Orientador: Evandro Conforti / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-21T04:49:45Z (GMT). No. of bitstreams: 1 Rocha_Peterson_M.pdf: 5254230 bytes, checksum: 811832dc531fcd6bcc9edf29f71bf219 (MD5) Previous issue date: 2012 / Resumo: Modulações ópticas avançadas como DQPSK e QAM tem sido escolhidas por serem formatos multiniveis (dois bits ou mais por símbolo), aumentando a eficiência espectral de sistemas ópticos. Entretanto, o amplificador óptico a semicondutor (SOA) indicado principalmente para aplicações de media distancia (da ordem de 20 km), pode degradar o sinal DQPSK e QAM. Sistemas de fase modulada (como o DQPSK) são afetados principalmente por SPM e XPM, devido ao ruído de fase não-linear adicionado a fase óptica do sinal. Visando analisar estes problemas, apresenta-se um estudo sobre os sinais NRZ-DQPSK e 16-QAM amplificados pelo SOA, bem como outros fatores que degradam tais sistemas, através de simulações com os softwares comerciais OptiSystem e VPItransmissionMaker. Nas simulações, resultados foram obtidos estando em acordo com a teoria e em acordo com o capitulo 3. Para o sistema DQPSK, o SOA degradou o sinal em todos cenários propostos para avaliar o sistema. O sinal NRZ-DQPSK apresentou maior penalidade quando o ganho do SOA foi de 20 dB. Efeitos não-lineares juntamente com a dispersão cromática limitam fortemente a distancia do enlace, e ao compensar a dispersão cromática no enlace com maior penalidade em 56 Gbps, o sinal NRZ-DQPSK pode trafegar por uma distancia 10 vezes maior (de 5 km para 50 km) com uma BER de 10-12. Para o sistema QAM, o sinal foi penalizado pelo SOA em todos os casos, e utilizando o SOA com ganho grampeado, os efeitos não-lineares foram minimizados, melhorando substancialmente o desempenho. Compensando a dispersão cromática e usando o SOA com ganho grampeado para o caso com maior penalidade, o sinal 16-QAM viajou a uma distancia 16 vezes maior (3 km e 50 km) / Abstract: High spectral efficiency is being achieved in modern optical fiber systems using multilevel optical modulation formats such us DQPSK and QAM, with more than one bit per symbol. However, amplifying devices such as the semiconductor optical amplifier (SOA) can degrade the DQPSK signal. In recent years SOAs have gained much attention (mainly in medium distance links, around 20 km) due to non-linear and fast switching potential applications (wavelength conversion, 3R regeneration, optical packet switching, etc.). In addition, the SOA under gain saturation further enhance deleterious nonlinear effects such as SPM, XGM, FWM, XPM. Phase modulated systems as DQPSK are affected mainly by SPM and XPM due to the nonlinear phase noise added to the controlled phase of the optical modulated signal. This work presents a study on the NRZ-DQPSK and 16-QAM signals when amplified by SOAs, analyzing the main factors degrading such systems through simulations using commercial OptiSystem and VPItransmissionMaker software. SOA showed degradation effects over DQPSK, with larger penalties to NRZ signals and optical gain over 20 dB. Non-linear effects and chromatic dispersion impose a maximum distance limit. In dispersion compensated links, 10 fold distances are achieved in relation to standard fibers (5 to 50 km) with BER= 10-12. For 16 QAM, the penalties are still high. However, gain clamped SOAs have better performance with a 16 fold distance increase (3 km to 50 km) / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica

Wavelength Division Multiplexing Passive Optical Networks (WDM PONs) offer a great solution to satisfy the increasing demand of bandwidth. In addition, it offers a higher level of data security through virtual point to point connections. A great challenge in realizing cost-effective WDM PON is the need for a transmitter at each Optical Network Unit (ONU) with a dedicated wavelength, which overloads the total cost of the system, in addition to reducing the number of available wavelengths in the system. Remodulation scheme is an ultimate solution for these problems of WDM PONs as the downstream signal itself is remodulated with upstream data which saves the need for a laser source at the ONU side. In this thesis I propose and experimentally demonstrate a novel wavelength remodulation scheme for WDM PONs that employs Differential Phase Shift Keying (DPSK) for downstream and Return to Zero DPSK (RZ-DPSK) for upstream. The use of DPSK enhanced the system with improved receiver sensitivity and RZ-DPSK improved the tolerance toward chromatic dispersion. In addition, I investigate the Backreflection (BR) penalty resulting from beat noise of BRs with upstream signal in a bidirectional WDM PON system that uses remodulation and phase modulation as a modulation format. I experimentally demonstrate the optimal conditions to operate the system and minimize the BR penalty.

