Material features based compensation technique for the temperature effects in a polymer diaphragm-based FBG pressure sensor

Fiber Bragg grating (FBG) based sensors have been applied to measure several parameters, such as pressure, vibration, liquid level, humidity, the concentration of chemical compounds, among others. An approach to measure parameters like liquid level, pressure and vibration are to embed the FBG on a diaphragm, which is generally made of a polymeric material. Nevertheless, the mechanical properties of polymers depend on temperature variation. For this reason, a polymer diaphragm can enhance the cross-sensitivity between the strain and temperature on an FBG sensor. In order to overcome this limitation, this paper presents a compensation technique for the temperature effects on an oblong polymer diaphragm-based FBG pressure sensor. The presented technique is based on the analytical model of the sensor, which takes into account the variation of the diaphragm properties with temperature obtained through a dynamic mechanical analysis of the diaphragm material. Results show that the developed technique reduces the sensor cross-sensitivity to about 1.74 Pa/°C. Furthermore, the presented technique is compared with the direct difference between the FBG strain and temperature responses presented in reference works. The comparison shows a better performance of the technique presented in this paper with respect to the cross-sensitivity and the root mean squared error.