Relevant bibliographies by topics / Fast Optical Signal

Academic literature on the topic 'Fast Optical Signal'

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Published: 11 March 2023

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Journal articles on the topic "Fast Optical Signal"

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Sheng, Zhiyong, Dandan Qu, Yuan Zhang, and Dan Yang. "The Fast Detection and Identification Algorithm of Optical Fiber Intrusion Signals." Algorithms 11, no. 9 (August 23, 2018): 129. http://dx.doi.org/10.3390/a11090129.

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With the continuous development of optical fiber sensing technology, the Optical Fiber Pre-Warning System (OFPS) has been widely used in various fields. The OFPS identifies the type of intrusion based on the detected vibration signal to monitor the surrounding environment. Aiming at the real-time requirements of OFPS, this paper presents a fast algorithm to accelerate the detection and recognition processing of optical fiber intrusion signals. The algorithm is implemented in an embedded system that is composed of a digital signal processor (DSP). The processing flow is divided into two parts. First, the dislocation processing method is adopted for the sum processing of original signals, which effectively improves the real-time performance. The filtered signals are divided into two parts and are parallel processed by two DSP boards to save time. Then, the data is input into the identification module for feature extraction and classification. Experiments show that the algorithm can effectively detect and identify the optical fiber intrusion signals. At the same time, it accelerates the processing speed and meets the real-time requirements of OFPS for detection and identification.
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Radhakrishnan, Harsha, Wim Vanduffel, Hong Ping Deng, Leeland Ekstrom, David A. Boas, and Maria Angela Franceschini. "Fast optical signal not detected in awake behaving monkeys." NeuroImage 45, no. 2 (April 2009): 410–19. http://dx.doi.org/10.1016/j.neuroimage.2008.12.014.

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Ziskind-Conhaim, Lea, and Stephen Redman. "Spatiotemporal Patterns of Dorsal Root–Evoked Network Activity in the Neonatal Rat Spinal Cord: Optical and Intracellular Recordings." Journal of Neurophysiology 94, no. 3 (September 2005): 1952–61. http://dx.doi.org/10.1152/jn.00209.2005.

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Spatiotemporal patterns of dorsal root–evoked potentials were studied in transverse slices of the rat spinal cord by monitoring optical signals from a voltage-sensitive dye with multiple-photodiode optic camera. Typically, dorsal root stimulation generated two basic waveforms of voltage images: dual-component images consisting of fast, spike-like signal followed by a slow signal in the dorsal horn, and small, slow signals in the ventral horn. To qualitatively relate the optical signals to membrane potentials, whole cell recordings were combined with measurements of light absorption in the area around the soma. The slow optical signals correlated closely with subthreshold postsynaptic potentials in all regions of the cord. The spike-like component was not associated with postsynaptic action potentials, suggesting that the fast signal was generated by presynaptic action potentials. Firing in a single neuron could not be detected optically, implying that local voltage images originated from synchronously activated neuronal ensembles. Blocking glutamatergic synaptic transmission inhibited excitatory postsynaptic potentials (EPSPs) and significantly reduced the slow optical signals, indicating that they were mediated by glutamatergic synapses. Suppressing glycine-mediated inhibition increased the amplitude of both optical signals and EPSPs, while blocking GABAA receptor–mediated synapses, increased the amplitude and time course of EPSPs and prolonged the duration of voltage images in larger areas of the slice. The close correlation between evoked EPSPs and their respective local voltage images shows the advantage of the high temporal resolution optical system in measuring both the spatiotemporal dynamics of segmental network excitation and integrated potentials of neuronal ensembles at identified sites.
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YAO, XIN-CHENG, LEI LIU, and YANG-GUO LI. "INTRINSIC OPTICAL SIGNAL IMAGING OF RETINAL ACTIVITY IN FROG EYE." Journal of Innovative Optical Health Sciences 02, no. 02 (April 2009): 201–8. http://dx.doi.org/10.1142/s1793545809000462.

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Using a near-infrared (NIR) light flood-illumination imager equipped with a high-speed (120 Hz) CCD camera, we demonstrated optical imaging of stimulus-evoked retinal activity in isolated, but intact, frog eye. Both fast and slow transient intrinsic optical signals (IOSs) were observed. Fast optical response occurred immediately after the stimulus onset, could reach peak magnitude within 100 ms, and correlated tightly with ON and OFF edges of the visible light stimulus; while slow optical response lasted a relatively long time (many seconds). High-resolution images revealed both positive (increasing) and negative (decreasing) IOSs, and dynamic optical change at individual CCD pixels could often exceed 10% of the background light intensity. Our experiment on isolated eye suggests that further development of fast, high (sub-cellular) resolution fundus imager will allow robust detection of fast IOSs in vivo, and thus allow noninvasive, three-dimensional evaluation of retinal neural function.
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Yao, Xincheng, and Tae-Hoon Kim. "Fast intrinsic optical signal correlates with activation phase of phototransduction in retinal photoreceptors." Experimental Biology and Medicine 245, no. 13 (June 19, 2020): 1087–95. http://dx.doi.org/10.1177/1535370220935406.

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Quantitative assessment of physiological condition of retinal photoreceptors is desirable for better detection and treatment evaluation of eye diseases that can cause photoreceptor dysfunctions. Functional intrinsic optical signal (IOS) imaging, also termed as optoretinography (ORG) or optophysiology, has been proposed as a high-resolution method for objective assessment of retinal physiology. Fast IOS in retinal photoreceptors shows a time course earlier than that of electroretinography a-wave, promising an objective marker for noninvasive ORG of early phototransduction process in retinal photoreceptors. In this article, recent observations of fast photoreceptor-IOS in animal and human retinas are summarized, and the correlation of fast photoreceptor-IOS to five steps of phototransduction process is discussed. Transient outer segment conformational change, due to inter-disc space shrinkage correlated with activation phase of phototransduction, has been disclosed as a primary source of the fast photoreceptor-IOS. Impact statement As the center of phototransduction, retinal photoreceptors are responsible for capturing and converting photon energy to bioelectric signals for following visual information processing in the retina. This article summarizes experimental observation and discusses biophysical mechanism of fast photoreceptor-intrinsic optical signal (IOS) correlated with early phase of phototransduction. Quantitative imaging of fast photoreceptor-IOS may provide objective optoretinography to advance the study and diagnosis of age-related macular degeneration, retinitis pigmentosa, diabetic retinopathy, and other eye diseases that can cause photoreceptor dysfunctions.
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Sun, Xiaoyong, Shaojing Su, Xiaojun Guo, and Junyu Wei. "A Fast and Blind Chromatic Dispersion Estimation Based on Stepwise Optimal Order Search Method in Fractional Domain." Photonics 9, no. 4 (March 28, 2022): 223. http://dx.doi.org/10.3390/photonics9040223.

