Research On The Signal Tracking Technology Of Optical Wireless Communication

In the decade of information, with the increment of the data rate and capacity in communication, optical wireless communication (FSO) has been paid much attention by many countries since it integrates the advantages of fiber communication and other traditional wireless communication technologies, such as large capacity, low cost, convenient deployment and flexibility. It has been developed rapidly in recent years.This thesis concerns with the research on the signal tracking technology of FSO. The main parts of the thesis are as follows:(1) Based on the widely learning of relative references, the character and applications of FSO are reviewed in the first chapter, and the state of the art is introduced in brief.(2) The effect of atmospheric turbulence and vibration of the FSO platform on signal tracking system is discussed. And the system BER is analyzed, which is influenced by the laser transmitting power, atmospheric turbulence, vibration and the link range.(3) Considering that suppressing vibration is a difficulty of FSO, so suppressing methods are discussed in the paper. As a base, the ATP (Acquisition, Tracking, Pointing) technology of satellite laser communication system is analyzed in this paper. And a new signal tracking system for ground-based optical wireless communication is described. The main structure, integral parts and detailed work process of this signal tracking system are introduced in detail. (4) Some new methods about of error signal analysis and processing are presented, the selecting principal of spot size is given. Considering the spot intensity of laser beam is related to the formation of error signals, a new method of error signal processing is designed. This method can speed up the pointing of the signal tracking system.(5) A detecting circuit for error signal is presented. This detecting circuit has performance of broad band, high speed, and provides high reliability for the signal tracking system. Based on digital signal processor, the control module for the signal tracking system is designed. In the design, the emphasis is the function and the working process of A/D conversion and DSP control. At the same time, the corresponding circuit structure charts are given. The capability and structure of the main components are illuminated.In addition, this paper gives the simulation software frame of the signal tracking system on the basis of the reasonable disassemble of tracking function, and the flow chart of some important software, such as PID control.