Patents Assigned to British Telecommunication, plc
  • Speed estimation
    Patent number: 5396253
    Abstract: A system and method of speed estimation for a cellular radio network includes a number of speed estimation units. Each unit comprises an averaging window of a different duration, a buffer store and variance calculator. The duration of each window is equivalent to the time taken by a mobile unit to traverse a distance of 20 wavelengths of the received signal at a particular speed. An incoming signal is applied to the units. The duration of the window determines the significance of the fast fade components in the signal which is related to mobile unit speed. When the average of a window is substantially constant, the speed corresponding to that window can be assumed to be achieved or exceeded. Decision logic is arranged to poll the outputs of the variance calculators to derive a speed estimation indication.
    Type: Grant
    Filed: March 22, 1993
    Date of Patent: March 7, 1995
    Assignee: British Telecommunications plc
    Inventor: Si T. S. Chia
  • Lossless optical signal splitter including remotely pumped amplifier
    Patent number: 5323474
    Abstract: A lossless optical component includes an input and at least one output. The optical component includes an operational portion and an amplifier portion upstream of the operational portion. The amplifier portion includes an optical amplifier for amplifying optical signals received by the input. The optical amplifier is provided with input optical waveguide via which the optical amplifier is optically pumpable by a remote pump laser. The output of the optical amplifier is proportional to the loss of the operating portion of the optical component.
    Type: Grant
    Filed: July 9, 1992
    Date of Patent: June 21, 1994
    Assignee: British Telecommunications plc
    Inventors: Stephen Hornung, Christopher Rowe
  • Duplex data transmission
    Patent number: 5289459
    Abstract: A duplex data transmission system in which a station can vary its transmission power to keep the signal-to-noise ratio the same in each direction or, in a system employing a different data rate in each direction, to keep the two ratios in a fixed relation to one another. In an initial training sequence, each station measures "talker echo" from its own transmission, and subsequently measures noise from the other station's transmission. The other station then makes the same measurements. The noise data thus collected is sent by both to a control circuit in one or other station which calculates from both sets of data an adjustment (e.g. a reduction) of the power to be transmitted. One or other stations then accordingly reduces power.
    Type: Grant
    Filed: May 31, 1989
    Date of Patent: February 22, 1994
    Assignee: British Telecommunications plc
    Inventor: John D. Brownlie
  • Preparing substrates by annealing epitaxial layers in the form of nesas and substrates so prepared
    Patent number: 5279687
    Abstract: In order to grow single crystal, solid state devices onto a mismatched substrate, a secondary substrate is obtained by growing an epilayer divided into mesas (21) onto the primary substrate. The epilayer is annealed and this relieves the strain and causes dislocations to terminate preferentially on the sides of the mesas.
    Type: Grant
    Filed: September 12, 1991
    Date of Patent: January 18, 1994
    Assignee: British Telecommunications PLC
    Inventors: Christopher G. Tuppen, Christopher J. Gibbings
  • Tape-automated bonding of integrated circuits
    Patent number: 5223321
    Abstract: A tape for use in tape-automated-bonding of integrated circuits is disclosed. A series of interconnection arrays ("frames") are arranged along the tape, each array being formed by a number of interconnection beams 3. A terminal ("bump") 6 is located on each beam 3 for bonding to a respective interconnection pad 7 of an integrated circuit 8. Conventional bumps are made of gold-plated copper and have uneven and unyielding bonding surfaces which can fail to provide consistent bonds. The bumps 6 of the tape disclosed comprise a conductive material having a Vickers hardness number of 55 or less, and thus have a compliance which facilitates more even bonding. A method of producing the tape is also disclosed.
    Type: Grant
    Filed: October 15, 1991
    Date of Patent: June 29, 1993
    Assignee: British Telecommunications plc
    Inventors: F. Nihal Sinnadurai, David J. Small, Alexander A. Blain, Kenneth Cooper
  • Optical detector with integral filter and having Fabry Perot resonator system
    Patent number: 5216237
    Abstract: An optical detector such as a pin photodiode or avalanche photodiode is provided with an integral dielectric filter (8). The optical filter (8) preferably comprises a plurality of layers of silicon and silicon monoxide. If the detector is a PIN diode, the filter (8) may be provided on the underside of a substrate (1) before growth of the diode is commenced on the other side.
    Type: Grant
    Filed: September 17, 1991
    Date of Patent: June 1, 1993
    Assignee: British Telecommunications, plc
    Inventors: Simon Ritchie, Paul C. Spurdens, Mark D. Learmouth
  • Binary tree switching network
    Patent number: 5212587
    Abstract: A binary tree switching network in which the switching states are configured to switch an input signal from a selected input to an output by means of a control code set having a minimum Hamming distance (d) greater than one which eliminates cross-talk of order (d-1) and less. Such a network may be used for switching optical signals by means of optical beam deflector stages, each having a variable polarization rotator and a polarization sensitive deflector. Elimination of first order cross-talk is readily achieved by a modification stage arranged to receive a single input from the preceding stages and to pass it to the output.
