| 摘要 |
<p>A fibre optic interferometric strain gauge assembly includes a sensor element (1) in the form of a length of single mode optical fibre whose ends (1a) and (1b) have a peak reflectivity not exceeding 10%. This reflectivity is provided either by semi-transparent coatings on the fibre ends or by the establishment of Bragg gratings within the fibre length. A laser source (2) provides a beam which is coupled into the element (1) as one arm of an interferometer. The light reflected in the interferometer whose intensity varies depending upon the degree of strain applied to the element (1) is detected and separated out into samples corresponding to the frequency of the laser source and to twice the frequency of the laser source with the two values being processed to provide both the magnitude of strain and the direction of strain in the element (1), which are derived from the ratio of intensity values for the two frequency components.</p> |
