Abstract

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.

© 2017 Optical Society of America

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References

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Supplementary Material (1)

NameDescription
» Visualization 1: MOV (12651 KB)      Response of fiber-optic sensor system (yellow waveform on the oscilloscope) and the reference AE sensor system (purple waveform on the oscilloscope) when a 10 Hz dynamic background strain was applied on the fiber-optic sensor.

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