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1
Bollond, Paul. "Picosecond Pulse Generation and Propagation in Erbium Doped Optical Fibres." Thesis, University of Auckland, 1997. http://hdl.handle.net/2292/1983.
Texte intégralRésumé :
This thesis is concerned with the generation of picosecond pulses and their propagation through both resonant and non-resonant media. This was achieved by constructing a passively modelocked Erbium doped fibre laser (EDFL) which was used to study pulse propagation through sections of standard communications grade optical fibre, dispersion shifted optical fibre, and also through an Erbium doped fibre amplifier (EDFA) module. The EDFL produced a train of ˜2 psec pulses at 4 MHz, tunable over the erbium gain band ( 1520 - 1570 nm). The laser was constructed from commercially available components and had the property of stability combined with low pump power requirements to produce ˜50 Watt peak power pulses. The laser cavity geometry included a nonlinear optical loop mirror, which has the property of efficiently switching high peak power pulses, and allowed pulsed operation without the aid of any high-speed electronics. An EDFA module of identical geometry to that used in the laser was also constructed, and this was probed using the pulses from the EDFL. The traditional temporal and spectral measurements were found to be inadequate to allow a complete description of the pulse amplification process to be developed. To overcome this problem the technique of frequency resolved optical gating (FROG) was applied for the first time to optical fibre research, and allowed an indirect measurement of the electric field of the pulse. This complete description of the pulse was used in a numerical model to describe pulse propagation in an optical fibre. Fundamental propagation terms in the model were treated as free parameters in a minimisation scheme, which could be determined for a fibre under examination. This technique was shown to be accurate when used to examine pulse propagation through both standard and dispersion shifted optical fibre. A comprehensive numerical model was developed for the EDFA, and it was apparent from this model that a pulse propagating through an optimised EDFA encounters an atomic inversion distribution which is a strong function of distance along the amplifying fibre. It was also shown from the experimental results that the EDFA exhibited resonant dispersion, which is characteristic for propagation through an atomic medium on resonance.
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Males, Mladen. "Suppression of transient gain excursions in an erbium-doped fibre amplifier /." Connect to this title, 2006. http://theses.library.uwa.edu.au/adt-WU2007.0157.
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Males, Mladen. "Suppression of transient gain excursions in an erbium-doped fibre amplifier." University of Western Australia. School of Electrical, Electronic and Computer Engineering, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0157.
Texte intégralRésumé :
This thesis reports original work on suppression of transient gain excursions in an erbium-doped fibre amplifier (EDFA). The work presented in this thesis is a detailed investigation of four closed-loop systems that control the EDFA gain dynamically. The performance of the four closed-loop systems is evaluated by analytical work, supplemented by computer simulations and insystem measurements performed on a hardware EDFA. In addition, a stability analysis of the four closed-loop systems is presented. In the stability analysis presented in this thesis, nonlinear nature of the four closed-loop systems is taken into consideration. In the stability analysis, in addition to proving that the four closed-loop systems considered are stable, it is proven that for any practical values of the EDFA gain at the initial time of observation, the EDFA gain is restored to the desired value in steady state. These outcomes of the stability analysis are supported by simulation results and experimental results. Errors in system modelling, change in the operating point of the nonlinear closed-loop system, and measurement noise are important aspects of practical implementations of systems that control the EDFA gain dynamically. A detailed analysis of the effects these practical aspects have on the performance of the four closed-loop systems considered is presented. The analysis is validated using computer simulations and experimental measurements. In most of the work reported in the literature on controlling the EDFA gain, controllers that include feedforward and/or feedback components are employed. In the traditional approaches to combining the feedforward and the feedback components, large transient excursions of the EDFA gain can still occur due to errors in the control provided by the feedforward component. In this thesis, a novel approach to combining the feedforward and the feedback components of the controller is presented. Based on the analytical work, the computer simulations and the experimental work presented in this thesis, the novel approach provides a significant reduction in the excursions of the EDFA gain in the transient period.
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Cheney, Glenn P. (Glenn Peter) Carleton University Dissertation Engineering Electrical. "All-optical gain switching of erbium-doped fibre amplifiers." Ottawa, 1992.
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Hoffman, Mark Brandon. "Sub-picosecond pulse propagation in an erbium-doped fiber amplifier with ion-induced dispersion." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/14961.
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Da, Rosa Marcelo Zannin. "Optical gain clamping in erbium doped fibre amplifier : investigation in optical burst switching networks." Thesis, Swansea University, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.678524.
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Dimopoulos, C. "Study of dynamic phenomena in WDM optical fibre links and networks based on EDFAs." Thesis, University of Essex, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327071.
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Altuncu, Ahmet. "Distributed erbium doped fibre amplifiers (DEDFAs) for use in long haul and high bit rate soliton transmission systems." Thesis, University of Essex, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388156.
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Wijaya, Shierly. "Fixed-point realisation of erbium doped fibre amplifer control algorithms on FPGA." University of Western Australia. School of Electrical, Electronic and Computer Engineering, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0132.
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The realisation of signal processing algorithms in fixed-point offers substantial performance advantages over floating-point realisations. However, it is widely acknowledged that the task of realising algorithms in fixed-point is a challenging one with limited tool support. This thesis examines various aspects related to the translation of algorithms, given in infinite precision or floating-point, into fixed-point. In particular, this thesis reports on the implementation of a given algorithm, an EDFA (Erbium-Doped Fibre Amplifier) control algorithm, on a FPGA (Field Programmable Gate Array) using fixed-point arithmetic. An analytical approach is proposed that allows the automated realisation of algorithms in fixedpoint. The technique provides fixed-point parameters for a given floating-point model that satisfies a precision constraint imposed on the primary output of the algorithm to be realised. The development of a simulation framework based on this analysis allows fixed-point designs to be generated in a shorter time frame. Albeit being limited to digital algorithms that can be represented as a data flow graph (DFG), the approach developed in the thesis allows for a speed up in the design and development cycle, reduces the possibility of error and eases the overall effort involved in the process. It is shown in this thesis that a fixed-point realisation of an EDFA control algorithm using this technique produces results that satisfy the given constraints.
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Goel, Nitin Kumar. "Development of "Core-Suction" Technique for Fabrication of Highly Doped Fibers for Optical Amplification and Characterization of Optical Fibers for Raman Amplification." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/29302.
Texte intégralRésumé :
This thesis presents a novel technique named "Core Suction" for fabricating optical fiber preforms for manufacturing highly doped fibers (HDFs) for optical amplification (Raman effect based or Erbium fiber based). The technique involves drawing the molten non-conventional core glass material into the silica cladding tube to form the preform. The developed technique is simple, inexpensive and shows great potential for fabricating preforms of highly nonlinear non-conventional multi-component glasses as the core material. Preforms were made with various core glasses such as Schott SF6, Lead-Tellurium-Germanate, Lead-Tellurium-Germanate- Neodymium -Erbium and MM2 in silica cladding tubes and then pulled into fibers.
The fabricated fibers were measured for refractive index profile, loss spectrum and spontaneous Raman spectra. Elemental analysis of the fiber samples was also performed using an electron microprobe. Erbium doped fiber amplifiers (EDFAs) were setup using 30 cm, 5cm and 1 cm lengths of fabricated erbium doped fibers and their gain spectra measured. The distributed gain spectrum for an EDFA was also measured using an optical frequency domain reflectometery (OFDR) technique. Commercial dispersion compensated fiber (DCF) with very high GeO2 doping was used to setup a Raman amplifier and the gain spectrum measured.
One of the needs of Raman amplification in optical fibers is to predict an accurate Raman gain, based on the fiber's refractive index profile. A method of predicting Raman gain in GeO2 doped fibers is presented and the predicted Raman gain values are compared with the measured ones in the same fibers. Raman gain issues like the dependence of the Raman gain on the GeO2 concentration, polarization dependence were taken into account for the gain calculations. An experimental setup for Raman gain measurements was made and measurement issues addressed. Polarization dependence of the Raman gain in one kilometer of polarization maintaining fiber was also measured.<br>Ph. D.
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Montes, Thisien Gabriel 1988. "Caracterização experimental de fibras de vidro telurito dopado com érbio e itérbio : Experimental characterization of tellurite glass fibers doped with erbium and ytterbium." [s.n.], 2015. http://repositorio.unicamp.br/jspui/handle/REPOSIP/261920.
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Orientador: Aldário Chrestani Bordonalli<br>Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação<br>Made available in DSpace on 2018-08-27T14:08:20Z (GMT). No. of bitstreams: 1
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Previous issue date: 2015<br>Resumo: Com a demanda por comunicação continuamente aumentando nos últimos anos, mantém-se constante a busca por aperfeiçoamento dos amplificadores ópticos a fibra. Como uma proposta de proporcionar maior largura de banda de amplificação para sistemas ópticos, este trabalho procura caracterizar o comportamento operacional de uma fibra de vidro telurito dopado com érbio e itérbio para diferentes condições iniciais de comprimento de amostra, aplicação de sinais e configuração de bombeio. As amostras, fabricadas pelo Grupo de Fibras Ópticas do IFGW/UNICAMP, foram submetidas a análises experimentais baseadas nas principais topologias de amplificadores a fibra que usam matrizes de sílica. Assim, avalia-se a potencialidade das características de amplificação do vidro telurito fabricado com dosagem de compostos inéditos, além de uma investigação da possibilidade da geração laser utilizando-se essa fibra como meio ativo em configurações com laço de realimentação. Mesmo que o ganho real do sistema não tenha sido determinado pela incerteza em relação a real potência óptica acoplada às amostras, observou-se ser possível a compensação da atenuação que o sinal que se propaga pelas amostras sofre após a aplicação de bombeio. Nesse aspecto, o vidro telurito dopado com érbio e itérbio apresentou potencial de aplicação em amplificação óptica. Uma amostra de 2 cm, comprimento muito menor que o usado em amplificadores ópticos baseados em matrizes de sílica e uma ordem de grandeza menor que os baseados em vidro telurito dopado apenas com érbio, apresentou resultados de ganho óptico on-off da ordem de 30 dB com bombeio bi-direcional de 100 mW. Em relação ao vidro telurito dopado apenas com érbio, os resultados para o ganho on-off chegaram a ser até 15 dB maiores. Além disso, as transições providas pela interação entre a matriz vítrea com o érbio e o itérbio levaram a larguras de banda de 3 dB para o espectro de ASE de até 70 nm, dependendo da configuração de bombeio<br>Abstract: With the recently increase in data transmission demands, the search for improved fiber amplifier physical processes, materials, and configurations is still on going. As a way to provide a wider amplification bandwidth for optical systems, this work intends to characterize the operational behavior of an erbium and ytterbium doped tellurite fiber for different sample lengths, light coupling and pump configurations. The fiber samples, manufactured by the Optical Fiber Group of the IFGW/UNICAMP, underwent experimental analyses based on the same main pump topologies as those of silica-based optical amplifiers. Thus, the potential amplification characteristics of tellurite glass doped with new compounds are evaluated, as well as an investigation of possible laser generation by using this type of fiber as gain medium within feedback loop configurations. Although real system gain was impossible to determine due to uncertainties in the actual coupled optical power, it was observed that the attenuation during signal propagation through the fiber samples could be compensated after pump application. In this context, the erbium and ytterbium doped tellurite fiber has potential for optical amplification. Samples as short as 2 cm, far shorter than the ones used in silica based amplifiers and one order of magnitude shorter than those based on Er3+ doped tellurite fiber structures, presented on-off optical gain of the order of 30 dB for bi-directional 100-mW pump. By comparing with the latter doped glass structure, the on-off gain results were as high as 15 dB greater. Furthermore, the transitions provided by the interaction between the host glass and both erbium and ytterbium have led to a 70-nm ASE bandwidth, depending on the pumping configuration<br>Mestrado<br>Telecomunicações e Telemática<br>Mestre em Engenharia Elétrica
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Verlinden, Nicholas H. P. "The excited state absorption cross section of neodymium-doped silica glass fiber in the 1200-1500 nm wavelength range." Worcester, Mass. : Worcester Polytechnic Institute, 2008. http://www.wpi.edu/Pubs/ETD/Available/etd-072508-145557/.
