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Distributed Optical Fiber Vibration Sensor Based on Phase-Sensitive Optical Time Domain ReflectometryRen, Meiqi January 2016 (has links)
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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Study on Supervision of Wavelength Division Multiplexing Passive Optical Network systemsCen, Min January 2011 (has links)
The wavelength-division-multiplexed passive optical network (WDM-PON) offers many advantages such as large bandwidth per user, easy management, high network security and low insertion loss enabling long-reach and/or high split-ratio. However, with the rapid development and growing interest for deployment of WDM-PON, the PON systems are becoming increasingly vulnerable to various failures. Therefore, network supervision becomes extremely important to guarantee an appropriate level of network reliability performance. The aim of PON supervision is to provide automated test and diagnostic capability without compromising the available bandwidth for services. An essential function is to detect any kind of deterioration in the network that can cause suspended services and to remotely localize these faults in order to avoid the high cost arising from troubleshooting. In this thesis, we evaluate several existing WDM PON supervision methods, based on which two simple and cost-effective new solutions are proposed to localize fiber failures in WDM PON systems. In the first solution, a conventional optical time domain reflectometry (OTDR) and a switch unit are employed, while in the second method, a novel architecture based on N×N arrayed waveguide grating (AWG) is proposed. Both methods are able to localize failures in feeder fiber and drop fibers without e.g. using expensive tunable OTDRs. A patent has been filed based on the second solution. The first proposed method is validated by simulations using VPI Transmission Maker. According to the results, this supervision method is able to give accurate measurement of many different types of failures that may happen in a fiber link. Furthermore, VPI is examined in terms of its future applicability in modeling complete PON supervision methods based on OTDR.
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[en] AUTOMATIC HIGH-DYNAMIC AND HIGH-RESOLUTION PHOTON COUNTING OTDR FOR OPTICAL FIBER NETWORK MONITORING / [pt] SISTEMA DE MONITORAMENTO AUTOMÁTICO DE FIBRAS ÓPTICAS POR OTDR DE CONTAGEM DE FÓTONS E MODOS DE ALTA- RESOLUÇÃO/ALTO-ALCANCE06 October 2017 (has links)
[pt] Neste trabalho é apresentado o desenvolvimento de uma estrutura automatizada para o monitoramento de fibras ópticas. Esta estrura consite em dois tipos de reflectômetros ópticos por contagem de fótons no domínio
do tempo e um filtro de tendências que é utilizado para detectar as falhas em uma fibra óptica de forma automatizada. O primeiro OTDR por contagem de fótons apresenta uma faixa dinâmica de 32 dB com resolução espacial de 6 m, já o segundo OTDR apresenta uma faixa dinâmica de 14 dB e uma resolução de 3 cm. Foi demonstrada a sua capacidade de detectar falhas automaticamente em um enlace óptica e de sintonização no monitoramento de redes passivas WDM. / [en] In this work the development of an automated structure for the monitoring of optical fibers is presented. This structure consists of two types of Photon Counting Optical Time Domain Reflectometers and a trend filter
that is used to detect fiber faults in an automated way. The first Photon Counting OTDR has a 32 dB dynamic range with spatial resolution of 6 m, while the second OTDR has a 14 dB dynamic range and a resolution of
3 cm. Its ability to automatically detect faults in an optical fiber link and tunability for monitoring of optical WDM networks has been demonstrated.
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Monitoring Slope Stability Problems Utilizing Electrical and Optical TDRMomand, Farid A. January 2010 (has links)
No description available.
