Investigation of advanced control for adaptive optics in free-space optical communication

Free-Space Optical (FSO) communication can play an important role in meeting the demands of future high throughput and high data rate communication applications. However, atmospheric turbulence induced effects degrade the performance of FSO communication links resulting in high volume data losses. Adaptive Optics (AO) can be used to mitigate the effects of atmospheric turbulence in FSO links. A key challenge is the fact that turbulence scenarios in FSO links are stronger and FSO links are expected to remain operational in all conditions. This requires a robust AO controller that can cope with the more extreme turbulence. In this work, the design and simulation of one such advanced controller based on Linear Quadratic Gaussian control (LQG) is presented. The operation of the controller is demonstrated with an end-to-end simulation. The simulation uses multi-layer phase screens for representing the turbulent atmosphere and angular spectrum propagation for accuracy. We present here the performance of the AO controller through an analysis of the Strehl ratio, the fiber coupling efficiency and the power scintillation index on the fiber achieved.