Hybrid structure hollow-core anti-resonant fiber with low confinement loss at 1550 nm and high birefringence in the C-band

Abstract

This study proposes a hollow-core anti-resonant fiber with a hybrid nested cladding structure, aimed at achieving high birefringence, broad bandwidth, and low confinement loss. The proposed fiber has a three-layer nested ring structure in the x-direction and a parallel array of four holes in the y-direction. The anti-resonance effect of multi-layer nested tubes greatly reduces the confinement loss of the fiber, while high birefringence characteristics is achieved by using different thicknesses of the cladding tubes. The coupling of the two glass modes of hybrid nested tubes and the core mode broadens the bandwidth range of low-loss and high birefringence. The theoretical results indicate that the birefringence of the fiber can reach $1.06\times {10}^{-4}$, the confinement loss is as low as 1.8 dB/km at 1550 nm, and show the excellent single-mode characteristics with the higher-order mode extinction ratio 5539. Moreover, the confinement loss is as low as 2.4 dB/km at 2550 nm, and the birefringence reaches $1.1\times {10}^{-4}$. The structure achieves low confinement loss, high birefringence and single mode at 1.54 ∼ 1.67 µm and 2.25 ∼ 2.85 µm dual wavelength ranges, which is the widest bandwidth range among all reported polarization maintaining fibers.