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A fast and low-complexity blind chromatic dispersion (CD) estimation method is proposed by a stepwise optimal order search of fractional Fourier transform (FrFT) in coherent optical communications. The method can track the cumulative dispersion over time in future dynamic and flexible scenarios. The validity of the FrFT method is verified by analogy to the field of CD estimation from the energy concentration property of the chirp signal, and the estimation equation of the CD value is obtained by parameter transformation. Numerical simulations have been carried out in the CD range of 1600 ps/nm to 32,000 ps/nm for 28 GBaud PM-QPSK and 14 GBaud PM-16QAM signals. The results show that the proposed algorithm achieves a high CD estimation accuracy with an average estimation error of less than 50 ps/nm within the 4096 sampling points and an order search interval of 0.0001. The effects of the polarization mode dispersion, optical signal-to-noise ratio and nonlinearity on CD estimation performance are discussed. In addition, the stepwise optimal order search method can achieve the purpose of greatly reducing the computational complexity under the premise of ensuring the accuracy of CD estimation.
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Sytnik, O. "Optimal nonlinear fi ltering of stochastic processes in rescue radar." RADIOFIZIKA I ELEKTRONIKA 26, no. 3 (2021): 18–23. http://dx.doi.org/10.15407/rej2021.03.018.

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Subject and Purpose. Smoke, fog, avalanches, debris of collapsed structures and other optically opaque obstacles in both natural and man-made disasters make optical sensors useless for detecting victims. Electromagnetic waves of the decimeter range penetrate well almost all obstacles, reflect from the trapped people and return to the radar receiver. Due to the breathing and heartbeat, the human-reflected sounding signals get the Doppler phase modulation, which is an information signal. These information signals and their properties provide the subject matter for the present research with the aim to create optimal methods and algorithms of random event processing for the prompt location of survivors by rescuers. Method and Methodology. The method of stochastic analysis of the fluctuation Doppler spectra of reflected sounding signals shows that the information signals have properties of conditional Markov processes. Results. The problem of optimal nonlinear filtering of conditional Markov processes entering the radar signal processing unit has been examined closely. An optimal adaptive filter has been proposed to reduce the masking effect of interferences caused by non-stationary noises and sounding signal reflections from stationary objects. The optimality criterion is the minimum mean square error function whose current value is evaluated in real time during the filtering process as the statistics is accumulated. The filter coefficients are calculated by the recurrent, steepest descent algorithm. The real-time work is carried out through the use of fast Fourier transform algorithms. Conclusion. The structure of the optimal adaptive filter to be built into the radar signal processing unit has been developed. Real radar signals have shown that the optimal filtering during the signal processing in systems designed for detecting live people by their breathing and heartbeat facilitates the interpretation of the observed signals. Some spectra of real signals generated by human breathing and heartbeat are presented.
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YU, LI-PING, JIAN-CHEN GUO, LI-DEK CHOU, TE-LUN MA, JHENG-SYONG WU, JIANN-DER LEE, and CHIEN CHOU. "POLARIZATION-SENSITIVE OPTICAL COHERENCE TOMOGRAPHY USING A MODIFIED BALANCE DETECTOR." Journal of Innovative Optical Health Sciences 05, no. 04 (October 2012): 1250024. http://dx.doi.org/10.1142/s1793545812500241.

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In conventional polarization-sensitive optical coherence tomography (PS-OCT), phase retardation is obtained by the amplitude of P and S polarization only, and the fast axis angle is obtained by the phase difference in P and S polarizations via Hilbert transformation. In this paper, we proposed a modified PS-OCT setup in which the phase retardation and fast axis angle are simply expressed as the function of the amplitude of P and S polarization and their differential signal. Due to the common-path feature between the two channels of P and S polarization, the fluctuation in the measurement of phase retardation and fast axis angle caused by excess noise and phase noise from the laser source can be reduced by the differential signal of P and S polarization via a modified balance detector. Thus, the signal of phase retardation and fast angle axis in the deep layer of a porcine sample can be improved.
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Nelson, D. A., and L. C. Katz. "Optical imaging of brain slice preparations using voltage sensitive dyes." Proceedings, annual meeting, Electron Microscopy Society of America 53 (August 13, 1995): 810–11. http://dx.doi.org/10.1017/s0424820100140427.

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Fast responding, biological membrane-soluble voltage sensitive dyes are probes which make it possible to directly monitor the electrical activity of neuronal tissues with both high temporal and high spatial resolution. High temporal resolution is desirable because of the millisecond time scale on which neuronal events occur. High spatial resolution is desirable to better reveal the complex interactions between different regions of neural circuits.Taking full advantage of the promise of voltage sensitive dyes can be both difficult and expensive. Tissues stained with these dyes undergo very small (often less than one part in a thousand) relative changes in fluorescence in response to changes in transmembrane potential. The signal-to-noise ratio is similarly small for these responses. Finally, the responses are very fast. Most major components of the signal rise to their maximum and then disappear within 15 milliseconds of stimulation (figure 1).Because standard video cameras are inadequate for recording the very small and very fast optical signals transduced by voltage sensitive dyes, specialized detection equipment is required. This entails a high cost per pixel, often limiting the practial number of detector elements to a few hundred or even less.
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Chkalova, D. G. "Fast optical signal filtering by means of amplitude and phase operators." Journal of Physics: Conference Series 1679 (November 2020): 022092. http://dx.doi.org/10.1088/1742-6596/1679/2/022092.

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Dissertations / Theses on the topic "Fast Optical Signal"

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Awad, Ehab S. "Ultra-fast optical signal processing for digital communications using all-optical nonlinear interactions in semiconductor optical waveguides." College Park, Md. : University of Maryland, 2003. http://hdl.handle.net/1903/299.

