Abstract: A method of manufacturing dichroic antenna structures, which makes use of a projector mounted on the mobile arm of a computer-controlled machine to project the shape of selective antenna elements on the surface of an insulating layer, clad with a metallic layer covered in turn with a photographic emulsion. Development and chemical etching of the excess conductive parts are then carried out.

Abstract: A circuit for automatically controlling the gain-bandwidth product of operation amplifiers, where gain-bandwidth product (G*B) of one of the amplifiers placed on the same chip as the amplifiers to be controlled is measured and the resulting signal is used to control through a bias circuit the gain-bandwidth products of all the amplifiers, the value of these products being presettable through the frequency of a control signal sent to the circuit input. The reference amplifier is highly compensated for and placed in the configuration of voltage follower.

Abstract: The method of measuring viscosity of a glass body, such as an optical preform related to at least its softening temperature, exploits the scattering effects the body introduces into a substantially monochromatic radiation passing through it; more particularly, the width of the spectral line due to Brillouin scattering is measured. The temperature of the body can also be determined by measuring the width of the line generated by Rayleigh scattering. The method is of particular interest for measurements on glasses.

Abstract: The distributed temperature sensor employs an optical fiber as sensing element located in an ambient or near a body of which the temperature is to be monitored or measured. A source of light pulses sends into the fiber, pulses of predetermined duration. The backscattered radiation is collected for each pulse and the frequency spectrum variations in the backscattered radiation with respect to the incident radiation are analyzed. A computer obtains the temperature from said variations. The source and the spectrum variation analyzer are part of an optical time domain reflectometer which allows the temperature information to be associated with the information on the position of the backscattering point along the fiber.

Abstract: The control unit detects the errors concurrently with normal microinstruction execution through suitable internal checking circuits and a determined microinstruction allocation in the memory. Microinstructions comprise additional fields (CS, FS) carrying the encoding, in Modified Berger code, of the allocation address of the microinstruction itself and of the following one. The microinstructions of destination of conditional jumps are allocated so that their codes are related to each other by simple logic relationships which are then reproduced by an internal circuit (CSM). The two fields, the one of the next microinstruction being duly delayed, are then compared and possible differences represent unidirectional and incorrect sequencing errors. The other errors are detected through particular implementations of some internal circuits (STK1, INC1) and duplication of others (RCT, SEL).

Abstract: Optical-fiber transmission system with heterodyne coherent detection in which, at the transmitting side, the polarization of an optical carrier is modulated, and at the receiving side the beam resulting from a combination of the modulated beam and a beam emitted from a local oscillator is split into two orthogonally-polarized components. The two optical signals are detected and sent to an electronic mixer which receives the two components and carries out a synchronous demodulation eliminating the effects of the linewidth of the source and of the local oscillator.

Abstract: In order to prevent an uncontrolled collapse of a quartz tube whose inner surface is being coated with a vitrifiable substance in making a preform or parison of an optical fiber, one or more streams of carrier gas entraining the ingredients of the coating substance through the quartz tube are supplemented by a stream of supplemental carrier gas whose flow is being continuously controlled to keep the overall mass-flow rate substantially constant. The outer tube diameter is photoelectrically monitored and incipient changes thereof are compensated by controlling a flow of additional carrier or inert gas which does not pass through the tube but joins the traversing gas flow at the tube outlet, inside a solids separator with a restricted exit aperture, to modify the pressure differential across the tube wall.

Abstract: According to the coding method, the digital speech signal is split into subbands; each subband is coded independently of the others. The first two subbands undergo an adaptive linear prediction operation yielding a residual, normalized with respect to a quantized r.m.s. value; the residual samples are quantized and coded by a variable bit number. As to the third subband the samples normalized with respect to a quantized gain term are directly quantized and coded by a variable bit number. While splitting the subband signals into sample blocks, for the first two subbands the coefficient vectors of subband linear prediction filters relevant to each block are also determined by vector quantization and linear prediction inverse filtering operations; quantized r.m.s. values are also determined to calculate the numbers of bits permitting subband signals coding. The coded signal consists of subband signal quantization level indices, of r.m.s.

Abstract: An integrated circuit selectively programmable to form an active filter without external circuit components, the integrated circuit having 2.sup.m amplifying modules where m is an integer between 2 and 4, inclusive, p resistive matrices where p is 1 when m is other than 4 and is 2 when m=4, and a bias circuit, r of the amplifying modules being positioned in a first column separated from a second column of r amplifying modules by a respective one of the resistive matrices, where r=4 when m is other than 2 and r=2 when m=2, the second column of amplifying modules being separated from a third column of 4 amplifying modules when m=4 by a second of the resistive matrices.

Abstract: The method of and the device for digital signal coding by vector quantization exploit representation of signal portions in a one-dimensional space for vector codebook generation and for coding for transmission and/or storage purposes. The n-dimensional sampling is transformed into coordinates in one-dimensional space preferably in accordance with Hilbert's curve.

