Atmospheric turbulence effects on a wavelength diversified ground-toUAV FSO link

The use of free-space optical (FSO) communications links are envisioned as a viable option for providing a temporary high-bandwidth communications link between a ground station and an unmanned aerial vehicle (UAV). The presence of atmospheric turbulence causes three different phenomena to occur, namely beam wander, scintillation and beam spread, each of which is a wavelength dependent phenomenon. In this paper, simulation tools are used to investigate the effects of atmospheric turbulence on a wavelength diversified ground-to-UAV FSO communications link. This paper compares the effects of atmospheric turbulence on three different wavelengths, 1.55 mu m, 0.85 mu m and 10 mu m. Each of these wavelengths has different advantages depending on prevalent weather conditions and atmospheric turbulence conditions. Based on the effects of atmospheric turbulence on each wavelength, a wavelength diversity scheme is proposed in order to optimize the performance of the FSO link. The largest problem associated with establishing a ground-to-UAV FSO link is alignment and tracking of the FSO link. For this reason, the wavelength diversity scheme is further analyzed as a method to optimize link acquisition and tracking of the ground-to-UAV link by exploiting various characteristics of each wavelength.