We describe an experiment where we made a direct measurement of the bit-error rate of a high-order adaptive optics laser communications system. We describe a quantitative characterization of a repeatable atmospheric turbulence aberration generator and both static and dynamic characterizations of a 19-channel adaptive optics system. We show a reduction of the bit-error rate by a factor of 41.5 under specific laboratory conditions.
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.
Recent experiments performed at UNC Charlotte indicate that we can achieve a reduction in the bit-error rate (BER) for a laser communication system with the implementation of low-order (tip/tilt) adaptive optics in a free-space communication link. We previously reported indirect measurements of the BER by measuring scintillated signals with and without an adaptive optics loop operating. By assuming standard values for receiver noise, we calculated the BER that we would expect. In this paper, we report on the direct measurements of the BER that we observe with the laboratory adaptive optics laser communication system. By directly comparing both the low (“0”) bits and the high (“1”) bits of the outgoing laser modulation signal with the PIN diode-detected signal we determine the BER as a function of various propagation, receiver electronics, and adaptive optics system parameters. Scaling our visible measurements to atmospheric paths and IR wavelengths, we compare our results with vigorous theoretical calculations.
Recent experiments performed at UNC Charlotte indicate a reduction in the bit-error rate for a laser communication system with the implementaion of low-order adaptive optics in a free-space communication link. With simulated atmospheric tilt injected by a conventional PZT tilt mirror, an adaptive optics system with a Xinetics tilt mirror was used in a closed loop. The laboratory experiments replicated a monostatic propagation with a cooperative wavefront beacon at the receiver. Due to constraints in the speed of the processing hardware, the data is scaled to represent an actual propagation of a few kilometers under moderate scintillation conditions. We compare the experimental data and calculated bit-error rate before correction and after correction and compare it with a rigorous theoretical prediction.
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