The Research Of The Optical Orthogonal Frequency Division Multiplexing System Technique

Orthogonal frequency division multiplexing (OFDM) is a modulation technique which is now used in most new and emerging broadband wired and wireless communication systems because it is an effective solution to intersymbol interference caused by a dispersive channel. Leveraging recent advances in high-speed complementary metal-oxide semiconductor (CMOS) technologies and optical modulation and detection technologies, optical OFDM at a 40 Gb/s or even a 100 Gb/s information rate becomes feasible. In light of the emerging demand for a 100 Gb/s data rate in future optical transport systems, optical OFDM is considered to be a promising enabling technology.The paper focuses on the design and research of the optical orthogonal frequency division multiplexing system receiver, and includes several aspects as follows. This thesis introduced the general background information and domestic and overseas research status of Optical Orthogonal Frequency Division Multiplexing System.We accomplished the research into the principle and structure of the system, as well as some related techniques such as Cyclic Prefix, Interweaving, Synchronization estimation and compensation and Channel estimation. In addition, all three methods of channel estimation were simulated and compared to one another.Subsequently two forms of the system receiver were demonstrated in detail-the direct detection and coherent detection. As for coherent detection, we performed explicit analysis on its system theory, channel, and optical Up/down conversion design, moreover we conducted the simulation on the two-tone intermodulation analysis. The systems for direct detection and coherent detection were set up and then simulated through the software toolkit "optisystem". On that basis the two systems were compared to each other and given the performance analysis.This thesis presents a complete optical orthogonal frequency division multiplexing system, which is employed to achieve long distance transmission with high efficiency. We have constructed an experiment in which 4QAM light modulated OFDM signal with the code rate 10Gbit/s is transmitted 50 km away in the fiber, and the constellation diagram and error rate we have obtained through direct detection achieve good performance. The difference between two detection fashions that use avalanche photodiodes and traditional photodiodes (PIN) respectively is compared on that base, thereby the 5.2dB improvement of the sensitivity of the OFDM system receiver using APD for detection is discovered.Finally, a summary of the paper is given as well as the prospective of the research.