Patents Represented by Attorney, Agent or Law Firm Eli Weiss
  • Patent number: 5117303
    Abstract: In a transmission system having concatenated optical amplifiers, gain saturation of the optical amplifiers at any stage is caused by the extraction of power from the amplifier by the ASE and amplification of the signal and of the ASE from previous stages. Three methods of operating transmission systems are classsified as free-running, constant-total power and constant-signal power. Differences in performance of the three systems arise from the propagation of signal power and the buildup of the ASE. It is now disclosed that the buildup of ASE noise in a system of either lumped or distributed concatenated optical amplifers can be limited by operating at least a plurality of the optical amplifers to provide unsaturated gain which is greater than the loss of the system and/or each optical amplifier is operated in its saturated state.
    Type: Grant
    Filed: August 23, 1990
    Date of Patent: May 26, 1992
    Assignee: AT&T Bell Laboratories
    Inventors: Emmanuel Desurvire, Clinton R. Giles
  • Patent number: 5115338
    Abstract: This invention relates to an Erbium-doped fiber amplifier having multiple stages of amplification for providing enhanced performance. More specifically, optical means is located intermediate first and second stages of doped optical amplifying fibers adapted to receive a pump signal at a pump wavelength where the optical means is adapted to modify the net gain characteristics of the multi-stage amplifier. Presently, all known Erbium-doped fiber amplifiers utilize relatively simple single stage amplifiers which support required ancillary optically passive components such as isolators, filters, pump multiplexers, power monitors and the like at either end of the amplifier.
    Type: Grant
    Filed: April 12, 1991
    Date of Patent: May 19, 1992
    Assignee: AT&T Bell Laboratories
    Inventors: David J. DiGiovanni, Clinton R. Giles
  • Patent number: 5101400
    Abstract: The implementation of BRI/ISDN services is changing the way services can be maintained with existing operations support systems. For example, with ISDN a subscriber to the service can initiate and effect a move of his director or telephone number from one location to another without directly involving the operating company. The subscriber, by moving his directory number to a new location, now receives his service over a new transport facility. As a result, the records of the operating company which identify a specific transport facility to a specific telephone number cannot be readily updated to reflect subscriber moves. Thus, if the records of the operating company do not identify the transport facility which is associated with the directory number at the new location the operating company cannot readily process trouble reports against the service.
    Type: Grant
    Filed: September 29, 1989
    Date of Patent: March 31, 1992
    Assignee: AT&T Bell Laboratories
    Inventor: Louis Krantz
  • Patent number: 5095381
    Abstract: A communications network is implemented utilizing a transmission medium and a plurality of Network Interface Units passively coupled thereto. Communications among a first set of Network Interface Units is implemented on a predetermined channel in a first portion of the transmission medium. Simultaneous communications among a second set of Network Interface Units is implemented using the same predetermined channel in a second portion of the transmission medium. Interference between communications in the first and second portions does not occur because the passive couplers disposed between the portions attenuate the signal from each portion to a value less than a predetermined Network Interface Unit sensitivity level before the signal reaches the other portion.
    Type: Grant
    Filed: January 11, 1990
    Date of Patent: March 10, 1992
    Assignee: AT&T Bell Laboratories
    Inventor: Mark J. Karol
  • Patent number: 5088095
    Abstract: In this invention an optical fiber doped with a rare earth element and coupled to be pumped with a laser is coupled to an optical feedback loop. The feedback loop couples the output signal of the fiber amplifier to the input of the fiber amplifier. A narrow bandwidth filter coupled to the feedback loop allows a selected wavelength of the amplified spontaneous emission to pass from the output of the fiber amplifier to the input of the fiber amplifier. The feedback signal has a wavelength which is different from that of the pump signal and the wavelengths of the signals to be amplified. In operation, when bursts of optical signals from at least two discrete word or frequency division multiplexed channels are amplified in the fiber amplifier, the undesired fluctuations of gain of the output signals normally due to transient saturation of the erbium-doped filter amplifier are substantially eliminated.
