Abstract

Timing recovery is critical for synchronizing the clocks at the transmitting and receiving ends of a digital coherent communication system. The core of timing recovery is to determine reliably the current sampling error of the local digitizer so that the timing circuit may lock to a stable operation point. Conventional timing phase detectors need to adapt to the optical fiber channel so that the common effects of this channel, such as chromatic dispersion (CD) and polarization mode dispersion (PMD), on the timing phase extraction must be understood. Here we exploit the cyclostationarity of the optical signal and derive a model for studying the CD and PMD effect. We prove that the CD-adjusted cyclic correlation matrix contains full information about timing and PMD, and the determinant of the matrix is a timing phase detector immune to both CD and PMD. We also obtain other results such as a completely PMD-independent CD estimator, etc. Our analysis is supported by both simulations and experiments over a field implemented optical cable.

Joint CD and PMD monitoring based on a pair of low-bandwidth coherent receivers

Yuli Chen, Qi Sui, Zhaohui Li, Zihao Liang, and Weiping Liu
Opt. Express 24(23) 26756-26765 (2016)

Modified square timing error detector with large chromatic dispersion tolerance for optical coherent receivers

Dawei Wang, Zikang Su, Hao Jiang, Guowei Liang, Qianxin Zhan, and Zhaohui Li
Opt. Express 29(13) 19759-19766 (2021)

Multi-parameter estimation resistant to the random polarization effect for coherent optical receivers

Meng Qiao, Yingyu Chen, Dawei Wang, and Zhaohui Li
Opt. Express 31(11) 18454-18467 (2023)

All-Digital Timing Recovery and Adaptive Equalization for 112 Gbit∕s POLMUX-NRZ-DQPSK Optical Coherent Receivers

Xian Zhou, Xue Chen, Weiqing Zhou, Yangyang Fan, Hai Zhu, and Zhiyu Li
J. Opt. Commun. Netw. 2(11) 984-990 (2010)

Cyclostationarity-based joint monitoring of symbol-rate, frequency offset, CD and OSNR for Nyquist WDM superchannels

Maria Ionescu, Masaki Sato, and Benn Thomsen
Opt. Express 23(20) 25762-25772 (2015)