Temperature compensation effect of different packaged FBGs under abrupt temperature changing environment

Abstract

The temperature compensation effect of FBG sensors is crucial to their measuring accuracy. In the design of a FBG sensor, two FBGs are often adopted to subject positive and negative strains through two packaging methods including all grating pasting and two-end pasting after grating pretension. Temperature compensation of the FBG sensor is often realized by using the difference of the wavelength shift of the two FBGs as the sensing signal. In current reports, temperature compensation is performed based on the assumption that the wavelength shifts of the two FBGs are the same. However, the difference of the wavelength shift is also influenced by the packaging methods and the temperature changing environment. This work presents an experimental study on the temperature compensation effect of two pair different packaged FBGs under abrupt temperature changing environment. For each packaging method, two FBGs with same parameters are pasted on the upper and lower surfaces of an equal-strength cantilever and assembled in a shell to serve as a FBG sensor. Boiling water and ice-water mixture are used to pour on the shell to form abrupt temperature changing, whereas an adjustable thermostat provides slowly temperature changing environment. Experimental results shows that the temperature compensation effects for the two different packaging method are same(within 21pm) when slowly temperature changing slowly, however, the compensation effects are significantly degraded during abrupt temperature increasing (58 pm and 48 pm for all grating pasting and two-end pasting, respectively). The results can provide a scientific reference for the design of FBG sensors.