    Type: Grant
    Filed: January 31, 1991
    Date of Patent: February 11, 1992
    Assignee: AT&T Bell Laboratories
    Inventor: Martin Zirngibl
  • Patent number: 5078499
    Abstract: An optical interconnection arrangement having a high degree of connectivity and bandwidth is obtained by a non-collinear arrangement of lenses. In a preferred embodiment, the optical system comprises a first pupil lens, a second pupil lens and an array of fanout lenslets wherein the optical axes of the first and second pupil lenses are collinear. The first and second pupil lenses form an afocal system with the array of fanout lenslets situated between and at the focal planes of the first and second pupil lenses. Light beams from arrays of light emitting devices are collimated by input probe lenses that have their optical axes non-collinear with the optical axis of the first lens. The first pupil lens forms a coincident pattern of the arrays of light emitting devices. Additionally, the array of fanout lenslets fans out exiting beamlets comprising the coincident pattern such that each exiting beamlet substantially fills the aperture of the second pupil lens.
    Type: Grant
    Filed: August 4, 1989
    Date of Patent: January 7, 1992
    Assignee: AT&T Bell Laboratories
    Inventor: Robert E. LaMarche
  • Patent number: 5078468
    Abstract: This invention is a highly efficient star coupler for use with single mode waveguides. In the inventive coupler, all of the input waveguides and all of the output waveguides are assembled to form two separate bundles. The two bundles are axially aligned with each other and the ends of the bundles are spaced apart. The ends of the waveguides of the bundle of output waveguides are polished to receive optical energy from the bundle of input waveguides. The end facet of the input waveguide bundle is shaped and polished to form a convex spherical surface. The diameter of each waveguide of the bundle is small relative to the diameter of the bundle of waveguides. Therefore, the end facet of each waveguide which makes up the convex spherical surface is angled very slightly relative to the waveguide axis. This slight angle on the end facet of the waveguide acts as a bevel to bend the optical energy coming out of the end of the waveguide.
    Type: Grant
    Filed: April 24, 1991
    Date of Patent: January 7, 1992
    Assignee: AT&T Bell Laboratories
    Inventor: Julian Stone
  • Patent number: 5077728
    Abstract: An N.times.N passive star coupler can be used to provide a high performance optical data network to interconnect many users at gigabit rates. Ignoring excessive losses, a signal incident on any input port is divided equally between all of the output ports. The average power at all of the input ports N of the star is equal to the average power at all of the output ports N. But, the power per channel at each output port is equal to only 1/N of the applied power. This loss which is due to splitting cannot be recovered by an amplifier at either the input port or the output port of the star coupler unless the amplifier saturation power is greater than the transmitter power. This invention solves the problem of amplifier saturation.
    Type: Grant
    Filed: December 20, 1989
    Date of Patent: December 31, 1991
    Assignee: AT&T Bell Laboratories
    Inventor: Ivan P. Kaminow
  • Patent number: 5063585
    Abstract: The present invention relates to a method for distinguishing between an open conductor and a proper termination of a telephone subscriber loop which is terminated with a telephone which does not conform to the ringer-equivalence standard of the FCC Rules. In this invention a telephone subscriber loop can be tested for an open or for a termination by a customer provided equipment telephone by obtaining a first ratio of the tip-to-ground impedance relative to the tip-to-ring impedance; and a second ratio of the ring-to-ground impedance relative to the tip-to-ring impedance, and comparing each of these ratios relative to a fixed ratio value. If the measured ratios are substantially equal to or greater than the fixed ratio value, the subscriber loop is terminated with a customer provided equipment telephone. The fixed value may be dependent upon the length of the loop and whether or not a maintenance termination unit is present in the loop.
    Type: Grant
    Filed: September 27, 1990
    Date of Patent: November 5, 1991
    Assignee: AT&T Bell Laboratories
    Inventor: Roy A. Shapiro
  • Patent number: 5055795
    Abstract: A transversal equalizer is realized by employing variable gain and delay in the amplification branches of a traveling wave amplifier. Specifically, by adjusting the gain and delay in each branch, the traveling wave type transversal equalizer may be adjusted to having a complementary frequency response in order to compensate for linear channel gain and phase ripples. This approach permits the transversal equalizer to be designed without the use of resistive splitter and combiner networks and, therefore, without the use of high gain amplifiers. Without such amplifiers, splitters and combiners, the smaller physical size, which is afforded thereby, allows the transversal equalizer to be easily assembled as a hybrid integrated circuit.
