Abstract: A method for processing a signal from a coherent lidar comprising a periodically frequency-modulated coherent source (L), the method includes the following steps: A decomposing each modulation period indexed j into a plurality of intervals indexed i, and determining, for each interval Iij, an elementary power spectral density DSP(i,j) of the beat signal over the interval, B determining an average power spectral density over j DSP(i), C determining a lower frequency bound of the average power density DSP(i) and an upper frequency bound, D determining a distance dk(i) and a velocity of the fluid vk(i) from the lower and upper bounds.

Abstract: A distributed optical fiber sensor of dynamic stress state comprises: an optical assembly configured to generate a series of optical pulses; an optical fiber of optical length L; an optical system configured to: inject through the first end at least the series of optical pulses; receive at the level of the end at least one series of output optical pulses, arising from the input pulses after propagation and retro-propagation in the fiber; generate at least one continuous reference beam or reference optical pulses on the basis of the optical assembly or of output optical pulses; produce a series of interference zones corresponding to the interference between the reference beam or a reference pulse and a signal optical pulse arising from an output optical pulse; a holographic detector comprising: a liquid-crystal light valve, the valve disposed so that it at least partially covers the interference zones, and producing holograms on the basis of the interference zones; at least one optical detector configured to d

Abstract: This oscillator comprises: a source generating an incident optical wave at a pulsation frequency ?; an optomechanical resonator, having optical resonances at the pulsation frequency ? and mechanical resonances at a frequency f1 and generating, from the incident optical wave, emergent optical waves at the pulsation frequencies ? and ??2?f1, and an acoustic wave at frequency f1; and, a photodiode delivering a useful signal at frequency f1 from the emergent waves. This oscillator further comprises: an acoustic propagation means for propagating the acoustic wave over a distance in order to produce a delayed acoustic wave; a means for converting the delayed acoustic wave into a delay signal at the frequency f1; and, a control loop, processing the delay signal in order to obtain a control signal applied to the source.

Abstract: This oscillator comprises: a source generating an incident optical wave at a pulsation frequency ?; an optomechanical resonator, having optical resonances at the pulsation frequency ? and mechanical resonances at a frequency f1 and generating, from the incident optical wave, emergent optical waves at the pulsation frequencies ? and ??2?f1, and an acoustic wave at frequency f1; and, a photodiode delivering a useful signal at frequency f1 from the emergent waves. This oscillator further comprises: an acoustic propagation means for propagating the acoustic wave over a distance in order to produce a delayed acoustic wave; a means for converting the delayed acoustic wave into a delay signal at the frequency f1; and, a control loop, processing the delay signal in order to obtain a control signal applied to the source.

Abstract: A fiber optic sensor for detecting an excitation in proximity to a fiber optic assembly, the excitation inducing a modulation of the phase of an optical signal propagating in the fiber optic assembly, the sensor comprises: a laser assembly emitting at least one laser beam; a fiber optic assembly; an optical system configured to: inject at least one portion of the laser beam; generate at least one laser signal beam issued from the laser beam injected into and propagated in the fiber assembly; generate at least one reference beam from the laser beam or the signal beam; produce at least one interference zone corresponding to the interference between a portion of the reference beam and a portion of the interference signal beam corresponding to the interference between a portion of the reference beam and a portion of the signal beam; a digital holography assembly comprising: a liquid-crystal spatial light modulator; a video camera configured to receive the interference zone and to transcribe it electrically to the

Abstract: A distributed optical fiber sensor of dynamic stress state comprises: an optical assembly configured to generate a series of optical pulses; an optical fiber of optical length L; an optical system configured to: inject through the first end at least the series of optical pulses; receive at the level of the end at least one series of output optical pulses, arising from the input pulses after propagation and retro-propagation in the fiber; generate at least one continuous reference beam or reference optical pulses on the basis of the optical assembly or of output optical pulses; produce a series of interference zones corresponding to the interference between the reference beam or a reference pulse and a signal optical pulse arising from an output optical pulse; a holographic detector comprising: a liquid-crystal light valve, the valve disposed so that it at least partially covers the interference zones, and producing holograms on the basis of the interference zones; at least one optical detector configured to d

