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12 April 1996 Braided intensity-based fiber sensor for civil infrastructure monitoring
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An intensity-based fiber optic senor has been studied, especially for use in long term monitoring of civil structures. The fiber tested was a braided polyimide multimode fiber. By braiding, the sensitivity of the fiber was enhanced due to the increased microbending. Two types of laboratory tests have been performed using the optical fibers. First, uniaxial tension tests of the fiber were performed on an Instron testing machine. The braided fiber's intensity loss versus applied strain (using various gauge lengths and pretension loads) was monitored and shown to be more sensitive than straight fibers with inconsequential hysteresis occurring. Next, the fiber was attached to a 3/4' diameter solid steel rod at varying gauge lengths, braids per inch, and loop diameters. The rod was placed in pure tension on a SATEC Universal Testing machine and electric strain gauges were attached to relate strain measurements to intensity readings. The braided fiber was also applied on the rod in a loop to take advantage of the macrobending. Results from these tests suggested a need for further test studies, which are ongoing, within a certain range of strain values to determine an optimum gauge length, number of braids of the fiber and required pretension loading and to check the validity of using this type of fiber sensor in civil engineering structures to monitor response continuously.
© (1996) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Ramesh B. Malla, Gregory C. Frantz, Mark Allyn Jr., and Howard A. Canistraro "Braided intensity-based fiber sensor for civil infrastructure monitoring", Proc. SPIE 2682, Laser Diodes and Applications II, (12 April 1996);

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