    Type: Grant
    Filed: May 29, 1990
    Date of Patent: October 8, 1991
    Assignee: AT&T Bell Laboratories
    Inventors: Bryon L. Kasper, Osamu Mizuhara
  • Patent number: 5050949
    Abstract: In this invention there is disclosed a multi-stage optical fiber amplifier for providing a new functon, that of gain equalization. The disclosed multi-stage optical fiber amplifier comprises at least two stages of amplification where each stage comprises an amplifying fiber having a different gain spectrum. In one embodiment the two stages, which can be pumped separately, have different dopant compositions to provide each stage with a different gain spectrum. The disclosed multi-stage optical fiber amplifier provides overall gain spectrum equalization of the amplified channels of long haul transmission lines. Typically, gain equalization can adjust the gain of one channel while maintaining the gain of a second channel constant. When used in combination with automatic gain control, the amplifier gain can be equalized dynamically to compensate for random variations in the relative optical power of wavelength-multiplexed signals to prevent system impairment caused by low-power channels.
    Type: Grant
    Filed: June 22, 1990
    Date of Patent: September 24, 1991
    Assignee: AT&T Bell Laboratories
    Inventors: David J. DiGiovanni, Clinton R. Giles
  • Patent number: 5040033
    Abstract: Briefly, in the invention a photodetector and an optical amplifier are integrated in the same semiconductor chip. The optical amplifier and the photodetector are positioned side-by-side on the same chip. A portion of the electromagnetic energy carried in the evanescent tail of the optical mode is detected by the photodetector for monitoring the average output power of the optical amplifier. Current confinement and lateral index guiding can be provided by Fe or Ti doped semi-insulating layers of InP. The side-by-side arrangement enables the detector to monitor the output power of the optical amplifier without degrading the output power of the optical amplifier.
    Type: Grant
    Filed: June 26, 1989
    Date of Patent: August 13, 1991
    Assignee: AT&T Bell Laboratories
    Inventors: Niloy K. Dutta, Thirumala R. Halemane, Steven K. Korotky
  • Patent number: 5040111
    Abstract: The present invention utilizes hardware and/or software, in combination with a personal computer and its peripheral devices (i.e., storage media, peripheral control, video display and the like) to monitor communication links. The personal computer, to operate properly, must operate in an interactive communication mode. But, to avoid "lock-up" of a communication link which is being monitored, the personal computer must be "invisible" to equipment on the communication link. Hardware is disclosed which permits the personal computer to operate in its interactive communications mode while being "invisible" (non-interactive) to equipment on a communication link being monitored.
    Type: Grant
    Filed: April 11, 1988
    Date of Patent: August 13, 1991
    Assignee: AT&T Bell Laboratories
    Inventors: Daniel Y. Al-Salameth, Jeffrey J. Farah, John Soukas
  • Patent number: 5039993
    Abstract: A waveguide array comprising a plurality of waveguides which are each outwardly tapered at the aperture of the array in accordance with a predetermined criteria chosen to increase waveguide efficiency. The tapering serves to gradually transform a fundamental Bloch mode, propagating through the waveguide array, into a plane wave in a predetermined direction, and then to launch the plane wave into free space in the predetermined direction. In another embodiment, the waveguides are positioned relative to one another in order to satisfy the predetermined criteria.
    Type: Grant
    Filed: November 24, 1989
    Date of Patent: August 13, 1991
    Assignee: AT&T Bell Laboratories
    Inventor: Corrado Dragone
  • Patent number: 5037180
    Abstract: In this invention there is disclosed an optical filter disposed on an optical fiber. More specifically, a filter comprised of a multilayer thin-film stack of low and high index of refraction material is deposited onto the end of an optical fiber. The filter can be, for example, a long-pass filter, a Fabry-Perot Etalon, a Double-Cavity Filter, and the like. Filters deposited on perpendicular facets of single-mode fibers reflect most of the power that is not transmitted. This reflection if fed back to a laser or an amplifier can cause a problem, particularly if an isolator does not adequately block the reflections. A bevel on the fiber end face can eliminate this problem by preventing the reflected power from being directed back into the optical fiber.
