Voice Transmission System Based On Free Space Optical Communication

The basic principles of free space optical communication technique is analyzed in this dissertation, and the study on the pivotal problem existing in the technique--effects of free space attenuation is laid emphasis on, the transmission of voice signals under different climates also is preliminarily explored.Firstly, the simulation model of free space optical communication system is established. The atmospheric attenuation influenced on bit error rate of the system under clear, rainy, snowy weather conditions is discussed respectively, and the difference in system performance for three weather conditions is investigated directly through eye diagrams. The laser power and transmission distance influenced on bit error rate of the system is considered. The results show that the transmission distance does not only depend on laser power. The relation of maximum distance and attenuation coefficient is given.Secondly, on the basis of experimental simulation, the design scheme of the transmitter and receiver is given in this thesis. Every part and their design principle of free space optical communication system are investigated in detail. The research on the module of preamplifier, A/D voice input, D/A voice output, and controlling of the system is laid stress on.Finally, various atmospheric channels are simulated, the theoretical test of influences of atmospheric attenuation and practical voice communication experiment are conducted by the model machine of phonetic transmission system studied, and the results are analyzed.The simulation and the experimental results show that transmitting voice data under common weather conditions (except heavy rain and snow) could be realized.