Laser beam control is important in many applications. Phase modulating spatial light modulators (SLMs) can be used to electronically alter the phase distribution of an optical wave-front and thus change the direction and shape of a laser beam. Physical constraints set limitations to the SLM and an ideal phase distribution can usually not be realised. In order to understand how such components can be used for non-mechanical beam control three nematic liquid crystal (NLC) SLMs have been thoroughly characterised and modelled. The pixel structure and phase quantisation give a discrepancy between ideal and realised phase distributions. The impact on beam steering capability was examined by measurements and simulations of the intensity distribution in the far-field. In two of the studied SLMs the pixel period was shorter than the thickness of the LC layer giving the optical phase shift. This results in a so-called “fringing field”, which was shown to degrade the phase modulation and couple light between polarisation modes. The deformation of the LC was simulated and a finite-difference time-domain (FDTD) algorithm was used to calculate how polarised light propagates through the optically anisotropic SLM. Non-mechanical beam steering and tracking in an optical free-space communication link were demonstrated. Continual optimisation of the steering angle was achieved by feedback from a video camera. The optical properties of the SLM in the time period right after a voltage update were studied. It was shown how light is redistributed between orders during the switching from one blazed grating to another. By appropriate choice of the blazed gratings the effects on the diffraction efficiency can be minimised. The detailed knowledge of the SLM structure and its response to electronic control makes it possible to predict and optimise the device performance in future systems.

The objective of this research work is to develop reliable and power-efficient synchronization algorithms for continuous phase modulation (CPM). CPM is a bandwidth and power efficient signaling scheme suitable for wireless and mobile communications. Binary CPM schemes have been widely used in many commercial and military systems. CPM with multilevel symbol inputs, i.e., M-ary CPM, can achieve a higher data rate than binary CPM. However, the use of M-ary CPM has been limited due to receiver complexity and synchronization problems. In the last decade, serially concatenated CPM (SCCPM) has drawn more attention since this turbo-like coded scheme can achieve near Shannon-limit performance by performing iterative demodulation/decoding. Note that SCCPM typically operates at a low signal-to-noise ratio, which makes reliable and power-efficient synchronization more challenging. In this thesis, we propose a novel timing and phase recovery technique for CPM. Compared to existing maximum-likelihood estimators, the proposed data-aided synchronizer can achieve a better acquisition performance when a preamble is short or channel model errors are present. We also propose a novel adaptive soft-input soft-output (A-SISO) module for iterative detection with parameter uncertainty. In contrast to the existing A-SISO algorithms using linear prediction, the parameter estimation in the proposed structure is performed in a more general least-squares sense. Based on this scheme, a family of fixed-interval A-SISO algorithms are utilized to implement blind iterative phase synchronization for SCCPM. Moreover, the convergence characteristics of iterative phase synchronization and detection are analyzed by means of density evolution. Particularly, an oscillatory convergence behavior is observed when cycle slips occur during phase tracking. In order to reduce performance degradation due to this convergence fluctuation, design issues, including delay depth of the proposed algorithms, iteration-stopping criteria and interleaver size, are also discussed. Finally, for completeness of the study on phase synchronization, we investigate the error probability performance of noncoherently detected full-response CPM, which does not require channel (or phase) estimation.

In this thesis, noncoherent differential demodulation of CPM signals with joint carrier frequency offset and symbol timing estimation is investigated. CPM is very attractive for wireless communications owing to major properties: good spectral efficiency and a constant envelope property. In order to demodulate the received CPM signal differentially, the symbol timing and the carrier frequency offset have to be estimated accurately. There are numerous methods developed for the purpose. However, we have not encountered studies (which are based on autocorrelation estimation and hence suitable for blind synchronization) that give expectable performance for both M-ary and partial response signaling. Thus, in this thesis we analyze a feedforward blind estimation scheme, which recovers the symbol timing and the frequency offset of M-ary CPM signals and partial response CPM signals. In addition, we surveyed low complexity symbol detection methods for CPM signals. Reduced state Viterbi differential detector incorporated to the joint frequency offset and symbol timing estimator is also examined. The performance of the examined demodulator scheme is assessed for the AWGN channel by computer simulations.

