11 April 2013 High dynamic range high sensitivity FBG interrogation
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We present a fiber Bragg grating (FBG) interrogation method using a micro-controller board and optical filter that achieves high strain sensitivity and high dynamic range. This interrogation method allows high sensitivity detection of ultrasonic waves superimposed on low-frequency (on the order of 100Hz) vibrations of arbitrary magnitude. One possible application is in-situ structural health monitoring of windmill blades exposed to strong winds by using FBG sensors for detection of ultrasonic waves. Interrogator operation is based on the edge filtering method using a broadband source, fiber Fabry-Perot filter and a micro-controller board which acts as a control feedback loop that locks the filter wavelength to the mid-reflection point on the FBG spectrum. Wavelength locking method allows high sensitivity for edge filtering of high-frequency waves, while the feedback signal is the measurement of low-frequency vibration with high dynamic range. The concept of the interrogator operation and different implementations are described and discussed with experimental results.
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Nikola Stan, Nikola Stan, Douglas Bailey, Douglas Bailey, Spencer Chadderdon, Spencer Chadderdon, Richard Selfridge, Richard Selfridge, Stephen M. Schultz, Stephen M. Schultz, Sean Webb, Sean Webb, Kara J. Peters, Kara J. Peters, Mohammed Zikry, Mohammed Zikry, "High dynamic range high sensitivity FBG interrogation", Proc. SPIE 8694, Nondestructive Characterization for Composite Materials, Aerospace Engineering, Civil Infrastructure, and Homeland Security 2013, 86940N (11 April 2013); doi: 10.1117/12.2009875; https://doi.org/10.1117/12.2009875

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