetics and encoding these signals to be sent to the brain in the form of electrical stimulation. Tactile sensation has been achieved through peripheral nerve stimulation and direct stimulation of the somatosensory cortex using intracortical microstimulation (ICMS). The initial focus of this paper is to review these principles and link them to modern day applications such as restoring limb use to those who lack such control. With regard to how far the research has come, a new perspective for the signal breakdown concludes the paper, offering ideas for more real somatosensory feedback using ICMS to stimulate particular sensations by differentiating touch sensors and filtering data based on unique frequencies.

  11. Ultralow-phase-noise millimetre-wave signal generator assisted with an electro-optics-modulator-based optical frequency comb.

    Science.gov (United States)

    Ishizawa, A; Nishikawa, T; Goto, T; Hitachi, K; Sogawa, T; Gotoh, H

    2016-05-17

    Low-noise millimetre-wave signals are valuable for digital sampling systems, arbitrary waveform generation for ultra-wideband communications, and coherent radar systems. However, the phase noise of widely used conventional signal generators (SGs) will increase as the millimetre-wave frequency increases. Our goal has been to improve commercially available SGs so that they provide a low-phase-noise millimetre-wave signal with assistance from an electro-optics-modulator-based optical frequency comb (EOM-OFC). Here, we show that the phase noise can be greatly reduced by bridging the vast frequency difference between the gigahertz and terahertz ranges with an EOM-OFC. The EOM-OFC serves as a liaison that magnifies the phase noise of the SG. With the EOM-OFC used as a phase noise "booster" for a millimetre-wave signal, the phase noise of widely used SGs can be reduced at an arbitrary frequency f (6 ≦ f ≦ 72 GHz).

  12. Optical stimulated Luminescence Signal on Modern Fluvial Deposit in Taiwan

    Science.gov (United States)

    Chen, Y. G.; Wu, T. S.; Chen, Y. W.; Kuo, Y. T.

    2014-12-01

    The river terraces overlain by fluvial and debris-flow deposit are widely distributed in Taiwan due to its active tectonic situation. They are not only critical in reconstructing the river evolution, but also of importance in understanding neotectonics. However, the age estimation for the terraces has their own problems by C-14 as well as OSL (Optical Stimulated Luminescence) dating method. For C-14 method, the major problem is the difficulty in discovering the suitable samples, but for OSL method the zeroing effect of the sediments becomes the major barrier if quartz SAR (Single Aliquot Regenerative) procedure is applied. In order to test the residual dose from different drainage areas in Taiwan, modern deposits were collected from 13 main rivers and 3 samples for each from upper-stream to downstream. The apparent dose of modern fluvial deposit was defined as residual dose and believed to be able to give a hint for estimating the zeroing effect for river terraces. Quartz SAR OSL procedure on small aliquot was adopted for all samples in this study. Our results show the residual dose in western Taiwan strongly relies on the source from. If we further apply the mean value of smallest 5% on samples from modern debris flow deposits in upper-stream, the residual dose rise up as high as ~40Gy but lower down to ~15Gy for samples collected from river mouth estuary. It implies that there will be a large error when evaluating the age of debris deposit terrace by quartz SAR OSL procedure. However, if the modern river does not suffer from debris flow in upper-stream, the residual dose is ~5Gy in upper stream and only -0.7~2Gy to the lower steam estuary, which provide better chance to derive relatively reliable ages. We also find that the luminescence characteristics is different between the samples in western and eastern Taiwan respectively. The quartz grains from eastern Taiwan are much dimer than those of the western Taiwan. We may therefore face severe challenge to approach

  13. A Design of High—precision High—Voltage Fiber—Optic Analog Signal Isolation Converter

    Institute of Scientific and Technical Information of China (English)

    李建伟; 许留伟; 等

    2002-01-01

    This paper introduces a design of high-precision high-voltage fiber-optic analog signal isolation converter based on the technology of Voltage-to-Frequency(V/F) and Frequency-to-Voltage(F/V) conversion.It describes the principle,system configuration and hardware desin.

