Measuring outer scale in atmospheric optical turbulence from the point view of spatial correlation function

A theory about scales in atmospheric optical turbulence vortex from the point view of spatial correlation function is described. Then an experiment is carried out to prove this theory by the fiber optical turbulence sensor array near the ground. Results show that the outer scale has a mean value of 0.62m and varies from 0.34m to 0.95m by doing a nonlinear fitting on spatial correlation functions. With this method, the value of the outer scale can be given directly without any hypothesis when the optical turbulence is well-developed. A question about how the trend of the spatial correlation function show when the displacement approaches the outer scale is solved. This research can be regarded as a progress about understanding the characters of spatial correlation function in optical turbulence.