Abstract: A measuring system includes a detector having an optical waveguide including a primary dopant capable of transmuting, by neutron capture, into a stable secondary dopant that is less neutron-absorbent than the primary dopant, a moderation layer suitable for slowing down fast neutrons, and an analysis device connected to the detector. The analysis device is configured to inject, into the waveguide, an interrogation wave having a wavelength corresponding to an absorption peak of the secondary dopant, detect a response wave emitted by the waveguide, calculate, from the detected response wave, a piece of information relating to a concentration of secondary dopant in the waveguide, and, based on the information relating to the calculated concentration of secondary dopant, determine a fluence of fast neutrons during a predetermined secondary period.

Abstract: A signal-distributing device that includes an arrayed-waveguide-grating demultiplexer and at least one receiving module. Each receiving module includes a multimode interference coupler and two output waveguides, the multimode interference coupler being located between the arrayed-waveguide-grating demultiplexer and the two output waveguides. The multimode interference coupler is configured to distribute, to the two output waveguides, an optical signal delivered by the arrayed-waveguide-grating demultiplexer. Such a device allows wavelength shifts in the signal delivered by a set of one or more sensors, in particular Bragg grating reflectors inscribed in a given optical fibre, to be measured. It allows a wavelength shift to be measured with a high linearity and a signal-to-noise ratio.

Abstract: An optical fibre, for use in the field of distributed measurement of temperature or deformation by optical reflectometry in the frequency domain using the Rayleigh backscattered signal in the fibre, includes a core doped with nanoparticles for example formed from gold particles covered with zirconium oxide, and can be subjected to high temperatures during the measurement. A method for producing the optical fibre includes a step of heat treatment during which the optical fibre is subjected, for a duration of at least one hour, to a heat treatment temperature higher than a maximum temperature to which it will be subjected during a measurement.

Abstract: The field of integrated health monitoring using Bragg grating optical fibre sensors including a sensor and methods for locating and installing this sensor on a support. The Bragg grating optical fibre sensor includes an optical fibre wherein at least one set of patterns forming a Bragg grating is written, the optical fibre further including a set of microstructures in the vicinity of each Bragg grating, the microstructures being separate from the patterns forming the Bragg grating, each microstructure being capable of scattering a portion of a light beam within a predetermined range of scattering wavelengths.

Abstract: A Bragg grating optical fiber sensor for measuring temperatures and deformations and a method for manufacturing same, the manufacturing method including ablating a mechanical coating over a portion of an optical fiber so as to form an opening extending radially over the entire thickness of the mechanical coating, and inscribing a Bragg grating into the optical fiber through the opening.

Abstract: An erosion sensor includes one or more optical fibres each having one or more cores and an optical sheath surrounding the one or more cores, a variable pitch measurement Bragg grating inscribed in one of the cores of one of the optical fibres over a measurement section to be eroded, and one or more reference Bragg gratings each inscribed in one of the cores. The reference Bragg grating is used to correct the physical length of the measurement section determined from the width of the spectrum reflected by the measurement Bragg grating, taking into account the thermomechanical parameters imposed on the erosion sensor.

Abstract: The invention relates to a device and method for detecting an acoustic wave propagating toward a membrane, the membrane carrying a waveguide comprising an optical cavity defining a resonant frequency. Under the effect of a vibration of the membrane, the resonance frequency of the optical cavity varies. The device includes a light source for directing a light wave into the optical cavity, and a servo circuit for servo-controlling the wavelength of the light wave to the resonant wavelength of the optical cavity. Monitoring the variation in the wavelength of the light wave allows an amplitude of the acoustic wave to be estimated.

Abstract: A measuring system includes a detector having an optical waveguide including a primary dopant capable of transmuting, by neutron capture, into a stable secondary dopant that is less neutron-absorbent than the primary dopant, a moderation layer suitable for slowing down fast neutrons, and an analysis device connected to the detector. The analysis device is configured to inject, into the waveguide, an interrogation wave having a wavelength corresponding to an absorption peak of the secondary dopant, detect a response wave emitted by the waveguide, calculate, from the detected response wave, a piece of information relating to a concentration of secondary dopant in the waveguide, and, based on the information relating to the calculated concentration of secondary dopant, determine a fluence of fast neutrons during a predetermined secondary period.

Abstract: The invention is a device and method for detecting an analyte in a medium. An exciting light source produces an exciting light wave, which propagates to the medium and heats the latter. The device comprises a transducer for detecting the heating of the medium. According to one embodiment, the transducer is a thermal transducer, configured to detect a variation in the temperature of the medium. According to another embodiment, the transducer is an acoustic transducer, configured to detect a photoacoustic wave propagating from the medium. Whatever the embodiment, the transducer employs a membrane, on which a waveguide is placed. The waveguide comprises a resonant optical cavity. Transduction is achieved by analyzing a variation in a resonant wavelength of the optical cavity.

