共查询到18条相似文献,搜索用时 156 毫秒
1.
2.
基于Taylor湍流冻结假设理论,在不同湍流折射率谱型条件下,推导得出了光波闪烁和相位起伏频谱的表达式;数值计算了湍流谱型中折射率标度指数、内尺度以及外尺度变化时对光波频谱的影响。结果表明:随着折射率起伏标度指数的增大,闪烁频谱的低频段不再仅为常数,高频段下降的幂率逐渐增大,同时相位频谱在整个起伏频率段下降的幂率越来越大;湍流内尺度的增加将引起光波频谱的高频段下降的幂率越来越大;而随外尺度的减小,闪烁频谱低频段的振幅减小,这种影响在大口径接收时较为明显,相位谱的低频段幂率减小。 相似文献
3.
4.
5.
部分相干光在大气湍流中的光强闪烁效应 总被引:5,自引:0,他引:5
以修正Rytov方法为基础,利用部分相干高斯-谢尔(GSM)光束模型并结合Andrews的唯像闪烁模型,研究部分相干光在大气湍流中的光强闪烁效应。推导出适用于不同湍流情形的部分相干光对数光强起伏方差表达式,系统分析了部分相干光在大气湍流中的光强起伏方差。结果表明:在同等的湍流环境下,部分相干光比完全相干光的光强起伏方差要小;光束相干性越差,光强起伏越小,抗湍流能力越强。在不同大气湍流情形下,光源相干性、大气折射率常数等参数对光强起伏都有不同程度的影响。 相似文献
6.
多光束发射对湍流效应下激光传输的影响 总被引:2,自引:0,他引:2
大气湍流引起的光强起伏会导致大气闪烁、光束漂移、到达角起伏和波前畸变等效应.多光束发射技术是克服激光大气传输中光强起伏的有效途径之一.以单光束、双光束、四光束以及八光束发射为例,通过计算峰值光强、环围功率半径以及像散参数等光束质量参数,得到单光束和多光束大气传输的光强起伏特性.结果表明:随着光束数目的增加,峰值光强显著... 相似文献
7.
湍流路径积分参量与湍流大气中光的传播效应 总被引:5,自引:1,他引:4
根据光波在湍流大气中传播的理论分析了弱起伏条件下决定光波传播效应的折射率结构常数C^2n的各种路径积分参量之间的关系,导出了由光波的强度起伏所确定的等效折射率结构常数对计算大气相干长度与光波的到达角起伏,光束的扩展及漂移的相对偏差的表达式。针对折射率结构常数C^2n具有周期性,递减,递增和随 相似文献
8.
研究了部分相干高斯谢尔光束在大气湍流中的到达角起伏.主要采用湍流内外尺度的修正Von Karmon谱模型及广义惠更斯-菲涅尔原理和交叉谱密度函数推导出了部分相干光在大气湍流中的到达角起伏表达式.对比分析了湍流内外尺度、湍流强度、传输距离、源相干参数以及波长等参数对部分相干光在大气湍流水平路径上传输时的到达角起伏的影响.结果表明:随着传输距离的增加,到达角起伏越来越小;随着大气湍流内外尺度和源相干参数的增加,到达角起伏也越来越大;与部分相干光相比,完全相干光的到达角起伏受湍流影响很小;随着波长和湍流强度的减小,到达角起伏越来越小. 相似文献
9.
10.
湍流大气传输高斯谢尔光束的到达角起伏 总被引:13,自引:10,他引:3
研究了在弱大气湍流起伏环境下以窄带宽高斯谢尔光束为激光光源的大气通信问题,分析了大气湍流强度和光源空间相干度对通信光束到达角起伏的影响.采用窄带宽光场的交叉谱密度函数代替光场互相干函数的近似方法和采用包含大气湍流内外尺度的简化折射率谱密度函数,得出了湍流大气中传输高斯谢尔光束的波结构函数(WSF) 和到达角起伏方差解析近似关系.分析表明,光源的空间相干度和传输光束的湍流扩展是影响高斯谢尔光束的相位起伏结构函数和传输光束到达角起伏的重要因素. 相似文献
11.
