Abstract: A body transparent to laser radiation, such as an optical fiber or a preform thereof in the process of manufacture, is transluminated by a monochromatic beam of a frequency in the THz range split off from a composite laser beam with two closely spaced frequencies produced by the Zeeman effect. Another monochromatic beam of the second laser frequency bypasses the transparent body and is photoelectrically recombined with the first beam to provide an electrical measuring wave at a beat frequency in the MHz range differing in phase from an electrical reference wave of the same beat frequency, similarly derived from the original laser beam, to an extent determined by the refractive index and the thickness of the transluminated body. Two or more phase comparisons are made with different angles of incidence of the transluminating beam and their results are compared for an arithmetic determination of refractive index and thickness.

Abstract: An automatic exchange of a telephone system comprises a PCM switching network with a plurality of cascaded stages for establishing temporal and spatial connections between incoming channels on input lines of the first stage and outgoing channels on output lines of the last stage in response to commands from external controllers dialoguing with internal controllers of the network. Pairs of switching matrices forming part of nonadjacent stages are combined into modular switching units each provided with its own internal controller. Routing instructions are transmitted from an external controller to a first internal controller which selects a signal path through the matrices of its own switching unit and informs a second internal controller of that selection whereupon the latter extends the path through an adjoining switching unit, and so on until the connection is completed.

Abstract: The system allows the implementation of packet-switched synchronous speech communications in the network without requiring any centralized device synchronizing all the network stations. To obtain that, the active periods of each station are subdivided into frames each having a duration equal to the time elapsing between the generation to two subsequent speech packets relating to the same communication; once a station has accessed the line for the speech communications, these communications are allotted time slots which are maintained for the whole communication duration. The slots not allotted to speech communications are allotted to data transmission. The access to the line for a speech communication is obtained by the same contention techniques used also for data transmission.

Abstract: A drum for winding up filamentary material, such as optical fibers, has a generally cylindrical unitary flangeless hollow body of airtight and somewhat resilient polymeric material inflated under a fractional gauge pressure through a valve in one of its end walls. A bore in each end wall, centered on the cylinder axis, enables the drum to be coupled with a driving mechanism.

Abstract: An apparatus for the recovery of an amplitude-modulated and phase-modulated signal wherein the signal is multiplied by two correction and adjustment signals in phase-quadrature in a pair of multipliers connected in low-pass filters to the sample and decision circuit. The output of the latter is an error signal which represents the phase error of the recovered carrier obtained by the comparison made between the baseband components of the demodulated signal and suitable decision thresholds at a decision instant estimating transmitted digital symbols. A logic circuit is connected to the output of the sample and decision circuit and delivers its output to a pulse generator whose correction train of pulses is filtered before being applied to a voltage-controlled oscillator whose output is applied directly to one of the multipliers and through a quadrature-phase shifter to the other.

Abstract: An optical fiber, being drawn from a preform and wound upon a reel, passes between parallel plates of a capacitor connected in a measuring circuit which, from the capacitance variations due to changes in fiber diameter, controls a reel-driving motor to minimize these variations. The capacitor may have a constant charge, as by having one of its plates made of an electret, in which case the capacitance variations are determined from voltage changes. A calculator connected to the measuring circuit translates these variations into numerical values representing the fiber diameter which can be visually displayed.

Abstract: Each of several stations served by a common bus in a communication system of the packet-switching type has a layered structure interposed between a user terminal and a port giving access to the bus, this structure including an interface separating a transceiver at a bottom level of the structure from upper levels controlling the establishment, maintenance and termination of temporary signal paths for the transmission of data between stations. The interface is divided into a lower-tier portion, implemented by wired-logic circuitry, and a higher-tier portion, programmed to set up virtual point-to-point data links between its own station and other stations under the control of a microprocessor. The lower-tier portion dialogues with the transceiver and has transmitting and receiving sections with respective buffer memories for the temporary storage of outgoing message frames generated at the higher-tier portion and incoming message frames extracted from the bus and found to be addressed to the station involved.

