Multi-wavelength optical Kerr effects in high nonlinearity single mode fibers and their applications in nonlinear signal processing.

Kwok Chi Hang.Thesis (M.Phil.)--Chinese University of Hong Kong, 2006.Includes bibliographical references.Abstracts in English and Chinese.Chapter Chapter 1 --- Introduction --- p.1Chapter 1.1 --- All-Optical Signal Processing in Optical Communications --- p.2Chapter 1.2 --- Fiber-Based Optical Kerr Nonlinear Switches --- p.5Chapter 1.3 --- Highly Nonlinear Fibers --- p.6Chapter 1.4 --- Objectives and Scope of Study --- p.8Chapter 1.5 --- Summary --- p.9Chapter Chapter 2 --- Optical Nonlinearity --- p.14Chapter 2.1 --- Fiber Nonlinearity --- p.15Chapter 2.2 --- Dispersion --- p.21Chapter 2.3 --- Cross-Phase Modulation --- p.26Chapter 2.4 --- Cross-Polarization Modulation --- p.29Chapter Chapter 3 --- Fibers: The Nonlinear Media --- p.47Chapter 3.1 --- Average Dispersion --- p.48Chapter 3.2 --- Longitudinal Dispersion Map --- p.53Chapter 3.3 --- Nonlinear Refractive Index and Nonlinear Coefficient --- p.57Chapter 3.4 --- Electrostrictive Contribution --- p.62Chapter 3.5 --- List of the Fiber Properties --- p.66Chapter Chapter 4 --- Multi-Wavelength Nonlinear Signal Processing --- p.69Chapter 4.1 --- Challenge --- p.70Chapter 4.2 --- Applications --- p.72Chapter 4.3 --- Proposed System Application --- p.110Chapter Chapter 5 --- Conclusion and Future Work --- p.114Chapter 5.1 --- Comparisons between Proposed and Existing Approaches --- p.114Chapter 5.2 --- Conclusion of the Dissertation --- p.115Chapter 5.3 --- Prospects and Directions of Future Work --- p.117Appdenix A Numerical Model for Dispersion Calculation --- p.IAppdenix B Simulation Model of Wide Band Cross-Polarization Switch --- p.IIIAppdenix C Simulation Model of Spectral Filtering under XPM --- p.VIList of Publications --- p.I

