超400G短距离光互联系统的关键技术研究

Due to its attractive features including high spectrum efficiency, transparent to modulation formats, low system complexity and low cost, direct-detection orthogonal-frequency-division-multiplexing (DD-OFDM) has been proved to be a good candidate for beyond 400G short reach optical inter-connection. System performance degradation is currently always induced by high frequency attenuation, frequency selective fading and I/Q imbalance in the high capacity DD-OFDM. In this project, it is the first time to propose a novel complete pre-equalization scheme in the transmitter which includes high frequency attenuation and I/Q imbalance compensation. We theoretically analyze the exact relationship between pre-compensation co-efficient and the degree of SNR degradation to optimize pre-compensation co-efficient and improve pre-equalization theory. We try to propose and design novel fiber dispersion immune system architectures to solve signal-to-noise ratio (SNR) competition relationship between optical carrier and signal in the proposed fiber dispersion free systems. We try to realize decision-directed least mean square (DD-LMS) equalizer in the receiver to further improve the system BER performance of DD-OFDM with high order QAM modulation formats. In this project, we solve the key technical problems and pave the way for beyond 400G short reach optical interconnection.

具有高频谱效率、对调制格式透明、低实现复杂度和低系统成本的直接检测OFDM已成为超400G短距离光互联的有效解决方案。目前的大容量直接检测OFDM方案中高频衰减、频率选择性衰减以及I/Q不平衡是导致系统性能恶化的主要因素。本项目创新提出在发送端同时实现高频衰减和I/Q不平衡的完备预补偿，理论分析衰减补偿系数和信噪比降低的定量关系，优化补偿系数并完善信道预补偿理论；研究新型色散免疫系统架构，打破传统色散免疫系统架构中光载波和信号信噪比分配的竞争关系；提出在接收端采用判决导引最小均方误差(DD-LMS)均衡器优化系统性能实现高阶调制格式的OFDM信号传输。解决超400G短距离光互联系统中的关键技术问题并为超400G短距离光互联系统铺平道路。

光互连目前主要解决数据中心和超算中心中的机柜和板间的高速互联，下一代的光互连的信息速率将高达400Gbit/s。本项目主要解决目前400G短距离光互连实现中的关键问题。主要开展了以下三个方面的研究：1.高谱效率的调制格式以及相应的数字信号处理算法的开发，调制格式主要包括脉冲幅度调制(PAM)、离散多音频调制(DMT)和非正交频分复用调制(SE-FDM)；2.高效的数字后补偿和预补偿技术，解决如高频衰减、IQ不平衡、非线性效应和窄带干扰等难题；3.高效的复用技术，研究了频分复用(FDM)、波分复用(WDM)和空分复用(SDM)。通过以上三方面的研究，实现了单波长超400G的短距离光互连。解决了超400G短距离光互联系统中的关键技术问题并为超400G短距离光互联系统铺平道路。