Research On The Key Technologies Of High-Speed Optical Transmission System Based On OFDM Technology

With the rapid development of data service and video traffic, the demand of large transmission bandwidth increases rapidly with the amazing speed.In order to meet the demands of network bandwidth and the highly continuous growth of single channel rate, high-speed optical communication systems are abandoning the conventional Intensity-Modulation/Direct-Detection(IM/DD) scheme.Applying the mature OFDM technology of wireless communication into the optical field which can be used to realize the high-speed optical transmission has become one of research focus.Optical OFDM system, which has the advantages of high transmission rate, high spectrum efficiency, high immunity to chromatic dispersion and lower cost, combines the advantages of wireless OFDM technology and optical communications.The optical OFDM system is able to construct the optical networks with high-speed, lower-cost and long-distance transmission.Furthermore, the optical OFDM system has been considered to be one of potential technologies for next generation high-speed and long-distance transmission optical networks.This paper illustrates the related fundamental theories and systemic concepts of Optical OFDM system. Then, the performance and some key technologies of optical OFDM were deeply investigated by constructing the simulation platforms. Some major research contents and achievements are summarized as follow:(1)First, the principle and key technologies of OFDM technique are well researched.Then, starting from the formula derivation, the fundamental theories,advantages and disadvantages of the optical OFDM system, especially the Direct-Detection OFDM (DD-OFDM)and Coherent-Optical OFDM (CO-OFDM) are deeply analyzed.(2)The DD-OFDM simulation platform is constructed by using the VPI and Matlab simulation tools.Researches show that DD-OFDM system has high immunity to chromatic dispersion,when the on-line dispersion compensation is not introduced.(3)A novel DD-OFDM optical single-sideband (OSSB) modulation scheme is proposed, which is based on traditional OSSB modulation theory and composed of two parallel dual-drive MZMs.(4) The CO-OFDM simulation platform is constructed by using the VPI and Matlab simulation tools.The platform is verified by comparing the simulation Q-factors with the theoretical values.(5) Based on the constructed CO-OFDM simulation platform, carrier frequency offset (CFO) compensation algorithm and phase noise (PHN) compensation algorithm are investigated. The frequency offset compensation algorithm combines of decimal part CFO and integral part CFO compensation algorithm. The PHN compensation algorithm utilizes the comb-type pilot method.Researches show that these algorithms can effectively resist the systemic degradation which is induced by the linewidth and frequency offset of lasers.