Parmi les techniques d'imagerie optiques utilisées en milieu clinique, la principale limitation est la faible résolution lorsque la profondeur d'examen dépasse quelques mm. Cette limite de résolution ne permet pas à l'heure actuelle de concurrencer les techniques d'imagerie médicales permettant de réaliser un examen du corps dans son intégralité (Rayons X, IRM, Scanner). Dans ce cadre, l'imagerie acousto-optique présente plusieurs avantages: elle permet de mesurer des propriétés optiques utiles pour la détection de tumeur, à la résolution spatiale des ultrasons. Cependant, les dispositifs de détection utilisés présentent un manque de sensibilité et de rapidité qui freinent le transfert de cette technique en milieu clinique.Ce constat nous a conduit à étudier les caractéristiques intrinsèques du signal acousto-optique afin de proposer deux architectures de pixels basées sur des technologies CMOS. La première architecture, totalement analogique, présente des caractéristiques de vitesse d'acquisition compatibles avec le temps de corrélation des milieux biologiques (<1 ms)et un pré-traitement du signal utile. La seconde architecture intègre une fonction de conversion analogique-numérique de manière à simplifier le montage optique, et traiter le signal plus efficacement.Par ailleurs, le contrôle de la phase en plusieurs points du front est essentiel pour refocaliser les signaux lumineux. Pour contourner les limitations de vitesse des dispositifs de contrôle adaptatif de phase de l'état de l'art, nous avons développé un dispositif monolithique constitué de l'empilement physique d'un modulateur de lumière en phase, à cristaux liquides, sur un circuit CMOS constitué d'une matrice de photo-détecteurs et de circuits de traitement afin de permettre le contrôle de front d'onde dès son acquisition. Le dispositif opto-électronique a été proposé et couplé à la première architecture électronique. Il permet de réaliser une opération sur la phase de l'onde lumineuse en chaque pixel (conjugaison de phase par ex.) en parallèle sur les pixels d'une matrice, dans un intervalle de temps inférieur au temps de corrélation des milieux biologiques. / Among the optical medical imaging techniques used in medicine, the main limitation is the low resolution at a penetration depth greater than a few mm. This limitation does not allows competing with the standard imaging techniques such as X rays or RMI based imaging. In that scope, the acousto-optical imaging features several advantages: it allows measuring an optical contrast useful to detect tumors, in conjunction with the spatial resolution of ultrasound. However, the state of the art detecting devices feature a lack of sensitivity, which prevent its transfer to medical practitioners.This leads us to study the intrinsic features of the acousto-optical signal in order to propose two CMOS pixel architectures. The first one, fully analog, is compliant with the correlation time of biological tissue (1 ms typ.) and features an analog processing of the relevant signal. The second one is based on a digital pixel which contains an analog to digital converter, allowing simplifying the optical setup and increasing the robustness of the processing.In addition, related to the recent progress in wavefront control, an opto-electronic device, coupled with the first pixel architecture, has been proposed. It allows performing an optical phase operation (e.g. phase conjugation) in parallel on a pixels array, within the correlation time of biological media. Thus, this monolithic device circumvents the speed limitations of state of the art setup by a physical stacking of a liquid crystals spatial light modulator over a CMOS image sensor.

