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Artykuły w czasopismach na temat "Fiber Bragg Grating Pulse Recorder"
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Umesh, Sharath, Srivani Padma, Shikha Ambastha, Anand Kalegowda i Sundarrajan Asokan. "Pulse transit time differential measurement by fiber Bragg grating pulse recorder". Journal of Biomedical Optics 20, nr 5 (28.05.2015): 057005. http://dx.doi.org/10.1117/1.jbo.20.5.057005.
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Sharath, U., C. Shwetha, K. Anand i S. Asokan. "Radial arterial compliance measurement by fiber Bragg grating pulse recorder". Journal of Human Hypertension 28, nr 12 (19.06.2014): 736–42. http://dx.doi.org/10.1038/jhh.2014.45.
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Radzi, Nurnazifah M., Amirah A. Latif, Mohammad F. Ismail, Josephine Y. C. Liew, Noor A. Awang, Han K. Lee, Fauzan Ahmad, Siti F. Norizan i Harith Ahmad. "Tunable Spacing Dual-Wavelength Q-Switched Fiber Laser Based on Tunable FBG Device". Photonics 8, nr 12 (23.11.2021): 524. http://dx.doi.org/10.3390/photonics8120524.
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A tunable spacing dual-wavelength Q-switched fiber laser is experimentally demonstrated based on a fiber Bragg grating tunable device incorporated in an erbium-doped fiber laser (EDFL). The system utilizes two identical fiber Bragg gratings (FBGs) at 1547.1 nm origin to enable two laser lines operation. The wavelength separations between two laser lines are controlled by fixing one of the FBGs while applying mechanical stretch and compression to the other one, using a fiber Bragg grating tunable device. The seven steps of wavelength spacing could be tuned from 0.3344 to 0.0469 nm spacing. Pulse characteristics for both close and wide spacing of dual-wavelength Q-switched fiber laser are successfully being recorded. The findings demonstrate the latest idea of dual-wavelength fiber laser based on FBG tunable device, which offers a wide range of future applications.
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Kulchin, Yuriy N., Anatoly M. Shalagin, Oleg B. Vitrik, Sergey A. Babin, Anton V. Dyshlyuk i Alexander A. Vlasov. "Differential Reflectometry of Fiber Bragg Gratings". Key Engineering Materials 437 (maj 2010): 324–28. http://dx.doi.org/10.4028/www.scientific.net/kem.437.324.
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A reflectometric approach is proposed for interrogation of multiple fiber Bragg grating (FBG) sensors recorded in a single fiber optic line, based on the differential registration FBGs’ response to a short probing laser pulse using conventional OTDR. A special optical layout has been developed allowing transformation of FBG’s spectrally modulated signals into intensity modulated signals and at the same time eliminating the susceptibility of the system to light power fluctuations. Threshold sensitivity of the method amounted to ~50 μstrain within the measurement range of ~4000 μstrain. The maximum number of FBGs interrogated by the proposed technique is estimated at several hundred, which by far surpasses the requirements of most practical applications. Due to its simplicity, efficiency and usage of conventional OTDR equipment the proposed FBG interrogation technique can find a wide range of applications, in particular in structural health monitoring.
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Acharya, Anirudh R., Bram Vandekerckhove, Lars Emil Larsen, Jean Delbeke, Wytse J. Wadman, Kristl Vonck, Evelien Carette i in. "In vivo blue light illumination for optogenetic inhibition: effect on local temperature and excitability of the rat hippocampus". Journal of Neural Engineering 18, nr 6 (1.12.2021): 066038. http://dx.doi.org/10.1088/1741-2552/ac3ef4.
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Abstract Objective. The blue light-activated inhibitory opsin, stGtACR2, is gaining prominence as a neuromodulatory tool due its ability to shunt-inhibit neurons and is being frequently used in in vivo experimentation. However, experiments involving stGtACR2 use longer durations of blue light pulses, which inadvertently heat up the local brain tissue and confound experimental results. Therefore, the heating effects of illumination parameters used for in vivo optogenetic inhibition must be evaluated. Approach. To assess blue light (473 nm)-induced heating of the brain, we used a computational model as well as direct temperature measurements using a fiber Bragg grating (FBG). The effects of different light power densities (LPDs) and pulse durations on evoked potentials (EP) recorded from dentate gyrus were assessed. For opsin-negative rats, LPDs between 127 and 636 mW mm−2 and pulse durations between 20 and 5120 ms were tested while for stGtACR2 expressing rats, LPD of 127 mW mm−2 and pulse durations between 20 and 640 ms were tested. Main results. Increasing LPDs and pulse durations logarithmically increased the peak temperature and significantly decreased the population spike (PS) amplitude and latencies of EPs. For a pulse duration of 5120 ms, the tissue temperature increased by 0.6 °C–3.4 °C. All tested LPDs decreased the PS amplitude in opsin-negative rats, but 127 mW mm−2 had comparatively minimal effects and a significant effect of increasing light pulse duration was seen from 320 ms and beyond. This corresponded with an average temperature increase of 0.2 °C–1.1 °C at the recorded site. Compared to opsin-negative rats, illumination in stGtACR2-expressing rats resulted in much greater inhibition of EPs. Significance. Our study demonstrates that light-induced heating of the brain can be accurately measured in vivo using FBG sensors. Such light-induced heating alone can affect neuronal excitability. Useful neuromodulation by the activation of stGtACR2 is still possible while minimizing thermal effects.
