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Monitorização de estruturas de engenharia baseada em redes de Bragg em fibra óptica : contribuição para a optimização de dois sistemas de interrogaçãoAlves, Joaquim Fernando Almeida January 2007 (has links)
Tese de doutoramento. Ciências de Engenharia. Faculdade de Engenharia. Universidade do Porto. 2007
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[en] BRAGG GRATING IN OPTICAL FIBERS AND APPLICATIONS / [pt] REDES DE BRAGG EM FIBRAS ÓPTICAS E APLICAÇÕESLILIANA ROCHA KAWASE 07 June 2006 (has links)
[pt] O objetivo principal deste trabalho foi o de estudar as
redes de Bragg em fibras ópticas e suas principais
aplicações, com especial interesse na compensação de
dispersão de pulsos ópticos em sistemas de
telecomunicações, onde uma implementação original foi
construída.
Faz-se uma revisão geral das técnicas existentes para
fabricá-las e caracterizá-las, além de suas principais
aplicações, não somente na área de telecomunicações mas
também na área sensoriamento óptico.
São mostrados os resultados experimentais obtidos nas
montagem realizadas para escrever redes de Bragg em fibras
ópticas e para caracterizá-las. Algumas experiências
usando redes de Bragg para o controle do comprimento de
onda de emissão de um laser de semicondutor e para medição
de força aplicada numa estrutura são mostradas.
São mostrados também os resultados experimentais inéditos
obtidos com a compensação de dispersão de pulsos ópticos
em enlaces de telecomunicações, onde várias montagens
foram realizadas para comprovar a superioridade da
utilização da redes de Bragg para esse fim. Demonstra-se
também um sistema para gerar pulsos solitônicos
sintonizável em comprimento de onde numa faixa de MHZ.
Finalmente são mostrados os resultados obtidos com a
utilização de fibras ópticas para chaveamento
interferométrico de luz. Neste sistema são utilização como
elemento óptico não linear fibras tipo D, com e sem redes
de Bragg, revestidas com filme de materiais semicondutores
amorfos. / [en] Bragg grating in optical fibers are used to compensate the
dispersion of optical pulses in telecommunication systems.
Initially, an overview is presented of the existing
fabrication techniques of such gratings, as well as the
techniques used for characterization. Some useful
applecations in telecommunications and sensing are also
shown.
The results obtained in the set-up to write and to
characterize Bragg gratings are presented. Some
measurements were also done with typical applications such
as controlling the emitting wavelength in semiconductors
lasers, and monitoring the applied pressure in an optical
fiber.
Some new results are described on dispersion compensation
in fibers. Using specially chirped Bragg gratings to pre-
compensatedispersion of an optical pulse in a 80 km fiber
link, we demonstrated that the poor quality of the input
laser pulses has little impact on the duration of the
pulses recovered after transmission.
Finally, an interferometric switching arrangement using a
semiconductor coated D fiber as nonlinear control element,
is presented. The configuration uses infrared optical
pulses to control a continuous wave light signal. It is
also shown that the original reflected wavelength of a
semiconductor coated D-fiber with Bragg grating can be
shited with an external optical control signal.
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Leitura de redes de Bragg por modulação óticaOliveira, Valmir de 2010 October 1914 (has links)
Neste trabalho é apresentado um sistema de leitura de redes de Bragg derivado da
técnica por filtro Fabry-Perot sintonizável. A técnica apresentada é implementada através
de um sistema atuador piezelétrico que modula mecanicamente uma rede de Bragg de
referência, com seu espectro de reflexão convoluido com o espectro de reflexão de uma
rede sensora. A técnica desenvolvida apresenta vantagens em relação ao processo original por ter implementação mais simples, menor custo e melhor discriminação de posição espectral. / This work presents a process to detect Bragg grating spectra based on the tunable
Fabry Perot filter technique. The apparatus is assembled with a piezoelectric actuator that
mechanically modulates a reference Bragg grating. The spectrum of that grating is
convoluted with the spectrum of the sensor during a sweep. The device presents some
advantages as, eg., simplicity, lower cost and better discrimination for the spectral position of the reflected band.
