A free-space optical communications link to an unmanned aerial vehicle.

Abstract

Free-space optics (FSO) is an optical communications technology in which information is transmitted through the atmosphere on modulated optical beams. At the time of the development of FSO, it was envisioned to be a possible solution for provision of connectivity between customer premises and the optical backbone of today's telecommunications infrastructure. Due to limitations in the performance of FSO technology under adverse weather conditions, it is unable to provide sufficiently reliable connectivity for permanent telecommunications and networking applications. This dissertation investigates the deployment of FSO communications links to provide a temporary high-bandwidth communication line between a ground station and an unmanned aerial vehicle (UAV). The deployment of FSO links for ground-to-UAV communications is analyzed from the standpoint of feasibility based on beam steering tolerances and beam divergences, along with platform vibration analysis and active beam steering element comparisons. A mathematical model of a ground-to-UAV communication link is developed. Furthermore, an experimental analysis of a mechanical gimbal's accuracy and repeatability is performed. A wavelength diversity scheme in the presence of atmospheric turbulence is proposed to improve the alignment process. Finally, a wavelength diversity scheme is discussed which allows for transmission through radiation fog.