Mach–Zehnder interferometer based on tapered PCF with an up-tapered joint for curvature, strain and temperature interrogation

We propose a Mach–Zehnder interferometric sensor based on tapered Photonic Crystal Fiber (PCF) with up-tapered collapsed region for measurement of parameters such as curvature, strain and temperature. The up-tapered collapsed region helps in excitation of the cladding modes in PCF and these modes interfere with each other at the tapered region of PCF which is completely collapsed. Three tapered PCFs with varying geometry are fabricated and their effect on curvature sensitivity is analyzed. Experimental results show that the proposed sensor has a curvature sensitivity of 7.56 nm m−1 with negligible hysteresis effect. Moreover, the proposed sensor shows a strain sensitivity of 1.6 pm/μe along with a maximum temperature sensitivity of 51.6 pm °C−1. In addition to this, the response of the interference pattern to all these parameters is found to be linear.