基于投影光瞳分布的星地激光通信波前探测

Wavefront sensing for FSO systems based on projected pupil plane pattern

为了解决星地自由空间光学通信系统中的提前角问题,采用了一种基于光强传输的新型波前探测技术——投影光瞳面分布(Projected Pupil Plane Pattern,PPPP),并通过实验室实验验证了该技术的可行性。PPPP基于TIE光强传输公式,根据不同传输距离下光强分布的变化反解出大气湍流引起的波前畸变。由于PPPP采用的是上行通信激光本身的后向瑞利散射,其测量的大气湍流方向与通信卫星方向一致,因此可以有效解决星地激光通信中的提前角问题。实验模拟了1 m口径的地基望远镜作为上行激光发射装置和后向散射光斑成像设备,通过等效高度分别为10 km和17 km的上行激光后向散射光斑图像来实现对10 km以下大气湍流的波前探测。实验采用的波前畸变模拟装置包括空间光调制器和透明塑料片,实验结果表明,对不同的波前畸变PPPP和通用的夏克-哈特曼波前探测器可以实现相似的波前重构,两者重构相位的残差约为初始相位的30%。

Addressing the challenge of point ahead angle(PAA)in satellite-based free-space optical communication systems,this paper introduces a novel wavefront sensing method,the Projected Pupil Plane Pattern(PPPP),utilizing the transport-of-intensity equation(TIE).Laboratory experiments confirm its viability.The PPPP method,rooted in TIE,can deduce wavefront distortions due to atmospheric turbulence by analyzing variations in light intensity distribution over different transmission distances.Utilizing the back Rayleigh scattering from the communication laser,PPPP's atmospheric turbulence measurements align with the satellite's direction,offering an effective solution to PAA-related issues in satellite-ground la‐ser communications.In our experiments,a 1-m ground telescope simulates an upward laser transmitter and captures the backscattered light for imaging.We measure wavefront distortions caused by atmospheric tur‐bulence up to 10 km using backscattered light from altitudes of 10 km and 17 km.These distortions are simulated using a spatial light modulator or a transparent plastic sheet.The results demonstrate that PPPP and the commonly used Shack-Hartman wavefront sensor provide comparable wavefront reconstructions for various distortions,with the reconstructed phase's residual difference around 30%of the initial phase.