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[en] DISPERSION COMPENSATION USING OPTICAL FIBRE CHIRPED BRAGG GRATTINGS / [pt] COMPENSAÇÃO DE DISPERSÃO CROMÁTICA COM O EMPREGO DE REDES DE BRAGG EM FIBRA COM CHIRPWALDEMAR ROBERTO RUZISCKA 09 November 2006 (has links)
[pt] A utilização de redes de Bragg com chirp em fibra, para
compensação dos efeitos da dispersão cromática, é uma
técnica promissora que permite o aumento progressivo da
capacidade de canalização dos sistemas ópticos. Dentre as
diversas técnicas para a compensação da dispersão, sendo
propostas nos tempos correntes, o emprego da rede de
Bragg
em fibra tem se mostrado o mais exequível em virtude de
serem passivas, relativamente fáceis de fabricar, de boa
reprodutibilidade e alto grau de integrabilidade aos
sistemas.
Este trabalho mostra a aplicação desse dispositivo em
experimentos de compensação de dispersão com o emprego de
modulação direta e externa em diferentes taxas de
transmissão. / [en] The use of in-fibre Bragg gratings with dispersion
compensating purposes, is a promissing technique for the
increasing optical systems bitrate pace development. Among
the various dispersion compensation techniques, in-fibre
Bragg gratings had proven, to be the most feasible. They
are passive, higly reproducible, relatively easy to
fabricate at reasonable costs and have a good degree of
integrability. This dissertation exploits significant
aspects of the Bragg fibre grating fabrication and its
employment as dispersion compensation device.
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Multimode Optical Fiber Bragg Gratings: Modeling, Simulation and ExperimentsZhang, Jinsong 05 1900 (has links)
Telecommunication networks based on optical fiber technology have become a major information-transmission system, satisfying the growing demand for bandwidth due to increased internet traffic and other applications such as video on demand, etc. Fiber Bragg gratings (FBGs), in recent years, have emerged as critical components for enabling high-capacity transmission since their response can be tailored to meet the needs of specific applications. FBGs are currently the focus of intense research interest in both the fiber communications and sensing fields. Optical fiber Bragg grating structures in single-mode fiber (SMFBGs) have been studied extensively since the discovery of photosensitivity in germanium-doped silica fiber. They have been used in numerous applications ranging from wavelength-selective filtering in wavelength-division-multiple-access (WDMA) systems to temperature and strain sensing. To a lesser extent, Bragg gratings in multimode fibers have also received attention because of easy coupling with light sources. Most of the MMFBGs related research work has demonstrated the formation of a Bragg grating in a graded-index MMF and briefly reported the measured transmission spectrum. So far, there are few theoretical studies on Bragg gratings in multimode fibers. In this thesis, we investigate Bragg gratings in multimode optical fibers both theoretically and experimentally. A comprehensive numerical model for MMFBGs has been established and the corresponding computer simulation software (MMFBG simulator combined with mode solver) developed. The optical properties of MMFBGs were systematically studied for the first time using our own MMFBG numerical software package. It effectively assists the design modeling for MMFBG-based optical devices. Bragg gratings in multimode fiber were also investigated experimentally. Our theoretical simulation results show good agreement with experiments and offer the insightful explanations for the underlying physics of the device. First, the guided modes were modeled and simulated for step index multimode fibers and graded index multimode fibers with emphasis on parabolic fiber structure. These are popular, standard and commercially available MM fibers, and employed throughout our experiments. This allows us for the simulation of fiber characteristics such as cut-off wavelength, mode effective index, propagation constants and optical field distribution. It also allows for calculation of mode coupling coefficients by overlap integral between any chosen guided modes. Therefore, it serves as a powerful model for the design and analysis of optical fibers. Second, the generalized MMFBG coupled mode theory formalism is derived. The physical mechanism of the behavior of MMFBGs is studied and discussed. The general solution to the MMF Bragg grating problem is achieved by Runge-Kutta, Newton-Raphson and shooting numerical methods. Our theoretical treatment, in particular, offers the advantages which can deal with not only self-coupling but also more complicated cross-coupling interactions and can solve arbitrary large number of mode coupling problems throughout the entire spectra simultaneously for multimode FBGs, thus allowing for a precise and quantitative study of MMFBGs. Such an intensive multimode fiber Bragg grating physical modeling and simulations have not been reported previously. It provides an effective means for the design and analysis of optical fiber devices based on Bragg gratings. Third, the optical properties of multimode FBGs were studies experimentally. Numerical predications of the grating spectral characteristics under fabrication and experimental condition are calculated. The results of