Thomson-csf

Marc Turpin

Herve Lefevre

Jean Chazelas

Jean-Pierre Le Pesant

Philippe Refregier

Dominique Rojas

Philippe Bonniau

Serge Botti

Jean-Michel Vignolle

Michel Faure

Didier Rolly

Michele Brevignon

Marie-Noelle Charasse

Arnaud De Panafieu

Christiane Baylac

Marie-Noel Charasse

Yves Nemaud

Jean-Pierre Bettini

Reconfigurable multipoint temperature sensor

Reconfigurable birefringent fiber-optic sensor with shape-memory alloy

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.

Optical fiber stress detector using amplitude modulation

Fibre optic sensor array reading device

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.

Optical fiber sensor and a manufacturing process for making same

Electromagnetic disturbance free ring interferometer

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.

Process and device for producing a hollow optical fiber

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.

Network of sensors connected to a remote supply, monitoring and

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.

Optical fiber sensor

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.

Reading device of polarimetric and interferometric sensors

Device for reading by optical sensor coherence

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.

Measuring device for the measurement, in a wide range, of a

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.

Multiple-point temperature sensor using optic fibers

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.

Shift sensor with optic fiber

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.

Growing community of inventors

Bures Sur Yvette, France

Marc Turpin