This paper introduces a new type of fiber-optic acoustic emission (AE) sensor, based on a fused tapered 2x2 coupler. Laser light is injected into one input fiber and variations in the splitting ratio, caused by the passage of an ultrasonic pulse through the coupling region, are measured via a differential detection scheme. The sensor was designed to be directly compatible with an existing AE instrumentation system (the MISTRAS system from Physical Acoustics). Sensors were mounted on the surface of and embedded within glass-reinforced polyester laminates. They were excited with simulated AE signals and their performance was compared to that of a conventional piezoelectric AE transducer. The characteristics of the response of the fiber-optic sensor were similar to those of a commercial piezoelectric transducer. A signal-to noise ratio of 45 dB was achieved.
A fiber acousto-optic device is analyzed experimentally, which based on a single mode fiber coupler. The cutoff wavelength and splitting ratio in 630 nm are about 600 nm and 3 dB. When a strain wave acts on the packaged fiber coupler, the splitting ratio of the coupler will be changed which cause the modulation of output in the fiber coupler. At some frequency of strain wave, the modulation will get at Maximum.
The analysis of acoustic emission signals has been widely applied to damage detection and damage characterization in composites. Features of acoustic emission signals, such as amplitude, frequency, and counts, are usually utilized to identify the type of a damage. Recently, time-frequency distribution techniques, such as the wavelet transform and the Choi-Williams distribution, have also been applied to characterize damage. A common feature of these approaches is that the analysis is on the acoustic emission signal itself. Nevertheless, this signal is not the wave source signal as it has been modulated by the signal transfer path. Real information on damage is actually hidden behind the signal. To reveal direct information on damage, a blind deconvolution method has been developed. It is a quefrency domain method based on the cepstrum technique. With the method, acoustic emission signal is demodulated and information on the wave source can be revealed and thus damage can be identified. This paper presents preliminary test data to assess the validity of the proposed methodology as a means of identifying specific damage modes in fiber reinforced composites.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.