Optimizing differential mode delay and crosstalk in nested anti-resonant node-less hollow-core fibers for mode-division multiplexing

Hollow-core fibers have recently gained significant attention by demonstrating ultra-low-loss, surpassing the attenuation benchmark put forward by conventional single-mode solid-core fibers. In this work, we explore the multimode operation in Nested Anti-resonant Node-less Fibers (NANF) fibers for mode division multiplexing strategy to overcome the inherent limitations of space division multiplexing. Unlike prior studies focused on solid-core fibers, our study investigates, for the first time in a hollow-core fiber, how various fiber design parameters impact the trade-off between differential mode delay and crosstalk. Numerical simulations reveal that although structural parameters such as ring spacing or nested anti-resonant ring size have minimal impact on the trade-off, resonant conditions play a significant role in the differential mode delay when the operational wavelength is closer to the resonant wavelength.