Flexible Coherent Optical Access: Architectures, Algorithms, and Demonstrations
Ji Zhou, Z. Z. Xing, Haide Wang, Kuo Zhang, Xi Chen, Qiguang Feng, Keshuang Zheng, Yijia Zhao, Zhen Dong, Tao Gui, Zhicheng Ye, Liangchuan Li
Abstract
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 50 Gb/s line rate. Recently, 50 G PON has become mature gradually, which means it is time to discuss beyond 50 G PON. For ensuring an acceptable optical power budget, beyond 50 G 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 reduce the cost of ONUs greatly. Meanwhile, continuous-mode and burst-mode digital signal processing (DSP) algorithms are proposed for dealing with downstream and upstream signals, respectively. Based on the architectures and algorithms, we experimentally demonstrate the first real-time TFDMA-based coherent PON where 50 Gb/(s × subcarrier) continuous downstream signal and 12.5 Gb/(s × subcarrier) burst upstream signal are processed in real time. Owing to the independent subcarrier processing, it has the potential to support peak line rates of downstream 200 Gb/s (i.e. four subcarriers) and upstream 100 Gb/s (i.e. eight subcarriers). Significantly, the proposed architectures and algorithms have been sufficiently verified by real-time demonstrations. In conclusion, the proposed technologies for the coherent PON make it more possible to be applied in the future beyond 50 G PON.