Polynkin Pavel, Peleg Avner, Klein Laura, Rhoadarmer Troy, Moloney Jerome
College of Optical Sciences, The University of Arizona, Tucson, Arizona 85721, USA.
Opt Lett. 2007 Apr 15;32(8):885-7. doi: 10.1364/ol.32.000885.
Using laser beams with less than perfect spatial coherence is an effective way of reducing scintillations in free-space optical communication links. We report a proof-of-principle experiment that quantifies this concept for a particular type of a partially coherent beam. In our scaled model of a free-space optical communication link, the beam is composed of several partially overlapping fundamental Gaussian beams that are mutually incoherent. The turbulent atmosphere is simulated by a random phase screen imprinted with Kolmogorov turbulence. Our experiments show that for both weak-to-intermediate and strong turbulence an optimum separation between the constituent beams exists such that the scintillation index of the optical signal at the detector is minimized. At the minimum, the scintillation reduction factor compared with the case of a single Gaussian beam is substantial, and it is found to grow with the number of constituent beams. For weak-to-intermediate turbulence, our experimental results are in reasonable agreement with calculations based on the Rytov approximation.
使用空间相干性欠佳的激光束是减少自由空间光通信链路中闪烁的有效方法。我们报告了一项原理验证实验，该实验针对特定类型的部分相干光束对这一概念进行了量化。在我们的自由空间光通信链路缩放模型中，光束由几个部分重叠且相互不相干的基本高斯光束组成。通过印有科尔莫戈罗夫湍流的随机相位屏来模拟湍流大气。我们的实验表明，对于弱到中等强度以及强湍流，组成光束之间存在一个最佳间距，使得探测器处光信号的闪烁指数最小化。在最小值处，与单个高斯光束的情况相比，闪烁降低因子相当可观，并且发现它随着组成光束的数量增加而增大。对于弱到中等强度的湍流，我们的实验结果与基于里托夫近似的计算结果合理吻合。
