Adaptive Beam Divergence for Expanding Range of Link Distance in FSO With Moving Nodes Toward 6G

Free space optics (FSO) provides high-capacity optical wireless communications. To maintain an FSO link with a moving node, beam should be steered toward it. As the distance gets shorter, it becomes difficult to link. This is because radius has not largely expanded yet at shorter transmission distances and received power decreases as receiver moves away from center of beam. In this letter, we address adaptive divergence control method expand range within which can maintained. Theoretical evaluation results show our minimum 5 m in assumed use cases, though was least 20 fixed divergence. Furthermore, confirmed angle changing interval were feasible.