Analysis of beam wander effects for a horizontal-path propagating Gaussian-beam wave: focused beam case

Abstract

Abstract. Failure of the first-order Rytov approximation to properly predict the scintillation index of a large-aperture focused beam, or an uplink collimated ͑or focused͒ beam, has been discussed in several recent publications, which cite beam wander effects as the main reason for this failure. We use computer simulations to examine several aspects of beam wander phenomena on a propagating convergent beam in the weak-fluctuation regime over a horizontal path at high altitude for which the refractive index structure parameter is on the order of C n 2 = 1.39 ϫ 10 −16 m −2/3 . Simulation results are presented at various ranges up to 10 km for ͑1͒ the beam wander centroid displacement, ͑2͒ the kurtosis excess of the irradiance profile, ͑3͒ the irradiance profile, ͑4͒ the meansquare hot spot displacement from the boresight and from the centroid, and ͑5͒ the scintillation index at the optical axis of the beam. In addition, simulation results are compared with theoretical models.

Laser beam propagation over the sea surface: experimental data and verification of simulations

“…The split-step method is well-documented in the literature. 12,[14][15][16][17][18] In this method, free-space propagations, turbulence and thermal blooming effects are alternately applied to the beam propagating between transmitter and receiver using a diffraction integral in the transformed domain and a series of uncorrelated (in propagation direction) random phase screens. The split step method provides a particularly useful technique to characterize the propagated beam in the far field when analytical theory is absent or insufficient.…”

“…For the root mean square centroid movement √〈𝛽 𝑐 2 〉 we can subsequently employ the relation √〈𝛽 𝑐 2 〉 = √0.56 ⋅ 〈𝑟 𝑐 2 〉. 14,26 Finally, for the scintillation index we deviate from first-order Rytov theory and rely on extended Rytov theory where the additional effect of beam jitter on the scintillation index is taken into account through an effective pointing error jitter variance 𝜎 𝑝𝑒 2 . 12,25 This latter quantity can be expressed using the equations above and a spatial Gaussian filter 𝐻 𝑗𝑖𝑡𝑡𝑒𝑟 that only takes turbulent scale sizes between the beam dimension and turbulence coherence width into account:…”

“…The partial propagations allow varying the physical dimensions of the series of intermediate in-and output planes and their pixel sizes along the propagation following the method described by Schmidt. 14 The turbulence along the path is captured by an array of uncorrelated refractive index or phase screens. These screens are generated in the Fourier or spectral domain by filtering random numbers with the appropriate power spectral density, a method which is well-documented.…”

Air turbulence effects on performance of optical wireless communication with crosstalk in server backplane

“…Hot and cool air currents due to the cooling fans within the server produce temperature gradients that lead to scintillation in the beam spot at the receiver [11] . Turbulence also leads to the beam wander phenomenon that affects the irradiance profile of the received signal [12,13] . Nevertheless, FSOIs between server components are considered to offer a competitive solution for the next generation of servers due to the low index of refraction of air, which is lower than that of any waveguide, the straightforward and short distance three-dimensional (3D) arrangement capabilities, and the wide optical bandwidth facilitating high data rates with low achievable bit error rates (BERs).…”

“…7 and 8). Rigorous theoretical analysis [12,13,19] cannot be exploited to predict the experimental results due to the experimental environmental conditions that are highly uncommon when compared to common air turbulence conditions [4] .…”