Real-time fast polarization tracking based on polarization phase locking least mean square algorithm

We propose a fast polarization tracking scheme based on polarization phase locking least mean square (LMS) algorithm and experimentally demonstrate it in real-time implementation with a quasi-feed-forward digital signal processing (DSP) architecture. It has the advantages of no frequency/phase offset feedback requirement from the carrier recovery stage. The tracking performance of the proposed algorithm is verified in both simulation and real-time coherent transmission systems. It can track the state of polarization (SOP) variations up to 12 Mrad/s and 3.3 Mrad/s in 100-Gb/s QPSK and 400-Gb/s 16QAM simulation system, and can track 2.5 Mrad/s in 10-Gb/s QPSK real-time experiment, which has great improvement over conventional LMS algorithm.