Probabilistic Shaping for 56-Gbps PAM-4 Signalling Over 8-GHz-Bandwidth VCSEL-Modulated Optical Interconnection Links

In this paper, probabilistic shaping for PAM-4 signalling at 56 Gbps is demonstrated for the first time. Experiment is carried out over 8-GHz-bandwidth VCSEL-modulated optical interconnection links with significantly reduced BER due to probabilistic shaping.