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Pourbahri, Babak. "Erbium-doped fibre amplifiers and their effects on the phase noise of optical carriers and radio-over-fibre signals." Thesis, University of Kent, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369689.
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Turghun, Matniyaz. "Free-space NPR mode locked erbrium doped fiber laser based frequency comb for optical frequency measurement." Thesis, Kansas State University, 2014. http://hdl.handle.net/2097/18682.
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Master of Science<br>Department of Physics<br>Brian R. Washburn<br>This thesis reports our attempt towards achieving a phase stabilized free-space nonlinear polarization rotation (NPR) mode locked erbium doped fiber laser frequency comb system. Optical frequency combs generated by mode-locked femtosecond fiber lasers are vital tools for ultra-precision frequency metrology and molecular spectroscopy. However, the comb bandwidth and average output power become the two main limiting elements in the application of femtosecond optical frequency combs.
We have specifically investigated the free-space mode locking dynamics of erbium-doped fiber (EDF) mode-locked ultrafast lasers via nonlinear polarization rotation (NPR) in the normal dispersion regime. To do so, we built a passively mode-locked fiber laser based on NPR with a repetition rate of 89 MHz producing an octave-spanning spectrum due to supercontinuum (SC) generation in highly nonlinear fiber (HNLF). Most significantly, we have achieved highly stable self-starting NPR mode-locked femtosecond fiber laser based frequency comb which has been running mode locked for the past one year without any need to redo the mode locking.
By using the free-space NPR comb scheme, we have not only shortened the cavity length, but also have obtained 5 to 10 times higher output power (more than 30 mW at central wavelength of 1570 nm) and much broader spectral comb bandwidth (about 54 nm) compared to conventional all-fiber cavity structure with less than 1 mW average output power and only 10 nm spectral bandwidth.
The pulse output from the NPR comb is amplified through a 1 m long EDF, then compressed by a length of anomalous dispersion fiber to a near transform limited pulse duration. The amplified transform limited pulse, with an average power of 180 mW and pulse duration of 70 fs, is used to generate a supercontinuum of 140 mW. SC generation via propagation in HNLF is optimized for specific polling period and heating temperature of PPLN crystal for SHG around 1030 nm.
At last, we will also discuss the attempt of second harmonic generation (SHG) by quasi phase matching in the periodically polled lithium niobate (PPLN) crystal due to nonlinear effect corresponding to different polling period and heating temperature.
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Šustr, Pavel. "Optický zesilovač v laboratorní výuce." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-218165.
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The aim of this thesis is to introduce to reader the application and use of optical EDFA amplifiers in optical transmission and to show wiring and practical test, including measurements on amplifier. The aim of this thesis is to propose the use of optical amplifier in laboratory practice for subject Optical networks. The thesis briefly introduces the problems of data transmissions through optical fibers with a focus on the use of optical amplifiers. The basic characteristic of optical transmission paths and the reasons for the use of optical amplifiers are described here. One entire chapter is devoted to distinction of optical amplifiers. Amplifiers can be divided according to location in the transmission path to the booster, in-line and pre-amplifiers and according to the used of amplifying technology to optical amplifiers with subsidies, semiconductor optical amplifiers and Raman optical amplifiers. The factors affecting the efficiency of optical amplifiers, such as noise and the level of saturated power are mentioned here too. The different types of optical amplifiers from the two producers are also described. From these amplifiers was chosen EDFA CzechLight Amplifier from Optokon to be used for the laboratory exercise in the subject of Optical networks. The use of EDFA optical amplifiers in optical transmission lines is mentioned here too. These amplifiers can be used in telecommunications transmission systems and for data transmission over long distances. They will find use in WDM transmission systems and cable TV distribution through the optical fiber to the end users. Practical measurements were performed on optical amplifier CLA-PB01F. In the transmission route was located attenuator and the dependence of output power to input signal power was measured. The amplification course was linear in the range of input values provided by the manufacturer. Laboratory exercise for the subject of Optical networks is aimed at preacquaintance of students with problems EDFA optical amplifiers and practical measurements with the optical amplifier CLA-PB01F. Students acquire basic theoretical knowledge of the issue and verify the functionality of optical amplifiers on a specific exercise. This work is destined for all who wish to get basic knowledge of optical amplifiers, their characteristics and possibilities of their use in optical transmission lines.
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Michel, David Daniel. "Linear-cavity tunable fibre lasers employing an Opto-VLSI processor and a MEMS-based device." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2012. https://ro.ecu.edu.au/theses/520.
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This thesis proposes and demonstrates experimentally two novel linear-cavity tunable fibre lasers employing an erbium-doped fibre (EDF) in conjunction with an Opto- VLSI processor and a MEMS-based device for wavelength selection. The Opto-VLSI processor and the MEMS-based device along with an optical collimator, a Bragg grating plate and an optical lens, enable the realisation of an optical filter for continuous tuning of wavelengths over the amplified spontaneous emission (ASE) range of the EDF. We also propose the use of a section of un-pumped EDF as a saturable absorber (SA), which suppresses noise spikes caused by the high optical pumping power. Experimental results show that by optimising a length of the SA a single wavelength, high power laser signal can be achieved. In addition, we experimentally demonstrate that the performance of the proposed linear-cavity tunable fibre lasers is better than that of ring-cavity tunable laser counterparts. Specifically, we show that linear-cavity based tunable fibre lasers can achieve higher output power, a larger side mode rejection ratio (SMRR) and narrower laser linewidth than ring-cavity tunable fibre lasers.
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Elias, Mauro Biscaro. "Sistemas de sensores ópticos baseados em fibra óptica de perfil-W dopada com Érbio." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/264962.
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Orientadores: Carlos Kenichi Suzuki, João Batista Rosolem<br>Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica<br>Made available in DSpace on 2018-08-21T04:05:23Z (GMT). No. of bitstreams: 1
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Previous issue date: 2012<br>Resumo: Fibras ópticas de casca rebaixada (também conhecidas como fibras ópticas de dupla-casca ou fibras ópticas de perfil-"W") com cortes do modo fundamental proporcionam perdas distribuídas altas em comprimentos de onda longos e perdas baixas em comprimentos de onda curtos. A grandeza da brusca transição entre a perda baixa em comprimentos de onda curtos e a perda alta em comprimentos de onda longos excede 200 dB/km e é extremamente sensível à curvatura aplicada na fibra. O fenômeno é atribuído ao acoplamento modal entre o modo guiado no núcleo e os modos discretos guiados na casca externa. A fibra óptica ativa de casca rebaixada Er: Al/Ge/SiO2 (DC-EDF) pode ser projetada para ter um corte do modo fundamental próximo de 1530 nm o que proporciona supressão distribuída da emissão espontânea amplificada (ASE) na banda-C em proveito da ASE na banda-S. Este fenômeno, associado a um outro, o de perda induzida por curvatura, proporciona um modelo alternativo para obter amplificação óptica na banda-S, exigida para expandir a capacidade de sistemas de multiplexação por divisão de comprimentos de onda (WDM). Um laser à fibra óptica, configurado na forma de anel, de fibra óptica de casca rebaixada dopada com érbio, que pode ser sintonizado através de perdas induzidas por curvatura na fibra óptica, ou pelo uso de um filtro óptico sintonizável, também pode ser projetado. Devido às características de amplificação e "lasing" desenvolvidas para aplicação na banda-S, baseadas em propriedades únicas, a fibra DC-EDF foi base dos sistemas de sensores desenvolvidos neste trabalho. De fato, os sistemas de sensores propostos mostraram alta sensibilidade, larga faixa dinâmica, e ampla largura de banda, e podem ser usados para monitorar parâmetros estáticos, tais como força, pressão, deslocamentos e parâmetros dinâmicos usados em acústica e vibrações. Dois tipos de sistemas de sensores, com diferentes modelos, foram estudados: um sensor-amplificador e um sensor-laser. Os desempenhos desses sistemas de sensores na banda-S (1490 e 1510 nm) foram estudados e analisados nas condições estática e dinâmica<br>Abstract: Depressed-cladding (often referred to as dual-clad or "W"- fiber) fibers with fundamental-mode cutoffs provide high distributed losses at long wavelengths and low losses at short wavelengths. The magnitude of the abrupt transition between low-loss at short wavelengths and high-loss at long wavelengths exceeds 200 dB/km and is found to be extremely sensitive to fiber curvature. The phenomenon is attributed to mode coupling between the core-guided mode and the discrete modes guided in the outer cladding. The active depressed-cladding Er: Al/Ge/SiO2 fiber (DC ? EDF) may be designed to have a fundamental mode cutoff near 1530 nm and provides distributed suppression of C-band amplified spontaneous emission (ASE) to the advantage of that in the S-band. This phenomenon, associated with the mechanism of induced bending loss, provides an alternative approach to obtain amplification in S-band, required to expand the capacity of wavelength-division multiplexing (WDM) systems. A S-band depressed-cladding erbium-doped fiber ring laser which can be tuned through the active fiber bending losses or by using an optical tunable filter, can be designed as well. Due to the amplification and lasing characteristics developed for S-band, based on unique properties, the DC - EDF was the basis of the optical sensing systems developed in this work. In fact, the sensing systems proposed showed high sensitivity, high dynamic range and wide bandwidth, and can be used to monitor static parameters, such as force, pressure, displacement and dynamic parameters used in acoustics and vibrations. Two types of sensing systems, with different approaches, have been studied: an amplifier-sensor and a laser-sensor. The performances of these sensing systems in S-band (1490 and 1510 nm) were studied and analyzed in static and dynamic conditions<br>Doutorado<br>Materiais e Processos de Fabricação<br>Doutor em Engenharia Mecânica
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Herbster, Adolfo Fernandes. "Projeto de amplificadores a fibra dopada com érbio para sistemas baseados em multiplexação modal." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/18/18155/tde-06082015-144812/.