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Padma, Srivani, Sharath Umesh, Talabattula Srinivas i Sundarrajan Asokan. "Carotid Arterial Pulse Waveform Measurements Using Fiber Bragg Grating Pulse Probe". IEEE Journal of Biomedical and Health Informatics 22, nr 5 (wrzesień 2018): 1415–20. http://dx.doi.org/10.1109/jbhi.2017.2765701.
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Wang, Ming-Xiao, Ping-Xue Li, Yang-Tao Xu, Yun-Chen Zhu, Shun Li i Chuan-Fei Yao. "An All-Fiberized Chirped Pulse Amplification System Based on Chirped Fiber Bragg Grating Stretcher and Compressor". Chinese Physics Letters 39, nr 2 (1.02.2022): 024201. http://dx.doi.org/10.1088/0256-307x/39/2/024201.
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We report an all-fiberized chirped pulse amplification system without any bulk devices. The stretcher and compressor are chirped fiber Bragg gratings inscribed in a 6/125 μm single-mode fiber and a 30/250 μm large-mode-area fiber. The fabrication system of chirped fiber Bragg gratings was designed and built by ourselves. The width of the linear exposure spot was controlled according to the different fiber sizes to improve the fabrication quality, and the parameters of chirped fiber Bragg gratings were fine-tuned during the fabrication to achieve the overall system’s spectral matching. Two fiber circulators with the same fiber sizes as the chirped fiber Bragg gratings were employed to auxiliarily achieve the pulse stretching and compression. The dispersion accumulations provided by the stretcher and compressor are 129.8 ps and 90.8 ps. The power amplifiers were composed of the two-stage 10/130 μm fiber pre-amplifier and the 30/250 μm fiber main amplifier. The proposed chirped pulse amplification system with no spatial light is the true sense of an all-fiberized chirped pulse amplification structure and shows the main trend in development of ultrashort pulse fiber lasers.
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Longhi, Stefano. "Klein Tunneling of Light in Fiber Bragg Gratings". Physics Research International 2010 (31.08.2010): 1–5. http://dx.doi.org/10.1155/2010/645106.
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A photonic analogue of Klein tunneling (KT), that is, of the exotic property of relativistic electrons to pass a large repulsive and sharp potential step, is proposed for pulse propagation in a nonuniform fiber Bragg grating with an embedded chirped region. KT can be simply observed as the opening of a transmission window inside the grating stop band, provided that the impressed chirp is realized over a length of the order of the analogue of the Compton wavelength.
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Chen, Xinxin, Enbo Wang, Yali Jiang, Hui Zhan, Hongwei Li, Guohui Lyu i Shuli Sun. "Generalized Resonance Sensor Based on Fiber Bragg Grating". Photonics 8, nr 5 (6.05.2021): 156. http://dx.doi.org/10.3390/photonics8050156.
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In response to the difficulty of weak detection of early bearing damage, resonance demodulation technology and the principle of fiber Bragg grating sensing strain were combined to design a fiber Bragg grating generalized resonance sensor, which can extract the weak pulse signal of weak detection of early bearing’s early damage from rolling bearing. First, a principle of resonance dynamics of second-order mechanical systems based on fiber Bragg grating and generalized resonance principles is proposed. Second, the basic structure of the sensor is designed. Then, ANSYS finite element simulation is used to analyze the natural frequency of the sensor. Finally, the natural frequency value of the sensor was obtained through experiments. The experimental results of proof-of-principle show that the experimental results are consistent with the theoretical predictions. The theoretical model is accurate, which verifies the feasibility of the sensor.
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Xu, Qinfeng, Qiong Liu, Qing Ye, Zhengqing Pan, Haiwen Cai, Ronghui Qu i Zujie Fang. "Millimeter-wave pulse generation based on pulse reshaping using superstructure fiber Bragg grating". Optik 121, nr 20 (październik 2010): 1853–58. http://dx.doi.org/10.1016/j.ijleo.2009.05.004.
Pełny tekst źródłaRozprawy doktorskie na temat "Fiber Bragg Grating Pulse Recorder"
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Liu, Weilin. "Real-time Interrogation of Fiber Bragg Grating Sensors Based on Chirped Pulse Compression". Thèse, Université d'Ottawa / University of Ottawa, 2011. http://hdl.handle.net/10393/20289.
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Theoretical and experimental studies of real-time interrogation of fiber Bragg grating (FBG) sensors based on chirped pulse compression with increased interrogation resolution and signal-to-noise ratio are presented. Two interrogation systems are proposed in this thesis.
