Phase rearrangement shell mapping in single-span nonlinear optical fiber communication system

The importance of single-span systems is emphasized by the fact that they currently constitute the fastest growing section of the fiber communication markets. In such systems, the correlation time of the nonlinear phase noise is too short to allow the nonlinear phase-noise mitigation such as adaptive phase-recovery or equalization, while it is sufficient for the shaping approaches. The multi-dimensional (MD) coded-modulation based standard shell mapping (SM) algorithm can realize signal shaping and mitigate the nonlinear phase noise in single-span optical fiber transmissions. However, the standard SM algorithm has poor performance resulted from the decoding penalty in two-dimensional (2D) decoding with a low signal-to-noise (SNR) ratio. In this paper, we propose a phase rearrangement shell mapping (PRSM) algorithm to improve the 2D decoding performance by rearranging the constellation sequence in order of signal phase for each shell. This proposed technique is verified through the simulation of a 5 x 70-GBaud 4D/8D modulated signal in a 5-channel wavelength division multiplexing (WDM) system after a single span transmission of 100-km standard single mode fiber (SSMF). We also conduct an experiment to verify the performance of 3 x 45-GBaud 4D/8D-16QAM with PRSM algorithm after unrepeated transmission of 100-km SSMF. The simulation and experimental results show that the Q2 factor gain of PRSM-4D/8D-16QAM is about 0.2 similar to 0.3 dB compared with standard SM-4D/8D-16QAM using 2D decoding. There is about 1.6-dB or 1.8-dB launch optical power (LOP) dynamic range improvement by PRSM compared with standard SM for 4D/8D-16QAM, respectively.