Low-Loss Nodeless Conjoined-Tube Anti-Resonant Hollow-Core Fiber

We propose a novel nodeless conjoined-tube hollow-core fiber (CT-HCF) with elliptical arcs as negative curvature boundaries to limit the leakage of transmitted light. The cladding nodes are effectively eliminated by the attachment of arcs to the outermost dielectric tube. Numerical simulations performed using the full-vector finite element method show that a significant reduction in fiber loss over a wide bandwidth can be obtained. The confinement losses for the proposed fiber are two orders of magnitude lower than those obtained for a typical CT-HCF. The total loss, including confinement loss and surface scattering loss, is also investigated. The proposed fiber shows a loss of less than 0.1 dB/km for a bandwidth of 450 nm, with a minimum loss of 6.58·10 ⁻⁵ dB/m at 1.45 μm. Moreover, the proposed fiber exhibits good single-mode performance, with the higher-order mode extinction ratio reaching a maximum value of 39341 at 1.7 μm.