Sperry Corporation

Sperry Rand Corporation

Polaroid Corporation

Digital Equipment Corporation

Photon Kinetics, Inc.

Donald H McMahon

Richard A Soref

Bruce A Schofield

Amaresh Mahapatra

Arthur R Nelson

Alan A Kirby

Kent Springer

James B Thaxter

Norman A Sanford

Colin G Whitney

William B Spillman, Jr

John D Liebenrood

William C Robinson

William A Dyes

Gilbert L Johnson, Jr

Input values are data encoded for improved signal characteristics (e.g., limited maximum run length and limited cumulative DC-offset) so as to form 'data codewords,' and then a number of the data codewords, collectively referred to as a block, are error protection encoded, preferably using a conventional linear and systematic forward error control ('FEC') code, to yield an FEC code block. Preferably, an FEC code block is formed by generating a number of check bits or FEC bits equal to the number of data codewords in the block, and then concatenating one FEC bit and its binary complement with each data codeword, so that one FEC bit and its complement is interposed between each successive codeword.

Data and forward error control coding techniques for digital signals

A network interconnection architecture for a plurality of nodes uses sets of grouped node connections which form a plurality of node groups. A central electrically passive interconnection hub is coupled via a signal transmission path to each node group to establish a full mesh coupling between each of the plurality of node groups. An input and output matrix switch along with a pair of 1.times.N multiplexers are also coupled to each of the plurality of node groups and the hub multiplexer via the signal transmission path. The architecture can be further extended to encompass other networks with electrically passive hubs using a sandwich coupling of a matrix switch between two wavelength multiplexers.

High bandwidth network based on wavelength division multiplexing

Input values are data encoded for improved signal characteristics (e.g., limited maximum run length and limited cumulative DC-offset) so as to form 'data codewords, ' and then a number of the data codewords, collectively referred to as a block, are error protection encoded, preferably using a conventional linear and sytematic forward error control ('FEC') code, to yield an FEC code block. Preferably, an FEC code block is formed by generating a number of check bits or FEC bits equal to the number of data codewords in the block, and then concatenating one FEC bit and its binary complement with each data codeword, so that one FEC bit and its complement is interposed between each successive codeword.

An optical multiplexing/demultiplexing device combines an etalon and weak diffraction grating along with temperature control to finely tune local resonant stations along the etalon to separate and/or combine a plurality of optical signals that are finely spaced in wavelength.

Bulk optic wavelength division multiplexer

An optical time domain reflectometer comprises a detector device for detecting optical energy received at an end of a fiber under test, an amplifier having an input terminal connected to the detector device, and a photoconductive switch connected between the amplifier input terminal and a reference potential level. The photoconductive switch is selectively illuminated.

Optical time domain reflectometer having a receiver with selectively

A system for the thermal control of optical devices includes an optical device having at least one coating of an electrically conductive material formed on a surface in a heat conducting relationship with the material and connected to a controllable current source which passes varying amounts of electrical current through the layer to vary the amount of thermal energy introduced into the device to control its optical response characteristics. The electrically conductive layer or layers can be optically active, that is, function to affect the light energy transmitted into or through the device as well as acting as an electrically conductive thermal element. The use of an electrically conductive coating or coatings allows the rapid and precise control of thermal energy introduced into the device and, accordingly, the rapid and precise control of the optical characteristics of the device as well as providing a thermal interface between the optical device and the ambient environment that is effective to minimize the adverse affects of transient temperature changes occurring in the environment.

Thermally controllable optical devices and system

An optical communications system for providing wavelength division multiplexed communications with high spectral channel density and increased sensitivity and selectivity through coherent detection utilizes a fixed frequency source for introducing at least one fixed frequency carrier for system-wide propagation through a system bus. Terminal devices coupled to the system bus functioning as transmitters remove a portion of the system-wide carrier energy and effect a frequency translation and modulation of the translated carrier energy for return to the system bus as a modulated, frequency shifted information bearing signal. Terminal devices functioning as a receiver effect either synchronous homodyne or heterodyne coherent detection by removing a portion of the system-wide carrier energy, optionally effecting a frequency translation, and combining the frequency shifted carrier energy with that of the frequency shifted information bearing signal to effect coherent detection. Where the relative frequency translation of information bearing signal and the locally shifted demodulating carrier energy are the same, homodyne detection is achieved, and, where the relative frequency shift of the information bearing signal and the locally shifted carrier energy is different, an intermediate frequency is provided for subsequent processing.

