Performance Improvement of OOK Free-Space Optical Communication Systems by Coherent Detection and Dynamic Decision Threshold in Atmospheric Turbulence Conditions

In this letter, we analyze the performance improvement of on–off-keying free-space optical communication systems in atmospheric turbulence conditions due to coherent detection and the dynamic decision threshold (DDT) scheme. Our analytical results show that the DDT scheme provides a 5.7-dB power reduction for achieving a bit error rate of
$10^{-3}$
compared with the conventional fixed decision threshold scheme. In addition, the improvement achieved by the DDT scheme is related to the strength of amplitude and phase fluctuations, not to the power of the local oscillator.