| With the improvement of living standard and requirement of working, and the global introduction of portable terminal devices and new cloud paradigms for storage and computing, more and more people demanding one-stop multi-services wireless access network. Coupled with network users and network traffic surge, forcing operators to further improve the network transmission speed, look for a new frequency to broaden the channel bandwidth. Optical fiber communication has the advantages of high bandwidth, low signal power consumption, resistance to electromagnetic interference, as a foundation for the future network development. Meanwhile, orthogonal frequency division multiplexing (OFDM) technique can well combine with optical access network, because of its advantages of being against multipath fading and dispersion, flexible modulation, high spectral efficiency that provide more support for realizing fiber access network. How to combine optical fiber and wireless communication technology, use high frequency radio frequency signal with the existing fiber optic lines based on OFDM and High frequency wireless signal interference suppression technology is a research direction of high speed multi-services wireless access network in the future of the telecommunication industry.This thesis focus on combining orthogonal frequency division multiplexing technique and radio over fiber technique. The aim is to design a high speed access network system for multi-service. In the process, I analyzed the high frequency wireless signals in optical fiber transmission by dispersion and nonlinear effect and found the solution to restrain dispersion and nonlinear effect. A novel optical carrier modulation technology is proposed, which is similar to the single side band and optical carrier suppression modulation. At the same time, pilot frequency and phase correction technique are used in this system. All this restrains the interference between the high frequency signals. And it reuses downlink signal overload technique to reduce the cost and complexity of the system. The main works are as the following:1) For OFDM modulation technique, making theoretical analysis based on the mathematical model and understanding the basic principle of its structure and modulation signal demodulation. Designing a suitable program which support OFDM signal flow for radio over fiber (ROF) and do preparation for link simulation.2) ROF system comprehensive analysis in the different carrier modulation techniques and the carrier reusing technology. To design a suitable ROF link structure for OFDM signal transmission. I proposed a similar to the single sideband suppressed carrier modulation technology and effectively inhibit the signal power fluctuate along with the increase of transmission distance. And on this basis, proposed a full-duplex ROF wireless access network system which achieve the downlink rate10Gb/s and the uplink rate of2.5Gb/s.3) Designed an OFDM-ROF system which is suitable for the two different signal transmission. Making a optical carrier signal loaded two different data signals. I analyzed the reasons why the two high frequency signals interference each other and through the inserted pilot frequency, phase correction technique to suppress the influence of high frequency signal interference. Finally, an dual duplex OFDM-ROF wireless access network system is realized which can achieve the downlink of2.5Gb/s,1.25Gb/s and uplink1.25Gb/s,1.25Gb/s by only one optical carrier. |
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