Neste trabalho estudamos teórica e experimentalmente o efeito de Conjugação de Fase por Mistura Degenerada de Quatro Ondas (CFMD40) e Modulação Transversal de Fase em cristais dopados com Cr+3. Estudamos a CFMD40 em Al2O3:Cr+3 (rubi) e GdAlO3:Cr+3 com um laser de Ar (em &#955;=514nm) obtendo um bom acordo entre os resultados experimentais e os teóricos (nestes cálculos usamos os valores de n2 de um trabalho anterior [1]). O modelo teórico que fizemos explica muito bem o comportamento de saturação da eficiência da CFMD40 que não era compreendido em trabalhos anteriores [47,48.2]. Usando os mesmos valores de n2 obtivemos um bom acordo entre os resultados experimentais e teóricos para o efeito de Modulação Transversal de Fase. Também fizemos um modelo teórico para o efeito de Modulação Transversal de Fase em CFMD40 que explica nossas observações [2]. A não linearidade destes materiais foi investigada usando-se três técnicas experimentais diferentes [1.2] e por dois outros grupos [61.62] (para o rubi) através de mistura de duas ondas não degeneradas. Todas estas medidas estão em bom acordo. Na alexandrita (BeAl2O 4:Cr+3) estudamos o espectro de &#967;(3) (ou n2) em ressonância das linhas R. Nos atribuímos a forma assimétrica do espectro como sendo oriunda de duas contribuições para susceptibilidade, onde um termo é devido a interação ressonante com o sistema de dois níveis e o outro devido a mudança de polarizabilidade causada pela população do estado excitado (esta é a primeira vez que este efeito foi observado). / In this work we studied theoretical and experimentally the effects of Phase Conjugation by Degenerate Four Wave Mixing and Transversal Phase (PCD4WM) Modulation in Cr+3 doped crystals. We studied the PDC4WM in Al2O3:Cr+3 (ruby) and GdAlO3:Cr+3 with on Ar laser (at &#955;= 514 nm) and obtained a good agreement between our experimental and theoretical results (in these ca1culations we used the nonlinear refractive index n 2 values from a previous paper [1]. The theoretical model that we developed explains very well the saturation behaviour of the PDC4WM efficiency that was not understood in previous papers [47.48,2]. These values of n2 are also in good agreement with our results in Transverse Phase Modulation. We also developed a theoretical model for the effect of Transverse Phase Modulation in PCDFWM that explains our observations [2]. The nonlinearity ?n IND.2? from these materials was investigated by us using three different techniques [1.2], by other two groups [61.62] (for the ruby) in nondegenerate two-wave mixing and all those measurements are in good agreement. In alexandrite (BeAl2O4:Cr +3) we studied the &#967;(3) (or n2) spectrum in resonance with the R lines. We attributed the asymetric shape of the spectrum by the effect of two differents contributions, one term due to the resonant interaction of the two-level system and the other due to the polarizability change caused by excited state population (this is the first observation of this kind of effect.

Formatos de modulação com capacidade de ajuste às condições variáveis de propagação são de interesse para uso em redes ópticas reconfiguráveis. Alterações nos níveis de potência e no mapa de dispersão afetam o desempenho de sistemas de transmissão, limitando o alcance e a capacidade de reconfiguração da rede. Fornecer capacidade de ajuste dinâmico ao sinal transmitido, sem usar sistemas complexos de modulação ou de compensação variável de dispersão, é uma solução eficaz para se obter rendimento ótimo nas diversas condições de propagação na rede. Esta característica também é útil na instalação de redes convencionais, poupando tempo e reduzindo custos. Neste trabalho é proposto o formato de modulação NRZ com gorjeio sincronizado com o sinal como alternativa para sobrepujar as limitações impostas pelas redes reconfiguráveis. O sistema proposto tem o atrativo de permitir, além da capacidade de adaptação, a possibilidade de integração dos componentes ópticos do