Timing Recovery Algorithm Selection for Duo-Binary Signal Used in Next Generation 25G-EPON

Abstract

Low complexity and effective symbol timing recovery (STR) algorithm is a serious challenge for high speed NG-EPON system with 25 Gb/s serial bit-rate per channel. In this paper, the frequently used nonlinear function based timing algorithms are compared in 25 Gb/s Duo-binary transmission system through simulation and experiment. Both simulation and experiment results show that absolute-law based STR (AL-STR) algorithm has minimum timing jitter and lowest computational complexity for Duo-binary receiver. The jitter of STR caused by the nonideal Duo-binary signal is also investigated by simulating different bandwidths of the commercial 10G optical devices. Results show that there are only little effect on STR performance when the –3 dB bandwidth changes from 6 to 8.75 GHz. Maximum likelihood sequence estimation (MLSE), linear and nonlinear equalizer are, respectively, performed after STR in 10G optics-based 25 Gb/s Duo-binary receiver. An optical power sensitivity of –25.6 dBm can be obtained with AL-STR and MLSE.