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Literatura académica sobre el tema "Distributed reflectometry"

Autor: Grafiati

Publicado: 25 de mayo de 2024

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Artículos de revistas sobre el tema "Distributed reflectometry"

Mizuno, Yosuke, Neisei Hayashi, Hideyuki Fukuda, Kwang Yong Song y Kentaro Nakamura. "Ultrahigh-speed distributed Brillouin reflectometry". Light: Science & Applications 5, n.º 12 (30 de junio de 2016): e16184-e16184. http://dx.doi.org/10.1038/lsa.2016.184.

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Gorlov, N. I. y I. V. Bogachkov. "DISTRIBUTED SENSING OF FIBER-OPTIC COMMUNICATION LINES USING BRILLOUIN SCATTERING". DYNAMICS OF SYSTEMS, MECHANISMS AND MACHINES 11, n.º 4 (2023): 71–75. http://dx.doi.org/10.25206/2310-9793-2023-11-4-71-75.

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The report discusses the main aspects of distributed sensing of fiber-optic communication lines using Brillouin scattering. The results of the study of the main functional capabilities of the method of coherent reflectometry and the method of counter propagating waves are presented. Special attention is paid to the principles of construction of reflectometric systems and the analysis of requirements for optical radiation sources. In conclusion, the main problems and prospects of practical implementation of the investigated method in the practice of monitoring fiber-optic communication lines are formulated

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Zahoor, Rizwan, Raffaele Vallifuoco, Luigi Zeni y Aldo Minardo. "Distributed Temperature Sensing through Network Analysis Frequency-Domain Reflectometry". Sensors 24, n.º 7 (8 de abril de 2024): 2378. http://dx.doi.org/10.3390/s24072378.

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In this paper, we propose and demonstrate a network analysis optical frequency domain reflectometer (NA-OFDR) for distributed temperature measurements at high spatial (down to ≈3 cm) and temperature resolution. The system makes use of a frequency-stepped, continuous-wave (cw) laser whose output light is modulated using a vector network analyzer. The latter is also used to demodulate the amplitude of the beat signal formed by coherently mixing the Rayleigh backscattered light with a local oscillator. The system is capable of attaining high measurand resolution (≈50 mK at 3-cm spatial resolution) thanks to the high sensitivity of coherent Rayleigh scattering to temperature. Furthermore, unlike the conventional optical-frequency domain reflectometry (OFDR), the proposed system does not rely on the use of a tunable laser and therefore is less prone to limitations related to the laser coherence or sweep nonlinearity. Two configurations are analyzed, both numerically and experimentally, based on either a double-sideband or single-sideband modulated probe light. The results confirm the validity of the proposed approach.

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Volanthen, M., H. Geiger y J. P. Dakin. "Distributed grating sensors using low-coherence reflectometry". Journal of Lightwave Technology 15, n.º 11 (1997): 2076–82. http://dx.doi.org/10.1109/50.641525.

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Dominauskas, Aurimas, Dirk Heider y John W. Gillespie. "Electric time-domain reflectometry distributed flow sensor". Composites Part A: Applied Science and Manufacturing 38, n.º 1 (enero de 2007): 138–46. http://dx.doi.org/10.1016/j.compositesa.2006.01.019.

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Bao, Xiaoyi y Yuan Wang. "Recent Advancements in Rayleigh Scattering-Based Distributed Fiber Sensors". Advanced Devices & Instrumentation 2021 (11 de marzo de 2021): 1–17. http://dx.doi.org/10.34133/2021/8696571.

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Recently, Rayleigh scattering-based distributed fiber sensors have been widely used for measurement of static and dynamic phenomena such as temperature change, dynamic strain, and sound waves. In this review paper, several sensing systems including traditional Rayleigh optical time domain reflectometry (OTDR), Φ-OTDR, chirped pulse Φ-OTDR, and optical frequency domain reflectometry (OFDR) are introduced for their working principles and recent progress with different instrumentations for various applications. Beyond the sensing technology and instrumentation, we also discuss new types of fiber sensors, such as ultraweak fiber Bragg gratings and random fiber gratings for distributed sensing and their interrogators. Ultimately, the limitations of Rayleigh-based distributed sensing systems are discussed.

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Rahman, Saifur, Farman Ali, Fazal Muhammad, Muhammad Irfan, Adam Glowacz, Mohammed Shahed Akond, Ammar Armghan, Salim Nasar Faraj Mursal, Amjad Ali y Fahad Salem Alkahtani. "Analyzing Distributed Vibrating Sensing Technologies in Optical Meshes". Micromachines 13, n.º 1 (5 de enero de 2022): 85. http://dx.doi.org/10.3390/mi13010085.

