Concept and realization of measuring spatial structure of atmospheric optical turbulence by the fiber optical turbulence sensor array

Abstract

In this article, a high quality fiber optical turbulence sensing array contains several sensors is proposed to obtain time series of air refractive index fluctuations. A fixed sensor is supposed to be set as the origin and others to be arranged in Cartesian coordinates respectively. Under the spatial configurations above, two-point correlation algorithm is used to give two order structure parameters and multipoint correlation algorithm for more structure information about scalar turbulence. For each direction, two-point spatial correlation coefficients varying with distance are provided. Meanwhile spatial power spectrum and outer-scales according to the data are introduced. Multipoint correlations can give more structure information such as the interactions between scales and the spatial structure of relevant fluctuations. In the one-dimension circumstance for instance the x-axis, spatial correlation coefficient tends to take oscillation. After a short-time averaging, it tends to decrease with the increase of spatial displacement, and then tends to zero after outer scale. Further study show that within the limit of outer scale, diurnal variation of the spatial correlation coefficient and intensity reveal a higher similarity, the relevancy is about 60% and keeps stable; once the distance goes across the outer scale, they are uncorrelated. In short, utilizing the fiber optical turbulence sensing array is a new method for measuring spatial correlation of optical turbulence. It can overcome some problems from single-point measurement, especially when using Taylor’s frozen-turbulence hypothesis. Some structural information of optical turbulence not only makes the theory of scalar field more abundant, but also in favor of some problems about optical propagation.