Turbulence statistics applied to calculate expected turbulence-induced scintillation effects on electro-optical systems in different climatic regions
Turbulence statistics applied to calculate expected turbulence-induced scintillation effects on electro-optical systems in different climatic regions
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湍流统计用于计算不同气候区域的电光系统预期的湍流引起的闪烁效应
DOI：
10.1117/12.618308
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
K. Weiss
中科院分区：
文献类型：
--
作者：
K. Weiss
折射率结构参数Cn2是最常用于描述光学活性湍流的参数。过去，FGAN-FOM在温和气候（中欧，德国）、干旱（夏季）和半干旱（冬季）气候（中东，以色列）进行了长期实验。由于Cn2通常作为一天中的时间和季节的函数而变化，因此其对电光系统的影响应以统计方式表示。我们组成了一个统计数据库的Cn 2值。在夏季和冬季任意选择一个月的时间段，计算中午前后（最强湍流时间）、夜间和日出前后（最弱湍流时间）两个小时的累积发生频率。2004年10月，我们将长期湍流实验扩展到亚北极气候（北欧，挪威）。我们在积雪覆盖的地形上的湍流测量的第一个结果表明，Cn 2值与中欧冬季的测量值相似，甚至更高。利用统计数据库计算了不同气候条件下自由空间光学系统（FSO系统）的预期孔径平均闪烁指数。计算是针对商用FSO系统进行的，波长分别为785 nm和1.55 µm，接收器孔径直径分别为60 mm和150 mm，水平路径位于地面以上2.3 m和10 m两个高度。
The refractive-index structure parameter Cn2 is the parameter most commonly used to describe the optically active turbulence. In the past, FGAN-FOM carried out long-term experiments in moderate climate (Central Europe, Germany), arid (summer), and semiarid (winter) climate (Middle East, Israel). Since Cn2 usually changes as a function of time of day and of season its influence on electro-optical systems should be expressed in a statistical way. We composed a statistical data base of Cn2 values. The cumulative frequency of occurrence was calculated for a time interval of two hours around noon (time of strongest turbulence), at night, and around sunrise (time of weakest turbulence) for an arbitrarily selected period of one month in summer and in winter. In October 2004 we extended our long-term turbulence experiments to subarctic climate (North Europe, Norway). First results of our turbulence measurement over snow-covered terrain indicate Cn2 values which are similar or even higher than measured values in Central European winter. The statistical data base was used to calculate the expected turbulence-induced aperture-averaged scintillation index for free-space optical systems (FSO system) in different climates. The calculations were performed for commercially available FSO systems with wavelength of 785 nm and 1.55 µm respectively and with aperture diameters of the receiver of 60 mm and 150 mm for horizontal path at two heights, 2.3 m and 10 m above ground.