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Ultrasonic Sensitivity of Strain-Insensitive Fiber Bragg Grating Sensors and Evaluation of Ultrasound-Induced Strain
National Institute of Advanced Industrial Science & Technology/AIST Tsukuba Central 2, Tsukuba, 305-8568, Japan
Department of Mechanical Engineering, Faculty of Science and Technology, Tokyo University of Science/2641 Yamazaki, Noda, 278-8510, Japan
* Author to whom correspondence should be addressed.
Received: 19 October 2010; in revised form: 22 November 2010 / Accepted: 26 November 2010 / Published: 8 December 2010
Abstract: In conventional ultrasound detection in structures, a fiber Bragg grating (FBG) is glued on or embedded in the structure. However, application of strain to the structure can influence the sensitivity of the FBG toward ultrasound and can prevent its effective detection. An FBG can work as a strain-insensitive ultrasound sensor when it is not directly glued to the monitored structure, but is instead applied to a small thin plate to form a mobile sensor. Another possible configuration is to affix an FBG-inscribed optical fiber without the grating section attached to the monitored structure. In the present study, sensitivity to ultrasound propagated through an aluminum plate was compared for a strain-insensitive FBG sensor and an FBG sensor installed in a conventional manner. Strains induced by ultrasound from a piezoelectric transducer and by quasi-acoustic emission of a pencil lead break were also quantitatively evaluated from the response amplitude of the FBG sensor. Experimental results showed that the reduction in the signal-to-noise ratio for ultrasound detection with strain-insensitive FBG sensors, relative to traditionally-installed FBG sensors, was only 6 dB, and the ultrasound-induced strain varied within a range of sub-micron strains.
Keywords: fiber Bragg grating; ultrasonic sensitivity; strain; ultrasound detection
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Tsuda, H.; Kumakura, K.; Ogihara, S. Ultrasonic Sensitivity of Strain-Insensitive Fiber Bragg Grating Sensors and Evaluation of Ultrasound-Induced Strain. Sensors 2010, 10, 11248-11258.
Tsuda H, Kumakura K, Ogihara S. Ultrasonic Sensitivity of Strain-Insensitive Fiber Bragg Grating Sensors and Evaluation of Ultrasound-Induced Strain. Sensors. 2010; 10(12):11248-11258.
Tsuda, Hiroshi; Kumakura, Kenji; Ogihara, Shinji. 2010. "Ultrasonic Sensitivity of Strain-Insensitive Fiber Bragg Grating Sensors and Evaluation of Ultrasound-Induced Strain." Sensors 10, no. 12: 11248-11258.