Abstract: The invention relates to a flexible strip (1) for a civil engineering structure, that can extend longitudinally along a longitudinal axis and comprises at least one optical fiber (20) enabling a structure to be localized and measured in terms of deformation and/or temperature, where said optical fiber (20) is essentially arranged along the longitudinal axis and is surrounded by an at least partially reinforced thermoplastic polymeric matrix of continuous reinforcement fibers (30), essentially along the longitudinal axis, and where the mass quantity of continuous reinforcement fibers extending essentially along the longitudinal axis, WCF, is higher than, or equal to, ten times the mass quantity of optical fiber(s), WOF. The invention also relates to metrology devices and associated methods.

Abstract: The invention relates to a flexible strip (1) for a civil engineering structure, that can extend longitudinally along a longitudinal axis and comprises at least one optical fibre (20) enabling a structure to be localised and measured in terms of deformation and/or temperature, where said optical fibre (20) is essentially arranged along the longitudinal axis and is surrounded by an at least partially reinforced thermoplastic polymeric matrix of continuous reinforcement fibres (30), essentially along the longitudinal axis, and where the mass quantity of continuous reinforcement fibres extending essentially along the longitudinal axis, WCF, is higher than, or equal to, ten times the mass quantity of optical fibre(s), WOF. The invention also relates to metrology devices and associated methods.

Abstract: A temperature sensor having a light fiber connecting a light source and a reflectometer. Temperature measurement zones are formed by sensing elements made of shape-memory alloy. The elements exert a stress on the fiber when they are subjected to an increase in temperature due to their memorized state. The change in temperature is detected by the reflectometer.

Abstract: A fiber-optic sensor composed of elements made of shape-memory alloy which, in one of their memorized shapes, impose a stress on the optical fiber, which stress is easy to locate with an interferometer. The multisensor configuration is thus easily reconfigurable.

Abstract: An optical fiber stress detector in which the light beam transmitted in the optical fiber which has to detect stresses is modulated in amplitude by a microwave alternating signal. The signal coming from the fiber is demodulated and then transmitted to a detector which measures the phase-shift existing between the demodulated signal and a signal derived from the modulation alternating signal. Application to the detection of stresses in any composite structures such as public constructive works, aircraft wings etc.

Abstract: A device for reading sensors in fiber optics which includes an integrated optics interferometer wherein the interference signal is slaved to a set-point value by means of a negative feedback signal. The measurement for reading the sensors is provided from the negative-feedback generated signal. In one of the disclosed embodiments generated delays of a value greater than an optical wavelength are measured by coupling the interferometer to a counting-up/counting-down system for interference fringe jumps.

Abstract: The invention is a hollow fiber with, over the full length of the fiber and between each fiber channel (3, 4) and the core, at least one stress zone (5, 6) to create an anisotropic stress distribution which subjects the fiber core to a tensile stress. The cable design is advantageous in that it is possible to control the sign of the fiber intrinsic birefringence. The cable is thus advantageous for use as a pressure sensor or pressure transducer.

Abstract: The interferometer of the invention, of the type with an optical fibre in ring form, with a measuring head (16) connected to a distant processing center (18) by cables, has an optoelectronic detector (17) removed to the center and connected to the measuring head by a multimode optical fibre (19).

Abstract: A process for producing an optical fiber comprising the following stages: a stage of production of a preform having an axis of symmetry and their ends and comprising an optical core as well as at least one cylindrical recess whose axis is parallel to the axis of symmetry of the preform; a drawing stage at a temperature making possible the softening of the drawn part of the preform to obtain a hollow optical fiber, characterized in that it comprises, after the preceding stage of production of the preform: a stage of attachment in a tight manner, to one end of the preform, of a hollow chamber whose cavity communicates with the recess of the preform. The cavity also communicates with a pneumatic regulation device. The drawing stage comprises a pneumatic regulation of the gas contained in the cavity and in the recess with the help of the pneumatic regulation device.

Abstract: The disclosed network comprises standard sensors and intrinsic sensors with optic fibers. It is optically supplied. It has a circuit for addressing the channels of sensors with active couplers, also optically supplied. Each standard sensor is associated with an integrated optic element. The outputs of the sensors are all coupled to an optic fiber return bus.

