Abstract: A method of improving the symmetry of a cylindrical silica tube to be used in making a preform having a circular outside surface eccentric to a circular inside surface thereby providing a varying tube thickness throughout the circumference of the tube which includes the following steps. The first step is locating a longitudinal generator line of the cylindrical tube at a greatest thickness of the tube at a given circumferential point on the tube, and while preventing the tube from rotating, etching in at least one pass the inside of the tube with a gas capable of decomposing silica, while heating the outside of the tube along that longitudinal generator line.

Abstract: A method and apparatus for analyzing ions by determining times of flight include establishing an encoded sequence for launching packets of ions from a source region toward a detector. The encoded sequence is one in which the high-mass ions of a leading packet will be passed by the low-mass ions of a trailing packet. Thus, a high efficiency time-of-flight mass spectrometer is formed. The ions of each packet are acted upon to bunch the ions of the packet, thereby compensating for initial space and/or velocity distributions of ions in the launching of the packet. The times of arrival of the ions are determined at the detector to obtain a signal of overlapping spectra corresponding to the overlapping launched packets. A correlation between the overlapping spectra and the encoded launch sequence is employed to derive a single non-overlapped spectrum.

Abstract: A method of manufacturing active optical fibers comprising preparing a preform and then drawing a fiber from the preform, wherein the method consists in using a preform having a doped peripheral outer zone, said zone being intended to constitute the outer cladding of the optical fiber, the doping of the peripheral zone giving it a refractive index greater than that of the optical cladding, and giving it a difference in softening temperature relative to that of the core of the optical fiber which is less than the difference that would exist if the outer zone were not doped.

Abstract: A power transmission system for the transmission of power or the transmission of movement from a first device to a second device comprises an endless flexible belt for transmitting power from a first power driven device to a second device for receiving the power. Such a belt can preferably be a toothed belt, also called a synchronous belt, as used, for example, on internal combustion engines for the synchronous propulsion of cam shafts at the cylinder head, and which belt has a construction capable of withstanding the operating environment for which it is intended.

Abstract: Method of outside plasma deposition onto a rod (17,22) of silica substantially free from hydroxyl ions, possibly doped to change its refractive index, by reaction with oxygen of a silicon compound and possibly of doping compounds, in the presence of a gas plasma raised to a very high temperature (16) by induction with the help of a high frequency generator (15). The rod on which the silica deposit is made is kept in a sealed chamber (19) separated from the surrounding atmosphere and supplied by a pipe (20) with atmospheric air that is successively passed through a filter (31), a compressor (32) a cooling means (33), a condensation water drain (35) and a final desiccation by adsorption (36, 38). A device for implementing the method is also claimed.

Abstract: A cylindrical piece of glass (4) is subjected to heating passes on a glassmaker's lathe. Possible opto-geometrical defects of said piece of glass are detected and measured and then said defects are corrected by machining the outside surface thereof during a correction pass performed on the same glassmaker's lathe.

Abstract: An optical amplifier in the 1.26 .mu.m to 1.34 .mu.m spectrum range, comprising a solid substrate of fluoride glass doped with praseodymium in which a three-dimensional monomode waveguide is formed having an index difference .DELTA.n relative to the index of the fluoride glass lying in the range 4.times.10.sup.-3 and 8.times.10.sup.-2, said waveguide being associated by coupling means to an optical pump having a wavelength equal to 1.02 .mu.m .+-.0.1 .mu.m.

Abstract: A method of fabricating preforms for making optical fibers by drawing, in which a silica deposit, including a doping agent, is formed in successive layers inside a silica-based tube (1) from a chemical vapor containing a gaseous compound of silicon, oxygen, and a gaseous compound of an element for doping the silica, with the composite tube then being subjected to collapsing so as to cause the empty axial zone (3), the tube hollow, to disappear. The silica of the initial tube is then eliminated, by removal, after which a recharge of silica (5) is made around the remaining cylinder (4) by plasma torch deposition from a gas comprising oxygen and a halogen derivative of silica.

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: This invention relates to a method for controlling the emission, and recovery, of volatile solvents. In particular, this invention relates to a type of finish material applying apparatus which has become known as a robotized spraying cabinet and to methods of operating such an apparatus. In accordance with this invention, materials sprayed through the spray head and which escape adherence to a sprayed articles impinge onto overspray directing members disposed adjacent the conveyor and between the conveyor and the reservoir, a quantity of solvent for the finishing materials is retained at a location adjacent the conveyor and supplying for use in cleaning the conveyor, and the overspray directing members and retained solvent to be supplied for cleaning are chilled and thereby the vapor pressure of the volatile solvent is reduced, whereby the volatile solvent is maintained in liquid form and control over the emission thereof is facilitated.

