Application Of Polar Codes In Optical Communication Systems

Driven by high-traffic services such as the Internet,big data,and cloud computing,the optical communication system has become a research hotspot in the communication field with its advantages of high speed,large capacity,and low loss.Since the polar.code was proposed in 2009,it has become a new star in the coding field due to its low complexity of coding and decoding,and "reachable" channel capacity.In this paper,the structure of the polar code and the coding and decoding algorithm are first implemented.Then,the polar code is simulated and analyzed experimentally in a non-coherent optical communication system.Finally,the performance of the polar code is studied in a coherent optical communication system.Compare with LDPC.The specific work of the paper is summarized as follows:(1)The implementation of Polar Code Information Bit Selection,Encoding and Decoding Algorithms and Simulation Performance AnalysisAfter summarizing and classifying three commonly used information bit selection methods for polar code,this paper chooses Gaussian approximation,which is more suitable for optical channels,as the research object,and simulates information bit selection with arbitrary code length.In terms of decoding,this paper analyzes and implements the classic successive cancellation decoding algorithm(SC)and an improved list cancellation decoding algorithm with cyclic redundancy check(CA-SCL).Finally,under the white noise(AWGN)channel,the effects of code length,code rate,and search algorithm L of the decoding algorithm on the performance of polar code are analyzed.(2)High performance transmission of 28-GBaud polar code aidedPAM system based on 10-GHz Direct modulation laser(DML)Applying low-complexity polar code to low-cost optical communication PAM systems can significantly increase the optical link budget of the system.The paper first introduces the simulation platform of a non-coherent PAM system,and explains the principle of PAM modulation,soft demodulation of PAM signals,and the puncture-polar code to implement polar-PAM8,and complete it.Then,the performance of the PAM2,PAM4,and PAM8 systems using the polar code is simulated and analyzed.The results show that the optical budget of the system has been improved by 8dB,7dB,and 9.6dB with the polar code.Finally,based on a 10-GHz direct modulation laser,at the rate of 28-GBaud,this paper firstly studied the improvement of PAM4 and PAM8 systems by polar code.The experimental results show that by using the polar code decoding algorithm of SCL=4,the optical link budget of the PAM4 system at back-to-back and 10-km is increased to 31.8dB and 30.9dB,respectively,which is improved compared with the case without polar code 10dB and 11.7dB.Polar code assisted PAM8 overcomes the problem that the 10-km system of 28-GBaud PAM8 cannot be transmitted due to error leveling.Using the decoding algorithm of SCL=4,its back-to-back and 10-km optical link budgets are increased to:25.8 dB and 23.7dB.(3)Performance Study of Polar Code and LDPC for m-PSK,m-PPM and mPPM-QPSK Modulation SystemIn the application scenarios of coherent optical communication systems with limited delay,the performance of polar codes and LDPC with low complexity and short codes is studied.This paper builds the MATLAB simulation platform of the coherent optical communication system,and then in the QPSK system,the code length of the short code is 256,512,1024,2048 and the number of decoding iterations(decoding list width)on the polar code and LDPC conducting research,the results show that polar code has better performance than LDPC in short codes and low search width.In QPSK,8PSK,and 16QAM systems,with 20%overhead,1024 code lengths of polar code coding gain are better than LDPC:1dB,1.1dB,0.6dB.Then this article applies polar code and LDPC to 2PPM,4PPM,and 8PPM systems.Since high-order modulation will destroy the polarization characteristics of the polar code,this article uses a random interleaver to improve it before modulation.The results show that in the three systems,the coding gain of polar code is better than LDPC:1.1 dB,0.4dB,0.7dB.Finally,the performance of polar code and LDPC is studied in mPPM-QPSK.The results show that the sensitivity of polar code in the mPPM-QPSK system is still higher than that of LDPC:0.93dB,0.43dB,0.67dB.Limited by the post-correction performance of PPM in the mixed modulation format,the sensitivity of 2PPM-QPSK and 4PPM-QPSK is lower than the polar-QPSK system,and the sensitivity of 8PPM-QPSK is higher than polar-QPSK system,reached 1.07dB.