Tens to Hundreds of Mrad/s Fast Polarization Tracking and Demultiplexing Using Angle-Plus-Phase Algorithm in Stokes Space

A fast polarization tracking and demultiplexing algorithm in polarization-division-multiplexing (PDM) systems is proposed and demonstrated. The scheme utilizes two optimizing parameters in Stokes Space, including the polarization angle and the phase information. In addition to its transparency to modulation formats, the angle-plus-phase algorithm (APA) could provide fast convergence up to >100-Mrad/s polarization tracking speed. Compared to common polarization demultiplexing algorithms such as constant modulus algorithm (CMA) and linear Kalman filter (LKF), experimental results show that the polarization tracking capability of the proposed APA algorithm is significantly improved without sacrificing the transmission performance. Specifically, compared to CMA, the tracking speed can be improved from 9-Mrad/s to 160-Mrad/s for PDM quadrature phase shift keying (PDM-QPSK) signals. Furthermore, compared to CMA and LKF, APA has the best tracking performance, and the tracking speed can be reached to 34-Mrad/s for PDM 16 quadrature amplitude modulation (PDM-16QAM) signal.