title: Irradiance correlations in retro-reflected beams.
abstract: Communications links that utilize modulating retro-reflectors can make use of turbulence-induced fade information available at the remote data-signal terminal in order to optimize the data transfer rate. Experiments were conducted to measure the irradiance in both the direct and the retro-reflected beams. Both on-axis and off-axis components were recorded in order to further study the enhancement in the scintillation index observed in the retro-reflected beam. Measurements were made over a 1.8 km terrestrial range at AP Hill, Virginia. The degree of correlation of the received irradiance between the direct and double-passage beams is found to approach 90% on-axis and 70% outside of the Fresnel zone radius. The scintillation index in the retro-reflected beam is enhanced on-axis due to reciprocal optical paths. The measured scintillation indices, and the correlation of the retro-reflected beam with the direct beam, are compared with a point source, point scatterer, and point receiver model in the strong scintillation approximation.
authors.forename: Rita
authors.initials: R
authors.lastname: Mahon
authors.forename: Mike S
authors.initials: MS
authors.lastname: Ferraro
authors.forename: Peter G
authors.initials: PG
authors.lastname: Goetz
authors.forename: Christopher I
authors.initials: CI
authors.lastname: Moore
authors.forename: James
authors.initials: J
authors.lastname: Murphy
authors.forename: William S
authors.initials: WS
authors.lastname: Rabinovich