Abstract: An optical frequency-encoded CDMA transmission system is presented in which received optical signals are decoded in the electric part of an optical receiver (12). To that end, the optical receiver (12) has a single photodetector (6) which converts received light into an electric signal, and which is directly or indirectly connected to a decoding unit (9, 10; 13, 14, 15), for recovering the information contained in the characteristic frequency-encoded spectrum.

Abstract: A method of fabricating a fluoride glass optical fiber preform which has a fluoride glass core surrounded by a fluoride glass optical cladding includes the following steps: introducing the cladding glass in the molten state into a bottom part of a mold having a cylindrical inside cross-section, introducing the core glass in the molten state into a top part of the mold above the cladding glass, and inwardly solidifying the core glass and the cladding glass from the interface between the glasses and the mold. The kinetics of solidification of the core glass are such that complete solidification of the cladding glass occurs before complete solidification of the core glass.

Abstract: To shape binary optical signals, the apparatus comprises a first stage for providing a modulating signal whose high levels are stabilized so as to depend little on fluctuations in the input signal. The signal is applied to a second stage including an interferometer structure designed to deliver an output signal that is the result of interference between first and second auxiliary waves, the interference being respectively constructive and destructive when the power of the modulating signal corresponds respectively to a first logic state and to a second logic state. The apparatus can be used to modify the input signal by deleting or inserting data. It can be used in optical data switching or transmission.

Abstract: A method of preparing faces of a laser based on III-IV compounds, the method comprising the following operations:1) the faces of the laser are opened;2) said faces of the laser are placed in an enclosure in which there obtains a pressure of about 10.sup.-7 mbar to about 10.sup.-8 mbar, and they are subjected to a step of cleaning by irradiation with a pulsed laser; and3) the same pulsed laser is used to ablate a target so as to subject said faces to a passivation operation whereby silicon Si or gallium nitride GaN is deposited thereon by the pulsed laser deposition method until a thickness is obtained lying in the range 2 .ANG. to 20 .ANG..

Abstract: Apparatus and method for controlling the electromagnetic torque of an asynchronous machine. The apparatus includes a corrector which controls the electromagnetic torque of an asynchronous machine by regulating the magnetic flux and by controlling the electromagnetic torque C.sub.m, the corrector including a regulator circuit (3) for regulating the rotor magnetic flux .phi..sub.r , having non-linear control using input/output linearization by static looping and whose output controls the d-component of the stator current i.sub.s, a first linear corrector (1) of the proportional, integral type whose output v is the input to the regulator circuit, and a second linear corrector (2) of the proportional, integral type whose output controls the angular frequency of the rotor currents .omega..sub.s1.

Abstract: The method is used in a switching network over which data packets are transferred and which includes a plurality of switching nodes with switching node terminations (SNT) and associates in each one of the switching node terminations (SNT) internal header information (IHI) included in an internal data packet received by the switching node termination and identifying an internal connection within the switching node and ending in the switching node termination, to external header information (EHI) included in an external data packet and identifying an outgoing external connection external to the switching node and originating from the switching node termination. The internal header information (IHI) includes a connection reference number (CRN) and a transfer type is associated to the internal connection. The method comprises three steps:a. determining the transfer type;b.

Abstract: A system for writing a Bragg grating point-by-point in an optical waveguide includes an illumination system for producing a primary beam. It further includes a diffraction grating to receive the primary beam and to produce a zero order secondary beam and two symmetrical secondary beams of higher order and a focusing optical device for focusing the secondary beams onto a writing area of the waveguide. The diffraction grating and the focusing optical device define an intensity function of writing in the area of the guide including a central peak and two secondary peaks spaced from the central peak by a distance equal to the pitch of the grating.

Abstract: The control path of the switch (I) comprises an input stage (T2, T1) having an input (H) coupled to the input (E) for the control signal and having its output coupled to the control electrode (G) of the switch (I). A protection circuit (D1, Z2) coupled between the load (C) and the control path includes a threshold effect component (Z2) and a decoupling element (D1). On being made conductive by the current that results from a surge generated in a circuit of the load (C), the protection circuit (D1, Z2) is coupled to the input (H) of said input stage (T2, T1) to act on said switch (I) in the same way as a control signal for the switch (I). In this manner, the control path prevents current in the load (C) from dropping off suddenly.

Abstract: The demultiplexer comprises a diffraction space defined by a reception surface coupled to a grating. In order to obtain output waves of flattened spectral response, the input waveguide and the reception surface are dimensioned so that the input wave diffracts over said surface and presents a plurality of secondary lobes. The demultiplexer is particularly applicable to optical communications systems with wavelength multiplexing.

Abstract: In a method of fabricating a surface emitting semiconductor layer, to achieve good electrical confinement and good flatness of the mirrors delimiting the resonant cavity of the laser, an electrical confinement layer is made by growing a localized aluminum alloy layer on the active layer, except for an opening area on top of which the mirror is to be formed. After epitaxial regrowth, the alloy layer is oxidized laterally. Applications include the fabrication of semiconductor lasers on III-V substrates such as InP and GaAs.