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Hundreds of kilometers of optical fibers are installed for optical meshes (OMs) to transmit data over long distances. The visualization of these deployed optical fibers is a highlighted issue because the conventional procedure can only measure the optical losses. Thus, this paper presents distributed vibration sensing (DVS) estimation mechanisms to visualize the optical fiber behavior installed for OMs which is not possible by conventional measurements. The proposed technique will detect the power of light inside the optical fiber, as well as different physical parameters such as the phase of transmitted light inside the thread, the frequency of vibration, and optical losses. The applicability of optical frequency domain reflectometry (OFDR) and optical time-domain reflectometry (OTDR) DVS techniques are validated theoretically for various state detection procedures in optical fibers. The simulation model is investigated in terms of elapsed time, the spectrum of a light signal, frequency, and the impact of many external physical accidents with optical fibers.

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Kiyozumi, Takaki, Tomoya Miyamae, Kohei Noda, Heeyoung Lee, Kentaro Nakamura y Yosuke Mizuno. "Super-simplified optical correlation-domain reflectometry". Japanese Journal of Applied Physics 61, n.º 7 (1 de julio de 2022): 078005. http://dx.doi.org/10.35848/1347-4065/ac7272.

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Abstract Optical correlation-domain reflectometry (OCDR), which is known as one of the fiber-optic techniques for distributed reflectivity sensing, conventionally included an acousto-optic modulator, a reference path, and erbium-doped fiber amplifiers in its setup. In this work, by removing all of these components simultaneously, we develop a super-simplified configuration of OCDR, which consists of a light source and a photodetector only. We experimentally show that this system can still perform distributed reflectivity sensing with a moderate signal-to-noise ratio, which will boost the portability and cost efficiency of the OCDR technology.

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Fan, Xinyu, Bin Wang, Guangyao Yang y Zuyuan He. "Slope-Assisted Brillouin-Based Distributed Fiber-Optic Sensing Techniques". Advanced Devices & Instrumentation 2021 (14 de julio de 2021): 1–16. http://dx.doi.org/10.34133/2021/9756875.

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Brillouin-based fiber-optic sensing has been regarded as a powerful distributed measurement tool for monitoring the conditions of modern large civil and geotechnical structures, since it provides continuous environmental information (e.g., temperature and strain) along the whole fiber used for sensing applications. In the past few decades, great research efforts were devoted to improve its performance in terms of measurement range, spatial resolution, measurement speed, sensitivity, and cost-effectiveness, of which the slope-assisted measurement scheme, achieved by exploiting the linear slope of the Brillouin gain spectrum (BGS), have paved the way for dynamic distributed fiber-optic sensing. In this article, slope-assisted Brillouin-based distributed fiber-optic sensing techniques demonstrated in the past few years will be reviewed, including the slope-assisted Brillouin optical time-domain analysis/reflectometry (SA-BOTDA/SA-BOTDR), the slope-assisted Brillouin dynamic grating (BDG) sensor, and the slope-assisted Brillouin optical correlation domain analysis/reflectometry (SA-BOCDA/SA-BOCDR). Avenues for future research and development of slope-assisted Brillouin-based fiber-optic sensors are also prospected.

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Zhou, Da-Peng, Liang Chen y Xiaoyi Bao. "Distributed dynamic strain measurement using optical frequency-domain reflectometry". Applied Optics 55, n.º 24 (18 de agosto de 2016): 6735. http://dx.doi.org/10.1364/ao.55.006735.

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Tesis sobre el tema "Distributed reflectometry"

Luo, Linqing. "Time-frequency localisation of distributed Brillouin Optical Time Domain Reflectometry". Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/274568.

