Abstract: An integrated optical circuit includes an optically transparent substrate including: an input face, an output face, an upper face and a lower face, the upper and lower faces extending between the input and output faces; at least one optical waveguide which includes at least one first end situated on the input face and a second end situated on the output face; and at least one optical attenuation zone able to attenuate an optical signal transmitted via the substrate to the outside of the waveguide. The waveguide has a non-rectilinear optical path between the first and second end, the attenuation zone extends from the upper face to the lower face, and is positioned on a straight line segment joining the first and second end of the optical waveguide, the waveguide and the attenuation zone having respective dimensions such that the attenuation zone does not cut the waveguide.

Abstract: An active acoustic control method for attenuating disturbing narrow-band noise with at least one counter-noise loudspeaker and at least one error microphone in a space forming a material electroacoustic system, the method implementing, in a computing element, a control law with an internal model and disturbance observer with a model of the electroacoustic system, previously obtained by an identification method. The current configuration of the electroacoustic system can vary over time, a nominal configuration of the electroacoustic system is previously determined, a corresponding nominal model Mo(q?1) or Mo(k) previously identified, the control law with an internal model and disturbance observer is implemented in real time, a modifier block ?(q?1) or ?(k) is applied to and associated with the nominal model, and the nominal model remains the same during the variations of the current configuration of the electroacoustic system, and the modifier block is varied in real time during these variations.

Abstract: An acoustic antenna includes an array of elementary submarine transducers, each elementary transducer including, between a counterweight and a horn, at least one ceramic. Each elementary transducer is mounted on a printed circuit so that the printed circuit is clamped between the ceramic and counterweight thereof. The printed circuit includes conductors for connection to electrodes of the respective ceramic for individual control of the elementary transducers. The weight of each element of the elementary transducer is set to minimize cross-talk between channels.

Abstract: An integrated optical circuit includes a substrate having an input face, an output face, a lower face and an upper face, at least one optical waveguide having a first waveguide end located on the input face of the substrate and a second waveguide end located on the output face of the substrate. The lower face of the substrate includes a first part that is planar and parallel to the upper face and an optical block, the optical block being positioned in the median plane and in the incidence plane, the optical block forming a protrusion at least at the primary reflection point of the integrated optical circuit with respect to the first planar part of the lower face and the optical block being capable of receiving and attenuating at least one non-guided optical beam propagating on the optical path of a primary reflection.

Abstract: A fiber optic interferometric measurement system includes a light source; first and second optical transmission elements; first and second Sagnac-ring interferometers, respectively, including first and second fiber optic coils, and, respectively, having lengths L1 and L2; and first and second individual integrated optical circuits, respectively, connected to the first and second optical transmission elements, and to the two ends of the first and second optic coils, respectively. The interferometric system includes a multiple integrated optical circuit integrating, on a single substrate, the first and second individual integrated optical circuits, and the difference ?l between the optical length of the first optical transmission elements and the optical length of the second optical transmission elements is higher than the maximum of ?Nb1×L1 and ?NB2×L2, in which ?Nb1 and ?Nb2, respectively, are the group birefringence index difference of the first and second fiber optic coils, respectively.

Abstract: A radiation-resistant optical fiber includes at least one core and at least one first cladding surrounding the core. The core includes a phosphosilicate matrix, the core being rare-earth doped, the rare earth being chosen from erbium, ytterbium, neodymium, thulium or erbium-ytterbium of thulium-holmium codoped and the core is cerium codoped. Also described is a method for radiation-hardening an optical fiber including the core having a phosphosilicate matrix, the core being rare-earth doped, the rare earth being chosen from erbium, ytterbium, neodymium and thulium, or erbium-ytterbium or thulium-holmium codoped, and including a step of cerium codoping the core of the fiber.

Abstract: A fibre-optic measurement device (10) includes a SAGNAC ring interferometer (20) having a proper frequency fp, a detector (14) and a modulation chain (30) generating a phase-shift modulation ?m(t) between the two counter-propagating waves (24, 25) propagating in the ring interferometer. The device aims to reduce measurement faults due to the linearity defects in the modulation chain of such a measurement device with optical fibre. For this reason, the fibre-optic measurement device reduces the amplitude of the phase-shift modulation ?m(t) which is the sum of a first biasing phase-shift modulation component ?b1(t) and a first counter-reaction phase-shift modulation component ?cr1(t), the phase-shift modulation ?m(t) falling or rising by twice the amplitude of the first biasing phase-shift modulation component ?b1(t). A rate gyro including such a measurement device and an inertial stabilization or navigation unit including at least one such rate gyro are also described.

