Abstract: The hydrophone has an interferometer structure incorporating a measuring arm in which is provided a very long monomodal optical fibre immersed in the interaction medium in which is propagated the acoustic wave. A phase displacement is induced on the optical wave by the elastooptical effect and said wave is propagated in the fibre by the acoustic wave which creates an acoustic pressure field in the medium. A reference arm establishes a reference optical path and the phase displacement linked with the acoustic wave is detected by interferometry between the two optical waves emerging from the two arms. The optical connections between the source, the optical fibre immersed in the interaction medium, the reference arm and the detector being provided in guided optics in a compact structure.

Abstract: A semiconductor laser particularly useful for frequency multiplexing in optical telecommunications having a distributed resonator supplying from a single etched grating, two or more radiations of different wavelengths. The laser comprises a junction formed by an n-type substrate, a p-type radiation-confinement region, and a surface region, a grating being etched at the interface between the confinement region and the surface region. Useful elementary bands of the junction for the attainment of the laser effect are fixed by proton implantation in the surface region of the junction. The elementary band-type regions are convergent and form, with the perpendicular to the grooves of the grating, angles that are determined so that the spacing along the various bands has a specified value linked directly to the wavelength of the corresponding emitted radiation.

Abstract: The invention relates to a light intensity modulator controlled by a "word" of n bits and an opto-electronic digital-analog converter.The modulator comprises a two-arm interferometer in whose length there is created, by opto-electrical effect, successive phase shifts controlled respectively by control bits and whose values, when the control bits are in state 1, conform to the successive powers of 2. The total phase shift obtained thus depends directly on the analog value of the control word and the emerging intensity is modulated as a function of this word. A digital-analog converter is constructed by adding a photodetector means whose output voltage depends on the analog value of the control word.

Abstract: The invention relates to a semiconductor laser with a distributed reflector comprising a semiconductor junction, one of whose semi-transparent mirrors is a split face of the semiconductor in which is integrated a light emitting junction with epitaxial layers. The active layer of this junction is coupled to a waveguide integrated in a dielectric medium, on one face of which is engraved a grating forming a distributed reflector playing the part of the second mirror. The reflector, when functioning according the second order of counter coupling emits a diffracted wave normal to the waveguide which can easily be coupled to an optical fiber.

Abstract: The interferometric laser gyrometer according to the invention comprises a laser source, a wound monomode optical fibre an a detector, the optical coupling between the source and the two ends of the optical fibre in order that these two ends receive equal parts of the light emitted by the source contro-propagating in the fibre and the optical coupling between these two ends and the detector being effected by wave guides integrated on an electrooptical substrate at which the two ends of the fibre are rigidly coupled.

Abstract: A device for connecting a peripheral unit to an optical bus-line which comprises a substrate onto which are integrated a first optical waveguide for being inserted in the path of the bus-line, a second optical waveguide for being connected to the emitting circuit of the peripheral unit, a third optical waveguide for being connected to the receiving circuit of the peripheral unit, and three couplers for intercoupling these waveguides. A plurality of connections related to the peripheral unit are provided for controlling the couplers in order to control the emission or the reception of information on or from the bus-line.

Abstract: The invention relates to an integrated optical circuit intended to separate a plurality of optical waves of different wavelengths, comprising at least one basic cell formed of elements integrated on the same plate: a directional coupler adjusted to divide between two output branches the incident energy in one branch of the coupler; each of the output branches comprising a phase-shifter, an engraved network which reflects an optical carrier of a definite wavelength, a second phase-shifter; and a junction between the two output branches. The phase-shifters are adjusted so that the waves reflected by the networks are in phase-opposition at the input to the coupler and recombine in the fourth branch of the coupler, and so that the waves not reflected by the networks are in phase in the junction.

Abstract: The present invention relates to the read-out of a data carrier having a track along which there is transcribed an angularly modulated carrier wave. In accordance with the present invention, there is provided a system for processing the read-out signal, which uses a feedback loop correcting the duty factor of a restored rectangular waveform when its value deviates from the value 0.5.

Abstract: The invention relates to variable vergency focussing systems which enable the focussing of a light beam on an object to be maintained despite movements of the object. The invention consists in using as variable-vergency element two astigmatic elements made of electro-optical material which are arranged at 90.degree. relative to one another and are subjected to voltages variable in dependence upon the vergency to be obtained.

Abstract: A flexible record disc engraved in the form of impressions along a track located in a ring-shaped zone is protected with a second flexible disc adhering at its central portion to the non-engraved part of the record disc. In the case where read-out is carried out on a stabilizing air cushion, the air remaining between the two discs is displaced by centrifugal force, so that good conditions of optical read-out are achieved.

Abstract: The present invention relates to the protecting against scratching and fouling of a data carrier which carries a relief impression readable optically by transmission. The data carrier in accordance with the invention is protected by a transparent protective layer with substantially smooth faces, which adheres to the peaks in the relief of the impression in such a way as to prevent the troughs in said relief from being filled up.

Abstract: The present invention relates to the protection of relief impressions formed in order to store information on a data carrier which can be optically read out by transmission. The invention relates to a data carrier the relief impression in which is protected by at least one layer transparent vis-a-vis the read-out radiation. The protective layer has an index of refraction that differs from that of the data carrier, per se. Thus, a refractive boundary at the relief impression is maintained and the information encoded in the diffractive relief pattern is preserved.

Abstract: The present invention relates to data carriers intended for optical read out. The data carrier in accordance with the invention comprises: a first transparent material at the surface of which the information is recorded in the form of an embossed pattern; a partially transparent metal layer covers said embossed pattern and a second, thick transparent material is deposited upon the metal layer for protection purposes.

Abstract: The process consists in splitting the information into N groups of M bits, in recording the groups on N parallel tracks on the carrier, in the form of M holograms differentiated from each other by the pitch of the interference fringes constituent of each hologram. To this end, either a laser of variable wavelength is used, or a reference beam of variable direction. The M holograms are superimposed. At the play-back stage, a fixed coherent light beam projected onto one hologram generates NM beams of different directions. N rows of M photodiodes detect the beams and supply read-out means.

Abstract: A system for creating independent communication channels using a single optical fibre, is provided. To this end, at the transmitting end, several "laser" diodes such as that E.sub.11 (FIG. 1) supply infrared rays of a wavelength defined to within at least 50 angstrom units (in the case of suitably doped gallium arsenide diodes), to selective mirrors such as that M.sub.11 which are quasi-transparent vis-a-vis other wave lengths. These rays focussed along with those coming from other diodes, upon the entry face 11 of the fibre. At the receiving end, there is an arrangement similar to that at the transmitting end, but comprising, instead of the diodes, photodetectors. A diode and a photodetector may be exchanged in order to provide a channel operating in the reverse direction.

Abstract: A device for pressing storage substrates made of thermoplastic material. It comprises: a press having two plates, a matrix attached to one of the plates, the matrix carrying the data to be stored in said substrate, and, arranged between the plates, one rubber sheet, on polyethyleneterephtalate sheet and a metal film. The superimposition of these different materials ensuring a properly uniform pressure over the substrate.

Abstract: A cinematographic film to be reproduced by television is driven at constant speed in synchronism with the sweep cycle of one or more camera tubes each positioned to pick up images projected upon a receiving surface thereof whose luminous persistence equals at least a sweep cycle. The film is periodically transluminated, during the retrace phase of the scanning beam, by a light pulse emitted by an electroluminescent diode -- or by a cluster of such diodes operating on different wavelengths -- defining a quasi-pinpoint light source, the diode being excited by an energizing pulse whose length does not exceed the duration of a line scan of the camera tube.