Application Of Turbo Code And RS-Turbo Concatenated Code In Optical Orthogonal Frequency Division Multiplexing System

As a key technology for long-distance,high-speed,high-capacity optical communication transmission systems,Optical Orthogonal Frequency Division Multiplexing(OOFDM)has become the research focus.However,as the result of the existence of fiber nonlinear,high peak to average power ratio(PAPR)and the spontaneous emission noise of the optical amplifier(ASE),the BER performance of system is affected severely.So,in this paper OOFDM system is analyzed in theoretically and experimentally to improve the BER performance.The details are expressed as follows :1.The development and current research state of OOFDM technology and coding are introduced.2.The needed fundamental of this paper is introduced.Such as the theory of OFDM and coding and decoding theory of Turbo code and RS-Turbo code.3.A direct detection optical orthogonal frequency division multiplexing(DDO-OFDM)system using Turbo codes is built,and the transmission performance is analyzed between coded system and uncoded system.Three decoding algorithms,which are Log-MAP,Max-Log-MAP,Threshold Max-Log-MAP,are used in Turbo coded system.By comparing three decoding algorithms,Max-Log-MAP algorithm is obtained the best bit error rate(BER)performance.At the transmission distance of 240 km,uncoded system with transmission rate of 30Gb/s cannot get the BER performance of 10-3 degree within OSNR of 24 dB,while the Turbo coded system with transmission rate of 50Gb/s can achieve it with OSNR of 20 dB.4.The RS-Turbo concatenated code is applied to CO-OFDM system.RS(186,166,8)and Turbo code of code rate 1/2 is employed for RS-Turbo concatenated code.Two decoding algorithms,which are Max-Log-MAP algorithm and Log-MAP algorithm,are adopted for Turbo decoding and iteration BM algorithm is adopted for RS decoding.The simulation results show that the BER performance of CO-OFDM system with RS-Turbo concatenated code is significantly improved at high OSNR and the iteration number is reduced compared with Turbo coded system.Furthermore,when Max-Log-MAP algorithm is adopted for Turbo decoding,the transmission distance of CO-OFDM system with RS-Turbo concatenated code can reach about 400 km without error,while the transmission distance of Turbo coded system can only reach about 240 km when BER lower than 10-4 degree.5.A WDM transmission system using the CO-OFDM with PDM is builted,and Turbo code and RS-Turbo code are applied to the system,simulation results show that the system can transfer 200Gb/s data without error at OSNR of 22dB...