8 December 2004 Calculations of bit error rates for retroreflective laser communications systems in the presence of atmospheric turbulence
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A retro-reflective communications system comprises a laser transmit/receive station and a remote retroreflector that can be switched between "on" and "off" states. The laser illuminates the remote station and a collection telescope directs the reflected light to an associated detector the output of which is interpreted as logic 1 or 0. Atmospheric turbulence affects the outgoing illumination beam, resulting in beam spreading and in fluctuations in the intensity (scintillation)1. The reflected beam undergoes further turbulence induced spreading and there is an enhancement in the intensity fluctuations. These fluctuations mean that the logic level of signals may be wrongly identified, leading to bit errors. The signal may fade below detectable levels for periods of time, leading to sections of the bit stream being lost. We develop a description of the intensity fluctuations in terms of the Gamma-Gamma distribution2, and incorporate the effect of "aperture averaging" associated with the retro-reflector and the collection aperture. We characterise signal-to-noise ratios and calculate bit error rates as a function of retro-reflector cross-section and contrast for a variety of ranges, turbulence levels and system configurations. We also identify the characteristic timescale over which the atmosphere causes changes of intensity and discuss the implications.
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Andrew M. Scott, Andrew M. Scott, Kevin D. Ridley, Kevin D. Ridley, "Calculations of bit error rates for retroreflective laser communications systems in the presence of atmospheric turbulence", Proc. SPIE 5614, Advanced Free-Space Optical Communications Techniques and Technologies, (8 December 2004); doi: 10.1117/12.580844; https://doi.org/10.1117/12.580844

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