Abstract
Ultrasonic wave-sensing technology has been applied for the health monitoring of composite structures, using normal fiber Bragg grating (FBG) sensors with a high-speed wavelength interrogation system of arrayed waveguide grating (AWG) filters; however, researchers are required to average thousands of repeated measurements to distinguish significant signals. To resolve this bottleneck problem, this study established a signal-processing strategy that improves the signal-to-noise ratio for the one-time measured signal of ultrasonic waves, by application of parallel factor analysis (PARAFAC) technology that produces unique multiway decomposition without additional orthogonal or independent constraints. Through bandpass processing of the AWG filter and complex wavelet transforms, ultrasonic wave signals are preprocessed as time, phase, and frequency profiles, and then decomposed into a series of conceptual three-way atoms by PARAFAC. While an ultrasonic wave results in a Bragg wavelength shift, antiphase fluctuations can be observed at two adjacent AWG ports. Thereby, concentrating on antiphase features among the three-way atoms, a fitting atom can be chosen and then restored to three-way profiles as a final result. An experimental study has revealed that the final result is consistent with the conventional 1024-data averaging signal, and relative error evaluation has indicated that the signal-to-noise ratio of ultrasonic waves can be significantly improved.
Highlights
Fiber Bragg grating (FBG) sensors used in structural health monitoring have been studied extensively in terms of their long-term structural operation and safety [1,2]
The present study investigated the signal recognition of ultrasonic waveforms by application of fiber Bragg grating (FBG)
The method based on parallel factor analysis (PARAFAC) decomposition is effective in dealing with noise
Summary
Fiber Bragg grating (FBG) sensors used in structural health monitoring have been studied extensively in terms of their long-term structural operation and safety [1,2]. An FBG is a kind of distributed Bragg reflector that reflects light of a particular wavelength. Because of their small size, passive nature, immunity to electromagnetic interference, and ability to directly measure physical parameters such as temperature and strain, FBG sensors have become an important sensing technology even in harsh environments [3]. An arrayed waveguide grating (AWG) filter has been applied in a high-speed optical-wavelength interrogation system to speedily reflect wavelength shifts of the FBG and. The AWG filter has been applied as a demultiplexer to precisely interrogate wavelength shifts of multiple FBG sensors [5]
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