Abstract: A fast packet and frequency switch, with inputs and outputs connected to optical fibers, each allowing the transit of a certain number of different-wavelength optical carriers, modulated by serial information flows organized into packets. The packets are phase-realigned and their labels are converted under the control of external processors designed to set-up and break connections. Then a frequency conversion of the optical carriers allotted to packets is carried out and the packets are recombined into a single fiber by a passive recombination network in order to be stored into an optical loop memory, which is an optical fiber delay line. Each optical packet flow is extracted at suitable times, is frequency-converted and, among the various frequencies obtained, there are selected only those to be sent to corresponding output fibers outgoing from the switch, after having been recombined with those of the other converted flows.

Abstract: An automatic system for adjusting the output impedance of fast CMOS drivers, wherein the output impedance of a plurality of slaved drives is adjusted by a circuit for measuring and correcting mismatch between the output impedance of one of the drivers, taken as reference and dedicated for this purpose, and the impedance at the input of a reference transmission line, equal to the lines connected to the other drivers. The measuring of the output impedance of the reference drive is indirectly effected by inserting at the reference drive input a clock signal and by periodically measuring the output on the reference transmission line in correspondence with the positive half-period center.

Abstract: The system uses a monochromatic radiation source (1) and an acousto-optic modulator (2), which acts as a Bragg modulator and is driven by a frequency which is caused to periodically vary. The modulator emits a first beam having the same wavelength as the source and a second beam, whose wavelength and emission direction vary with the modulating frequency and which is collimated. For measuring angular displacements, the collimated beam is recombined with the first beam after traversing a plate (5) with parallel and plane faces integral for the rotation with a moving device, and a photodetector (12) generates a beat signal whose frequency depends on the angular position of the plate (5). For measuring linear displacements, the two beams are directly sent onto a detector (12) integral with the moving device.

Abstract: A fast packet switching system has an interconnection network associated with a distributed control structure composed of a plurality of processing units (UC1-1 . . . UC3-16) managing the routing at the virtual call level. At least some processing units each associated with a group of network inputs/outputs store bandwidth occupancy data relevant to the interstage links which can be reached from the inputs of the group and are included between the inputs and a central network stage where there is a maximum number of alternative paths or, respectively, bandwidth occupancy data relevant to interstage links which lead to the outputs of the group and are included between the stage and the output, the data being updated whenever a new call is routed.

Abstract: A device for the correlation between optical beams having spatially modulated intensities has an active glass window, which on one side is illuminated at the same time by a reading and a pumping beam through one or a plurality of semitransparent mirrors. The reading beam has radiations with a wavelength equal to that of a transition between an intermediate and fundamental energy level. The pump beam has radiations with a wavelength corresponding to the energy of the highest power level of the material forming the active glass, obtaining on the other side of the window a light beam representing the correlation betwen the pumping and reading beams.

Abstract: The cavity resonator is composed of a closed metallic body transversely subdivided into two parts, housing a small dielectric cylinder, which is held in coaxial position inside the cavity by two small quartz plates provided with a centering indentation. Holes are provided in the lateral surface for tuning screws and an access connector and coupling irises can be cut in the bases.

Abstract: The characteristic parameters of a semiconductor laser (1) acting as an amplifier and brought to bistable operating conditions are determined. The output power (I2) of laser (1) is measured as a function of the power (I1) of an amplitude-modulated optical input signal to determine the laser hysteresis loop; the switching points (P1, P2) between the two stable states of the laser (1) are identified, the input and output power values relevant to such points are memorized, and at least the value of the non-linear refractive index coefficient (n.sub.2) of the material used to fabricate the laser (1) as determined starting from the power values relevant to at least one of said points (P1, P2). By exploiting the power values relevant to both switching points (P1, P2) also the amplification factor (A), the finesse parameter (F) of the passive cavity of the laser (1) and the wavelength difference (.lambda.1-.lambda.

Abstract: A label-switching and control interface for asynchronous fast-packet switching consisting of a set of label-switching and cell-processing units controlled by a suitable control unit. The units operate at each multiplex level in real time thanks to a microprogrammed logic requiring the control processor intervention only at the connection set-up/release. The units implement the low levels of the flow control algorithms necessary to conveniently exploit the advantages of the techniques. The label becomes indicative of a virtual circuit which is allotted only locally to the call, annulling thus the necessity of very extensive labels, while the parameters which characterize the connection which uses a particular label are stored in the unit itself.

Abstract: The coaxial-waveguide phase shifter consists of a coaxial waveguide section, comprising an external cylindrical conductor and an internal cylindrical conductor, both hollow. Between them a number of irises are provided parallel to one another. The irises can be differently shaped and can be fixed to the external or to the internal conductor. By replacing the internal cylindrical conductor with a rectangular conductor, the irises can be unnecessary.