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Thesis (Ph. D.) -- University of Maryland, College Park, 2003.
Thesis research directed by: Electrical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Pachnicke, Stephan [Verfasser]. "Fast Analytical Assessment of the Signal Quality in Transparent Optical Networks / Stephan Pachnicke." Aachen : Shaker, 2005. http://d-nb.info/1186576782/34.

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Bekker, Scott Henry. "Continuous real-time recovery of optical spectral features distorted by fast-chirped readout." Thesis, Montana State University, 2006. http://etd.lib.montana.edu/etd/2006/bekker/BekkerS0506.pdf.

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Zhao, Jun. "Fast optical signal detected in the prefrontal lobe with near-infrared spectroscopy during sleep." Diss., Columbia, Mo. : University of Missouri-Columbia, 2005. http://hdl.handle.net/10355/4237.

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Thesis (M.S.)--University of Missouri-Columbia, 2005.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (January 11, 2007) Includes bibliographical references.
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Shahoei, Hiva. "Tunable Slow and Fast Light Generation and the Applications in Microwave Photonics." Thesis, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31201.

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In this thesis, new techniques to generate slow and fast light are proposed and investigated. The use of the slow and fast light for microwave photonics applications is also investigated. This thesis consists of four parts. In the first part, the generation of slow and fast light based on fiber Bragg gratings (FBGs) is studied. Two techniques are proposed. In the first technique, slow and fast light is generated based on a linearly chirped fiber Bragg grating (LCFBG); and in the second technique, slow and fast light is generated based on a tilted fiber Bragg grating (TFBG). Theoretical analysis is performed which is verified by experiments. In the second part, the applications of FBG-based slow and fast light in microwave photonics are studied. These applications include all-optical tunable microwave frequency multiplication, tunable microwave chirped pulse generation, tunable phase shifting, tunable fractional order differentiation, and tunable microwave photonic filtering. In the third part, the generation of slow and fast light based on microring resonators (MRRs) is studied. Novel methods to obtain continuously tunable slow to fast light are proposed and experimentally demonstrated by using a silicon-on-insulator (SOI) MRR with MMI (multi-mode interference) couplers, and a high-contrast Ge-doped silica-on-silicon (SOS) MRR. In the fourth part, the applications of the MRR-based slow and fast light in microwave photonics are studied. These applications include all-optical tunable fractional order differentiation, and tunable fractional order Hilbert transformation.
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Manoochehri, Mana. "Enregistrement simultané par EEG haute résolution et signal optique rapide (fast NIRS) chez l'enfant épileptique." Thesis, Amiens, 2017. http://www.theses.fr/2017AMIE0034.

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Les pointes épileptiques intercritiques (IES) représentent une signature neuronale de l'activation transitoire hypersynchrone et excessive d'un grand ensemble de neurones corticaux hétérogènes. Elles sont considérées comme la signature de l’épileptogénicité du réseau neuronal sous-jacent. Dans cette étude, des changements sur la configuration neurale ont été observés chez des modèles animaux et humains au cours de l'IES. Pour la première fois, ces changements ont été détectés à l'aide de la spectroscopie optique rapide (FOS), qui correspond aux variations de la lumière diffusée par le tissu neural pendant l'activation. Ces chages [i.e. changements] sont associés à des mécanismes cellulaires plutôt qu'à des réponses hémodynamiques à haute résolution spatiale et temporelle. Pour étudier le mécanisme IES, une analyse simultanée multimodale des changements optiques rapides (FOS) et électriques (EEG/ECoG: temps et fréquence) a été développée chez des modèles animaux (15 rats) et humains (IES frontales,3 enfants). Pour évaluer de manière indépendante nos méthodes, un potentiel évoquant somatosensoriel et une réponse optique ont été conçus dans des modèles animaux et humains (5 volontaires sains).Les résultats suggèrent une relation entre la (dé)synchronisation et les changements optiques quel que soit le modèle épileptique. Nous avons démontré que cette approche multimodale non invasive multi-échelles (FOS, ECoG / EEG) permet d'étudier la physiopathologie de l'IES chez les patients et de mieux comprendre les mécanismes qui propulsent les neurones vers l'hypersynchronisation chez les modèles épileptiques humains et animaux
Interictal epileptic spikes (IES) represent a signature of the transient synchronous and excessive discharge of a large ensemble of cortical heterogeneous neurons and are widely accepted diagnostically as a signature of an epileptic underlying network. In this study, changes on neural configuration were observed in an animal and human models during the IES. For the first time, these changes were detected using Fast Optical Spectroscopy (FOS), which correspond to variations of scattered light from neural tissue during activation. These chages [i.e. changes] are associated with cellular mechanisms rather than hemodynamic responses with high spatial and temporal resolution. To investigate IES mechanism, a multimodal simultaneous analysis of the fast optical (FOS) and electrical (EEG/ECoG: time and frequency domain) changes was developed in both animal (15 rats) and human models (frontal IES, 3 children). To independently evaluate our methods, a control somatosensory evoked potential and optical response was designed in both animal and human models (5 healthy volunteers). The results suggest a relationship between (de)synchronization and optical changes whatever the epileptic model. This also proposed that changes in the fast optical signal which reflect changes in membrane configuration, are associated with the complex perturbations of the neuronal activation of the epileptic networks. We demonstrated that this non-invasive multiscale multimodal approach (FOS, ECoG/EEG) is suitable to study the pathophysiology of the IES in patients and shed new light on the mechanisms that propel neurons to the hypersynchronization in both animal and human epileptic models
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Petreto, Andrea. "Débruitage vidéo temps réel pour systèmes embarqués." Electronic Thesis or Diss., Sorbonne université, 2020. http://www.theses.fr/2020SORUS060.

