Optical Fiber Strain Sensor for Measuring Maximum Strain
Patent, filed 30 Jun 1994, patented 31 Oct 1995
NAVAL AIR WARFARE CENTER AIRCRAFT DIV PATUXENT RIVER MD
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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.
- Optical Detection and Detectors
- Fiber Optics and Integrated Optics