modulador num mesmo substrato. O desempenho do formato de modulação proposto foi analisado em diversas condições de propagação para sistemas a 10 Gbit/s, tanto em sistemas ponto-a-ponto como de longas distâncias. Esta análise foi feita por meio de modelagem matemática, simulações numéricas e experimentos em laboratório. Foi demonstrada a capacidade de ajuste a diversos mapas de dispersão e seus limites, bem como a compensação de efeitos da automodulação de fase causados por alterações no nível da potência do sinal. / Modulation formats with adjustment capability to the variable propagation conditions are of interest in reconfigurable optical networks. Changes in optical power levels and dispersion compensation map affect the transmission system performance, limiting the range and the network reconfiguration capability. To provide dynamical adjustment capability to the transmitted signal, using neither complex modulation systems nor variable dispersion compensation, is an effective solution to obtain optimal performance within the diverse network propagation conditions. This characteristic is also useful during conventional networks installation, saving time and reducing costs. In this work it is proposed the NRZ modulation format with signal synchronized chirp as an alternative to overcome the limitations imposed by the reconfigurable networks. The proposed system has the benefit of allowing, more than adaptation capability, the possibility of integration of the optical modulator\'s components in the same substrate. The proposed modulation format was analyzed under diverse propagation conditions for 10 Gbit/s, in point-to-point as well as long-haul systems. This analyses war performed by mathematical modeling, numerical simulations and laboratorial experiments. It was demonstrated the adjustment capability for diverse dispersion compensation maps and its limits as well as the compensation of the self-phase modulation effects due to changes in optical power levels.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-06-27T19:15:36Z No. of bitstreams: 1 eltonsoaresdelimafilho mestrado.pdf: 10470752 bytes, checksum: b2ec80f3017bdb5b70e7d1e60f734b92 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-08-07T21:06:43Z (GMT) No. of bitstreams: 1 eltonsoaresdelimafilho mestrado.pdf: 10470752 bytes, checksum: b2ec80f3017bdb5b70e7d1e60f734b92 (MD5) / Made available in DSpace on 2017-08-07T21:06:43Z (GMT). No. of bitstreams: 1 eltonsoaresdelimafilho mestrado.pdf: 10470752 bytes, checksum: b2ec80f3017bdb5b70e7d1e60f734b92 (MD5) Previous issue date: 2009-08-07 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Neste trabalho apresenta-se os princípios, a construção e o funcionamento de um aparato que realiza medidas interferométricas de atividade metabólica de microorganismos, em tempo real e de várias amostras simultaneamente. A construção do MAI1 compreende o desenvolvimento e implementação de técnicas de posicionamento das amostras, controle preciso de temperatura, bem como a aquisição e interpretação de padrões de sinais modulados de interferência óptica. Ao longo deste trabalho serão apresentados os modelos teóricos utilizados, os códigos de computador, os desenhos dos circuitos eletrônicos e da mecânica do aparato, bem como medidas realizadas com o mesmo. / This work presents the principles, construction and functioning of an apparatus wich measures the metabolic activity of microorganisms, in real time and from different samples simultaneously, using optical interferometry. The construction of MAI' required the development and implementation of techniques for positioning of samples, precision control of temperature, as well as the acquisition and interpretation of patterns of modulated optical interference signals. Along this work the theoretical models used, the computer codes, the electronic circuit drawings, and the mechanics of the apparatus, as well as measurements carried out with it, will be presented.

No description available.

