Patents Represented by Attorney, Agent or Law Firm Aprilia U. Diaconescu
  • Patent number: 5835369
    Abstract: A power factor and crest factor correction circuit for a power distribution network of the type comprising a low power source for supplying a plurality of ports with an ac signal is disclosed. Each port comprises a rectifier bridge, a bulk storage capacitor and a power converter connected across the rectifier bridge, The power factor and crest factor correction circuit comprises an inductor, series connected between the rectifier bridge and the bulk capacitor, for reducing the current peaks in a rectified signal received from the rectifier bridge. The correction circuit also comprises diode means connected in parallel across the inductor for discharging the bulk capacitor whenever the voltage across the bulk capacitor exceeds the voltage of the rectified signal. As a result, a higher power factor is obtained for the dc signal applied to the power converter, and also the current peaks in the dc signal are substantially reduced.
    Type: Grant
    Filed: July 8, 1997
    Date of Patent: November 10, 1998
    Assignee: Northern Telecom Limited
    Inventor: John Bottrill
  • Patent number: 5822094
    Abstract: In an apparatus and method for troubleshooting a transmission system comprising optical line amplifiers (OA), optical reflections can be detected irrespective if a data signal is present or absent. Each OA is equipped with a self-stimulation signal detection unit for generating a low frequency local code unique to the transmission system and dithering the outgoing signal in a controlled manner with the local code. Each OA attempts to detect its local code in the incoming signal by comparing the energy of the transmitted and received dithers. The presence of the local code in the incoming signal initiates alarms which unequivocally identify the faulted OA. Each OA selects its local code out of a bank of local codes, according to a priority scheme and re-selects its local code in case of conflicts.
    Type: Grant
    Filed: September 5, 1997
    Date of Patent: October 13, 1998
    Assignee: Northern Telecom Limited
    Inventors: Maurice Stephen O'Sullivan, Kim Bryon Roberts, James St. Leger Harley, Jeffrey Alan Weslowski
  • Patent number: 5774242
    Abstract: A performance evaluation analysis for optical transmission systems is disclosed. A reference eye mask is defined for a transmitter and for a reference optical transmission link. The quality of the transmission for a live path is determined by applying the reference eye mask on the eye diagram of the electrical signal recovered at a point of measurement with a distortion measurement unit. The point of measurement could be established at a receiver optical connection plane, for measuring the optical transmission link and transmitter penalty, or could be at the optical connection plane of a transmitter, for measuring the performance of the transmitter. The optical path may include optical amplifiers, dispersion compensating modules, active and passive components.
    Type: Grant
    Filed: January 15, 1997
    Date of Patent: June 30, 1998
    Assignee: Northern Telecom Limited
    Inventors: Maurice Stephen O'Sullivan, Rongqing Hui, Jingyu Zhou
  • Patent number: 5751454
    Abstract: The invention is directed to the use of wavelength channels to bypass nodes in ring networks. For networks with a small number of nodes, direct node to node routes are provided without changing the physical layout of the fibre in the ring. Architectures providing complete transparent interconnections with extra capacity for heavily used routes on a portion of the ring are disclosed. For networks with a large number of nodes, underconnected networks provide a number of accelerated, direct routes between some of the nodes. Proposed architectures for underconnected networks and methods for self-routing the traffic are also provided.
    Type: Grant
    Filed: October 10, 1996
    Date of Patent: May 12, 1998
    Assignee: Northern Telecom Limited
    Inventors: R. Ian MacDonald, Herman W. Willemsen
  • Patent number: 5737109
    Abstract: A method and apparatus for transmitting an analog signal over an optical fiber cable is disclosed. A semiconductor laser provides an optical carrier signal, the laser having the natural linewidth at high power of the same order as the SBS linewidth. The method comprises directly modulating the current of the laser with a dither signal comprising a first component f.sub.C and a second component f.sub.S. Due to the nonlinearity of the "I-V" characteristic of the laser, a thermal modulation component f.sub.T appears in the active region. This thermal modulation component reshapes the spectrum of the semiconductor laser to increase the threshold of the SBS. As a result, the energy of the signal transmitted over the optical cable may be increased by approximately 16 dB. The first frequency is at least twice the maximum frequency of the analog signal and the second frequency is selected to obtain f.sub.C -f.sub.S =f.sub.T.
