Research On Key Technology Of Fiber-to-wireless Transparant Access Based On Optically Controlled Microwave Switch

With the deepening of information society, communication exists everywhere. Wireless access technology becomes a common way of communication thanks to its high flexibility and customized characteristic. However, the microwave signal has a great loss in the process of long distance transmission, especially in the high frequency band, and the loss is more and more obvious. Therefore, microwave is not suitable for long distance communication application. Optical fiber communication has the characteristics of high speed, and low loss. Thus, the hybrid fiber- wireless access technology which lets signals be transmitted through an optical fiber to a close distance mobile terminal user launch system, and then the signal is sent to user by means of the antenna with wireless method is a very good choice.In order to overcome the disadvantages of existing optical fiber wireless access system, based on Optically Controlled Microwave Switch(Optically Controlled Microwave Switch, OCMS) technology and Directly Antenna Modulation(DAM) principle, this thesis put forward a kind of wireless access technology which is able to make optical fiber "transparent". Without the optical modulation, regeneration of the RF signal, and the recovery of baseband digital signal, regeneration and radio frequency modulation, the optical output terminal is directly connected with the antenna system. By introducing an OCMS in the antenna structure, the optical signal directly controls switch on and off in order to achieve the antenna radiation signal on-off modulation, so that it can realize optical signals to the "transparency" of the radio signal transmission. Compared to traditional optical and wireless access technology, this method avoids the baseband signal recovery, regeneration and frequency conversion process, thus greatly reduces the volume of a communication system as well as the complexity. The main content of this thesis are as follows:First, the background, significance and state of the art about the fiber-wireless access system are introduced. Then the communication principle of Directly Antenna Modulation technology is summarized.Second, optically controlled microwave switch is analyzed in detail on the working principle, performance parameters and its influencing factors. A kind of fiber-wireless access antenna design is given based on optically controlled microwave switch in combination with direct modulation technology. The working principle, design process of the antenna is discussed in detail. Simulation results of the influence of switch on the antenna parameters are compared with measurements, and an antenna transceiver signal construction of the experimental test platform is built.After that, aiming at the shortage of the fiber-wireless antenna structure design in the third chapter, an improvement of the antenna structure is proposed and the influence of switches on the antenna parameters is analyzed by simulation.Finally, the work of this thesis is summarized and the development direction of this research is prospected.