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: A train of rectangular pulses is sent into a fiber, which pulses have such a wavelength that fiber operates under anomalous dispersion conditions, such a peak power as to cause modulation instability in the fiber and such a ratio between duration and repetition period that the average power is lower than the threshold at which stimulated Brillouin effect takes place. The maximum value of instability gain is measured in the spectrum of the pulses exiting the fiber and the Kerr non linearity coefficient is obtained from the maximum measured value of modulation instability gain by minimizing the error, in the range of power values used for the measurement, with respect to a theoretical curve expressing such maximum gain as a function of the peak power. The device to realize the method is also provided.

Abstract: The circuit in CMOS technology allows high speed driving of optical sources, in particular laser diodes, operating efficiently at speeds that meet the requirements imposed by optical fiber communication systems and avoiding interference between driving currents and biasing current in the optical source. The circuit utilizes a bias current generator, a modulation current generator and a cascade of CMOS inverter stages that supplies a driving voltage to the modulation current generator and receives digital signals at its input. It is possible to independently adjust the bias current, so as to allow driving sources with different threshold currents, and to adjust the modulation current.

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.

Abstract: A method and apparatus is disclosed for modulating a laser by a current resulting from the combination fo a threshold current and a current due to a data signal and in which a fraction of the laser output signal is taken and converted into a monitoring current, such monitoring current is sampled, an actual value of the peak power is obtained as an average over a number of samples of the monitoring current, the actual value of the peak power thus found is compared with a desired value of the peak power and an updated value for the laser threshold current is obtained from the difference, if any, between the desired value and the actual value, the updated value being such as to compensate for the difference.

Abstract: The device for the phase realignment of ATM cells in an optical ATM switching node is associated with each input line (Fe) of node and includes a circuit for recognizing the beginning of a cell, a circuit for evaluating the time shift between of a cell and a reference instant and for generating an error signal (ER) depending on the amount of time difference, and a delay line for compensating the time difference, driven by the error signal (ER). The time difference compensator means includes a logarithmic optical delay line that is connected upstream of the device for recognizing the beginning of a cell and for evaluating the amount of the time difference.

Abstract: In a radio communication system, in particular a mobile communication system, variable-rate information flows originating from different sources (CV1, CS1; CV2, CS2) and relative to a same communication are transmitted on a same radio channel. Each mobile station (M1 . . . Mh) and the fixed part (B1 . . . Bn; RNC) of the system comprise a unit for the control of the variable-rate transmission, which dynamically allocates the available bits to the different streams by taking into account the needs of the sources (CV1, CS1; CV2, CS2), the conditions of the channel (6) and the system occupancy. (FIG. 1).

Abstract: The optical switch for fast cell-switching networks comprises an optical interconnection network (CM) and an electrical control network (CT). In order to fully exploit optical component capabilities and to overcome the constraints imposed by operating speed limits of electronic components, each input (IN1 . . . INk) of the interconnection network (CM) is associated with units (PAC1 . . . PACk) forming aggregates of cells which are to follow a same path through the interconnection network and time-compressing the aggregates, and each output (OU1 . . . OUk) is associated with units (PAD1 . . . PADk) for the time expansion of the aggregates and separation of the aggregate cells.

Abstract: The device includes a first and a second optical circulator (C1, C2) having an input port and an output port that are the inputs and the outputs of the switch, as well as an optical bandpass filter (FP) placed between the two circulators (C1, C2) and connected with means for switching its state so that the filter either reflects or transmits a given wavelength, thus allowing a carrier with this wavelength at the input port of one of the circulators (C1, C2) to reach the output port of the same circulator or the output port of the other circulator.

Abstract: Optical demultiplexing system, wherein from an optical carrier modulated by a TDM data flow the wanted tributary is extracted as an optical signal. The system makes use of a semiconductor optical amplifier, whose gain is modulated due to saturation effect. The amplifier receives both the modulated optical carrier and one or a plurality of sampling optical carriers, with wavelengths different from that of the modulated carrier. One or a plurality of optical filters supply at the output the tributaries by extracting from the amplifier output the sampling carriers modulated by data signals.

Abstract: The vapour generator for chemical vapour deposition plants allows the extraction of metalorganic vapours from liquid or solid sources. It mainly consists of a container into which a gas flows in, and as it passes near the reagent, it is saturated with the vapours produced and transports them to the reaction chamber. Only the generator is brought to a temperature which is higher than room temperature so as to obtain a vapour which is saturated with a high quantity of reagent. To avoid vapour condensation in the pipe system transporting it from the generator to the reaction chamber, it is diluted with a carrier gas directly in the body of the heated generator, reducing in this way the condensation temperature of vapour which becomes unsaturated. For this purpose, the generator contains a dilution bypass-line in the upper base into which the carrier gas is made to flow. The pipe system going from the generator to the reaction chamber can be held at room temperature without any condensation risks.

Abstract: The switching element allows building up of ATM exchanges capable of processing cell flows at bit rates higher than 700 Mbit/s. It uses an architecture with output queues, implemented through a unique shared memory, suitably controlled in order to obtain spatial cell switching towards the outputs. ATM cells are converted into a highly parallel format by a structure named rotation memory, where through the cells are then transferred into the master memory. The rotation memory is used also for the inverse operations of format restoration towards the output. The element control circuit is entrusted with the generation of writing and reading addresses of the master memory, in order to carry out the switching proper.

Abstract: A method of adjusting the operation of optical networks in terms of propagation constants of guided modes in integrated optical devices, allowing a considerable number of out of tolerance devices to be recovered by depositing on the surface where the optical guides are manufactured, once the normal fabrication process is completed, a further layer of transparent material of suitable size and refractive index.

Abstract: Apparatus for measuring the effective refractive index in optical fibers, in which a source sends light radiation, the wavelength of which can be varied within a predetermined interval, into a fiber span, and a detector collects the radiation intensity of the radiation collected by the detector as the wavelength varies, in order to determine the oscillation period of the fiber transmittance or reflectivity and to obtain the effective refractive index from such period.