Simultaneous measurement of refractive index and temperature based on half-tapered SMS fiber structure with fringe-visibility difference demodulation method

Abstract A novel fiber-optic sensor is demonstrated based on half-tapered single-mode-multimode-single-mode fiber structure, which consists of the multimode interferometer (MMI) and Mach–Zehnder interferometer (MZI). The comprehensive experiments in terms of temperature and refractive index (RI) are performed and the immunity to varied RI is observed in MMI. Further, to enhance precision of measurement, the fringe-visibility difference (FVD) based demodulation method is proposed to quantify and eliminate the influences from the fluctuations of light source power and ambient temperature. The corrected sensitivities present high linearity (>0.99) and the detecting resolution reaches 0.072 °C and 2.89 × 10−5 RIU, respectively. With FVD, our sensor can complete simultaneous measurement of RI and temperature without the crosstalk from light source power and ambient temperature.