  14. A design of High-precision High-Voltage Fiber-Optic Analog Signal Isolation Converter

    Institute of Scientific and Technical Information of China (English)

    李建伟; 许留伟; 刘小宁; 杨雷

    2002-01-01

    This paper introduces a design of high-prectison high-voltage fiber-optic analog sig-nal isoaltion converter based on the technology of Voltage-to-Fequency (V/F)and Frequency -to Voltage(F/V) conversion It describes the principle ,system configuration and hardware design

  15. Linear all-optical signal processing using silicon micro-ring resonators

    DEFF Research Database (Denmark)

    Ding, Yunhong; Ou, Haiyan; Xu, Jing

    2016-01-01

    Silicon micro-ring resonators (MRRs) are compact and versatile devices whose periodic frequency response can be exploited for a wide range of applications. In this paper, we review our recent work on linear all-optical signal processing applications using silicon MRRs as passive filters. We focus...

  16. Optically envelope detected QAM and QPSK RF modulated signals in hybrid wireless-fiber systems

    DEFF Research Database (Denmark)

    Tafur Monroy, Idelfonso; Prince, Kamau; Seoane, Jorge;

    2009-01-01

    from a 1.6 GHz carrier frequency to an IF at 500 MHz, requiring no high frequency local oscillator and mixer at the remote base station. This result proves the feasibility of optical envelope detection for complex modulation formats of RF signals for hybrid wireless-fiber transmission links....

  17. All-optical wavelength conversion and signal regeneration using an electroabsorption modulator

    DEFF Research Database (Denmark)

    Højfeldt, Sune; Bischoff, Svend; Mørk, Jesper

    1999-01-01

    All-optical wavelength conversion in an InGaAsP quantum well electroabsorption modulator is studied at different bit-rates. We present theoretical results showing wavelength conversion efficiency in agreement with existing experimental results, and signal regeneration capability is demonstrated....

  18. All-Optical Signal Processing for 640 Gbit/s Applications

    DEFF Research Database (Denmark)

    Mulvad, Hans Christian Hansen

    2008-01-01

    This thesis concerns all-optical signal processing technologies for ultra-high serial data rates up to 640 Gbit/s. Firstly, time-division add-drop multiplexing at 640 Gbit/s is demonstrated for the first time using two different fibre-based switching techniques. Secondly, a novel principle...

  19. Optical signal processing up to 1.28 Tbits/s

    DEFF Research Database (Denmark)

    Mulvad, Hans Christian Hansen; Oxenløwe, Leif Katsuo; Galili, Michael;

    2009-01-01

    Techniques for 640 Gbit/s optical signal processing are described, including demultiplexing, clock recovery, transmission, wavelength conversion, add-drop multiplexing, and timing-jitter tolerance. Demultiplexing at 1.28 Tbit/s is presented, with preliminary results for 1.28 Tbit/s transmission....

  20. Converged wireline and wireless signal distribution in optical fiber access networks

    DEFF Research Database (Denmark)

    Prince, Kamau

    This thesis presents results obtained during the course of my doctoral studies into the transport of fixed and wireless signaling over a converged otpical access infrastructure. In the formulation, development and assessment of a converged paradigma for multiple-services delivery via optical access...

  1. A transfer function approach to the small-signal response of saturated semiconductor optical amplifiers

    DEFF Research Database (Denmark)

    Nielsen, Mads Lønstrup; Blumenthal, D. J.; Mørk, Jesper

    2000-01-01

    A theoretical analysis of the small-signal frequency response (SSFR) of a wavelength converter based on cross-gain modulation in a semiconductor optical amplifier with a finite waveguide loss is presented. We use a transfer function formalism to explain the resonant behavior of the frequency...

  2. Transmission and transparent wavelength conversion of an optically labeled signal using ASK/DPSK orthogonal modulation

    DEFF Research Database (Denmark)

    Chi, Nan; Zhang, Jianfeng; Holm-Nielsen, Pablo Villanueva

    2003-01-01

    We report an experimental investigation of transmission and transparent wavelength conversion properties of a two-level optically labeled signal using amplitude-shift-keying/differential-phase-shift-keying orthogonal modulation. Error-free transmission of a 10-Gb/s payload and 2.5-Gb/s label over...

