Simulations of Negative Curvature Hollow-core Fiber
COMSOL Multiphysics® software was used to simulate and analyze the transmission attenuation spectra of the negative curvature hollow-core fiber (NCHCF) over the wavelength from 2.7 μm to 4.2 μm. The effect of thickness of capillaries and the effect of the distance between the capillaries on confinement loss spectra were studied, which agreed well with the high-loss and low-loss bands predicted by the ARROW model. Based on mode confinement factor, a criterion for selecting the fundamental mode was proposed. Theoretical analysis has shown that the integral coefficient of 0.5 could effectively distinguish fundamental modes from high-order ones. This method was easy and accessible, and the error rate was fractional. This research could offer useful theoretic guidance for the design and fabrication of negative curvature hollow-core fiber.