Highly sensitive temperature sensor based on an isopropanol-sealed optical microfiber coupler

A simple and highly sensitive temperature sensor based on an isopropanol-sealed optical microfiber coupler (OMC) is reported. Due to the high thcrmo-optic coefficient of isopropanol, the temperature sensitivity of the OMC can be effectively improved by immersing the OMC into isopropanol. The refractive index change of isopropanol is caused by the surrounding temperature variation which in turn allows highly sensitive temperature sensing. Theoretical analysis demonstrates that the temperature sensitivity increases quickly with the decreasing OMC waist diameter. Temperature sensitivities at different waist diameters exhibit high consistency with the theoretical results. When used for temperature sensing, the transmission spectrum blueshifts as the surrounding temperature increases. The highest sensitivity of -5.89 nm/degrees C is achieved at the waist diameter of 2.2 mu m. This is the most sensitive OMC based temperature sensing device reported so far. Such a compact size, low cost, and highly sensitive device may widen the application range of OMC. Published by AIP Publishing.