  3. A novel optical transmission link with DHT-based constant envelope optical OFDM signal

    Science.gov (United States)

    Ma, Jianxin; Liang, Hao

    2013-07-01

    In this paper, we have proposed a novel optical OFDM transmission link that takes advantages of discrete Hartley Transform (DHT) and constant envelope (CE) modulation, obtaining DHT-based constant envelope optical OFDM. The numerical results show that this design achieves better performance when compared with conventional O-OFDM in terms of bit error rate (BER) and peak-to-average power ratio (PAPR). The impact of phase modulation index (PMI) on both PAPR and noise tolerance is investigated. Since the scheme has simplified design, it is believed to be a cost-effective in the practical implement.

  4. Experiment on the phase congruency of distributed feedback optical fiber laser hydrophones%分布反馈光纤激光水听器相位一致性的测试方法

    Institute of Scientific and Technical Information of China (English)

    宋晓燕; 张文涛; 何俊; 李芳; 刘育梁

    2011-01-01

    在传统压电水听器相位一致性测试的基础上提出了分布反馈(DFB)光纤激光水听器相位一致性的测试方法,并搭建了测试系统.采用偏振无关的非平衡迈克尔逊干涉仪和归一化的相位载波(PGC)解调方案,解调出光纤激光水听器感受的水声信号,并与参考压电水听器作对比,使用高精度相位检测器将两信号转化为相位差信号:重复测量第二支光纤激光水听器:将两个相位差值作比较即可得到光纤激光水听器的相位一致性.实验证明了测试系统的稳定性;同时对光纤激光水听器的相位一致性进行了测试和分析,证明了光纤激光水听器具有很高的相位一致性.%A method of detecting the phase congruency of distributed feedback (DFB) optical fiber laser hydrophones was proposed based on detection system of traditional piezoelectric hydrophones, and the phase congruency detection system was set up.A polarization-insensitive unbalanced Michelson fiber interferometer was employed to transfer the frequency shifts to the phase shifts of the interferometer.After converting the output optical signal of the interferometer to electric signal, a normalized phase generated carrier (PGC) demodulation technique was used to demodulate the acoustic signal.Then the demodulated signal and the signal of the reference piezoelectric hydrophone were input into a high-resolution digital phase detector to get the phase difference.Repeat the above steps with another optical fiber laser hydrophone and compare the two results, the phase congruency between the two optical fiber laser hydrophones would be calculated.Corresponding experiments show the reliability of the phase congruency detection system and the high phase congruency between optical fiber laser hydrophones.

  5. Stimulated Brillouin scattering gain bandwidth reduction and applications in microwave photonics and optical signal processing

    Science.gov (United States)

    Preussler, Stefan; Schneider, Thomas

    2016-03-01

    Stimulated Brillouin scattering (SBS) is one of the most dominant nonlinear effects in standard single-mode fibers and its unique spectral characteristics, especially the narrow bandwidth, enable many different applications. Most of the applications would benefit from a narrower bandwidth. Different methods for the bandwidth reduction of SBS in optical fibers are presented and discussed. A bandwidth reduction down to 17% of the natural gain can be achieved by the superposition of the gain with two losses or the utilization of a multistage system. Furthermore, applications in the field of microwave photonics and optical signal processing like high-resolution spectroscopy of communication signals, the storage of optical data packets as well as the processing of frequency combs including generation of millimeter waves and ideal sinc-shaped Nyquist pulses are presented.

  6. Adaptive coded spreading OFDM signal for dynamic-λ optical access network

    Science.gov (United States)

    Liu, Bo; Zhang, Lijia; Xin, Xiangjun

    2015-12-01

    This paper proposes and experimentally demonstrates a novel adaptive coded spreading (ACS) orthogonal frequency division multiplexing (OFDM) signal for dynamic distributed optical ring-based access network. The wavelength can be assigned to different remote nodes (RNs) according to the traffic demand of optical network unit (ONU). The ACS can provide dynamic spreading gain to different signals according to the split ratio or transmission length, which offers flexible power budget for the network. A 10×13.12 Gb/s OFDM access with ACS is successfully demonstrated over two RNs and 120 km transmission in the experiment. The demonstrated method may be viewed as one promising for future optical metro access network.

