Sensitivity Gains by Mismatched Probabilistic Shaping for Optical Communication Systems

TL;DR

This paper demonstrates that probabilistic shaping of QAM signals can significantly improve optical communication sensitivity, with robustness to SNR mismatch, using only a few shaping distributions for 64QAM.

Contribution

It introduces a method to achieve sensitivity gains in optical systems through probabilistic shaping and shows robustness to SNR mismatch with minimal distributions.

Findings

Sensitivity gains of 0.43 dB for 16QAM and 0.8 dB for 64QAM.

Robustness of probabilistic shaping to SNR mismatch.

Only four shaping distributions needed for 64QAM with 0.1 dB SNR penalty.

Abstract

Probabilistic shaping of quadrature amplitude modulation (QAM) is used to enhance the sensitivity of an optical communication system. Sensitivity gains of 0.43 dB and 0.8 dB are demonstrated in back-to-back experiments by shaping of 16QAM and 64QAM, respectively. Further, numerical simulations are used to prove the robustness of probabilistic shaping to a mismatch between the constellation used and the signal-to-noise ratio (SNR) of the channel. It is found that, accepting a 0.1 dB SNR penalty, only four shaping distributions are required to support these gains for 64QAM.