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 variable attenuation device intended to be inserted between a transmitter circuit having a certain internal impedance and a load circuit; it composed of at least on parallel attenuation branch made up from a variable resistance component (in particular a p-i-n diode) and a bias circuit to vary the resistance of the component as a function of an attenuation control variable. The parallel attenuation branch has a limiting component which is connected in series with the variable resistance component and whose value ensures the matching of the internal impedance of the transmitter circuit.

Abstract: The invention provides a device for delivering an indication about the mass per unit volume of the contents of an elementary volume, comprising a directional X or gamma radiation source and a directional photoelectronic photon detector, and wherein said source and/or said detector are mounted for rotation on a common support, about an axis orthogonal to the plane defined by the axis of the radiation beam emitted by said source and by the axis of the reception channel of said detector, and means are provided for moving said common support in a direction orthogonal to the axis of rotation of said source and/or of said detector.

Abstract: The invention relates to a laser cutting nozzle comprising at least two subsequent coaxial sections, the inside diameter of the first section decreasing from its inlet diameter to its outlet diameter and being devoid of a sharp corner, the inner envelope being tangent at its outlet to a cylinder having a diameter d, the second section being cylindrical and having a diameter D and a length l, the ratio D/d being between 1.1 and 1.3 and the ratio l/d being between 0.35 and 1. It relates to a laser cutting head comprising this nozzle and to a laser cutting method employing these elements.

Abstract: This invention concerns a device for the non-destructive inspection of a part (6) by means of optical holography. This device includes a source (2) emitting a laser beam and a holographic camera (4) placed at a certain distance from the source (2) and close to the part to be inspected (6); the laser beam is transmitted from the source (2) to the camera (4) by means of a beam of sequenced optical fibers (8) suitable for transmitting a high-powered laser beam, while maintaining the coherence of space and time of this laser beam. The device is suitable for interferometry nondestructive inspection applications.

Abstract: A method of fabricating an optical waveguide comprising a plane substrate made of a material having a relatively low refractive index, a plane light propagation layer made of a material having a higher refractive index than the substrate, inserted between two strips of a material having a lower refractive index than its own, and a plane light confining layer of a material having a lower refractive index than the propagation layer. At least one of the layer, meaning either the propagation or the confinement layer, is obtained by causing to circulate in a tube of pure silica the vapors of a gaseous compound of silicon transformable into silica and of a gaseous compound of a doping agent transformable into one of its own oxides and heating said vapors sufficiently to obtain the deposit of a layer of doped silica having a refractive index different from that of the pure silica.

Abstract: This invention relates to hoisting and traversing apparatus, and particularly to automatic hoisting and traversing apparatus which requires only a single motor for both hoisting and traversing. More particularly, the invention relates to a hoisting and traversing system in which the cable or chain which lifts the load can also be used to control the traversing movements of the load.

Abstract: A device comprising a lock with a rotating knob and incorporated bolt, capable of being blocked by the release of the rotating-knob unlocking control. The release results from the shifting of a blocking lever 13, 113 of the plate of the lock. The lever is operated by either a remote-controlled driving organ, or directly by the cylinder bolt. The blocking lever can, in addition, be inhibited by a locking lever 55, 155 operated from inside the trunk so as to neutralize the remote control.

Abstract: The blank is made from a tube of silica with a layer of other glass coated on its inner surface. The said other glass is doped with P.sub.2 O.sub.5 for example to increase its refractive index. The blank is then reduced in diameter from a tube to a rod by heating a region of the tube while it rotates in a glassmaker's lathe. The heated region is moved back and forth along the length of the tube until it is finally reduced to a rod. One effect of the moving heated zone is to evaporate some of the doping material, and the vapour tends to move along the tube ahead of the heated zone until it is eventually shifted out of the ends of the tube. To minimize this loss the back and the forth movement of the heated zone includes a sudden step forward at the end of each pass before returning in the opposite direction.

Abstract: A reactive gaseous mixture which reacts in a localized heating zone to form a glass deposit on the inner wall of a tube is made to flow along the tube, and in the heating zone it is channelled around a cylindrical element which occupies much of the bore of the tube. The glass deposit is used for making glass fibres for telecommunications.