The Research On Combining Algorithms To Reduce PAPR In Optical OFDM Systems

With the increasing demand for fast and high quality network,optical fiber communication plays an important role,and modem plays a key role in the process of information transmission.Orthogonal Frequency Division Multiplexing（OFDM）system has been widely used because of its superior characteristics,and its application in optical communication has made great progress in recent years.However,in OFDM,the peak-to-average power ratio（PAPR）problem caused by the system itself causes the system performance to decline.How to reduce PAPR has always been a hot issue.Similarly,because of the linear relationship of optical communication,it will lead to higher PAPR value.For how to reduce PAPR,scholars have studied and presented three classical algorithms:limiting technology,probability class technology and coding technology.Among these methods,the former proposed companding algorithm is to improve the probability class algorithm;the proposed SI-PTS algorithm is to improve the PTS algorithm and the proposed FRFT algorithm uses different transformation angles to reduce PAPR.In order to solve the problem of high PAPR,this paper proposes two ways to reduce the impact of PAPR on the system based on previous studies.Specific contents include:（1）Firstly,we propose to improve the SLM algorithm and generate GE-SLM algorithm by grouping signals.The algorithm can effectively reduce the PAPR value.The combination of the two algorithms can not only effectively reduce PAPR and BER,but also significantly reduce the computational complexity of the system.The feasibility of the proposed algorithm is verified by simulating the direct detection of optical orthogonal frequency division multiplexing channels.（2）Secondly,the application of pilot signal in reducing PAPR in OFDM intensity modulated optical wireless communication system is proposed.The phase selection of pilot signal is based on the selected mapping（SLM）algorithm,and the maximum likelihood criterion is used to estimate the pilot signal at the receiver.In reliable communication links with BER less than10^-3,the bit error rate（BER）of Pilot-Assisted optical OFDM system is basically the same as that of traditional optical OFDM system.Under the condition of high-order（M>4）constellation,Pilot-Assisted PAPR reduction technology has better performance than traditional SLM technology.Compared with basic optical OFDM,Pilot-Assisted optical OFDM system can reduce PAPR by about 2.5dB under L=4,R=10 conditions,and Pilot-Assisted optical OFDM system can reduce PAPR more effectively at the appropriate point of M=64 and CCDF=10^-4without reducing the error performance of the system.By improving and combining the algorithm,we can reduce the PAPR in optical OFDM system,so as to solve the problems of system cost increase,amplifier efficiency reduction and amplifier efficiency reduction caused by high PAPR.