Abstract: This method provides a filtering of digital samples of speech signal by a linear-prediction inverse filter, whose coefficients are chosen out of a codebook of quantized filter coefficient vectors, obtaining a residual signal subdivided into vectors. The weighted mean-square error made in quantizing said vectors with quantized residual vectors contained in a codebook and forming excitation waveforms is computed.The coding signal for each block of samples consists of the coefficient vector index chosen for the inverse filter as well as of the indices of the vectors of the excitation waveforms which have generated minimum weighted mean-square error. During the decoding phase, a synthesis filter, having the same coefficients as chosen for the inverse filter, is excited by quantized-residual vectors chosen during the coding phase (FIGS. 1, 2).

Abstract: Outgoing light signals from a virtual point source are transmitted to a confronting end of an optical fiber via a microlens, whose diameter approximately equals the fiber diameter, axially traversing a center hole of a large-diameter circular photodetector illuminated by incoming light signals from the same fiber end. A focusing lens or objective may be interposed between that fiber end and the photodetector with its microlens to create a field of parallel rays therebetween. The photodetector may be angularly subdivided into a plurality of sectoral portions which are electrically interconnected in series for producing an increased output voltage.

Abstract: A static interferometric ellipsometer, wherein a source (3) generates a coherent light-beam with two monochromatic radiations at slightly different frequencies. A first photodetector (6) generates a first beat between the two radiations, to be used as reference. A second photodetector (9) generates a second beat between the two radiations, after they have been polarized in perpendicular planes and separated so that one of them is reflected onto the photodetector (9) by the sample under test (1,2). A measuring and computing system (11) determines the optical properties of said sample starting from the intensity of the second beat and from the relative phase between the two beats.

Abstract: The digital phase-locked loop circuit extracts the clock signal from a serial flow of coded data by operating so as to determine the phase of the received signal and comparing this phase with that of a locally-generated signal. The error signal obtained from the comparison is digitally filtered and used to correct the phase of local signal. The error with respect to the signal extracted from a prior data stream is stored and used to effect corrections even in the absence of the data flow at the input or in presence of long zero sequences.

Abstract: Mode field radius in single-mode optical fibers is measured by the modulation of an optical beam by means of a spatial filter with radial-distribution of transmittivity of Gaussian type. Modulated beam intensity is measured in correspondence with the beam axis for different widths of the Gaussian curve, and the mode field radius is derived from both such intensity values and a parameter dependent on the Gaussian width.

Abstract: A constant force perpendicular to the fiber axis is applied to the fiber and is displaced step by step along the fiber axis. The state of polarization of a radiation outgoing from the fiber is determined at each step and the beat-length values are obtained from both the amplitude ratio and the phase difference between the components, along the two birefringence axes, of the electrical field associated with a radiation launched into the fiber.

Abstract: The device obtains several characteristic parameters from a standard sentence said by a speaker and compares them with average parameters of the same speaker stored in an internal memory and previously calculated. According to the comparison, it obtains a probability value that the sentence spoken belongs to that speaker and compares the value with a threshold normalized to the average parameter variance by a threshold calculation circuit. If the threshold is overcome, the device considers the speaker verified. A circuit determines the real instants of sentence beginning and end using a noise-adaptive threshold in order to limit between these two instants the time interval over which characteristic parameters are to be calculated. A circuit aligns as to time the characteristic parameters just calculated to the parameters of a reference sentence, obtaining standard lengths of the sounds composing the sentence spoken.

Abstract: A method of making optical performs from which optical fibers are drawn after collapsing of the preform, which comprises depositing by a vapor-phase reaction a plurality of layers on the inner surface of a support tube and controlling the temperature profile around the perimeter of the support so that the thickness of the deposit varies between at least one maximum and at least one minimum. Upon collapse of the support this gives rise to a core having a noncircular cross section.

Abstract: The method allows the production of silica and dopant with reactions among gaseous chemical compounds. The optical fibers produced do not present dip and exhibit low attenuation. Carbon dioxide is used as the oxidizer and organometallic aluminum compounds are used to obtain the dopant; silica is obtained from organometallic silicon compounds or silicon tetrachloride.

Abstract: The method provides the use, for the determination of the estimation echo-channel pulse response, of digital filtering techniques of the transversal adaptive type, and the subdivision of the pulse-response of the equivalent echo channel into three intervals, the second of which consists of the significant portion of the pulse response and is determined by the iterative search for the value and the position of the coefficient of maximum absolute value; the first interval corresponds to a pure delay and the third corresponds to the contribution given by the lowest frequencies of the base band. To copy the echo-signal, there are only considered the pulse-response coefficients whose indexes are comprised in the second interval, and the samples of the signals to be copied belonging to preceding sampling instants, whose indexes are also comprised in the second interval.