Acoustic orbital angular momentum-based space division multiplexing for multi-channel data transmission

Due to the low attenuation in the water, an acoustic wave is currently considered a promising medium for long-distance underwater information transmission. Acoustic vortex (AV) provides an alternative to expand the channel capacity by exploring the orbital angular momentum dimension. In this work, based on the ring-array of sectorial transducers, we propose a scheme for constructing double-ring perfect acoustic vortex (DR-PAV) beams by applying the Fourier transformation of quasi-Bessel acoustic vortex (QB-AV) beams with different radial wave numbers. The radius and ring width of the inner and outer rings of the DR-PAV beam remain nearly constant, and the topological charge (TC) of the inner and outer rings are independently controllable. Subsequently, the inner and outer rings of the DR-PAV beam are further treated as two independent channels for data transmission. At the receiver end, decoding of DR-PAV beams with multiplexed TCs is achieved by using a simplified double-ring receiver array. This multi-channel underwater data transmission scheme is expected to be applied in acoustic communication in the future.