Stabilization of high sensitivity optical fiber AE sensing for long-term detection

The optical fiber acoustic emission (AE) sensing system with high sensitivity is stabilized for long-term detection in this paper. The high linear slope window of the phase-shifted fiber Bragg grating (PS-FBG) spectrum is tracked by the tunable laser source (TLS) to maintain high AE detection sensitivity. The experimental results show that the proposed method successfully solves the problem of PS-FBG spectrum shift caused by cross sensitivity of temperature and strain. In the high linear slope window of the spectrum, the stabilized sensing system can guarantee the AE strain sensitivity of 0.63nΕ/Hz1/2 at 200 kHz under the DC voltage of 10 mV. The stability of the AE sensing system is verified by stretching a carbon fibre reinforced plastic (CFRP) sample. The practical application demonstrates that the stabilized system can accurately capture the lowest order modes in the plate wave during long-term AE detection. © 2020 Elsevier Inc.