On the implemetation aspects of adaptive power control algorithms in free-space optical communications

Atmospheric turbulence has made a significant contribution in free-space optical (FSO) communications´ areas of research. Assuming slowly varying channel, a feedback can be implemented to overcome the problem of fading. In comparison with all former published works, in this paper, we apply an algorithm to reduce average power consumption by regulating transmitter Erbium Doped Fiber Amplifier (EDFA) gain given channel state information (CSI). As a benchmark, a simple but non practical power control algorithm is introduced and discussed in this paper. To make the algorithm more practical, the quantized counterpart of the algorithm is introduced and its performance is compared to continuous one. It is shown by consuming 4dB more power than the continuous algorithm, we can simply implement a practical quantized power control algorithm. The statistical analysis of the proposed adaptive algorithms is performed, considering a complex model of the channel, including a low power transmitting laser, EDFA statistical model, channel fading, channel attenuations, receiver lens, photodetector model and all sources of optical and electrical noise. It is shown the proposed algorithm brings significant improvements over its non-adaptive counterpart.