Abstract: A node for a fast packet-switching network in optical-electrical technology comprises an optical switching matrix and electrical control equipment which processes the signalling and the information packet headers. More particularly, the control equipment updates the label and, depending on such a label, searches for the routing through the node. A centralized node controller processes the signalling, while a distributed processing system processes the packet headers and routes the packets through the network. For all communications in progress, the distributed processing system periodically forwards routing requests to an electrical self-routing switching matrix associated with the optical matrix. When a connection path has been found between an input and an output of the electrical matrix, the same path is reproduced in the optical matrix and the packets are transferred to the node output through the optical matrix.

Abstract: The value of a transverse moment of any order of the electromagnetic field associated with an optical beam (and in particular the spot-size of such a beam) is determined by two successive measurements of the optical power of the beam: one measurement is a direct measurement, the other is effected after spatially modulating the transverse distribution of the electromagnetic field by a factor proportional to the n-th power of the transverse coordinate of the beam, n being the moment order. The moment can be obtained from the ratio between the two measurements. The invention includes also the apparatus for carrying out the method.

Abstract: An electrooptic deflector composed of a plate made of a material with a refractive index which can be modified by the application of an electrical field, whereinto a collimated optical beam can be injected in direction parallel to the electrodes deposited on a plate face. Said electrodes are parallel to one another, equally-spaced and separately connected to voltage sources apt to increase the refractive index in the material passing from an electrode to the next. The emerging optical beam is deflected in the direction wherein the refractive index increases.

Abstract: A silica glass optical fiber is subjected to an external strain which causes vitreous matrix atoms to stabilize in a lower energy condition. In this way inhomogeneity domain sizes and as a consequence the attenuation due to Rayleigh scattering, depending on such inhomogeneity, are reduced.

Abstract: A silica glass optical fiber is subjected to an external strain which causes vitreous matrix atoms to stabilize in a lower energy condition. In this way inhomogeneity domain sizes and as a consequence the attenuation due to Rayleigh scattering, depending on such inhomogeneity, are reduced.

Abstract: A method is described for decoding messages coded as blocks consisting of a fixed number of symbols and affected by symbol substitutions, deletions and insertions, wherein for each received message having a length comprised within predetermined limits, a sequence of words (error frames) is generated which comprise all possible error combinations which can be corrected in the message. By using such error frames, a decoded word is generated for each frame, the probability that a decoded word actually is the transmitted word is calculated and the decoded word, whose probability value satisfies predetermined criteria, is emitted as a decoded message. A device for carrying out the method is also provided.

Abstract: In producing a preform for an optical fiber by MCVD technology, involving the buildup of a core matrix of doped silica layers inside a glass tube with subsequent thermal collapse of the structure, a layer of dopant is deposited on the inner surface of the finished core matrix before the collapse. The thickness of this dopant layer, which advantageously is in a colloidal state, progressively diminishes along the tube axis in a direction away from an end of the tube at which the collapse begins. The law of thickness variation is chosen to maintain an internal gas pressure of vaporized dopant equal to the vapor pressure of the dopant in the core material at the collapsing temperature, in order to prevent the appearance of a paraxial dip in the refractive-index profile of an optical fiber subsequently drawn from the collapsed preform.

Abstract: In a method for the automatic frequency control of semiconductor kasers, the signal emitted from the laser (1) is sent to an optical resonator (6) whose resonance frequency is modulated by a ramp signal, the signal outgoing from the resonator (6) is converted into an electrical signal, the derivative of such an electrical signal is calculated, the zero crossing of the derivative is detected, the ramp signal is sampled in corresponding with such a zero crossing, and the sample thus obtained is algebraically summed to a reference signal depenent on the nominal laser emission frequency, thus obtaining an error signal which is sent to devices (3) driving the laser (1). In case of a plurality of lasers (1a . . . 1n) the signals of which are wavelength multiplexed, the rame signal is sampled in correspondence with the derivative zero crossings corresponding with the emission frequencies of the individual lasers (1a . .

Abstract: A fixture for measuring the static characteristics of microwave active components has mechanical devices for supporting two dielectric substrates. Two terminals of the components under test are separately connected to electrical circuits constructed on said dielectric substrates. This fixture can be adapted to geometric sizes of component case and allows it to be submitted to thermal tests, without mechanical stresses due to expansion. The electrical circuits constructed on the dielectric substrates ensure circuit stability avoiding spurious oscillations during static characteristic measurement.

Abstract: The elementary adder, as far as carry propagation is concerned, has two circuit branches: the first is an inverter (II) followed by a transfer gate (T1, T2) activated when two operands have opposite logic levels, in which case it transfers complemented input carry Cin to the output CoutN; the second consists of a 4-transistor series cirucit, two P-MOS (T3, T4) and two N-MOS (T5, T6) geenrating carry output CoutN complemented when the two operands have equal logic levels.

Abstract: A device for coupling single-mode optical fibers, wherein light radiation outside the fibers is transmitted through a collimated optical beam, obtained by a two-lens array facing the fiber ends. Optimal coupling is obtained by translating a third lens and by rotating a small glass plate placed between the collimating lenses.