Airborne laser communications and performance enhancement by equalization

Free space optical (FSO) communication is a promising candidate for emerging broadband applications, considering that RF spectrum is already congested, rendering accommodation of additional RF broadband channels difficult and costly. Communications via RF signals are reliable but cannot support emerging high data rate services unless they use a large portion of the costly radio spectrum. FSO communications offer enormous data rates but operate much more at the mercy of the atmospheric environment, such as scintillation and multi-scattering through fog and clouds. Since RF paths are relatively immune to these phenomena, combining the attributes of a higher data rate but bursty link (FSO) with the attributes of a lower data rate but reliable link (RF) could yield attributes better than either one alone, enabling a high availability link at high data rates. This transmission configuration is typically called a hybrid RF/FSO wireless system. The focus of this paper will be on applying well-known equalization techniques to FSO, to further enhance availability of RF/FSO wireless system.