Abstract: An acoustic antenna intended to equip a sonar, the antenna being centred around a first longitudinal axis and includes at least a first assembly of at least two transducers and a second assembly of at least two transducers stacked along the longitudinal axis, each transducer having at least a radial mode having a resonance frequency, referred to as the radial frequency, and a cavity mode having a resonance frequency, referred to as the cavity frequency, wherein the transducers of the first assembly are configured to transmit sound waves in a first continuous frequency band extending at least between the cavity and radial frequencies of the transducers of the first assembly and the transducers of the second assembly are configured to transmit sound waves in a second continuous frequency band extending at least between the cavity and radial frequencies of the transducers of the second assembly, in that the cavity frequency of a transducer of the second assembly is equal to the radial frequency of a transducer o

Abstract: A holder and at least one terminal element that are configured and arranged with respect to one another so as to form a cavity of length ?L bounded axially by two walls the relative position of which with respect to each other varies in the opposite direction to the variation in ambient temperature, an increase in temperature causing the walls to move closer together and vice versa. A linear structure incorporating the device sees its length decrease when temperature increases and vice versa. Electro-optical transducers comprising a piezoelectric actuator of linear structure that acts on the length of a segment of optical fiber that forms the laser source of the transducer, and having such a device incorporated into the actuator in order to compensate, by modifying the length of the segment of fiber, for the variations in wavelength induced in the laser by the variations in temperature.

Abstract: A holder and at least one terminal element that are configured and arranged with respect to one another so as to form a cavity of length ?L bounded axially by two walls the relative position of which with respect to each other varies in the opposite direction to the variation in ambient temperature, an increase in temperature causing the walls to move closer together and vice versa. A linear structure incorporating the device sees its length decrease when temperature increases and vice versa. Electro-optical transducers comprising a piezoelectric actuator of linear structure that acts on the length of a segment of optical fiber that forms the laser source of the transducer, and having such a device incorporated into the actuator in order to compensate, by modifying the length of the segment of fiber, for the variations in wavelength induced in the laser by the variations in temperature.

Abstract: An omnidirectional antenna to equip a sonar, the antenna centered around a longitudinal axis and comprises an assembly of emission rings stacked along the longitudinal axis, each emission ring formed around the longitudinal axis. The emission rings are assembled in groups of ring, the antenna comprises at least two groups of rings and each group of rings comprises at least two rings, the inter-ring spacings between the rings of one and the same group and the inter-group spacings between two successive groups of rings chosen so as to optimize the emission bandwidth and the sound level.

Abstract: There is provided a method for manufacturing an optical-fibre sensor device, including an enclosure defining a cavity and an optical-fibre sensor including an optical-fibre and a device for holding the sensor rigidly connected to the optical fibre, the optical fibre passing through the holding device between two attachment points. The method comprises: positioning the optical-fibre sensor in the enclosure to pass the fibre through two passage openings provided on the enclosure, which defines two optical-fibre portions in the enclosure, on either side of the holding device, each fibre portion extending between one of the attachment points and one of the passage openings; holding the optical-fibre sensor in position; performing a differential elongation of the enclosure relative to the optical-fibre sensor in the longitudinal direction and towards the outside of the enclosure, the optical-fibre sensor remaining held in position; attaching the optical fibre to the enclosure at the passage openings.

Abstract: A compact omnidirectional antenna for dipping sonar comprises multiple elementary transmission rings formed around a longitudinal axis of the antenna and multiple hydrophones distributed around the longitudinal axis, the antenna intended to be dipped in water, the hydrophones separate from the elementary transmission rings, the hydrophones and the elementary transmission rings fixed in the antenna. The elementary transmission rings and the hydrophones are interlinked along one and the same height (H) measured along the longitudinal axis.

Abstract: An electro-optical transducer includes a section of optical fiber including a sensitive area conveying an optical signal representative of an elongation of the sensitive area, the section of optical fiber being taut and extending longitudinally at rest substantially along a longitudinal axis, a piezoelectric actuator including at least one piezoelectric assembly including a piezoelectric bar, the piezoelectric bar extending longitudinally at rest substantially parallel to the longitudinal axis, the piezoelectric bar being provided with a pair of electrodes between which the piezoelectric bar is intended to be supplied with electric power by way of an electrical signal delivered by a sensor, the piezoelectric bar being intended to deform essentially through expansion or contraction of said bar parallel to the longitudinal axis in response to a variation in the electrical signal and being coupled mechanically to the section of optical fiber such that this expansion or contraction of the piezoelectric bar brings

Abstract: A method for manufacturing an optical-fibre sensor device is provided, including an enclosure defining a recess and an optical-fibre sensor including an optical-fibre and a device for holding the sensor that is rigidly connected to the optical fibre, the optical fibre passing through the holding device between two attachment points provided on the holding device.

