Patents Represented by Attorney Stuart L. Wilkinson
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Patent number: 4415383Abstract: In the manufacture of VLSI (very large scale integrated) MOS (metal-oxide-semiconductor) circuits, a polysilicon gate is deposited on an oxide layer overlaying a silicon substrate. Ideally, the polysilicon gate is made extremely small and with sharply defined vertical boundaries. The invention proposes depositing a polysilicon layer, covering a region of the layer with an antireflective coating, and laser annealing the layer. Laser radiation is absorbed to a higher level by the coated region than elsewhere and consequently the polysilicon layer in this region melts and recrystallizes into large grains. The polysilicon layer is then etched using etch conditions ensuring preferential etching of unrecrystallized polysilicon in comparison with recrystallized polysilicon. Consequently, except at the coated region, the polysilicon is etched quickly and there is very little undercutting of the gate region.Type: GrantFiled: May 10, 1982Date of Patent: November 15, 1983Assignee: Northern Telecom LimitedInventors: Abdalla A. H. Naem, Iain D. Calder, Hussein M. Naguib
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Patent number: 4413881Abstract: A hermetic seal for an optical fiber is fabricated by casting or molding a mass of fusible alloy around the fiber so that the alloy solidifies within a confined space. The alloy used is characterized by low thermal coefficient of expansion, minimal relaxation after solidification, and appreciable expansion as it solidifies, thereby to create a stable pressure contact at its interface with the optical fiber. The solidified mass may be subsequently soldered into a passage through a wall of a fiber optic device package. Alternatively, the mold within which the mass of alloy is encased or molded may, itself, be soldered into the passage.Type: GrantFiled: October 19, 1981Date of Patent: November 8, 1983Assignee: Northern Telecom LimitedInventor: Tibor F. I. Kovats
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Patent number: 4413883Abstract: A matrix multiplexed field effect display has switch devices at matrix crosspoints to provide a turn-on threshold for the field effect material. The switch devices are thin film metal-insulator-metal (MIM) switches. The display is operated at low current so that the MIM switches, which may be deposited on glass, do not degrade rapidly in use.Type: GrantFiled: December 3, 1980Date of Patent: November 8, 1983Assignee: Northern Telecom LimitedInventors: David R. Baraff, Nur M. Serinken, Richard W. Streater, Carla J. Miner, Robert J. Boynton, Blair K. MacLaurin, William D. Westwood
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Patent number: 4404555Abstract: In known thin film switch controlled matrix multiplexed liquid crystal displays (LCD's), alternating pulses of an applied waveform are of reverse polarity. If the transient behaviour characteristic of the switches controlling the LCD is not saturated during application of a selection pulse, the selected pels may experience a relatively low RMS voltage in the ON state. To ensure that selected pels are fully turned on, the addressing waveform proposed consists of a series of pulses of one polarity followed by a corresponding series of pulses of opposite polarity. Transient effects are minimized by applying the series of unipolar pulses and the pels are consequently subjected to a high RMS voltage. However, net DC current through the LC is still zero as required in order to guard against irreversible electrochemical degradation of the LC. The higher RMS voltage can be used to improve contrast ratio or to increase the level of multiplexing.Type: GrantFiled: June 9, 1981Date of Patent: September 13, 1983Assignee: Northern Telecom LimitedInventors: John R. Long, Carla J. Miner, Richard W. Streater, David R. Baraff
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Patent number: 4399541Abstract: A known electro-optic has a semiconductor laser, a temperature sensor for controlling an electrically operated cooler, and an optical fiber end portion anchored close to the laser to receive light from it. Usually the fiber is anchored by a mass of cured epoxy. This invention proposes anchoring the fiber in a mass of fusible alloy which is melted and solidified using a Peltier effect device which is driven with one polarity current to function as a heater and with a reverse polarity current to function as a cooler. Once the package is complete and the laser is operating, the temperature sensor together with the Peltier effect device functioning as a cooler are used to cool the laser.Type: GrantFiled: February 17, 1981Date of Patent: August 16, 1983Assignee: Northern Telecom LimitedInventors: Tibor F. I. Kovats, Tibor F. Devenyi, Christopher M. Look
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Patent number: 4397551Abstract: A discontinuity within an optical fiber is located using a reflectometry technique. A swept frequency sinusoidal signal is launched into the fiber, is reflected from the remote discontinuity, and is returned to the fiber input end. The signal consists of the combined outputs of two optical sources identically frequency modulated and having output wavelengths .lambda..sub.1, .lambda..sub.2 separated by several nanometers. The light at .lambda..sub.1 has a group velocity different from the light at .lambda..sub.2 and consequently, reflected light components at .lambda..sub.1 and .lambda..sub.2 interfere with each other at the fiber input end. The interference signal is frequency dependent and from the frequency dependence the distance from the fiber input end to the discontinuity can be calculated. The received signal is dependent also on the difference in group index at .lambda..sub.1 and .lambda..sub.2, this difference being relatively insensitive to temperature, stress and fiber composition.Type: GrantFiled: October 29, 1981Date of Patent: August 9, 1983Assignee: Northern Telecom LimitedInventors: Marc Bage, Johanne Lemay
