| 摘要 |
PROBLEM TO BE SOLVED: To measure mean deformation of a size of about 1 m meshes of a large measured body like a bridge and a tunnel by using an optical fiber grating. SOLUTION: For deformation inspection, a sensor optical fiber 2 of constant length L wherein a grating 3 is built has both its ends 4 fixed to the body 1 to be measured while extended by a constant quantity, variation in the wavelength of a reflection spectrum or transmission and absorption spectrum by the grating 3 is measured, and the extension or shrinkage between both the fixed positions of the measured body 1 is measured as a mean value of lengths L from the variation quantity.
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