Research On The Performance Optimization In Radio Over Fiber System Based On OFDM Signal

With the rapid development of communication technology, people are more urgentto long distance, high-speed communication network and high quality communicationservices. Radio-over-fiber (RoF) technology has gained lots of attention recently dueto its ability to combine mobility in wireless communication and high capacity inoptical communication. Meanwhile orthogonal frequency division multiplexing(OFDM) becomes the key technology for the next-generation high speedcommunication network. OFDM technology has many characteristics, such as highefficiency, tolerance to fiber dispersion and polarization mode dispersion. The systemwhich seamlessly combines the RoF and OFDM technology gradually becomes thedeveloping tend of the high-speed communication in the future. But how to optimizethe performance of the OFDM-RoF system needs to be studied deeply. This thesis hasresearched the modulation of the OFDM signals and used training sequence technologyto reduce the signal-signal beating interference (SSBI) in optical OFDM system. Wehave done following researches.Firstly, we research the single sideband OFDM signals in60GHz OFDM-RoFsystem, and the signals are generated based on three different modulation methods. Wecompare the performance of the received OFDM signals between three systems.Thenwe obtain a modulation technology, with which the configuration of the optical OFDMsystem is simple, and the performance of the system is better. The simulation resultsshow that it can generate double frequency millimeter wave. It also reduces thebandwidth of optical devices and the cost of system. When the opticalcarrier-to-sideband ratio (CSR) of the optical signal is15dB, the2.5Gbit/s OFDMsignals which transmit120km standard single mode fiber can be completely recovered.Secondly, we research the SSBI in direct-detected OOFDM system when theOFDM signals are detected by photoelectric detector. We propose OFDM signals withinterleaved training sequence configuration to reduce the SSBI. The experimentalresults show that the power penalty of the2.5Gbit/s interleaved OFDM signals is1.4dB at the BER of103, and it is better than that of the continued OFDM signalsafter the signals transmitting over100km standard single mode fiber with nocompensate. The error vector magnitude (EVM) and performance of system are betterthan that of the continued OFDM signals in robust tolerance against SSBI. Lastly, we analyze the influence of SSBI in60GHz OFDM-RoF system. Wepropose an OFDM signal with interleaved training sequence configuration to reducethe SSBI influence. The experimental results show that after the2.5Gbit/s interleavedOFDM signals transmitting over20km standard single mode fiber in58GHzOFDM-RoF system, the power penalty of the OFDM signals is only0.5dB at the BERof103. While the power penalty of the continued OFDM signal is2dB. Itdemonstrates that the transmission performance of the interleaved OFDM signal isbetter than that of the continued OFDM signal.