An all-fibre multi-parameter sensor for composite structures based on a chirped fibre Bragg grating

Abstract

An all-fibre multi-parameter sensor for composite structures based on a chirped optical fibre Bragg grating (CFBG) has been studied theoretically and experimentally. The principle of multi-parameters sensing with a single CFBG is based on that the centre wavelength and the FWHM (full width at half maximum) in the reflection spectrum of a CFBG vary linearly with the temperature and/or the axial stress. A wavelength matched optical fibre long period grating (LPG) and another wavelength matched reference CFBG (CFBGR) have been used to interrogate the signal of the sensor CFBG (CFBGS). The temperature and strain of the composite structure have been monitored real-time with one CFBG as a single sensor head. The temperature resolution of 0.12°C and the strain resolution of 1.1μɛ for a composite structure have been realized in experiments. The experiment results agree well with the theoretical analyses.

Investigation of strain induced effect on linear shape fiber Bragg grating embedded in composite material

“…FBGs can be used for strain and temperature and other measurements such as pressure, acceleration and displacement [1][2][3]. Additionally, they can be easily suited to composite materials made of reinforced glass and carbon fiber because of their similar mechanical properties [4][5][6][7][8][9][10][11][12][13][14][15].Changes in strain affect both the effective refractive index n eff and the grating period Λ of FBG, which results in a shift in the reflected wavelength:2 ,where λ B is the Bragg wavelength and Δε is the relative strain change of FBG defined as:where Δl is the length change of FBG and l is the initial length of FBG. In order to determine the level of degradation of a composite material, a novel generation of FBGs has been used.…”