1 September 2006 Passive long range acousto-optic sensor
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Alexander Graham Bell's photophone of 1880 was a simple free space optical communication device that used the sun to illuminate a reflective acoustic diaphragm. A selenium photocell located 213 m (700 ft) away converted the acoustically modulated light beam back into sound. A variation of the photophone is presented here that uses naturally formed free space acousto-optic communications links to provide passive multichannel long range acoustic sensing. This system, called RAS (remote acoustic sensor), functions as a long range microphone with a demonstrated range in excess of 40 km (25 miles).
© (2006) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Dan Slater, Dan Slater, } "Passive long range acousto-optic sensor", Proc. SPIE 6304, Free-Space Laser Communications VI, 63040E (1 September 2006); doi: 10.1117/12.681389; https://doi.org/10.1117/12.681389

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