Burst-Mode Signal Reception for 200 G Coherent Time and Frequency Division Multiplexing Passive Optical Network

The coherent passive optical network (PON) is a cost-effective point-to-multipoint solution to accommodate the ever-increasing traffic demands in the future optical access network. Recently, time and frequency division multiplexing (TFDM) coherent PON have attracted increasing interest, due to its advantages of providing low latency access and flexible bandwidth allocation. One critical challenge for TFDM-PON system is the upstream burst-mode digital signal processing (DSP). DSP should converge fast in the specific time slot to ensure low latency for subcarrier allocation. The conventional subcarrier recognition and demultiplexing are realized in the frequency domain. The process of time-frequency conversion introduces extra computational complexity if the burst-mode DSP use time-domain algorithms. In this paper, we propose and experimentally demonstrate a data-aided DSP scheme for burst-mode detection in coherent TFDM-PON. Subcarrier demultiplexing is implemented in the time domain by using coarse and fine filtering. Coarse and fine filtering are achieved by convolving the signal with finite impulse response (FIR) pulse-shaping filters. Least square (LS) algorithm is used for channel estimation achieving fast convergence. With a 79.36-ns training sequence, −37.5-dBm and −29-dBm sensitivities are achieved for QPSK and 16QAM signal-based 200 G TFDM-PON with four subcarriers after 20-km fiber transmission.