In the first interrogation system, a linearly chirped FBG (LCFBG) is employed as the sensing element. By incorporating the LCFBG in an optical interferometer as the sensor encoding system, employing wavelength-to-time mapping and chirped pulse compression technique, the correlation of output microwave waveform with a chirped reference waveform would provide an interrogation result with high speed and high resolution. The proposed system can provide an interrogation resolution as high as 0.25 μ at a speed of 48.6 MHz. The second interrogation system is designed to achieve simultaneous measurement of strain and temperature. In this system, a high-birefringence LCFBG (Hi-Bi LCFBG) is employed as a sensing element.
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Kim, Kyungbum. "ALL-SEMICONDUCTOR HIGH POWER MODE-LOCKED LASER SYSTEM". Doctoral diss., University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2482.
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The objective of this dissertation is to generate high power ultrashort optical pulses from an all-semiconductor mode-locked laser system. The limitations of semiconductor optical amplifier in high energy, ultrashort pulse amplification are reviewed. A method to overcome the fundamental limit of small stored energy inside semiconductor optical amplifier called "eXtreme Chirped Pulse Amplification (X-CPA)" is proposed and studied theoretically and experimentally. The key benefits of the concept of X-CPA are addressed. Based on theoretical and experimental study, an all-semiconductor mode-locked X-CPA system consisting of a mode-locked master oscillator, an optical pulse pre-stretcher, a semiconductor optical amplifier (SOA) pulse picker, an extreme pulse stretcher/compressor, cascaded optical amplifiers, and a bulk grating compressor is successfully demonstrated and generates >kW record peak power. A potential candidate for generating high average power from an X-CPA system, novel grating coupled surface emitting semiconductor laser (GCSEL) devices, are studied experimentally. The first demonstration of mode-locking with GCSELs and associated amplification characteristics of grating coupled surface emitting SOAs will be presented. In an effort to go beyond the record setting results of the X-CPA system, a passive optical cavity amplification technique in conjunction with the X-CPA system is constructed, and studied experimentally and theoretically.Ph.D.
Optics and Photonics
Optics
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Rocha, HÃlio Henrique Barbosa. "Ressoadores e guias dielÃtricos cilÃndricos operando em micro-ondas e Ãptica: antenas dielÃtricas e acopladores refletores de Bragg a fibra". Universidade Federal do CearÃ, 2010. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=7068.
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FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgicoCoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior
Duas contribuiÃÃes caracteristicamente distintas, nÃo obstante correlacionÃveis num mesmo sistema de telecomunicaÃÃo, sÃo apresentadas. A primeira versa sobre antenas ressoadoras constituÃdas por novas cerÃmicas dielÃtricas à base de Fe2O3. Os materiais desenvolvidos foram caracterizados na faixa de micro-ondas. Tratam-se de dielÃtricos com baixa permissividade relativa, baixa tangente de perda, e, no caso das amostras monofÃsicas, com coeficiente de temperatura na frequÃncia de ressonÃncia negativo. Posteriormente, as antenas ressoadoras dielÃtricas de geometria cilÃndrica (CDRAs) suportadas em plano de terra retangular e alimentadas por sonda monopolar sÃo analisadas segundo critÃrios de desempenho de irradiaÃÃo, quais sejam: frequÃncia de ressonÃncia, impedÃncia de entrada, largura de banda e padrÃes de irradiaÃÃo. AlÃm de experimentaÃÃo, o seu estudo envolveu procedimento computacional, no que foi promovida a comparaÃÃo de resultados. O mÃtodo dos elementos finitos, no qual està baseado o programa comercial empregado, foi utilizado para anÃlise destas antenas. Resulta que para maiores valores de permissividade relativa de uma amostra, menores sÃo a frequÃncia em que a mesma ressoa e a sua largura de banda. Ainda, foi observado satisfatÃrio casamento de impedÃncia e padrÃes de irradiaÃÃo "broadside", o que candidata os novos materiais desenvolvidos a esta importante aplicaÃÃo. Adicionalmente, mediante empilhamento dos protÃtipos monofÃsicos examinados, foi verificada a remodelagem da largura de banda em relaÃÃo Ãs contrapartidas individuais, provavelmente devido à excitaÃÃo de modos de ordem elevada das CDRAs. A segunda contribuiÃÃo està enfocada no contexto dos guias de ondas dielÃtricos operando em frequÃncias Ãpticas. Neste cenÃrio, sÃo investigados acopladores refletores de Bragg a fibra (FBGCs), estruturas resultantes da combinaÃÃo de dois dispositivos reconhecidamente versÃteis e de ampla aplicaÃÃo: redes de Bragg e acopladores direcionais. Foram apreciados dois estudos de caso numÃricos nos quais se fez promover a interaÃÃo de sinais Ãpticos com as estruturas propostas. Na medida em que descreve com satisfatÃria precisÃo as propriedades Ãpticas dos dispositivos de interesse, o modelo matemÃtico empregado à baseado na teoria dos modos acoplados. O tratamento numÃrico à realizado mediante codificaÃÃo, em linguagem de programaÃÃo FORTRAN, de um algoritmo preditivo-corretor. Considerando regimes pulsados em termos da potÃncia operacional, o problema foi analisado no domÃnio da frequÃncia e, sobretudo, no domÃnio do tempo. Em condiÃÃes especÃficas, a possibilidade de realizaÃÃo da extraÃÃo, reconfiguraÃÃo e comutaÃÃo de pulsos, exemplos de funÃÃes essenciais ao processamento totalmente Ãptico, reforÃam a importÃncia de tais estruturas hÃbridas.
