Research On Atmosphere Channel Of Wireless Optical Communication System

Due to the intense requirement for improving the transmission speed of wireless communication and the increasing shortage of spectral bandwidth, we no longer satisfy with traditional microwave communication and call for a new mode of wireless communication. Wireless optical communication technology integrates the advantages of microwave communication and optical communication, has the merits of high bandwidth, fine secrecy and low power, utilizes light wave with frequency of hundreds of terahertz to transmit and have a bright future because of its high transmission speed which could reach 10Gb/s and no requirement for traditional spectral bandwidth resource. Nevertheless, wireless optical communication technology still has many problems which limit its development, the primary one of which is the influence of atmosphere channel on wireless laser communication.Firstly, this paper analyze two effect that atmosphere exerts on optical communication. The one is atmosphere attenuation effect which sharply reduces the power of optical signal when the transmission distance increases; the other one is the atmospheric turbulence effect which produces optical intense fluctuation and influences correctly receiving signal. Moreover, this paper introduces several atmosphere channel models proposed by scholars in the world and specially analyzes the logarithm normal distribution model which has been widely used currently. Finally, under different atmosphere channel, we have researched the bit error probability of single and multiple beam transmission system and simulated the transmission on the computer in which the decision criterion is the max likelihood radio decision criterion and the merging mode of multiple beam transmission system adopts equivalent plus merge. According to the numerical and simulative results, multiple beam transmission system could mitigate the adverse effect of strong turbulence on optical communication and decrease the bit error probability. In addition, this paper discusses how to improve the capability, which would be helpful for the design of wireless optical communication system.