Abstract: The invention is drawn to organic compounds of the general formulae L--A--Z or L--A'--L' as defined in the specification. The compounds are readily crystallizable and can be used for their ferromagnetic properties.

Abstract: A sheathed twisted superconductor with a high critical temperature is made from a billet obtained by assembling square cross-section single strands in a square cross-section metal tube. The multistrand obtained by drawing the billet through a roller die is twisted with a particular lay and rolled using rollers the diameter of which is much greater than the twist lay. The sheathed twisted superconductor obtained by this method is intended for variable current applications.

Abstract: A method of managing concurrent accesses by a plurality of users to a memory, for reading or writing data in memory zones of the memory on the basis of an index whose value identifies a memory zone in the memory, includes the steps of: recording the value of the index in a first memory register; summing the contents of the first memory register with an increment value; recording the result of the summing operation in a second memory register; atomically interchanging the index value with the contents of the second memory register; and taking the content of the first memory register as the current value of the index if the contents of the second memory register is identical to the old value of the index, otherwise performing each of the preceding steps again.

Abstract: A method of manufacturing a supercapacitor electrode containing a metal oxide and carbon-containing material, the method including the following steps: starting from a salt of said metal dissolved in an aqueous solution of a strong base, the hydroxide of the metal is precipitated in the form of a gel by adding an alcohol; the precipitate of the hydroxide of the metal is washed and dried; active carbon is added to the precipitated hydroxide of the metal to consitute a first mixture; the first mixture is subject to heat treatment in order to transform the hydroxide into an oxide, and a mixture of metal oxide and of active carbon is obtained which constitutes the active material of the electrode; and a binder is added to the active material to form a paste which is put into the form of an electrode.

Abstract: Crystalline compounds with ferromagnetic properties are described which are inclusion compounds comprising metal salts in copolymers in which the repeating unit includes one unit from a first group of aminoaromatic derivatives of 1-naphthylamine and corresponding oxidized forms, connected to one unit from a second group of substituted aminoaromatic compounds selected from substituted amines containing at least two condensed benzene nuclei, substituted polycyclic compounds containing at least one aniline moiety in their structure, and aniline derivatives carrying a substituent connected to the nucleus by an ethynylene or para-phenylene unit, and corresponding oxidized compounds. Methods for the preparation of these compounds are also described.

Abstract: The present invention concerns a magnetic copolymer having a structural unit comprising a first multivalent radical and a second multivalent radical derived from an aminoaromatic compound selected from a substituted amine containing at least two condensed benzene nuclei, a substituted polycyclic compound containing at least one aniline unit in its structure, and an aniline derivative substituted on the ring by an ethynylidene or paraphenylene side chain, these compounds being in their reduced or oxidized forms, said first and said second radical being coupled together by a carbon-nitrogen bond and the nitrogen atoms being separated by a single aromatic ring, characterized in that said first radical is derived from a compound selected from 1-naphthylamine, which may be substituted, in its reduced or oxidized form.

Abstract: A facility for detecting intrusions and suspect users in a computer installation, and a security system incorporating such a facility that makes use of surveillance data relating to the operation of the installation. The facility includes elements for modelling the computer installation, its users, and their respective behavior with the help of a semantic network; elements for comparing the modellized behavior of the system and of its users relative to modellized normal behavior; elements for interpreting observed anomalies in terms of intrusions and of intrusion hypothesis; elements for interpreting observed intrusion hypotheses and intrusions in order to indicate them and enable restraint actions to be prepared. Elements are provided to evaluate the degree of suspicion of users. The elements co-operate with one another for the purpose of providing information.

Abstract: In a method for securing the display on a screen of a workstation of mimic diagrams reflecting the status of a system connected to the workstation, a first counter is maintained in the system and a second counter is maintained in the workstation. The system periodically transmits to the workstation image data defining a mimic diagram reflecting the current status of the system, together with the first counter and a signature. In response, the workstation displays on the screen a mimic diagram based on the image data received and calculates a test value conditioned by the first and second counters, this value providing a basis for detecting a display error.

Abstract: The present invention provides a method of charging a carbon-anode lithium storage cell, which method comprises a first step in which a constant current is imposed and during which the voltage across said storage cell is allowed to increase until it reaches a reference value, and then a second step in which said reference voltage is imposed and said current decreases. The method of the invention is characterized in that, at each instant, said reference voltage is equal to the sum of the end-of-charge voltage of the cell plus the product of the current multiplied by the ohmic resistance of the cell.

Abstract: A method of preparing a substrate with a view to depositing a thin layer of a superconductive material thereon, wherein an operation is performed of depositing on the substrate an intermediate material having the property of having a crystal lattice constant that is a function of the percentage of a doping element, the depositing operation being initiated with a concentration of the doping element such that the lattice constant of the intermediate material is equal to or as close as possible to the lattice constant of the substrate, the proportion of the doping element being continuously varied during the depositing operation to a proportion of the doping element such that the lattice constant of the intermediate material is equal to or as close as possible to the lattice constant of the superconductive material.