Simultaneous Refractive Index and Temperature Measurement Based on Mach–Zehnder Interferometer Concatenating Two Bi-Tapers and a Long-Period Grating

An all-fiber sensor for simultaneous refractive index (RI) and temperature measurement based on Mach-Zehnder interferometer (MZI) is proposed and demonstrated experimentally. The MZI consists of two bi-tapers and a long-period grating. Two dips in the interference spectrum exhibit different responses to the variations of RI and temperature, and simultaneous measurement of RI and temperature can be realized by means of sensitivity coefficient matrix. Experimental results show that the RI and temperature sensitivity for the proposed sensor are -108.16 nm/RI and 0.12 nm/°C, respectively.