Experimental Study on Simultaneous Measurement of Temperature and Pressure of Seawater Based on the Reflecting Polarization Interferometer Incorporated With Bow-Tie Fiber

Detection of simultaneous measurement of temperature and pressure of seawater is very meaningful in oceanography research. To realize the goal, the reflecting polarization interferometer incorporated with the bow-tie fiber is proposed. First, the formation of birefringence in the bow-tie fiber and the working principle of the sensor are studied. Then, the temperature and pressure sensing experiments are performed, respectively. The least square method is adopted to eliminate the crosstalk influence. The best temperature and pressure sensitivities after adjustment are −1.2349 nm/°C and 1.9209 nm/MPa, respectively. The sensitivity matrix is built by extracting the information of two dips in the spectra. After comparison between the sensor demodulated results and the CTD-measured data, the correlation coefficient (
${r})$
, the mean absolute error (MAE), the mean absolute percentage error (MAPE), and the root-mean-square error (RMSE) of temperature are 0.9984, 0.3789 °C, 1.18%, and 0.4365 °C, respectively, and
${r}$
, MAE, MAPE, and RMSE of pressure are 0.9982, 0.0266 MPa, 3.18%, and 0.0308 MPa, respectively. Therefore, the method is verified to be accurate and feasible. This work could provide reference to who does oceanography research and is very prospective in the field of ocean detection.