Real-time Control System For Laser Power In Atmospheric Laser Communication

Atmospheric laser communication is one of the wireless optical communication methods with many technical advantages and great potential. It combines the strengths of wired and wireless communication which contain high speed, large capacity, wide bandwidth, low cost, convenience and flexibility. In spite of all the merits of atmospheric laser communication, it still has a critical problem to be solved for the atmospheric channel which it travels in is unsteady. Characteristics of the air channel change randomly, and the attenuation degree of the channel varies as the weather conditions change. In order to reduce the influence of the random variation of the atmospheric channel on the communication process, a communication system is introduced in this paper to adjust the power of the transmitted light in real time with the change of atmospheric environment.Based on the study of the air channel and auto-control algorithms and optical transceivers in free space optical communication system, a solution is proposed in this paper in which the laser power of the optical wireless communication system can adjust to the weather in real time. The main contents include the following:(1) This paper describes the characteristics and applications of atmospheric laser communication, discusses the significance of the real-time control of laser transmitting power, and introduces the research progress of the domestic and foreign research on the realtime control of laser power.(2) According to the characteristics and requirements of wireless optical communication system, a scheme of controlling the transmission power of the system by programmable optical attenuator is determined. The control method of the scheme is described, and the scheme is compared with that of the direct regulation of the laser drive current.(3) The effects of atmospheric channel on the transmission of optical signal are analyzed. Calculation and measurement of the optical transmission in the process of other loss are made. The control circuit schematic diagram and device parameters are provided and are used as the basis for determining the system model, and the system output feedback results are corrected using the PID algorithm.(4) The simulation test and experiment test is carried out on the system with real visibility data, and the results show that the system can meet the requirements of the real-time adjustment of the transmit power by using real-time monitor and PID.