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: 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 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.

Abstract: A high speed digital signal transceiver in CMOS technology, in which the receiver has a clock signal extraction circuit, which is capable of self-aligning on incoming data with no spurious locks. Utilizing the PLL technique, the circuit generates a clock signal locked to the incoming signal utilizing a local oscillator, voltage-controlled by two feedback loops, a main one for frequency and phase corrections and a secondary one for phase correction. Moreover, original circuit solutions for the phase detectors and the low-pass filters are also envisaged.

Abstract: Within an optical ATM node, an ATM cell to be synchronized is sent into a segment of pre-determined length of an optical fiber with a high time dispersion (FD), after having been associated, in a tunable wavelength converter (CL), to an optical carrier with a wavelength that is different from that with which the cell itself was received and such that, as an effect of the transit the fiber (FD), the cell reaches the input side of a switching element (Eml . . . Emh) of the node (NC) at a predetermined instant.

Abstract: A method and device are provided for measuring the viscoelastic characteristics of polymeric coatings of optical fibers directed on a coated fiber. The ends of the fiber are inserted into a pair of clamps which are shaped in such a way as to hold the coating without tearing it and to allow it to slide longitudinally over the fiber. The clamps impart a relative oscillating motion to the coating creating a longitudinal tensile stress of periodically varying intensity. The clamps and their support are part of a rheometer which measures the opposing stress and processes the stress data to give the desired characteristics.

Abstract: A speech recognition apparatus in which the speech signal is digitalized and subjected to special analysis, word end detection is effected by energy analysis of the speech signal and the recognition system utilizes a Markov model in combination with a neural network learning by specific training steps.

Abstract: An optical processing device for light radiation provides non-linear transfer functions in an optical guide. A coupled quantum well modulator is reverse biased by an adjustable dc voltage source through an impedance and light radiation to be processed is sent in parallel with the layers composing the modulator guiding zone. The coupled quantum well modulator has a multiplicity of layers including some which form a guide zone comprised of a sequence of alternating quantum wells and barrier layers. The light radiation to be processed passes parallel to the layers through this guiding zone.

Abstract: A flow of ATM cells to be cross-connected performs two consecutive passes through the connection network (PX) of a node. In the first pass the virtual channels of the input virtual paths (A, B, C) are distributed among intermediate virtual channel bundles (A' . . . C"') each with an overall peak bandwidth equal to that of the virtual path of origin of its contributing channels; between the first and the second pass, the virtual channels are cross-connected and the related cells are temporarily memorized, and at the same time the cell flow to be associated to an output virtual path is shaped; and in the second pass the virtual paths are cross-connected, Temporary memorization and shaping are accomplished in a device (SMS) connected between the outputs and the inputs of the connection network (PX) of the node.

Abstract: Ultra-short transform-limited optical pulses, to be utilized for high bit-rate transmission systems, are obtained through direct modulation of a semiconductor laser by pulses of such duration as to excite only the first peak of the relaxation oscillations of the cavity of laser, tuned to such a length that the pulse portions that overlap inside the cavity interfere constructively. The pulses emitted by the laser then pass upon a fiber with high negative dispersion to compensate for the phase effect due to the chirp.

Abstract: Power control in a base to mobile link of a mobile radio system is effected by measuring the carrier/interference ratio at each mobile station and transmitting information thereof, usually in terms of the inverse of that ratio, to the base station. Power is shared between the traffic channels which are active by assigning fractions thereto utilizing a power control factor as the coefficient typical of the channel and depending on the ratios for all of the stations, on the number of active channels, on whether or not there have been variations in the active channels relative to a preceding interval and on the power assigned to the channel in the preceding interval.