Abstract: An integrated circuit for manipulating digitized video sequences is provided, for use in a system for transmission and reception of compressed video sequences to perform, possibly with the aid of an external memory, reordering, format conversion, prediction and motion compensation on the pictures in a sequence. The device has memory for temporarily storing sequences to be manipulated and data read from the external memory; a circuit for decoding information about the manipulations to be performed; address circuitry for transferring the data between the device and the external memory; circuitry for configuring the device by means of a remote processing unit; circuitry for processing the data read from the external memory; and circuitry for arranging the output sequences in the format required by the function to be performed. A controller may control, supervise and set up the functions to be performed.

Abstract: A method of and an apparatus for measuring return loss in an optical fiber component. Radiation of a predetermined wavelength, e.g. from a laser, is launched into an optical fiber component, preferably through an optical fiber having a polarization control loop and the radiation reflected and the direct radiation are subjected to phase modification. An amplitude of the frequency component of the detected signal at the frequency imposed by phase modulation is measured and is used as the basis for evaluating the return loss.

Abstract: Transform-limited ultrashort optical pulses are obtained by sending into a dispersion-shifted optical fibre pulses of such duration and intensity as to produce self-phase modulation. The pulses are also made to travel through a conventional fibre with suitable dispersion and are subjected to optical filtering, so as to compensate, for a particular peak power, the phase effect due to the chirp. Pulse peak power is selected so as to coincide with the vertex of the parabola plotting the square of the duration of the outgoing pulse versus the peak power of the incoming signal.

Abstract: A multi-mode, typically triple-mode, cavity (1), for waveguide band-pass filters is disclosed, which cavity requires no tuning or coupling screws and rounded. The cavity comprises a waveguide element such as an iris (IR1) or a waveguide segment (CR2) arranged in a generically eccentric position with respect to the general development of the cavity and in particular to the main axis (Z) of the same. The cavity may be used to make narrowband filters for satellite communications. A filter comprising cavities (1) of the type described can be designed entirely using an electronic computer and requires no calibration procedure.

Abstract: The optical add/drop multiplexer has a pair of nominally identical interference filters, one of which carries out the function of extracting a carrier from a wavelength division multiplexed stream and the other the insertion function. The filters are arranged in parallel planes and are secured to opposite faces of a transparent plate so that the stream exits the device after having undergone reflection by both filters. The plate is mounted on a support which can be rotated in either direction to vary the tuning wavelength of the filters.

Abstract: The cavity has at least one waveguide segment with elliptical cross section whose axes are arranged at a given inclination angle (.alpha.) with respect to the polarization of the incident TE field. Thus a dual-mode cavity is realized, with the ability to let resonate two transverse fields (TE) with polarization planes orthogonal to each other. By adding a waveguide element able to introduce a non-axial discontinuity, a triple-mode cavity is obtained, allowing for an additional longitudinal mode to resonate as well.

Abstract: The serializing-parallelizing circuit comprises, on a single integrated circuit chip (IC), a transmitter (TX) which performs the parallel-to-series conversion of the data stream, the insertion into the serial stream, with a pre-set periodicity, of a synchronism word, and the line coding of the serial stream, and a receiver (RX) in which clock signals synchronous with the data stream are extracted from a serial stream of coded data and in which the data are decoded and the decoded signals undergo series-to-parallel conversion. The transmitter (TX) and the receiver (RX) can be configured to operate with 4 or 8-bit parallelism.

Abstract: A duct for housing cables for underground telecommunications networks has one or more tubular elements of a first plastic material, having helical ribs on their inner surface. The ribs may also be formed as inserts into the material of the tubular element.

Abstract: A synthesis method in which that part of each interval of the original signal which contains the fundamental information is left unchanged, and only the remaining part of the interval is altered. In this way, not only is processing time reduced, but the natural sound of the synthetic signal is also improved. The main part of the interval is an exact reproduction of the original signal. At least the waveforms associated to voiced sounds are subdivided into a plurality of intervals, corresponding to the responses of the vocal duct to a series of excitation impulses of the vocal cords, synchronous with the fundamental frequency of the signal. Each interval is subjected to a weighting. The signals resulting from the weighting are replaced with a replica thereof shifted in time by an amount that depends on a prosodic information. The synthesis is then carried out by overlapping and adding the shifted signals.

Abstract: The modification is accomplished on the basis of the solution known as spectral inversion (or optical phase conjugation). The device (1) comprises a medium, such as typically a dispersion shifted optical fiber (4), into which the signal to be modified is injected together with a pump signal at such a level as to induce modulation instability in the fiber (4). At the output of fiber (4) a spectrally inverted optical signal is available, which signal is translated in wavelength and is obtained with high conversion efficiency. Preferably, in order to avoid stimulated Brillouin scattering, the pump signal is subjected to spectrum broadening, for instance by means of a modulator (5).

