21 September 1994 Crack detection using multimode fiber optical time domain reflectometry
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Results of measurements of longitudinal and transverse crack growth using multimode fiber optical time domain reflectometry are presented. Crack detection thresholds less than 0.1 millimeter are readily achieved with OTDR. A sensor package design has been developed to provide controllable directional response characteristics. In particular, a method to eliminate the orientation angle problem and yield omnidirectional sensor response characteristics has been discovered. Results are reported on a novel all-fiber sensor capable of sensing 10 micrometers crack displacements while surviving and sensing 150% strains and displacements of 6 mm. Transmission measurements of the sensor using white light are also reported. The method is suitable for distributed sensing applications covering large areas of structures and adaptable to response enhancements required for real time structural monitoring at rates on the order of hundreds of Hertz. Applications include bridges, buildings, main-steam pipelines, and offshore platforms.
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Keith H. Wanser, Keith H. Wanser, Karl F. Voss, Karl F. Voss, "Crack detection using multimode fiber optical time domain reflectometry", Proc. SPIE 2294, Distributed and Multiplexed Fiber Optic Sensors IV, (21 September 1994); doi: 10.1117/12.187399; https://doi.org/10.1117/12.187399

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