Abstract: Semiconductor structure having a virtual diffraction grating.This structure comprises an intermediate semiconductor layer (4) between two other semiconductor layers (6,8) having opposite dopings and on one side of the intermediate layer a periodic arrangement or layout (12,14) able to spatially modulate the distribution of the charge carriers or the electric field in said intermediate layer when an electric current is injected into the p-n junction formed by the two other layers or said junction is reverse biased. The periodic arrangement is located in one of the first and second semiconductor layers and is constituted by a sequence of first semiconductor zones having a doping below 10.sup.19 cm.sup.-3 and of the opposite type to that of the semiconductor layer in which the periodic arrangement is located, alternating with second semiconductor zones having the same doping type as that of the semiconductor layer in which the periodic arrangement is located.

Abstract: The invention relates to a process for the analysis of all or part of the informations contained in data structures or formats in order to supply to an external system the informations necessary for the despatching or routing of said data structures or for the processing thereof by an intelligent external system, in which analysis takes place of the significant fields of said data structures, particularly the source or destination addresses, using the principle of translation tables by successive indirections in a two-dimensional array TRIE (i, j), each line of the array constituting a register having 2.sup.k cells, in which k is the length of the addressed segment. In this process, the search in the translation tables takes place with the clock cycle of the entering information by data structure segments.

Abstract: The present invention relates to a device and process for the digital coding and decoding of speech comprising a short term prediction, a long term prediction and a residual wave coding technique using a synthesis analysis method. The LTP analysis module uses a dictionary of delays having a pseudo-logarithmic structure, in which the delays are arranged in increasing order. This dictionary is constituted by segments, each having a given resolution, the resolutions of the successive segments decreasing geometrically in a rational ratio k>1, while the number of elements of each segment remains constant. The invention defines the use of .lambda. delay elements of said dictionary extending the LTP analysis techniques to high time resolution. The invention also relates to a process for the rapid scanning of such a pseudo-logarithmic delay dictionary. It also relates to a process for implementing a selection criterion of the delay in closed loop with perceptual filtering.

Abstract: An integrated monolithic laser-modulator component having a multiple quantum well structure. This component includes an InP substrate, a laser (L) formed from a stack of semiconductor layers epitaxied on the substrate, including an active and absorbent layer and a periodic Bragg grating fixing the emission wavelength of the laser to a value slightly above an optimum wavelength of the laser gain peak. An electrooptical modulator (M) is formed from the same stack of semiconductor layers, with the exception of the Bragg grating, the active layer of the laser and the absorbing layer of the modulator being formed by the same epitaxied structure having several constrained or unconstrained quantum wells, the modulator functioning according to a confined Stark effect. The semiconductor layers of the laser and those of the modulator are electrically controlled.

Abstract: Light diffraction device using reconfigurable spatial light modulators and the fractional Talbot effect. This device comprises two liquid crystal, electrically addressable spatial light modulators (M1, M2) on a semiconductor substrate and at least one polarizing beam splitter (2), the optical path between the modulators being equal to (2k+1) Z.sub.T /4.sup.n in which k and n are natural integers, n differing from zero, and Z.sub.T is the Talbot distance relative to a biperiodic hologram obtained by means of one of the modulators and at one of the periods equal to double the other, which makes it possible to obtain a reconfigurable hologram having four phase levels. Application to optical telecommunications.

Abstract: The present invention concerns a method for transmitting and switching packets in an optical network embodying a synchronous time-division multiplexing, the packets being transmitted at a given speed and the rate being determined by the line occupation time.The present invention also concerns a device for transmitting and switching packets in an optical network.

Abstract: The invention concerns a system and process for sending secure faxes that include a sending fax machine (20); a receiving fax machine (23); and a registered fax server (21). One of the fax machines is provided with a security module that assures document integrity, produces and verifies digital signatures and combats replays.

Abstract: A photorefractive device intended to be exposed to a marking radiation which is provided so as to create a grating of interference fringes in the device and to a reading radiation diffracted by the created grating. The device includes an electro-optical material having a quantum well structure (24) and formed in an intrinsic semi-conductor matrix (22, 24) and, on both sides of the material in the semi-conductor matrix, suitable means (28, 30) to trap, both parallel to the axis of the structure and perpendicular to this axis, free carriers generated by the marking radiation.

Abstract: Optical component having a plurality of Bragg gratings and process for the production of said component.According to the invention, an optical component is formed comprising a light guide and Bragg gratings which are formed in the guide and have predetermined Bragg wavelengths. This guide comprises a single diffraction grating (16) and zones (24, 26, 28, 30) associated with the Bragg gratings and. The zone have optical indices chosen so as to obtain, in cooperation with the diffraction grating, the Bragg wavelengths.

