Research On Auto-tracking System In Optical Wireless Communication

Optical wireless communication, which is also called free space optical communication, has the advantages of large capacity, anti-electronmagetic and good security. Nowadays, more and more people pay attention to it in the information age. The tracking technology is the critical part as well as technical difficulty in optical wireless communication system.In this paper, the advantages and the application prospect of optical wireless communication are analyzed, and then the current situation of the domestic is introduced. Although the system performance of inter satellite is good, the tracking technology cost is high which is not conducive to the popularization and application. According that the performance of the system requirements on the ground-based optical wireless communication on is not high and it’s sensitive to the cost, optical antenna is analyzed and, and designed, the technical requirements of tracking system is put forward. An auto-tracking system for ground-based optical wireless communication is designed based on the two dimensional(2D) galvanometer with a good linear, simple control, low cost. The four quadrant detector(QD) is used as the detector, and the two dimensional galvanometer is used to replace the traditional piezoelectric ceramic(PZT) and the fast steering mirror(FSM) to realize the optical path tracking. Two schemes are designed based on STC89C52 and FPGA respectively for micro control unit(MCU). The main research work of this paper is as follows:Firstly, the optical antenna of ground-based optical wireless communication is designed. The transmitting antenna adopted the Galileo transmission to reduce the antenna size with the divergence angle of 1mrad.While the receiving antenna adopted the Kepler transmission and the receive aperture is 100 mm. The tracking accuracy should be better than 142 μrad to meet the design of optical antenna in communication.Secondly, experiments are carried out to test the automatic tracking system which used the STC89C52 as the MCU, the design principle of the system is verified to be right. The results indicate that the system linearity is better than 0.017, the tracking accuracy of it can reach 0.53 mrad and the response frequency range is 200 Hz, and the optical jitter can be completely suppressed when the jitter frequency is below 100 Hz.While the improved system has better performance, the system linearity of it is better than 0.013, the tracking accuracy of it can reach 83.3μrad and the response frequency range is 1000 Hz.The optical jitter can be completely suppressed keep stable when the jitter frequency is below 300 Hz.The experimental results show that the auto-tracking system designed in this paper can meet the requirements in ground-based optical wireless communication...