Abstract: A method of speeding up the execution of a wide class of neural networks for processing input signals evolving slowly through time, such as, for instance, voice, radar, sonar, video signals, and which requires no specialized, costly or hard-to-find hardware. The method requires storing, for the neurons in at least one level of the network, the activation value at a certain instant and comparing it with the one computed at the subsequent instant. If the activation is equal, the neuron carries out no activity, otherwise it propagates the difference in activation, multiplied by the interconnection weights, to the neurons it is connected to.

Abstract: Dual-mode cavity of waveguide bandpass filters, which allow the realization of narrow-band filters with very limited transition band and extremely low losses, without tuning or coupling screws or smooth edges. The dual mode cavity is composed of three coaxial sections of waveguide arranged in cascade and provided with irises, of which the two end sections are suited to support two modes with orthogonal polarizations and the intermediate section, consisting of a rectangular waveguide, has its side tilted with respect to the plane on which the irises lie. The whole filter composed of these cavities can be entirely designed by means of a computer and requires no tuning operation.

Abstract: The nonlinear optical element for extremely high bit rates comprises a plate made of semiconductor material, in which is there is realized a sequence of variously doped layers, which can be passed through, in operation, by one or more light radiations. The element comprises a sequence of structures which exhibit excitonic nonlinearities, and which are placed geometrically close to layers of larger sizes, which act as dilution/recombination tanks for the carriers eliminated by the nonlinear structures. The element allows realization of optical devices, such as memories, directional couplers, switches, etc., in which fast excitonic nonlinearity is very evident and in which carriers are eliminated in time intervals of 1 to 10 ps, so that the devices are able to function at extremely high bit rates. (FIG.

Abstract: The circuit for clock signal extraction from a high speed data stream which allows a rapid attainment of the identity between the frequencies of the locally generated clock signal and of the data signal, even when such frequencies are very different. The circuit can easily be inserted into a more complex CMOS digital integrated circuit, it has low power dissipation and is capable of operating at bit rates exceeding 300 Mbit/s. The circuit has a main phase locked loop, which controls a voltage controlled oscillator by continually controlling its phase and a secondary loop, which allows the main loop to become locked, by causing the voltage controlled oscillator to oscillate at a frequency close to the operating frequency.

Abstract: The amplifier is made up of two active or guide amplifiers placed respectively before and after a gain clamped semiconductor amplifier brought to stimulated emission conditions, which acts as pump radiation source for the two active fiber or guide amplifiers.

Abstract: The method allows performing the multiplexing of audio-visual streams, coded according to standard MPEG1, to be sent to remote equipment where demultiplexing and decoding occur. The method takes into account the trend of the occupancy of the input buffers of the remote decoders in order to avoid possible underflow or overflow conditions. For this purpose a multiplexed stream is constructed, composed of packets of variable sizes, by choosing the streams on the basis of the urgency to receive data that the demultiplexing buffers BDi have in order not to become empty.

Abstract: A train of transform-limited optical pulses with wavelength close to the zero-dispersion wavelength of the fiber and high and variable peak power, such as to give rise to self-phase modulation, is sent into a fiber. The spectral broadening of the signal exiting the fiber is measured for a number of values of the peak power of the pulses and the nonlinear refractive index is obtained from the angular coefficient of the straight line representing spectral broadening versus peak power.

Abstract: A light beam is sent onto a wafer, at different angles of incidence, thus giving rise to fluctuations in the transmittance of the wafer, as the angle of incidence varies, because of interference due to multiple reflections of the beam inside the wafer. The transmittance of the wafer is measured as the angle of incidence varies. The angular positions of transmittance maxima and minima are determined with respect to a maximum or minimum corresponding to normal incidence. The refractive index is obtained from these positions and from the number of maxima and minima in the different angles.

Abstract: Fluoride glass optical fibers are fabricated by minimizing the number of high-temperature operations. A tube comprising an external layer of a first fluoride glass of composition suitable to form the cladding of the fiber and an internal layer of a second fluoride glass of composition suitable to form the core of the fiber is prepared by a conventional rotational casting technique. Then, the internal layer is thinned by means of chemical etching at ambient temperature until the attainment of a ratio between the volumes of the two layers that corresponds to the ratio between the core and cladding diameters required for a single mode fiber, and the resulting tube is drawn.

Abstract: In a ring network communication structure for communication on an optical carrier (3A, 3B), a plurality of nodes (2A, . . . , 2E) are interconnected by means of connections comprising at least a first (3A) and a second (3B) optical carrier, such as an optical fiber. Transmission occurs on the ring according to a WDM scheme, by utilizing a first wavelength (.lambda..sub.1) for communication in one direction on the first carrier (3A) of said pair, while communication in the opposite direction occurs by employing a second wavelength (.lambda..sub.2) on the other optical carrier (3B). In the presence of a failure on one of the connections, the nodes adjacent (2B, 2C) to the failed connection reconfigure themselves to ensure the continuation of communication on the alternative path provided by the ring, by utilizing the first wavelength (.lambda..sub.1) on the second carrier (3B) and the second wavelength (.lambda..sub.2)on the first carrier (3A). Preferential application to SDH optical fiber ring networks.