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Distributed fibre optic sensing (DFOS) is essential for structural health monitoring (SHM) of strain changes induced during the lifetime of a structure. Among different DFOS systems, the Brillouin Optical Time Domain Reflectometry (BOTDR) takes the advantages of obtaining full frequency spectrum to provide strain and temperature information along the optic fibre. The key parameters of distributed fibre optic sensors, spatial and frequency resolution, are strongly linked with the time-frequency (T-F) localisation in the system in three parts: pulse, hardware design and optical fibre. T-F localization is fundamentally important for the communication system, whereas in this study the importance of the T-F localisation to the spatial and frequency resolution, repeatability and the measurement speed are introduced in BOTDR. In this dissertation, the development of DFOS is first introduced, including both traditional methods and new developed designs. The literature review shows the signal to noise ratio (SNR) of BOTDR can be improved by investigating its T-F localisation. In the hardware design, in order to improve the T-F localisation in hardware architecture, a Short-Time Fourier Transform-Brillouin Optical Time-Domain Reflectometry (STFT-BOTDR), which implements STFT over the full frequency spectrum to measure the distributed temperature and strain along the optic fibre, is applied so that the conventional frequency sweeping method can be replaced for high resolution and fast speed measurement, providing new research advances in dynamic distributed sensing. The STFT based BOTDR has better T-F localisation, which in turn provides an opportunity for off-line post signal processing that is more adaptable for fast speed measurements. The spatial and frequency resolution of dynamic BOTDR sensing is limited by the Signal to Noise Ratio (SNR) and the T-F localization of the input pulse shape. The T-F localized input pulse shape can enhance the SNR and the spatial and frequency resolution in STFT-BOTDR. In this study, simulation and experiments of T-F localized different pulses shapes are conducted to examine the limitation of the system resolution. The result indicates that a rectangular pulse should be selected to optimize the spatial resolution and a Lorentzian pulse could be chosen to optimize the frequency resolution, while a Gaussian shape pulse can be used in general applications for its balanced performance in both spatial and frequency resolution. Meanwhile, T-F localization is used for pulse T-F localisation optimisation. A set of Kaiser-Bessel functions is used to simulate different pulse shapes and to compare their parameters in terms of T-F localisation and their Brillouin scattering spectrum. A method using an iterative filtering algorithm to achieve the optimised pulse in terms of T-F localisation is introduced to converge the Effective-pulse Width (TEW) in the time-domain and Effective-pulse Linewidth (FEL) in the frequency domain to identify the fundamental limitations. The optimised pulse can be fitted with a 7th order Gaussian (super-Gaussian) shape and it offers the best experimental performance compared to a Rectangular pulse. The sensitivity of a sensor to strain or temperature variations due to distributed Brillouin scattering is closely related to the power distribution on the Brillouin scattering spectrum which is related to the property of the optic fibre. The performance of a highly nonlinear fibre that can generate a higher Brillouin scattering signal is compared to that of a standard single mode fibre. The results show that much higher SNR of the Brillouin scattering spectrum and smaller frequency uncertainties in the sensing measurement can be achieved by using a highly nonlinear fibre for comparable launched powers. With a measurement speed of 4 Hz, the frequency uncertainty can be 0.43 MHz, corresponding to 10 με in strain or 0.43°C in temperature uncertainty for the tested highly nonlinear fibre. In contrast, for a standard single mode fibre, the value would increase to about 1.02 MHz (25 με or 1.02°C), demonstrating the advantage of the tested highly nonlinear fibre for distributed strain/temperature sensing. Results show that, by using a small effective area highly nonlinear fibre, the strain or temperature resolution can be improved because it generates stronger Brillouin scattering signal with high SNR and high Q factor spectrum, both of which determine the optimal averaging time in a single measurement. In general, the STFT-BOTDR can achieve 1 m spatial resolution, 10 με frequency resolution on a 10 km fibre with measurement speed at about 2.5 kHz.

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Wu, Nan. "Optical Frequency Domain Reflectometry Based Quasi-distributed High Temperature Sensor". Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/76905.

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Temperature sensing in harsh environment is desired in many areas, such as coal gasification, aerospace, etc. Single crystal sapphire is an excellent candidate for construction of harsh environment sensors due to its superior mechanical and optical properties even at temperature beyond 1600°C. The temperature inside a coal gasifier can be as high as 1200°C. And there is dramatic temperature gradient between the inner and outer layers of the gasifier refractory. Previous work has been done at Virginia Tech's Center for Photonics Technology to design and fabricate a sapphire wafer based Fabry-Perot interferometer (FPI) sensor for temperature sensing in coal gasifiers. The sensor head is based on the use of sapphire wafer which is attached to a lead-in sapphire fiber to be applied in the ultrahigh temperature region; and the sapphire fiber is spliced to a multi-mode fused silica fiber for quality signal transmission in lower temperature areas. One of the challenges encountered by this approach is the shear force to the sapphire fiber, which is caused by the differential thermal expansion between the inner and outer layers of the gasifier refractory. This shear force may be so significant to break the sensor probe. This thesis proposed a free space based interrogation sensing system to address that problem. In this free space based interrogation sensing system, only the sensor head is placed in the inner refractory wall, while all the other parts of the system are placed in the outer refractory or outside the gasifier at the ambient room temperature. An optical frequency domain reflectometry (OFDR) based multiplexed technique is applied in the sensor design to realize temperature measurement at multiple locations along the optical path. In this work, three sapphire wafers based multiplexed temperature sensor is fabricated and calibrated in laboratory. This multiplexed high temperature sensor shows linear response in the range of 20°C ~ 1000°C, with a sensitivity of 1.602?10??/°C and a resolution of 1.3°C.
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Ek, Simon. "Distributed Temperature Sensing Using Phase-Sensitive Optical Time Domain Reflectometry". Thesis, KTH, Tillämpad fysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-285902.

