In-fiber modal interferometer for simultaneous measurement of curvature and temperature based on hollow core fiber

An in-fiber modal interferometer is presented and experimentally demonstrated for simultaneous measurement of curvature and temperature. The sensing part is fabricated by splicing single mode fiber (SMF) and hollow core fiber (HCF) via two abrupt tapered joints. Light couples to the wall of HCF due to the collapse in abrupt taper region and then modal interference occurs among multiple modes. Not only intensity but also wavelength of the dip around 1556 nm linearly responses to the curvature and temperature change thus a sensitivity matrix could be built to demodulate both curvature and temperature simultaneously. In addition, the interference dip around 1540 nm performs a decrease trend and the highest curvature sensitivity of 5.05 dB/m−1 is achieved in a wide range from 0.765 m−1 to 3.423 m−1.