Wideband low confinement loss hollow core anti-resonant fiber with semi-circular and semi-elliptical nested tubes

We propose three hollow-core anti-resonant fibers with different nested tube structures and numerically analyse their confinement loss, single-mode performance and bending loss by using the finite element method. The results show that the nested semi-elliptical structure FD#2 and the hybrid nested FD#3 structure have excellent transmission performance. The confinement loss of FD#2 and FD#3 at 1.55 µm is 0.00037 dB/km and 0.0004 dB/km respectively, and the high order mode extinction ratio is around 1700 for both FD#2 and FD#3. The bandwidths of FD#2 and FD#3 with losses less than 0.01 dB/km are within 1.36–1.73 μm and 1.42–1.8 μm, respectively. In addition, the bending resistance of FD#2 and FD#3 is excellent, with bending losses of 0.003 dB/km and 0.001 dB/km at a bending radius of 8 cm. We also evaluated the manufacturing tolerance range of these two structures in the actual manufacturing process. The structure proposed in this paper is expected to provide new ideas for the design of nested elements, and provide more possibilities for optical fiber design suitable for large-capacity data transmission and gas sensing applications.