A Novel Pilot-Aided Polarisation Joint Carrier Phase Estimation Method for Set-Partitioning QAM Systems

In this paper, we propose a novel 4-D CPR method based on the enhanced pilot-aided (PA) carrier phase recovery (CPR) method aided with maximum likelihood (ML) phase estimation for Set-Partitioning quadrature amplitude modulation (SP-QAM) signals. A polarisation joint PA-CPR scheme with the estimation for the phase offset is implemented and a ML phase estimation method based on four dimensional (4-D) decision is utilized to take advantage of the increased Euclidean distance. The simulation results demonstrate that utilising the 7% hard-decision forward error correction (HE-FEC) threshold as a benchmark, the proposed method could achieve optical signal-to-noise ratio (OSNR) gains of approximately 0.7 dB in comparison to the traditional PA+ML CPR method.