Dynamic Adaptive Beam Control System Using Variable Focus Lenses for Laser Inter-Satellite Link

One of technical challenges in laser inter-satellite link (ISL) is the mitigation of performance degradation caused by pointing errors and angle-of-arrival (AoA) fluctuations arising unavoidably from satellite movements and vibrations. In this paper, we propose the dynamic adaptive beam control (ABC) technique implementable by using variable focus lenses (VFLs) at both the transmitter and receiver. In this technique, we monitor the instantaneous pointing error and AoA fluctuation induced by satellite vibrations and then provide feedback corrections to the VFL-based ABC system. The VFLs at the transmitter and receiver adjust their focal lengths adaptively to the amount of pointing error and AoA fluctuation, respectively, to minimize the link loss. VFLs operated by electro-wetting or electromagnetic actuator are fast enough to respond to the vibrations. We design the proposed dynamic ABC system for laser ISL by using the double-lens configuration and VFLs. An exemplary system design is presented when commercially available VFLs are utilized. Our simulation study shows that the proposed dynamic ABC technique offers improved transmission performance, compared to the static and the dynamic ABC technique applied to either the transmitter or receiver.