FIBRE-OPTIC SENSOR IN THE FORM OF A FABRY-PEROT INTERFEROMETER HAVING ONE OR BOTH REFLECTING ELEMENTS MADE AS A BRAGG GRATING

摘要

The present invention relates to a fibre-optic sensor in the form of a Fabry-Pérot interferometer having one or both beam-reflecting elements designed as a Bragg grating (BG). What especially distinguishes the invention is that the chirp function of at least one Bragg grating is balanced against one non-desired measurand, such that the shift of the centre (xr) of the reflection which is a result of the variation of the non-desired measurand exactly compensates for the optical path difference which this measurand generates in the interferometer. This can be carried out by the chirp function having the form LAMBDA 0(x) = lambda 0/2n0 (1+Ax/BL0-Cx), wherein A, B and C are constants which are determined analytically or experimentally for each different case of desired invariance.