Role of location-dependent transverse wind on root-mean-square bandwidth of temporal light-flux fluctuations in the turbulent atmosphere

Abstract

The root-mean-square (RMS) bandwidth of temporal light-flux fluctuations is formulated for both plane and spherical waves propagating in the turbulent atmosphere with location-dependent transverse wind. Two path weighting functions characterizing the joint contributions of turbulent eddies and transverse winds at various locations toward the RMS bandwidth are derived. Based on the developed formulations, the roles of variations in both the direction and magnitude of transverse wind velocity with locations over a path on the RMS bandwidth are elucidated. For propagation paths between ground and space, comparisons of the RMS bandwidth computed based on the Bufton wind profile with that calculated by assuming a nominal constant transverse wind velocity are made to exemplify the effect that location dependence of transverse wind velocity has on the RMS bandwidth. Moreover, an expression for the weighted RMS transverse wind velocity has been derived, which can be used as a nominal constant transverse wind velocity over a path for accurately determining the RMS bandwidth.

Simulation Method for the Impact of Atmospheric Wind Speed on Optical Signals in Satellite–Ground Laser Communication Links

“…where |r| ≤ D/2 is a point located on the pupil plane within the aperture, D indicates the receiving lens's diameter, P c represents the mode coupling coefficient, P a represents the total optical power entering the receiving aperture, U i (r) = U 0 exp[χ(r) + iS(r)]M(r) denotes the incident optical field transmitted at the aperture, U 0 (r) [2] is the optical field in the absence of turbulence [8][9][10], χ(r) is the amplitude fluctuations of the optical wave field, S(r) describes the complex phase perturbation induced by atmospheric turbulence, M(r) [2] is the aperture transmittance function, U m (r) [1] is the back-propagated fiber mode profile in the receiver aperture plane (A), and the asterisk indicates the complex conjugate. The mode coupling coefficient (P c ) can be written as follows [1,24]:…”

“…For slant transmission, the refractive index's atmospheric structure constant in the Hufnagel-Valley model is expressed as follows [3,9]:…”

“…Additionally, it introduced the concept of the weight-averaged transverse wind speed. The findings revealed that under isotropic turbulence conditions, variations in the transverse wind speed primarily influence the root-mean-square bandwidth because of its magnitude rather than its direction [9]. Using the power spectrum inversion method, we constructed a turbulent phase screen to simulate the temporal variations in turbulence caused by atmospheric wind speed.…”