Advanced decision scheme to mitigate phase impairments in coherent optical transmission systems

An advanced decision scheme is proposed to mitigate phase impairments in coherent optical communication systems. First, the centers of received signals affected by nonlinear impairment are calculated using tangential and radial hierarchical clustering. Then signal decisions with phase noise and nonlinear impairment tolerance are achieved through phase subsequence clustering, resulting in the improvement of transmission performance and the reduction of the computational complexity. The proposed scheme was simulated and experimentally verified in a 216 Gbit/s uniform and probabilistic-shaped (PS) polarization division multiplexing (PDM) 64-quadrature amplitude modulation (64-QAM) coherent optical communication system. The results indicate that the proposed scheme achieves a power budget increase of 0.1 dB in the uniform 64-QAM system and 1.7 dB in the PS 64-QAM system, respectively, compared to the cascaded schemes of 2-stage blind phase search and K-means. Furthermore, the proposed scheme reduces the computational complexity by 86.5% and 93.9%, respectively.