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Snímač úhlové rychlosti se Sagnacovým interferometrem / Angular velocity sensor with Sagnac interferometerSkalský, Michal January 2016 (has links)
This thesis deals with theoretical description of fiber-optic angular velocity sensors, or gyroscopes, and further with design and construction of own sensor of this type. The theoretical part describes problematics of interferometric and resonant fiber-optic gyroscopes. Basic principles and physical limits are described for both types. The main focus is then put on analysis of possible conceptions of these sensors. Solutions using different optical configurations as well as various modulation and signal processing schemes are discussed. The practical part deals with design and construction of own interferometric fiber-optic gyroscope in closed-loop configuration. The gyroscope utilizes all-fiber components including piezoelectric phase modulator and unexpensive single-mode fiber, which are commonly used only for open-loop configurations. To realize closed-loop operation, special modulation scheme based on fully harmonic signal was develeped, which yields linear output within wide dynamic range. This type of modulation requires high level of synchronization achieved by using a field-programmable gate array module. The gyroscope utilizes powerful broadband fiber source, polarizer and Lyot depolarizer which ensure good reciprocity of whole architecture. The parameters of the sensor, obtained by measurement, are even comparable to some sensors using PM fiber, which is much more expensive.
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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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