Research On The Theory And Application Of Polar Code In Coherent Optical Communication System

With the continuous development of 6G and new infrastructure,the demand for transmission capacity and communication rate of optical communication network is also growing exponentially,and the requirements for optical signal-to-noise ratio,dispersion and fiber nonlinearity are becoming more and more strict.In order to reduce the impact of the above factors on high-speed optical fiber communication,the introduction of forward error correction coding in optical fiber communication is one of the most effective methods.Polar code is a new coding method,which is the first coding method that can obtain channel capacity in information theory and does not have error floor.It has become a research hotspot in the field of error correction code,and also provides a new idea for the next generation of optical communication forward error correction coding technology.This paper mainly studies the performance of modulation schemes based on polar code in coherent optical communication systems.The following are the research emphasis and innovations of this paper :(1)The principle of polar coding and decoding and three construction methods of polar code are introduced,and a DP-16 QAM coherent optical communication system based on polar code is built.The performance of the three construction methods under different design signal-to-noise ratios is comparative analyzed.The simulation results show that the performance of different construction methods is different under different design SNRs,and the performance of Monte Carlo construction is the best under about-1.5d B design SNR.(2)This paper studies the coding and modulation technology in general field,and expounds the problem of bit imbalance in the polar coding and modulation system based on traditional BICM.A multi-level coding and modulation method is proposed for DP-16 QAM coherent optical communication system.Two MLC encoders are used to encode the four binary channels of DP-16 QAM jointly,and the bit rate is adjusted according to the reliability of the binary channel to solve the bit imbalance problem with low hardware complexity.(3)For the first time,an optical communication system based on polarization interleaver is proposed.The polarization recursive structure of polar code is used to encode and modulate the two polarization channels of polarization multiplexing optical communication system.Only one encoder is used to encode the multiple binary channels of DP-16 QAM.At the same time,a deinterleaving method based on four-dimensional demodulation is used to jointly demodulate the variables of two polarization amplitudes and two phases,which improves the spectrum utilization rate.And the BER performance of the traditional BICM,two-dimensional polarization interleaving,four-dimensional polarization interleaving under different OSNRs and PMDs is compared to verify the effectiveness of the proposed scheme.