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Pour beaucoup d'applications, la présence de bruit dans les vidéos peut être un problème majeur. Des algorithmes de débruitage existent, la plupart sont qualitativement très efficaces mais au prix d'un temps de traitement trop important pour pouvoir envisager une implémentation temps réel embarquée. D'autres méthodes, plus rares, peuvent être exécutées en temps réel mais gèrent mal les forts niveaux de bruit. Pour bon nombre d'applications, il est cependant important de conserver une bonne qualité d'images en toutes conditions avec parfois d'importantes contraintes d'embarquabilité. Dans ces travaux, nous cherchons à proposer une solution de débruitage vidéo qui permet un traitement en direct sur des systèmes embarqués. La solution proposée doit rester efficace même pour de forts niveaux de bruit. Ici, nous nous limitons à l'utilisation de CPU embarqués d'une consommation inférieure à 30W. Les travaux menés dans le cadre de cette thèse ont permis la mise en place d'une chaîne de débruitage nommée RTE-VD (Real-Time Embedded Video Denoising). RTE-VD se décompose en trois étapes : stabilisation, recalage temporel par flot optique et filtrage spatio-temporel. Sur un CPU embarqué (Jetson AGX), RTE-VD permet de traiter à une cadence de 30 images par seconde, des vidéos au format qHD (960x540 pixels). Afin de pouvoir atteindre ces performances, de nombreux compromis et optimisations ont dû être faits. Nous comparons RTE-VD à d'autres méthodes de référence de la littérature à la fois en termes de qualité du débruitage et de vitesse d'exécution. Nous montrons que RTE-VD apporte un nouveau positionnement pertinent au niveau du rapport qualité/vitesse
In many applications, noisy video can be a major problem. There are denoising methods with highly effective denoising capabilities but at the cost of a very high computational complexity. Other faster methods are limited in their applications since they does not handle high levels of noise correctly. For many applications, it is however very important to preserve a good image quality in every situation with sometimes strong embedding constraints. In this work, the goal is to propose an embedded solution for live video denoising. The method needs to remain efficient with even under high level of noise. We limit our work to embedded CPU under 30W of power consumption. This work led to a new video denoising algorithm called RTE-VD: Real-Time Embedded Video Denoising. RTE-VD is composed of 3 steps: stabilization, movement compensation by dense optical flow estimation and spatio-temporal filtering. On an embedded CPU (Jetson AGX), RTE-VD runs at 30 frame per seconds on qHD videos (960x580 pixels). In order to achieve such performance, many compromises and optimizations had to be done. We compare RTE-VD to other state-of-the-art methods in both terms of denoising capabilities and processing time. We show that RTE-VD brings a new relevant tradeoff between quality and speed
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Albuquerque, André Antunes de Carvalho. "All-optical signal processing for optical communication systems." Doctoral thesis, Universidade de Aveiro, 2017. http://hdl.handle.net/10773/23624.

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Doutoramento em Engenharia Física
O processamento ótico de sinal é uma alternativa possível para melhorar o desempenho e eficiência de sistemas de comunicações óticas, mas o seu estágio atual de desenvolvimento é ainda insuficiente para aplicações em sistemas reais. De forma a inverter esta situação, novas estratégias e pos-sibilidades para processamento ótico de sinal são aqui investigadas, com ênfase em conversão de comprimento de onda, regeneração de fase e amplificação sensível à fase em dispositivos de niobato de lítio com inversão periódica dos domínios ferroelétricos e fibras fortemente não-lineares. Um novo método para o desenho do perfil de inversão dos domínios fer¬roelétricos nos dispositivos de niobato de lítio de acordo com um espetro de conversão alvo é investigado nesta tese. O método proposto é validado numericamente e através da produção de um dispositivo real com largura de banda de conversão de 400 GHz. O dispositivo produzido é utilizado para conversão de onda multicanal de oito sinais modulados em fase, com a possibilidade adicional de sintonizar o comprimento de onda dos sinais con¬vertidos. Observa-se a existência de um compromisso entre elevada largura de banda de conversão e eficiência do dispositivo. São também investigadas nesta tese conversão e permuta de comprimento de onda tolerantes ao ruído de fase adicionado por fontes de bombeamento. Demonstra-se neste trabalho que a utilização de fontes de bombeamento coerentes permite evitar a adição de ruído de fase aos sinais convertidos. Nesta tese é também analisada analítica e numericamente amplificação sensível a fase baseada em dispositivos de niobato de lítio com inversão periódica dos domínios ferroelétricos para configurações de amplificadores de um, dois ou quatro modos. É ainda avaliada a possibilidade de ge¬rar ondas correlacionadas e de realizar amplificação sensível a fase num único dispositivo com propagação bidirecional. Com base neste esquema, demonstra-se regeneração de fase de sinais modulados em fase, porém com ganho limitado devido à baixa eficiência de conversão dos dispositivos e com desempenho afetado por instabilidades térmicas e foto refrativas. Mo¬tivado por estas limitações, demonstra-se amplificação de elevado ganho num amplificador sensível à fase de quatro modos, construído com uma fibra fortemente não-linear em vez de um dispositivo de niobato de lítio. Por fim, é efetuada uma análise numérica do impacto de utilizar amplifica¬dores sensíveis à fase em vez de amplificadores de fibra dopada com érbio no alcance em transmissão ponto a ponto de sinais e na amplificação e regeneração em redes óticas. Demonstra-se que amplificadores sensíveis à fase são mais vantajosos para formatos de modulação avançados e siste¬mas compostos por ligações óticas longas. As simulações assumem mode¬los simplificados para o ganho e ruído dos amplificadores, bem como uma versão modificada do modelo de ruído Gaussiano para estimar a potência das distorções não-lineares em sistemas com compensação total da dispersão cromática no final de cada segmento de fibra entre amplificadores.
All-optical signal processing techniques are a possible way to improve the performance and efficiency of optical communication systems, but the cur¬rent stage of development of such techniques is still unsatisfactory for real- world implementation. In order to invert this situation, new strategies and possibilities for all-optical signal processing are investigated here, with a particular focus on wavelength conversion, phase regeneration and phase- sensitive amplification in periodically poled lithium niobate waveguides and highly nonlinear fibers. A new and flexible method to design the poling pattern of periodically poled lithium niobate devices according to a target conversion spectrum is inves¬tigated in this work. The proposed method is validated through numerical simulations and by producing a real device with broad conversion bandwidth of 400 GHz. The device is then used for multichannel wavelength conversion of eight phase-modulated signals, with the additional possibility to tune the wavelength of the converted signals. A trade-off between high conversion bandwidth and conversion efficiency is observed. Advanced wavelength conversion and wavelength exchange tolerant to the phase noise added by the pump lasers are also investigated. It is shown that the additional phase noise transferred to the converted signals is eliminated by using coherent pumps, generated from the same light source. Phase-sensitive amplification based on periodically poled lithium niobate devices is also investigated in this thesis by numerically comparing the gain properties for one-, two- and four-mode configurations. The possibility to si¬multaneously generate correlated waves and observe phase-sensitive amplifi¬cation in a single device with bidirectional propagation is also demonstrated. Using such scheme,"black-box" phase regeneration of phase-encoded sig¬nals is experimentally demonstrated, albeit with limited net gain due to the low conversion efficiency of the device, and the limited reliability due to thermal and photorefractive instabilities. Motivated by such limitations, high-gain amplification in a four-mode phase-sensitive amplifier built with a highly nonlinear fiber instead of a periodically poled lithium niobate is demonstrated. Finally, the impact of using phase-sensitive amplifiers instead of common erbium-doped fiber amplifiers on the reach in point-to-point transmission and on the amplification and regeneration requirements in optical transport networks is numerically investigated. The calculations show that phase- sensitive amplifiers are particularly advantageous when considering high- order modulation formats and for transport networks comprised by long links. The numerical simulations are performed using simplified models for the gain and noise properties of the amplifiers, and a modified enhanced Gaussian noise model to estimate the power of the nonlinear distortions in systems with full dispersion compensation at the end of each span of fiber.
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Rocha, Peterson 1977. "Degradação de sinais com modulação NRZ-DQPSK e 16-QAM em enlaces ponto a ponto com amplificadores ópticos a semicondutor = NRZ-DQPSK and 16-QAM signal degradation in fiber links with semiconductor optical amplifiers." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/260643.

