Single-Ended Optical Fiber Strain Sensor for Measuring Maximum Strain
Patent, Filed 30 Jun 1994, patented 31 Oct 1995
DEPARTMENT OF THE NAVY WASHINGTON DC
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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 reflective surface is fixed at one location on the structure, and a multi-mode optical fiber with a flat end is fixed at another location on the structure and is positioned so that its flat end is in contact with the reflective surface. A microbore capillary tube attached to the reflective surface encloses the fiber at its flat end and frictionally retains it in contact with the reflective surface. Increasing strain in the structure pulls the fiber end away from the reflective surface in proportion to the amount of strain however, when strain is decreasing, the fiber buckles rather than moving closer to the reflective surface. Therefore, the maximum strain is reflected as a maximum distance between the fiber end and the reflective surface. When the maximum strain experienced is to be measured, light is launched into the free end of the fiber and reflected back through the fiber by the reflective surface. Its intensity is then detected and measured. The intensity of light transmitted to the detector will vary inversely with the distance between the fiber end and the reflective surface therefore, this distance can be measured and correlated with strain to a high degree of accuracy.
- Test Facilities, Equipment and Methods
- Optical Detection and Detectors
- Fiber Optics and Integrated Optics