Multipath and Receiver Aperture Effects in a THz Wireless Communications Link using OAM Multiplexing

We simulate and analyze the multipath and receiver aperture effects in a THz wireless communication link using multiplexed orbital-angular-momentum (OAM) beams. In our simulation, a reflector is placed in parallel with the propagation direction of the transmitted beams. Due to the divergence of OAM beams, part of the transmitted beam is reflected and interferes with the part of the directly propagated beam, which leads to the multipath effect. Due to the limited receiver aperture size, the received beam profile along the radial direction might be limited which results in modal couplings in two-dimensional Laguerre-Gaussian (LG) spectrum. The simulation results show that (i) the interference between the reflected path and directed path could induce the intra-channel coupling; (ii) the multipath and receiver aperture effect induces power coupling across multiple two-dimensional LG modes which could lead to the inter-channel coupling; and (iii) higher OAM order (i.e., ℓ from ±1 to ± 5), lower frequency (i.e., f from 0.1 to 1 THz), or smaller beam waist (i.e., w
₀
from 2.5 to 10 cm) could induce larger intra- and inter-channel coupling.