Optical Fiber Strain Sensor for Measuring Maximum Strain

An optical fiber strain sensor is provided which remembers the maximum strain a structure has experienced in a given timeframe. A pair of multi-mode optical fibers with flat ends meet end-to-end within a microbore capillary tube with which the fibers have frictional contact. The fibers are fastened...

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Bibliographic Details
Main Authors: Bobb, Lloyd C, Krumboltz, Howard D
Format: Report
Language:English
Subjects:
FIBER OPTICS
Fiber Optics and Integrated Optics
FIBER OPTICS TRANSMISSION LINES
INTENSITY
MULTIMODE
Optical Detection and Detectors
OPTICAL DETECTORS
PAT-CL-73-800
STRAIN GAGES
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Summary:An optical fiber strain sensor is provided which remembers the maximum strain a structure has experienced in a given timeframe. A pair of multi-mode optical fibers with flat ends meet end-to-end within a microbore capillary tube with which the fibers have frictional contact. The fibers are fastened to the structure at two points a known distance apart on either side of the capillary tube. Increasing strain in the structure pulls the fiber ends apart in proportion to the amount of strain; however, when strain is decreasing, the fibers buckle rather than move closer together. Therefore, the maximum strain is reflected as a maximum distance between the fiber ends. When the maximum strain experienced is to be measured, the free end of one fiber is connected to a light source and the free end of the other fiber is connected to a detector. The intensity of light transmitted to the detector will vary inversely with the distance apart the fiber ends are; therefore, this distance can be measured and correlated with strain to a high degree of accuracy. Supersedes PAT-APPL-272 915-94.