Polarization demultiplexing scheme for probabilistic shaping Stokes vector direct detection systemusing extended Kalman filter

摘要

A polarization demultiplexing (PolDemux) scheme using extended Kalman filter (EKF) is proposed to work in probabilistic shaping Stokes vector direct detection (PS SV-DD) system which has a good performance in the rotation of state of polarization (RSOP) compensation with lower optical signal to noise ratio (OSNR) requirement. As the ideal constellation points for the probabilistically shaped (PS) signal quite distinguished from the uniformly distributed signal in Stokes space, the algorithm of PolDemux will be somewhat different. To handle this problem, we propose a PolDemux scheme which can be suitable for both uniformly distributed quadrature amplitude modulation (QAM) signal and PS QAM signal. A 28GBaud Nyquist PS SV-DD system is constructed for performance evaluations. Different PolDemux algorithms are implemented for comparisons. Four different PS 16-QAM signals with different probability distributions and a PS 64-QAM signal with the entropy of 4bit/symbol are used to check the performances in the PS SV-DD system. The simulation results verify that the proposed scheme has the capability of RSOP tracking speed up to 41Mrad/s. Moreover, the proposed scheme performs better comparing with other algorithms, no matter what RSOP impairment model is chosen, either the model with 2 parameters or a universal model with 3 parameters compared with other PolDemux algorithms.