the numerical calculations are compared with experimentally measured spectra of multimode gratings written by ultraviolet irradiation of deuterium-sensitized fiber with grating reflectivities ranging from 78% to 99.39%. Good agreement is obtained between the theoretical simulations and the experimental results. Thus, we provide quantitative explanations for the observed experimental phenomena. These explanations give both physical insight and a more complete understanding of the nature of the interaction between the wave propagation and multimode fiber gratings. Furthermore, the spectral simulation of the actual experiments prepares a theoretical guidance for the advanced experimental investigation and also presents a step toward MMFBG device design. Finally, the optical properties of MMFBGs were also studied theoretically. To our knowledge, this is the first detailed analysis and thorough investigation on grating characteristics in MMF. It is demonstrated that the transmission and reflection spectra of fiber Bragg gratings in multimode optical fibers strongly depend on the length of grating, index modulation, period of grating, mode excitation condition and physical structure of MMF. The simulation results allow us to deeply comprehend and visualize the more sophisticated behavior within a multimode fiber grating, and will also allow us to confidently predict and evaluate the performance of more complex structure MMFBGs. It provides the fundamental principles for designing the targeted spectrum performance and settles the theoretical rationale for realizing the practical applications. Overall, the comprehensive numerical model and MMFBG solver package developed in this thesis opens a clear and broad window for understanding MMFBG mechanisms from the physical point of view. Various simulation results and spectral characteristics have been researched and discussed under both ideal and experimental conditions for the purpose of experimental analysis and device design. The results of our study indicate that a new class of potential applications based on MMFBGs can be expected in optical fiber sensors and advanced communication systems. / Thesis / Master of Applied Science (MASc)
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Fabrication of SMR Filter and Its Thermal Annealing TreatmentWen, Jau-Yu 17 August 2009 (has links)
In this study, 1/2 £f mode SMR filters on Si substrates by reactive RF magnetron sputtering method were fabricated. In addition, the thermal annealing process was adopted to improve the insertion loss of SMR filter.
The Bragg reflector in SMR is alternately mounted by high and low acoustic impedance materials, with low acoustic impedance material of SiO2 and high acoustic impedance material of W. We could obtained three kinds of crystal structures of W, £\ - phase W¡B£] - phase W and £\ & £] - mixed phase W, respectively, it could be obtained by modulating the sputtering recipe. £\ - phase W possesses higher acoustic impedance and is suitable for high acoustic impedance material in bragg reflector.
The piezoelectric layer of ZnO is sputtered by a 2-step deposition method on Si substrates with different temperature. The ZnO film with stronger C-axis (002) orientation and lower surface roughness value could be obtained at substrate temperature of 200 ¢J, which is suitable for fabricating SMR device.
After the SMR filter had completed, the device is thermal annealed with CTA¡BRTA and RTA in O2 ambient. After thermal treatment, the properties of filters are improved. The properties could be optimized with RTA in O2 ambient condition. The insertion loss was improved from -12.03 dB to -6.96 dB. The film characteristics of ZnO changes after the SMR processed thermal treatment. The strongest C-axis (002) intensity with the lowest surface roughness value at 400 ¢J annealing temperature could be obtained, in that, approximate equal Zn:O ratio could be achieved by XPS examination.
The central frequency of SMR filter drifted to higher value as the temperature of thermal treatment increased, which is attributed to the changes of the ZnO acoustic velocity(£o) after thermal treatment.
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Dense spectral beam combining with volume Bragg gratings in photo-thermo-refractive glassAndrusyak, Oleksiy G. January 2009 (has links)
Thesis (Ph.D.)--University of Central Florida, 2009. / Adviser: Leonid B. Glebov. Includes bibliographical references (p. 142-151).
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Femtosecond laser inscribed fiber Bragg grating sensorsZhan, Chun. January 2007 (has links)
Thesis (Ph.D.)--Pennsylvania State University, 2007. / Mode of access: World Wide Web.
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Herstellung photonischer Komponenten durch Heissprägen und UV-induzierte Brechzahlmodifikation von PMMABründel, Mathias January 2008 (has links)
Zugl.: Karlsruhe, Univ., Diss., 2008 / Hergestellt on demand. - Auch im Internet unter der Adresse http://uvka.ubka.uni-karlsruhe.de/shop/isbn/978-3-86644-221-4 verfügbar
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Herstellung photonischer Komponenten durch Heissprägen und UV-induzierte Brechzahlmodifikation von PMMABründel, Mathias. January 2008 (has links)
Zugl.: Karlsruhe, Universiẗat, Diss., 2008.
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