Abstract
Turbulence and absorption of seawater are two important factors affecting the signal transmission quality of underwater optical communication link. Here, we study the channel capacity and bit error rate of an underwater extinction communication link with a coaxial double-position power Gaussian vortex carrier based on Rytov approximation theory. The study finds that channel capacity and bit error rate are the nonlinear functions of the dimensionless structural parameter and reach maximum and minimum values at |α| = 1, respectively. The seawater absorption has a great influence on the channel capacity but not bit error rate. The communication link with large receiving aperture, small transmitting beam diameter, long wavelength of light source in a seawater window, and more OAM channels has high channel capacity.
Highlights
Orbital angular momentum (OAM) is a new dimension that can be encoded, which can be adopted by optical [1,2,3,4] and acoustic [5,6,7] communication systems to improve the information capacity of links
Acoustic OAM has the advantages of low loss of underwater communication and perfect theoretical [5,6,7] and experimental model compared with underwater optical OAM transmission, its fatal weakness is the low channel capacity and signal transmission rate of underwater acoustic communication link
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]
Summary
Orbital angular momentum (OAM) is a new dimension that can be encoded, which can be adopted by optical [1,2,3,4] and acoustic [5,6,7] communication systems to improve the information capacity of links. Compared with the Laguerre–Gaussian beam and the Bessel–Gaussian beam, a diffraction- and attenuation-resistant random vortex beam is a more resistant to seawater turbulence and seawater absorption and the optical communication link, which consists of a long-wave length anti-diffraction and anti-attenuation random vortex carrier and a small receiving diameter, has high channel capacity [19]. When the vortex carrier carries two OAM modes with different amplitudes and rotation directions in the absorption of turbulent seawater, whether the transmission characteristics are different from the above research conclusions, that is, whether there are more factors that can optimize the communication system. The influence of coaxial double-position power vortex Gaussian carrier parameters and seawater turbulence parameters on the channel capacity and bit error rate (BER) of the communication link is studied.
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