In this Letter, we investigate the transition of the well-known Fabry–Perot (FP) and antiresonant (AR) mechanisms via a single-mode fiber (SMF)-capillary-SMF structure. The critical length for this transition is analytically found as a linear relation with the capillary inner diameter based on the ray optic method, which shows the agreement with both numerical simulations and experiments. Evolutions of the transmission and reflection spectra verify that FP and AR mechanisms are closely related to the critical length. An observed AR envelope modulated by the FP mechanism in the reflection strengthens gradually with the increase of the capillary length, which is expected to be a novel method for potential applications in multi-parameters sensing because of its combined mechanisms. The transition and critical lengths can be also found and explained using the same method in other types of AR fibers or waveguides with a hollow core.

中文翻译：

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通过SMF-毛细管-SMF结构转变法布里-珀罗和反共振机制

在这封信中，我们通过单模光纤（SMF）-毛细管SMF结构研究了著名的Fabry-Perot（FP）和反共振（AR）机制的转变。基于射线光学方法，分析发现了该转变的临界长度与毛细管内径呈线性关系，这与数值模拟和实验均显示出一致性。透射光谱和反射光谱的演变证明FP和AR机制与临界长度密切相关。随着毛细管长度的增加，通过FP机制调制的观察到的AR包络随着毛细管长度的增加而逐渐增强，由于其结合的机制，有望成为一种在多参数传感中潜在应用的新方法。