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Orientador: Evandro Conforti
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
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Resumo: Modulações ópticas avançadas como DQPSK e QAM tem sido escolhidas por serem formatos multiniveis (dois bits ou mais por símbolo), aumentando a eficiência espectral de sistemas ópticos. Entretanto, o amplificador óptico a semicondutor (SOA) indicado principalmente para aplicações de media distancia (da ordem de 20 km), pode degradar o sinal DQPSK e QAM. Sistemas de fase modulada (como o DQPSK) são afetados principalmente por SPM e XPM, devido ao ruído de fase não-linear adicionado a fase óptica do sinal. Visando analisar estes problemas, apresenta-se um estudo sobre os sinais NRZ-DQPSK e 16-QAM amplificados pelo SOA, bem como outros fatores que degradam tais sistemas, através de simulações com os softwares comerciais OptiSystem e VPItransmissionMaker. Nas simulações, resultados foram obtidos estando em acordo com a teoria e em acordo com o capitulo 3. Para o sistema DQPSK, o SOA degradou o sinal em todos cenários propostos para avaliar o sistema. O sinal NRZ-DQPSK apresentou maior penalidade quando o ganho do SOA foi de 20 dB. Efeitos não-lineares juntamente com a dispersão cromática limitam fortemente a distancia do enlace, e ao compensar a dispersão cromática no enlace com maior penalidade em 56 Gbps, o sinal NRZ-DQPSK pode trafegar por uma distancia 10 vezes maior (de 5 km para 50 km) com uma BER de 10-12. Para o sistema QAM, o sinal foi penalizado pelo SOA em todos os casos, e utilizando o SOA com ganho grampeado, os efeitos não-lineares foram minimizados, melhorando substancialmente o desempenho. Compensando a dispersão cromática e usando o SOA com ganho grampeado para o caso com maior penalidade, o sinal 16-QAM viajou a uma distancia 16 vezes maior (3 km e 50 km)
Abstract: High spectral efficiency is being achieved in modern optical fiber systems using multilevel optical modulation formats such us DQPSK and QAM, with more than one bit per symbol. However, amplifying devices such as the semiconductor optical amplifier (SOA) can degrade the DQPSK signal. In recent years SOAs have gained much attention (mainly in medium distance links, around 20 km) due to non-linear and fast switching potential applications (wavelength conversion, 3R regeneration, optical packet switching, etc.). In addition, the SOA under gain saturation further enhance deleterious nonlinear effects such as SPM, XGM, FWM, XPM. Phase modulated systems as DQPSK are affected mainly by SPM and XPM due to the nonlinear phase noise added to the controlled phase of the optical modulated signal. This work presents a study on the NRZ-DQPSK and 16-QAM signals when amplified by SOAs, analyzing the main factors degrading such systems through simulations using commercial OptiSystem and VPItransmissionMaker software. SOA showed degradation effects over DQPSK, with larger penalties to NRZ signals and optical gain over 20 dB. Non-linear effects and chromatic dispersion impose a maximum distance limit. In dispersion compensated links, 10 fold distances are achieved in relation to standard fibers (5 to 50 km) with BER= 10-12. For 16 QAM, the penalties are still high. However, gain clamped SOAs have better performance with a 16 fold distance increase (3 km to 50 km)
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Ribeiro, Vitor Bedotti. "Filtros digitais para recepção coerente em 112 Gb/s de sinais ópticos com modulação QPSK e multiplexação por divisão em polarização." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/261928.

