Measurement of the bit-error rate of an adaptive optics, free-space laser communications system, part 1: tip-tilt configuration, diagnostics, and closed-loop results

Abstract
We describe an experiment where we made a direct measurement of the bit-error rate of a low-order adaptive optics laser communications system. The adaptive optics system consisted of a two-axis tip-tilt corrector. In the paper we describe the driver system for the tilt aberration generator, the tilt sensor, the control system for the corrector mirror, and the diagnostic electronics for measuring and recording the bit-error rate. Finally, we present results of a closed-loop experiment where we report bit-error rate improvement up to a factor of 42.