Beyond 100G passive optical networks (PONs) will be required to meet the ever-increasing traffic demand in the future. Coherent optical technologies are the competitive solutions for the future beyond 100G PON but also face challenges such as the high computational complexity of digital signal processing (DSP). A high oversampling rate in coherent optical technologies results in the high computational complexity of DSP. Therefore, DSP running in a non-integer-oversampling below 2 samples-per-symbol (sps) is preferred, which can not only reduce computational complexity but also obviously lower the requirement for the analog-to-digital converter. In this paper, we propose a non-integer-oversampling DSP for meeting the requirements of coherent PON. The proposed DSP working at 9/8-sps and 5/4-sps oversampling rates can be reduced by 44.04% and 40.78% computational complexity compared to that working at the 2-sps oversampling rate, respectively. Moreover, a 400-Gb/s-net-rate coherent PON based on digital subcarrier multiplexing was demonstrated to verify the feasibility of the non-integer-oversampling DSP. There is almost no penalty on the receiver sensitivity when the non-integer-oversampling DSP is adopted. In conclusion, the non-integer-oversampling DSP shows great potential in the future coherent PON.

翻译：超越100G的无源光网络（PON）将需要满足未来不断增长的流量需求。相干光技术是未来超越100G PON的竞争性解决方案，但也面临着数字信号处理（DSP）计算复杂度高等挑战。相干光技术中的高过采样率会导致DSP计算复杂度的增加。因此，优选工作在低于每个符号2个样本（sps）的非整数过采样DSP，这不仅能够降低计算复杂度，还能明显降低对模数转换器的要求。本文提出了一种满足相干PON要求的非整数过采样DSP。所提出的DSP在9/8-sps和5/4-sps过采样率下工作，相较于在2-sps过采样率下工作，计算复杂度分别降低了44.04%和40.78%。此外，基于数字子载波复用的400-Gb/s净速率相干PON被用于验证非整数过采样DSP的可行性。当采用非整数过采样DSP时，接收机灵敏度几乎无代价。综合而言，非整数过采样DSP在未来相干PON中展现出巨大潜力。