Research On Synchronization Technology In Real-time Optical IM/DD-OFDM System

The rapid development of Internet applications has led to a drastic increase in Internet Protocol(IP)traffic.To meet the growing demand for high-bandwidth services,existing networks need to be upgraded to support higher-speed network transmission.Orthogonal Frequency Division Multiplexing(OOFDM)technology will be widely used in the next generation of optical networks due to its scalable high-speed transmission and excellent dispersion resistance.Optical Intensity Modulation/Directe Detection OFDM(IM/DD-OFDM)system is a low-cost solution for high-speed short-distance optical communications and has been widely studied by domestic and overseas scholars.However,most of the research on optical IM/DD-OFDM systems is mostly offline or simulation studies,and does not consider the impact of hardware implementation complexity and synchronization problems in real-time transmission systems.In response to the problem,this paper focuses on the synchronization problem in the optical IM/DD-OFDM system.The main research and achievements of this paper are as follows:(1)From the aspects of symbol timing deviation and sampling clock deviation,the mathematical models are respectively established and the influences of the two deviations on the transmission performance of the system are simulated.Symbol timing offset can undermine the orthogonality between subcarriers in some cases,which can seriously affect the system transmission performance.Sampling clock offset causes phase rotation and amplitude fading of the data symbols and results in inter-subcarrier interference.(2)For symbol timing synchronization,three typical symbol timing synchronization algorithms are analyzed.A low complexity symbol timing synchronization algorithm based on a single training sequence is proposed.The simulation shows that the algorithm is easy to implement in hardware and has good noise immunity.(3)For the sampling clock synchronization,the pilot-based sampling clock offset estimation algorithm and two different compensation schemes are studied,and an easy-to-implement frequency offset estimation and frequency-domain compensation algorithm is proposed.Finally,the performance of this algorithm was verified on a real-time optical IM/DD-OFDM transmission platform.