In this paper, the Average Bit Error Rate of the signal in the Free Space Optical system modulated with On-Off keying scheme is calculated and analysed. The Average Bit Error Rate is determined in the case of an atmospheric channel modelled with Gamma-Gamma distribution, Log-Normal distribution, K distribution and I-K distribution. The results are presented both analytically and graphically for different lengths of the Free Space Optical link and the strength of the atmospheric turbulence. The quality of the received signal based on the Average Bit Error Rate for weak, moderate and strong atmospheric turbulences, different lengths of the transmission section and different Signal-to-Noise Ratio values was analysed. The operation of the Free Space Optical system in the observed environment was simulated and the transmission quality was analysed based on Bit Error Rate and Q factor.

In this paper, the signal transmission in the Free -Space Optics (FSO) communicati on system using the software package