Spatial intensity correlation and aperture averaging measurements in a 20 mile retro-reflected lasercom link

摘要

The Naval Research Laboratory has established a lasercom test bed across the Chesapeake Bay. The test bed uses a bi-static transmitter/receiver arrangement on the western shore of the Chesapeake Bay and various configurations of 5 cm retro-reflectors on the eastern shore to produce a 32 km retro-reflected lasercom test range. Experiments measuring the laser's transverse spatial profile after propagation over the test range have been performed. These experiments use an InGaAs CCD to image the pupil plane of the 40 cm receiver telescope and a frame grabber to store contiguous images for analysis. Analysis of these image sequences allows measurement of transverse spatial correlations across the received beam after 32 km retro-reflected propagation of the beam. Various configurations and numbers of retro-reflectors were studied to investigate the impact of number and arrangement of retro-reflectors on the received beam's spatial profile and spatial correlations. Additionally, since the CCD output is stored as a contiguous stream of images, analysis of these images' intensity variance in time allows measurement of aperture averaging effects as a function of number of retro-reflectors and their geometry. Results from these experiments are presented.