High-Sensitivity Temperature Sensor Based on a Selectively-Polymer-Filled Two-Core Photonic Crystal Fiber In-Line Interferometer

A highly sensitive temperature sensor based on an all-fiber Mach-Zehnder interferometer using a selectively polymer-filled two-core photonic crystal fiber is experimentally demonstrated. The sensor fiber was made by the manual gluing and subsequent infiltration of polymer; the cladding air holes surrounding one core were selectively filled with a polymer material with a high thermo-optic (TO) coefficient while leaving those of the other core unfilled, and this led to the large TO mismatch between two cores. It was found from measurements that a very high temperature sensitivity of 1.595 nm/°C could be achieved, which was more than two orders of magnitude higher than that of the sensor fiber before the selective filling process.