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This thesis explores and evaluates the temperature measuring capabilities of a phase-sensitive optical time-domain reflectometer (φ-OTDR), which exploits Rayleigh backscattering in normal single mode optical fibers. The device is constructed and its setup explained, and a protocol for making temperature measurements with it is developed. Performance tests are made and the device is shown to achieve fully distributed temperature measurements on fibers hundreds of meters in length with a spatial resolution of 1 m and a temperature resolution of 0.1 K. In addition, the capabilities of the device to measure normal strain in the measurement fiber are tested using the same approach, albeit with less success. The device is capable of very precise measurements, making it very sensitive to the environmental conditions around the measuring fiber but also susceptible to disturbances. Some discussion is had on how to avoid or deal with these disturbances. Furthermore, the technique is shown to be able to run in conjunction with other φ-OTDR measurement techniques from the same device simultaneously.
Det här examensarbetet utforskar och utvärderar förmågorna att mäta temperatur hos en fas-känslig optisk tidsdomän-reflektometer (φ-OTDR), som utnyttjar bakåtriktad Rayleigh-spridning i vanliga optiska singelmodfibrer. Anordningen konstrueras och dess komponentstruktur förklaras, och ett protokoll tas fram för att utföra mätningar med den. Prestandatester utförs och anordningen visas kapabel att göra fullt distribuerade temperaturmätningar längs hundratals meter långa fibrer, med en rymdsupplösning på 1 m och en temperaturupplösning på 0.1 K. Dessutom testas förmågan att mäta normaltöjning hos testfibern med samma metod, dock med mindre framgång. Anordningen är väldigt känslig för förhållandena i omgivningen runt mätningsfibern, vilket gör den kapabel till mätningar med mycket hög precision, men också mottaglig för störningar. Lite diskussion hålls kring hur dessa störningar kan undvikas eller hanteras. Vidare visas att mätningstekniken kan köras samtidigt som andra φ-OTDR-baserade tekniker från samma anordning.

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Saunders, Charles T. W. "Optical fibre sensing by time domain reflectometry". Thesis, University of Manchester, 2006. https://www.research.manchester.ac.uk/portal/en/theses/distributed-optical-fibre-sensing(f1857f29-5af2-4e94-97dd-164f3d67f29b).html.

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This thesis considers cost effective optical time domain rcflectometry for distributed fibre sensors, using new developments in light sources, detectors, fibres and computational power, suitable to interrogate distributed fibre sensors from 20m to 10km, within a £5,000 hardware budget. The characteristics of 200μm core diameter polymer clad silica (PCS) fibre and 980μm core diameter PMMA POF (polymethyl methacrylate plastic optical fibre) were theoretically evaluated including damage thresholds, optimum sensitisation (evanescent field attenuation and micro-bending) and launch conditions for optimum performance as a distributed sensor. Rayleigh backscattered signals, forward-propagating power and Fresnel reflections for different fibre types at different distances along the fibre were considered. PCS fibre allows solutes and gases ready access to the core-cladding interface and is preferred for distributed optical fibre sensors (DOFS) of 1000m. 50-125 graded index multimode fibre is preferred as a sensor of mechanical measurands for DOFS 10km long. The higher backscattering coefficient of PMMA POF returns the highest reflected signals for DOFS of up to 30m. Test beds of simulated distributed optical fibre sensors built from single- and multimode silica, hybrid and PCS fibres were assembled for interrogation by visible and NIR wavelengths using mechanical measurands and misaligned splices as point losses, to determine the relationships between launch pulse power, pulse width and backscattered power and the factors determining spatial resolution and dynamic range. Commercial analogue OTDRs (optical time domain reflectometers) and custom-built photon counting OTDRs (ν-OTDRs) were used to probe the fibre sensors. This enabled the design, custom build and evaluation of an OTDR-based DOFS system where the light source may easily be changed for one of a different power or wavelength. The performance of intrinsic or modified fibres in applications of chemical and pH sensing was evaluated: A simulated distributed PMMA POF was demonstrated to sense pH to a resolution of ±1 pH when placed in aqueous solutions of 4.2 x 10⁻⁴ M methyl red between pH 2.89 and 9.70 and probed with 648nm light using a ν-OTDR. An undyed PCS fibre was used to sense aqueous methyl red when probed with 657nm light from a ν-OTDR. An undyed PCS fibre was used to detect 6.5 x 10⁻⁴ M methyl red in ethanol using 657nm light from a ν-OTDR by modifying the cladding refractive index from 1.401 to 1.370. A PCS fibre dyed with 4.4 x 10⁻⁶ M chlorophyll a in ethanol solution then dried was probed by ν-OTDR at 657nm, returning a 4.0dB peak on the trace indicating detection by Fresnel reflection by light in the cladding. A slope of -2.0dB/m on the trace indicated evanescent field absorption due to the 662nm absorption peak. An avalanche photodiode (APD) detection system with inherent stability suitable for long term monitoring of Rayleigh back-scattered signals was designed and built. The modules included an active quench and recharge circuit capable of 20MHz count rate with a novel quenching circuit bias arrangement to provide immunity from spurious triggering, and a Peltier cooler circuit to regulate the APD to ± 0.1°C. A dynamic bias control system based around a PCI-6602 (NI) counter-timer card was designed, built, evaluated and shown by calculation to limit the tolerance on 2.0V excess bias to ± 0.048V. The tighter control of the excess bias stabilises quantum efficiency, resolution and dark count.

