Have you looked at "Performance analysis of OOK, BPSK, QPSK modulation schemes in uplink of ground-to-satellite laser communication system under atmospheric fluction" by Yan Li, Mi Li, Yin Poo, Jiachen Ding, Minghui Tang, and Yuangang Lu in Optics Communications Vol 317, 15 Apr 2014, Pgs 57-61? This article might give you some insights.