Study on high sensitivity measurement of seawater temperature based on bow tie fiber

A high sensitivity and easily achievable measurement is proposed for temperature sensing in seawater by har-nessing the high birefringence of the bow tie fiber. The formation of the birefringence is analyzed and the Jones matrix is introduced to calculate the spectrum. The experiments based on the reflecting polarization interfer-ometer were performed and the theoretical and experimental results are highly consistent. Furthermore, the changing rules of dips are investigated. The temperature sensitivity increases when the wavelength increases or the length of the bow tie fiber increases. Free spectral range increases when the wavelength increases or the length of the bow tie fiber decreases. The biggest length applicable is 4 cm. The best sensitivity we could get is-1.27 nm/degrees C. By comparison with other types of seawater sensors, this sensor shows advantages of high sensitivity, easy fabrication, good stability and simple operation, which make it prospective in ocean exploration. This work can provide reference to researchers who do oceanography research.