    Type: Grant
    Filed: July 19, 1990
    Date of Patent: August 6, 1991
    Assignee: AT&T Bell Laboratories
    Inventor: Julian Stone
  • Patent number: 5028892
    Abstract: An analog voltage-controlled phase shifter is disclosed which is smaller in size and provides a larger phase shift for a smaller change of capacitance of presently available voltage controlled phase shifters. These unexpected advantages are obtained by using lumped elements to simulate the normally used .lambda./4 transmission lines of the hybrid portion of the phase shifter and by eliminating or reducing the value of the capacitors normally present at the varactor nodes of the hybrid. The capacitance fully or partially removed from the varactor nodes of the hybrid can be selectively fully or partially added to the varactors.
    Type: Grant
    Filed: April 30, 1990
    Date of Patent: July 2, 1991
    Assignee: AT&T Bell Laboratories
    Inventor: Timothy E. Daughters
  • Patent number: 5029297
    Abstract: The device here disclosed comprises an optical amplifier coupled to direct optical energy into a passive waveguide for transmission through the waveguide to its other end. A photodetector, positioned relative to the passive waveguide, detects the presence of optical energy in the passive waveguide. The photodetector in the structure illustrated is positioned downstream from the optical amplifier and spatially positioned with respect to the optical amplifier to receive optical energy only from the waveguide. The photodetector does not receive optical energy directly from the optical amplifier. A small fraction of the optical energy carried by the passive waveguide is received and detected by the photodetector.
    Type: Grant
    Filed: October 13, 1989
    Date of Patent: July 2, 1991
    Assignee: AT&T Bell Laboratories
    Inventors: Thirumala R. Halemane, Thomas L. Koch, Steven K. Korotky
  • Patent number: 5027079
    Abstract: This invention relates to an Erbium doped fiber amplifier having improved operating characteristics. Parameters which determine the operating characteristics of an erbium doped fiber amplifier are the concentration of erbium in the core of a fiber; the ratio of the radius of the core of the fiber doped with erbium relative to the radius of the core of the fiber, and, the length of the fiber. It is now recognized that improved fiber amplifier performance can be obtained by varying the core-cladding refractive index difference of the fiber. The various parameters are here defined for providing an erbium doped fiber amplifier having optimum gain characteristics.
    Type: Grant
    Filed: July 31, 1990
    Date of Patent: June 25, 1991
    Assignee: AT&T Bell Laboratories
    Inventors: Emmanuel Desurvire, Clinton R. Giles, John L. Zyskind
  • Patent number: 5027435
    Abstract: One aspect of the invention is a Fabry-Perot cavity which has in part a waveguiding portion and in part a nonwaveguiding portion. In this manner, a cavity is constructed whose length would be too short to manipulate effectively if it were comprises exclusively of a waveguiding portion, and whose length might have unacceptable diffraction losses if it were comprised exclusively of a nonwaveguiding portion. In the inventive device the resonant wavelength can be adjusted by varying the length of either the gap or the waveguide or both. The device can be advantageously constructed and aligned using fiber coupling technology.
    Type: Grant
    Filed: January 27, 1989
    Date of Patent: June 25, 1991
    Assignee: AT&T Bell Laboratories
    Inventors: Andrew R. Chraplyvy, Patrick P. Iannone, Ivan P. Kaminow, Tingye Li, Julian Stone, Lawrence W. Stulz, Robert W. Tkach
  • Patent number: 5005175
    Abstract: This invention is a rare earth doped optical amplifier with increased gain and lowered pump thresholds. The amplifying scheme is based on a 3 level lasing system rather than the more prevalent 4 level lasing system. Additionally, the transmission mode of the optical fiber at the pump wavelength has a radius which is substantially equal to or greater than the radius of the distribution profile of the rare earth ions in the fiber amplifier core. With the inventive amplifier, a gain of 37 dB and a saturation power of 11.3 dBm has been obtained with only 54 mW of launch power at .lambda.=1.49 .mu.m.
    Type: Grant
    Filed: November 27, 1989
    Date of Patent: April 2, 1991
    Assignee: AT&T Bell Laboratories
    Inventors: Emmanuel Desurvire, Clinton R. Giles, Jay R. Simpson, John L. Zyskind