Microcapillary-Based High-Sensitivity and Wavelength-Tunable Optical Temperature Sensor

A high-sensitivity and wavelength-tunable temperature sensor based on a short piece of fused-silica microcapillary (FSC) spliced between two single mode fibers (FSCs) and immerged in ethonal solution is proposed and experimentally investigated. Using the thermo-optic effect of ethanol and high sensitivity to refractive index of the FSC modal interference, the temperature sensitivity of the sensor immerged in ethanol solutions is significantly increased over an FSC sensor in air. Besides, the sensitivity and the feature wavelength of the interferometer can be tuned by adjusting the concentration and refractive index of the filling ethonal solution, which is important for achieving the maximum measurement range.