| 摘要 |
<p>Methods, and corresponding apparatus, for detecting the occurrence of cracks or fractures are described and claimed. The methods utilize Bragg gratings, and the occurrence of a crack is detected by detecting a change in the reflectance and/or transmittance characteristics of the Bragg grating when the crack is transmitted to it. In addition to merely detecting that a crack has occurred, the methods may also provide information on the position of the fracture along the length of the Bragg grating. This may be achieved by comparing the peak intensities and/or widths of the optical reflectance spectra of the unbroken and broken grating. In certain preferred embodiments the Bragg gratings are interrogated using the combination of a broad band source and an optical spectrum analyser, or a tunable laser source and a broad band detector.</p> |
