Broadband dispersion compensating ring-core fiber for orbital angular momentum modes

A well designed ring-core fiber can theoretically support numerous orbital angular momentum (OAM) modes with low crosstalk for space-division-multiplexing (SDM) data transmission, which is considered as a promising solution for overcoming the capacity crunch in optical communication network. However, the accumulated chromatic dispersion in OAM-fiber could limit the data speed and transmission distance of communication systems. A potential solution is to insert a dispersion compensation ring-core fiber with opposite-sign of dispersion in the transmission fiber along the fiber link. In this work, we propose a triple ring-core fiber with broadband negative dispersion. A highest negative dispersion of -24.47 ps/(nm·km) at 1550 nm and an average dispersion slope in the C band from -0.182 ps/(nm²·km) to 0.065 ps/(nm²·km) can be achieved to compensate multi-order dispersion. The effects of Ge-doping concentration fluctuation in the high-index ring core and fabrication errors on fiber geometric structures are also investigated. Furthermore, the effective mode area decreases as the widths of high-index rings increase due to the enhanced confinement ability. The designed triple ring-core fiber could offer potential for compensating OAM fiber links with positive dispersions.