短距离光传输中基于直接探测的偏振复用理论与关键技术研究

The communications and processing of Big Data have brought great pressure to the short reach optical systems, because of its ever-increasing requirement on transmission rate. However, the upgrade of transmission systems faced many challenges from cost, speed, and distance. If only depending on the high-effective modulation formats, such as PAM, CAP, DMT, etc., it is very difficult to increase transmission rate up to 100-Gbit/s or above smoothly and reach the target transmission distance. In this project, the optical polarization dimensions will be explored under direct detection to double the transmission rate in a cost-effective manner. Here, four crucial research contents will be investigated, including theoretical model, system design, digital signal processing algorithm and scientific demonstration. The expected innovative contributions of this project are listed as follows. Firstly, the basic principles of polarization multiplexing and de-multiplexing under nonlinear intensity mapping situation will be revealed. Furthermore, the optimum combination rule between dual-polarizations and high level modulation formats will be investigated. Then, the DSP compensation algorithms, which are specifically employed for the polarization multiplexing and direct detection system, will be proposed. Finally, a simulation and experimental platform will be built to evaluate and demonstrate the proposed theory model, system scheme, and algorithms. Through the above innovative researches and scientific demonstration, the results of this project will provide the important theory and technology supports to double the transmission rate of short reach communications, and effectively promote the development of Big Data networks.

大数据信息交互与处理对短距离光互连传输速率提升提出了迫切的需求，然而底层光传输系统的升级革新面临来自成本、速率、距离的多重挑战，仅依靠PAM、CAP、DMT等高效调制技术难以实现未来单波超100Gbit/s速率的平滑升级与其目标传输距离的覆盖。本项目拟在低成本直接探测条件下探索光偏振维度空间的利用，从理论模型建立、系统方案优化、DSP算法创新、科学实践验证四个方面开展研究工作，揭示非线性光强映射下偏振复用/解复用机理，探索偏振复用与高效调制技术间最优协同机制，研究偏振复用直接探测信号损伤抑制和补偿的特有DSP算法集，搭建仿真与实验平台，对本项目所提出的理论模型、最优化系统方案、信号处理算法进行验证和评估。本项目预期研究成果将为短距离光互连传输速率倍增提供重要的理论与技术支撑，将有效促进大数据承载网络的发展。

新型的简化偏振复用光纤传输系统对数据中心短距光互连速率提升具有重要的研究与应用价值。本项目主要从理论模型、系统方案、算法设计三个方面入手，研究基于直接检测技术的偏振复用传输理论及关键技术。. 1）在建立完善的理论模型，揭示光强度直接探测下信号多维空间复用原理与规则方面：在面向直接检测的斯托克斯空间中，分析了多输入多输出（MIMO）偏振复用信道传输矩阵的特性，确定了基于不同检测结构下，信道光偏振状态（SOP）、噪声、接收机分支比等相互作用机理，确定了其对信号性能的影响，建立了一套完整的理论分析体系，为后续系统设计与系统性能估计提供理论支撑。. 2）在基于距离细分的 PDM-DD 传输系统最优化方案研究方面，提出了基于偏振复用的DMT直检（PM-DMT-DD）系统、提出了基于SSB-OFDM与DMT混合偏振复用单PD直检系统、提出了部分琼斯与斯托克斯分量混合接收的PDM-MQAM系统，可以分别适用于SR/LR、ER光互连传输场景。. 3）在面向短距离光互连数字信号处理算法研究方面，基于直接检测的超奈奎斯特(DD-FTN)算法、基于误差表格生成的联合均衡(JEEG)算法等补偿窄带宽效应和器件非线性损伤的新型DSP算法，并结合了PAM、CAP等多种调制格式开展了应用研究。. 为了对上述理论、系统方案、信号处理算法进行分析验证，项目组搭建了一套完善的短距离光传输系统的仿真分析平台与实验验证平台。面向SR/LR光互连传输场景，实现了超200Gbit/s 信号传输，面向ER光互连传输场景，实现了超100Gbit/s信号传输。在四年的项目执行期间内，已顺利完成了各项指标要求，相关项目研究成果得到了华为公司的关注，已联合提交技术发明专利两项，将为促进短距离光互连技术发展提供支撑。