Fiber optic Fabry–Perot interferometer constructed by quartz capillary and titanium wire for temperature measurement

A novel fiber temperature sensing head based on the Fabry–Perot interference principle is proposed and fabricated. Its temperature sensing is performed by using the thermal expansion of titanium wire fixed in a quartz capillary. The rationality of ignoring high-order reflected light was verified by the experiment. The spectra of heating and cooling processes were measured for three times in the temperature range of 1 ∼ 50 °C, showing the high consistency and stability. This sensor requires only 25 nm scanning width of the optical spectrum analyzer. Its sensitivity of the Fabry–Perot cavity optical length changing with temperature is approximately −66.7 nm °C⁻¹, and the accuracy can reach 0.1 °C by utilizing the binomial empirical formula instead of the linear one. (paper)