Theoretical and experimental analysis of interaction from acoustic emission on fiber Bragg grating

Fiber Bragg grating (FBG) sensors have been indicated to be ideal candidates for high frequency acoustic emission (AE) detection. This paper reports that the strain fields along FBG axis generated by acoustic emission waves contain Gaussian-sine strain field distribution. Propagation matrix method is adopted to evaluate the dynamic characteristics of FBG reflection spectrum under the action of the Gaussian-sine strain field. Then, intensity demodulation signal of FBG acoustic emission detection system using 3-dB bandwidth method is theoretically simulated based on the spectrum analysis. In order to obtain accurate measurement using this system, the maximum displacement amplitude of the strain field generated by acoustic emission is explored. Furthermore, in AE experiments, Gaussian-sine waves are extracted to confirm the accuracy of the novel presentation regarding strain field generated by acoustic emission waves along FBG axis. These studies provide useful tools for acoustic emission sources position and identification by time waveform analysis.