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Stastny, Jeffrey Allen. "Time domain reflectometry (TDR) techniques for the design of distributed sensors". Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-09122009-040407/.

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Ren, Meiqi. "Distributed Optical Fiber Vibration Sensor Based on Phase-Sensitive Optical Time Domain Reflectometry". Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34400.

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In this thesis, the work focuses on developing distributed optical fiber vibration sensors based on phase-sensitive optical time domain reflectometry (Φ-OTDR). Three works have been accomplished to improve the performances of Φ-OTDR for distributed vibration sensing. Firstly, Φ-OTDR based on a polarization diversity scheme is demonstrated to mitigate the polarization mismatch effect occurring in traditional systems. A theoretical analysis is performed in different polarization cases corresponding to coherent and polarization diversity detection. Φ-OTDR based polarization diversity shows a great potential in the multi-events sensing application. Two vibration events are simultaneously detected and their signal to noise ratios are improved by 10.9 dB and 8.65 dB, respectively, compared to the results obtained by a conventional coherent scheme. Intensity fluctuation in a phase-sensitive optical-time domain reflectometry (Φ-OTDR) system caused by stochastic characteristics of Rayleigh backscattering has limited relative vibration strength measurement, which is proportional to dynamic strain. A trace-to-trace correlation coefficient is thus proposed to quantify the Φ-OTDR system stability and a novel approach of measuring the dynamic strain induced by various driving voltages of lead zicronate titanate (PZT) is demonstrated. Piezoelectric vibration signals are evaluated through analyzing peak values of the fast Fourier transform spectra at fundamental frequency and high-order harmonics based on Bessel functions. Experimental results show high correlation coefficients and good stability of our Φ-OTDR system, as well as the small measurement uncertainty of measured peak values. To reduce the intra-band noise caused by the finite extinction ratio of optical pulses, Φ-OTDR based on high extinction ratio generation is studied. Two methods are developed for achieving high extinction ratio of optical pulse generation. One of the approaches is to synchronize two cascaded electro-optic modulators to achieve high extinction ratio operation. The other one is to use the nonlinear optical fiber loop mirror as an optical switch to suppress the continuous wave portion of optical pulse. The sensing range of 1.8 km and 8.4 km with corresponding spatial resolution of 0.5 m and 2 m have been demonstrated based on cascaded two electro-optic modulators and nonlinear optical fiber loop mirror setup, respectively.

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Bolen, Ryan. "A study of optical frequency domain reflectometry and its associated distributed sensor applications". Thesis, University of Ottawa (Canada), 2010. http://hdl.handle.net/10393/28464.

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Optical Frequency Domain Reflectometry (OFDR) is an interferometric technique which is capable of interrogating fibers under test (FUT) up to kilometers in length with millimeter resolution[10]. It does so by taking the Rayleigh backscattered light, or Fresnel back-reflected light and combining it with the reference arm to create a beating signal. The beating signal is then Fourier transformed to create a scattering profile of the FUT. Presented in this thesis are 5 novel OFDR configurations that improve the SNR in the spatial domain up to 26dB. As well, 4 new data analysis algorithms are presented that improve the spectral resolution by up to a factor of 40 and spectral SNR by 1.31dB. The FUT's investigated are regular SMF, linear FBG's, and chirped FBG's. With these, the wavelength shift at specific points along the FUT is measured and correlated with temperature changes (with associated applications), longitudinal stress, and torsional stress stimuli.

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Rizzolo, Serena. "Advantages and limitations of distributed optical-frequency-domain-reflectometry for optical fiber-based sensors in harsh environments". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSES013.

