A probabilistically shaped CAP modulation method employing multiple subsets mapping with symbol classification for a short reach communication

This paper proposes a novel probabilistically shaped carrierless amplitude/phase (CAP) modulation method employing multiple subsets mapping with symbol classification for a short reach communication. This method can classify the original data into multiple subsets of symbols carrying different amounts of bits, and then, map the symbols with different probabilities in the subsets to the different regions of the constellation to reduce the average signal power, thus improving the system bit error rate (BER) performance. An experiment demonstrating 21.8 Gb/s PS-CAP-12 data transmission employing the proposed method over 25 km standard single-mode fiber is successfully carried out. Experiment results show that the proposed scheme outperforms the traditional CAP-16 modulation by 2 dB improvement in receiver sensitivity at a BER of 1 × 10^-3, which suggests the superiority of our proposed scheme for a future short reach communication.