Texte intégralRésumé :
Os sistemas ópticos atuais, baseados em fibras monomodo, operam próximos ao limite teórico da capacidade. Sistemas ópticos baseados em multiplexação modal (Mode Division Multiplexing – MDM) possibilitam o aumento da capacidade do sistema por meio do uso de fibras de poucos modos. Nestes sistemas, a propriedade de ortogonalidade entre os modos propagantes permite que cada modo espacial carregue um sinal óptico específico. O amplificador à fibra dopada com érbio (Erbium-Doped Fiber Amplifier – EDFA) segue fundamental para assegurar a transmissão em longas distâncias. No entanto, devido às distintas distribuições de intensidade dos modos que compõem o sinal de entrada, cada modo experimenta diferentes valores de ganho. Desta forma, o objetivo principal no projeto de EDFAs de poucos modos (Few-Mode Erbium-Doped Fiber Amplifier – FM-EDFA) é determinar os melhores parâmetros opto-geométricos da fibra para produzir uma amplificação eficiente. A metodologia normalmente empregada é baseada na resolução das equações de taxa e de propagação. Nesta tese, é proposta uma metodologia alternativa de projeto de FM-EDFA, baseada em uma nova figura de mérito. Este parâmetro quantifica o nível de inversão da população dos íons na fibra a partir da integral de superposição (overlap integral), considerando tanto o perfil de dopagem da fibra dopada com érbio para poucos modos (Few-Mode Erbium-Doped Fiber – FM-EDF) quanto as distribuições de intensidade dos sinais de entrada e de bombeio. A aplicação desta metodologia permite reduzir, em cerca de 25-40 vezes, o número de resoluções das equações de taxa e de propagação e, consequentemente, diminuir o tempo de processamento e reduzir o esforço computacional. Como consequência da maior velocidade de processamento, torna-se possível a aplicação de métodos de otimização mais rigorosos, permitindo uma busca em um espaço irrestrito de soluções. Especificamente, a partir de uma metodologia baseada em algoritmos genéticos, obteve-se um perfil de dopagem otimizado. É também demonstrado que os perfis com geometria circular exibem melhores características, como excelente desempenho do FM-EDFA e maior facilidade de fabricação. Por meio da análise da figura de mérito, é mostrado que o desempenho do FM-EDFA é afetado pelas características do modo de bombeio. Finalmente, o desempenho de um sistema óptico MDM é avaliado, simulado por meio da integração entre as ferramentas MatLab® e VPItransmissionMakerTM, comprovando a necessidade do projeto de um amplificador específico para sistemas MDM.<br>Modern optical systems based on single-mode fiber, operate close to the theoretical capacity limit. By using few-mode fibers, optical systems based on modal division multiplexing (MDM) allows increased system capacity. In these systems, orthogonality between the propagating modes allows each spatial mode to carry a specific optical signal. The erbium doped fiber amplifier (EDFA) remains essential to ensure long distance transmission. However, due to the distinct intensity profile distributions of the modes which comprise the input signal, each mode experiences a different value of optical gain. Thus, the main objective in the few-mode EDFA design (FM-EDFA) is to determine the best opto-geometrical fiber parameters in order to produce an efficient amplification. The methodology normally used is based on the simultaneous resolution of the rate and propagation equations. In this thesis, we propose an alternative methodology for the FM-EDFA design, based on a new figure of merit which quantifies the level of population inversion for the Er ions in the fiber, by means of a overlap integral considering both the doping profile of the few-mode erbium doped fiber (FM-EDF) as well as the intensity distributions of the optical signals and pump beams. This methodology reduces, by a factor of 25-40, the number of resolutions of the rate and propagation equations, thereby decreasing processing time and computational effort. As a consequence of the improved processing speed, it becomes possible to apply more rigorous optimization methods in an unrestricted solution space. Specifically, by using a genetic algorithm technique, we obtained an optimized doping profile. It is also shown that profiles with circular geometry exhibit improved features, such as excellent FM-EDFA performance and ease of manufacturing. By analyzing the figure of merit, it is shown that the FM-EDFA performance is affected by the characteristics of the pump mode. Finally, the performance of an MDM optical system is evaluated, by integrating Matlab and VPI simulation tools, to demonstrate the need for specific amplifier designs in MDM systems.
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Freire, Hermelo Maria. "Amplifier control using machine learning and coloured optical packet switching node design in optical networks." Electronic Thesis or Diss., Institut polytechnique de Paris, 2020. http://www.theses.fr/2020IPPAS024.
Texte intégralRésumé :
Le débit de données et la consommation d’énergie sont les principaux défis auxquels doivent faire face les réseaux optiques. Afin de réduire la consommation d’énergie, les réseaux opérateurs de transport optiques basés sur le concept de commutation de circuits optiques (OCS), deviennent optiquement transparents, réduisant les conversions optique/électrique (O/E) et électrique/optique (E/O). Pour faire face à l’augmentation du débit de données, on utilise des formats de modulations complexes et la technique de multiplexage en polarisation et on économise le spectre des fibres optiques en considérant une grille en longueurs d’onde plus flexible que la grille fixe ITU-T WDM. On développe des transpondeurs flexibles capables de sélectionner différents formats de modulation et longueurs d’onde; on développe également des multiplexeurs optiques d’insertion/extraction reconfigurables (ROADMs) basés sur des commutateurs sélectifs en longueur d’onde (WSSs). Ces réseaux flexibles prennent également en compte un trafic plus dynamique. Dynamisme et flexibilité impactent fortement les équipements des réseaux optiques, y compris les nœuds optiques d’un point de vue couche physique et couche de contrôle. Lorsque des canaux ou demandes sont ajoutés et/ou extraits, l’excursion de puissance optique des amplificateurs à fibre dopée à l’erbium (EDFAs) varie temporellement ce qui implique qu’elle doit être contrôlée dynamiquement. Dans ce contexte, le concept de réseau défini par le soft (SDN: Software Defined Network) prend tout son sens et l’introduction des techniques d’apprentissage machine (ML) permet d’entrevoir une aide au concept de SDN pour la gestion et le contrôle dynamique des réseaux optiques. Dans la première partie de ce travail de thèse, nous étudions l’excursion de puissance optique dans les réseaux de transport optiques dynamiques. Afin d’en atténuer les effets indésirables, nous introduisons et mettons en œuvre un module de prédiction et de pré-compensation de l’excursion de puissance en utilisant les méthodes ML. Comme les altérations de la couche physique (PLIs : Physical Layer Impairments) s’accumulent le long du chemin optique entre les noeuds source et destination de réseau, nous associons à l’excursion de puissance optique le rapport signal/bruit optique (OSNR: Optical Signal to Noise Ratio) et le taux d’erreur binaire (BER: Bit Error Rate), afin d’estimer la qualité de transmission (QoT: Quality of Transmission) de nouvelles configurations de canaux. Ensuite, en utilisant l’approche d’apprentissage par renforcement (RL), nous attribuons un format de modulation et une longueur d’onde aux différents canaux de façon automatique afin de réduire la probabilité de blocage des demandes entrantes dans les nœuds optiques. Dans la deuxième partie de ce travail de thèse, nous présentons notre contribution en tant que partenaire du projet ANR N-GREEN. Le principal objectif de N-GREEN est de proposer une nouvelle génération de routeurs peu consommateurs en énergie en considérant une architecture de réseau. Dans ce projet, nous abordons une architecture de réseau basée sur la commutation optique de paquets colorés (OPS: Optical Packet Switching) en rupture avec celle considérée dans la première partie de cette thèse. Dans le cadre de ce projet, nous avons caractérisé expérimentalement un commutateur optique 2 x 2 basé sur des amplificateurs optiques à semi-conducteurs (SOAs). Cette caractérisation nous a permis de valider un réseau en anneau constitué de 10 noeuds en cascade. En envisageant une configuration de commutateur 16 x 16, la caractérisation expérimentale, dans des configurations à canal unique et WDM, laisse entrevoir des possibilités intéressantes pour la transmission de données à très haut débit<br>Data rate and energy consumption are the major concerns in optical networks. In order to reduce energy consumption, transport operator networks based on optical circuit switching (OCS) concept, are becoming optically transparent, reducing optical to electrical (O/E) and electrical to optical (E/O) conversions. To face data rate increase, complex modulation formats and dual-polarization systems are considered and fiber spectrum is saved using network resources in a more efficient way, giving rise to a flexible frequency grid. Flexible transponders are developed to tune modulation formats and wavelengths and reconfigurable optical add/drop multiplexers (ROADMs) based on wavelength selective switches (WSSs) are studied. Flexible networks consider also a more dynamic traffic. Dynamism and flexibility lead to a deep transformation of the optical networks, including optical nodes, from both physical and control layer point of view. When channels are added and/or dropped, optical power excursion from erbium doped fiber amplifiers (EDFAs) has to be controlled dynamically. In that context, software defined networking (SDN) assisted by machine learning (ML) techniques is envisaged as promising candidate for the management and the dynamic control of optical networks. In this context, in the first part of our PhD work, we deal with optical power excursion in dynamic optical transport networks. In order to mitigate undesirable effects, we introduce and implement power excursion prediction and pre-compensation module using ML methods. As physical layer impairments (PLIs) accumulate along the path, we consider optical power excursion together with optical signal to noise ratio (OSNR) and bit error rate (BER), to estimate quality of transmission (QoT) of unseen channel configurations. Afterwards, using a reinforcement learning (RL) approach, we establish an autonomous impairment aware modulation format and wavelength assignment procedure, and we show that this permits to reduce the blocking probability of the incoming demands in optical nodes. In the second part of our PhD work, in the context of the N-GREEN project from the French national agency of research, we address a disruptive network architecture based on coloured optical packet switching (OPS). The main objective of N-GREEN is to propose a new generation of energy efficient routers. In the N-GREEN project, we perform the experimental characterization of an optical 2 x 2 switch based on semiconductor optical amplifiers (SOAs). This characterization leads to the proof of concept of a ring network with 10 nodes in cascade. Envisaging a 16 x 16 switch configuration, the experimental characterization, in single channel and WDM configurations, unveil interesting possibilities for the transmission of ultra-high data rates
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Osorio, Sergio Paulo Amaral. "Fabricação e caracterização de fibras microestruturadas de vidros teluritos dopados com érbio." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/278259.
Texte intégralRésumé :
Orientador: Luiz Carlos Barbosa<br>Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin<br>Made available in DSpace on 2018-08-08T19:58:45Z (GMT). No. of bitstreams: 1
Osorio_SergioPauloAmaral_D.pdf: 8946065 bytes, checksum: 9771cf8636d67bee8eb1b92d030d0d13 (MD5)
Previous issue date: 2007<br>Resumo: Neste trabalho três tipos de vidro telurito são estudados, fabricados e caracterizados, tendo em vista a fabricação de fibras ópticas de cristal fotônico. Basicamente, dois processos de fabricação de fibras de cristal fotônico foram considerados: 1) Empilhamento e puxamento, e 2) Extrusão.
