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26 April 2002 Ground detectors for optical communications from deep space
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Proceedings Volume 4635, Free-Space Laser Communication Technologies XIV; (2002)
Event: High-Power Lasers and Applications, 2002, San Jose, California, United States
A variety of avalanche photodiodes (APD's) were tested with pulse position modulated (PPM) Q-switched laser pulses incident on the detector, with varying amounts of attenuation. The detector output was recorded and post- processed in order to determine the signal and noise slot statistics, as well as, to estimate bit-error-rates (BER). The probability distribution functions predicted by a Webb+Gaussian model were compared to the measured slot statistics, as were theoretical BER curves. Allowing noise equivalent temperature to be a free fitting parameter yielded good fits between measurements and theory. All the measurements used 256-ary PPM and 10 - 25 ns slot widths, with a Q-switched Nd:YVO4 laser modulated at 50 K - 100 K pulses per second. A 3 mm diameter, silicon (Si) APD with 80% quantum efficiency (QE) at 532 nm displayed a sensitivity deteriorated to 18 photons/bit in the presence of 100 photons per 25 ns slot of background light. A 0.8 mm diameter near infrared (NIR) enhanced Si APD with QE of 0.38 displayed sensitivities of 23 - 32 photons/bit for a BER of 10-2 at 1064 nm in the absence of background light. Backgrounds of 400 photons per 25 ns slot degraded the sensitivity to approximately 58 photons/slot. Finally a 3 mm diameter NIR enhanced Si APD yielded a sensitivity of approximately 100 photons/bit 1064 nm for BER of 10-2 with no background present.
© (2002) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Abhijit Biswas, Beckett Madden-Woods, Meera Srinivasan, Victor Vilnrotter, and William H. Farr "Ground detectors for optical communications from deep space", Proc. SPIE 4635, Free-Space Laser Communication Technologies XIV, (26 April 2002);

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