Abstract: A fiber optic sensor for detecting an excitation in proximity to a fiber optic assembly, the excitation inducing a modulation of the phase of an optical signal propagating in the fiber optic assembly, the sensor comprises: a laser assembly emitting at least one laser beam; a fiber optic assembly; an optical system configured to: inject at least one portion of the laser beam; generate at least one laser signal beam issued from the laser beam injected into and propagated in the fiber assembly; generate at least one reference beam from the laser beam or the signal beam; produce at least one interference zone corresponding to the interference between a portion of the reference beam and a portion of the interference signal beam corresponding to the interference between a portion of the reference beam and a portion of the signal beam; a digital holography assembly comprising: a liquid-crystal spatial light modulator; a video camera configured to receive the interference zone and to transcribe it electrically to the

Abstract: An optical fiber sensor for locating an excitation in proximity to an optical fiber assembly comprises: a laser assembly configured to emit N laser beams indexed i with N>1, of respective emission wavelength ?i, an optical fiber assembly comprising N successive sections indexed i, an optical system configured to: inject the laser beams, receive N signal beams indexed i respectively of wavelengths ?i, generate N reference beams indexed i respectively of wavelengths ?i, produce N interference areas indexed i, a holographic detector comprising: a liquid crystal light valve that at least partially covers the interference areas, and is configured to produce N holograms indexed i from, respectively, N interference areas, at least one optical detector configured to detect N output optical signals indexed I, a processing unit adapted to identify the section of the fiber assembly situated in proximity to the excitation to be located.

Abstract: An optical fiber sensor for locating an excitation in proximity to an optical fiber assembly comprises: a laser assembly configured to emit N laser beams indexed i with N>1, of respective emission wavelength ?i, an optical fiber assembly comprising N successive sections indexed i, an optical system configured to: inject the laser beams, receive N signal beams indexed i respectively of wavelengths ?i, generate N reference beams indexed i respectively of wavelengths ?i, produce N interference areas indexed i, a holographic detector comprising: a liquid crystal light valve that it at least partially covers the interference areas, and is configured to produce N holograms indexed i from, respectively, N interference areas, at least one optical detector configured to detect N output optical signals indexed I, a processing unit adapted to identify the section of the fiber assembly situated in proximity to the excitation to be located.

Abstract: Techniques for identifying images of a scene including illuminating the scene with a beam of 3 or more wavelengths, polarized according to a determined direction; simultaneously acquiring for each wavelength an image X//(?i) polarized according to said direction and an image X?(?i) polarized according to a direction perpendicular to said direction, X?(?i) being spatially distinct from X//(?i); calculating for each wavelength an intensity image which is a linear combination of X//(?i) and X?(?i), providing an intensity spectrum for each pixel; calculating for each wavelength a polarization contrast image on the basis of an intensity ratio calculated as a function of X//(?i) and of X?(?i), providing a polarization contrast spectrum for each pixel; and calculating a spectro-polarimetric contrast image of the scene, each pixel of this spectro-polarimetric contrast image calculated based on the intensity spectrum and the contrast spectrum of the pixel considered.

Abstract: The subject of the present invention is a dynamic sensor of physical quantities with optical waveguide with optically-pumped amplifier medium, which requires no interferometer or reference sensor and which makes it possible to obtain at least the same level of performance, in terms of sensitivity, as known sensors of this type, and this waveguide is linked at one end to a selective mirror, and comprises at its other end an interrogation laser, the reflection of which on the selective mirror produces a wave which, by interference with the incident wave, provokes the periodic saturation of the gain of the waveguide.

Abstract: The general field of the invention is that of fiber-optic sensors comprising at least one measurement optical fiber having an optically pumped doped amplifying medium, the optical characteristics of which are sensitive to a physical quantity, the fiber having at least one Bragg grating. The fiber is designed so as to generate, in the amplifying medium, two optical waves having different optical frequencies that propagate in the same direction after reflection on the Bragg grating and are emitted by the amplifying medium, the two optical frequencies depending on the physical quantity. The two waves may be generated using either a birefringent polarization-maintaining fiber or a DBR (Distributed Bragg Reflector) laser cavity. Notably, this sensor may be used as a hydrophone.