Abstract: An omnidirectional antenna to equip a sonar, the antenna centered around a longitudinal axis and comprises an assembly of emission rings stacked along the longitudinal axis, each emission ring formed around the longitudinal axis. The emission rings are assembled in groups of ring, the antenna comprises at least two groups of rings and each group of rings comprises at least two rings, the inter-ring spacings between the rings of one and the same group and the inter-group spacings between two successive groups of rings chosen so as to optimize the emission bandwidth and the sound level.

Abstract: A compact omnidirectional antenna for dipping sonar comprises multiple elementary transmission rings formed around a longitudinal axis of the antenna and multiple hydrophones distributed around the longitudinal axis, the antenna intended to be dipped in water, the hydrophones separate from the elementary transmission rings, the hydrophones and the elementary transmission rings fixed in the antenna. The elementary transmission rings and the hydrophones are interlinked along one and the same height (H) measured along the longitudinal axis.

Abstract: The invention consists of an optical hydrophone, an optical fiber element forming a laser cavity, housed in a mechanical structure which comprises an open cylindrical rigid body, defining the cavity enclosing a fluid and in which the optical fiber element is housed, and closed at its ends by two end caps which keep the optical fiber element permanently under tension, in a longitudinal rectilinear position inside the cavity. The end caps are configured in such a way that when the exterior pressure varies, they undergo a deformation giving rise to a variation in the length of the optical fiber element and that when the temperature varies, they undergo a deformation giving rise to a variation in the length of the optical fiber element which compensates for that induced on this element by the temperature variation. The mechanical structure furthermore exhibits one or more orifices allowing equilibration of the static pressures.

Abstract: The invention consists of an optical hydrophone, an optical fiber element forming a laser cavity, housed in a mechanical structure which comprises an open cylindrical rigid body, defining the cavity enclosing a fluid and in which the optical fiber element is housed, and closed at its ends by two end caps which keep the optical fiber element permanently under tension, in a longitudinal rectilinear position inside the cavity. The end caps are configured in such a way that when the exterior pressure varies, they undergo a deformation giving rise to a variation in the length of the optical fiber element and that when the temperature varies, they undergo a deformation giving rise to a variation in the length of the optical fiber element which compensates for that induced on this element by the temperature variation. The mechanical structure furthermore exhibits one or more orifices allowing equilibration of the static pressures.

Abstract: The invention relates to a process for the collective fabrication of a remotely interrogable sensor having at least one first resonator and one second resonator. Each resonator exhibits respectively a first and a second operating frequency. A first series of first resonators are fabricated. The first resonators each have a first operating frequency belonging to a first set of frequencies centered on a first central frequency. A second series of second resonators are fabricated. The second resonators each having a second operating frequency belonging to a second set of frequencies centered on a second central frequency. A series of pairings of a first resonator and of a second resonator are conducted so as to form pairs of resonators exhibiting a difference of operating frequencies which is equal to the difference of the first and second central frequencies.

Abstract: The filter includes at least one acoustic track formed on a piezoelectric substrate. At least one SAW input transducer and at least one SAW output transducer are arranged in each track. Each track has a RSPUDT structure and thus a distributed excitation. The excitation function includes sources arranged in a main lobe and a tail function including at least one tail lobe. A fine and precise approximation to the desired continuous excitation function is obtained by decreasing the excitation strength in the tail function by a factor of at least 2.

Abstract: The filter includes at least one acoustic track formed on a piezoelectric substrate. At least one SAW input transducer and at least one SAW output transducer are arranged in each track. Each track has a RSPUDT structure and thus a distributed excitation. The excitation function includes sources arranged in a main lobe and a tail function including at least one tail lobe. A fine and precise approximation to the desired continuous excitation function is obtained by decreasing the excitation strength in the tail function by a factor of at least 2.

Abstract: The invention relates to a process for the collective fabrication of a remotely interrogable sensor having at least one first resonator and one second resonator. Each resonator exhibits respectively a first and a second operating frequency. A first series of first resonators are fabricated. The first resonators each have a first operating frequency belonging to a first set of frequencies centered on a first central frequency. A second series of second resonators are fabricated. The second resonators each having a second operating frequency belonging to a second set of frequencies centered on a second central frequency. A series of pairings of a first resonator and of a second resonator are conducted so as to form pairs of resonators exhibiting a difference of operating frequencies which is equal to the difference of the first and second central frequencies.