  7. Linear methods for input scenes restoration from signals of optical-digital pattern recognition correlator

    Science.gov (United States)

    Starikov, Sergey N.; Konnik, Mikhail V.; Manykin, Edward A.; Rodin, Vladislav G.

    2009-04-01

    Linear methods of restoration of input scene's images in optical-digital correlators are described. Relatively low signal to noise ratio of a camera's photo sensor and extensional PSF's size are special features of considered optical-digital correlator. RAW-files of real correlation signals obtained by digital photo sensor were used for input scene's images restoration. It is shown that modified evolution method, which employs regularization by Tikhonov, is better among linear deconvolution methods. As a regularization term, an inverse signal to noise ratio as a function of spatial frequencies was used. For additional improvement of restoration's quality, noise analysis of boundary areas of the image to be reconstructed was performed. Experimental results on digital restoration of input scene's images are presented.

  8. Circular polarization intrinsic optical signal recording of stimulus-evoked neural activity.

    Science.gov (United States)

    Lu, Rong-Wen; Zhang, Qiu-Xiang; Yao, Xin-Cheng

    2011-05-15

    Linear polarization intrinsic optical signal (LP-IOS) measurement can provide sensitive detection of neural activities in stimulus-activated neural tissues. However, the LP-IOS magnitude and signal-to-noise ratio (SNR) are highly correlated with the nerve orientation relative to the polarization plane of the incident light. Because of the complexity of orientation dependency, LP-IOS optimization and outcome interpretation are time consuming and complicated. In this study, we demonstrate the feasibility of circular polarization intrinsic optical signal (CP-IOS) measurement. Our theoretical modeling and experimental investigation indicate that CP-IOS magnitude and SNR are independent from the nerve orientation. Therefore, CP-IOS promises a practical method for polarization IOS imaging of complex neural systems.

  9. Optical differential phase-shift keyed signal generation, transmission and detection

    Science.gov (United States)

    Lize, Yannick Keith

    When encoding information on an electromagnetic wave such as infrared light, to be transmitted through an optical fibre in telecommunication networks, any of the physical properties of light can be modulated. Light has a frequency, intensity, polarization and a phase. Until recently, optical communication systems strictly employed conventional intensity (IM) modulation signals in either non return-to-zero (NRZ) or return-to-zero (RZ) format. But a number of advanced optical modulation formats have attracted increasing attention in the last few years. One prime example is the phase-shift-keyed (PSK) family of formats which carry the information on the optical phase. Since absolute phase is not easily detected through coherent demodulation, differential encoding in which the phase of the preceding bit is used as a relative phase reference for demodulation has become a method of choice for phase modulated signals. The result in the differential-phase-shift-keyed (DPSK) formats, which carry the information in the difference in optical phase between successive bits. In this thesis by article, composed of six papers, we investigate the generation, transmission and demodulation of DPSK in optical fibre transmission systems. We propose a novel way to encode optical packets using DPSK in our investigation of the generation. We also investigate transmission effects monitoring using a novel partial-bit delay interferometer-assisted clock tone monitoring method for sensitive optical-signal-to-noise ratio (OSNR), chromatic dispersion and polarization mode dispersion monitoring. Then we look at the demodulation of DPSK, first investigating the reduced tolerances and power penalties of DPSK demodulation when more than one bit delay is used in the interferometer. We also propose an optical error correction method combining DPSK optical logic gates with electronic logic gates to improve receiver sensitivity and transmission impairment tolerances. Finally we redefine the previously

  10. Theoretical Design of a Depolarized Interferometric Fiber-Optic Gyroscope (IFOG) on SMF-28 Single-Mode Standard Optical Fiber Based on Closed-Loop Sinusoidal Phase Modulation with Serrodyne Feedback Phase Modulation Using Simulation Tools for Tactical and Industrial Grade Applications.

