Highly Sensitive Vector Curvature Sensor Based on Two Juxtaposed Fiber Michelson Interferometers With Vernier-Like Effect

In this paper, a highly sensitive vector curvature sensor based on two juxtaposed fiber Michelson interferometers (MI) with Vernier-like effect has been proposed and verified. Different from the structures of the conventional Vernier effect which are composed of the cascaded elements, the proposed configuration consists of two juxtaposed MIs. A triple-core fiber (TCF) is connected with a quite short piece of dual-side-hole fiber (DSHF), and the core of the DSHF and the two eccentric cores of the TCF are respectively constituted two juxtaposed MIs. The Vernier-like effect is caused by the very small refractive index difference between the two eccentric cores of the TCF. The most outstanding feature of the proposed structure is that the two MIs are both sensitive to curvature with opposite sensitivities, which makes the curvature sensitivity magnification factor twice that of the conventional Vernier effect structure. Experimental results show that the curvature sensitivity of the structure can reach -60.84~{\mathrm {nm/m}}^{-1} .