Os vidros teluritos fabricados são: 0,77TeO2¿0,23WO3; 0,75TeO2¿0,20Li2O¿0,05TiO2 e 0,68TeO2¿0,155ZnO¿0,05Li2CO3¿0,015Bi2O3¿0,095CsCl (mol%), dos tipos binário, ternário e quinqüenário, respectivamente, os quais foram dopados com Er2O3. As caracterizações efetuadas foram: a) Medida do índice de refração, 2) Fotoluminescência, 3) Absorbância, 4) Tempo de vida dos íons de Érbio, 5) Análise Térmica Diferencial, 6) Análise termogravimétrica e, 7) Viscosidade.
Como dito anteriormente, pode-se fabricar fibras microestruturadas de telurito por extrusão, ou pelo método de empilhamento e puxamento.
A extrusora disponível no laboratório de materiais vítreos foi feita para extrudar materiais polímeros. Nossa tentativa de utilizá-la para vidros telurito não foi bem sucedida. Porém, pudemos tirar algum proveito desta experiência para futuros projetos.
Os tubos de vidro telurito utilizados no método de empilhamento e puxamento foram fabricados tanto por sucção vertical do vidro fundido, quanto por rotação horizontal dos tubos em chama. No primeiro método, o diâmetro interno dos tubos de revestimento diminuiu de baixo para cima, devido ao efeito da gravidade, fazendo com que o preenchimento dos mesmos com tubos capilares fosse inadequado, ou seja, a secção transversal da fibra apresentou espaços vazios não preenchidos pelos capilares. No segundo método, o diâmetro interno dos tubos de revestimento não apresentou variação significativa ao longo de seu comprimento, possibilitando, assim, um melhor preenchimento dos mesmos por tubos capilares. Embora as fibras fabricadas com tubos feitos por rotação horizontal em chama apresentem boa geometria de secção transversal, a contaminação do vidro pela chama acarreta um aumento nas perdas de potência óptica dos modos guiados. Este efeito foi eliminado pela utilização de centrifugação em um forno radiante.
Verificamos, também, que as fibras microestruturadas com somente um anel de capilares ao redor do núcleo apresentam grandes perdas por confinamento.<br>Abstract: In this work, three types of tellurite glasses are synthesized and characterized, aiming the manufacturing of photonic crystal fibers or microstructured fibers. Basically, two types of manufacturing processes are considered: 1) Stacking and draw, and 2) Extrusion.
The tellurite glasses are: 0,77TeO 2¿0,23WO3; 0,75TeO2¿0,20Li2O¿0,05TiO2 e 0,68TeO2¿ 0,155ZnO¿0,05Li2C3¿0,015Bi2O3¿0,095CsCl (mol%), composed by two, three and five types of oxides, respectively, and Erbium oxide. The glasses were characterized by: a) index of refraction, 2) photoluminescence, 3) absorbance, 4) Erbium ions lifetime, 5) Differential Thermal Analysis, 6) Thermo gravimetric Analysis, and 7) Viscosity.
The extrusion machine of the laboratory was devised for polymers. Nevertheless, we tried with telluride glass but without success.
The tellurite glass tubes used for the stack and draw process were manufactured by vertical suction of the melted glass as well as by horizontal rotation of the tubes in flame.
For the vertical suction method, the tellurite tube inner diameter shows a taper feature from the bottom to the top of the tube, due to the gravity effect, that makes the jacket tube unsuitable for capillary filling, that is, the fiber transversal section shows empty spaces that could not be filled with capillaries.
For the second method, the telluride jacket tube inner diameter do not shows a significant variation with length, so it was possible to better fill it with the capillaries. Although the fibers made with tubes manufactured by horizontal rotation in flame shows good transversal geometry, the contamination of the glass by the flame gases brought about great losses for optical guided modes. The burner was replaced by a radiant oven.
We verified, also, that micro structured fibers with only one ring of capillaries around the nucleus shows great confinement loss arising from the leaky nature of the modes<br>Doutorado<br>Física da Matéria Condensada<br>Doutor em Física
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Palma, Giuseppe. "Design of microlaser in medium infrarer wavelengnth range for biomedicine and environmental monitoring." Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1S017/document.
Texte intégralRésumé :
Les micro-résonateurs optiques comptent parmi les dispositifs les plus importants en photonique. Les résonateurs WGM sont assez particuliers. Il s'agit de composant présentant une symétrie circulaire comme c'est le cas des sphères, des anneaux, des disques et des tores. Les résonateurs WGM présentent un facteur de qualité exceptionnel et un volume modal très faible. Ces appareils peuvent être utilisés dans plusieurs domaines, notamment la télédétection, le filtrage optique et l'optique non linéaire. D'autres applications sont possibles en biologie, médecine, spectroscopie moléculaire, surveillance environnementale, astronomie et astrophysique grâce à l'exploitation du rayonnement moyen infrarouge. Les micro-résonateurs optiques comportent un grand nombre de transitions vibrationnelles qui agissent comme des «empreintes» pour de nombreuses molécules organiques permettant le développement d'applications spectroscopiques innovantes et de nouveaux capteurs. Il convient de noter que l'atmosphère de la terre est transparente au niveau des deux fenêtres de transmission atmosphérique. La première est comprise entre 3 et 5 μm et la seconde entre 8 et 13 μm, ce qui rend possible des applications telles que la détection d'explosifs à distance ainsi que le brouillage de communication confidentielles. La large fenêtre de transparence en verres de chalcogénures dans le domaine spectral infrarouge rend envisageable le développement de nombreuses applications. Les verres de chalcogénure sont caractérisés par une bonne résistance mécanique et une durabilité chimique suffisante dans l'eau et l'atmosphère. Par ailleurs, l'indice de réfraction élevé, le rendement quantique élevé, l'énergie de phonon faible et la solubilité importante des terres rares permettent des émissions dans le domaine spectral du moyen IR. Dans cette thèse, la conception de dispositifs innovants en chalcogénure pour des applications utilisant le moyen infrarouge est étudiée en utilisant un code d'ordinateur personnel formé de façon aléatoire. Les appareils reposent sur des trois types de micro-résonateurs : les microsphères, les micro-disques et les microbulles. Les résonateurs WGM sont efficacement excités à l'aide de fibres nervurées et de guides d'ondes optiques de forme conique. Le nouveau procédé de conception est développé en utilisant la méthode d'optimisation par essaims particulaires (PSO). Elle permet de maximiser le gain d'un amplificateur reposant sur une microsphère d'émission laser dopée à l'erbium à 4,5 μm. Une technique innovante permettant de caractériser les propriétés spectroscopiques de la terre rare intégrant la recherche électromagnétique en mode WGM grâce à l'algorithme PSO a été développée. Les valeurs récupérées sont entachées d’une erreur inférieure à celle prévue par les instruments de mesure ayant un coût élevé. Des applications intéressantes peuvent être obtenues en excitant le micro-résonateur avec une fibre conique présentant deux LPG identiques sur les côtés. En effet, les FLP peuvent sélectionner le couplage de modes de fibre avec le résonateur WGM. En utilisant différentes paires de FLP identiques, opérant dans différentes bandes de longueurs d'onde, il est possible de coupler de façon sélective différents résonateurs à l'aide de la même fibre optique. Un code informatique aléatoire a été développé et validé. Il a démontré la faisabilité d'un capteur de microbulles de glucose. Un microdisque en terre rare dopé est étudié pour obtenir une source de lumière compacte et économique dans l'infrarouge moyen. Un code informatique est développé afin de simuler un micro-disque de terre rare dopé et associé à deux guides d'ondes nervurés, un pour le signal et l'autre pour la pompe. Le modèle est validé à l'aide d'un micro-disque dopée à l'erbium émettant à 4,5 μm. Ce dispositif très prometteur pour des applications dans le moyen infrarouge est obtenu en utilisant un micro-disque de praséodyme dopé émettant à 4,7 μm<br>Optical micro-resonators represent one of the most important devices in photonics. A special kind is constituted by the WGM resonators, i.e. devices with circular symmetry such as spheres, rings, disks and toroids. They are characterized by very small dimensions, exceptionally quality factor and very low modal volume becoming a valuable alternative to the traditional optical micro-resonators, such as Fabry-Pérot cavities. These devices allow applications in several fields, such as sensing, optical filtering and nonlinear optics. In particular, different applications in biology and medicine, molecular spectroscopy, environmental monitoring, astronomy and astrophysics are feasible in Mid-Infrared wavelength range. For example, it includes a lot of strong vibrational transitions that act as “fingerprints” of many bio-molecules and organic species allowing the develop of innovative spectroscopic applications and novel sensors. In addition, the earth's atmosphere is transparent in two atmospheric transmission windows at 3–5 μm and 8–13 μm and then applications such as remote explosive detection, e.g. in airports and for border control, and covert communication systems are feasible. The wide transparency window of chalcogenide glasses in Mid-Infrared makes possible the development of several devices. Chalcogenide glasses are characterized by good mechanical strength and chemically durability in water and atmosphere. Furthermore, the high refractive index, high quantum efficiency, the low phonon energy and high rare-earth solubility enables the emissions at long wavelengths.In this thesis, the design of innovative chalcogenide devices for applications in Mid-Infrared is investigated using an ad-hoc home-made computer code. The devices are based on three kinds of micro-resonators: microspheres, micro-disks and microbubbles. The WGM resonators are efficiently excited by using tapered fiber and ridge waveguides. A novel design procedure is developed using the particle swarm optimization approach (PSO). It allows to maximize the gain of an amplifier based on an erbium-doped microsphere lasing at 2.7 μm.An innovative technique in order to characterize the spectroscopic properties of rare-earth is developed integrating the WGM electromagnetic investigation with PSO algorithm. The method is based on two subsequent steps: in the first one, the geometrical parameters are recovered, in the second one, the spectroscopic parameters. The recovered values are affected by an error less than that provided by high-cost measurement instruments. Furthermore, the procedure is very versatile and could be applied to develop innovative sensing systems.Interesting applications could be obtained exciting the micro-resonator by a tapered fiber with two identical LPGs on the sides. Indeed the LPGs can select the fiber modes coupling with the WGM resonator. Using different pairs of identical LPGs operating in different wavelength bands, it is possible to selective couple different micro-resonators by using the same optical fiber. An ad-hoc computer code is developed and validated and it demonstrated the feasibility of a microbubble glucose sensor.In order to obtain a compact and cost-saving light source in Mid-Infrared, rare-earth doped micro-disk are investigated. A computer code is developed in order to simulate a rare-earth doped micro-disk coupled to two ridge waveguide, one at signal wavelength and the other one at pump wavelength. The model is validated using an erbium-doped micro-disk emitting at 4.5 μm. A very promising device for application in Mid-Infrared is obtained using a praseodymium-doped micro-disk emitting at 4.7 μm
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Ferreira, João Carlos de Melo. "Fiber amplifiers in transparent and dynamic optical networks." Doctoral thesis, Universidade de Aveiro, 2015. http://hdl.handle.net/10773/14090.
Texte intégralRésumé :
Doutoramento em Engenharia Eletrotécnica<br>In this thesis a study of optical fiber amplifiers in the context of
transparent and dynamic optical networks is performed.
