Ma Xuelian, Liu Lu, Zhang Xiaoning, Tang Junxiong
Institute of Quantum Electronics, School of Electronics Engineering and Computer Science, Peking University, Beijing 100871, China.
Appl Opt. 2010 Feb 1;49(4):718-23. doi: 10.1364/AO.49.000718.
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.
空间捕获对于建立大气光链路至关重要。在捕获过程中，检测概率会因大气湍流引起的闪烁而降低。我们提出一种孔径阵列捕获方案来抑制这种闪烁噪声。孔径阵列由N个接收元件组成，每个接收元件包含一个用于接收光信号的孔径、一个用于滤除背景辐射的光学滤波器以及一个用于检测光信号的电荷耦合器件（CCD）。当CCD采样时间短于闪烁特征时间时，基于湍流大气中的对数正态分布推导了孔径阵列捕获的长期平均检测概率（LTADP）的数学模型。在这种情况下，CCD采样时间内的平均信号计数和检测概率都是随机变量；因此，需要考虑平均信号计数的概率密度，并基于此概率密度计算LTADP。仿真结果表明，当单孔径信噪比固定时，这种孔径阵列捕获方案能够有效抑制闪烁并提高LTADP。
