Atmospheric Turbulence Effects on Bit Error Rate in Lognormal and Negative Exponential Channel in FSO Link

With the increase in the population worldwide, there is a need of a wellordered communication system which can manage the demands of the users. Radio communication system is not able to manage the over increasing demand of bandwidth. Optical wireless or FSO is one such solution to the problem. It has many advantages like large bandwidth, spectrum is unlicensed, high security, and ease of installation. But due to atmospheric turbulences, the link quality is compromised. One of the major issues faced in free space optical links is the induced fading due to the channel which in turn deteriorates the performance of the link. Different channel models are used for different turbulence conditions. Lognormal and negative exponential are two turbulence channel models discussed in this paper. For lowturbulence condition and where propagation distance is less, we use lognormal model. Negative exponential model is employed where we have strong turbulence conditions and the link length spans a few kilometers. Various modulation techniques are used in a FSO link. In this paper, we have used BPSK modulation technique. Effects of atmospheric turbulence on the channel link are observed considering parameters such as refractive index structure parameter Cn2 and mean irradiance Io. The change in the value of bit error rate due to change in the values of these parameters has also been listed.