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Orientadores: Aldário Chrestani Bordonalli, Júlio César Rodrigues Fernandes de Oliveira
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
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Resumo: As mudanças nos padrões de tráfego na internet forçam a constante evolução das redes ópticas, que, por serem sistemas com grande capacidade e se estenderam por milhares de quilômetros, são a principal aposta para suprir a demanda por banda. A solução adotada foi aumentar a eficiência espectral da transmissão, por meio do uso de formatos de modulação de alta ordem, como o PSK e o QAM, da detecção coerente e da multiplexação em polarização. Nessa dissertação, os conceitos de uma transmissão coerente digital e os principais algoritmos para a recepção e recuperação de sinal são apresentados, considerando o formato de modulação DP-QPSK com taxa agregada de 112 Gb/s. É proposto, também, um método de adaptação de ganho para o algoritmo de módulo constante (CMA), que acelera a convergência e torna a rotina que rastreia as mudanças no estado de polarização do sinal óptico mais rápido e robusto. Os algoritmos para cada funcionalidade foram testados individualmente em simulação. O melhor conjunto de algoritmos é analisado e configurações experimentais em back-to-back com carregamento de ruído ASE, em anel de recirculação óptico de 225 km com 80 canais DWDM e, também, em transmissão pela Rede Experimental de Alta Velocidade GIGA no trecho Campinas - São Paulo - Campinas. Para a configuração em back-to-back, o limite do sistema foi de 10,5 dB de OSNR. No anel de recirculação, foi possível a transmissão de 80 canais a 112 Gb/s, totalizando 8,96 Tbit/s por 2925 km e ocupando 50 GHz de banda, ou por 2475 km e ocupando 25 GHz. Na rede GIGA, o sistema se mostrou estável, com taxa de erro de bits bem inferior ao limite por mais de 3 horas de análise. O método de adaptação de ganho proposto conseguiu acompanhar mais de 20 Mrad/s e 3 Mrad/s de variação angular no estado de polarização para 34 dB e 15 dB de OSNR, respectivamente, enquanto o CMA sem adaptação de ganho falha a 10 Mrad/s e 1,5 Mrad/s nas mesmas condições. Os resultados demonstram a eficácia e a estabilidade dos algoritmos e a capacidade de recuperação do sinal em simulação, em experimentos laboratoriais ou em campo
Abstract: The changes in traffic patterns due to the Internet force the constant evolution of optical networks. These systems, designed to deliver high transmission capacity over thousands of kilometers, are the key solution to meet the demand for bandwidth. The recent tendency to provide wider bandwidth without changing the infrastructure already deployed has been to increase the spectral efficiency of transmission by using high order modulation formats, such as PSK and QAM, and employment coherent detection along with polarization multiplexing. In this work the concepts of optical digital coherent systems and the main algorithms for signal reception and recovery are presented, considering QPSK modulation format and polarization multiplexing (DP-QPSK) at 112 Gb/s. It is also proposed a method for adaptive adjustment of the constant modulus algorithm (CMA) gain, which accelerates the convergence and makes the algorithm faster and more robust to changes in the state of polarization of the optical signal. The algorithms for each function were tested individually in a simulation setup. The best set of algorithms were then obtained and applied in the receiver end of different experimental setups: back-to-back with ASE noise loading; 225-km optical recirculation loop with 80 DWDM channels; and a field transmission over part of the high-capacity experimental network GIGA (Campinas - São Paulo - Campinas). For the back-to-back setup, the system limit was achieved at 10.5 dB of OSNR. For the recirculation loop, it was possible to transmit up to 80 channels at 112 Gb/s, or 8.96 Tbit/s for overall system capacity, over 2925 km, considering 50-GHz bandwidth signal, or 2475 km for 25-GHz bandwidth signal. For the GIGA network, the system was stable with bit error rate well below the FEC threshold during the 3-hour analysis. The gain adaptation method proposed was able to track over 20 Mrad/s and 3 Mrad/s of angular rotation rate in the state of polarization for OSNRs of 34 dB and 15 dB, respectively, while the CMA without gain adaptation fails to track frequencies above 10 Mrad/s and 1.5 Mrad/s in the same conditions. The results show that the set of algorithms is effective, stable and capable of recovering the signal during simulation, laboratory experiments or field trials
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Books on the topic "Fast Optical Signal"

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John, Schewel, and Society of Photo-optical Instrumentation Engineers., eds. Field programmable gate arrays (FPGAs) for fast board development and reconfigurable computing: 25-26 October, 1995, Philadelphia, Pennsylvania. Bellingham, Wash: SPIE, 1995.

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United States. National Aeronautics and Space Administration., ed. Feasibility study, software design, layout and simulation of a two-dimensional fast Fourier transform machine for use in optical array interferometry: Final report on the NASA FTT project covering the period June 1, 1989 to September 1, 1994. [Washington, DC: National Aeronautics and Space Administration, 1994.

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Ishikawa, Hiroshi. Ultra-Fast All-Optical Signal Processing Devices. Wiley & Sons, Limited, John, 2008.

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Book chapters on the topic "Fast Optical Signal"

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Navarro, Rafael, and Antonio Tabernero. "Gaussian Wavelet Transform: Two Alternative Fast Implementations for Images." In Optical Signal Processing, 67–82. Boston, MA: Springer US, 1991. http://dx.doi.org/10.1007/978-1-4615-4006-9_8.

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Medvedev, A. V., J. M. Kainerstorfer, S. V. Borisov, and J. VanMeter. "Fast optical signal in the prefrontal cortex correlates with EEG." In XII Mediterranean Conference on Medical and Biological Engineering and Computing 2010, 631–34. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-13039-7_159.

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Syré, Frank, Hellmuth Obrig, Jens Steinbrink, Matthias Kohl, Rüdiger Wenzel, and Arno Villringer. "Are VEP Correlated Fast Optical Signals Detectable in the Human Adult by Non-Invasive Nearinfrared Spectroscopy (NIRS)?" In Oxygen Transport to Tissue XXIV, 421–31. Boston, MA: Springer US, 2003. http://dx.doi.org/10.1007/978-1-4615-0075-9_39.

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Lobbe, Alexander. "Deep Learning for the Benes Filter." In Mathematics of Planet Earth, 195–210. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-18988-3_12.

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AbstractThe filtering problem is concerned with the optimal estimation of a hidden state given partial and noisy observations. Filtering is extensively studied in the theoretical and applied mathematical literature. One of the central challenges in filtering today is the numerical approximation of the optimal filter. Here, accurate and fast methods are actively sought after, especially for such high-dimensional settings as numerical weather prediction, for example. In this paper we present a brief study of a new numerical method based on the mesh-free neural network representation of the density of the solution of the filtering problem achieved by deep learning. Based on the classical SPDE splitting method, our algorithm includes a recursive normalisation procedure to recover the normalised conditional distribution of the signal process. The present work uses the Benes model as a benchmark. The Benes filter is a well-known continuous-time stochastic filtering model in one dimension that has the advantage of being explicitly solvable. Within the analytically tractable setting of the Benes filter, we discuss the role of nonlinearity in the filtering model equations for the choice of the domain of the neural network. Further, we present the first study of the neural network method with an adaptive domain for the Benes model.
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Li, Xinwan, Zehua Hong, Shuguang Li, and Jianping Che. "Digitally Fast Programmable Optical Signal Processing Devices." In Optical Fiber New Developments. InTech, 2009. http://dx.doi.org/10.5772/7556.

