A comparison of temperature compensation methods in a diaphragm-embedded FBG

Abstract

This paper presents the comparison of temperature compensation techniques for Fiber Bragg Grating (FBG)-based pressure sensor. Such temperature compensation is obtained through a physical assembly using a continuous FBG pair embedded in a rubber diaphragm through a vulcanization method in conjunction with different signal processing methods. The so-called continuous FBG pair is based on two consecutive FBGs (with different Bragg wavelengths) inscribed with physical separation up to 10 mm. The sensor system is tested as a function of temperature and pressure, where the temperature sensitivities of both FBGs are around 50 pm/°C. Pressure estimation errors around 148.22 Pa/°C were observed when this variation in sensitivity was not taken into account by the compensation technique. Furthermore, there is a comparison between techniques that consider the pressure sensitivity variation, namely multiple linear regression using the response of both FBGs and exponential regression using the sum of FBGs. In this case, the exponential regression indicated a smaller temperature cross-sensitivity (3.07 Pa/°C), higher determination coefficient (0.97) and smaller root mean squared error (0.40 kPa). Therefore, the exponential regression using the response of both FBGs is the suitable technique for temperature compensation when the continuous FBG pair embedded in the diaphragm assembly is considered. The results obtained in this work provide a guideline for the development of diaphragm-embedded sensors with temperature compensation and suitable for large-scale production in practical applications.