Aperture-array acquisition scheme for optical links in atmospheric turbulence

Spatial acquisition is essential for the establishment of atmospheric optical links. The detection probability in the acquisition process can be degraded by atmospheric-turbulence-induced scintillation. We present an aperture-array acquisition scheme to suppress this scintillation noise. The aperture array is composed of N receiving elements, each containing an aperture to receive the optical signal, an optical filter to reject the background radiation, and a charge-coupled device (CCD) to detect the optical signal. The mathematical model of the long-term average detection probability (LTADP) for the aperture-array acquisition is derived based on the lognormal distribution in turbulent atmosphere, when the CCD sample time is shorter than scintillation characteristic time. In this case, the average signal count and the detection probability in the CCD sample time are both random variables; therefore, the probability density of the average signal count needs to be considered and the LTADP can be calculated based on this probability density. The simulation results show that this aperture-array acquisition scheme can suppress scintillation effectively and enhance the LTADP when the one-aperture signal-to-noise ratio is fixed. (C) 2010 Optical Society of America