We propose and validate a simplified model to estimate the gain profile
and amplified spontaneous emission (ASE) noise of broadband counterpumped
Raman fiber amplifiers (RFAs). The proposed model requires
very low computational resources and it is suitable to be used in
network planning tools. Based on the proposed model, we also present
an algorithm to design flat gain counter-pumped RFAs for the extended
C-band with low computational requirements.
We experimentally verify that the pump-reflecting RFA presents a higher
transient response due to channels add/drop, when compared to the
conventional counter-pumped RFA. This makes this amplifier
configuration unsuitable for transparent and dynamic optical networks.
To mitigate the transient response due to channel add/drop, a pumpcontrolled
gain-locked system based on the monitorization of the
reflected pump power is proposed and validated numerically and
experimentally. Following this approach, an efficient low-cost RFA
suitable for dynamic optical networks is proposed.
The dependence of the dynamical response of erbium-doped fiber
amplifiers (EDFAs) on the pump wavelength, pump power, and
temperature due to spectral hole burning (SHB) and site dependent
pumping (SDP) is experimentally investigated. A dependence of the
dynamic response on the pump wavelength, for amplifiers pumped
around 1480 nm, is shown. In order to explain this dependence, the
impact of SDP on the performance of EDFAs pumped at wavelengths
around 1480 nm is investigated, both experimentally and numerically.
As a result, an improved model incorporating the SDP effect for twolevel
EDFAs is derived and experimentally validated.<br>Nesta tese é feito um estudo sobre amplificadores de fibra ótica no
contexto de redes óticas transparentes e dinâmicas.
Propomos e validamos um modelo simplificado para estimar o perfil do
ganho e do ruído de emissão espontânea amplificada (ASE), para
amplificadores de Raman (RFAs) contra propagantes. O modelo
proposto requer baixos recursos computacionais e é adequado para ser
usado em ferramentas de planeamento da rede. Com base no modelo
proposto, apresentamos também um algoritmo com requisitos
computacionais baixos para desenhar RFAs contra propagantes com
ganho constante para a banda C estendida.
Verificamos experimentalmente que um RFA contra propagante com
reflexo da potência da bomba devido à adição/remoção de canais
apresenta uma resposta transiente mais elevada, quando comparado
com um RFA contra propagante convencional. Isto torna esta
configuração inadequada para redes óticas transparentes e dinâmicas.
Para mitigar a resposta transitória devido à adição/remoção de canais,
um sistema de controlo do ganho baseado na monitorização da
potência da bomba refletida é proposto e validado numérica e
experimentalmente. Seguindo esta abordagem, um RFA contra
propagante eficiente e de baixo custo adequado para redes óticas
dinâmicas é proposto.
A dependência da resposta dinâmica dos amplificadores de fibra
dopada com érbio (EDFAs) em função do comprimento de onda da
bomba, da potência da bomba e da temperatura devido ao spectral hole
burning (SHB) e site dependent pumping (SDP) é investigada
experimentalmente. Nos resultados obtidos é mostrada a dependência
da resposta dinâmica em função do comprimento de onda da bomba,
para amplificadores bombeados em torno de 1480 nm. Para explicar
esta dependência, o impacto do SDP no desempenho de EDFAs
bombeados em comprimentos de onda em torno de 1480 nm é
investigado, tanto experimental como numericamente. Como resultado,
um modelo mais completo, incorporando o efeito SDP para EDFAs de
dois níveis é derivado e validado experimentalmente.
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Goutaland, François. "Processus multiphotoniques, défauts ponctuels et mécanismes de leur formation dans les fibres optiques : étude par spectroscopie laser." Saint-Etienne, 1998. http://www.theses.fr/1998STET4021.
Texte intégralRésumé :
Ce mémoire se compose de deux parties, la première consacrée à l'étude des processus multiphotoniques se produisant dans des fibres optiques fortement dopées avec des ions er3+ et yb3+, et la seconde à l'étude des défauts induits par différents traitements dans des fibres germanosilicates. En étudiant la spectroscopie d'émission des fibres fortement dopées, sous excitations visibles (488 nm) et infrarouge (790 - 880 nm), nous mettons en évidence les différents mécanismes aux émissions bleues, vertes et rouge observées. Deux principaux types de processus d'up - conversion peuvent alors être distingués : ceux faisant appel aux transferts d'énergie Yb er et ceux faisant intervenir le phénomène d'absorption dans l'état excité (ESA). L'influence de la longueur de fibre et des concentrations en ions de terre rare sur les efficacités respectives de chacun de ces deux mécanismes est ensuite abordée. Après une présentation bibliographique des différents défauts dans la silice et les fibres germanosilicates, nous présentons le phénomène appelé dépendance modale du spectre d'émission d'une fibre optique, c'est-à-dire la variation du spectre d'émission d'une fibre en fonction du mode excité. L'évolution avec la température d'une bande d'émission centrée autour de 600 nm nous permet ensuite d'attribuer cette émission à des radicaux péroxys. Nous montrons alors que ces radicaux péroxys peuvent être photoinduits dans le CUR des fibres par irradiation intense à 488 nm. Enfin, nous étudions par spectroscopie Raman et spectroscopie d'émission les défauts générés dans deux types de fibres germanosilicates irradiées à 240 nm. Une technique de filtrage spatial du mode excité permet alors de séparer les défauts photoinduits dans le CUR de ces fibres de ceux localisés près de l'interface CUR/gaine
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KARAMSHUK, SVITLANA. "Organic sensitizers for application in photonic and photovoltaic devices." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2015. http://hdl.handle.net/10281/76622.
Texte intégralRésumé :
With the increasing demand for reliable and efficient devices with minimal environmental impact, novel organic materials gain extreme interest in the research community and industry. In this work we present synthetic strategies towards new organic compounds as promising materials for dye sensitized solar cells (DSCs) and low-cost integrated optics along with the investigation of these materials in devices.
Despite the recent hype in the research community around DSCs, increasing efficiency of DSCs is still a challenge. In principle, one promising way to obtain DSCs with significantly enhanced efficiency lies in connecting an n-type photoelectrode (i.e. n-Dye/TiO2) with a p-type one (i.e. p-Dye/NiO) leading to a tandem cell composed by two serially connected photoactive electrodes, each contributing with its own photovoltage to the total photovoltage delivered by the cell. Applying such concept could theoretically lead to organic photovoltaic devices with up to 40% overall conversion yield. One of the main limitations in p-type systems, commonly based on NiO, arises from fast charge recombination between the photoinjected hole in NiO, and the reduced dye. Therefore it is crucially important to develop p-type chromophores which could produce a long-lived charge separated state and minimize back recombination.
We were thus triggered to explore new organic structures for potentially efficient chromophores for p-type devices, by considering that the intramolecular charge transfer, at the basis of efficient charge separation in donor-acceptor dyes, is strongly dependent on the electron-withdrawing ability of the acceptor. Herein we present charge separators based on organic push-pull systems of tryphenylamine donors and branched electron acceptors (SK2-3-4) based either on Dalton (SK2) or benzothidaziole acceptor groups (SK3-4) which were synthesized and characterized by steady state spectroscopic, electrochemical and computational means. All the dyes exhibit strong charge transfer bands in the visible regions with ground and excited state energetics which are favourable to the sensitization of NiO electrodes. The computational investigation revealed a clear directionality of the lowest excited state exhibiting a marked charge transfer character, shifting the electron density to the acceptor branches, an electronic situation which is favourable to the hole injection in p-type semiconductors. When tested in p-type DSCs the SK series was found capable to sensitize NiO electrodes. The charge recombination kinetics, probed by considering the charge transfer resistance at the NiO/electrolyte interface at a comparable chemical capacitance, showed that the dyes behaved similarly and that the higher Voc observed with the SK4 dye is ostensibly due to a positive shift of the valence band edge, consistent with the shift in the anodic current threshold observed in dark conditions.
The second part of this work is dedicated to synthesis and characterisation of metallo-organic materials for optoelectronic devices. Optical amplification plays crucial role in the transmission and manipulation of optical signals in modern telecomunications. Nowadays amplifiers, which rely on erbium ions in a glass matrix, suffer from difficulties in fabrication and the need of high pump power densities to produce gain. Here we show a newly synthesised series of organic fully halogenated optical amplifier materials.
We will compare the ability of materials with different halogen atoms in complexes with transition metals to provide population of triplets which together with the lack of CH or OH oscillators in the molecule, can be potentially used as an efficient chromophore to sensitise the erbium ions in a long-lifetime erbium complex. Finally by doping Er(FTPIP)3 with newly designed Zn and Co complexes, we aim to find differences in the lifetime emission from erbium at the important telecommunication wavelength of 1.5 μm.
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O, Cochlain Ciaran R. "Tunable erbium doped fibre lasers for lightwave communication systems." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283935.
Texte intégral
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Perry, Ian Richard. "Investigations into ytterbium, ytterbium-erbium and thulium-doped silica-based fibre lasers." Thesis, University of Southampton, 1991. https://eprints.soton.ac.uk/427927/.
Texte intégral
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Williams, Quinton Lemonte. "Fast temporal dynamics of the erbium-doped fiber ring laser." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/27975.
Texte intégral
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VanWiggeren, Gregory D. "Chaotic communication with erbium-doped fiber ring lasers." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/30299.
Texte intégral
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Fadel, Hicham Joseph. "Tunable erbium-doped fiber ring laser using an intra-cavity filter." Thesis, Texas A&M University, 2004. http://hdl.handle.net/1969.1/1050.
Texte intégralRésumé :
Linear tuning the frequency of an erbium-doped fiber ring laser using both a Fabry-Perot filter and an electro-optic tunable filter has been experimentally demonstrated. The rate of frequency change is determined by monitoring the fringes produced by laser light transmitted through a fiber Fabry-Perot interferometer. The fiber ring laser has been tuned over a 50 nm spectral range when using the Fabry-Perot filter and a tuning rate of 16480 nm/s has been achieved. The spectral width of the laser is 0.049 nm and the nearest sidelobe to the main peak is more than 30 dB below the central lobe. When the electro-optic tunable filter is used, a spectral range of 11 nm is reached. The spectral width is 2.33 nm and is in close agreement with the filter theoretical results. The sidelobe to main peak difference is around 13 dB.
30
GARTER, MICHAEL JAMES. "ELECTROLUMINESCENT DEVICES FABRICATED ON ERBIUM DOPED GaN." University of Cincinnati / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin990545888.
Texte intégral
31
Issa, Fatma Mabruk. "Doped optical fibres thermoluminescence dosimetry for brachytherapy." Thesis, University of Surrey, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.580336.