Two heterogeneous contributions to modern communication systems â although fully possible to be correlated â are presented. The first one deals with resonant antennas consisting of new dielectric ceramics based on Fe2O3. These materials characterized at microwave frequency range possess low relative permittivity, low loss tangent and, concerned with the monophasic samples, negative temperature coefficient of resonant frequency. Subsequently, the cylindrical dielectric resonator antennas (CDRAs) supported on rectangular ground plane and fed by monopole are analyzed according to the following radiation performance criteria: resonant frequency, input impedance, bandwidth and radiation patterns. Besides experimentation, the study involved computational procedure, so that the results of both can be compared. A commercial software based on the finite element method was employed to examine the CDRAs. It follows that as higher is the permittivity of a material, the lower are the frequency at which it resonates as well as its bandwidth. Satisfactory impedance matching and broadside radiation patterns are observed, what enables the materials investigated to this relevant application. Additionally, the stacking of the monophasic CDRAs prototypes resulted in bandwidth enhancement, presumably due to their excited high order modes. The second contribution focuses on dielectric waveguides operating at optical frequencies, being fiber Bragg grating couplers (FBGCs) investigated in this scenario. Indeed, they result from a combination of two versatile and widely applied devices: fiber Bragg gratings and directional couplers. Two numerical case studies related to the interaction between optical signals and structures were performed. The theoretical model observed is based on the coupled mode theory since it provides a satisfactorily accurate description of the devices optical properties. By the way, the theoretical model is coded in FORTRAN programming language according to a predictor-corrector algorithm. In terms of operational power levels, analyses are carried out in frequency and (mainly) time domains. Under specific conditions, the capability of the extraction, reshaping and switching of pulses â examples of essential functions for all-optical processing â reinforces the importance of such hybrid structures.
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Sharath, U. "Fiber Bragg Grating Based Sensing Devices for Novel Applications in Bio-medical and Engineering Fields". Thesis, 2015. https://etd.iisc.ac.in/handle/2005/4556.
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Sensors have been an integral part of human life. Various sensor technologies have contributed in their own ways to fulfill specific requirements for aiding human beings. In this context, fiber optic sensors have several advantages such as availability of large number of components from communication industry, small footprint, easy fabrication, and immunity to Electro Magnetic Interference. In the category of fiber optic sensors, Fiber Bragg Gratings (FBGs) have been found to be very useful, because of their high sensitivity, multi-modal sensing ability, large operational bandwidth, and multiplexing capability.
An FBG is a periodic orthogonal perturbation of the refractive index along the longitudinal axis of the core of a single mode optical fiber. The periodic modulation of index of refraction is brought about by exploiting the photosensitivity of a germania- doped silica fiber upon exposure to UV light. FBGs, in the basic form, can sense strain and temperature. However, in recent years, several newer sensing applications of FBGs are being explored and the present thesis is an attempt in this direction.
In this thesis work, Fiber Bragg Grating sensor-based devices have been devised for newer applications in bio-medical and engineering fields. Basically, novel packaging methodologies for FBGs are designed and developed, which transduce the measured parameter to a secondary parameter that can be sensed by the FBG.
In the field of Cardiology, an FBG Pulse Recorder has been developed which has the ability to acquire the radial arterial pulse pressure waveform. It records the beat-to-beat pulse pressure along with the radial arterial diametrical variations. The FBG Pulse Recorder has been employed to measure the blood pressure in conjunction with a sphygmomanometer, using the unique signatures obtained in the radial arterial pulse pressure waveform. By the same methodology, radial arterial compliance, is evaluated. Also, using two FBG Pulse Recorders at the carotid and radial arterial sites the pulse transit time differential is measured which acts as an indicator of variation in systolic blood pressure and pulse wave velocity.
In the field of dentistry, a novel technique for real time dynamic measurement of the maximum individual bite force using Fiber Bragg Grating Bite Force Recorder has been proposed. The results obtained show that bite forces increase along the dental arch and are found to be higher in male than in female. Also, an in-vitro study utilizing the FBG temperature sensor has been carried out to measure the variation of temperature in the pulp chamber during light curing of composite materials.
In the field of seismology, a new methodology for real time dynamic monitoring of seismic vibrations, using a Fiber Bragg Grating Seismic Sensor has been proposed. The validation and field tests are carried out in comparison with a commercial seismometer. Further, the feasibility study for an elephant intrusion monitoring system employing the sensor developed has been put forth.
