Polarization-maintaining fiber sensor for simultaneous measurement of the temperature and refractive index

A polarization-maintaining fiber (PMF) sensor for simultaneous measurement of the temperature and refractive index (RI) based on the Mach–Zehnder interferometer is proposed and demonstrated experimentally. This fiber sensor is constructed by sandwiching a 20-mm waist-enlarged PMF between two single-mode fibers (SMFs). Using the wavelength shifts of different interference dips and the sensitivity matrix, two external parameters can be measured simultaneously. Experiment results show that the sensitivities to the temperature are 145.6 pm/°C and 0.1256 nm/°C and the sensitivities to the RI are −35.0502 and −23.3694 nm/RIU for two interference dips, respectively. This fiber sensor is simple and easy to fabricate, has high sensitivity, and can be applied to other fields, such as biological and chemical sensings.