Temperature sensor based on modes coupling effect in a liquid crystal-filled microstructured optical fiber

A temperature sensor based on modes coupling effect in a liquid crystal-filled microstructured optical fiber was proposed and studied in this paper. The sensing characteristics were investigated by using a full-vectorial finite-element method (FEM) with perfectly matched layer and scattering boundary condition. For the purpose of temperature sensing, liquid crystal E7 was designed to be infiltrated into one cladding air hole in PCF to form a defect core. As the phase matching condition is satisfied, the core modes couple to several different ordered defect core modes, and finally experience a large increase in the confinement loss spectra. Furthermore, the loss spectra shift toward opposite directions in the two temperature segments (15–29 °C, 29–50 °C) for X-polarized (X-pol) direction, while it experiences a blue shift in the temperature range of 15–50 °C for Y-polarized (Y-pol) direction. Numerical simulation results show that the sensitivity reaches −5.26 nm/°C at 30 °C. The coupling effect between the core fundamental mode and high-order defect core modes utilized in this paper will be beneficial to the high-sensitivity detection.