    Science.gov (United States)

    Pérez, Ramón José; Álvarez, Ignacio; Enguita, José María

    2016-04-27

    This article presents, by means of computational simulation tools, a full analysis and design of an Interferometric Fiber-Optic Gyroscope (IFOG) prototype based on a closed-loop configuration with sinusoidal bias phase- modulation. The complete design of the different blocks, optical and electronic, is presented, including some novelties as the sinusoidal bias phase-modulation and the use of an integrator to generate the serrodyne phase-modulation signal. The paper includes detailed calculation of most parameter values, and the plots of the resulting signals obtained from simulation tools. The design is focused in the use of a standard single-mode optical fiber, allowing a cost competitive implementation compared to commercial IFOG, at the expense of reduced sensitivity. The design contains an IFOG model that accomplishes tactical and industrial grade applications (sensitivity ≤ 0.055 °/h). This design presents two important properties: (1) an optical subsystem with advanced conception: depolarization of the optical wave by means of Lyot depolarizers, which allows to use a sensing coil made by standard optical fiber, instead by polarization maintaining fiber, which supposes consequent cost savings and (2) a novel and simple electronic design that incorporates a linear analog integrator with reset in feedback chain, this integrator generating a serrodyne voltage-wave to apply to Phase-Modulator (PM), so that it will be obtained the interferometric phase cancellation. This particular feedback design with sawtooth-wave generated signal for a closed-loop configuration with sinusoidal bias phase modulation has not been reported till now in the scientific literature and supposes a considerable simplification with regard to previous designs based on similar configurations. The sensing coil consists of an 8 cm average diameter spool that contains 300 m of standard single-mode optical-fiber (SMF-28 type) realized by quadrupolar winding. The working wavelength will be

  11. Theoretical Design of a Depolarized Interferometric Fiber-Optic Gyroscope (IFOG) on SMF-28 Single-Mode Standard Optical Fiber Based on Closed-Loop Sinusoidal Phase Modulation with Serrodyne Feedback Phase Modulation Using Simulation Tools for Tactical and Industrial Grade Applications

    Science.gov (United States)

    Pérez, Ramón José; Álvarez, Ignacio; Enguita, José María

    2016-01-01

    This article presents, by means of computational simulation tools, a full analysis and design of an Interferometric Fiber-Optic Gyroscope (IFOG) prototype based on a closed-loop configuration with sinusoidal bias phase- modulation. The complete design of the different blocks, optical and electronic, is presented, including some novelties as the sinusoidal bias phase-modulation and the use of an integrator to generate the serrodyne phase-modulation signal. The paper includes detailed calculation of most parameter values, and the plots of the resulting signals obtained from simulation tools. The design is focused in the use of a standard single-mode optical fiber, allowing a cost competitive implementation compared to commercial IFOG, at the expense of reduced sensitivity. The design contains an IFOG model that accomplishes tactical and industrial grade applications (sensitivity ≤ 0.055 °/h). This design presents two important properties: (1) an optical subsystem with advanced conception: depolarization of the optical wave by means of Lyot depolarizers, which allows to use a sensing coil made by standard optical fiber, instead by polarization maintaining fiber, which supposes consequent cost savings and (2) a novel and simple electronic design that incorporates a linear analog integrator with reset in feedback chain, this integrator generating a serrodyne voltage-wave to apply to Phase-Modulator (PM), so that it will be obtained the interferometric phase cancellation. This particular feedback design with sawtooth-wave generated signal for a closed-loop configuration with sinusoidal bias phase modulation has not been reported till now in the scientific literature and supposes a considerable simplification with regard to previous designs based on similar configurations. The sensing coil consists of an 8 cm average diameter spool that contains 300 m of standard single-mode optical-fiber (SMF-28 type) realized by quadrupolar winding. The working wavelength will be

  12. Theoretical Design of a Depolarized Interferometric Fiber-Optic Gyroscope (IFOG on SMF-28 Single-Mode Standard Optical Fiber Based on Closed-Loop Sinusoidal Phase Modulation with Serrodyne Feedback Phase Modulation Using Simulation Tools for Tactical and Industrial Grade Applications

    Directory of Open Access Journals (Sweden)

