Nonlinear optical signal processing for high-speed, spectrally efficient fiber optic systems and networks

Unrestricted The past decade has witnessed astounding boom in telecommunication network traffic. With the emergence of multimedia over Internet, the high-capacity optical transport systems have started to shift focus from the core network towards the end users. This trend leads to diverse optical networks with transparency and reconfigurability requirement. As single channel data rate continues to increase and channel spacing continues to shrink for high capacity, high spectral efficiency, the workload on conventional electronic signal processing elements in the router nodes continues to build up. Performing signal processing functions in the optical domain can potentially alleviate the speed bottleneck if the unique optical properties are efficiently leveraged to assist electronic processing methodologies. Ultra-high bandwidth capability along with the promise for multi-channel and format-transparent operation make optical signal processing an attractive technology which is expected to have great impact on future optical networks.; For optical signal processing applications in fiber-optic network and systems, a laudable goal would be to explore the unique nonlinear optical processes in novel photonic devices. This dissertation investigates novel optical signal processing techniques through simulations and experimental demonstrations, analyzes limitations of these nonlinear processing elements and proposes techniques to enhance the system performance or designs for functional photonic modules.; Two key signal-processing building blocks for future optical networks, namely slow-light-based tunable optical delay lines and SOA-based high-speed wavelength converters, are presented in the first part of the dissertation. Phase preserving and spectrally efficient slow light are experimentally demonstrated using advanced modulation formats. Functional and novel photonic modules, such as multi-channel synchronizer and variable-bit-rate optical time division multiplexer are designed and demonstrated using slow-light tunable delay lines. Deleterious signal degrading effects on SOA-based differential mode wavelength converters are experimentally identified and techniques to alleviate or eliminate them are proposed.; The second part of the dissertation discusses enabling technologies for enhancing the system performance or enriching the system functionalities. Two novel optoelectronic devices, namely the optical injection-locked VCSEL and MEMS actuated micro-disk resonator, are utilized for the demonstration of transmission reach extension and dynamic bandwidth allocation, respectively. Additionally, polarization-based novel optical instruments, such as a polarimeter-enabled optical spectrum analyzer and an all-optical automatic polarization de-multiplexer, are designed and demonstrated. Finally, a 40-Gb/s capable re-circulating fiber loop test-bed is constructed and design guidelines as well as experimental results are discussed in detail.

无限制 过去十年间，电信网络流量呈现出惊人的爆发式增长。随着互联网多媒体应用的兴起，大容量光传输系统（optical transport systems）的关注点已从核心网络转向终端用户。这一趋势催生了对透明度与可重构性有需求的多样化光网络。随着单信道数据速率持续提升，且为实现高容量与高频谱效率而不断缩小信道间隔，路由器节点内传统电子信号处理元件的负载持续攀升。若能有效利用光域的独特光学特性辅助电子处理方法，在光域执行信号处理功能或可缓解速度瓶颈。超宽带宽能力，结合多信道与格式透明运行的前景，使光信号处理（optical signal processing）成为极具吸引力的技术，有望对未来光网络产生深远影响。
针对光纤网络（fiber-optic network）与系统中的光信号处理应用，一项值得追求的目标是探索新型光子器件中的独特非线性光学过程。本论文通过仿真与实验演示，研究新型光信号处理技术，分析这类非线性处理元件的局限性，并提出提升系统性能的技术方案或功能型光子模块的设计思路。
论文第一部分介绍了面向未来光网络的两大关键信号处理模块，即基于慢光的可调谐光延迟线（slow-light-based tunable optical delay lines）和基于半导体光放大器（SOA, Semiconductor Optical Amplifier）的高速波长转换器（wavelength converters）。研究团队采用高级调制格式，实验演示了保相且频谱高效的慢光技术。基于慢光可调谐光延迟线，设计并演示了多信道同步器、可变比特率光时分复用器（optical time division multiplexer）等功能型新型光子模块。针对基于SOA的差分模式波长转换器，研究团队通过实验识别出有害的信号劣化效应，并提出了缓解或消除此类效应的技术方案。
论文第二部分讨论了用于提升系统性能或丰富系统功能的使能技术（enabling technologies）。两款新型光电子器件——光注入锁定垂直腔面发射激光器（optical injection-locked VCSEL）和微机电系统（MEMS, Micro-Electro-Mechanical Systems）驱动的微盘谐振器（micro-disk resonator），分别被用于演示传输距离扩展与动态带宽分配。此外，研究团队还设计并演示了基于偏振原理的新型光学仪器，如具备偏振计功能的光谱分析仪（polarimeter-enabled optical spectrum analyzer）和全光自动偏振解复用器（all-optical automatic polarization de-multiplexer）。最后，搭建了支持40Gb/s速率的循环光纤环路测试平台，并详细讨论了设计指南与实验结果。