Non Binary Polar Codes for Short Reach Optical System Based on an Efficient Channel Model

Next generation short reach optical systems demand forward error correction codes with low latency decoding for ultra reliable data transmission. Polar codes are a new class of capacity achieving codes which outperforms the widely used low density parity check codes, for shorter codeword lengths, as required by short reach optical transmission systems. Short reach optical systems typically employ intensity modulation and direct detection, which employ erbium doped fiber amplifiers for optical amplification. Eventhough a few works on binary polar code based optical systems are available in literature, all of them utilizes additive white Gaussian noise (AWGN) to model the channel noise. But this assumption is neither accurate nor realistic noise model here since the noise distribution is non-Gaussian. In this paper, the noise distribution of the optical channel is first mathematically derived and is proved that the chi-square distribution is more accurate. Non-binary polar codes provide same coding gain as that of binary polar codes, with shorter codeword length. This paper presents a non-binary polar code based short reach optical communication system with chi-square channel model. The successive cancellation list decoding for non-binary polar codes is used in order to reduce the latency and complexity in decoding. The error performance analysis of the non-binary polar codes with proposed channel model indicates that a coding gain of more than 1dB can be obtained compared to the AWGN channel model. Additionally, the performance enhancement of the non-binary polar codes over binary version is evaluated in terms of link distance.