Low confinement loss anti-resonant hollow-core fiber with a nested capsule shape tube

A dual-layer, elliptical, nested-capsule structure was proposed for hollow-core antiresonant fibers (DENC-ARFs). The key parameters of the newly designed fiber structure were optimized through numerical analysis, and finite-element method simulations were used to evaluate the confinement loss, bending loss, and single-mode performance of the design. The simulation results demonstrated that the confinement loss of the proposed structure remained below 0.01 dB/km over a broad wavelength range from 1.1 to 1.65 μm. This value was nearly an order of magnitude lower than that of most nested anti-resonant five-node fibers. Notably, over the 200 nm wavelength range from 1.4 to 1.6 μm, the confinement loss of the proposed structure fell below 0.001 dB/km, however within in the narrower range of 1.5–1.6 μm, the confinement loss exceeded 0.001 dB/km, reaching a minimum of 1.5549 × 10⁻⁷ dB/m at 1.5 μm. Furthermore, the bending loss was 5.79 × 10⁻⁴ dB/m at a bending radius of 6 cm, reflecting excellent bending performance. The higher-order mode extinction ratio exceeded 10 dB over the wavelength range of 1.3–1.6 μm, meeting the fundamental requirements for communication systems. These results underscore the potential of the proposed structure for applications in optical communication and gas sensing.