Optical pressure sensors for harsh environment

Abstract

This paper deals with the design, manufacturing, and evaluation of a new optical pressure sensor produced by using Low Temperature Co-fired Ceramic technology. This optical sensor is designed for the applications with harsh operating conditions. The sensor has to withstand temperatures up to 300 °C and work in chemically aggressive environment. Low Temperature Co-fired Ceramic is chosen for the sensor body to meet these operation conditions. This material is easy to process and easy to use for prototype manufacturing. Another important factor is the electromagnetic susceptibility of the sensor, which restricts the use of electronic pressure sensors in the application with high levels of electromagnetic interference. Therefore the optical sensing method was used for the sensor design. The paper gives a brief overview of the benefits and problems related to the optical measurement methods suitable for pressure sensor interrogation. Optical spectrum change based measurement method was chosen for the best sensor performance. Pressure transducer presented in this paper is based on the interrogation of the light spectra reflected from the Fabry-Perot optical cavity. The Fabry-Perot optical resonator is formed on the inner surface of ceramic diaphragm in the Low Temperature Co-fired Ceramic structure of the sensor body. The cavity of the resonator is between the flat end of the optical fiber and the reflective mirror layer on the diaphragm. The samples of the fiber optic sensors were calibrated by using the reference pressure gauge and the operating characteristics of the sensors are measured. The sensors were designed for various pressure ranges, samples were manufactured, measured and tested. A selected optical method for enhancing the temperature compensation and measurement accuracy is discussed. Specific interrogation unit was used for the pressure sensor measurement and evaluation.