Orientadores: Aldário Chrestani Bordonalli, Júlio César Rodrigues Fernandes de Oliveira / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-22T02:02:14Z (GMT). No. of bitstreams: 1 Ribeiro_VitorBedotti_M.pdf: 8224184 bytes, checksum: f63b4dc7f1e4170cdcb48f49bf1b4155 (MD5) Previous issue date: 2012 / Resumo: As mudanças nos padrões de tráfego na internet forçam a constante evolução das redes ópticas, que, por serem sistemas com grande capacidade e se estenderam por milhares de quilômetros, são a principal aposta para suprir a demanda por banda. A solução adotada foi aumentar a eficiência espectral da transmissão, por meio do uso de formatos de modulação de alta ordem, como o PSK e o QAM, da detecção coerente e da multiplexação em polarização. Nessa dissertação, os conceitos de uma transmissão coerente digital e os principais algoritmos para a recepção e recuperação de sinal são apresentados, considerando o formato de modulação DP-QPSK com taxa agregada de 112 Gb/s. É proposto, também, um método de adaptação de ganho para o algoritmo de módulo constante (CMA), que acelera a convergência e torna a rotina que rastreia as mudanças no estado de polarização do sinal óptico mais rápido e robusto. Os algoritmos para cada funcionalidade foram testados individualmente em simulação. O melhor conjunto de algoritmos é analisado e configurações experimentais em back-to-back com carregamento de ruído ASE, em anel de recirculação óptico de 225 km com 80 canais DWDM e, também, em transmissão pela Rede Experimental de Alta Velocidade GIGA no trecho Campinas - São Paulo - Campinas. Para a configuração em back-to-back, o limite do sistema foi de 10,5 dB de OSNR. No anel de recirculação, foi possível a transmissão de 80 canais a 112 Gb/s, totalizando 8,96 Tbit/s por 2925 km e ocupando 50 GHz de banda, ou por 2475 km e ocupando 25 GHz. Na rede GIGA, o sistema se mostrou estável, com taxa de erro de bits bem inferior ao limite por mais de 3 horas de análise. O método de adaptação de ganho proposto conseguiu acompanhar mais de 20 Mrad/s e 3 Mrad/s de variação angular no estado de polarização para 34 dB e 15 dB de OSNR, respectivamente, enquanto o CMA sem adaptação de ganho falha a 10 Mrad/s e 1,5 Mrad/s nas mesmas condições. Os resultados demonstram a eficácia e a estabilidade dos algoritmos e a capacidade de recuperação do sinal em simulação, em experimentos laboratoriais ou em campo / Abstract: The changes in traffic patterns due to the Internet force the constant evolution of optical networks. These systems, designed to deliver high transmission capacity over thousands of kilometers, are the key solution to meet the demand for bandwidth. The recent tendency to provide wider bandwidth without changing the infrastructure already deployed has been to increase the spectral efficiency of transmission by using high order modulation formats, such as PSK and QAM, and employment coherent detection along with polarization multiplexing. In this work the concepts of optical digital coherent systems and the main algorithms for signal reception and recovery are presented, considering QPSK modulation format and polarization multiplexing (DP-QPSK) at 112 Gb/s. It is also proposed a method for adaptive adjustment of the constant modulus algorithm (CMA) gain, which accelerates the convergence and makes the algorithm faster and more robust to changes in the state of polarization of the optical signal. The algorithms for each function were tested individually in a simulation setup. The best set of algorithms were then obtained and applied in the receiver end of different experimental setups: back-to-back with ASE noise loading; 225-km optical recirculation loop with 80 DWDM channels; and a field transmission over part of the high-capacity experimental network GIGA (Campinas - São Paulo - Campinas). For the back-to-back setup, the system limit was achieved at 10.5 dB of OSNR. For the recirculation loop, it was possible to transmit up to 80 channels at 112 Gb/s, or 8.96 Tbit/s for overall system capacity, over 2925 km, considering 50-GHz bandwidth signal, or 2475 km for 25-GHz bandwidth signal. For the GIGA network, the system was stable with bit error rate well below the FEC threshold during the 3-hour analysis. The gain adaptation method proposed was able to track over 20 Mrad/s and 3 Mrad/s of angular rotation rate in the state of polarization for OSNRs of 34 dB and 15 dB, respectively, while the CMA without gain adaptation fails to track frequencies above 10 Mrad/s and 1.5 Mrad/s in the same conditions. The results show that the set of algorithms is effective, stable and capable of recovering the signal during simulation, laboratory experiments or field trials / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica

The theses is focused on the use of PLC technology. The aim of the thesis is creating device which communicates in a narrowband transmission frequency band. Transmission of communication between plc elements runs through the low voltage distribution network. The frequency and phase modulations are used in order to change the character of data signal. Transmitter and receiver parameters are subjects to the CENELEC standard. The theses gives more attention to the area of hardware build communication element rather than the area of programming.