Optical link stabilization by controlling focus of received beam in mini-unmanned aerial vehicle-to-ground free-space optical communications

Abstract

To stabilize an optical link, in this study, we propose to control the focus of the received laser beam in free-space optical (FSO) communications between mini-unmanned aerial vehicles (UAVs) and ground stations. Numerical calculations confirm that the coupling efficiency of the received laser beam to an optical fiber (OF) at the ground station is improved by compensating for the shift in the received beam’s focal position caused by the movement of the mini-UAV. Additionally, we conduct an outdoor experiment in which a laser beam is transmitted between two ground positions under the influence of atmospheric turbulence. This experiment indicates the feasibility of controlling the focus of the received beam in realistic environments. These results are expected to significantly contribute to the stabilization of optical links in mini-UAV-to-ground FSO communications.