Wander of a Gaussian-Beam Wave Propagating through Kolmogorov and Non-Kolmogorov Turbulence along Laser-Satellite Communication Uplink

Fazhi Wang,Qi Yuan,Daosen Liu,Shuang Feng,Wenhe Du

doi:10.3390/atmos13020162

Abstract

It is accepted that there exists two kinds of atmospheric turbulence in the Earth’s aerosphere—Kolmogorov and non-Kolmogorov turbulence; therefore, it is important to research their combined impacts on laser-satellite communications. In this paper, the exponential power spectra of refractive-index fluctuations for non-Kolmogorov turbulence in the free troposphere and stratosphere are proposed, respectively. Based on these two spectra, using the Markov approximation, beam wander displacement variances of a Gaussian-beam wave are derived, respectively, which are valid under weak turbulent fluctuations condition. On this basis, using a three-layer altitude-dependent turbulent spectrum model for vertical/slant path, the combined influence of a three-layer atmospheric turbulence on wander of a Gaussian-beam wave as the carrier wave in laser-satellite communication is studied. This three-layer spectrum is more accurate than a two-layer model. Moreover, the variations of beam wander displacement with beam radius, zenith angles, and nominal value of the refractive-index structure parameter on the ground are estimated. The theory of optical wave propagation through non-Kolmogorov atmospheric turbulence is further enriched and a theoretical model of a three-layer atmospheric turbulence beam wander for a satellite-ground laser communication uplink is established.

Highlights

Since the 1960s, as one of the advanced satellite communication technologies, satellite laser communication technology has attracted much attention from the scientific community because it has some potential advantages, including higher data rates, larger communication capability, better anti-disturbance, low probability of intercept, less volume, less mass, lower power consumption, no restrictions for frequency use, etc. [1]
We proposed an exponential power spectra of refractive-index fluctuations for non-Kolmogorov turbulence in the free troposphere and the stratosphere, and on this basis, modified a three-layer altitude-dependent power spectrum of refractive-index fluctuations for satellite-to-ground and ground-to-satellite links, which is composed of the exponential Kolmogorov turbulence power spectrum of the boundary layer, the exponential non-Kolmogorov power spectrum turbulence of the free troposphere, and the exponential non-Kolmogorov power spectrum of the stratosphere
The theoretical model of beam wander displacement variances of a Gaussian-beam wave propagating through Kolmogorov and non-Kolmogorov turbulence along laser-satellite communication uplink was developed and applied to characterize the displacement of the instantaneous center of the beam for the small zenith angle

Summary

Introduction

Since the 1960s, as one of the advanced satellite communication technologies, satellite laser communication technology has attracted much attention from the scientific community because it has some potential advantages, including higher data rates, larger communication capability, better anti-disturbance, low probability of intercept, less volume, less mass, lower power consumption, no restrictions for frequency use, etc. [1]. In addition to atmospheric attenuation and scintillation, the downlink is affected seriously by the beam wander, which is equivalent to increase the pointing error of the satellite laser communication system. The fluctuation conditions gradually expanded from weak to strong fluctuations It is well-known that beam wander can cause time-varying power fades at the receiver terminal and further deteriorates the performance of satellite laser communication system. It is significant to study the combined influence of the three-layer atmospheric turbulence on the wander of the laser beam wave as the carrier wave in laser satellite communication. This work lays a scientific foundation for the establishment of an atmospheric turbulence compensation model and has certain scientific significance for improving the performance of a satellite-ground laser communications system, on-orbit experiment and practical application

Three-Layer Altitude Spectrum Model of Refractive-Index Fluctuations

Beam Wander

Simulation and Analysis

Conclusions