High-Performance Bending Vector and Strain Sensor Using a Dual-Tapered Photonic Crystal Fiber Mach–Zehnder Interferometer

An in-line Mach-Zehnder interferometer based on a dual-tapered photonic crystal fiber (PCF) for bending vector and strain sensing is proposed and experimentally demonstrated. This sensor consists of a 25.7-cm homemade asymmetric twin-core PCF sandwiched between two tapers. Due to the asymmetry of twin cores, two opposite bending directions can be distinguished with the maximum bending sensitivities of 18.29 and -18.13 nm/m
^-1
, respectively. By applying axial strain to the sensor, the strain sensitivity reaches up to -10.65 pm/με. Because of the excellent linear response, the effect of temperature on strain and bending sensing can be eliminated by using a measurement matrix. The advantages of bending direction recognition, high strain and bending sensitivities, and compact structure make this sensor attractive for structural deformation monitoring.