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Patent number: 4392931Abstract: Using a sputter deposition system to reactively deposit a material such as an oxide, it is relatively easy to achieve either an oxygen-doped film with appreciable metallic content or an oxide film. However it is difficult with known systems to obtain an intermediate film having an accurately controlled resistivity, transparency, and composition, such films being of much use in semiconductor applications, in displays and in photovoltaic cells. It is now proposed that an apertured barrier be used to accurately fix the flow rate of target material to the substrate and in addition, that reactive gas flow be regulated and directed only to the immediate vicinity of the substrate. In this way the composition of the film can be accurately fixed. By establishing an r.f. field at the substrate, increased dissociation of the reactive gas can be achieved to render the gas more reactive and so enhance certain film properties such as transparency.Type: GrantFiled: March 31, 1981Date of Patent: July 12, 1983Assignee: Northern Telecom LimitedInventors: Shmuel Maniv, William D. Westwood
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Patent number: 4392014Abstract: A splice between ends of a pair of telecommunications cables is encapsulated in a thermoset foam. To encapsulate the splice it is positioned within a mold with the cables extending through apertures in the mold. At the apertures the cables are wrapped with an open cell foam material to block the cavity ends. A foam base material is then mixed with an activating agent which includes both a heat activated blowing agent and a material which reacts exothermically with the foam base material. The mixture is deposited within the mold and the mold closed. The mixture then foams to fill the mold and rapidly cures. The resulting joint is light, durable, waterproof and re-enterable.Type: GrantFiled: April 20, 1981Date of Patent: July 5, 1983Assignee: Northern Telecom LimitedInventors: William P. Trumble, Roger C. Finn, Charles F. C. Jackson
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Patent number: 4389557Abstract: In a method and apparatus for bonding a semiconductor laser chip to a heatsink and testing the bond obtained, temperature in the bonding operation is regulated by passing a small fixed current through the forward biased laser and monitoring corresponding change in voltage caused by alteration of the laser pn junction temperature. Current is passed to the laser through a floating contact consisting of a conducting vacuum pick-up pressed against the laser top surface. Bond integrity is subsequently tested at low temperature by passing a dc current greater than a threshold current through the laser and measuring the resulting light output and then passing a pulsed current with identical peak current level and again measuring light output. The difference in light output is a function of the bond thermal resistance.Type: GrantFiled: August 17, 1981Date of Patent: June 21, 1983Assignee: Northern Telecom LimitedInventors: Tibor F. Devenyi, Tibor F. I. Kovats, Christopher M. Look
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Patent number: 4366488Abstract: A terminal has a reciprocating print head bearing a series of linearly arranged, individually-magnetizable styli for printing on magnetic particle oriented paper. The terminal may be used as a printer, or as a display by combining the printer with an erasing head comprising a series of linearly arranged magnets which create a rotating magnetic field to erase the magnetic particle oriented paper when the erasing head is reciprocated. The print and erase heads are mounted on a common carriage. The terminal is cheap to manufacture and, if used as a printer, has the advantage of reusable paper. If used as a display, it required no refresh.Type: GrantFiled: April 2, 1980Date of Patent: December 28, 1982Assignee: Northern Telecom LimitedInventors: William D. Westwood, Steven Kos, Herman W. Willemsen
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Patent number: 4364639Abstract: A variable attenuation electro-optic device has a lens for collimating light from an input fiber and for focussing light into an output fiber. The optical path of light passing through the device passes through a dynamic scattering liquid crystal cell whose optical transmissivity can be varied by varying an AC electric field applied across it. Reflective and transmissive embodiments are described using one or two lenses of the Selfoc.RTM. type. The applied AC introduces a frequency component into the attenuation which is suppressed to particularly adapt the device for use as an attenuator or enhanced and modulated to particularly adapt the device for use as a modulator.Type: GrantFiled: August 25, 1980Date of Patent: December 21, 1982Assignee: Northern Telecom LimitedInventors: William J. Sinclair, Josef Straus, Philip M. Garel-Jones
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Patent number: 4360372Abstract: A fiber optic system element for reducing speckle and modal noise resulting from coupling a laser diode to an optical fiber has the form of a short length of fiber through which extend filaments of different refractive indices. Such fiber is fabricated by fusing together a plurality of fibers of different refractive index profiles and drawing the resulting preform into a single fiber.Type: GrantFiled: November 10, 1980Date of Patent: November 23, 1982Assignee: Northern Telecom LimitedInventor: Roman Maciejko
