4 April 2012 High-speed full-spectrum interrogation of fiber Bragg grating sensor application in reducing sensor strain sensitivity
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We used high-speed full-spectrum interrogation of a Fiber Bragg Grating (FBG) sensor to measure dynamic strain in different sensor packages in real-time. In this effort we performed solenoid impact tests on a variety of sensor mounting structures made with FR4, steel, and carbon fiber composite materials. Full spectrum FBG interrogation at 40 kHz repetition rate was the key that allowed us to measure and compare dynamic strain in the structures, with measurement resolution on the sub-millisecond scale. With this interrogation method we were able to measure the full character of the dynamic strain including the strain non-uniformity and distribution manifested in peak-splitting and spectrum broadening. Results showed that the FR4 board with soft epoxy responded with a maximum dynamic strain on the order of 3000 micro-strain. Adding hard materials such as steel and graphite fiber composite reduced the strain about 7 times. However, the FR4 board mounted in a free-floating configuration using hard epoxy reduced the maximum strain to a value below the noise threshold of the full spectrum interrogation configuration. Here we proposed using edge detection method of FBG interrogation due to its increased strain sensitivity which enabled us to further analyze the critical results obtained by full spectrum interrogation. We also proposed using edge detection to measure sensor strain in real time for the purpose of filtering out the strain noise from useful signal. We will use the results and data obtained with both methods to analyze and enhance the performance of our electric field sensors in environments of high static and dynamic strain.
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Nikola Stan, Nikola Stan, Spencer Chadderdon, Spencer Chadderdon, Richard Selfridge, Richard Selfridge, Stephen Schultz, Stephen Schultz, Sean Webb, Sean Webb, Kara J. Peters, Kara J. Peters, Mohammed Zikry, Mohammed Zikry, } "High-speed full-spectrum interrogation of fiber Bragg grating sensor application in reducing sensor strain sensitivity", Proc. SPIE 8347, Nondestructive Characterization for Composite Materials, Aerospace Engineering, Civil Infrastructure, and Homeland Security 2012, 83471N (4 April 2012); doi: 10.1117/12.914751; https://doi.org/10.1117/12.914751

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