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E. Abejide, Adebayo, Madhava R. Kota, Sushma Pandey, Oluyomi Aboderin, Cátia Pinho, Mário Lima, and António Teixeira. "Direct and External Hybrid Modulation Approaches for Access Networks." In Network-on-Chip [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.96085.

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The demand for low-cost high-speed transmission is a major challenge for 5G future networks. To meet this optical communication demand, holistic and painstaking approaches are required in designing a simplified system model. Since the demands for high bandwidth are growing at unprecedented speed as we approach the Zettabyte era, it is crucial to minimize chromatic dispersion (CD) associated to high bit-rate signals. Mitigating CD electronically comes at high cost which may not be compatible with 5G. Photonic Integrated Circuit (PIC) as an enabler for fast speed optical transmission is still undergoing its growth stage and its major speed and efficiency have not yet been attained. However, proper and right combination of components and approaches can potentiate this technology in a more cost-efficient way. Hybrid modulation (HM)-PIC presents a simplified approach in terms of cost and efficiency for 5G networks. Hybridization of existing modulation components and approaches in PIC can enhance the generation of high bit-rate signals without the need for electrical CD compensation. A detailed study of hybrid multilevel signal modulation concept as a valuable solution for Data Centers (DC) high data-rate signals and next-generation Passive Optical Networks (PONs) is proposed.
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Ben, Y., and B. I. Lembrikov. "New Approach to Ultra-Fast All-Optical Signal Processing Based on Quantum Dot Devices." In Semiconductor Technologies. InTech, 2010. http://dx.doi.org/10.5772/8567.

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Gratton, Gabriele, and Monica Fabiani. "Fast Optical Signals." In In Vivo Optical Imaging of Brain Function, Second Edition, 435–60. CRC Press, 2009. http://dx.doi.org/10.1201/9781420076851.ch15.

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Gratton, Gabriele, and Monica Fabiani. "Fast Optical Signals." In In Vivo Optical Imaging of Brain Function. CRC Press, 2002. http://dx.doi.org/10.1201/9781420038491.ch9.

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Chiarini, Marco, Alberto Parini, and Gian Giuseppe Bentini. "Integrated Optics and Photonics for Optical Interferometric Sensing." In Optical Interferometry - A Multidisciplinary Technique in Science and Engineering [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.103770.

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Integrated optics (IO) microsystems, based on guided wave and photonics structures, can find interesting developments for optical interferometric analysis in sensing applications. In fact, IO interferometric microsystems can act as transducers of the information carried on by an optical signal and originated along the signal optical path. In addition, the application of Integrated Optics and Photonics techniques, allow producing very small size and reduced power consumption instrumentation. These features explain the reason why the IO microsystems for interferometric analytics know an increasing interest in many areas such as Astrophysics, Environment, Biosciences, Space and Earth Exploration, Safety and Security. This chapter starts by synthetically describing the basics of the main analytical techniques covered by IO micro-devices. A discussion of the integrated micro-device fabrication procedures, with an analysis of the implied performance limitations, follows. Finally, a description of new generation optical interferometric microsystems, applied to different scientific and technical areas, completes the chapter.
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Conference papers on the topic "Fast Optical Signal"

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Wiatrek, Andrzej, Ronny Henker, Stefan Preußler, and Thomas Schneider. "1.4 Bit Delay and Pulse Compression Based on Brillouin Optical Signal Processing." In Slow and Fast Light. Washington, D.C.: OSA, 2009. http://dx.doi.org/10.1364/sl.2009.smc4.

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Wu, F. M., P. C. Peng, R. L. Lan, J. H. Chen, C. T. Lin, and S. Chi. "Tunable Optical Delay Line using Semiconductor Laser for 10 Gbit/s Data Signal." In Slow and Fast Light. Washington, D.C.: OSA, 2009. http://dx.doi.org/10.1364/sl.2009.jtub28.

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Balan, Radu, Bernhard G. Bodmann, Peter G. Casazza, and Dan Edidin. "Fast algorithms for signal reconstruction without phase." In Optical Engineering + Applications, edited by Dimitri Van De Ville, Vivek K. Goyal, and Manos Papadakis. SPIE, 2007. http://dx.doi.org/10.1117/12.731117.

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Chin, Sanghoon, and Luc Thévenaz. "Large multi Gbit/s delays generated in an all-optical tunable delay line preserving wavelength and signal bandwidth." In Slow and Fast Light. Washington, D.C.: OSA, 2008. http://dx.doi.org/10.1364/sl.2008.smc3.

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Oxenlowe, L. K., M. Galili, H. Hu, H. Ji, E. Palushani, J. L. Areal, J. Xu, H. C. H. Mulvad, A. T. Clausen, and P. Jeppesen. "Serial optical communications and ultra-fast optical signal processing of Tbit/s data signals." In 2010 IEEE Topical Meeting on Microwave Photonics (MWP 2010). IEEE, 2010. http://dx.doi.org/10.1109/mwp.2010.5664119.

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Konishi, Tsuyoshi. "Ultra-fast Optical Signal Processing using Optical Time-Space Conversion." In 2007 Conference on Lasers and Electro-Optics - Pacific Rim. IEEE, 2007. http://dx.doi.org/10.1109/cleopr.2007.4391677.

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Liu, Y., E. Tangdiongga, Z. Li, S. Zhang, M. T. Hill, J. H. C. van Zantvoort, F. M. Huijskens, et al. "Ultra-fast all-optical signal processing: toward optical packet switching." In Asia-Pacific Optical Communications, edited by Chang Soo Park, Shizhong Xie, Curtis R. Menyuk, and Ken-ichi Kitayama. SPIE, 2006. http://dx.doi.org/10.1117/12.687147.

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Oxenlowe, Leif Katsuo. "Ultra-broadband and Ultra-fast Optical Signal Processing." In Signal Processing in Photonic Communications. Washington, D.C.: OSA, 2015. http://dx.doi.org/10.1364/sppcom.2015.spt2e.2.

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Belovolov, M. I., E. M. Dianov, V. I. Karpov, V. N. Protopopov, and V. N. Serkin. "Fiber Optic Dynamic Memory For Fast Signal Processing And Optical Computing." In Optical Computing '88, edited by Pierre H. Chavel, Joseph W. Goodman, and Gerard Roblin. SPIE, 1989. http://dx.doi.org/10.1117/12.947878.