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Patent number: 4344173Abstract: Compensation for variation of a semiconductor laser threshold position is based on the utilization of the rectifying property of such lasers near threshold. A small amplitude test signal is applied to the laser close to threshold and a distortion component at a harmonic of the test signal frequency is isolated from a voltage or current analog generated from the laser light output. Depending on the order of the harmonic, the characteristic of this distortion component has a maximum value (even harmonic) or is zero valued (odd harmonic) when the threshold current is applied to the laser. If the laser threshold position changes, a feedback circuit resets the bias current applied to the laser to a value close to but just below, the threshold position. The test signal can also be used to compensate for change in laser slope efficiency to avoid any variation in signal power output at a fixed modulation level.Type: GrantFiled: August 28, 1980Date of Patent: August 10, 1982Assignee: Northern Telecom LimitedInventor: Joseph Straus
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Patent number: 4342944Abstract: A surface emitting light emitting diode (LED) has a reflecting element to redirect light emitted away from the light emitting region towards an exit window. The LED bottom contact is formed over the reflecting element and a current confining path is set up within the LED to funnel current between the top and bottom contacts around the reflecting element and through the light emitting region.Type: GrantFiled: September 15, 1980Date of Patent: August 3, 1982Assignee: Northern Telecom LimitedInventor: Anthony J. SpringThorpe
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Patent number: 4342148Abstract: In the manufacture of double heterostructure laser diodes using liquid phase epitaxy a source crystal precedes the laser substrate crystal through the process to ensure saturation of the various melts from which epitaxial growth is obtained. The source crystal has hitherto been discarded. The source crystal, since it immediately precedes the substrate crystal, also experiences epitaxial growth of a heterostructure but with heterostructure layer thicknesses unsuited for laser diode fabrication. By suitable processing of the source crystal after it is formed with a heterostructure, light emitting diodes can be produced so contributing to a 50% reduction in materials cost.Type: GrantFiled: February 4, 1981Date of Patent: August 3, 1982Assignee: Northern Telecom LimitedInventors: Anthony J. SpringThorpe, Agnes Margittai
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Patent number: 4339628Abstract: A combined supporting arrangement and RF shield for stacked circuit boards has several conducting shields, each shield covering a respective circuit board and having an edge flange, part of the flange being turned under to space a particular circuit board from the next lower circuit board in the stack, and part of the flange being turned out to engage a clamp projecting from a baseboard, the clamp being common to all the shields.Type: GrantFiled: August 20, 1980Date of Patent: July 13, 1982Assignee: Northern Telecom LimitedInventors: Gabriel Marcantonio, David M. Macklem
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Patent number: 4337531Abstract: In a scanning head for an optical disc system, a light beam from a laser is transmitted through a monomode optical fiber and then focussed on a record carrying surface of an optical disc by a converging lens. The end of the fiber can be reoriented within orthogonal planes perpendicular to the plane of the record carrying surface by transducers so as to correct for tracking and timing errors. The laser diode can function both as an emitter and, in an external cavity mode, as a detector of light reflected from the disc. Drive to the transducers is dependent on tracking and speed error signals generated from the detected light. For tracking and speed error compensation, only lens fiber end, and, optionally, a collimating lens, which are of negligible weight, need be moved rather than the entire scanning head. This provides a simple structure having a high frequency response and low power consumption.Type: GrantFiled: May 14, 1980Date of Patent: June 29, 1982Assignee: Northern Telecom LimitedInventor: Herman W. Willemsen
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Patent number: 4330690Abstract: A telephone group listening system is one in which one member of an assembled group has a telephone for communication with a remote party while the other members may only listen to the communication through the agency of a loudspeaker. The system is subject to the Larsen effect on call answering or clear down if the telephone handset is normally sited close to the loudspeaker. This effect is overcome by including a proximity switch in the loudspeaker circuit, the switch being triggered by a change in the level of coupling of a capacitively or inductively coupled circuit, the coupling being dependent on the closeness of the speaker's body to the switch or on the separation of the handset and the loudspeaker.Type: GrantFiled: May 5, 1980Date of Patent: May 18, 1982Assignee: Northern Telecom LimitedInventor: Radamis Botros
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Patent number: 4329189Abstract: In a fabricating a III-V compound, for example, GaAs, having a layered structure a first layer is grown on a planar substrate by a vapor deposition process adapted to produce differential growth while a subsequent layer is grown by a deposition process which restores planarity. In this way a uniformly thick combination layer is produced with a non-planar junction between its composite layers. Particularly in the fabrication of channelled substrate double heterostructure lasers, a channelled blocking layer is grown by organo-metallic pyrolysis (OMP) and a subsequent confining layer is grown using liquid phase epitaxy (LPE). The OMP process produces a channel with flanking shoulder portions which permit LPE growth of a very thin confining layer immediately above the shoulder portions thereby improving linearity of the device.Type: GrantFiled: July 13, 1981Date of Patent: May 11, 1982Assignee: Northern Telecom LimitedInventors: Julian P. Noad, Anthony J. Springthorpe, Christopher M. Look
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Patent number: D265311Type: GrantFiled: October 22, 1979Date of Patent: July 6, 1982Assignee: Northern Telecom LimitedInventors: Clifford D. Read, Donald T. Chadwick