Abstract: An interferometric system includes a polarization separation element (10), a first polarization conversion element (11), a Mach-Zehnder interferometer (2) including a first (4) and second (5) arms connected to one another by a first (6) and second (7) ends in order for a first and second beams (20, 21) having the same polarization to pass through the interferometer in a reciprocal manner in opposite directions of propagation, respectively, so as to form a first and second interferometric beam (22, 23), a second polarization conversion element (11) for obtaining an interferometric beam (24), the polarization of which is converted, a polarization-combining element (10), and a detection element (8) suitable for detecting an output beam (25).

Abstract: An integrated optical circuit includes a substrate having an input face, an output face, a lower face and an upper face, an optical waveguide extending between a first end located on the input face of the substrate and a second waveguide end located on the output face of the substrate. The integrated optical circuit further includes at least one off-center groove, the off-center groove extending from the lower face to the inside of the substrate, the at least one off-center groove being located at a non-zero distance d from the median plane, the off-center groove replacing a central groove and the at least one off-center groove being capable of attenuating the non-guided optical beam transmitted by the substrate between the first end and the second end.

Abstract: A method of calibration of a navigation and pointing system (10) including a navigation unit (11) integrally connected to a pointing device (12), the navigation unit being configured to measure the orientation of a navigation reference system (21), the pointing device (12) being configured to measure a signal in a pointing reference system (22). The calibration method includes the following steps: selecting a first planar surface (8) and a second planar surface (9); acquiring measurements via the system by directing the pointing direction towards the first planar surface (8), and respectively towards the second planar surface (9), according to a plurality of predetermined orientations; applying an algorithm for processing the measurements acquired at the previous step to extract therefrom the misalignment angles between the navigation reference system (21) and the pointing reference system (22).

Abstract: An acoustic positioning device includes an acoustic emitter and receiver. The device emits a sequence of at least one first acoustic signal (S1) and one second acoustic signal (S2), separated by a time interval T, and to receive and measure the arrival phase ?1 of S1 and the arrival phase ?2 of S2. The device measures a relative displacement between the acoustic emitter and the acoustic receiver and determines the approximate difference (R2?R1)AUX between the distance R1 traveled by S1 between the acoustic emitter and receiver, and the distance R2 traveled by S2 between the acoustic emitter and the acoustic receiver, and calculates the relative displacement (R2?R1) between the acoustic emitter and the acoustic receiver as a function of the approximate difference (R2?R1)AUX, of the time interval T and of the arrival phases ?1, ?2 respectively of S1 and of S2.

Abstract: An integrated optical circuit includes an optically transparent substrate including: an input face, an output face, an upper face and a lower face, the upper and lower faces extending between the input and output faces; at least one optical waveguide which includes at least one first end situated on the input face and a second end situated on the output face; and at least one optical attenuation zone able to attenuate an optical signal transmitted via the substrate to the outside of the waveguide. The waveguide has a non-rectilinear optical path between the first and second end, the attenuation zone extends from the upper face to the lower face, and is positioned on a straight line segment joining the first and second end of the optical waveguide, the waveguide and the attenuation zone having respective dimensions such that the attenuation zone does not cut the waveguide.

Abstract: A hybrid navigation device includes at least one auxiliary sensor adapted to deliver at least one auxiliary signal and a plurality of hybrid navigation systems, each including at least one inertial navigation system and one calculator configured to form an hybrid signal at the output of each hybrid navigation system. The hybrid navigation device includes a module for the detection of good operating condition and the weighting of the hybrid navigation systems, the module being configured to receive the at least one auxiliary signal, and the hybrid signals of each hybrid navigation system, respectively, to deduce therefrom an indicator of good operating condition and a weighting coefficient for each hybrid navigation system, and to calculate a weighted hybrid signal as a function of the hybrid signals and of the weighting coefficients of each hybrid navigation system, respectively.

Abstract: A bidirectional guided optical router includes an evanescent-field optical coupler having three input ports, three output ports, a first central waveguide, a second lateral waveguide and a third lateral waveguide and an evanescent-field-based optical coupling zone in which the first, second and third waveguides are disposed so as to allow evanescent-field-based coupling between the first central waveguide and either one of the lateral waveguides. The 3×3 optical coupler has a length L of between 3154×Leq and 2×Leq such that an optical beam coupled on the first input port having a power p and propagating on the first waveguide in the forward direction is distributed according to the following distribution: a first secondary beam having a power 90% of p/2 on the second output port, another secondary beam having a same power ?90% of p/2 on the third output port.

