Prospects and challenges of free space optical communications

Free space optical (FSO) transmission is a technology which uses a narrow laser beam to transmit the signal from the source to the destination through the free space. Although it has various advantages, a laser beam propagating through the atmosphere is subjected to different kind of disturbances causing the attenuation of the signal and, in some extreme conditions, leading to the link outage. In fact, the atmospheric turbulences and the chemical nature of the medium is the main source of link attenuation. In this paper, we present the different challenges of FSO communications: absorption, pointing errors, atmospheric turbulence and scattering phenomenon. Moreover, based on the strength of turbulences, we will detail the FSO channel modeling. Then, we introduce some techniques to overcome the weakness presented by FSO link under different strength of atmospheric turbulences.Scopu