Texte intégralRésumé :
In the various brachytherapy techniques the intent is to deliver as high a tumour dose as possible, limited only by surrounding normal tissue tolerance. The main feature of the techniques is very steep dose gradients, representing a potential limiting factor in accurate dose distribution measurements around sources. Dose distributions at distances less than 1 cm are therefore normally generated using either validated Monte Carlo (MC) simulations or standard dose calculation formalisms, for example that of AAPM TG 43, while dose measurements can only be performed at larger distances, normally greater than 1 cm from the outer dimensions of the source encapsulation Ge-doped silica fibres are a viable thermoluminescent dosimetry (TLD) system, providing good spatial resolution of approximately 120 urn, sensitive response to ionizing radiations, large dynamic dose range, good reproducibility and reusability, dose rate independence, minimal fading, resistance to water and low cost. Dosimetric characterisation of commercial Ge-doped silica fibres have been obtained by subjecting them to kilovoltage therapeutic x-ray radiation beams, verifying their use for brachytherapy sources; dose response, reproducibility and fading at 90 kVp and 300 kVp have been investigated. Central-axis depth doses have been obtained at the two accelerating potentials using different field size applicators, measurements being made using the fibres in both water and a GAMMEX RMr 4571 solid water phantom. Comparison has been made with central-axis depth doses, measured using a 0.6 cm3 graphite-walled ionisation chamber data and British Journal of Radiology Supplement 25 tabulated values (both in water). Ge-doped optical fibre dosimeters show good dosimetric response for low photon energies. These desirable characteristics support the use of these TL fibres as dosimeters for brachytherapy applications. Ge-doped optical fibre TL dosimeters have been used to measure the dose distribution around two Low Dose Rate (LDR) 125r seeds; model 6711, the new thinner model 9011 and a High Dose Rate (HDR) 192rr (MicroSelectron V2) source at proximal distances down to 1 mm, measured in a Perspex medium. The anisotropy has also been measured in Perspex, for distances from 10 to 100 mm from a LDR 1251 seed model 6711 centre, in 10 mm increments and at angles 10° to 90° in 10° increments from the seed central axis. Measured doses have been compared with calculations and treatment planning system (TPS) predicted doses for the same locations. Monte Carlo simulations were obtained using the EGSnrc \ DOSRZnrc codes and TPS predicted doses were obtained using the system VariSeed V8.0.2. For 1251 seed model 6711, the measurements agree with simulations to within 2.3 % ± 0.3 % along the transverse and perpendicular axes and within 3.0 % ± 0.5 % for measurements investigating anisotropy in angular dose distribution. Measured and Veriseed™ brachytherapy treatment planning system (TPS) values agreed to within 2.7 % ± 0.5 %. For the new thinner 1251 model 9011, dose measurements were in good agreement with simulations to within 2.1 ± 0.2 %, while dose measurements and doses obtained through use of the Variseed TPS agreed well, to within 2.2 ± 0.5 %. The above work has therefore demonstrated the applicability of Ge-doped optical fibres for use in brachytherapy.
32
Ono, Shunsuke. "Optical properties and gain characteristics of erbium-doped fiber amplifier." Kyoto University, 2005. http://hdl.handle.net/2433/144986.
Texte intégralRésumé :
Kyoto University (京都大学)<br>0048<br>新制・課程博士<br>博士(人間・環境学)<br>甲第11688号<br>人博第294号<br>新制||人||73(附属図書館)<br>16||185(吉田南総合図書館)<br>23331<br>UT51-2005-D437<br>京都大学大学院人間･環境学研究科環境相関研究専攻<br>(主査)教授 村中 重利, 教授 林 哲介, 助教授 田部 勢津久<br>学位規則第4条第1項該当
33
Furusawa, Kentaro. "Development of rare-earth doped microstructured optical fibres." Thesis, University of Southampton, 2003. https://eprints.soton.ac.uk/15481/.
Texte intégralRésumé :
This thesis describes the development of novel optical fibres, microstructured optical fibres (MOFs), and demonstrates device applications based on these structures. A particular emphasis is made on incorporating rare-earth ions within these fibres in order to realise novel active devices. Together with the development of the fabrication technique, characterisation and applications of these radically different fibre types are presented. First, the fabrication techniques of MOFs, which heavily rely upon fibre drawing, are studied. A mathematical model developed for the capillary drawing process is experimentally examined. Good agreement is obtained whilst it is also found that the model provides useful physical insights for determining the fibre draw parameters even for MOFs with complex geometries. Details of the fabrication techniques developed to optimise fibre structures are also presented. Transmission properties of highly nonlinear MOFs are then studied experimentally. It is found that the transmission losses are strongly influenced by the core dimensions due to the high Rayleigh scattering coefficient that originates from the holey cladding. A simple model is used to explain the observations. In addition, a continuous effort towards reducing OH-induced losses of this fibres type is outlined. Rare-earth doped highly nonlinear MOFs are fabricated and characterised. Then, three device demonstrations are carried out for the first time. These include a mode-locked ytterbium doped MOF laser, a nonlinear amplifier based on an ytterbium doped MOF, and a continuous wave erbium doped MOF laser with a very low threshold and high efficiency. Using the ytterbium doped MOF, wide tunability of ultrashort pulses from 1µm to 1.58µm is demonstrated using the soliton self frequency shift effect. For the erbium doped MOF, a pump power threshold of 0.5mW and a slope efficiency of 57% are demonstrated. Novel cladding pumped fibres, air clad MOFs, which use a conventional inner cladding and a holey outer cladding, are developed aiming at improved performance of cladding pumped fibre lasers. Wide tunability over 110nm and pure three level operation at 980nm of ytterbium doped cladding pumped fibre lasers are demonstrated. Finally, the fabrication and characterisation of large mode area microstructured fibres (LMA-MOFs) are described, and a comparison with conventional counterparts is made in terms of bend losses and corresponding effective mode areas. The results show that a slight refractive index difference introduced in the core region of this fibre type strongly modifies its waveguide characteristics. By applying this knowledge, a novel ytterbium doped cladding pumped fibre, which uses different sizes of air holes to define the inner and outer cladding, is developed. A continuous wave output power in excess of 1W is obtained. Results concerning various forms of pulsed laser operation using this fibre are presented and future possibilities are discussed.
34
Moulding, Keith M. "Transmission electron microscopy of nonlinear optical glasses and optical fibres." Thesis, University of Essex, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279411.
Texte intégral
35
BANERJEE, SIDDHARTHA. "OPTICAL PROPERTIES AND POPULATION STATISTICS OF ERBIUM IN OPTICALLY-PUMPED ERBIUM-DOPED ZINC SILICATE GERMANATE WAVEGUIDE AMPLIFIERS." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1100892919.
Texte intégral
36
Norhashim, Nurhakimah. "Temperature dependent photoluminescence of erbium doped YAG, zinc nitride and manganese-doped cadmium selenide optical materials." Thesis, University of Surrey, 2017. http://epubs.surrey.ac.uk/814013/.
Texte intégralRésumé :
Temperature dependent studies of a selection of materials including erbium-doped yttrium aluminum garnet (Er:YAG), zinc nitride nanocrystals(NCs) and manganese-doped cadmium selenide (CdMnSe) NCS have been undertaken in order to determine their fundamental optical properties. The study is based upon the measurement of their photoluminescence (PL) and PL transient decay transient over the temperature range of 300K to 5K. For the Er:YAG samples, two different sample types are studied as a function of erbium concentration that are a fast-cooled (mono-phase) and a slow-cooled (bi-phasic) polycrystalline material. Due to the presence of emission upconversion in these materials the emission dependence on excitation power is also studied. It is found that for high Er concentrations (40-50%) energy transfer upconversion (ETU) occurs that may be of use for assisting population inversion at the 4I11/2 level for the laser 3µm emission. Generally it is confirmed that the single phase and bi-phasic materials possess slightly different optical properties and that the material production must therefore be carefully controlled in order to realize optimized materials for optical applications. Zinc nitride NC materials are studied for the first time with four samples representing a range of NC diameters characterized. These materials were highly susceptible to oxidation which presented a significant challenge in their handling and study. Strong emission was observed across the visible spectral region though the origin of this it was found probably included trap state emission and for the smallest NC samples organic ligand emission. The PL was found to shifting to higher energies as the size of the NC is decreased as expected due to increased quantum confinement and in line with the Brus equation. Two of the samples (8.9nm and 2.7nm diameter NCs) display a temperature dependence of the optical properties in line that seen in other semiconductor NCs such as PbS. The other samples displayed anomalous behavior that could be due to ligand emission (2.5nm NC sample) or higher energy trap states caused by localized oxidation (3.8nm NCs). A study of temperature dependent optical properties of CdMnSe NCs was focused around the role of NC shape and type. Core only, core/shell and dot-in-rod samples were studied and all found to display a blue shift as temperature is reduced from 300K to ~5K of between ~24meV to 58meV. The core only NCs display a different luminescent behavior to that of the core-shell and dot-in-a-rod samples. The PL is related to the recombination of confined excitons within the NC, together with a contribution from what are most probably trap states located at the surface of the NC. In these samples no contribution from the Mn2+ ion is found suggesting that the dopant ions are not fully incorporated into the NC but may reside on the surface.
37
Olsen, David W. "Investigation of material and optical properties of erbium-doped sputtered glass films." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq28972.pdf.
Texte intégral
38
Lee, Boon Kwee. "OPTICAL STORAGE IN ERBIUM DOPED GALLIUM NITRIDE USING FOCUSED ION BEAM NANOFABRICATION." University of Cincinnati / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin985883067.
Texte intégral
39
Banerjee, Siddhartha. "Optical properties and population statistics of erbium in optically pumped erbium doped zinc silicate germanate (ZSG) waveguide amplifiers." Cincinnati, Ohio : University of Cincinnati, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=ucin1100892919.
Texte intégral
40
Starr, Elizabeth Mary. "Gemania doped silica : a new material for integrated optics." Thesis, University College London (University of London), 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339043.
Texte intégral
41
Townsend, Janet E. "The development of optical fibres doped with rare-earth ions." Thesis, University of Southampton, 1990. https://eprints.soton.ac.uk/400704/.
Texte intégralRésumé :
Research into rare-earth ion doping of silica based optical fibres is described and a detailed study of the fabrication process reported. Dilute solutions of rare-earth ions are employed to incorporate dopants into preforms prepared by conventional methods. Alternative core glass compositions are also studied. Parameters affecting dopant incorporation, host composition and refractive index, as well as impurity concentration are investigated. Spectroscopic fluorescence and absorption measurements are presented and provide important information for device applications. In addition, fluorescence lifetime data allow the effect of dopant concentration and host composition to be analysed. Thus, a model describing the limits of doping levels is developed. The use of rare-earth ion doped fibre in several devices, both active and passive, is assessed, with special reference to the fabrication process. In particular, the effect of host glass on the laser characteristics of Tm3+ doped fibres and of the ratio of doping levels on the behaviour of Er3+/Yb3+ codoped fibre lasers is discussed. A practical temperature sensor based on fibre doped with low levels of rare-earth ions and a fibre filter requiring heavily doped fibre are demonstrated, with suggested design for improved performance. Finally, a novel radiation dosimeter, based on Nd3+ doped fibre, is described. Unusually, the response is found to be both rereadable and linear, even at elevated temperatures, and a model is proposed to describe the behaviour of this material. In summary, the fabrication, characterisation and applications of a wide range of rare-earth ion doped optical fibres have been investigated in detail.