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L’accident de Fukushima-Daiichi du 11 Mars 2011 a fortement marqué l'industrie nucléaire en mettant en évidence plusieurs faiblesses dans le contrôle des systèmes critiques qui assurent la sécurité des centrales nucléaires, en particulier, lors de conditions accidentelles. Cette thèse a été réalisée en collaboration avec AREVA, groupe industriel français actif dans le domaine de l'énergie, avec l’objectif de réaliser des capteurs à fibres optiques résistants aux contraintes sévères d'une centrale nucléaire et, en particulier, de surveiller la température et le niveau de l'eau à l'intérieur d’une piscine de stockage de combustible. La thèse est composée de deux parties organisées en 7 chapitres. Dans la première partie, le chapitre 1 traite des phénomènes contribuant à l'atténuation de la lumière au cours de sa propagation dans la fibre et donne un aperçu des effets des radiations sur les fibres optiques. Pour identifier la technique la plus prometteuse adaptée aux applications visées par AREVA, le chapitre 2 propose un état de l’art sur les capteurs distribués à fibres optiques existants avec une attention particulière à leur emploi dans des environnements radiatifs. La dernière partie de ce chapitre est consacrée à la description détaillée de l’OFDR qui est la technique retenue pour cette application. La deuxième partie est consacrée à la présentation des résultats obtenus et leur analyse. Le chapitre 3 présente le détail des irradiations et des traitements thermiques, les échantillons retenus et les bancs de mesure utilisés. Afin de déterminer la meilleure combinaison fibre/technique par rapport à l’application visée, une étude systématique des capteurs distribués de température et de contrainte a été réalisée. Les effets permanents des rayonnements (niveaux de dose du MGy) sont étudiés dans le chapitre 4. Le chapitre 5 illustre des mesures in situ sur les fibres résistantes aux radiations pour comprendre les effets combinés de la température et des radiations (rayons X), effets représentatifs des conditions nominales et accidentelles des piscines de stockage. Enfin, nous avons développé un prototype de capteur de niveau d’eau pour les piscines de combustible qui est décrit dans le chapitre 6. Ensuite, les principales conclusions et les perspectives de ce travail de thèse sont discutées
Fukushima-Daiichi event on March 11th, 2011, signed a turning point in nuclear industry by highlighting several weaknesses in the control of critical systems that ensure the safety in nuclear power plant (NPP) operating, particularly, in accidentals conditions. This PhD thesis has been carried out in collaboration with AREVA, the French industrial group active in the energy domain, with the aim of realizing optical fiber sensors resistant to the harsh environment constraints of a NPP and, in particular, to monitor temperature and water level several parameters inside the spent fuel pools (SFPs). It consists of two parts organized in 7 chapters. In the first part, chapter 1 deals with the phenomena contributing to the light attenuation during its propagation along the fiber and gives an overview on the radiation effects on optical fibers. To identify the most promising technique suitable for AREVA needs, in chapter 2 is reported the state-of-the-art on the distributed OFSs with particular attention to their employment in radiation environments. The last part of this chapter is devoted to the detailed description of the OFDR that is the selected sensor technique for this application. The second part is devoted to present and discuss the obtained results. Chapter 3 gives the experimental details on radiation and thermal treatments, investigated samples and used setups. In order to determine the best fiber/setup combination, a systematic study on temperature and strain distributed sensors was carried out in relation to the harsh constraints demanded from the application. The permanent radiation (MGy dose levels) effects on different fiber classes are investigated in Chapter 4. Chapter 5 illustrates in situ measurements on radiation resistant fibers to understand the combined temperature and radiation (X-rays) effects representative of the SFP nominal and accidental conditions. Simultaneously, we have developed the OFS design for its integration at SFP facility. The prototype is described and its performance is evaluated in chapter 6. Then, the main conclusion and perspective are discussed
L'incidente di Fukushima-Daiichi dell’11 marzo 2011 ha segnato un punto di svolta per l’industria nucleare, mettendo in evidenza diversi punti deboli nel controllo di sistemi critici che garantiscono la sicurezza nelle centrali, in particolare in condizioni di incidente. Questa tesi è stata condotta in collaborazione con AREVA, il gruppo industriale francese attivo nel settore dell'energia, con l'obiettivo di produrre sensori a fibra ottica resistenti alle condizioni estreme di una centrale nucleare e, in particolare, per controllare diversi parametri all'interno di una piscina di stoccaggio di combustibile nucleare, quali la temperatura e il livello dell'acqua. La tesi si compone di due parti organizzate in 7 capitoli. Nella prima parte, il capitolo 1 riguarda i fenomeni che contribuiscono all'attenuazione della luce durante la sua propagazione nella fibra e permette di comprendere gli effetti della radiazione sulle fibre ottiche. Per identificare la tecnologia più promettente per le esigenze di AREVA, nel capitolo 2 é discusso lo stato dell’arte sui sensori distribuiti con particolare attenzione alle loro performance in ambienti radiativi. L'ultima parte di questo capitolo è dedicato ad una descrizione dettagliata della tecnica OFDR che è la tecnologia scelta per questa applicazione. La seconda parte è dedicata a presentare e discutere i risultati. Il capitolo 3 fornisce i dettagli sui campioni studiati e i trattamenti effettuati su di essi e descrive il setup utilizzato. Per determinare la migliore combinazione fibra/tecnica per l’applicazione prevista, è stato eseguito uno studio sistematico sulla risposta alla radiazione dei sensori distribuiti di temperatura e strain. Glieffetti permanenti della radiazione (dosi dell’ordine del MGy) su diverse classi di fibre, resistenti e sensibili alle radiazioni, sono discussi nel capitolo 4. Il capitolo 5 riporta le misure in situ sulle fibre resistenti alla radiazione per investigare gli effetti combinati di temperatura e radiazioni (raggi X) rappresentativi delle condizioni operative e accidentali nelle piscine di stoccaggio. Infine, abbiamo sviluppato un prototipo di sensore del livello dell’acqua nelle piscine di stoccaggio che è descritto nel capitolo 6. In seguito, le principali conclusioni e le prospettive sono discusse

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Randall, Summer Lockerbie. "Development and utilization of optical low coherence reflectometry for the study of multiple scattering in randomly distributed solid-liquid suspensions /". Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/8672.

