Experimental Research on Temperature Sensing of Seawater Based on Three Interferometers Incorporated With Bow Tie Fiber

Three interferometers (the Sagnac sensor, the linear polarization interferometer, and the reflecting polarization interferometer) incorporated with the bow tie fiber are proposed to detect the seawater temperature. Bow tie fiber, a kind of polarization maintaining fiber, has stress induced birefringence. The three interferometers are categorized as transmission and reflection types to analyze the sensing principles. Related experiments are performed to explore the influence of the wavelength and length of the bow tie fiber on the sensitivity and free spectral range (FSR). The sensitivity and FSR both increase with the wavelength increasing. The sensitivity fluctuates in a small range and FSR decreases with the length increasing. The reflecting polarization interferometer has the bigger sensitivity of -1.19nm/& DEG;C than the other two. And it has the advantages of easy fabrication, simple operation, and good stability, so it is applicable in real ocean exploration. Our work can provide a reference to researchers who do oceanographic research.