    Type: Grant
    Filed: January 16, 1996
    Date of Patent: April 7, 1998
    Assignee: Northern Telecom Limited
    Inventor: John Charles Goodwin
  • Patent number: 5708391
    Abstract: A programmable high frequency active filter comprises a plurality of basic building blocks connected in parallel. A basic building block includes a transistor pair connected in a differential amplifier configuration, an impedance connected between the emitters of the transistors and a switching block for applying the necessary bias current to the transistors. The transfer function of the filter is programmed with a digital word, the length of which determines the number of basic building blocks included in the configuration. In this way, the equivalent high frequency impedance of the filter is controlled by selecting the configuration and the value of the impedance of each building block.
    Type: Grant
    Filed: May 2, 1996
    Date of Patent: January 13, 1998
    Inventors: Michael Altmann, Bernard Guay
  • Patent number: 5684805
    Abstract: A microwave multiphase detector for demultiplexing and regenerating data from an incoming data stream includes N data channels and has a data rate R. For recovering data corresponding to a channel M, a detecting unit receives the data stream, detects a sampling phase corresponding to a data transition on channel M and generates a phase width modulated (pwm) pulse, phase modulated with the sampling phase. A digital to analog (D/A) conversion unit converts the pwm pulse to a contributing control voltage and a data regeneration unit provides a recovered data bit for channel (M). The detector is supplied with N variants of a local clock signal with a rate R/N, each variant being phase displaced with .+-.360.degree./N from the adjacent variants. A counterbalancing unit is also provided for each channel, such that if a pwm pulse is indeed generated, the contributing voltage for that pulse is compensated for with a balance pulse of opposed amplitude.
    Type: Grant
    Filed: November 30, 1995
    Date of Patent: November 4, 1997
    Inventor: Anthony Kevin Dale Brown
  • Patent number: 5684294
    Abstract: A proximity detector and ambient light monitor (PALM) is provided, comprising a light source for generating an optical composite signal, a light detector for providing a detected signal, a circuit for separating the ac component from the detected signal, and a switch for providing a control signal when the ac component is outside a preset range. The PALM further comprises an ambient light detector which also receives the detected signal and provides an ambient light level signal. The ambient light detection circuit rejects the signals that relate to the proximity monitoring and provides sufficient gain to overcome daylight filtering lens currently provided on the light detectors. The ambient light monitoring circuit provides either a continuous varying voltage proportional to the ambient light, or a simple binary signal indicating that the light is above a threshold.
    Type: Grant
    Filed: October 17, 1996
    Date of Patent: November 4, 1997
    Inventor: Ross George Kouhi
  • Patent number: 5635880
    Abstract: A microwave differential amplifier comprises a first and a second matched NMOS device, each connected with the source to a common bias node, the gate to an input port for receiving a differential input signal and with the drains to an output port for providing a differential output signal. The Miller capacitors of each device provide the necessary feedback between the input and output ports for shifting the phase of the differential output signal with respect to the phase of the differential input signal with 45.degree. at a predetermined frequency. The operating point of the NMOS devices is maintained in the linear region of the respective transfer characteristic, using matched loads and a corresponding bias current. The loads may be resistors, in which case AGC is used for maintaining a constant bias current, or active loads. A VCO built with four such differential amplifiers in a gyrator configuration oscillates at the predetermined frequency and has eight output signals.
    Type: Grant
    Filed: March 14, 1996
    Date of Patent: June 3, 1997
    Assignee: Northern Telecom Limited
    Inventor: Anthony K. D. Brown