LOFTS: Liquid core capillary based optical fiber fluorescence temperature sensor

Optical fiber sensors are one preferred solution for temperature sensing especially for their capability of distributed measurement. However, many of them still suffer from complicated and expensive fabrication and are hardly suitable for temperature sensing in all liquid, gas and solid conditions. In order to solve these problems, we demonstrate LOFTS, a Liquid core capillary based Optical fiber Fluorescence Temperature Sensor, as a new type of fiber sensor. The temperature sensitive solution is first sealed in capillary, which is then incorporated on the tip of an optical fiber to fabricate LOFTS only relying on extremely simple fabrication operations and cost-effective materials. Combining with excitation laser and fiber spectrometer, temperature can be quantitatively measured according to fluorescence signature, yielding the same excellent linear response to temperature in all liquid, gas and solid sample sensing. Proved by various samples, the proposed LOFTS could measure temperature in high accuracy, good repeatability, stability and reproducibility, and has long conservation time for at least 3 months at 4 degrees C. This work provides an optimal optical fiber fluorescence temperature sensor in high temperature sensing performance, and more importantly, delivers a new design for simply and cost-effectively fabricated optical fiber fluorescence temperature sensors. Therefore, LOFTS can be extensively used in applications even requiring expanded temperature sensing ranges or with complicated occasions relying on different temperature sensitive solutions and capillary materials.