In free-space optical communication links, atmospheric turbulence causes fluctuations in both the intensity and the phase of received light signal, impairing link performance. In this paper, we describe several communication techniques to mitigate turbulence-induced intensity fluctuations, that is signal fading. These techniques are applicable in the regime in which the receiver aperture is smaller than the correlation length of the fading and the observation interval is shorter than the correlation time of fading. We assume that the receiver has no knowledge of the instantaneous fading state. When the receiver knows only the marginal statistics of the fading, a symbol-by-symbol Ml detector can be used to improve the detection performance. If the receiver has knowledge of the joint temporal statistics of fading, maximum- likelihood sequence detection (MLSD) can be employed, yielding a further performance improvement, but at the cost very high complexity. © 2005 - 2013 JATIT & LLS. All rights reserved.