Sapphire Fabry–Perot interferometer for high-temperature pressure sensing

An adhesive-free encapsulation sapphire Fabry-Perot interferometer (FPI) is proposed and demonstrated for high-temperature pressure measurements. The sapphire FPI sensor is packaged by zirconia ferrules and a zirconia sleeve, which is easy to be configured and low in cost. Owing to this packaging technology, the sapphire FPI sensor presents good stability and high temperature resistance. The pressure and temperature properties of the sapphire FPI sensor are investigated within a temperature range from -50∘C to 1200°C and a pressure range from 0.4 to 4.0 MPa. Experimental results show the FPI has a temperature sensitivity of 23 pm/°C and still works as the temperature is up to 1200°C. Meanwhile, the wavelength shift of the sapphire FPI versus the applied pressure is linear at each tested temperature. The pressure sensitivity is measured to be 1.20 nm/MPa at 1200°C, and the linear response shows the proposed sensor has good repeatability within 0.4-4.0 MPa. Such a sapphire FPI sensor has potential applications in engineering areas, such as the oil industry and gas boilers.