Optical communication system employing coherent detection and method

Bulk optic echelon gratings suitable for use in multi/demultiplexing optical signals carried on sets of optical fibers. The gratings can be either reflective or transmissive and may be either curved with self-focusing properties or planar requiring the use of auxiliary collimating optics. All versions have the property of being simultaneously blazed at at least two different wavelengths whose ratio is in the range between 0.8 and 0.9. This property of the gratings enables their operation over preferred multiple wavelength bands using a limited set of fibers which are fixed in place. Preferred wavelengths at which the gratings are simultaneously blazed include 1.3 and 1.55 micrometers. Devices incorporating the gratings can be used singly or in groups in inverted tree arrangements for tandem or hierarchical multiplexing purposes.

Bulk optic echelon multi/demultiplexer

An optical fiber communications system includes a closed loop birefringent optical fiber bus for supporting optical energy propagated in a first and a second orthogonal polarization state. An optical energy source introduces a fixed frequency system wide carrier onto the optical fiber bus in a first polarization state for propagation in a first direction. Terminal devices coupled to the optical fiber bus include a bus tap resonator for removing a portion of the system wide carrier light and, in addition to modulating the removed light, effecting a frequency shift to a side frequency and effecting a state shift from the first to the other polarization state, and returning the information bearing optical energy to the optical fiber bus for propagation in a direction opposite to the first direction. A receiving device includes a bus tap resonator for removing a portion of the light from the bus and effecting demodulation to recover the information bearing signal.

Wavelength multiplexed optical communications system and method

Integrated optic devices incorporating echelon gratings suitable for use in performing multi/demultiplexing functions in optical communications systems. The echelon gratings can be either reflection or transmissive types and are conveniently formed using conventional photolithographic techniques.

Integrated optic multi/demultiplexer

An optical communications system includes an optical bus and a plurality of terminal devices coupled to the bus and a reference signal generator for propagating a reference signal through the bus for use by all terminal devices in selecting one of a predetermined number of frequency distinct communications channels. The reference signal is frequency swept in a recurring manner between two fixed frequencies and is introduced onto the system bus, along with a system synchronization signal, for propagation to bus tap resonators associated with the terminal devices in the system. Each terminal device detects the moment at which the swept reference frequency passes through one of the resonant modes of its bus tap resonator and determines the elapsed time thereof from the system synchronization signal. The respective bus tap resonator can be controlled, for example, by controlling its operating temperature, so that the reference frequency passes through the resonant mode of the terminal devices bus tap resonator at a selected time after the occurrence of the system synchronization signal to thus correspond to a frequency distinct communications frequency.

Optical communication system

An optical communications system with terminal devices connected to an optical pathway for communications with one another. A system wide reference signal is introduced into the optical pathway by a reference signal generator for propagation throughout the system. Each terminal device includes a resonant cavity to support one of a plurality of available sets of resonant modes, each set having an associated free spectral range between resonant modes, and controls the resonant cavity structure to lock one of the resonant modes of the resonant cavity to the system wide reference signal. The resonant characteristics of the resonant cavity at each terminal device can be changed to vary the number of integral wavelengths supported in the resonant cavity. Plural terminal devices can communicate with one another to support a set of resonant modes common to one another with one mode of the common set locked to the system wide frequency reference.

Optical communication system employing frequency reference

Integrated optic resonant structures for use in optical communications and sensing applications requiring control or detection of electromagnetic radiation in the optical region of the spectrum. Preferably of planar form, the structures comprise a substrate made of a ferroelectric crystalline material in which there is formed by selectively exchanging protons for an ionic constituent of the substrate at least one optically continuous waveguiding region having predetermined resonant characteristics. At least one other waveguiding region is similarly formed in the substrate to optically couple with the resonant region and includes at least one port by which radiation can be coupled in and out of the substrate. The substrate material is preferably lithium niobate (LiNbO.sub.3) or lithium tantalate (LiTaO.sub.3) in which lithium ions are selectively exchanged for protons supplied by diffusion from a hydrogen rich acid. Applications for the structures include use as a band pass or reject filter, bus tap, sensor, or modulator.

Integrated optic resonant structres and fabrication method

A battery powered optical sensor, capable of functioning for a period of time approximately equal to the shelf life of the battery, utilizes an LED driven by an optical transducer and biased by the battery at a level that exceeds the shot noise level of the LED by the dynamic range of the sensor.

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Carlisle, MA, United States of America

Donald H McMahon