Multi-rings modulation and hole-assisted fiber under single-mode operation

In this paper, we propose a novel air-hole-assisted step refractive index fiber. Air holes located in the cladding can ensure the single-mode operation of the proposed fiber. The triangular refractive index ring structure further enlarges large mode field area. Bending performance of the proposed fiber is analyzed by the finite element method with perfectly matched layers, and the influence rule of each structure parameter on bending performance is summarized. Numerical results show that the proposed fiber can achieve stable single-mode operation over a wide wavelength range from 1.5 mu m to 1.9 mu m at a tight bending scale of 10 cm. Effective mode field area can reach 1002.73 mu m2, and the bending loss of fundamental mode (FM) is only 0.000827 dB/m at the working wavelength of 1.55 mu m; meanwhile, the loss ratio between higher-order mode (Homs) and fundamental mode is 7240. The proposed fiber is more stable compared to photonic crystal fibers. The change in bending angle does not affect the single-mode operation, and this novel fiber has potential applications in high-power lasers.