    Ramón José Pérez

    2016-04-01

    Full Text Available This article presents, by means of computational simulation tools, a full analysis and design of an Interferometric Fiber-Optic Gyroscope (IFOG prototype based on a closed-loop configuration with sinusoidal bias phase- modulation. The complete design of the different blocks, optical and electronic, is presented, including some novelties as the sinusoidal bias phase-modulation and the use of an integrator to generate the serrodyne phase-modulation signal. The paper includes detailed calculation of most parameter values, and the plots of the resulting signals obtained from simulation tools. The design is focused in the use of a standard single-mode optical fiber, allowing a cost competitive implementation compared to commercial IFOG, at the expense of reduced sensitivity. The design contains an IFOG model that accomplishes tactical and industrial grade applications (sensitivity ≤ 0.055 °/h. This design presents two important properties: (1 an optical subsystem with advanced conception: depolarization of the optical wave by means of Lyot depolarizers, which allows to use a sensing coil made by standard optical fiber, instead by polarization maintaining fiber, which supposes consequent cost savings and (2 a novel and simple electronic design that incorporates a linear analog integrator with reset in feedback chain, this integrator generating a serrodyne voltage-wave to apply to Phase-Modulator (PM, so that it will be obtained the interferometric phase cancellation. This particular feedback design with sawtooth-wave generated signal for a closed-loop configuration with sinusoidal bias phase modulation has not been reported till now in the scientific literature and supposes a considerable simplification with regard to previous designs based on similar configurations. The sensing coil consists of an 8 cm average diameter spool that contains 300 m of standard single-mode optical-fiber (SMF-28 type realized by quadrupolar winding. The working

  13. Chaotic systems in optical communications

    Science.gov (United States)

    Siuzdak, J.

    2016-09-01

    Communications application of chaotic oscillations of lasers with optoelectronic feedback was discussed. The possibility of eavesdropping of the transmission was analyzed. It was proved that if the rogue party precisely knows parameters of the chaotic system it may recreate the entire signals solely by observation of the optical signal power causing security breach.

  14. Signaling-based path-segment protection in mesh optical networks

    Institute of Scientific and Technical Information of China (English)

    Yueming Lu; Chao Zou; Qiushi Wang; Yuefeng Ji

    2011-01-01

    Path protections have become increasingly important for current mesh optical networks because fast restorations in generalized multiprotocol label switching (GMPLS) networks are uncertain. However, setting up additional disjoint paths to protect connections leads to more path setup blocking and signaling collisions. We analyze signaling collisions, path blocking and blocking probability, as well as calculate node-to-node blocking probabilities. A signaling-based path-segment protection (PSP) is proposed, which integrates segment protections and path protections as well as enhances the performance of path protections and ring protections. The setup of PSP connections causes less blocking probability than the setup of path protection connections in the simulations.%Path protections have become increasingly important for current mesh optical networks because fast restorations in generalized multiprotocol label switching (GMPLS) networks are uncertain.However,setting up additional disjoint paths to protect connections leads to more path setup blocking and signaling collisions.We analyze signaling collisions,path blocking and blocking probability,as well as calculate node-to-node blocking probabilities.A signaling-based path-segment protection (PSP) is proposed,which integrates segment protections and path protections as well as enhances the performance of path protections and ring protections.The setup of PSP connections causes less blocking probability than the setup of path protection connections in the simulations.Recently,with the emergence of new protection and restoration methods,mesh topologies have gradually replaced ring topologies,especially in optical transport networks (OTNs)[1],automatically switched optical networks (ASONs)[2],generalized multiprotocol label switching (GMPLS) protocol networks[3,4],and packet transport networks (PTNs)[5].However,fast restoration methods currently face some challenges in China.

  15. The use of balanced homodyne and squeezed states for detecting weak optical signals in a Michelson interferometer

    Energy Technology Data Exchange (ETDEWEB)

    Ben-Aryeh, Y., E-mail: phr65yb@physics.technion.ac.i [Physics Department, Technion - Israel Institute of Technology, Haifa 32000 (Israel)

    2011-03-07

    The possibility of using squeezed states and balanced homodyne detection of optical signals in a Michelson interferometer is discussed. The present analysis describes photon statistics measurements effects related to quadrature balanced homodyne detection showing the advantage of using this scheme for detecting weak optical signals.