Abstract: A signal-distributing device that includes an arrayed-waveguide-grating demultiplexer and at least one receiving module. Each receiving module includes a multimode interference coupler and two output waveguides, the multimode interference coupler being located between the arrayed-waveguide-grating demultiplexer and the two output waveguides. The multimode interference coupler is configured to distribute, to the two output waveguides, an optical signal delivered by the arrayed-waveguide-grating demultiplexer. Such a device allows wavelength shifts in the signal delivered by a set of one or more sensors, in particular Bragg grating reflectors inscribed in a given optical fibre, to be measured. It allows a wavelength shift to be measured with a high linearity and a signal-to-noise ratio.

Abstract: A Bragg grating temperature sensor includes an optical fiber including a core, an optical cladding surrounding the core and a Bragg grating incorporated in the core and extending along a sensitive segment of the optical fiber. The core of the temperature sensor includes a core gap extending along a core gap segment of the optical fiber, the core gap segment being located in the vicinity of the sensitive segment. The optical cladding includes a cladding gap extending along a cladding gap segment of the optical fiber, the cladding gap segment including the sensitive segment.

Abstract: A Bragg grating optical fiber sensor for measuring temperatures and deformations and a method for manufacturing same, the manufacturing method including ablating a mechanical coating over a portion of an optical fiber so as to form an opening extending radially over the entire thickness of the mechanical coating, and inscribing a Bragg grating into the optical fiber through the opening.

Abstract: The field of integrated health monitoring using Bragg grating optical fibre sensors including a sensor and methods for locating and installing this sensor on a support. The Bragg grating optical fibre sensor includes an optical fibre wherein at least one set of patterns forming a Bragg grating is written, the optical fibre further including a set of microstructures in the vicinity of each Bragg grating, the microstructures being separate from the patterns forming the Bragg grating, each microstructure being capable of scattering a portion of a light beam within a predetermined range of scattering wavelengths.

Abstract: An optical fibre, for use in the field of distributed measurement of temperature or deformation by optical reflectometry in the frequency domain using the Rayleigh backscattered signal in the fibre, includes a core doped with nanoparticles for example formed from gold particles covered with zirconium oxide, and can be subjected to high temperatures during the measurement. A method for producing the optical fibre includes a step of heat treatment during which the optical fibre is subjected, for a duration of at least one hour, to a heat treatment temperature higher than a maximum temperature to which it will be subjected during a measurement.

Abstract: The invention involves a sensor (100) with a Bragg network fiber including a source (105) and detection system (101), operating at a wavelength of a given study, in addition to a Bragg (6) network fiber (1) linked to said source and said system, with said fiber being a microstructured optic fiber whose sheath (5) includes channels (3) adjacent to the heart (2) of the fiber (1), capable of receiving a product to be analyzed, characterized in that the number of channels (3) adjacent to the heart (2) is between 2 and 5, and that the size of the heart (2) of the fiber (1) is adapted so that an electromagnetic field of a wave guided by the fiber is not confined in the heart (2) of the fiber (1), and the electromagnetic field extends into the channels (3).

Abstract: This refractometer includes at least one optical waveguide (2) comprising at least one slanted Bragg grating (4), formed in a part of the waveguide, which is placed in contact with the medium (7) of which the refraction index is to be determined, a light source (10) coupled to the waveguide in order to send this light there and have it interact with the grating, means (17) for measuring the optical power of the light diffracted to the radiation-mode continuum, when the light transmitted by the source interacts with the grating, and electronic processing means (22) for supplying the value of the refraction index of the medium based on this optical power.

Abstract: A refractometer with blazed Bragg gratings. In order to measure the refractive index of a medium, for example a liquid or a gas, the refractometer includes a waveguide having a blazed Bragg grating, the spectral response of which depends on the refractive index of the medium and a light source in order to make this light interact with the grating. Further, spectral analysis of the light which has interacted with the grating is performed, the spectrum provided by the spectral analysis is recovered, and, from the recovered spectrum, the spectral response of the grating is correlated with one value of the refractive index of the medium.

Abstract: In order to measure the refractive index of a medium (18), for example a liquid or a gas, this system comprises a waveguide (14) having a blazed Bragg grating (16), the spectral response of which depends on the refractive index of the medium, a light source (20) in order to make this light interact with the grating, means (22) for the spectral analysis of the light which has interacted with the grating, means (24) for recovering the spectrum provided by the spectral analysis means and means (26) to correlate, from the recovered spectrum, the spectral response of the grating with one value of the refractive index of the medium.