Abstract: A method of evaluating free-space optical propagation characteristics includes emitting a plurality of laser beams from a corresponding plurality of laser sources, receiving laser beams at different target points, and measuring the time-based spatial fluctuations between the laser beams thus received. The respective distances from the laser sources to each target point are used to normalize the time-based spatial fluctuations. The difference between the normalized spatial positions of the laser beams at the target points is derived and used to obtain the frequency spectrum of time-based fluctuations of the spatial positions.