The propagation length of surface plasmon polaritons (SPPs) increases with increasing wavelength, which makes it possible to use radiation from the far-infrared and terahertz ranges to create communication devices in which SPPs will be carriers of information. In this paper, we consider methods for implementing the multiplex transmission of information along cylindrical conductors using a combination of SPPs with orbital angular momentum. The work was supported in parts by the RSF grant No. 19-12-00103.
It is shown that there are two methods for generating ring surface plasmon polaritons (SPPs) using high-order Bessel beams. In the first method, free radiation is transformed into an SPP using a binary phase axial grating illuminating a cylindrical diffraction grating connected to a cylindrical waveguide. The second method uses the diffractive coupling of a Bessel beam to an axisymmetric conductor. In this case, as an option, before the capture, the beam can be first transformed by a lens, forming an annular vortex beam at its focus. After passing through the waveguide, the mode composition of the beam is decoded, for example, using diffractive optical elements, and each communication channel is registered by an individual detector. A device that implements these methods is demonstrated.