Studies Of The Effects Of Random Media On Free Space Optical Communication

Free space optical communication (FSO) has some applications in optical networks, where an optical gap exists between the backbone network and access network. Free space optics delivers cost effective optical connectivity and faster returns on investment for service providers. The numbers of FSO used in Telecommunication networks continues to grow as high bandwidth demands.Optical turbulence has a significant impact on the quality of free space optical communication system, in the presence of optical turbulence, the received signal exhibits random intensity fluctuations, which increase bit error rate. Optical turbulence results in many effects causing fluctuation in the received signal.The most important effects of optical turbulence on free space optical communications system are beam broadening, beam wander, and scintillation. Scintillation is the temporal redistribution of the intensity, results from the changes of air and from thermal gradients within the optical path caused by the variation in air temperature.In this dissertation, first our study the effects of optical turbulence on laser beam from previous work and from classic theories such as Rytov theory for Gaussian beam and kolmogorov theory of turbulence.Second we designed the experimental system for characterizing thermal turbulence on laser beam and we conducted field test for free space optical communication system then from experimental results we analyzed and evaluated the performance and availability of free space optical communication. The new method used to assess the effects of atmospheric turbulence on laser beam propagation is also presented. In this new approach, we take into account two changing parameters affecting the probability of fade.First is the received optical power and scintillation. Unlike other works, the probability of fade is in dependence on link distance.Finally, the experimental results show that there are several limitations and uncertainties such local whether that can make the results different in dealing with random media. In addition, these results agree with the weak turbulence regime for Rytov variance.