Designing of a Free Space Optical Communication System and Evaluation of its Performance in the Face of Climatic Change Phenomena

Free-Space Optical (FSO) Communication has many advantages such as high bandwidth and high security and can also be a good alternative to radio communication systems. The main problem with the use of FSO is the presence of atmospheric phenomena such absorption, scattering and turbulence. This effect causes not only the weakening of the laser light transmission but also causes the multipath phenomena and behavior similar to the fading in the radio communication channels. In this paper, a model is presented to investigate the FSO attenuation and turbulence effect on its performance. Designing of an FSO system using a combination of methods such as Aperture averaging, Multiple Input Single Output (MISO) and Line code 1B4B to reduce the effects of turbulence has been examined and the behavior of system using error probability rate (BER) diagram and the probability of cutting (Outage) in different climatic conditions has also been simulated. Link budget analysis shows that an FSO system with 4 transmitters each with 200mW of optical power and a receiver with at least 25cm optical aperture can communicate data, in the moderate turbulence condition, with a maximum range of 10 km and a BER better than 10-6.