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Bergdoll, Greg M. "Characterization of two Vernier-Tuned Distributed Bragg Reflector (VT-DBR) Lasers used in Swept Source Optical Coherence Tomography (SS-OCT)". DigitalCommons@CalPoly, 2015. https://digitalcommons.calpoly.edu/theses/1461.

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Insight Photonic Solutions Inc. has continued to develop their patented VT-DBR laser design; these wavelength tunable lasers promise marked image-quality and acquisition time improvements in SS-OCT applications. To be well suited for SS-OCT, tunable lasers must be capable of producing a highly linear wavelength sweep across a tuning range well-matched to the medium being imaged; many different tunable lasers used in SS-OCT are compared to identify the optimal solution. This work electrically and spectrally characterizes two completely new all-semiconductor VT-DBR designs to compare, as well. The Neptune VT-DBR, an O-band laser, operates around the 1310 nm range and is a robust solution for many OCT applications. The VTL-2 is the first 1060 nm VT-DBR laser to be demonstrated. It offers improved penetration through water over earlier designs which operate at longer wavelengths (e.g. - 1550 nm and 1310 nm), making it an optimal solution for the relatively deep imaging requirements of the human eye; the non-invasive nature of OCT makes it the ideal imaging technology for ophthalmology. Each laser has five semiconductor P-N junction segments that collectively enable precise akinetic wavelength-tuning (i.e. - the tuning mechanism has no moving parts). In an SS-OCT system utilizing one of these laser packages, the segments are synchronously driven with high speed current signals that achieve the desired wavelength, power, and sweep pattern of the optical output. To validate the laser’s fast tuning response time necessary for its use in SS-OCT, a circuit model of each tuning section is created; each laser section is modeled as a diode with a significant lead inductance. The dynamic resistance, effective capacitance, and lead inductance of this model are measured as a function of bias current and the response time corresponding to each bias condition is determined. Tuning maps, spectral linewidths, and side-mode suppression ratio (SMSR) measurements important to SS-OCT performance are also collected. Measured response times vary from 700 ps to 2 ns for the Neptune and 1.2 to 2.3 ns for the VTL-2. Linewidth measurements range from 9 MHz to 124 MHz for the Neptune and 300 kHz to 2 MHz for the VTL-2. SMSR measurements greater than 38 dB and 40 dB were observed for the Neptune and VTL-2, respectively. Collectively, these results implicate the VT-DBR lasers as ideal tunable sources for use in SS-OCT applications.

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Capítulos de libros sobre el tema "Distributed reflectometry"

Pradhan, Himansu Shekhar, P. K. Sahu, D. Ghosh y S. Mahapatra. "Brillouin Distributed Temperature Sensor Using Optical Time Domain Reflectometry Techniques". En Smart Sensors, Measurement and Instrumentation, 207–21. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-42625-9_10.

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Sallem, Soumaya, Ousama Osman, Laurent Sommervogel, Marc Olivas, Arnaud Peltier, Françoise Paladian y Pierre Bonnet. "Wired Network Distributed Diagnosis and Sensors Communications by Multi-carrier Time Domain Reflectometry". En Advances in Intelligent Systems and Computing, 1038–46. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-030-01057-7_77.

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"Principles of Optical Time-Domain Reflectometry (OTDR) for Distributed Sensing". En An Introduction to Distributed Optical Fibre Sensors, 55–106. CRC Press, 2017. http://dx.doi.org/10.1201/9781315119014-4.

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Shishkin, Victor, Kenji Tanaka y Hideaki Murayama. "Proposal on Miniaturization of Distributed Sensing System Based on Optical Frequency Domain Reflectometry". En Advances in Transdisciplinary Engineering. IOS Press, 2019. http://dx.doi.org/10.3233/atde190103.

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The main goal of our research is to develop an integrated photonics circuit for sensing system based on Optical Frequency Domain Reflectometry in order to reduce size, weight and cost of current system. In this work we designed, simulated and fabricated Michelson interferometer integrating components such as adiabatic splitter, loop back mirrors, grating couplers and waveguides on total area 150x410 μm of silicon-on-insulator chip. According to simulation results free spectral range of the interferometer is 0.55 nm. Manufacturing variability was taken into account by performing corner analysis.

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"Distributed strain measurement in steel slab-on-girder bridge via Brillouin optical time domain reflectometry". En Advances in Bridge Maintenance, Safety Management, and Life-Cycle Performance, Set of Book & CD-ROM, 899–900. CRC Press, 2015. http://dx.doi.org/10.1201/b18175-367.