Abstract: Disclosed is a fiber optic interferometer including: a wideband optical source having a decoherence time ?DC; a coil including N turns of a fiber optic with length L; an optical element separating the incident beam into first and second beams coupled to first and second ends of the fiber respectively, so the first beam travels through the fiber optic in a first direction and the second beam travels through the fiber optic in a counter propagating direction; and a detector detecting the intensity of the output beam. The fiber optic is a high polarization mode dispersion type, and the length L of the fiber optic coil is more than twice the fiber correlation length, so the fiber operates in a coupled PMD mode, and the propagation differential group delay between two orthogonal polarization states, accumulated over the length of the fiber, is greater than the decoherence time of the source.

Abstract: An acoustic wave transducer includes at least one electroacoustic motor, a horn having an inner wall and an outer wall, a counterweight, and a hollow housing having an inner wall and an outer wall and at least one acoustic opening. The electroacoustic motor is connected to the horn and to the counterweight along an axis, and the electroacoustic motor is capable of exciting the horn at about at least one resonance frequency. The housing is connected to the counterweight and surrounds the motor and the horn, the outer wall of the horn being arranged opposite an acoustic opening of the housing, and the space between the inner wall of the housing and the inner wall of the horn defines a cavity that contains a fluid. The transducer includes acoustic attenuation elements connected to the outer wall of the housing in order to attenuate the emission and/or reception acoustic waves at the frequency at least in a direction transverse to the emission/reception axis.

Abstract: A method for the global acoustic positioning of the USBL or SBL type of a marine or submarine target is more accurate than the method used by known USBL or SBL systems, while applying a network of sensors having the same material dimensions as those of these known systems. The method makes use of the movements of the network of sensors to apply principles of the processings by synthetic antenna. The principle of the synthetic antenna transposed to the present problem consists in using the signals received by the hydrophones of a physical antenna placed on a moveable platform at K different moments in succession, and therefore at K locations in succession in order to provide an estimate of the position of the beacon by virtue of an antenna of virtually greater dimensions.

Abstract: A fiber Bragg grating hydrophone includes a fluid chamber (1) and an optical fiber (2) in which a Bragg grating (3) is integrated, the optical fiber extending through the fluid chamber such that the Bragg grating is positioned inside the latter. The fluid chamber is filled with a compressible fluid and is defined by a rigid casing (4) including two end surfaces (28a, 28b) that are rigidly connected to the optical fiber. At least one of the two end surfaces of the rigid casing includes an opening (5a, 5b) closed by a deformable diaphragm (6a, 6b) that is rigidly connected to the optical fiber and that can be deformed in reaction to a difference in the pressures applied to the surfaces thereof, thereby modifying the length of the optical fiber as measured by a variation in the wavelength of a luminous flux extracted from the optical fiber.

Abstract: A method and a device for suppressing noise in the passenger compartment of a vehicle, which include at least one transducer, a programmable computer, at least one acoustic sensor, the computer being configured such as to apply an electro-acoustic model of the passenger compartment to a correcting system model including a central controller with fixed coefficients joined to a block of variable coefficients, including a Youla parameter in the form of a Youla block Q. The first phase includes determining and calculating the electro-acoustic model and the control law for at least one predetermined noise frequency. In a second phase, in real time, the computer applies the control law to the electro-acoustic model in accordance with the current frequency of the noise to be suppressed.

Abstract: A Bragg grating fiber hydrophone, includes a fluid chamber and an optical fiber in which a Bragg grating is integrated, the optical fiber passing through the fluid chamber along a longitudinal axis such that the Bragg grating is positioned inside the latter. The fluid chamber is filled with a compressible fluid and is defined by a casing including two ends connected to the optical fiber. The casing includes at least one portion formed by an extensible and compressible tube extending along the longitudinal axis. The portion formed by an extensible and compressible tube includes an outer end coinciding with one of the two casing ends and can be longitudinally deformed by a difference in the pressures applied on the walls thereof, which results in a variation of the length of the optical fiber as measured by a variation in the wavelength of a luminous flux extracted from the optical fiber.