Abstract

For the free-space optical (FSO) communication system, the spatial coherence of a laser beam is influenced obviously as it propagates through the atmosphere. This loss of spatial coherence limits the degree to which the laser beam is collimated or focused, resulting in a significant decrease in the power level of optical communication and radar systems. In this work, the analytic expressions of wave structure function for plane and spherical wave propagation through anisotropic non-Kolmogorov turbulence in a horizontal path are derived. Moreover, the new expressions for spatial coherence radius are obtained considering different scales of atmospheric turbulence. Using the newly obtained expressions for the spatial coherent radius, the effects of the inner scales and the outer scales of the turbulence, the power law exponent, and the anisotropic factor are analyzed. The analytical simulation results show that the wave structure functions are greatly influenced by the power law exponent α , the anisotropic factor ζ , the turbulence strength σ ~ R 2 , and the turbulence scales. Moreover, the spatial coherence radiuses are also significantly affected by the anisotropic factor ζ and the turbulence strength σ ~ R 2 , while they are gently influenced by the power law exponent α and the inner scales of the optical waves.

Highlights

  • In recent years, the traffic carried by the telecommunication network is growing significantly, especially the wireless network

  • We have presented new sets of expressions for the wave structure functions and for the spatial coherence radiuses of the free-space optical waves such as the plane waves and the spherical waves propagating in a horizontal path of a free space, which is disturbed by anisotropic turbulence

  • The wave structure function (WSF) increase as the anisotropy increases while the spatial coherence radius (SCR) decrease on the contrary

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Summary

Introduction

The traffic carried by the telecommunication network is growing significantly, especially the wireless network. Mobile data traffic and mobile service spectrum have increased by many orders of magnitude from 2010 to 2020 [1] This is an important topic of the sixth generation (6G) wireless communication. OWC technology provides a basic combination of the various advantages necessary to deliver highspeed services to optical backbone networks It provides an unlicensed spectrum, almost unlimited data rate, low-cost development, and convenient installation [2]. The anisotropic factor is used to describe anisotropy of the atmosphere turbulence [7], and the generalized non-Kolmogorov von Karman spectrum of Wireless Communications and Mobile Computing the anisotropic atmospheric turbulence is available [8,9,10]. We derive new WSF and SCR expressions for the plane waves and the spherical waves which propagate in the anisotropic non-Kolmogorov atmosphere turbulence. In addition to the influences of the power law exponent, the turbulence strength and the anisotropic factor, which are all affecting parameters of the WSFs and SCRs, are carefully analyzed

Anisotropic Non-Kolmogorov Spectrum with Inner and Outer Scales
The Expressions for Wave Structure Functions
New Expressions for Spatial Coherence Radius
Evaluations Using Numerical Analysis
Evaluation on SCRs
Conclusion
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