Low-Complexity QPSK Partitioning Assisted Carrier Phase Recovery for CS-NFDM PS-64QAM System

We propose a QPSK partitioning assisted (QPA) carrier phase recovery (CPR) scheme for continuous spectrum nonlinear frequency division multiplexing (CS-NFDM) probabilistic shaping (PS)-64 quadrature amplitude modulation (QAM) system. Firstly, the QPSK-shaped constellation points are picked out among the 64QAM constellation points. Secondly, the selected constellation points are extended to the outermost ring. Finally, the modulation information is removed from the signals to perform CPR. The simulation results of 32 GBaud CS-NFDM PS-64QAM system demonstrate that the transmission distance of our proposed QPA scheme can reach up to 880 km, with a maximum linewidth (LW) tolerance up to 1.6 MHz. The QPA scheme is applicable to the case where the entropy is within the range of [5.1, 5.9] bit/symbol. Additionally, when the number of subcarriers is 256, the complexity of our scheme is only 63.59% as that of decision directed free (DDF) scheme.