Comparison of Geometrically Shaped and Probabilistically Shaped Bit-Loading DMT for Optical Interconnect System

We experimentally demonstrate the transmission performance of the bit-loading discrete multi-tone (DMT) signal in intensity modulation and direct detection (IM-DD) system with a transmission distance of 2km and a net data rate of 108-Gb/s by two different shaping methods. A detailed comparison between the application of geometric shaping (GS) and probabilistic shaping (PS) in bit-loading DMT is presented. With continuous entropy loading for better channel fitting, probabilistically shaped bit-loading DMT achieves 1-dB receiver sensitivity gain compared to the conventional bit-loading DMT and outperforms geometrically shaped bit-loading DMT in the transmission experiment.