Based On The Research And Design Of Key Technologies Such As Constellation Shaping In Optical Fiber Communication System

Since the 21st century,emerging Internet technologies such as big data,cloud computing,Internet of Things,augmented reality and virtual reality have developed vigorously.Various Internet services have emerged in an endless stream,which result in a spurt of network data traffic and the ever-increasing demand for large-bandwidth digital services from end users and mobile communication networks.The optical fiber communication system,as the backbone of the Internet,carries most of the network data traffic.Therefore,how to achieve greater capacity,better system performance,higher information rate,longer transmission distance,lower system power consumption,and more flexible modulation methods in optical fiber communication systems has become a research topic widely studied today.The constellation shaping technology,as an enabling technology that can enhance system capacity,improve system performance,extend transmission distance,and reduce transmit power,is at the right time and has become a research hotspot at home and abroad.This thesis has carried out in-depth research on constellation shaping technology.Starting from the basic principles and implementation foundation of constellation shaping technology,this thesis focuses on key technologies based on the generation and construction of constellation shaping signals,constellation optimization and modulation,and has verified the advantages and potential of constellation shaping.In view of the limitations of the current probability distribution matching methods,some new probability distribution matching methodes are proposed to reduce the system power consumption and improve the system error performance.The main research contents and innovations of this article are as follows:(1).Based on the study of the Constant Composition Distribution Match(CCDM),a parallelized bit-level probabilistic shaping optimization scheme based on CCDM is proposed.Allows the transmission data to be input to the bit-level probability distribution matcher in parallel to improve the system throughput and data processing rate.For each bit tributary whose half of the parallel input bit tributaries are at the high bit level,a CCDM is used for bit-level probability distribution matching independently,thereby reducing the requirements of the CCDM for the length of the shaping block and the memory space,thereby reducing delay and saving costs.A simulation platform was built to verify the feasibility and performance advantages of the new probability distribution matcher.Simulation results show that compared with the uniform distribution scheme,the PS scheme has better error performance,larger transmission capacity and longer transmission distance.In this simulation,when the bit error rate is 3.8×10-3,the new probabilistic shaping scheme improves the receiver sensitivity by 2.4 dB.After 400 km of optical fiber transmission,the bit error rates of probability distributed signal and uniform distributed signal are 6.2×10-3 and 0.0205,respectively.The system error performance is significantly improved after probability shaping..(2).An even-order modulation scheme based on bit-spreading probability shaping and constellation optimization is proposed.Compared with the traditional probabilistic amplitude shaping coded modulation scheme is only applicable to the square orthogonal amplitude modulation format,this paper proposed a new scheme with the method of bit extension to change the number of code words corresponding to different symbols,to generate an even number of class symbols with a target distribution,thus,the universality of probabilistic shaping to different modulation formats is improved.According to the number of types of code words obtained after the shaping,the structure of 10-points constellation,12-points constellation and 30-points constellation with excellent constellation performance index was designed accordingly.Compared with the square 2-D constellation structure,the structure of 10-points constellation,12-points constellation and 30-points constellation has more dense constellation point arrangement and lower average power of constellation.Simulation results show that when the bit error rate is 1×10-3,the SNR tolerance of PS-star-10QAM is increased by 1.32dB.The BER of 30QAM signal with probability distribution and honeycomb constellation structure and uniform distribution signal are 0.0023 and 0.0082,respectively.(3).Researched and proposed a joint probability shaping and geometric shaping 44QAM coded modulation scheme.Firstly,the probability distribution of 44QAM symbols is matched by Hoffman coding.Then,based on the square 64QAM constellation diagram,a truncated 44QAM constellation structure with lower average constellation power and peak to average ratio was designed,and PS-44QAM signals were generated after mapping with the new constellation.Finally,the Pair Optimization Algorithm is applied to optimize the constellation coordinates of PS-44QAM signal,and finally the joint probability and geometric shaping 44QAM signal(G/PS-44QAM)is obtained.Simulation results show that the combination of probabilistic shaping and geometric shaping can obtain better error performance.At BER=1×10-2,G/PS-44QAM improved the SNRtolerance of 2.2dB and 3.3dB compared with UNIFORM 32QAM and UNIFORM 44QAM,respectively.Simulation shows that the G/PS-44QAM can improve the system performance on the basis of PS-44QAM by geometric shaping,and has lower bit error rate and higher mutual information than PS-44QAM under the condition of low SNR.In the case of high signal-to-noise ratio(SNR),geometric shaping almost provides no shaping gain.