High sensitivity Mach–Zehnder interferometer based on peanut-shaped hollow-core fiber

A curvature and temperature sensor based on a double peanut-shaped hollow-core fiber (HCF) Mach–Zehnder interferometer (MZI) is reported and demonstrated for the first time. In the sensor, the two ends of the HCF are fused into two spherical shapes and sandwiched with two spherical-shaped single-mode fibers (SMFs) to form a double peanut-shaped structure (PSS). When incident light injects the HCF through the PSS, the light can greatly stimulate form fundamental mode to cladding modes and achieve high sensitivity in external environment detection. We successfully adjust the curvature and temperature sensitivity by controlling the length of HCF. The maximum curvature sensitivity is -648.17 pm/m−1 when the HCF is 0.73 mm, and the maximum temperature sensitivity is 25.42 pm/°C when the HCF is 0.97 mm. In addition, the simulation shows that the coupling efficiency of the sensor can be significantly improved by changing the diameter of the PSS, which provides a new method for making high-sensitivity sensors by using HCF in the future.