Furthermore, a displacement device has been devised which converts displacement into strain on a cantilever beam over which the FBG sensor is bonded with the aid of a pivoted arm. This arm provides the necessary mechanical amplification of the displacement by varying the pivot screw position, facilitating tunable sensitivity for the FBG displacement device. Also, the same device has been used for measurement of vibration and with enhanced sensitivity for surface profilometry with a resolution of 175nm.
To summarize, the present thesis demonstrates a comprehensive experimental study which bring out the utility of FBG sensors in variety of challenging applications.
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Padma, G. Srivani. "Fiber Bragg Grating Sensor Based Devices for Novel Biomedical Applications". Thesis, 2017. https://etd.iisc.ac.in/handle/2005/4316.
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The present thesis work comprises of design and development of devices based on Fiber Bragg Grating (FBG) sensors for novel biomedical applications. Here, novel packaging methodologies have been utilized for transduction of the measurand parameter into a secondary parameter that can be sensed by the FBG sensor.
Chapter 2 of the thesis deals with the theory of FBGs along with photosensitive property of fibers, theory and fabrication techniques of FBGs, etc. Among the FBG fabrication techniques, the phase mask method of inscription is emphasized, as the FBG sensors utilized for the research work undertaken in the present thesis have been fabricated using this method.
Chapter 3 deals with the study on the usage of a FBG sensor as a communication assistance device. The development of a noninvasive, real-time, communication assistance device employing a FBG sensor, for the assistance of those with restricted communication ability has been presented in this chapter. The communication assistance device comprises of a breath pattern analyzer developed using a FBG sensor, which acquires the exhalation force in the form of strain variations on a cantilever. The present approach is intended to be an alternative to the common approach via brain–computer interface in which an electrode is utilized for learning of brain responses.
Chapter 4 deals with the application of a FBG sensor in the field of dentistry, in which a Bite Force Measurement Device (BFMD) has been demonstrated for the measurement of the individual maximum bite force along the dental occlusion. The developed BFMD facilitates the ability to alter the distance between the biting platform according to the tooth position. Further, clinically relevant bite forces are measured and analyzed.
Chapter 5 provides an insight to another novel application of FBG sensor in the measurement of the Range of Motion (ROM) of joints in human body, which is of prime importance in monitoring the progress of therapeutic procedures. A Fiber Bragg Grating Goniometer (FBGG) has been developed which can be employed to dynamically measure the angular movement of joints. The maximum flexion angles at the elbow along with the plantar and dorsi-flexion angles are evaluated using the FBGG for illustration.
Chapter 6 reports the application of FBG sensor in the field of cardiology, wherein a Fiber Bragg Grating Pulse Probe (FBGPP) developed is described, which comprises the ability to dynamically acquire the arterial pulse pressure waveform. This chapter also deals with the measurement of the Carotid Arterial Pulse Pressure Waveform (CAPPW) of individual subjects, which consists of beat-to-beat carotid pulse pressure, using the proposed FBGPP.
In addition, the pulse wave analysis of the recorded CAPPW is presented, which has been undertaken to evaluate vital cardiovascular parameters and the relationships between them. Lastly, in this chapter, the deployment of the developed FBGPP for radial arterial pulse pressure waveform acquisition in children, has been presented. This study validates the fact of variation of heart rate of children with age. It has been observed that the diastolic time component varies in good accordance with children’s age and in addition it is found to be major contributor to heart rate variation. Furthermore, various cardiovascular parameters are evaluated and compared along with the variation in children’s age.
Finally, chapter 7 gives a summary of the thesis and future directions of the presented research work that are yet to be explored.
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Lee, Hao-Xiang, i 李浩祥. "Development of Non-invasive Optical Metrologies for Profiling Wrist Pulse-Applications of Laser Doppler Interferometer and Fiber Bragg Grating Sensor". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/93514828698371479892.
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碩士國立臺灣大學
工程科學及海洋工程學研究所
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Cardiovascular diseases have been the leading cause of death in recent years. Therefore, regular monitoring of blood pressure has become current trend of personalized health management. The most common and commercialized blood pressure portable device is the electronic sphygmomanometer. It is based on the principle of Oscillometry with a pressurized cuff to measure the systolic and diastolic blood pressure. However, it cannot measure the complete profile of blood pressure, and it is not a comfortable process. To overcome these limitations, current studies have turned to the direction of cuffless and continuous Sphygmomanometer. In this study, we use laser Doppler interferometer to measure the pulse amplitude of the wrist skin. The advantage of this system is it has a resolution as high as 0.08 nm, and the directional ambiguity can be removed by the quadrature interferometer. To increase the stability, we use a wristband to fix a corner cube on wrist and identify the suitable pressure in the range between 70~114 mmHg testing by using a film pressure sensor. We compared our system with Arteriovenous Ultrasound Scanner system and ECG monitor to verify its. Different pulse amplitudes were obtained from different objects, the measurement result was in the range between 25 to 56 μm. The correlation coefficient between pulse amplitude and blood flow velocity was between 0.4 and 0.7. The mean value of heart beating cycle and the result of electrocardiogram have a 73.3% similarity with a less than 0.05 second difference. The correlations among pulse amplitude, blood flow velocity and the accuracy of heart rate measurement were evident. To develop personalized blood pressure sensor, we further develop the fiber Bragg grating to measure the surface strain induced by wrist pulse vibrations. The Bragg wavelength offset of the fiber grating has a nearly linear relationship with surface strain. Using the four point bending test, we found that 1 micro strain could induce 0.1 pm wavelength shift with the correlation coefficient of 0.995. By adjusting the Bragg wavelength, this strain sensor can be applied to measure the profile of wrist pulse. This sensor could potentially combine with wearable device to achieve long time continuous monitoring of blood pressure.
