21 August 2009 Measurement of beam wander using cone modulation in an optical free-space retro-reflective link
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Proceedings Volume 7464, Free-Space Laser Communications IX; 74640X (2009); doi: 10.1117/12.826570
Event: SPIE Optical Engineering + Applications, 2009, San Diego, California, United States
Abstract
Understanding the relative contribution of beam wander and scintillation to the power fluctuations due to atmospheric turbulences is essential to improving the performance of Free Space Optical Communication systems. In prior work [5], we briefly mentioned that cone modulation could be used to measure the beam wander. We presented a few experimental results showing high correlation between the power fluctuation and the measured beam wander. Here we present the method in details, as well as the results of a more extensive set of measurements. The measurements are done using an optical interrogator tracking a passive retro-reflector over distances of 800 and 8km, using a cone modulation frequency of 625Hz, a rate significantly higher than the Greenwood frequency. We recorded the data at 10 kHz sampling rate, and ran off-line analysis to evaluate the correlation between the position of the beam relative to the retro-reflector and the fluctuations of the power received by the interrogator. We also recorded the angle of arrival fluctuations, which allows for an evaluation the correlation between the beam wander and the angle of arrival. The same data was used to calculate the Cn2 structure constant from the statistics of the angle of arrival, in order to correlate the amplitude of the beam wander to the strength of the turbulence.
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Eric Saint Georges, Stanley Uecke, "Measurement of beam wander using cone modulation in an optical free-space retro-reflective link", Proc. SPIE 7464, Free-Space Laser Communications IX, 74640X (21 August 2009); doi: 10.1117/12.826570; https://doi.org/10.1117/12.826570
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KEYWORDS
Modulation

Beam analyzers

Optical testing

Retroreflectors

Digital signal processing

Free space optics

Statistical analysis

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