Effect of aperture averaging on a 570-Mbps 42-km horizontal path optical link

Abstract

Optical communications offer high data rate satellite to ground communications in a small, low mass, and low power consumption package. However, turbulence-induced scintillation degrades the link performance as the zenith angle increases. To investigate the effect of atmospheric turbulence on the optical link at high zenith angles, we performed a 570 Mbps optical communications link across a 42 km horizontal path, and have measured the effects of aperture averaging on the irradiance variance. The variance clearly showed a dependence on the aperture size, decreasing with increasing aperture size. These results were used to calculate the log-amplitude variance and the atmospheric structure constant, C<SUB>n</SUB><SUP>2</SUP>, across the link. The bit error rates across the link were also measured. The results show that the link performance was dominated by burst errors with error rates that ranged from 10<SUP>-6</SUP> to 10<SUP>-2</SUP>, increasing with decreasing aperture size.