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Raghuwanshi, Sanjeev Kumar. "Analytical And Numerical Study Of Propagation In Optical Waveguides And Devices In Linear And Nonlinear Domains". Thesis, 2008. https://etd.iisc.ac.in/handle/2005/782.
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The objective of this thesis is to study of optical effects, arising in the form of non-uniform waveguide structure, complicated refractive index profiles or due to pulse propagation in dense wavelength division multiplexing (DWDM) optical communication systems. These effects are important and critically influence the performance of DWDM optical systems. A comprehensive survey of current literature on optical effects due to nonuniform optical structure and nonlinear optical effects is first done, showing their advantages and disadvantage in optical communication systems. A survey on methods of optical waveguide analysis is also done. The main contribution has been made to three main aspects of the problem :
Accurate analysis of uniform/non-uniform optical waveguides with arbitary refractive index profiles
Pulse propagation and distortion in DWDM Raman amplification systems.
Use of non-uniform FBG to compensate for pulse distortion
We study several existing analytical techniques developed so far for analyzing the mode of non-uniform optical waveguide structures. Later, we verify the analytical results by finite element method (FEM). The convergence study is also carried out. A new computational technique is proposed modifying the finite element method to analyze complex refractive index profiles required for the analysis, namely single mode step index profile, multi clad fiber, W -profile, chirp profile etc. An accuracy of 10−4 in the calculation of propagation constant/eigen-value is demonstrated. Dispersion characteristics of optical fibers w.r.t. different profile parameters is evaluated. A modification to scalar BPM is proposed and applied to study the effects of inhomogeneities along the propagation direction. The applicability and accuracy of the method is tested using integrated optic waveguide devices, namely, graded index slab waveguide. The proposed BPM uses Fourier decomposition of the transverse field. Coupled mode theory (CMT) of optical waveguides in non-homogeneous optical medium is applied to study the interaction of lightwaves propagation together such as in a DWDM system. The BPM results is verified by CMT.
The inhomogeneous waveguide theory is extended to study pulse propagation in DWDM optical communication system. Nonlinear optical effects are an important aspects of DWDM systems with fiber Raman amplifier. Finite difference time domain (FDTD) method is necessary to study these nonlinear optical effects as other conventional methods are not suitable here. Here, we discuss DWDM optical communication systems due to nonlinearity in the form of SRS effect. In case of FRA, we study the various kinds of fiber profile design parameters, for the purpose to achieve and extend the flat gain bandwidth over the EDFA window. We also propose and study, a new bi-directional optical fiber transmission scheme with various constraints, using Raman amplification process with and without pump depletion. Our scheme, provides an advantage like high SNR, low pump induced noise, for long-haul communication link. We find that, there is a quite significant crosstalk and power coupling among the dense DWDM channels but earlier discussed BPM fails to account for possible interference effects among the channels. To reduce the harmful nonlinear optical effects like four wave mixing (FWM), we need to deploy a high chromatic dispersion fiber, which will ultimately lead to high pulse walk-off rate among the DWDM channels; hence for high bit rate long haul systems, walk-off effect can not be ignored. Application of FDTD provided an improved insight into the effect of GVD on stimulated Raman scattering crosstalk than different modulation techniques and line codes. It is shown through analysis that pulse walk-off phenomena may distort the data asymmetrically; especially for case of wide-band DWDM transmission system. Hence, the pulse walk-off effect should be considered in future systems containing optical amplifier. It is shown, that large walk-off rate may reduce the crosstalk among DWDM channels but tends to increase the asymmetric pulse distortion. Data may lose due to high walk-off effect. We also investigate channel addition/removal process in DWDM fiber Raman amplifier. We also demonstrate that the pulse walk-off effect tends to lead significantly to positive chirp for higher frequency channels. This feature can be exploited to overcome the chromatic dispersion effects in DWDM transmission systems.
