Abstract: According to the present invention, a preform (7) for an optical fiber is made from a tube having a substrate layer (16) of fluorine-doped silica and a support layer (18) of non-doped silica. A cladding layer (8) of fluorine-doped silica and a core layer (10) of non-doped silica are formed on the inside surface of the tube by chemical vapor phase deposition. The optical fiber is subsequently obtained by collapsing the tube and drawing it. The invention is applicable to fabricating optical fibers.

Abstract: The invention concerns a gaseous flux laser device. To enable the removal into the atmosphere of the exhaust gases of an N.sub.2 -CO.sub.2 laser while maintaining a sufficiently low pressure in the zone where the stimulated light emission occurs, the carbon dioxide is injected through supersonic nozzles and an exhaust tube having a sufficient length is used. Application to the generating of powerful coherent light beams.

Abstract: A signal generator generates a temporal signal with a periodic configuration defined by an arrangement of seed patterns resulting from a branching construction iteratively using laws for composing several patterns and consisting in defining the periodic configuration of the signal as a component "a.sub.n " of the nth term Un with several components (a.sub.n, b.sub.n) of a recurrent sequence defined at the level of each of its components by a specific recurrent composition law, the initial term U0 having for its components the seed patterns (a.sub.0, b.sub.0). The temporal signals known as "fractal" signals result from a branching construction of this kind. The generator comprises a microprocessor (10) associated with a keyboard-display system (11), a read-only memory (12) for programs, a random access memory (13) and an output digital-to-analog converter (14).

Abstract: The core (2) of a monomode fiber is surrounded by a slightly monomode annular waveguide (6) guiding masking light having the same wavelength as the light conveyed by the core. The invention is particularly suitable for telecommunications.

Abstract: The temporal signal generated has a periodic configuration defined by an arrangement of seed patterns resulting from a branching construction employing n successive applications of m pattern type laws each defined by a specific arrangement of p pattern types. This construction amounts to defining a periodic signal configuration as a component "an" of the nth term Un with several components (an, bn) of a recurrent sequence defined at the level of its components by a particular recurrent composition law, the initial term UO having for its components the seed patterns (aO, bO). The temporal signals known by the name "fractal" result from a branching construction of this kind.

Abstract: An erbium-doped fiber laser amplifier (1), characterized by the fact that said fiber (3) is doped to a concentration lying in the range 5 ppm to 50 ppm, that the length of said fiber lies in the range 250 m to 30 m depending on the selected concentration of doping, and that the radial position of the doped zone substantially coincides with the energy maximum of the set of propagation modes in said fiber at the pumping wavelength.

Abstract: A mist is formed by an ultrasonic generator (5) from a liquid solution containing a dopant, and the mist is inserted into the tube blank to be doped (4) by means of a flexible pipe (2) in order to deposit microdrops on the inside surface of said tube blank. The flexible pipe is withdrawn progressively so that deposition takes place along the entire length of the tube blank. The deposit is dried and a new layer of glass is deposited thereon. The dopant from the deposit is heat diffused into the glass of the tube blank and of the new layer of glass. The invention is particularly applicable to fabricaitng rare-earth-doped silica preforms for the purpose of drawing optical fibers that can be used to constitute lasers or sensors.

Abstract: A laser diode (4) emits a beam which is reflected by a plane mirror (12) and by a spherical focusing mirror (2) in order to form a beam (40) which is focused on a read window which is a segment of a read line (6). Said line extends transversely relative to a film (16) running over a drum (20) which rotates about an axis (22). The window occupies the width of the soundtrack on the film. The light passing through said soundtrack is received by a photo cell (34) which provides the sound signal. The invention is particularly applicable to sound motion pictures.

Abstract: The method is intended to provide cables (10) having an optical fiber (1) and suitable for mechanically severe environments, while remaining small in section. Heretofore, the mechanical strength of optical fiber cables has been obtained by plastic structures of considerable cross-sectional area and reinforced by metal strands or by glass fibers. In the method of the present invention, the reinforcing is obtained by metal composites (3) having very high mechanical strength and very small diameter, said composites extending parallel to the fiber (1).

Abstract: Rotating membrane tangential filtration apparatus with low power consumption is characterized by a direct drive system (10) along the axis of its membrane (5), a sealing system (11, 16) between the residue and filtrate compartments, which system used frictional ceramic parts; the diameter of the filter membrane is small relative to its length, and the filter layer is arranged on its outside surface; it is provided with a system for taking up the slack caused by differential expansion.

