Dual step-index ring core antiresonant fiber for broadband transmission of numerous OAM modes with high purity and quality
Rosni Sayed, Abdul Khaleque, Kumary Sumi Rani Shaha, Md. Anowar Kabir, Rifat Ahmmed Aoni
Abstract
We present a design strategy of a dual step-index ring core antiresonant fiber (DSI-RC-ARF) to significantly enhance the number of orbital angular momentum (OAM) modes while preserving their high purity and transmission quality over the O-E-S-C-L-U bands. The proposed fiber features a central ring of high refractive index, surrounded by outer and inner rings of refractive indices that gradually decrease from the central ring in both directions. The proposed fiber consists of a unique core arrangement having a central ring with a higher refractive index that can support up to 206 OAM modes across the 1.28 μ m to 1.70 μ m wavelength range without any higher-order radial modes or phase distortion. Additionally, the core is surrounded by inner and outer rings with gradually varying refractive indices, which helps to maintain the mode quality above 97% and mode purity mostly above 98%. The fiber also renders a uniform dispersion variation with wavelength, large effective mode area, nonlinear coefficients below 1.62 /W/km throughout the entire bandwidth, very low confinement loss ranging from 10 −11 to 10 −9 dB/m, and longer 2 π and 10 ps walk-off length for higher-order OAM modes with ellipticity and bending. This innovative fiber design enhances the capabilities of antiresonant fibers in modern communication systems, making it ideal for efficient broadband transmission of high-capacity OAM modes.