Propagation characteristics of Airy vortex beams in bi-anisotropic unstable stratified oceanic turbulence

ObjectiveAs a key carrier for breaking the Shannon channel capacity limit in marine wireless optical communication systems, vortex beams have long been restricted in the in-depth development of this field and the breakthrough of system performance due to the strong uncertainty, time-varying characteristics, and modeling difficulties of real marine environments. This paper systematically investigates the evolution law of the channel capacity of Airy Vortex (AV) beams in oceanic turbulence, aiming to evaluate its feasibility and application potential as a high-performance information carrier in complex oceanic channels, and to provide theoretical guidance for the design of long-distance, high-capacity underwater optical communication systems.MethodsBased on the Rytov approximation theory and the extended Huygens-Fresnel principle, a marine turbulence power spectrum model with finite outer scale, dual anisotropic factors, and unstable stratification is adopted to characterize the actual oceanic turbulence environment. Numerical simulations are performed to quantitatively analyze the effects of different main ring widths, receiving aperture sizes, oceanic turbulence parameters (including the rate of dissipation of kinetic energy per unit mass of fluid, the rate of dissipation of mean-square temperature, and the temperature-salinity contribution ratio), and five propagation distances ranging from 50 m to 300 m on the channel capacity of AV beams..Results and DiscussionsNumerical results demonstrate that AV beams with larger main ring widths and smaller receiving apertures (less than 4 cm) exhibit higher channel capacity, which is attributed to the weaker beam spreading and less energy loss during propagation; a larger anisotropy factor in oceanic turbulence leads to a higher channel capacity of AV beams, indicating that the anisotropic characteristics of oceanic turbulence can effectively mitigate the degradation of channel capacity; under the same marine environment, the channel capacity of AV beams with the same main ring width (5 mm) is higher than that of Perfect Vortex (PV) beams, which verifies the superiority of AV beams in resisting oceanic turbulence and maintaining high channel capacity.ConclusionsThe research results of this paper reveal the channel capacity evolution mechanism of AV beams in complex oceanic turbulence environments, and provide reliable theoretical support and technical reference for the beam selection, light source parameter setting, and system optimization design of long-distance, high-capacity wireless optical communication systems in oceanic scenarios.