Adaptive control of a MEMS steering mirror for free-space laser communications

Abstract

This paper presents an adaptive control scheme for laser-beam steering by a two-axis MEMS tilt mirror used in current free-space optical communications systems. In the control scheme presented here, disturbances in the laser beam are rejected by a high-performance linear time-invariant feedback controller augmented by the adaptive control loop, which determines control gains that are optimal for the current disturbance acting on the laser beam. The variable-order adaptive control loop is based on an adaptive lattice filter that implicitly identifies the disturbance statistics from real-time sensor data. Experimental results are presented to demonstrate the effectiveness of the adaptive controller for rejecting multi-bandwidth jitter. These results demonstrate that the adaptive loop significantly extends the jitter-rejection bandwidth achieved by the feedback controller alone.