Seawater temperature and salinity sensing based on in-fiber Michelson-Fabry-Perrot hybrid interferometer employing frequency domain decomposition method

Abstract:

We propose an in-fiber Michelson-Fabry-Perrot (M-FP) hybrid interferometer for the simultaneous measurement of seawater temperature and salinity. The sensor head consists of two parallel hetero Fabry-Perot (FP) cavities fabricated on the end face of the twin core fiber (TCF). A fiber fusion taper is used to split and recouple the light in the two cores. In this case, the Vernier effect can be obtained which can greatly enhance the sensitivity and solve the problem of temperature cross-sensitivity. Different from the traditional demodulation method based on envelop detection, we employed frequency domain decomposition method (FDDM) to demodulate the sensing signal. The simulation results indicate that the proposed sensor has high sensitivity to salinity and temperature. Thanks to the merits of high sensitivity, ease of fabrication and small footprint, the proposed seawater temperature and salinity sensor would have potential applications in marine science, food industry and ocean ranching.