Optical modal interferometer fiber strain sensor based on waist-enlarge fusion splicing

A novel strain sensor based on all-fiber modal interferometer is presented and experimentally demonstrated. It is formed by splicing a section of polarization-maintaining fiber (PMF) between two waist-enlarge fusion tapers. When the strain increased from 0 μe to 1764 με, the sensitivities of sensors with lengths of 34 mm, 40 mm and 47 mm are −1.36 pm/με, −1.22 pm/με, −1.06 pm/με, respectively. The absolute value of sensitivity will increase with the decrease of the length. The temperature response of the sensor is also discussed. The sensor has merits of simple fabrication, low cost, and good robustness.