Sapphire Fiber Fabry-Perot Interferometer for Measurement of High Temperatures

摘要

A fiber-optic sensor based on extrinsic Fabry-Perot interferometer has been developed and tested for the measurement of temperatures above 1000 ℃. Because of the high operation temperatures, quartz glass fibers are of limited use. Therefore, the suitability of single crystal sapphire fibers for this kind of sensor and for the expected environmental conditions has been investigated. To prepare a temperature sensitive Fabry-Perot interferometer, two optical sapphire fibers (an input fiber and a short reflecting fiber) were positioned and glued inside of an alumina ceramic capillary. The difference between the coefficients of thermal expansion of fiber and capillary, acting over the length of the capillary, determines the temperature sensitivity of the sensor. While the material parameters would allow temperature measurements up to 1600 ℃, the experimental results indicate ability to short-term temperature measurements up to 1100 ℃, but to long-term measur ements only up to 800 ℃.