The optical measurement of atmospheric turbulence strength is often subject to the effects of scintillation saturation. In the saturation regime, the intensity variance no longer increases with turbulence strength. In some instances, the observed behavior with respect to turbulence strength shows a flattening of the variance followed by a shallow drop-off with further increases in turbulence. The Air Force Research Laboratory requires a robust instrument for determining path-integrated turbulence effects on a laser propagating over a 50 km path under a variety of clear-air atmospheric conditions and turbulence strengths. The approach described here is based on the measurement of the Mutual Coherence Function (MCF). The MCF doesn't saturate since it depends on the total wave structure function, a function consisting of a non-saturating phase term as well as the saturating log- amplitude term. The sensor itself is an interferometer which measures fringe visibility. In addition to a measure of turbulence strength, or C$+2$/$-n$/, the wave structure function itself can be determined. The latter feature is an especially important one for determining whether or not Kolmogorov statistics prevail.
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