Abstract: The device comprises a plurality of circuits interfacing a computer with a plurality of professional videorecorders, for the automatic control by computer of all the operations carried out by the video-recorders. Each of the interface circuits requests of the computer only data allowing its addressing, data identifying an image sequence on which the video-recorder must operate and data on the kind of operation to carry out, and comprises a logic circuit, which is capable of shortening the time taken by the videorecorder to search for the sequence and determines the direction and the speed of the magnetic tape depending on the determination of the position of the point being read on the tape with respect to the sequence position, and a further circuit able to detect errors of data setup by the computer and errors due to data misinterpretation by the videorecorder.

Abstract: An equalizer designed to correct both precursor and postcursor distortion in signal samples periodically obtained from a train of digital symbols comprises two parallel circuit branches each including a delay line preceded by a linear upstream filter for postcursor suppression in the case of the first branch and precursor suppression in the case of the second branch. A decision stage in parallel with the delay line of the first branch works into a nonlinear downstream filter delivering a precursor-correcting signal to an adder which also receives precorrected earlier signals from the two delay lines. A second decision stage connected to an output of the adder feeds back to that adder a postcursor-correction signal via another nonlinear downstream filter. The purged signal emitted by the second decision stage may be subjected to additional filtering and precursor/postcursor correction with the aid of another adder and a third decision stage provided with a further feedback loop.

Abstract: In order to suppress noise due to reflected outgoing signals in a telephone receiver of a system for the bidirectional transmission of digitized voice signals over a two-wire telephone line connected by a hybrid coil to an outgoing section and an incoming section of a subscriber station or of an exchange, a shift register loaded with several (e.g. five) consecutive transmitted bits from the outgoing section addresses the cells of a memory containing the digitized amplitudes of corrective signals assigned to the several bit combinations which may be present at any time in that register. The corrective signal read out from the memory during each bit period is subtracted in the incoming section from an arriving signal and the result is fed on the one hand to a receiver and on the other hand to an algebraic adder as a modifying signal incrementing or decrementing, if need be, the contents of the corresponding cell during a writing interval which is a small fraction of a bit period.

Abstract: Digitized message samples or bytes appearing in time slots of an outgoing PCM frame, temporarily allocated to respective local channels such as telephone lines of limited activity, are written during alternate storage periods of, say, 32 ms (each encompassing 256 PCM frames) in a pair of memories from which they are alternately read out in a different sequence to form special packets of interleaved bytes from respective channel pairs or other channel groupings. A number of such special packets are assembled together with other packets from more active channels into an outgoing TDMA frame which forms part of a superframe equal in length to a storage period; the TDMA frames are modulated at an accelerated bit rate upon an r-f carrier for transmission to a relay station aboard a satellite. Upon redistribution of the packets at the relay station according to their respective destinations, they are beamed back to earth for reception by other ground stations.

Abstract: A terminal of a digital telecommunication system working in a so-called "ping-pong" mode, with alternate reception and transmission of data words in respective halves of a recurrent operating cycle, has a phase-lock circuit whose oscillator is stabilized by a control signal periodically extracted from an incoming bit stream during the data-receiving phases. The receiving section of the terminal has a branch obtaining incoming bipolar data words from an input/output transformer and converting them, with the aid of a peak detector and an integrator or a monoflop, into respective timing pulses whose leading edges recur with the same periodicity as the data words.

Abstract: A line loop designed for the transmission of digitized voice samples as well as data words between an exchange and several subscriber terminals, not all of them necessarily equipped for voice communication, is connected through a modem to a bus with parallel branches extending to all the terminals, each branch including an outgoing-data lead, an incoming-data lead and two ancillary leads carrying clock pulses for the timing of data transmission and reception which are generated at the exchange. Each terminal, identified by a multibit address, is provided with an interface including a carrier sensor which detects the free or busy state of the line--during a time slot assigned to data transmission--on the basis of a certain protocol according to which an idle state is denoted by an unbroken succession of at least seven bits of predetermined logical value (here "1").