Thesis: Elec. E., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 1976 / Bibliography: leaves 255-263. / by Dennis V. Marsicano. / Elec. E. / Elec. E. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science

The goal of the theses is to propose an idea for a generator of a radar polyphase modulated signal, that will operate at a frequency of 30 MHz. At the beginning of this project, an outline of the basic structure of the generator is proposed and a function of a programable logical perimeter is analyzed. This perimeter, together with an oscillator, generate two mutually phase-shifted rectangular pulses in its outputs. The shift phase of these two pulses is set by a program, and operated by single-chip processor. Those pulses are consequently converted to sinusoidal wave with the help of filters, and the required phase is chosen by the multiplexer, which is also operated by the processor. The phase modulation is realized this way. The output signal of the generator is radiopulse, which subpulses are phase modulated by the described method. Individual parts are solved analogously in this Theses.

abstract: Modern Communication systems are progressively moving towards all-digital transmitters (ADTs) due to their high efficiency and potentially large frequency range. While significant work has been done on individual blocks within the ADT, there are few to no full systems designs at this point in time. The goal of this work is to provide a set of multiple novel block architectures which will allow for greater cohesion between the various ADT blocks. Furthermore, the design of these architectures are expected to focus on the practicalities of system design, such as regulatory compliance, which here to date has largely been neglected by the academic community. Amongst these techniques are a novel upconverted phase modulation, polyphase harmonic cancellation, and process voltage and temperature (PVT) invariant Delta Sigma phase interpolation. It will be shown in this work that the implementation of the aforementioned architectures allows ADTs to be designed with state of the art size, power, and accuracy levels, all while maintaining PVT insensitivity. Due to the significant performance enhancement over previously published works, this work presents the first feasible ADT architecture suitable for widespread commercial deployment. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2019

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Amplitude and phase modulated optical OFDM (Orthogonal Frequency Division Multiplexing) are analyzed in a 50GBit/s single channel and 40GBit/s 5 channel 512 subcarrier non-ideal dispersion-compensated fiber optic communication systems. PM-OFDM is investigated as an alternative to AM-OFDM to alleviate the problem associated with amplitude-modulated signals in a nonlinear medium. The inherent dispersion compensation capability in OFDM (using a cyclic prefix) allows transmission over a link whose dispersion map is not exactly known. OFDM also mitigates the effects of dispersion slope in wavelength-division multiplexed (WDM) systems. Moreover, the overall dispersion throughout the transmission link may vary due to environmental effects and aging. OFDM is inherently tolerant to over- or under-compensation and dispersion slope mismatch. OFDM transmission over dispersive, non-dispersion managed fiber links using OFDM requires an overhead in excess of the maximum accumulated dispersion. Existing WDM systems usually employ periodic dispersion management. OFDM in these systems requires a smaller overhead. It is, however, more susceptible to nonlinearity due to the coherent beating of subcarriers after each dispersion-compensated span. The large variation in intensity associated with amplitude-modulated OFDM makes this modulation format more susceptible to nonlinear effects in fiber compared to phase-modulated signals. This holds true unless dispersion and EDFA noise lead to amplitude variations strong enough for PM-OFDM to be degraded by nonlinear effects as well. In conclusion OFDM is beneficial for non-ideal dispersion managed systems. PM-OFDM can further improve the performance.

This thesis focuses on the generation and applications of stable optical frequency combs. Optical frequency combs are defined as equally spaced optical frequencies with a fixed phase relation among themselves. The conventional source of optical frequency combs is the optical spectrum of the modelocked lasers. In this work, we investigated alternative methods for optical comb generation, such as dual sine wave phase modulation, which is more practical and cost effective compared to modelocked lasers stabilized to a reference. Incorporating these comblines, we have generated tunable RF tones using the serrodyne technique. The tuning range was ±1 MHz, limited by the electronic waveform generator, and the RF carrier frequency is limited by the bandwidth of the photodetector. Similarly, using parabolic phase modulation together with time division multiplexing, RF chirp extension has been realized. Another application of the optical frequency combs studied in this thesis is real time data mining in a bit stream. A novel optoelectronic logic gate has been developed for this application and used to detect an 8 bit long target pattern. Also another approach based on orthogonal Hadamard codes have been proposed and explained in detail. Also novel intracavity modulation schemes have been investigated and applied for various applications such as a) improving rational harmonic modelocking for repetition rate multiplication and pulse to pulse amplitude equalization, b) frequency skewed pulse generation for ranging and c) intracavity active phase modulation in amplitude modulated modelocked lasers for supermode noise spur suppression and integrated jitter reduction. The thesis concludes with comments on the future work and next steps to improve some of the results presented in this work.

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<p> Conventional method for testing the total power loss and internal temperature rise of induction motors under full load can often be a complex and costly process. The new phase modulation method for synthetic full-load testing of induction machines has been proven viable, provided the power oscillation in this method can be minimized. This thesis explores two techniques for stabilizing power fluctuation in the new method, and determines the test system's power sensitivities to parameter changes in the equivalent circuit of the induction motors under test.</p> <p> A computer simulation representing the test system used in the new phase modulation method was developed, and an experimental testing facility was built to test the technique devised for suppressing power oscillation in the test system.</p> <p> The results from simulations are analyzed and compared to those obtained from the actual experiments in order to identify the feasible power-suppressing technique, and determine the induction machine parameters responsible for causing power unbalance in the test system.</p> / Thesis / Master of Applied Science (MASc)