| Polar code is the first coding scheme to reach the Shannon limit in theory.It has a regular coding architecture and low complexity coding and decoding calculation.At present,polar codes are mostly used in wireless communication system scenarios,while there is relatively little research in the field of optical communication applications.At the same time,because coherent optical communication technology and mode division multiplexing technology are becoming the research and development hotspot of optical communication technology,polar code will also be introduced into the mode division multiplexing system.Therefore,the potential of polar code in the field of optical fiber communication needs to be further studied.This paper mainly studies the application of polar coded modulation in optical communication system,which can be summarized into the following three parts.(1)The design of a polarization interleaver in polarization multiplexed optical communication systemThe polarization interleaver in this dissertation uses the same encoder to polarize the information bits of the system,and then interleaves the sequence after polar coding,which breaks the correlation between the multi bit bits contained in the symbol bits after highorder modulation,reduces its impact on the polarization of the polar code channel,and improves the performance of the communication system.At the same time,2D and 4D modulation and coding schemes are compared and analyzed,and the scaling factor is introduced in the calculation of decoding symbol measurement.When the scaling factor is 0.5 and 1.7 respectively,the performance of the system is improved.(2)Performance study of bit-interleaved polar code modulation in mode division multiplexing systemIn this dissertation,polar coded modulation and mode division multiplexing system are combined to build a mode division multiplexing system based on bit interleaved polar coded modulation,and the experimental simulation of the decoding performance of the system is carried out.Compared with the non-coding mode division multiplexing system,the system performance of the polar coding modulation mode division multiplexing system has been improved by 8d B.At the same time,the decoding performance of ML detection algorithm and MMSE detection algorithm in the system is analyzed.When the number of modes is 2 and 4 respectively,compared with the decoding performance of MMSE detection algorithm,the system performance after using ML detection algorithm is improved by 5d B and 2.5d B respectively.Finally,the influence of different mode dependent loss on system performance is studied.With the increase of mode loss,the degree of system performance decline increases.(3)Performance study of suboptimal detection algorithm in mode division multiplexing system.Aiming at the high complexity of ML detection algorithm,this paper improves it by suboptimal detection algorithm CR-QRM-MLD.The order of symbols to be detected is determined by channel sorting,and the computational complexity of the detection algorithm is reduced by decomposing the channel matrix by QR matrix,simplifying the calculation process and reducing candidate transmission vectors.Compared with ML detection algorithm,the decoding performance of suboptimal detection algorithm is reduced to a certain extent,but the complexity is greatly reduced. |
