Modulation strategies and phase noise mitigation for spectrally efficient optical coherent communications

光纤提供极低衰减、高带宽(太赫兹)的通信介质，是现代通信网络的主干。在过去的几十年里，通信的每比特成本呈指数级下降，然而，通过利用具有相干检测和高阶调制的波分复用，我们正在迅速接近容量极限。尽管如此，数据中心和本地网络中的数据处理水平不断提高，继续推动对光纤上更高信息密度的需求。 该方案应用实验、建模和数值计算技术来研究相干检测系统中的新调制策略。重点将集中在光纤中的空间多路复用以及伴随的交叉模干涉和相位噪声增强。空间多路复用试图通过利用准正交信道在相同的光学介质中创建新的通信信道--准正交信道是因为材料和器件中的物理缺陷破坏了理论正交性。必须对光纤和多路复用器诱导的模式相关性进行关键分析，以确定哪种空间多路复用方法(如果有的话)可以在合理的复杂性下增加光纤的信息承载能力，以进行数字信号处理。我们将在相同的分析框架内考察用于空间多路复用的线偏振和轨道角动量导模的性能，以量化和阐明它们的相对优点。我们的长期目标是开发用于检测光纤(多芯光纤、少模光纤和轨道角动量变化)中的空间复用的专业知识和实验设施；在支持空间复用的特种光纤设计方面开展合作--使系统分析与设计标准相协调；以及发现受益于空间复用的利基应用。

The optical fiber provides an extremely low attenuation, high bandwidth (terahertz) communications media and is the backbone of modern communications networks. The cost per bit of communications has fallen exponentially over past decades, however we are quickly approaching the capacity limits via exploitation of wavelength division multiplexing with coherent detection and higher order modulation. The increasing level of data manipulations in data centres and in local networks, nonetheless, continues to push demand for greater information density on fibers. This proposal applies experimentation, modeling and numerical techniques to research into new modulation strategies in the context of coherent detection systems. The focus will be on spatial multiplexing in fiber with the concomitant cross modal interference and phase noise enhancement. Spatial multiplexing attempts to create new communications channels in the same optical media by exploiting quasi orthogonal channels - quasi because physical imperfections in materials and devices destroy the theoretical orthogonality. Critical analysis of the fiber and multiplexer induced modal correlations must be examined to determine which, if any, of the spatial multiplexing approaches can increase the information bearing capacity of fiber at reasonable complexities for digital signal processing. We will examine the performance of linearly polarized and orbital angular momentum guided modes for spatial multiplexing within the same analytical framework to quantify and elucidate their relative merits. Our long term goals are to develop expertise and experimental facilities for the examination of spatial multiplexing in optical fibers (multiple core fiber, few mode fibers and orbital angular momentum varieties); develop collaboration in design of specialty fibers supporting spatial multiplexing - reconciling systems analysis with design criteria; and to discover niche applications benefiting from spatial multiplexing.