42
Rosa, Henrique Guimarães. "Estudo das propriedades ópticas do grafeno e sua aplicação como absorvedor saturável em lasers à fibra dopada com érbio." Universidade Presbiteriana Mackenzie, 2015. http://tede.mackenzie.br/jspui/handle/tede/1526.
Texte intégralRésumé :
Made available in DSpace on 2016-03-15T19:38:52Z (GMT). No. of bitstreams: 1
Henrique Guimaraes Rosa.pdf: 6486656 bytes, checksum: 6fc9fe7875ed2cceb89c9f5179b9f028 (MD5)
Previous issue date: 2015-02-25<br>Fundo Mackenzie de Pesquisa<br>In this thesis, we present results on the fabrication, transfer and characterization of
chemical vapor deposition (CVD) graphene and exfoliated graphene over glass and optical
fiber substrates, to study optical properties of graphene and its application as a saturable
absorber for Erbium-doped fiber laser (EDFL). Monolayer CVD graphene and stacked CVD
graphene samples were fabricated and characterized, transferred to the transverse face of
optical fibers, and a study on the relation between the optical properties of graphene samples
and the properties of ultrashort laser pulses generated in (EDFL) was performed. Furthermore,
we have developed a technique for transferring exfoliated nanomaterials which allowed us to
transfer exfoliated graphene onto optical fiber s faces and align the graphene flake to the fiber
core. With this transfer technique it is possible to fabricate samples with controlled number of
graphene layers onto optical fiber faces. As application, we demonstrate ultrashort pulse
generation in Erbium-doped fiber laser with exfoliated monolayer graphene samples as
saturable absorber. This is the first time that ultrashort laser pulses are generated with a single
exfoliated monolayer graphene sample.<br>Nesta tese, apresentamos resultados sobre a fabricação, transferência e caracterização
de grafeno CVD (grafeno fabricado por deposição química de vapor chemical vapour
deposition) e de grafeno esfoliado em substratos de vidro e em fibras ópticas, para o estudo
das propriedades ópticas do grafeno e sua aplicação como absorvedor saturável em laser à
fibra dopada com Érbio (EDFL). Foram fabricadas e caracterizadas amostras de grafeno CVD
monocamada e de grafeno CVD empilhado, transferidas para a face transversal de fibras
ópticas, e com estas amostras foram feitos estudos sobre a relação entre as propriedades
ópticas do grafeno e as propriedades de pulsos ultracurtos gerados em EDFL. Além disto,
desenvolvemos uma técnica para a transferência de nanomateriais esfoliados que permitiu a
transferência de grafeno esfoliado para fibras ópticas e seu alinhamento com o núcleo da
fibra. Com esta técnica de transferência é possível fabricar amostras com controlado número
de camadas de grafeno em fibra óptica. Como aplicação, demonstramos a geração de pulsos
em EDFL com uma amostra de grafeno esfoliado monocamada como absorvedor saturável.
Esta é a primeira vez que pulsos ultracurtos são gerados em lasers à fibra com amostra de
grafeno esfoliado de uma única camada sobre a face transversal da fibra óptica.
43
THOMAS, DJEISSON HOFFMANN. "PERFORMANCE OPTIMIZATION OF THE ERBIUM-DOPED FIBER AMPLIFIERS FOR OPERATION IN OPTICAL WDM NETWORKS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2007. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=11068@1.
Texte intégralRésumé :
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO<br>Nas redes ópticas que contém EDFAs (amplificadores à fibra
dopada com
Érbio), a característica variável do tráfego faz com que a
potência de entrada do
amplificador oscile, causando rápidas flutuações de ganho
que podem inviabilizar
a transmissão de dados nos canais WDM (multiplexados por
divisão de
comprimento de onda) co-propagantes. As variações de
tráfego podem ser lentas,
quando originadas pela adição ou remoção de canais WDM em
qualquer nó da
rede (roteamento dos canais WDM), ou rápidas, quando
causadas pela
transmissão aleatória de pacotes ou rajadas de dados
através da rede. Logo, para
alcançar uma alta qualidade de transmissão é necessário
garantir a operação
estável do EDFA, independentemente da natureza das
variações de sua potência
de entrada. Por isto, nós otimizamos o desempenho da
técnica da oscilação laser
em anel para controlar o ganho do EDFA, empregando dois
comprimentos de
onda espectralmente opostos, um acima e outro abaixo da
banca C. A partir da
ótima estabilidade de ganho alcançada com o emprego desta
técnica de controle
em uma unidade amplificadora, implementamos um sistema de
armazenamento de
sinais ópticos com ótimo desempenho e mostramos como
minimizar as flutuações
de ganho acumuladas após muitos EDFAs em cascata, tornando
os enlaces ópticos
de longo alcance mais eficientes.<br>In optical networks containing EDFAs (Erbium-Doped Fiber
Amplifiers),
the variable traffic characteristic lead the input power
to the amplifier to oscillate
and cause fast time-dependent gain fluctuations that can
impair the transmission
of data on co-propagating WDM (Wavelength Division
Multiplexing) channels.
Traffic variatons can be slow, when originated by add or
drop of WDM channels
at any network node (WDM routing), or fast, when come from
random
transmission of packet/burst data through the network.
Consequently, to reach a
high quality transmission it is necessary to ensure a
stable EDFA operation,
regardless the nature of its input power variations.
Therefore, we optimized the
performance of the ring-laser technique to clamp the EDFA
gain, using two
spectrally oposite lasing wavelengths, one above and
another below the C-band.
Based on the excellent gain stability reached with the
employment of this gain
control technique over one amplifier unit, we assembled a
high-performance alloptic
buffer memory and showed how to miminize the accumulated
gain
fluctuations after many cascaded EDFAs, enabling more
efficient long distance
optical links.
44
Mookherjea, Shayan 1977. "Optical distribution networks : signal-to-noise ratio optimization and distributed erbium-doped fiber amplifiers." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/9087.
Texte intégralRésumé :
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2000.<br>Includes bibliographical references (leaves [149]-151) and index.<br>Two important issues related to the use of remotely-pumped erbium-doped fiber amplifiers in optical distribution networks are analyzed. We investigate the optimal allocation of gain and loss among the stages of a lumped amplifier chain, using the concepts of a Nash solution and Pareto optimality. The propagation of optical channels along an erbium-doped fiber is derived from basic physical considerations, and compared with the well-known Desurvire model. We demonstrate a simple method of constructing bus distribution networks, but this approach is particularly sensitive to the numerical values of the parameters. A second approach is then discussed, extending the analysis of Sun et al. from ab-initio principles to model the effect of detectors (users) along a distribution network. Theoretical closed-form results indicate that the number of optical receivers that can be supported using this scheme is at least two orders of magnitude higher than without optical amplification. Finally, we analyze the effect of dynamic perturbations in the power that is extracted at the receivers. Though our focus is on bus networks, we also discuss tree distribution networks as extensions of the basic models. Our results have implications on the architecture of optical distribution networks.<br>by Shayan Mookherjea.<br>S.M.
45
Thomas, Jérémie. "Impact de la nanostructuration des fibres dopées Erbium sur leurs performances : application aux contraintes du spatial." Thesis, Montpellier 2, 2013. http://www.theses.fr/2013MON20178/document.
Texte intégralRésumé :
Ce travail de thèse porte sur l'étude de l'impact de la nanostructuration de la matière sur le comportement des fibres dopées Erbium en environnement radiatif tel que l'Espace. Cette étude est motivée par le fait qu'il n'existe pas de fibre dopée Erbium qualifiée pour le spatial, rendant l'AOFD indisponible pour ces applications, réduisant fortement l'intérêt de l'ensemble de la technologie WDM pour les satellites. Ainsi nous avons testé plusieurs fibres basées sur des technologies différentes dans le but d'évaluer leurs comportements sous radiations gamma. Nous avons ainsi défini un critère objectif pour la sélection des fibres dopées Erbium, et avons montré des éléments permettant de durcir des fibres co-dopées Aluminium en se basant uniquement sur des paramètres de conception. Ainsi, nous avons démontré une fibre durcie aux radiations à base de nanoparticules de silice dopées Erbium, montrant une perte de puissance de l'ordre de 1 dB en fin de mission typique d'un satellite. L'accent a également été mis sur la modélisation de l'AOFD en proposant un modèle évolué prenant en compte des effets non linéaires liés à la complexité de la spectroscopie de l'ion Erbium. Ce modèle a été complété par une prise en compte de l'effet des irradiations et de la guérison optique en utilisant un modèle de proche de celui développé par R. Chen. Nous avons pu noter la grande importance de l'effet de la guérison optique sur les performances de l'AOFD en fin de vie<br>This thesis focuses on the impact of nanostructuration on the performance of Erbium Doped Fiber in severe environment like Space. This study is motivated by the fact that no on-the-shell Erbium Doped Fiber can satisfy the space requirement, disabling the availability of the AOFD and stongly limiting the interest of the WDM technology for satellites. Several fiber based on different technologies have been tested in order to check their behavior under gamma radiations. We have defined an objective criterion for the selection of erbium doped fibers, and showed elements for hardening aluminum co-doped fibers, based solely on design parameters. In this way, we brought to the fore a radiation hardened fiber, based on silica nanoparticles, exhibiting a power decrease of 1 dB after a typical space mission. We also focused on EDFA modeling by proposing an evolved model taking into account non-linear effects due to the complex spectroscopy of Erbium. This model is completed by including irradiation effects thanks to a model such as Chen's one. The photobleaching effect that has been found to be strong is also considered
46
Mohd, Noor Noramaliza. "The use of Ge-doped optical fibres in external beam radiotherapy dosimetry." Thesis, University of Surrey, 2012. http://epubs.surrey.ac.uk/845678/.
Texte intégralRésumé :
The need for better characteristics of a radiation dosimeter arises from the requirement to verify the advanced techniques now employed in radiotherapy such as Intensity Modulated Radiation Therapy (IMRT), Intensity Guided Radiation Therapy (IGRT) and Cyberknife. To-date, one of the most promising dosimeter is thermoluminescent (TL) Ge-doped silica dioxide (SiO2) optical fibre. It has been established that it provides excellent spatial resolution, flexibility, modest cost, a nonhygroscopic nature, and excellent radiation response characteristics. In this study, the TL yield of 9 μm Ge-doped optical fibres (Ge-9 μm) has been investigated, establishing their key dosimetric characteristics: for verification of dose distributions in IMRT prostate dosimetry; for measuring out-of-field photon. These results show that the fibres offer consistent linearity between TL yield and dose for doses from 0.05 Gy up to 10 Gy for photon and electron beam energies, with reproducibility of better than 5%. For all investigated megavoltage photon and electron beam energies, the fibres also offer angular-, dose rate-, and temperature-independence, while a small energy-dependent response was found, of between 6 to 11%. However, at kilovoltage potentials there is significant energy dependence. When held at room temperature results show fading of 11% 133 days post-irradiation. In addition, Ge-doped optical fibre was observed to verify doses to within 3% of the IMRT radiotherapy treatment planning system predicted doses and LiF TLDs (TLD-100 and TLD-700) for the 6 MV and 15 MV energy photon beams used. The fibres have demonstrated potential for use in measuring IMRT out-of-field photon dose when using 6 MV photons, however when conducting 15MV irradiations, the fibres’ response needs to be corrected to account for the activation neutron dose. Ge-doped fibres also represent a viable system for use in mailed audit radiotherapy programmes; in particular measuring beam output under reference conditions as demonstrated in a postal dosimetry audit at selected Malaysian radiotherapy centres. The audit methodology has been developed with an expanded uncertainty of 4.22 % at 95% confidence interval for the energy photon beams used.
