Full-duplex Optical Carrier Wireless Transmission System Research

With the development of social information technologies, the demands formultimedia broadband service are increasing, but the congestion of wirelesscommunication at microwave frequencies has been unable to meet the variousneeds of the services. ROF (Radio-Over-Fiber) system was born, as a combinationtechnology of wireless communication and optical fiber communication. It takes themobility advantage of wireless technology to replace the cable restriction of opticalfiber communication. At the same time, it can transmit the high loss wireless signalvia optical fiber with large capacity. Thus, ROF systems have much potential practicalapplication.Recently, with the increasing requirements for access bandwidth of wirelesslocal area network and the fourth generation mobile communication system, and thereducing cost of optical modulators and transceivers, ROF systems using millimeterwave as carrier to transmit2.5Gb/s signal will play an important role in the futurecommunication. In this paper, we mainly study the ROF systems based on differentschemes of modulations and the corresponding transmission performances. In thisthesis, three crucial ROF technologies are investigated, the generation andtransmission technology of optical millimeter wave, base station simplifiedtechnology and multi-frequency doubling technology. The main contributions of thisthesis are as followings:Firstly, for the transmission technology of optical millimeter wave, wecomparatively study two simplex ROF systems based on phase modulation orintensity modulation to respectively transmit the2.5Gb/s downlink signal. Weanalyze the eye diagram performances. The results show that in order to suppressoptical carrier signal, the intensity modulation scheme with Q value of153, has abetter performance than phase modulation scheme with Q value of78.Secondly, for the simplified technical scheme of base station, we study anddemonstrate a duplex20GHz-ROF system based on optical carrier suppression totransmit the2.5Gb/s uplink and downlink signal. Compared with the simplex ROF system, the result shows that when BER is10-9, the received power of downlinksignal has decreased by0.3dB, and the Q value is74. The duplex ROF system canavoid the periodic fading of receiving current, and improve the dispersion capability.Finally, for the multiple frequency doubling technology, we proposed and study3ROF systems, simplex40GHz-ROF system based on four frequency doublingtechnology, simplex and duplex60GHz-ROF system based on six frequency doublingtechnology. We use10GHz RF signal and the two phase modulator to generate the60GHz optical millimeter wave signal, and transmit the2.5Gb/s uplink and downlinksignal. Compared with former duplex system, when BER is10-9, the received powerof downlink signal has decreased by0.5dB, and the Q value of downlink and uplinkare161and72, respectively.