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[en] HIGH RESOLUTION PHOTON COUNTING OPTICAL REFLECTOMETRY / [pt] REFLECTOMETRIA ÓPTICA DE ALTA RESOLUÇÃO POR CONTAGEM DE FÓTONSLUIS ERNESTO YNOQUIO HERRERA 17 October 2016 (has links)
[pt] Neste trabalho são apresentados dois reflectômetros ópticos por contagem
de fótons no domínio do tempo para o monitoramento de fibras ópticas. O
primeiro foi projetado para obter faixas dinâmicas altas. Demonstrou-se a sua
capacidade de sintonização no monitoramento de redes passivas WDM-PON
durante o tráfego de dados. 32 dB de faixa dinâmica com 6 m de resolução foram
atingidos. O segundo reflectômetro foi projetado para atingir resoluções ultra
altas. As aplicações neste caso, além do monitoramento de uma rede TDM-PON
de curto alcance, foram na caracterização de redes de Bragg dispersivas e na
descrição e modelagem de um fenômeno não reportado antes na literatura,
chamado nesta tese de reflexão por curvatura. Foi demonstrada uma resolução
menor que 3 cm com faixa dinâmica maior que 14.0 dB. / [en] This thesis presents the development of two photon counting optical time
domain reflectometers for fiber optic links monitoring. The first one was focused
on high dynamic range. It is demonstrated its tunable capability for a WDM-PON
in-service monitoring. 32 dB on dynamic range and a two-point resolution of 6 m
is achieved. The second reflectometer was design to accomplish an ultra high
resolution. The monitoring of a short TDM-PON is performed. Moreover, due to
its high resolution, a chirped fiber Bragg grating is characterized and a non
previous reported phenomena, the bend reflection, is shaped and described. It is
demonstrated 3 cm two-point resolution and more than 14 dB on dynamic range.
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Modelagem numérica de uma fibra óptica microestruturada para sensoriamento distribuído de pressãoMiraglia, Rodrigo Cesar Ribeiro 20 August 2010 (has links)
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Previous issue date: 2010-08-20 / Fundo Mackenzie de Pesquisa / Sensors based on optical fibers are being increasingly used in hostile environments for measuring pressure, temperature, stress, chemical and biological parameters, etc. These sensors have the advantage of having reduced size and weight, immunity to electromagnetic interference, of being chemically inert, and also allowing the distributed measurement of the respective parameter along the fiber. Microstructured optical fibers have characteristics that are relevant to sensing applications, such as freedom of design of their internal structure obtained by varying the diameter of the holes and the distances between them, among other
parameters, which is not applicable in conventional optical fibers. The present work aims to use a microstructured optical fiber as a distributed sensor for hydrostatic pressure, using the
POTDR (Polarization Optical Time-Domain Reflectometry) and the OFDR (Optical Frequency-Domain Reflectometry) measurement techniques. The application of hydrostatic pressure on the fiber changes its birefringence and, consequently, the evolution of the states of polarization, which is the parameter monitored by the techniques. By monitoring the changes of these states, it is possible to infer the changes in applied pressure. The study is undertaken via simulations and analysis, both performed in the software MatLab. / Sensores baseados em fibras ópticas vêm sendo cada vez mais utilizados em ambientes hostis para medição de pressão, temperatura, stress, análise química e biológica, etc. Esses sensores têm a vantagem de possuírem tamanho e peso reduzidos, imunidade à interferência eletromagnética, de serem quimicamente inertes, e também permitirem a medição distribuída do parâmetro a ser analisado ao longo da fibra. As fibras ópticas microestruturadas possuem características relevantes na aplicação de sensoriamento, tal como a liberdade de construção de sua estrutura interna variando o diâmetro dos buracos e a distância entre eles, entre outros
parâmetros, que não são aplicáveis em fibras ópticas convencionais. Este trabalho tem como objetivo estudar uma fibra óptica microestruturada como sensor distribuído de pressão hidrostática, utilizando as técnicas de medição POTDR (Polarization Optical Time-Domain Reflectometry) e OFDR (Optical Frequency-Domain Reflectometry). A aplicação de pressão hidrostática sobre a fibra altera sua birrefringência e, consequentemente, a evolução do seu estado de polarização, sendo este último o parâmetro monitorado pelas técnicas. Analisando-se a mudança deste estado, pode-se inferir a mudança de pressão aplicada. O estudo é realizado através de simulações e análises efetuadas no software MatLab.
