Longitudinal turbulent overfocusing of radiation in optical receivers.

The effect of longitudinal overfocusing of the radiation in optical receivers that is due to refractive-index fluctuations in air has been experimentally investigated. The dependence of the magnitude of the source-image plane shift on the turbulence intensity along the path is estimated. It is shown that the use of a variable observation plane, which takes into account the shift of the source image plane with the change in the turbulent state of a medium, permits reduction of the mean spot size by a factor of 1.