Abstract: An active gas based on CO.sub.2 penetrates under pressure into a discharge chamber (20) via injection orifices (10) formed through the upstream face of said chamber. These orifices leave considerable solid portions (22) about themselves in said face such that the gas forms jets which diverge up to an outlet grid (12) constituting a common anode. Cathodes (8) are individually powered by a block (14) and give rise to discharges which are widened on the edges of said jets by large-amplitude gas recirculation currents, thereby increasing the electrical power injected. The invention is particularly applicable to power lasers.

Abstract: In order to manufacture a fiber by drawing a preform, said preform is made by collapsing a thick-walled silica tube having a reduced pressure established therein and heated in successive passes. The tube is prevented from ovalizing by beginning each pass with a portion bearing against a coaxial internal conical guide. The invention is applicable to low cost fiber manufacture.

Abstract: The antenna includes at least one group of antenna elements (EA1, EA2, . . . , EAp). Microwaves emitted by a central emitter (EH) reach a particular element (EA1 for example) by passing through a controllable phase shifter (VE1), a laser (LE1) which modulates a carrier light signal at a frequency specific to said antenna element with the microwaves, via an optical deflector (FIE) which injects said light signal into an optical waveguide (GE) which is common to all of the antenna elements in the group, via an optical deflector (FPE) which directs said light signal to a detector which is specific to said antenna element (EA1), and which reconstitutes the microwaves, and via a microwave amplifier (AE1) which applies the microwaves to said antenna element. The system is applicable to telecommunications and to radar.

Abstract: Twenty temperature sensors follow one another along a measurement fiber. Each successively reflects a small fraction of the energy of an interrogation light pulse running along said fiber, with the value of the fraction being indicative of temperature. To do this, each sensor is constitutred by a gap between two successive lengths (F2, F3) of an optical fiber, said gap being filled with a transparent glue (36) whose refractive index varies as a fuction of temperature. The interrogation pulse is returned solely by the optical surface constituted by the end face (38) of the upstream length (F2) of the fiber.

Abstract: Gaseous flux laser generator of the nitrogen and carbon dioxyde type. The dimensions of the enclosure and the conditions of injection of the nitrogen and those of the electrical supply are chosen to set up a luminescent discharge in a swirling flow.

Abstract: A superconducting mixed valence copper oxide, having a formula of the type:(La.sub.2-x (Y.sub.x" Bi.sub.1-x").sub.x' Sr.sub.x-x').sub.1-e CuO.sub.4-y,where:0.ltoreq.x<0.30.ltoreq.x'.ltoreq.0.2 with x'<x0.ltoreq.x".ltoreq.10<y.ltoreq.0.10.ltoreq.e.ltoreq.0.005.

Abstract: A multidielectric mirror, in particular for the mid infrared, in which the last optical layer of a multidielectric stack is constituted by a composite layer including a thin protective surface layer of a material of amorphous structure together with a high index and very low absorption dielectric layer, with the thicknesses of these two layers being designed to obtain maximum reflectance given the indices of these materials. The protective layer is preferably made of amorphous hydrogenated silicon. The invention is applicable, in particular, to making carbon dioxide power lasers.

Abstract: A carbon dioxide laser (4) directs a beam (6) onto a ceramic workpiece to be treated (18), which workpiece moves along arrow (20). A carrier gas injector (14) injects a moderate throughput of spheroidized powder of a ceramic material into said beam. After melting and solidifying, the layer (24) after has microcracks which are smaller than they would have been if there had been no projected powder. The method is applicable to the construction of heat engines.

Abstract: The invention relates to a method and to apparatus for remotely measuring the distribution of a physico-chemical parameter in a medium. The method consists in exciting measurement points (20) situated in a medium (17) in succession via an optical fiber (18), with each point (20) being excited by two light pulses of different wavelengths offset from each other in time occurring simultaneously at said point, each measurement point returning radiation at a third wavelength representative of the temperature of the measurement point. The apparatus includes two lasers (3, 4) emitting different wavelengths, a delay circuit (5) for delaying the light pulse from one (4) of the two lasers, and the measurement points include a material sensitive to biphotonic excitation.

Abstract: The system comprises subscriber stations (1, 2) each comprising a semiconductor laser generator (4) provided with means (3, 5) for modulating its laser output by means of transmit signals and a heterodyned detection system consisting of a photoelectric receiver (15) optically coupled to a local oscillator (17), an exchange (32) comprising a computer (37) and dual cavity semiconductor laser transmitters (39) connected to the outputs (38) of the computer, a passive optical distributor (31), and optical fibers (16, 8) connecting the lasers (4) and receivers (15) of each station with the optical distributor (31), on the one hand, and the lasers (4) of each station to the exchange (32), on the other hand, the computer assigning an optical frequency for each requested call and the laser transmitters of the exchange being operable to lock the transmit optical frequency of the calling and the called station lasers (4, 104), via optical fiber lines (8), on the frequency assigned by the computer.