Pulse walk-off induced chirp, can be compensated by using the nonuniform fiber Bragg grating (NUFBG). The CMT due to periodic perturbation of the circular cylindrical waveguide structures is applied here. Here, we discuss the function of fiber Bragg grating as a transmission versus reflecting grating filter. We also discuss, FBG application to gain flattening of an EDFA window as well as how the group velocity dispersion (GVD) will be affected with bandwidth and coupling coefficient. We develop a new analytical technique to estimate the bandwidth of FBG based optical system. Finally, we investigate the dispersion compensation properties, pulse distortion, peak reflectivity analysis in uniform/non-uniform FBG due to an uniform/non-uniform incoming signal. More complicated refractive index profile can significantly reduce the GVD as well as side lobes intensity. Dispersion characteristic due to an arbitrary refractive index profile is discussed in details for the case of non-uniform FBG. Thus, we concluded that wide band DWDM optical communication system need to closely take into account various inhomogeneities and nonlinearities of optical fibers w.r.t. wave and pulse propagation.
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Raghuwanshi, Sanjeev Kumar. "Analytical And Numerical Study Of Propagation In Optical Waveguides And Devices In Linear And Nonlinear Domains". Thesis, 2008. http://hdl.handle.net/2005/782.
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The objective of this thesis is to study of optical effects, arising in the form of non-uniform waveguide structure, complicated refractive index profiles or due to pulse propagation in dense wavelength division multiplexing (DWDM) optical communication systems. These effects are important and critically influence the performance of DWDM optical systems. A comprehensive survey of current literature on optical effects due to nonuniform optical structure and nonlinear optical effects is first done, showing their advantages and disadvantage in optical communication systems. A survey on methods of optical waveguide analysis is also done. The main contribution has been made to three main aspects of the problem :
Accurate analysis of uniform/non-uniform optical waveguides with arbitary refractive index profiles
Pulse propagation and distortion in DWDM Raman amplification systems.
Use of non-uniform FBG to compensate for pulse distortion
We study several existing analytical techniques developed so far for analyzing the mode of non-uniform optical waveguide structures. Later, we verify the analytical results by finite element method (FEM). The convergence study is also carried out. A new computational technique is proposed modifying the finite element method to analyze complex refractive index profiles required for the analysis, namely single mode step index profile, multi clad fiber, W -profile, chirp profile etc. An accuracy of 10−4 in the calculation of propagation constant/eigen-value is demonstrated. Dispersion characteristics of optical fibers w.r.t. different profile parameters is evaluated. A modification to scalar BPM is proposed and applied to study the effects of inhomogeneities along the propagation direction. The applicability and accuracy of the method is tested using integrated optic waveguide devices, namely, graded index slab waveguide. The proposed BPM uses Fourier decomposition of the transverse field. Coupled mode theory (CMT) of optical waveguides in non-homogeneous optical medium is applied to study the interaction of lightwaves propagation together such as in a DWDM system. The BPM results is verified by CMT.
The inhomogeneous waveguide theory is extended to study pulse propagation in DWDM optical communication system. Nonlinear optical effects are an important aspects of DWDM systems with fiber Raman amplifier. Finite difference time domain (FDTD) method is necessary to study these nonlinear optical effects as other conventional methods are not suitable here. Here, we discuss DWDM optical communication systems due to nonlinearity in the form of SRS effect. In case of FRA, we study the various kinds of fiber profile design parameters, for the purpose to achieve and extend the flat gain bandwidth over the EDFA window. We also propose and study, a new bi-directional optical fiber transmission scheme with various constraints, using Raman amplification process with and without pump depletion. Our scheme, provides an advantage like high SNR, low pump induced noise, for long-haul communication link. We find that, there is a quite significant crosstalk and power coupling among the dense DWDM channels but earlier discussed BPM fails to account for possible interference effects among the channels. To reduce the harmful nonlinear optical effects like four wave mixing (FWM), we need to deploy a high chromatic dispersion fiber, which will ultimately lead to high pulse walk-off rate among the DWDM channels; hence for high bit rate long haul systems, walk-off effect can not be ignored. Application of FDTD provided an improved insight into the effect of GVD on stimulated Raman scattering crosstalk than different modulation techniques and line codes. It is shown through analysis that pulse walk-off phenomena may distort the data asymmetrically; especially for case of wide-band DWDM transmission system. Hence, the pulse walk-off effect should be considered in future systems containing optical amplifier. It is shown, that large walk-off rate may reduce the crosstalk among DWDM channels but tends to increase the asymmetric pulse distortion. Data may lose due to high walk-off effect. We also investigate channel addition/removal process in DWDM fiber Raman amplifier. We also demonstrate that the pulse walk-off effect tends to lead significantly to positive chirp for higher frequency channels. This feature can be exploited to overcome the chromatic dispersion effects in DWDM transmission systems.
Pulse walk-off induced chirp, can be compensated by using the nonuniform fiber Bragg grating (NUFBG). The CMT due to periodic perturbation of the circular cylindrical waveguide structures is applied here. Here, we discuss the function of fiber Bragg grating as a transmission versus reflecting grating filter. We also discuss, FBG application to gain flattening of an EDFA window as well as how the group velocity dispersion (GVD) will be affected with bandwidth and coupling coefficient. We develop a new analytical technique to estimate the bandwidth of FBG based optical system. Finally, we investigate the dispersion compensation properties, pulse distortion, peak reflectivity analysis in uniform/non-uniform FBG due to an uniform/non-uniform incoming signal. More complicated refractive index profile can significantly reduce the GVD as well as side lobes intensity. Dispersion characteristic due to an arbitrary refractive index profile is discussed in details for the case of non-uniform FBG. Thus, we concluded that wide band DWDM optical communication system need to closely take into account various inhomogeneities and nonlinearities of optical fibers w.r.t. wave and pulse propagation.