Abstract: The disclosed optical fiber sensor uses the effect of variation in the birefringence in a birefringent optical fiber as a function of the stresses and of the temperature. It has a linearly polarized, wide-spectrum source coupled to a polarizing-preserving single-mode optical fiber, along one of its neutral axes, devices capable of inducing coupling points being distributed along this fiber. A polarizer at 45.degree. with respect to the neutral axes of the fiber is placed at output of this sensor fiber. The output radiation is analyzed by spectroscopy, for example in a scanning Michelson interferometer associated with a detector. The detection by the interferometer enables the identification of the devices that are subjected to stresses. The same type of device may be used for the simultaneous detection of the stresses and/or the temperatures. The disclosed device can be applied notably to the monitoring and supervision of any installation in which strains have to be detected.

Abstract: A reading device of interferometric or polarimetric sensors including a main fiber on which a number of couplers equal to the number of sensors are placed, each coupler connected to a secondary compensation fiber, followed by a polarizer and a detector, thus constituting n elementary polarimeters.

Abstract: A reading device operates by the placing in interference of a reference signal, in the form of a fundamental wave train, with delayed wave trains constituting the useful signal. The device comprises an interferometer, a first branch (32) of which is traversed by at least said fundamental wave train (14), the first branch (32) being equipped, with means (37, 67, 87) for the generation of quantified delays of said fundamental wave train (14) with means (39) for the generation of a continuously variable delay of said fundamental wave train (14) over a range about each quantified delay value.

Abstract: The disclosure pertains to a device for the measurement, in a wide range, of a non-reciprocal phase shift generated in a ring interferometer, to a measuring method and, chiefly , to an optic fiber gyrometer. It also concerns a method of measurement, notably a method for the measurement of rotation speed. The disclosure concerns an improvement in a measuring device comprising a phase modulation device enabling the phase to be automatically locked to an interference fringe of the device. The improvement lies mainly in the fact that the light source emits, in the ring, several light frequencies so as to make it possible to remove uncertainty on the order (0, .pi., 2.pi., etc.) of the interference fringe on which the automatic control is achieved. The disclosure can be applied notably to the making of devices for the measurement of angular speeds. The disclosure can be aplied chiefly to the making of optic fiber gyrometers.

Abstract: A multiple-point temperature sensor, with optic fibers, uses the effect of variation in the birefringence in a birefringent optic fiber as a function of temperature. This sensor has a plane polarized, wide spectrum source coupled to a monomode optic fiber for preservation of polarization, along one of the neutral axes, with weak coupling points distributed along this fiber. A polarizer at 45.degree. to the neutral axes of the fiber is placed at the output of this sensing fiber. The output radiation is analyzed by spectroscopy, for example in a Michelson interferometer, capable of being swept, associated with a detector. The interferometer shifts needed to detect the extreme values of the transmission function are measurements of temperature deviations.

Abstract: Disclosed is a shift sensor with birefringent optic fiber, wherein two fixed coupling points are provided. One movable coupling point, created by a coupling means, for which it is sought to measure the shift gets shifted over the fiber. A source emits a plane polarized wave along a neutral axis of the fiber. A coupled wave train is created at each coupling point. These coupled wave trains have a propagation speed which is smaller than that of the primary wave train. A detector enables the locating of the relative positions of the coupled wave trains and, hence, of the movable coupling point with reference to the fixed coupling points.

Abstract: An optic fiber hydrophone comprises a wide spectrum optical source, a super-luminescent diode for example, associated with an optic fiber assembly comprising chiefly a side-hole optic fiber, subjected to the field of pressure, forming a sensor, transmitting the optic radiation in the slow and fast modes respectively, and a second fiber, not subjected to the field of pressure, the neutral axes of which are oriented with respect to the neutral axis of the first fiber so that the wave transmitted in slow mode in one fiber is transmitted in fast mode in the other fiber, it being possible to connect these two fibers by a polarization maintaining fiber in the event that the sensor is offset with respect to the source, a polarizing fiber enabling the creation of the interferences, and a radiation detector at the output of the fiber assembly.

Abstract: A process for the manufacture of a glass blank in the form of a rod from which the optical fibre is drawn, said blank being produced starting from a molten bath of glass. A first stage of the process comprises melting a mixture of starting materials having a higher impurity content (<10.sup.-4) in the form of so-called transition metals then the final blank (<10.sup.-7). A second stage consists in inducing separation into two solid phases (a hard phase rich in silica and a soft phase poor in silica) by drawing the blank from the bath of molten glass and by subsequently subjecting it to a thermal annealing treatment. This is followed by deep etching and by peripheral etching to eliminate the soft phase and its impurities to different extents as a function of depth, which creates a radial refractive index gradient and an optical cladding.