Acoustic emission sensor system using a chirped fiber-Bragg-grating Fabry-Perot interferometer and smart feedback control.
We demonstrate a fiber-optic acoustic emission (AE) sensor system that is capable of performing AE detection, even when the sensor is experiencing large quasi-static strains. The sensor is a Fabry-Perot interferometer formed by cascaded chirped fiber-Bragg gratings (CFBGs). The reflection spectrum of the sensor features a number of narrow spectral notches equally spaced within the reflection bandwidth of the CFBG. A semiconductor laser whose wavelength can be fast tuned through current injection is used to lock the laser line to the center of a slope of a spectral notch. When the notch is knocked out of the tuning range of the laser, a neighboring notch moves into the range. Through a smart feedback control scheme, the laser is unlocked from the current spectral lock and relocked to the desired point of the new notch. The fast speed of the unlocking/relocking process (<1  ms) ensures that the AE signal is monitored without significant disruption.
Qi
Q
Zhang
Yupeng
Y
Zhu
Xiangyu
X
Luo
Guigen
G
Liu
Ming
M
Han