Low loss negative curvature fiber with circular internally tangent nested tube in elliptical tubes

In this paper, we propose the low loss negative curvature fiber with circular internally tangent nested tube in elliptical cladding tubes. The leakage loss can be decreased because the elliptical cladding tubes have higher curvature at the core boundary compared to the circular cladding tubes. The circular nested tube in the elliptical cladding tubes provides an additional antiresonant reflection element to reach lower leakage loss. The simulation results show the negative curvature hollow core fiber in this paper has a low leakage loss in the spectral region from 1.3 mu m to 1.7 mu m. In particular, the leakage loss is 0.012dB/km at 1.55 mu m.