29 July 2004 Acoustic emission monitoring using a multimode optical fiber sensor
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Abstract
Permanent damage in various materials and constructions often causes high-energy high-frequency acoustic waves. To detect those so called ‘acoustic emission (AE) events’, in most cases ultrasonic transducers are embedded in the structure or attached to its surface. However, for many applications where event localization is less important, an embedded low-cost multimode optical fiber sensor configured for event counting may be a better alternative due to its corrosion resistance, immunity to electromagnetic interference and light-weight. The sensing part of this intensity-modulated sensor consists of a multimode optical fiber. The sensing principle now relies on refractive index variations, microbending and mode-mode interferences by the action of the acoustic pressure wave. A photodiode is used to monitor the intensity of the optical signal and transient signal detection techniques (filtering, frame-to-frame analysis, recursive noise estimation, power detector estimator) on the photodiode output are applied to detect the events. In this work, the acoustic emission monitoring capabilities of the multimode optical fiber sensor are demonstrated with the fiber sensor embedded in the liner of a Power Data Transmission (PDT) coil to detect damage (delamination, matrix cracking and fiber breaking) while bending the coil. With the Hankel Total Least Square (HTLS) technique, it is shown that both the acoustic emission signal and optical signal can be modeled with a sum of exponentially damped complex sinusoids with common poles.
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Steve Vandenplas, Steve Vandenplas, Jean-Michel Papy, Jean-Michel Papy, Martine Wevers, Martine Wevers, Sabine Van Huffel, Sabine Van Huffel, } "Acoustic emission monitoring using a multimode optical fiber sensor", Proc. SPIE 5391, Smart Structures and Materials 2004: Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems, (29 July 2004); doi: 10.1117/12.539762; https://doi.org/10.1117/12.539762
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