To cope with the explosive bandwidth demand, significant progress has been made in the ITU-T standardization sector to define a higher-speed passive optical network (PON) with a 50Gb/s line rate. Recently, 50G PON becomes mature gradually, which means it is time to discuss beyond 50G PON. For ensuring an acceptable optical power budget, beyond 50G PON will potentially use coherent technologies, which can simultaneously promote the applications of flexible multiple access such as time/frequency-domain multiple access (TFDMA). In this paper, we will introduce the architectures, algorithms, and demonstrations for TFDMA-based coherent PON. The system architectures based on an ultra-simple coherent transceiver and specific signal spectra are designed to greatly reduce the cost of ONUs. Meanwhile, fast and low-complexity digital signal processing (DSP) algorithms are proposed for dealing with upstream and downstream signals. Based on the architectures and algorithms, we experimentally demonstrate the first real-time TFDMA-based coherent PON, which can support at most 256 end users, and peak line rates of 100Gb/s and 200Gb/s in the upstream and downstream scenarios, respectively. In conclusion, the proposed technologies for the coherent PON make it more possible to be applied in the future beyond 50G PON.

翻译：为应对爆炸性增长的带宽需求，国际电联电信标准化部门（ITU-T）在定义线路速率为50Gb/s的更高速无源光网络（PON）方面取得了显著进展。近期，50G PON逐渐成熟，这意味着是时候探讨后50G PON技术了。为确保可接受的光功率预算，后50G PON可能采用相干技术，该技术同时可促进灵活多址接入（如时频域多址接入（TFDMA））的应用。本文将介绍基于TFDMA的相干PON的架构、算法与演示。设计了基于超简单相干收发机及特定信号频谱的系统架构，以大幅降低光网络单元（ONU）成本。同时，提出了针对上下行信号处理的快速低复杂度数字信号处理（DSP）算法。基于上述架构与算法，我们实验验证了首个基于TFDMA的实时相干PON，该系统可支持最多256个终端用户，上下行场景的峰值线路速率分别达100Gb/s及200Gb/s。总之，所提出的相干PON技术使其更有可能应用于未来的后50G PON。