    Type: Grant
    Filed: December 27, 1990
    Date of Patent: May 18, 1993
    Assignee: British Telecommunications plc
    Inventor: Peter Healey
  • Square optical pulse generator
    Patent number: 5208455
    Abstract: An all-optical fibre Sagnac antiresonant interferometer (2) is formed from an optical fibre having a non-linear refractive index. The coupler (8) is a dichroic coupler coupling equal portions of a cw optical signal at 1.53 .mu.m from laser (16) to ports (14 and 16) and all of a pulsed optical signal from laser (20 ) to port (14). The intensity of the pulsed optical signal is sufficient to provide a relative phase shift in the counter propagating 1.53 .mu.m signals. The loop (6) is longer than the inverse of the absolute difference in group delays of the cw and pulsed optical so causing a square optical pulse at 1.53 .mu.m to be switched to port (12) of the coupler.
    Type: Grant
    Filed: March 25, 1992
    Date of Patent: May 4, 1993
    Assignee: British Telecommunications plc
    Inventors: Brian P. Nelson, Keith J. Blow, Nicholas J. Doran
  • Optical filter tuning apparatus and an optical filtering method
    Patent number: 5193027
    Abstract: An optical filter tuning apparatus and filtering method uses an optical filter that reflects light of a predetermined wavelength which is dependent on the position of incidence of the light on the filter and a retroreflector moveable with respect to the filter and which reflects light from an optical source to the position of incidence and reflects light of the predetermined wavelength from the filter to an optical receiver.
    Type: Grant
    Filed: August 14, 1991
    Date of Patent: March 9, 1993
    Assignee: British Telecommunications plc
    Inventor: Keith R. Preston
  • Holographic element
    Patent number: 5164847
    Abstract: A transmission holographic element (30) comprises a holographic material (330) deposited onto a substrate (31) to form a composite substrate structure. The substrate (31) is coated with a mirror coating (32) prior to the deposit of the holographic material (33) which is reflecting at the reading wavelength and non-reflecting at the recording wavelength. This allows the use of substrates that need not be of good optical quality because when the holographic element is exposed to light at the reading wavelength, light is reflected by the mirror coating before passing through the substrate. In addition, the mirror coating is protectred from damage during processing since it is between the substrate (31) and holographic material (33).
    Type: Grant
    Filed: June 20, 1991
    Date of Patent: November 17, 1992
    Assignee: British Telecommunications plc
    Inventors: David J. McCartney, Giles R. Chamberlin
  • Laser systems
    Patent number: 5157683
    Abstract: The invention relates to laser systems of the type comprising optical fiber amplifiers. A laser system comprises a first laser 1 and a second laser 2. The second laser 2 is pumped at a first wavelength .lambda..sub.1 and caused to lase at a second wavelength .lambda..sub.2. The first laser 1 has absorption bands .lambda..sub.1 and .lambda..sub.2. The output .lambda..sub.2 of laser 2 and the remnant pump at .lambda..sub.1 are coupled and both are used to pump the first laser 1, thus causing laser 1 to lase at a third wavelength .lambda..sub.3.
    Type: Grant
    Filed: March 5, 1991
    Date of Patent: October 20, 1992
    Assignee: British Telecommunications plc
    Inventors: Colin A. Millar, Jonathan R. Armitage
  • Telephone handset
    Patent number: D339131
    Type: Grant
    Filed: January 21, 1992
    Date of Patent: September 7, 1993
    Assignee: British Telecommunications plc
    Inventor: Guy E. Desbarats
  • Videophone base
    Patent number: D342247
    Type: Grant
    Filed: April 28, 1992
    Date of Patent: December 14, 1993
    Assignee: British Telecommunications plc
    Inventor: Guy E. Desbarats
  • Video conference cabinet
    Patent number: D342517
    Type: Grant
    Filed: January 15, 1992
    Date of Patent: December 21, 1993
    Assignee: British Telecommunications plc
    Inventor: Peter T. Bosson
  • Telephone base
    Patent number: D344083
    Type: Grant
    Filed: January 21, 1992
    Date of Patent: February 8, 1994
    Assignee: British Telecommunications plc
    Inventor: Guy E. DesBarats
  • Telephone handset
    Patent number: D344272
    Type: Grant
    Filed: January 21, 1992
    Date of Patent: February 15, 1994
    Assignee: British Telecommunications plc
    Inventor: Guy E. Desbarats
  • Transition pattern between opaque border and transparent screen surface for video screen
    Patent number: D346604
    Type: Grant
    Filed: November 29, 1991
    Date of Patent: May 3, 1994
    Assignee: British Telecommunications plc
    Inventor: Peter T. Bosson
  • Video Conference camera screen
    Patent number: D346605
    Type: Grant
    Filed: December 20, 1991
    Date of Patent: May 3, 1994
    Assignee: British Telecommunications plc
    Inventor: Peter T. Bosson
  • Video conference screen
    Patent number: D348069
    Type: Grant
    Filed: November 29, 1991
    Date of Patent: June 21, 1994
    Assignee: British Telecommunications plc
    Inventor: Peter T. Bosson
  • Telephone handset
    Patent number: D354061
    Type: Grant
    Filed: January 21, 1992
    Date of Patent: January 3, 1995
    Assignee: British Telecommunications plc
    Inventor: Guy E. Desbarats