Abstract: An interface device between a public telephone (9) and an external terminal (14), the public telephone (9) having a control circuit (10) connected to a telephone line (20) and the interface device having a connector (15) accessible to the user. A switching circuit (22) makes it possible to switch the line (20) either to the control circuit of the public telephone (10), or to a connector control circuit. An information circuit of a connection of the external terminal is in the connector, a first electrical insulation module (21) is located between a connector control circuit and the switching circuit (22), a second electrical insulation module (19) is between a connector control circuit and the control circuit of the public telephone (9) and a control circuit of the connector (16).

Abstract: A process for the transposition of a modulation of an adjustable wavelength. A semiconductor amplifier is relooped through a feedback loop including a filter set to a first wavelength. An incident beam set at a second wavelength which is amplitude modulated is injected into the semiconductor amplifier laser. The incident beam is either extinguished or allows self-oscillation to be established in the loop. Thus, the modulation is transposed from the second wavelength to the first wavelength.

Abstract: Small, high precision, multicore optical guides and process for the production of said guides. Such a guide includes elementary guides (G1 to G4) and a matrix (M) in which they are located. These elementary guides are very accurately positioned with respect to one another in the matrix and with respect to the external contours (5) thereof and have high precision geometrical characteristics. According to the process, manufacturing and machining of the blanks so as to obtain, after assembly, the chosen geometrical model for the multicore guide. They are assembled in accordance with this model, welded together by means of a bait and the assembly is drawn.

Abstract: Optical communications system using traveling wave semiconductor optical amplifiers has at lest one optical fiber (2), tranceivers, (S1. . . , SN) placed along the fiber and having in each case at least one travelling wave semiconductor optical amplifier (A1. . . , AN), which is located in series with the fiber and transmission means (L1, L2) for feeding into the fiber at least one continuous optical signal. Each amplifier is used alternately to modulate the continuous optical signal in order to transmit information, and to detect information modulations of the optical signal which carry information.

Abstract: The network according to the invention combines a circuit switching multicoloured optical network (R1) and a packet switching network (R2). The circuit switching network is adapted to transmit data at a high rate. The packet switching network is adapted to transmit data at an average rate. Control data are carried on the packet switching network. This provides more efficient transmission of data and effectively handles peak transmission rates. The invention has application to telecommunications.

Abstract: Optical amplifier with a doped fluoride glass optical fibre and process for the production of said amplifier.In said amplifier, two monomode silica fibres (4a, 6a), whereof at least one is doped with erbium, are coupled to two ends of an erbium-doped, fluoride glass monomode fibre (2) and have the same optical mode diameter as the latter. Application to optical telecommunications.

Abstract: An association memory which permits the execution of all kinds of comparative operations. The associative memory includes a memory map (1) in which a search argument, which has been processed in a scanning module (3) and a masking unit (5,7), is compared to the data stored in the memory. After this comparison, the data obtained is recorded in a response register (11). When the search data and the stored data supply an association of variable length words, the result data is processed in a module for the processing of variable-length words (13) and in a multiple-response management module.

Abstract: The present invention relates to a device for the vector measurement of ultra-high frequency signals of the same angular frequency of the six port junction type, comprising a power divider (10) and a phase shifting circuit (11) two of the six ports of said device being measuring ports connectable to two sources of signals to be characterized, the four other ports being connected to four detectors, one of them being a matched detector (14) and the three others (12, 13, 15) being unmatched detectors.

Abstract: Smart card payment process.The card in particular contains an irreversible counter, a balance and a certificate proving the integrity of the preceding informations. The content of the card can only be updated by terminals knowing, the calculation secrets of the certificate. By means of the irreversible counter which intervenes in the calculation of the certificate, it is not possible to reload into the card a prior content (balance/certificate), because such a reloading requires the incrementation of the counter, which renders null and void the prior certificate.

Abstract: An amplitude optical modulator which utilizes a two-electrode DFB laser structure. The amplitude optical modulator includes a current generator which can modulate at least one of two currents injected into the DFB laser structure. This modulation displaces a spontaneous emission peak of the DFB laser structure, which leads to an amplitude modulation of the injected optical beam. Such an amplitude optical modulator may find particular application in an optical telecommunications system.

Abstract: The invention relates to a supply system, with uninterrupted distributed storage, for sensitive operation systems supplied from the public electric energy distribution network (10) or an emergency power supply (11) producing an equivalent voltage, said system incorporating at least one short term energy reserve supply circuit (30) associated with each supplied system and a medium term energy reserve supply circuit (31) having a reaction delay below the autonomy delay of the short term energy reserve supply circuit.