Temperature sensor based on liquid-filled negative curvature optical fibers

Abstract

We computationally investigate a novel temperature sensor that uses liquid-filled negative curvature optical fibers. Both the core and cladding tubes are infiltrated with a liquid that has a temperature-sensitive refractive index. The high-loss resonant wavelengths are sensitive to the liquid’s change of the refractive index. The refractive index of the liquid decreases and the resonant wavelengths increase when the temperature increases. The temperature sensitivity is 1.1 nm/ ◦C as the temperature changes from 15 ◦C to 35 ◦C using negative curvature optical fibers that are filled with liquid that has a refractive index of 1.36. The temperature sensitivity rises from 0.82 nm/ ◦C to 2.48 nm/ ◦C when different liquids are used with a refractive index from 1.30 to 1.42, and we use the third resonant peak in the fiber. The temperature sensitivity can be increased by 38% by using the second resonant peak. An analytical formula for the temperature sensitivity is derived, which can give an accurate prediction for the temperature sensitivity of this sensor. The relatively large size of the air core and cladding tubes, on the order of 10 µm, should make the infiltration procedure easier compared to other photonic crystal fibers with smaller holes. With temperature sensors based on liquid-filled negative curvature optical fibers, there is no need for any special post-processing, such as the liquid filling of selected air holes or inscription of fiber gratings.