Research On Short-range Optical Discrete Multi-subcarrier Modulation System Based On High Order Modulation Scheme

In recent years,data center traffic has become the dominant traffic in the current communication network,and with the advent of 5G era,the global demand for data traffic has shown an explosive growth,which puts forward higher requirements for optical transmission network,the physical layer of the entire communication system.In particular,the development of data centers and the so-called "last mile" short distance access network communications service has put forward higher requirements.Different from the way of high capacity and high speed transmission which usually sacrifices system complexity in long-distance optical communication transmission,the short-distance transmission of optical interconnection in data centers needs to be considered from the perspectives of cost,power consumption and complexity,etc.At present,the method combining IM-DD technology and high order modulation format is adopted.In order to realize the high speed and large capacity transmission of optical interconnection transmission in data center,this paper mainly studies and learns from DMT and PS.The main work and innovation points are as follows:1.This paper introduces the principle and key technologies of DMT technology in detail,and compares DMT technology with OFDM technology.In addition,probability shaping technology can be used in optical communication to obtain high spectral efficiency and relatively high channel transmission capacity without increasing transmission power,which has a good development prospect.Therefore,this paper introduces the principle of probabilistic shaping technique and the reason of reducing bit error rate performance.And from the point of view of the advantages and disadvantages of the current constellation shaping method.2.A scheme of improving system performance by using discrete Fourier transform spread spectrum is proposed;The effect of DFT spread spectrum DMT transmission system on the performance of short-distance optical fiber communication in four different high-order orthogonal amplitude modulation formats is studied,and the experimental verification is carried out in the IM-DD communication system of 10 kmstandard single-mode optical fiber.In this scheme,the principle of reducing PAPR in DFT spread spectrum DMT system is firstly analyzed,and the experimental comparison of the tolerance of RPS and nonlinear effect in different order QAM formats is carried out.The results show that the improved DMT system can provide sufficient system loss budget for utilizing the existing optical access network.3.The academics are struggling to increase the channel capacity of the system is the direction,in order to solve this problem,some scholars put forward based on the "many-to-one " probability of LDPC coding mapping technology,can effectively improve the channel capacity of the system,but this algorithm only considers the distribution should follow Gaussian distribution,without considering the most big fellow hamming distance between constellation points distribution,thus to cause a decline in performance.We propose a new method of probability distribution based on the LDPC-based "many-to-one" probability mapping technique,which generates the corresponding 100Gbit/s signal and passes the 10 km standard single-mode optical fiber transmission experiment.Experimental results show that this method can not only improve the channel capacity of the system effectively,but also bring it closer to Shannon limit.And can effectively improve the system bit error rate performance.