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Actas de conferencias sobre el tema "Distributed reflectometry"

Yoon, Myung-Keun, Daniel F. Dolan y Steve Gabriel. "Time domain reflectometry as a distributed strain sensor". En The 15th International Symposium on: Smart Structures and Materials & Nondestructive Evaluation and Health Monitoring, editado por Masayoshi Tomizuka. SPIE, 2008. http://dx.doi.org/10.1117/12.776224.

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Kreger, Stephen T., Emily Templeton, Daniel Kominsky y Brian Templeton. "Distributed polarization state sensing with optical frequency domain reflectometry". En Fiber Optic Sensors and Applications XVI, editado por Glen A. Sanders, Robert A. Lieberman y Ingrid U. Scheel. SPIE, 2019. http://dx.doi.org/10.1117/12.2519184.

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Xiao, Hu, Huafeng Lu, Zeheng Zhang, Guolu Yin y Tao Zhu. "Distributed pH sensing based on optical frequency domain reflectometry". En 2021 International Conference on Optical Instruments and Technology: Optical Sensors and Applications, editado por Xuping Zhang, Yuncai Wang y Hai Xiao. SPIE, 2022. http://dx.doi.org/10.1117/12.2616491.

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Gorlov, Nikolai I. y Igor V. Bogachkov. "Distributed Fiber-Optic Probing using the Optical Reflectometry Method". En 2022 IEEE International Multi-Conference on Engineering, Computer and Information Sciences (SIBIRCON). IEEE, 2022. http://dx.doi.org/10.1109/sibircon56155.2022.10016922.

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Hu, Zihe, Can Zhao y Ming Tang. "Distributed Optical Phase-sensitive Reflectometry Based on Continuous FrFT-DC Signal". En Optical Fiber Sensors. Washington, D.C.: Optica Publishing Group, 2023. http://dx.doi.org/10.1364/ofs.2023.th6.13.

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Abstract: We propose a phase-sensitive reflectometry using a continuous probe generated by fractional Fourier transform (FrFT) of a direct current signal. High-performance pulse compression is achieved by a single FrFT operation while significantly reducing computational complexity.

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Deng, Yuanpeng, Qinwen Liu, He li, Zhiwei Dai y Zuyuan He. "Quasi-distributed Temperature Sensing with Enhanced Measurement Range Using OFDR and Weak Reflectors". En Optical Fiber Sensors. Washington, D.C.: Optica Publishing Group, 2022. http://dx.doi.org/10.1364/ofs.2022.th4.20.

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We demonstrate a quasi-distributed temperature sensor with optical frequency domain reflectometry (OFDR) and weak reflector array. A temperatrure resolution of 0.3°C is achieved with large measurement range.

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Türker, Volkan, Faruk Uyar, Tolga Kartaloğlu, Ekmel Özbay y İbrahim Özdür. "Long-Range Distributed Acoustic Sensor Based on 3x3 Coupler Assisted Passive Demodulation Scheme". En CLEO: Applications and Technology. Washington, D.C.: Optica Publishing Group, 2022. http://dx.doi.org/10.1364/cleo_at.2022.am3m.3.

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A distributed acoustic sensor based on phase-sensitive optical time domain reflectometry (-OTDR) and passive 3x3 coupler demodulation is demonstrated which is capable of quantifying strain perturbations at 40 km of a sensing fiber.

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Orsuti, Daniele, Arman Aitkulov, Martina Cappelletti, Luca Schenato, Mirko Magarotto, Marco Santagiustina, Cristian Antonelli et al. "Multi-core Fibers as a Technological Platform for Distributed Twist Sensing". En Optical Fiber Sensors. Washington, D.C.: Optica Publishing Group, 2023. http://dx.doi.org/10.1364/ofs.2023.th6.27.

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We show how uncoupled-core multi-core fibers for telecom applications can serve as a technological platform for polarization-based distributed twist sensing. We report successful experimental results based on polarization-sensitive reflectometry on a 500-m-long fiber link.

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Xie, Dongcheng, Xiang Zhang, Yicheng Lin, Cuofu Lin, Jun Yang, Yuncai Wang y Yuwen Qin. "High Accuracy Distributed Birefringence Measurement of Polarization Maintaining Fiber Based on OFDR". En Optical Fiber Sensors. Washington, D.C.: Optica Publishing Group, 2023. http://dx.doi.org/10.1364/ofs.2023.tu3.73.

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We suggest a distributed birefringence measurement method for Polarization-maintaining fiber using Optical Frequency Domain Reflectometry. Method provides a spatial resolution of 5 cm and an uncertainty of 6.8×10-7 at a test distance of 2257 m.

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Shatalin, Sergey V., Vladimir N. Treschikov y Alan J. Rogers. "Interferometric optical time-domain reflectometry for distributed optical fiber sensing". En SPIE's International Symposium on Optical Science, Engineering, and Instrumentation, editado por Ryszard J. Pryputniewicz, Gordon M. Brown y Werner P. O. Jueptner. SPIE, 1998. http://dx.doi.org/10.1117/12.316448.

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