47
Martial, Igor. "Systèmes laser pompés par diode à fibres cristallines : oscillateurs Er : yAG, amplificateurs Nd : yAG." Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00705198.
Texte intégralRésumé :
Au cours de cette thèse, nous nous intéressons à deux applications nécessitant des sources laser impulsionnelles : l'imagerie active et l'usinage laser. L'imagerie active nécessite des sources laser efficaces émettant dans la gamme de sécurité oculaire (entre 1,5 µm et 1,7 µm) à des cadence de l'ordre du kilohertz et produisant des énergies par impulsion de plusieurs millijoules. Les sources efficaces émettant dans la gamme de sécurité oculaire utilisent l'ion erbium. Cependant la structure électronique complexe de l'ion erbium entraîne de nombreux effets parasites qui limitent fortement l'énergie accessible lors d'un fonctionnement à haute cadence. Pour diminuer l'influence de ces effets parasites nous avons utilisé le concept de fibres cristallines dans le cadre d'une collaboration entre le Laboratoire Charles Fabry et l'entreprise Fibercryst. La géométrie des fibres cristallines, combinant les propriétés des cristaux massifs et les avantages des fibres en verre nous a permis de dépasser les limites des sources actuelles. L'usinage de matériaux requière des sources laser impulsionnelles émettant dans le proche infrarouge (1 µm) et alliant forte énergie, forte puissance crête et forte puissance moyenne. Pour réaliser de telles sources, il est nécessaire d'utiliser des milieux à gain permettant de limiter les phénomènes thermiques et les effets induit par la puissance crête (effets non-linéaires). Pour cela nous avons utilisé à nouveau le concept de fibre cristalline, dopée cette fois ci par l'ion néodyme. Ces fibres cristallines ont été utilisées comme amplificateur de puissance pour amplifier des micro-lasers fonctionnant à haute cadence (de 1 à 100 kHz) et produisant des impulsions courtes (< 1 ns).
48
Dajczgewand, Julian. "Optical memory in an erbium doped crystal : efficiency, bandwidth and noise studies for quantum memory applications." Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLS198/document.
Texte intégralRésumé :
Le traitement quantique de l’information comme moyen de surmonter les limites de l’électronique classique a connu un développement rapide dans les deux dernières décennies. Plusieurs composants pour générer, traiter et envoyer l’information quantique sont nécessaires. Dans ce contexte, les mémoires quantiques optiques apparaissent comme des composantes principales capables de communiquer l’information quantique sur de longues distances en surmontant les pertes des fibres optiques dans un schéma de répéteur quantique. Durant la dernière décennie, plusieurs protocoles de stockage pour stocker l’information quantique ont été proposés et testés. Dans cette thèse, je présente le protocole Revival of Silenced Echo (ROSE) et sa réalisation dans un cristal Er3+:Y2SiO5. Ce matériau est un bon candidat pour une mémoire quantique grâce à sa transition dans la bande C des télécommunications où les pertes dans les fibres optiques sont minimales. Dans ce travail, j’évalue les performances du ROSE avec des impulsions faibles classiques. Je mesure l’efficacité, la bande passante et le temps de stockage qui sont des figures de mérite typiques d’une mémoire quantique optique. Pour une bande passante fixe, je démontre expérimentalement une bonne efficacité. En outre, je mesure la dépendance de la bande passante du protocole. Pour cette dernière les interactions dipôle-dipôle entre les ions d’erbium apparaît comme un facteur limitant. Enfin, je réalise le protocole ROSE avec quelques photons par impulsion afin d’évaluer son potentiel comme mémoire quantique. Je démontre une bonne efficacité avec un rapport signal sur bruit modéré. Je termine ce travail par une série de mesures dans des matériaux nouveaux (co-dopé ou dopé avec de l’erbium), pour augmenter la bande-passante de traitement d’échantillons dopés Er compatible avec les longueurs d’onde des télécommunications<br>Quantum information processing has been developing rapidly in the last two decades as a way to overcome the limitations of classical electronics. Several components to generate, process and send quantum information are needed. In this context, optical quantum memories appear as principal components to communicate quantum information at long distances by overcoming the losses of the optical fibers in the so-called quantum repeater scheme. During the last decade several storage protocols to store quantum information have been proposed and tested. In this thesis, I present the Revival of Silenced Echo (ROSE) protocol implemented in an Er3+:Y2SiO5 crystal. This material is a good candidate for a quantum memory because of its transition in the C-band of the telecom wavelengths where the losses in optical fibers are minimized. In this work, I evaluate the ROSE performances with weak classical pulses. I measure efficiency, bandwidth and storage time which are the typical figures of merit for an optical quantum memory. Starting with a fixed bandwidth, I demonstrate experimentally a good efficiency. Additionally, I measure the bandwidth dependence of the protocol. For this latter, the dipole-dipole interactions between erbium ions appears as limiting factors. Finally, I implement the ROSE protocol with a few photons per pulse to show its potential as a quantum memory. I report good efficiencies with a moderate signal to noise ratio.I finish this work with a series of measurements in new materials (doped or codoped with erbium), to extend the processing bandwidth of Er doped samples compatible the telecom wavelength range
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Huang, Xuezhen. "Fabrication and optical properties of (I) erbium-doped nanowires containing germanium and/or zinc oxide and (II) porous germanium nanowires." [Fort Worth, Tex.] : Texas Christian University, 2010. http://etd.tcu.edu/etdfiles/available/etd-04282010-134727/unrestricted/Huang.pdf.
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PENNA, STEFANO. "Design processing and characterization of organic devices for optical communications." Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2009. http://hdl.handle.net/2108/991.
Texte intégralRésumé :
La recente esplosione dei servizi a larga banda e i limiti imposti dalla legge di Moore hanno spinto la ricerca verso il concetto di chip ottico integrato, inteso come un dispositivo che implementa le principali funzioni ottiche, tipicamente nella banda C, su di un'unica piattaforma.
In questi dispositivi l'integrazione e la compattezza giocano un ruolo fondamentale. Tra i diversi materiali disponibili, i composti semiconduttori organici sono particolarmente attraenti perchè a basso costo di fabbricazione e particolarmente predisposti all'integrazione per via della loro struttura amorfa.
Tra le diverse funzioni da implementare in un chip ottico integrato, l'amplificazione e la generazione di luce sono ancora limitate. Questo è dovuto principalmente al fatto che l'erbio, necessario per l'emissione in banda C, ha proprietà sfavorevoli come basse sezioni d'urto di assorbimento ed emissione. Per questo motivo vengono utilizzati dei materiali host in grado di ospitare l'erbio al loro interno e di fungere da antenne, captando l'energia di eccitazione con maggiore efficienza e di trasferirla all'atomo di erbio. Un tipico esempio di questo tipo di sistema è dato dall'EDFA, in cui la matrice vetrosa delle fibra funge da host per l'erbio. Tecnologie come gli EDFA non sono però predisposte all'integrazione ottica, dal momento che fibre di circa 40 m di lunghezza sono richieste per ottenere una sufficiente amplificazione. In questo contesto i composti organici drogati con erbio, detti organolantanidi, sono promettenti per un'applicazione all'ottica integrata dal momento che possiedono proprietà interessanti come buone sezioni d'urto di assorbimento ed emissione e basso costo di lavorazione. Lo scopo di questo lavoro è di fornire una dimostrazione pratica delle potenzialità di applicazione dei composti organolantanidi per la realizzazione di un amplificatore DFB integrato in banda C a pompaggio elettrico
I diversi aspetti del dispositivo sono stati studiati separatamente, utilizzando l'uso di tecniche a basso costo come il solution processing e il pompaggio ottico tramite LED per l'eccitazione dei composti attivi. La possibilità del pompaggio elettrico è stata esplorata con la realizzazione di un LED organico (OLED) realizzato tramite spin-coating. Le cavità DFB sono state fabbricate tramite litografia per nanoimprinting ed interferenza laser e depositate con organolantanidi in funzione di strato attivo, ottenendo una linea di emissione a 1530 nm. Infine, le proprietà guidanti del dispositivo sono state studiate mediante la strutturazioen della cavità come guida d'onda di canale. La discontinuità d'indice planare è stata ottenuta tramite foto-patterning UV, ottimizzato per il composto organico attivo utilizzato in questo lavoro di tesi.<br>The recent explosion of broadband services and the limits imposed by the Moore’s law have stimulated strong research activities towards the integrated optical chips, that are composed of a platform on which many different optical functions, typically in the C-band, are implemented. Such devices are particularly challenging because integration and compactness play fundamental roles. Among the different materials used to process the optical integrated devices, three main classes can be identified: semiconductors, glasses and organic materials. The last ones are particularly attractive because of the low cost of processing and the high integration related to the amorphous structure, resulting in not required lattice matching conditions.
A common design approach in integrated optics is to optimize a particular optical function with a specific material, then to integrate it on the platform. Among the functions to be implemented, amplification and light generation are still limited with respect to the other functions such as modulation or coupling/splitting. This is due to the limits imposed by erbium for the C-band operation. Indeed, erbium is difficult to be optically excited because of the small absorption cross section, so host sensitizers such as glasses are needed to efficiently collect the outer excitation and transfer it to the erbium ions. The most famous example of erbium sensitizer scheme is provided by the Erbium Doped Fiber Amplifiers (EDFAs), wherein erbium ions are incorporated in glass matrices. However, EDFAs are not suitable for integrated chips since a long interaction length is required to achieve a sufficient gain level. Erbium-doped organic compounds are promising erbium sensitizers for the application to integrated chips as they exhibit attractive features such as high absorption and emission cross section, semiconducting behavior and low cost processing.
The aim of this work is to provide a demonstration of the potential of Er-doped compounds for the processing of an electrically driven integrated laser amplifier for the C-band of the optical communications. The different issues involved in such a challenging device have been studied separately, emphasizing the use of low cost techniques such as solution processing for organic deposition and LED pumping for the excitation of the active compounds. The opportunity for electrical pumping has been demonstrated with the processing of a spin-coated Er-doped organic LED. The optically pumped DFB cavities have been fabricated by nano-imprinting lithography and laser interference lithography and coated by Er-doped organic compound as active layer, resulting in a narrow emission line centered at 1530 nm. Finally, the waveguide issue has been addressed by designing a channel waveguide. Planar index discontinuity has been achieved by mean of a UV photo-patterning technique, purposed for the erbium-doped compound used in this work.