Abstract: Techniques for identifying images of a scene including illuminating the scene with a beam of 3 or more wavelengths, polarized according to a determined direction; simultaneously acquiring for each wavelength an image X//(?i) polarized according to said direction and an image X?(?i) polarized according to a direction perpendicular to said direction, X?(?i) being spatially distinct from X//(?i); calculating for each wavelength an intensity image which is a linear combination of X//(?i) and X?(?i), providing an intensity spectrum for each pixel; calculating for each wavelength a polarization contrast image on the basis of an intensity ratio calculated as a function of X//(?i) and of X?(?i), providing a polarization contrast spectrum for each pixel; and calculating a spectro-polarimetric contrast image of the scene, each pixel of this spectro-polarimetric contrast image calculated based on the intensity spectrum and the contrast spectrum of the pixel considered.

Abstract: A sensor is used to measure a physical quantity and includes at least: a measurement optical fiber including at least one Bragg grating; optical means designed to inject, into the fiber, a first, “pump” wave at a first optical frequency and a second, “probe” wave at a second optical frequency, the second optical frequency being different from the first optical frequency, the Bragg grating being designed to reflect the first and second optical waves, and the optical power of the first wave being sufficient to give, after interaction with the second wave reflected by stimulated Brillouin scattering, a “Stokes” wave, the frequency of which is representative of the physical quantity to be measured; and means for analyzing the difference in frequency between the two, “pump” and “Stokes”, optical waves. The sensor may notably be used as a hydrophone.

Abstract: The general field of the invention is that of fiber-optic sensors comprising at least one measurement optical fiber having an optically pumped doped amplifying medium, the optical characteristics of which are sensitive to a physical quantity, the fiber having at least one Bragg grating. The fiber is designed so as to generate, in the amplifying medium, two optical waves having different optical frequencies that propagate in the same direction after reflection on the Bragg grating and are emitted by the amplifying medium, the two optical frequencies depending on the physical quantity. The two waves may be generated using either a birefringent polarization-maintaining fiber or a DBR (Distributed Bragg Reflector) laser cavity. Notably, this sensor may be used as a hydrophone.

Abstract: The subject of the invention is a polarimetric imaging system exhibiting an optical axis, and comprising means (35) for the detection and analysis of the light backscattered by an object illuminated by a light source and at least one programmable waveplate (33), wherein the programmable waveplate comprises a material with an isotropic electrooptic tensor and a set of at least three electrodes disposed along the directions parallel to the optical axis of the imaging system.

Abstract: The subject of the present invention is a dynamic sensor of physical quantities with optical waveguide with optically-pumped amplifier medium, which requires no interferometer or reference sensor and which makes it possible to obtain at least the same level of performance, in terms of sensitivity, as known sensors of this type, and this waveguide is linked at one end to a selective mirror, and comprises at its other end an interrogation laser, the reflection of which on the selective mirror produces a wave which, by interference with the incident wave, provokes the periodic saturation of the gain of the waveguide.

Abstract: The subject of the invention is a laser comprising a semiconductor active medium with a population inversion lifetime ?c and a resonant cavity with a lifetime of the photons in the cavity ?p. The cavity includes means for being longitudinally monomode and means so that ?p>?c, such as for example a very long cavity, so as to obtain a laser with a very low intrinsic noise.

Abstract: The field of the invention is that of the detection of high frequency electromagnetic waves. The invention can be applied to a very wide range of bandwidths, but the preferred field of application is the terahertz frequency domain. The core of the detection device involves a so-called active material with an absorption coefficient in the optical domain that depends on the intensity of the terahertz signal to be detected. By measuring the variations of the absorption coefficient by means of an optical probe, the intensity of the terahertz signal is thus determined. By this means, a frequency translation is performed in a frequency domain where the measurement no longer poses technical problems. It is notably possible to improve the sensitivity of the detector by having antennas suited to the active medium, by using semiconductor or quantum well materials.

Abstract: A laser source comprises N incident laser beams, N equal to two at least, N single-mode spatial beam propagation media, each forming a propagation channel (gi) for one laser beam, a system for coherent recombination at the exit of the N channels, in order to deliver a recombined laser beam (fR) at the exit, and a phase control device (D) comprising N programmable phase-shifter elements (di) under closed-loop feedback control, one at the entry of each channel (gi). The source also comprises a polarization control device (P) comprising N programmable polarization controllers (pi) under closed-loop feedback control, one per channel, each controller being disposed between the associated phase-shifter element and channel.