  16. Optical guidelines and signal quality for LDA applications in circular pipes

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Z. [Sulzer Innotec, 8401, Winterthur (Switzerland); Faculty of Science and Technology, University of Applied Sciences Aargau, 5210, Windisch (Switzerland)

    2004-07-01

    The optical performance of laser Doppler anemometer (LDA) technology in applications to circular pipes with an external plane wall has been clarified and quantified. It is shown that optical aberration is a persistent feature in such LDA measurements and measurements from each direction along a full pipe diameter are needed to obtain the flow distribution. For measurements of axial velocities in a circular pipe no special care has to be taken, even if the optical plane deviates from the pipe axis. For measurements of tangential and radial velocities detailed operating guidelines have been presented with respect to the shift of the measurement volume, its optical properties and the beam waist dislocations. The analysis reveals the possible influences on both the signal quality and the measurement accuracy. (orig.)

  17. Analytical analysis of modulated signal in apertureless scanning near-field optical microscopy.

    Science.gov (United States)

    Lo, Y L; Chuang, C H

    2007-11-26

    Eliminating background-scattering effects from the detected signal is crucial in improving the performance of super-high-resolution apertureless scanning near-field optical microscopy (A-SNOM). Using a simple mathematical model of the A-SNOM detected signal, this study explores the respective effects of the phase modulation depth, the wavelength and angle of the incident light, and the amplitude of the tip vibration on the signal contrast and signal intensity. In general, the results show that the background-noise decays as the order of the Bessel function increases and that higher-order harmonic frequencies yield an improved signal contrast. Additionally, it is found that incident light with a longer wavelength improves the signal contrast for a constant order of modulation frequency. The signal contrast can also be improved by reducing the incident angle of the incident light. Finally, it is demonstrated that sample stage scanning yields an improved imaging result. However, tip scanning provides a reasonable low-cost and faster solution in the smaller scan area. The analytical results presented in this study enable a better understanding of the complex detected signal in A-SNOM and provide insights into methods of improving the signal contrast of the A-SNOM measurement.

  18. Time-delay signatures in multi-transverse mode VCSELs subject to double-cavity polarization-rotated optical feedback

    Science.gov (United States)

    Lin, Hong; Khurram, Aliza; Hong, Yanhua

    2016-10-01

    Time delay (TD) signatures are studied experimentally in orthogonal polarizations and in individual transverse modes respectively in a VCSEL operating with three transverse modes. Different types of concealment of the TD signatures are observed when the polarization of feedback is rotated through large angles. Effects of feedback strength and external cavity length on the TD signatures are investigated. Weak feedback leads to better concealment of the TD signatures in the dominant polarization. When the round-trip time difference between the two external cavities is close to a half of the relaxation oscillation period, the TD signatures are minimized.

  19. A 2-10 GHz GaAs MMIC opto-electronic phase detector for optical microwave signal generators

    DEFF Research Database (Denmark)

    Bruun, Marlene; Gliese, Ulrik Bo; Petersen, Anders Kongstad;

    1994-01-01

    Optical transmission of microwave signals becomes increasingly important. Techniques using beat between optical carriers of semiconductor lasers are promising if efficient optical phase locked loops are realized. A highly efficient GaAs MMIC optoelectronic phase detector for a 2-10 GHz OPLL...

  20. Asynchronous, all-optical signal processing based on the self-frequency shift of a gigahertz Raman soliton.

    Science.gov (United States)

    Kato, Masao; Fujiura, Kazuo; Kurihara, Takashi

    2005-03-10

    Ultrafast asynchronous all-optical signal processing is experimentally demonstrated. It is based on the intensity-dependent, self-frequency shift of a gigahertz Raman soliton. We demonstrate error-free, asynchronous, all-optical, bit-by-bit, self-signal recognition and demultiplexing from contended optical packets without use of an optical buffer, control pulse, or bit-phase synchronization. Fourfold, contended, 9.95-Gbit/s optical packets are transmitted through a conventional repeater span of 80 km and simultaneously demultiplexed to multiwavelength 9.95-Gbit/s optical packets with 0.5-dB processing sensitivity. Furthermore, we successfully accomplish demultiplexing from overlapping signals in contended optical packets with better than 3-dB recognition sensitivity. We confirm the capability of realizing a 3x cascade operation from bit-error-rate measurements.