The temporal power spectra of irradiance fluctuations reflect the frequency distribution of temporal statistical property of irradiance fluctuation. In this paper, new analytical expressions of the temporal power spectral models of irradiance fluctuations are developed for optical waves propagating through weak non-Kolmogorov turbulence with horizontal path. They are derived with the general modified atmospheric spectral model, and they consider the finite turbulence inner and outer scales, and have a general spectral power law value in the range of 3 to 4 instead of the standard power law value of 11/3. Numerical calculations are conducted to analyze the influence of non-Kolmogorov weak turbulence on the temporal power spectra of irradiance fluctuations. 相似文献
12.
Through extensive laboratory experimentation we demonstrate that the temporal frequency content of turbulence-induced scintillation strongly depends on the temperature gradient exerted at the propagation path of a collimated laser beam. We find a power law relating the turbulence strength induced by convection with the vertical temperature gradient and we show that the cutoff frequency of scintillation shows an approximately linear growth with turbulence strength, measured by angle-of-arrival fluctuations. The impact of these findings are discussed in the context of free-space optical communications. 相似文献
13.
Angle-of-arrival fluctuations for wave propagation through non-Kolmogorov turbulence 总被引:1,自引:0,他引:1
Recently the increasing experimental evidences have shown that atmospheric turbulence statistics does not obey Kolmogorov’s power spectrum model in portions of the troposphere and stratosphere. These experiments have prompted the investigations of optical wave propagation through atmospheric turbulence described by non-classical power spectra. In this paper, using an original approach and considering a non-Kolmogorov power spectrum which uses a generalized power law instead of constant standard power law value 11/3 and a generalized amplitude factor instead of constant value 0.033, the variances of the angle-of-arrival fluctuations of the plane and spherical waves are derived in weak turbulence for a horizontal path. The concise closed-form expressions are obtained and used to analyze the influence of spectral power law variation on the angle-of-arrival fluctuations. 相似文献
14.
15.
It is well known that atmospheric turbulence causes significant variations of the arrival angle of laser beams used in free-space
communications. Usually, angle-of-arrival fluctuations of an optical wave in the plane of the receiver aperture is calculated
by Kolmogorov’s power spectral-density model. Unfortunately, recently increasing experimental evidence has shown that atmospheric
turbulence statistics does not obey Kolmogorov’s power spectrum model in some parts of the troposphere and stratosphere. These
experiments have prompted investigations of the optical-wave propagation through atmospheric turbulence described by nonclassical
power spectra. In this paper, employing a new approach and considering a non-Kolmogorov power spectrum with a generalized
power law instead of the constant standard power-law value 11/3 and a generalized amplitude factor instead of the constant
value 0.033, we derive the variances of the angle-of-arrival fluctuations of the plane and spherical waves in a weak turbulence
for the horizontal path. The concise closed-form expressions are obtained and used to analyze the influence of spectral power-law
variations on the angle-of-arrival fluctuations. In addition, the outer scale effect is also analyzed. 相似文献
16.
The turbulence inner scale plays an important role in investigating the irradiance scintillation index for optical wave propagating through atmospheric turbulence. However, previous expressions of the irradiance scintillation index, which were derived based on the general non-Kolmogorov spectral model, did not consider the influences of finite turbulence inner scale. In this study, based on the generalized exponential spectral model for non-Kolmogorov atmospheric turbulence, theoretical expressions of the irradiance scintillation index are derived for plane and spherical optical waves propagating through weak turbulence. The new expressions have considered the influences of the finite turbulence inner scale and the receiver aperture on the irradiance scintillation index. Numerical simulations are performed to analyze these parameters’ influences. 相似文献
17.
18.
New analytical expressions for the temporal power spectral models of angle of arrival (AOA) fluctuations are derived for optical plane and spherical waves propagating through weak non-Kolmogorov turbulence. They consider the finite turbulence inner and outer scales, and have a general power law value in the range of 3–4 instead of the standard power law value of 11/3. The results derived in this work can reduce correctly to the previously published analytic expressions for the case of plane and spherical waves propagation through Kolmogorov turbulence case. These results are useful for the understanding the potential impact of derivations from the standard Kolmogorov spectrum. 相似文献