Open AccessJoint clock recovery and feed-forward equalization for PAM4 transmission
Author(s) -
Honghang Zhou,
Yan Li,
Dan Lü,
Lei Yue,
Chao Gao,
Yuyang Liu,
Ruibin Hao,
Zhentang Zhao,
Wei Li,
Jifang Qiu,
Xiaobin Hong,
Hongxiang Guo,
Yong Zuo,
Jian Wu
Publication year - 2019
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.27.011385
Subject(s) - computer science , clock recovery , transmission (telecommunications) , forward error correction , bit error rate , electronic engineering , intersymbol interference , modulation (music) , equalization (audio) , pulse amplitude modulation , real time computing , channel (broadcasting) , algorithm , jitter , telecommunications , clock signal , pulse (music) , physics , decoding methods , engineering , detector , acoustics
With the rapid development of cloud services, data-center applications and the Internet of Things, short-reach communications have attracted much more attention in recent years. 4-level pulse amplitude modulation (PAM4) is a promising modulation format to provide both high data rate and relatively low cost for short-reach optical interconnects. In this paper, a joint clock recovery and feed-forward equalization algorithm (CR-FFE) is proposed to simultaneously eliminate the inter-symbol interference (ISI) and track large sampling clock offset (SCO) in PAM4 transmission. The algorithm estimates timing error according to the difference between two tap coefficients of fractionally spaced equalizers, thus solving the problem of incompatible prerequisites between clock recovery and channel equalization. A 10GHz directly modulated laser (DML) based 50-Gbit/s PAM4 transmission experiment is implemented to investigate the performance of the proposed algorithm. Experimental results show that the proposed CR-FFE algorithm can resist SCO up to 1000 ppm after 40 km standard single-mode fiber (SSMF) transmission under the 2x10 -2 SD-FEC BER threshold, which is dramatically improved comparing with that of 20 ppm in traditional CR cascaded by FFE algorithm.