Multiple LDPC Code And Its Application In Optical Fiber Communication

The Low Density Parity Check(LDPC)code is the channel code that most approximates the Shannon limit proposed by Professor Robert Gallager of MIT in 1962.Error decoding,so this encoding is suitable for almost all channels,so the LDPC code has become a research hotspot in the coding and decoding world in recent years.Fiber-optic communication uses light and fiber to transmit information.It is a type of wired communication.After light is modulated,it can carry information.From the beginning,it has shown great advantages.Good performance makes binary LDPC codes widely used in optical fiber communication.However,under the same parameters,multi-element LDPC codes have better error correction capability,stronger burst resistance,and more stable code performance.Therefore,multiple LDPC codes are more suitable for optical fiber communication.This article focuses on the following aspects:1.Introduce the basic principles of optical fiber communication systems,channel coding and decoding theory,and basic knowledge of LDPC codes,and discuss in detail the representation methods,check matrix construction methods,and encoding methods of multivariate LDPC codes.2.Investigate five common decoding methods for multivariate LDPC codes.The first is the BP decoding algorithm in the probability domain;the second is the BP decoding algorithm in the log domain;the third is the minimum sum decoding algorithm;the fourth is the normalized minimum sum decoding algorithm;the fifth is the offset minimum sum decoding algorithm.At the same time,this paper compares these five algorithms in terms of performance and the amount of decoding operations.Based on the logarithmic domain BP decoding algorithm,this paper simplifies the field word operation,and proposes a logarithmic domain BP decoding algorithm based on Taylor series piecewise approximation,which greatly improves the original decoding algorithm's performance.Reduce the amount of computation and analyze its performance through Matlab.3.Investigate the effect of multiple LDPC codes on optical fiber communications under ultra-high-speed and large-capacity situations.Combine multiple LDPC codes with several digital modulation methods to find a balance between the amount of calculation and the bit error rate,so as to meet the actual operation requirements.Finally,FPGA is used to implement the improved algorithm in hardware,and each module is verified through simulation waveforms,which proves the correctness and feasibility of the improved algorithm in this paper.4.Summarize the research content of this article,point out the deficiencies and future research directions.