Research On Propagation Performance For Light Scattering In Free Space

Free Space Optics (FSO) communication sprung up again with the progress of the high power semiconductor lasers, high-sensitive optoelectronic detectors, demand for low-cost and fast access network. FSO had widely promising applications since it integrated the advantages of fiber communication and other traditional wireless communication technologies, such as huge capacity, low cost, convenient deployment and flexibility. Firstly, the thesis analyzed the FSO communication system, introduced the advance in FSO and their application.Then we discussed the propagation performance of light in atmosphere, such as atmosphere absorption, atmosphere scattering and the impact of atmosphere turbulence. The scattering performance analysis focused on Rayleigh scattering and Mie scattering, as well as the unite effect of scattering and absorption on the propagation performance of light were analyzed.On the basis of scattering performance, we analyzed the cross section of scattering when light propagation in atmosphere. The scattering performances of propagation under the different particle distribution condition were discussed. And we deduced the approximately calculate method in the condition of sparse distribution particle and dense sparse distribution particle, and gave the application condition. Then we analyzed the impact of random continuous medium and turbulence medium, calculated the change in scattering intensity under different propagation distance and different turbulence intensity. From the result, we discussed the possibility of establishing the scattering FSO system.Finally, based on the analysis of the performance of the light propagation in the fog, a bit-error rate(BER) model of FSO system was established. And certain BERs were calculated under different visibility and extinction coefficient using the MTALAB. The simulation showed that if the signal light power and the atmosphere visibility was enough, the bit-error rate of the light signal would be very low even through the span beyond the visual range. So the establishment of the reliable atmospheric light communications would be possible in the fog. Also we discussed the prospective advance in the key technology for the FSO system.