Mach–Zehnder Photonic Crystal Interferometer in Cavity Ring-Down Loop for Curvature Measurement

Abstract-An all-fiber Mach-Zehnder interferometer curvature sensor fabricated by collapsing both ends of a photonic crystal fiber connected to a single-mode fiber is described. The interferometer is inscribed into the cavity ring-down loop and shows high sensitivity of 0.7311(μs)^-1 · m and high repeatability when a curvature of 0.4135 to 0.8122 m^-1 is applied. High correlation value of 0.997 is obtained with low standard error of 1.05%. This corresponds to a minimum detectable curvature of 4.849 × 10^-3 m^-1. The proposed sensor also displays low sensitivity to temperature with a value of 0.0008(μs ·° C)^-1.