Streszczenia konferencji na temat "Fiber Bragg Grating Pulse Recorder"
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Kaczmarek, Tomasz, i Zdzisław Kaczmarek. "Modified fiber Bragg grating pulse pressure sensor". W SPIE Proceedings, redaktorzy Jan Wójcik i Waldemar Wójcik. SPIE, 2007. http://dx.doi.org/10.1117/12.739737.
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Krishna, VS Rakesh, i E. S. Shivaleela. "Asymmetric-Pulse Shaping Technique Using Fiber Bragg Grating". W 2017 IEEE Workshop on Recent Advances in Photonics (WRAP). IEEE, 2017. http://dx.doi.org/10.1109/wrap.2017.8468587.
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Ferchichi, Moez, Monia Najjar i Houria Rezig. "Pulse reflection of tunable Fiber Bragg Grating WDM filter". W 2010 17th International Conference on Telecommunications. IEEE, 2010. http://dx.doi.org/10.1109/ictel.2010.5478853.
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Li, Ming, Liyang Shao, Jacques Albert i Jianping Yao. "Chirped microwave pulse generation using a tilted fiber Bragg grating". W 2010 23rd Annual Meeting of the IEEE Photonics Society (Formerly LEOS Annual Meeting). IEEE, 2010. http://dx.doi.org/10.1109/photonics.2010.5699027.
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Zhang, Chengtao, Xiaochao Wang, Wei Fan, Daxing Rao i Zunqi Lin. "Pulse multi-pass stretcher using linear chirped fiber Bragg grating". W ISPDI 2013 - Fifth International Symposium on Photoelectronic Detection and Imaging, redaktorzy Andreas Tünnermann, Zejin Liu, Pu Wang i Chun Tang. SPIE, 2013. http://dx.doi.org/10.1117/12.2035015.
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Nishimura, Aikihko, Yukihiro Shimada, Yukihiro Yonemoto, Hirokazu Suzuki i Hisayoshi Ishibashi. "Development of pulse laser processing for mounting fiber Bragg grating". W LASER-DRIVEN RELATIVISTIC PLASMAS APPLIED TO SCIENCE, ENERGY, INDUSTRY, AND MEDICINE: The 3rd International Symposium. AIP, 2012. http://dx.doi.org/10.1063/1.4737569.
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Eggleton, B. J., R. E. Slusher, T. A. Strasser i C. M. de Sterke. "High intensity pulse propagation in fiber Bragg gratings". W Bragg Gratings, Photosensitivity, and Poling in Glass Fibers and Waveguides. Washington, D.C.: Optica Publishing Group, 1997. http://dx.doi.org/10.1364/bgppf.1997.bmb.1.
Pełny tekst źródłaStreszczenie:
Recently we reported the first systematic experiments describing high intensity pulse propagation in fiber Bragg gratings [1-3]. These experiments demonstrated nonlinear pulse compression, and pulse shaping, and also demonstrated the generation and propagation of grating solitons [1]. which exist because of the balancing of nonlinearity of the glass and the strong dispersion of the grating [4-6]. Possibly the most striking feature of these solitons is that they can travel at velocities between zero and the speed of light in the medium. Indeed initial experimental, which were performed in uniform (unchirped) gratings, indicated that the solitons propagated at about 75% of the speed of light in the uniform medium. In this paper we review the nonlinear optics of fiber gratings and in particular discuss the experimental realization of grating solitons. We also discuss two extensions of this work: launching of slow grating solitons in apodized fiber gratings; and experimental studies of modulational instabilities (MIs) in Bragg gratings. Finally we mention the possibility of soliton engineering, through the design of nonuniform gratings.
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Curatu, George, Sophie LaRochelle, Claude Pare i Pierre-Andre Belanger. "Pulse shaping with a phase-shifted fiber Bragg grating for antisymmetric pulse generation". W Photonics West 2001 - LASE, redaktor Yehuda B. Band. SPIE, 2001. http://dx.doi.org/10.1117/12.424698.
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Komukai, T., T. Yamamoto i S. Kawanishi. "Optical pulse generator using phase modulator and chirped fiber Bragg grating". W 2005 Optical Fiber Communications Conference Technical Digest. IEEE, 2005. http://dx.doi.org/10.1109/ofc.2005.193000.
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Wang, Chao, i Jianping Yao. "Fourier-transform pulse shaping using a single chirped fiber Bragg grating". W Multimedia Technology (IC-BNMT). IEEE, 2009. http://dx.doi.org/10.1109/icbnmt.2009.5347815.
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