Abstract: Lightwave diffraction device formed of a dielectric layer (4), a mirror (12) arranged at the lower face (10) of said layer, a semi-reflective structure (13) arranged at the upper face (100) of said layer, and a diffractive structure (8) arranged in said layer or on its faces. The height (H) of the layer is chosen so as to substantially satisfy the resonance condition for at least one leaky mode propagating in said layer for at least one given incident wave having a determined wavelength? and a determined incidence angle ?c. Next, the diffractive structure is arranged so that there is no propagating positive diffracted order, and so that all negative orders other than the ?1st propagating order have zero or a relatively small diffraction efficiency, the reflected ?1st order propagating in a direction non-parallel to the incident wave. This diffraction device allows a high diffraction efficiency of up to 100% for the ?1st order.

Abstract: Lightwave diffraction device formed of a dielectric layer (4), a mirror (12) arranged at the lower face (10) of said layer, a semi-reflective structure (13) arranged at the upper face (100) of said layer, and a diffractive structure (8) arranged in said layer or on its faces. The height (H) of the layer is chosen so as to substantially satisfy the resonance condition for at least one leaky mode propagating in said layer for at least one given incident wave having a determined wavelength? and a determined incidence angle ?c. Next, the diffractive structure is arranged so that there is no propagating positive diffracted order, and so that all negative orders other than the ?1st propagating order have zero or a relatively small diffraction efficiency, the reflected ?1st order propagating in a direction non-parallel to the incident wave. This diffraction device allows a high diffraction efficiency of up to 100% for the ?1st order.

Abstract: The device for measuring translation, rotation or velocity includes at least a light source, a light detector, a first grating and a second grating, the first grating being mobile relative to the second grating. A incident beam reaches the first grating where it is diffracted in two beams whose directions are interchanged by the second grating, the resulting beams being then again diffracted by the first grating in an output diffraction direction where they interfere together. Both gratings are used in reflexion.

Abstract: The device for measuring translation, rotation or velocity includes at least a light source, a light detector, a first grating and a second grating, the first grating being mobile relative to the second grating. A incident beam reaches the first grating where it is diffracted in two beams whose directions are interchanged by the second grating, the resulting beams being then again diffracted by the first grating in an output diffraction direction where they interfere together. Both gratings are used in reflexion.

Abstract: Light wave diffraction device formed of a dielectric layer (4), a reflecting structure (12) arranged on one lower face (10) of said layer, and a diffraction grating (8) arranged on one face (6) of said layer. The height (H) of the layer is selected so as to substantially satisfy the resonance condition for a leaky mode in said layer for at least one given incident wave having a wavelength &lgr; and a determined angle of incidence. Next, the diffraction grating has a spatial period selected so that the incident wave is diffracted essentially along the first negative diffraction order and at an angle of diffraction different to the angle of incidence (outside the Littrow condition). In particular, the invention provides that either the angle of incidence, or the angle of diffraction is high, i.e. relatively close to 90° from the direction perpendicular to the diffraction grating.

Abstract: The present invention relates to optical fiber measuring systems comprising a light source, a modulator for modulating the amplitude of the light signal emitted by the light source at a modulation frequency, an optical connecting fiber, a resonant cavity, a phase detector and a phase comparator. According to the invention, a sensor which is sensitive to an ambient parameter is incorporated into the cavity such that a variation in the parameter causes a variatioin in the phase of the signal at the modulation frequency. The invention can be applied to measuring systems for use in a severe environment.

Abstract: The invention relates to a fiber-optic detector and concerns more particularly a detector capable of producing microbends in an optical fiber in response to the variation of a physical quantity or of an environmental parameter. The sensor of the invention consists of an optical fiber provide with a sheath which is covered by a layer exhibiting periodic discontinuities. The sheath and its covering react to the variation of the parameter to be detected in such a manner as to produce microbends of the same periodicity as that of the discontinuities.

Abstract: The device for measuring translation, rotation or velocity includes at least a light source, a light detector, a first grating and a second grating, the first grating being mobile relative to the second grating. A incident beam reaches the first grating where it is diffracted in two beams whose directions are interchanged by the second grating, the resulting beams being then again diffracted by the first grating in an output diffraction direction where they interfere together. Both gratings are used in reflexion.