Patent attributes
The present invention relates to a temperature-compensated optical fiber pressure detector for detecting pressure variations in at least one medium in relation to a reference medium such as the atmosphere or a medium where a back pressure prevails. The detector essentially comprises a deformable element (2) such as a bellows (5) exposed on one side to the reference medium and on the opposite side to the pressure to be measured, an optical fiber portion (F1) including at least one optical grating such as a Bragg grating (B1), which is connected on one side to deformable element (2) and on the opposite side to a fixed point. The optical fiber portion is subjected to a prestress by a device (6, 15, 20, 21) and its elongation varies with the displacements of the deformable element. The device applies the prestress to optical fiber portion (F1) between deformable element (2) and another fixed element (15) isolated from the medium by a rigid housing (1). An optical system (25) detects the deformations undergone by said optical grating in response to the pressure variations undergone by the deformable element. Another part (F2) of the optical fiber that is not subjected to stresses (or another non-stressed fiber portion connected to the first one) preferably comprises another similar optical grating (B2) also allowing measurement of the temperature variations. By duplicating the deformable elements and possibly the stress applying device (3), differential pressure variations can also be measured. Such a detector can notably be applied to pressure and temperature measurements in wells where difficult conditions prevail.