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Simulace monitoringu optické trasy / Simulation of optical route monitoringMlejnek, Zbyněk January 2010 (has links)
Monitoring optical line for a long term monitoring and evaluating both transfer quality and running reliability of optical line links' physical layer (optical cable routes) fiber optical transfer systems. Monitoring indicates any kind of security erosion of transmission medium incited by either "natural" climatic and mechanical environmental effects, indeliberated cable violation (building operation) or by intended intervention into transfer path.
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[en] HIGH-RESOLUTION OTDR WITH EMBEDDED PRECISE FAULT ANALYSIS / [pt] OTDR DE ALTARESOLUÇÃO COM ANÁLISE PRECISA DE FALHAS INTEGRADAFELIPE CALLIARI 16 November 2021 (has links)
[pt] As fibras ópticas são suscetíveis ao estresse mecânico e podem ser
danificadas ou quebradas, portanto, a supervisão da camada física é essencial
para identificar essas falhas e remediá-las o mais rápido possível. Com o objetivo
de agilizar e simplificar o processo de agendamento de unidades de reparo em
campo, foi desenvolvido um sistema automatizado de medição de fibras baseado
em uma unidade de processamento digital de sinal (DSP) capaz de identificar as
posições das falhas de forma autônoma. Combinando esta unidade de DSP com
um OTDR de contagem de fótons, é possível criar tal dispositivo. Este trabalho
apresenta o desenvolvimento dos blocos de construção para tal dispositivo. / [en] Optical fibers are susceptible to mechanical stress and may be damaged
or broken, thus physical layer supervision is essential to identify these failures
and remediate them as quickly as possible. In order to hasten and simplify
the scheduling process of the in-field repairing units, an automated fiber
measurement system based on a digital signal processing (DSP) unit capable
of autonomously identifying fault positions was developed. By combining this
DSP unit with a Tunable Photon-Counting OTDR, it is possible to create such
a device. This work presents the development of the building blocks for such
device.
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[en] EMBEDDED OTDR MONITORING SYSTEMS FOR NEXT GENERATION OPTICAL ACCESS NETWORKS / [pt] SISTEMAS INTEGRADOS DE MONITORAMENTO POR OTDR PARA REDES DE ACESSO ÓPTICO DE PRÓXIMA GERAÇÃO12 December 2017 (has links)
[pt] Para suportar os requisitos das redes móveis de 5a geração (5G), os
sistemas de comunicação óptica serão usados nas redes de acesso. Isso ocorre
porque a evolução das RAN (Radio Access Networks) incluem a centralização
do equipamento mais crítico para implantar pontos de acesso móveis de
baixa potência, como DAS (Distributed Antenna Systems) e Small Cells. Os
serviços emergentes solicitam a implantação de tecnologias de rádio sobre fibra
com ênfase na eficiência de largura de banda, eficiência energética e alta
confiabilidade. Neste âmbito, um monitoramento eficiente da camada física
é imperativo para a operação dessas redes. O sistema de monitoramento
deve fornecer uma localização de falhas em serviço, econômico, centralizado
e com impacto mínimo para a transmissão de dados. Esta tese propõe vários
sistemas de monitoramento incorporado no transceptor utilizando reflectometria
óptica no domínio do tempo. Os sistemas de monitoramento são
testados em diferentes sistemas de transmissão de dados e arquiteturas de
rede, onde é apresentada uma validação simulada e outras experimentais. / [en] In order to support the requirements for 5th generation mobile networks (5G), optical communication systems will be used in the access part of the network. This is because the evolution of radio access networks includes the centralization of the most critical equipment in order to deploy low power mobile access points, like distributed antenna systems and small cells. The emerging services call for the deployment of radio over fibre technologies with emphasis on bandwidth efficiency, energy efficiency and high reliability. Within this scope, an efficient monitoring of the physical layer would become essential for the operation of these networks. The monitoring system should provide in-service, cost efficient and centralized fault localization with minimum impact on data transmission. This thesis proposes
several transceiver-embedded optical time domain reflectometry monitoring systems. The monitoring systems are tested over different data transmission systems and network architectures, where one architecture was simulated and several others experimentally validated.
