Propagation characteristics of the perfect vortex beam in anisotropic oceanic turbulence

Abstract

The propagation model of orbital angular momentum (OAM) modes carried by the perfect vortex (pv) beam through anisotropic oceanic turbulence links is established and the factors influencing the OAM propagation are discussed. The findings show that the self-focusing property of pv beams is beneficial to the propagation of OAM modes: a smaller topological charge, a smaller initial radius, and an optimized half-ring width can alleviate degrading effects of turbulence on the pv beam. Additionally, the pv beam with a longer wavelength is more resistant to turbulent interference. The oceanic conditions with a higher dissipation rate of kinetic energy per unit mass of seawater, larger values of anisotropy and inner-scale factor, a smaller temperature–salinity contribution ratio, or a lower mean-squared temperature dissipation rate can improve the signal mode detection probability. The results are expected to further optimize the design of OAM-based underwater wireless communication systems.

Capacity of the Weakly Absorbent Turbulent Ocean Channel with the Coaxial Double-Position Power Gaussian Vortex

“…As increases, channel capacity decreases. This study is similar to studies for the single vortex information carrier [9][10][11][12][13][14][15][16][17][18][19][20][21][22], and salinity fluctuations have a greater impact on the channel capacity with a larger number of channels.…”

“…In Figure 8, we investigate the effects of the temperature-salinity contribution ratios and different wavelength λ on the channel capacity of the RCDPPGV carrier in the "seawater light transmission window". Similar to any other type of beam [9][10][11][12][13][14][15][16][17][18][19][20][21][22], Figure 8 shows that the channel capacity of the RCDPPGV carrier increases with increasing λ . This is because the long-wavelength beam has lower scintillations [25].…”

“…This result indicates that the link with single-position power Gaussian vortex has maximum channel capacity. Similar to any other type of beam [9][10][11][12][13][14][15][16][17][18][19][20][21][22], Figure 6 shows that the channel capacity also increases with the increase in channel number. Figure 7 shows that channel capacity decays rapidly as absorption increases.…”

“…However, due to the presence of various constituents in the ocean and oceanic turbulence, seawater scattering and absorption inevitably limit the transmission of information carried by OAM modes over optical communication links [8][9][10][11][12][13][14][15][16][17][18]. Therefore, in order to reduce the above negative effects of seawater and consider the relationship between signal transmission probability and channel capacity, a lot of studies have been conducted from the perspectives of OAM detection probability and link channel capacity.…”

“…[15]. The self-focusing characteristic of a perfect optical vortex beam is beneficial to the propagation of the OAM mode, and the perfect optical vortex beam with smaller topological charge, smaller initial radius, and optimized half-ring width can reduce the degradation effect of the PV beam caused by turbulence [16]. The normalized received probability of signal OAM modes carried by finite energy frozen wave is independent of the quantum number of OAM modes in weak seawater turbulence, and the higher normalized received probability achieved in the smaller received diameter of the receiver, the larger the transverse size and longer the signal wavelength and the signal OAM modes [17].…”