Abstract: A digital transcoding unit receiving incoming PCM-coded speech and data samples to be distributed after selective quantization to different outgoing channels, with fewer quantizing bits assigned to speech samples than to data samples, includes a discriminator distinguishing among speech samples, high-rate data samples and low-rate data samples on the basis of bandwidth and number of zero crossings. Low-rate data samples are directed by the discriminator to outgoing speech channels, rather than data channels, for more efficient transmission-line utilization.

Abstract: Vapor deposition of doped silica in a reaction chamber on a rotating supporting surface, in the manufacture of a preform for the drawing of an optical fiber, is accompanied by the continuous admixture of deuterium with a flow of carrier gas, specifically oxygen, by which the reactants are transported to the reaction chamber. An isotopic substitution of deuterium for the hydrogen of hydroxyl groups in the reaction products shifts the major absorption peaks to wavelengths outside the minimum-attenuation range of 0.7 to 1.6.mu. used for fiber-optical signaling. The proper ratio of deuterium to carrier gas is maintained with the aid of a mixer having two compartments separated by a perforated diaphragm or a thin metallic foil, one compartment being connected to a deuterium tank while the other communicates with a conduit through which the vapors entrained by the carrier gas pass to the reaction chamber.

Abstract: A nozzle used in the coating of optical fibers with a protective resin layer comprises an aluminum body split into two symmetrical halves with cavities which upon assembly form a frustoconical funnel terminating at its narrower lower end in a coaxially converging outlet port. The cavities are machined in solid aluminum blocks whereupon each block is anodized in sulfuric acid to form thereon an abrasion-resistant oxide layer with few, small pores which may be sealed by an aftertreatment in hot de-ionized water.

Abstract: A light source of rectangular outline, such as a semiconductor laser, is coupled to a light receiver of circular outline to be illuminated thereby, such as an end of an optical fiber, by an anamorphotic system including a pair of spherical lenses and an afocal pair of cylindrical lenses interposed in a telecentric field therebetween. When the system is used for measuring the attenuation of a fiber by the back-scattering technique, a semireflecting prism inserted between the cylindrical lenses and the fiber-side spherical lens directs part of the returning beam toward a photodetector; the effect of spurious reflections at the fiber end may be minimized by the use of a polarization-sensitive Glan prism and/or by the positioning of a flat transparent plate in front of the fiber end.

Abstract: A transceiver inserted between a signal source and a two-wire or one-wire line, designed to transmit balanced or unbalanced digital signals to a remote station at the opposite end of the line while receiving similar signals from the latter station, comprises a first and a second amplifier with inputs connected to the line at a proximal and a distal end of a line-terminating impedance, respectively. Each amplifier has an inverting output connected to a noninverting output of the other amplifier, the two nodes formed between the interconnected outputs being connected to respective inputs of a differential third amplifier feeding a signal receiver. The gain of the first amplifier is half that of the second amplifier whereby the locally generated signals are suppressed in the output of the third amplifier. The several amplifiers are realized in integrated circuitry and may be provided with switches for selective changeover between a balanced and an unbalanced mode of operation.

Abstract: In order to improve the transmission characteristics of optical fibers drawn from the preforms manufactured by vapor deposition of silica on an inner wall surface of a supporting tube of glass, the tube is subjected to a two-stage heat treatment with deuterium whereby OH.sup.- groups at least on the inner tube surface are isotopically replaced by OD.sup.- groups. This pretreatment can be carried out in the same apparatus which is subsequently used for producing the preform.

Abstract: Telephone lines extending between a central office and associated subscriber stations are provided at opposite ends with mutually complementary modems and with couplers by which code signals from subscriber-operated address selectors can be sent to a common data network containing specialized information or to associated data-retrieval units. The latter are connected in parallel to a bus originating at a data bank from which data bits grouped into pages are continuously emitted at high speed. Each retrieval unit comprises two shift registers, one of them being loadable from the bus by the incoming high-speed bits to store a complete page together with an accompanying address code while the other receives a selected address code from the associated subscriber. A comparator, upon detecting an identity between the coded addresses stored in the two registers, stops the loading of the first shift register and commands its readout over the subscriber line at a slow rate compatible with that line's bandwidth.