Under favorable visibility conditions, scintillation becomes the limiting factor in estimating free space optical (FSO) link availability. In the summer of 2001, Terabeam performed several experiments to characterize the impact of scintillation on FSO products under development. In the experiment, a transmitter and a receiver were placed 1000 and 2600 meters apart and operated with the receiver at several different sized apertures and under diverse atmospheric conditions. The experimental probability of fade is then calculated and compared with two theoretical models, namely the lognormal and the gamma-gamma.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.