単一もしくは混合フォーマット光ネットワークのための光ファイバの四光波混合を用いた光信号処理

As data rates in broadband optical networks continue to grow, all optical signal processing technologies are expected to become important for future high bit-rate communication systems to address the growing demand for network flexibility, low cost and high bandwidth. Along the line of the capacity increased, many new modulation formats have been introduced. The most straightforward format is on-off-keying (OOK) modulation format. The state of art reveals that the differential phase-shift keying (DPSK)modulation format is the best candidate for high-speed long haul network segment, while OOK is suitable for short reach network segment. However, the next generation transmission systems will more likely employ mixed modulation formats. Thus, the shift towards these changes to be applied in many applications is necessary. Hence, it is worth investigating several signal processing, not only by using a single modulation format but also mixed modulation formats. In order to realize such systems, the scheme requirement must be transparent to modulation format and bit-rate. One of the promising candidates is based on the third-order nonlinear susceptibility x(3) in a nonlinear fiber, which is also called four-wave mixing (FWM). Fiber-based FWM, in a highly nonlinear fiber (HNLF) is a preferable choice due to its fast nonlinear response and high conversion efficiency. FWM technique can be also be used as an all-optical AND logic gates and signal regenerator. In optical fiber communication systems, signal distortions due to chromatic dispersion in fiber dominantly limit transmission length and bit-rate. An improvement in the distorted signal is crucially needed, as the processed signal will become more degraded after some distance of transmission. Optical phase conjugation (OPC) and tunable dispersion compensation modulator (TDCM) are two attractive schemes used to increase the signal robustness in transmission systems. It is also desirable if a practical function such as flexible picosecond width-tunability can be accomplished. The advantageous of flexible converted pulse width are for the creation of higher bit-rate signals and the ability to support wider bandwidth requirements. In this thesis, the experimental demonstration using compressed RZ clock from Raman adiabatic-soliton compressor (RASC) and continuous wave (CW) signal as a pump signals in all-optical fiber-based FWM AND-gate using singleand mixed OOK-DPSK modulation formats in many applications can be realised. The applications including: all-optical nonreturn-to-zero(NRZ)-to-return-to-zero(RZ) wavelength-waveform conversions, all optical wave-length multicasting, all channel OTDM demultiplexing, and transmission performance between the midspan of OPC and TDCM. We experimentally demonstrated an all-optical NRZ-DPSK-to-RZ-DPSK waveform-wavelength conversion with flexible picosecond width-tunability and signal regeneration with reshaping functionality. The scheme is based on a RASC and a fiber-based AND-gate. In the first demonstration, we demonstrate waveform-wavelength conversion of a 10-Gb/s DPSK signal without input signal degradation over wide input-output wavelength ranges. The measurement results of the converted RZ-DPSK signal are pedestal-free, and its converted pulse width can be adjusted by tuning the Raman pump power in RASC. Further investigation of the regenerative properties due to chromatic dispersion is conducted at several Raman pump power settings over 40-km standard single-mode fibers (SSMFs) without dispersion compensation. Also, low power penalty with an error-free operation is obtained for the RZ-DPSK regenerated converted signal. Next, an all-optical 1-to-6 wavelength multicasting of a 10-Gb/s picosecond-tunable-width converted OOK data signal using a parametric pulse source from a RASC is experimentally demonstrated. Width-tunable wavelength multicasting within the C-band with approximately 40.6-nm of separation with various compressed RZ data signal inputs has been proposed and demonstrated. The converted multicast pulse widths can be flexibly controlled down by tuning the Raman pump powers of the RASC. Nearly equal pulse widths at all multicast wavelengths are obtained. Furthermore, wide open eye patterns and low power penalties at the 10??9 BER level are found. An all-optical demultiplexing of 40-Gb/s hybrid OTDM mixed format channels by using RASC-flexible control-window is also demonstrated. Error-free operations with less than 1.3-dB power penalties were obtained and this scheme is expected to be scalable toward higher bit-rates. Further demonstration related to NRZ-to-RZ waveform-wavelength conversion for 4 x 10-Gb/s multichannel mixed OOK-DPSK data formats, deploying a single FWM and RASC has been done. The fiber-based switch in HNLF based on parametric process between mixed data signals and the compressed RZ clock from RASC. By flexibly tuning the Raman pump power from RASC in between 0.20 and 0.90 W, high quality converted signal can be achieved. Bit-error-rate measurements show negative power penalties for the obtained RZ signals with pedestal-free pulses. Finally, we demonstrated the transmission performance between the midspan of TDCM and OPC schemes with specialty using multichannel-mixed OOK and DPSK format. The OPC scheme has the advantage over the penalties performance compared to TDCM scheme.電気通信大学201

