Polar encoded probability shaping for highly reliable 7-core fiber optical communication system based on prefix-free code distribution matching

Abstract

A highly reliable optical orthogonal frequency division multiplexing (OFDM) system based on systematic polar encoded prefix-free codebook distribution matching (PCDM) is proposed. The PCDM is used to convert the uniform binary data into the unipolar coded amplitude symbols with the target probability distribution, which are then encoded by systematic polar code to maintain non-uniform probability distribution. The redundant parity bits generated by polar encoding are used as signs, map to the bipolar amplitude symbols as the real or imaginary part of the final constellation symbols when combined with the unipolar amplitude symbols. The proposed scheme generates a polar encoded probability-shaped 16 quadrature amplitude modulation (PS-Polar-16QAM) OFDM signal, which improves the bit error rate (BER) performance of the optical transmission system. The transmission of a 70 Gb/s polar encoded PS-Polar-16QAM-OFDM signal over a 2 km seven-core fiber is demonstrated experimentally. In comparison to normal-16QAM-OFDM without polar code and PCDM, the polar encoded PS-Polar-16QAM-OFDM achieves about 3.65 dB gain in receiver sensitivity at a BER of 10−4. The proposed polar encoded PS-Polar-16QAM-OFDM based on PCDM has a broad application prospect in a low-cost and reliable optical access system due to its good BER performance.