Terahertz fiber with multi-concentric ring cores for OAM modes propagation

A novel fiber incorporating central hollow, porous isolated layers, and concentric ring cores is proposed for the simultaneous propagation of multi-terahertz (THz) orbital angular momentum (OAM) modes with low-level inter-core and inter-mode crosstalk. The designed fiber can efficiently support 132 OAM modes in 0.6 ∼ 1.5 THz, 178 OAM modes in 0.7 ∼ 1.5 THz, etc, the high-order radial modes are suppressed within the whole frequency range meanwhile, and the number of OAM modes can be further boosted by further increasing the number of ring cores. In addition, the fiber has low confinement loss, flat dispersion, and high purity over a wide operating range. Hence it can be applied in mode-division multiplexing (MDM) based on OAM combined with core-division multiplexing (CDM) in THz range, and is also compatible with wavelength-division multiplexing (WDM) and multi-level modulation formats. The realized fiber is expected to dramatically extend the transmission capacity and spectral efficiency.