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Mi, Tiebin, and Shidong Li. "Fast null space tuning algorithms with feedbacks for sparse signal recovery." In SPIE Optical Engineering + Applications, edited by Dimitri Van De Ville, Vivek K. Goyal, and Manos Papadakis. SPIE, 2013. http://dx.doi.org/10.1117/12.2024819.

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Reports on the topic "Fast Optical Signal"

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Brady, David J., James J. Coleman, and Kenneth G. Purchase. Ultra-Fast Optical Signal Encoding and Analysis for Communications and Data Fusion Networks. Fort Belvoir, VA: Defense Technical Information Center, May 2000. http://dx.doi.org/10.21236/ada377846.

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Kuznetsov, Victor, Vladislav Litvinenko, Egor Bykov, and Vadim Lukin. A program for determining the area of the object entering the IR sensor grid, as well as determining the dynamic characteristics. Science and Innovation Center Publishing House, April 2021. http://dx.doi.org/10.12731/bykov.0415.15042021.

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Currently, to evaluate the dynamic characteristics of objects, quite a large number of devices are used in the form of chronographs, which consist of various optical, thermal and laser sensors. Among the problems of these devices, the following can be distinguished: the lack of recording of the received data; the inaccessibility of taking into account the trajectory of the object flying in the sensor area, as well as taking into consideration the trajectory of the object during the approach to the device frame. The signal received from the infrared sensors is recorded in a separate document in txt format, in the form of a table. When you turn to the document, data is read from the current position of the input data stream in the specified list by an argument in accordance with the given condition. As a result of reading the data, it forms an array that includes N number of columns. The array is constructed in a such way that the first column includes time values, and columns 2...N- the value of voltage . The algorithm uses cycles that perform the function of deleting array rows where there is a fact of exceeding the threshold value in more than two columns, as well as rows where the threshold level was not exceeded. The modified array is converted into two new arrays, each of which includes data from different sensor frames. An array with the coordinates of the centers of the sensor operation zones was created to apply the Pythagorean theorem in three-dimensional space, which is necessary for calculating the exact distance between the zones. The time is determined by the difference in the response of the first and second sensor frames. Knowing the path and time, we are able to calculate the exact speed of the object. For visualization, the oscillograms of each sensor channel were displayed, and a chronograph model was created. The chronograph model highlights in purple the area where the threshold has been exceeded.
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Mizrach, Amos, Sydney L. Spahr, Ephraim Maltz, Michael R. Murphy, Zeev Schmilovitch, Jan E. Novakofski, Uri M. Peiper, et al. Ultrasonic Body Condition Measurements for Computerized Dairy Management Systems. United States Department of Agriculture, 1993. http://dx.doi.org/10.32747/1993.7568109.bard.

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The body condition (BC) score is recognized in the dairy industry as an essential tool for managing the energy reserves of the dairy cow, which is essential for sustaining optimal and efficient production over several lactations. The current use of BC scoring depends on the accuracy of subjective visual estimates, and this limits its kusefulness as a management aid in the dairy industry. A measuring tool that would frequently provide objective data on the cow's body reserves would be a major contribution to efficient dairy herd management. Ultrasonic sensors have the potential to be developed into an efficient BC measuring device, and the experimental use of such sensors for subcutaneous fat thickness (SDFT) estimates, as an indication for BC in beef cattle, supports this assumption. The purposes of this project were: 1. To compare visual BC scoring and ultrasonic fat thickness with on-line automated body weight (BW) measurements as monitors of nutritional adequacy of dairy cows at various stages of lactation. 2. To determine the effects of variation in digestive fill in early and late lactation on the accuracy of body weight measurements in lactating cows. 3. To modify an existing ultrasonic system and develop a specialized, low-cost sensor for repeatable determination of body condition scores by users with minimal training and skill. 4. To develop a standard for the assignment of body condition scores based on ultrasonic measurements of subdermal fat thickness. The procedure to execute these objectives involved: 1. Frequent measurement of BW, milk yield (MY), BC (visually scored) and subdermal fat thickness ultrasonically measured of dairy cows, and data analysis on average and individual basis. 2. Testing and selection of an appropriate special-purpose sensor, finding an optimum body location for working an ultrasonic measurement, prcessing the signals obtained, and correlating the resulting measurements with performance responses in lactating cows. Linking the ultrasonic signals to BC scores, and developing a BC scoring data acquisition system are the first steps towards fulfilling the necessary requirements for incorporating this device into an existing dairy herd management system, in order to provide the industry with a powerful managment tool. From the results obtained we could conclude that: 1. BC does not correlate with BW changes during all stages of lactation, although in general terms it does. These results were confirmed by individual cow BW and BC data obtained during the course of lactation, that were supported by individual objective ultrasonic measurement of SDFT. 2. BW changes reflect energy metabolism reliably ony after peak milk yield; early in lactation, a decrease in BW expresses mobilization of body reserves only qualitatively, and not quantitatively. 3. Gastrointestinal content increases throughout the whole period during which dry matter intake (DMI) increases. The drastic increase very early in lactation prevents the use of BW changes as a basis for quantitative estimatio of energy meatabolism; at this stage of lactation, konly a BC score or any other direct measurements willl provide a quantitative estimate of energy metabolism. 4. Ultrasonic measurements of subdermal fat thickness can be used to quantify changes that correlate with the actual condition of the cow, as assessed by performance and the traditional way of scoring. 5. To find the best site on the cow's body at which to obtain responses to BC and its changes in the course of lactation, additional sites have to be examined. From the present study, it seems that the sites between ribs 12 and 13 have the potential for this purpose. 6. The use of templates made it easier to repeat measurements at a desired site and spot. However, the convenient easy-to-handle way to standardize the measurement, described in this study, koffers scope for improvement. 7. The RF peak values of the A-mode are better indicators of the location of fat layer borders than image analysis, from the point of view of future commercial development. 8. The distances between the RF peaks of the A-mode can be automatically measured by suitable software, for future commercial development. 9. Proper analysis of daily body weight and milk yield data can provide the necessary information on body condition changes during lactation, until a direct BC measurement device is developed. 10. In any case, at least one visual BC assessment has to be done, preferably immediately after calving, for calibration purposes.
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