Abstract: Uniaxial deformation-measuring device includes a section of optical fiber equipped with a Bragg grating aligned with the measurement axis, and a test body subjected to the deformations to be measured., this device includes the fixing points for attaching the fiber to the test body. The fixing points are separated by a distance (Lfib) having a variation (?Lfib). When the test body is stressed by the deformation, the effective length (Lce) of the test body has an elongation (?Lce). The length (Lfib) of the section of optical fiber and the effective length (Lce) of the measurement body are such that the longitudinal deformation (?Lfib/Lfib) of the section of optical fiber is strictly greater than the originating deformation (?Lce/Lce) of the test body, thus defining an amplification factor K which is strictly greater than 1 and which is equal to the quotient (?Lfib/Lfib)/(?Lce/Lce) in the first order.

Abstract: 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).

Abstract: The purpose of this invention is a device (1) for fixing a fiber (2) comprising a rigid and brittle core (24) surrounded by a mechanically deformable cladding (22), and that can be subjected to at least one mechanical stress. According to the invention, the clamping device comprises concentric jaws (4), each jaw comprising an inner surface (14) composed of a central portion (16) and two end portions (18, 20), the end portions being made so as to prolong the central portion by gradually moving away from the main axis of the device, each comprising at least one part in contact with the mechanically deformable cladding when the jaw occupies a clamped position. Use of this device for fixing an optical fiber and any optical fiber sensor, particularly a Bragg grating optical fiber sensor.

Abstract: 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).

Abstract: The purpose of this invention is a device (1) for fixing a fiber (2) comprising a rigid and brittle core (24) surrounded by a mechanically deformable cladding (22), and that can be subjected to at least one mechanical stress. According to the invention, the clamping device comprises concentric jaws (4), each jaw comprising an inner surface (14) composed of a central portion (16) and two end portions (18, 20), the end portions being made so as to prolong the central portion by gradually moving away from the main axis of the device, each comprising at least one part in contact with the mechanically deformable cladding when the jaw occupies a clamped position. Use of this device for fixing an optical fiber and any optical fiber sensor, particularly a Bragg grating optical fiber sensor.

Abstract: A device draws an optical fiber from one end of a preform melted by a furnace, an optical sensor being disposed a the exit from the furnace to measure the diameter of the optical fiber for the purpose of adjusting the tension with which the optical fiber is drawn. The sensor is surrounded by a mask in two parts joined at two pairs of edges to form a dark chamber through which the optical fiber passes. The mask protects the optical sensor from radiation from ambient light sources, especially rays emitted by the furnace, which cause localized measurement artifacts. It improves the accuracy of measurement of the diameter of the optical fiber leading, by eliminating artifacts, to a reduction in the number of times the optical fiber is cut.

Abstract: The fiber-coating apparatus comprises an injector having a tubular grid mounted between two dies between which the fiber travels on the axis of the grid, which grid filled with resin that penetrates therein via holes distributed through its wall. The wall of outside diameter dext is situated at a minimum distance from the wall of diameter Dext which surrounds it in the injector, such that the ratio Dext/dext is not less than 1.35 and the difference Dext−dext is not less than 4 millimeters. The holes through the wall have a minimum diameter of 0.50 mm and a minimum density of 0.20 holes per mm2. The height of the grid lies in the range 5 mm to 50 mm, and the difference between the outside and inside diameters of the cylindrical wall of the grid is not greater than 10 mm, with a minimum inside diameter of 5 mm.

Abstract: An installation for fabricating an optical fiber preform includes a reaction tube and an excess silica soot exhaust tube equipped internally with a screw having flat helical threads for removing the excess soot. The screw is a helix hollowed out longitudinally and the installation includes a cylinder housed within the interior passage of the helix, eccentrically disposed within this passage and bearing against the inside surface of the helix. The cylinder is rotated about its axis.