Processamento ótico de sinal para sistemas de comunicações óticas

Doutoramento em Engenharia FísicaO processamento ótico de sinal é uma alternativa possível para melhorar o desempenho e eficiência de sistemas de comunicações óticas, mas o seu estágio atual de desenvolvimento é ainda insuficiente para aplicações em sistemas reais. De forma a inverter esta situação, novas estratégias e pos-sibilidades para processamento ótico de sinal são aqui investigadas, com ênfase em conversão de comprimento de onda, regeneração de fase e amplificação sensível à fase em dispositivos de niobato de lítio com inversão periódica dos domínios ferroelétricos e fibras fortemente não-lineares. Um novo método para o desenho do perfil de inversão dos domínios fer¬roelétricos nos dispositivos de niobato de lítio de acordo com um espetro de conversão alvo é investigado nesta tese. O método proposto é validado numericamente e através da produção de um dispositivo real com largura de banda de conversão de 400 GHz. O dispositivo produzido é utilizado para conversão de onda multicanal de oito sinais modulados em fase, com a possibilidade adicional de sintonizar o comprimento de onda dos sinais con¬vertidos. Observa-se a existência de um compromisso entre elevada largura de banda de conversão e eficiência do dispositivo. São também investigadas nesta tese conversão e permuta de comprimento de onda tolerantes ao ruído de fase adicionado por fontes de bombeamento. Demonstra-se neste trabalho que a utilização de fontes de bombeamento coerentes permite evitar a adição de ruído de fase aos sinais convertidos. Nesta tese é também analisada analítica e numericamente amplificação sensível a fase baseada em dispositivos de niobato de lítio com inversão periódica dos domínios ferroelétricos para configurações de amplificadores de um, dois ou quatro modos. É ainda avaliada a possibilidade de ge¬rar ondas correlacionadas e de realizar amplificação sensível a fase num único dispositivo com propagação bidirecional. Com base neste esquema, demonstra-se regeneração de fase de sinais modulados em fase, porém com ganho limitado devido à baixa eficiência de conversão dos dispositivos e com desempenho afetado por instabilidades térmicas e foto refrativas. Mo¬tivado por estas limitações, demonstra-se amplificação de elevado ganho num amplificador sensível à fase de quatro modos, construído com uma fibra fortemente não-linear em vez de um dispositivo de niobato de lítio. Por fim, é efetuada uma análise numérica do impacto de utilizar amplifica¬dores sensíveis à fase em vez de amplificadores de fibra dopada com érbio no alcance em transmissão ponto a ponto de sinais e na amplificação e regeneração em redes óticas. Demonstra-se que amplificadores sensíveis à fase são mais vantajosos para formatos de modulação avançados e siste¬mas compostos por ligações óticas longas. As simulações assumem mode¬los simplificados para o ganho e ruído dos amplificadores, bem como uma versão modificada do modelo de ruído Gaussiano para estimar a potência das distorções não-lineares em sistemas com compensação total da dispersão cromática no final de cada segmento de fibra entre amplificadores.All-optical signal processing techniques are a possible way to improve the performance and efficiency of optical communication systems, but the cur¬rent stage of development of such techniques is still unsatisfactory for real- world implementation. In order to invert this situation, new strategies and possibilities for all-optical signal processing are investigated here, with a particular focus on wavelength conversion, phase regeneration and phase- sensitive amplification in periodically poled lithium niobate waveguides and highly nonlinear fibers. A new and flexible method to design the poling pattern of periodically poled lithium niobate devices according to a target conversion spectrum is inves¬tigated in this work. The proposed method is validated through numerical simulations and by producing a real device with broad conversion bandwidth of 400 GHz. The device is then used for multichannel wavelength conversion of eight phase-modulated signals, with the additional possibility to tune the wavelength of the converted signals. A trade-off between high conversion bandwidth and conversion efficiency is observed. Advanced wavelength conversion and wavelength exchange tolerant to the phase noise added by the pump lasers are also investigated. It is shown that the additional phase noise transferred to the converted signals is eliminated by using coherent pumps, generated from the same light source. Phase-sensitive amplification based on periodically poled lithium niobate devices is also investigated in this thesis by numerically comparing the gain properties for one-, two- and four-mode configurations. The possibility to si¬multaneously generate correlated waves and observe phase-sensitive amplifi¬cation in a single device with bidirectional propagation is also demonstrated. Using such scheme,"black-box" phase regeneration of phase-encoded sig¬nals is experimentally demonstrated, albeit with limited net gain due to the low conversion efficiency of the device, and the limited reliability due to thermal and photorefractive instabilities. Motivated by such limitations, high-gain amplification in a four-mode phase-sensitive amplifier built with a highly nonlinear fiber instead of a periodically poled lithium niobate is demonstrated. Finally, the impact of using phase-sensitive amplifiers instead of common erbium-doped fiber amplifiers on the reach in point-to-point transmission and on the amplification and regeneration requirements in optical transport networks is numerically investigated. The calculations show that phase- sensitive amplifiers are particularly advantageous when considering high- order modulation formats and for transport networks comprised by long links. The numerical simulations are performed using simplified models for the gain and noise properties of the amplifiers, and a modified enhanced Gaussian noise model to estimate the power of the nonlinear distortions in systems with full dispersion compensation at the end of each span of fiber