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[pt] LASERS DE FIBRA DE MODO TRAVADO PARA REFLECTOMETRIA ÓPTICA NO DOMÍNIO DO TEMPO E SENSORIAMENTO / [en] MODE-LOCKED FIBER LASERS FOR OPTICAL TIME-DOMAIN REFLECTOMETRY AND SENSINGMARLON MEDEIROS CORREIA 16 May 2023 (has links)
[pt] Diferentes tipos de lasers podem ser usados para gerar pulsos de luz com
uma ampla faixa de durações de pulso, energias e potências de pico. As técnicas
de Q-switching e mode-locked são relatadas há anos por vários autores e
pesquisadores e são frequentemente utilizadas na geração de lasers de pulso
ultracurto com duração de pulso no domínio do tempo na faixa de nanossegundos
até femtossegundos. Uma configuração, com ganho fornecido por um
amplificador óptico semicondutor (SOA) e amplificador de fibra dopada com
érbio (EDFA) é proposta e emprega a técnica de gerenciamento de dispersão para
gerar um trem de pulsos ópticos exibindo alta potência de pico, taxa de repetição
ultra-baixa e largura temporal curta, habilitando que este laser seja usado como
uma fonte para aplicações de alta resolução em reflectometria óptica no domínio
do tempo (OTDR). A operação mode-locked é conhecida por ocorrer apenas em
lasers ordenados padrão por um longo tempo e até recentemente foi encontrado
também em lasers de fibra aleatórios desordenados (RFL). Embora tenha havido
progresso no sentido de travar modos espaciais e longitudinais em lasers
aleatórios, a literatura carece de relatos sobre geração de pulsos limitada por
transformada de Fourier, apesar das muitas décadas de campo. O autor demonstra
experimentalmente um mode-locked random fiber laser (MLRFL) operando como
um refletômetro óptico de domínio do tempo sensível à fase. Aqui, a
saída total do laser fornece o sinal de detecção, em contraste com o pequeno sinal
retroespalhado medido em um OTDR convencional. O laser opera como um
sensor acústico distribuído (DAS) e sensor de temperatura distribuído (DTS). / [en] Different types of lasers can be used to generate light pulses with a wide
range of pulse durations, energies and peak powers. Q-switching and mode-locked
techniques have been reported for years by several authors and researchers and are
frequently used in the generation of ultra-short-pulse lasers with time-domain
pulse durations from the nanosecond to femtosecond range. A configuration, with
gain provided by a semiconductor optical amplifier (SOA) and erbium-doped
fiber amplifier (EDFA) is proposed and employ the dispersion management
technique to generate a train of optical pulses exhibiting high-peak-power, ultralow repetition rate, and fast temporal width, enabling this laser to be used as a
source for high-resolution optical time domain reflectometer (OTDR)
applications. The mode-locking operation has been known to occur only in
standard ordered lasers for a long time and until recently it was found to also
occur in disordered random fiber lasers (RFL). Although progress has been made
towards locking spatial and longitudinal modes in random lasers, the literature
lacks reports on Fourier transform-limited pulse generation despite the many
decades of the field. The author experimentally demonstrates a mode-locked
random fiber laser (MLRFL) operating as a lasing phase-sensitive optical time domain reflectometer based on random feedback from a sensing fiber.
Here, the full output of the laser provides the sensing signal, in contrast to the
small backscattered signal measured in a conventional OTDR. The laser operates
as a distributed acoustic sensor (DAS) and distributed temperature sensor (DTS).
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