Study On The Characteristics Of Atmospheric Channel In Wireless Optical Communication Systems

The study of the characteristics of Atmospheric channel in Wireless Optical Communication Systems is currently the key problems for the exploiture of the laser communication system in civil and military application.Firstly, the history and current situation about Wireless optical communication at home and abroad is introduced. The key technologies, merits and shortcoming as well as the application foreground about Wireless optical communication is summarized. Secondly, the atmospheric attenuation and turbulence effects are summarized and analyzed. By using the numerical calculation method, the characteristic about the laser attenuation is calculated, the relationship about the attenuation of the optical signal with transport distance and optical wavelength are found. It shows that the attenuation of clouds and fog are generally larger than the aerosol and increase quickly with the decrease of visibility. That is clouds and fog has great limits to the application of laser system. The laser intensity fluctuation in atmospheric turbulence channel is studied. In view of BER's importance, the BER model of the laser propagating through fog and turbulence is used. The BER are calculated under different visibility and transport distance. It shows that the BER not only changes with the attenuation of clouds and fog, but also with turbulent intensity. The BER decreases with optical wavelength increasing. The BER increases rapidly with turbulence intensity increasing. On Earth-space paths, the BER induced by turbulence is smaller than the BER on the horizontal paths of Earth surface. The larger is the elevation, the smaller is the BER. The effect of inner-scale on BER is smaller than the change of turbulent intensity. Hence, the change of turbulent intensity is the main factor that induces the BER for optical signal propagating through atmosphere. At last, some fairly mature methods and technologies to improve the performance of Laser wireless system are presented.These studies have great academic significance and practical values in the development and application for various ground-base laser systems.