Lucent Technologies Inc.

At&t Bell Laboratories

At+t Corp.

American Telephone & Telegraph Co., At&t Bell Laboratories

Bell Telephone Laboratories

Fitel USA Corporation

Tyco Submarine Systems Ltd.

Kenneth L Walker

David John DiGiovanni

Paul Joseph Lemaire

Stephen G Grubb

Ashish Madhukar Vengsarkar

Andrew John Stentz

Jay R Simpson

Katherine Theresa Nelson

Victor Mizrahi

Richard G Huff

Thomas Andrew Strasser

Andrew Roman Chraplyvy

William Alfred Reed

Robert M Atkins

Daryl Inniss

Arthur C Hart

John A Rogers

John Burnette MacChesney

Benjamin John Eggleton

Linn F Mollenauer

Rolando Patricio Espindola

Jane Deborah LeGrange

Frank Vincent DiMarcello

Paul Francis Glodis

Frederik Willem Willems

Matthijs M Broer

Sungho Jin

Jefferson L Wagener

Allan James Bruce

Man Fei Yan

Robert William Tkach

Paul Francis Wysocki

Hareesh Mavoori

James William Fleming

Leonard G Cohen

Ian A White

Per Bang Hansen

Raymond Wolfe

Howard D Kidorf

David Kalish

Lars Erik Eskildsen

Torben N Nielsen

Clifford E Headley

Justin Boyd Judkins

Ralph Stephen Jameson

John T Krause

Gloria R Jacobovitz-Veselka

Weyl-Kuo Wang

Kim Willard Womack

Donald Paul Jablonowski

Janet Renee Pedrazzani

Isaac Ryazansky

Stanley F Marszalek

Charles Francis Gridley

Jerry R Bautista

Robert M Aktins

Shungho Jin

Roseann Csencsits

An optical transmission system exploits the reduced signal-to-noise (SNR) requirements for low-bit rate channels to devise a new wavelength channel allocation scheme which increases the number of channels that a WDM system can support. Wavelengths of low-bit rate channels are assigned outside a flat-gain window (i.e., flat-passband region) of the system. The channel allocation scheme uses the high-bit rate channels located in the flat-passband region of wavelengths and the lower-bit rate channels located outside this passband region with progressively lower-bit rate channels located farther outside this passband region. Low-bit rate channels are also assigned to region(s) of the passband where the non-linear threshold power level of the system may be exceeded.

Power and wavelength management for mixed-rate optical data systems

Applicants have discovered that glass optical waveguides subject to hydrogen-induced loss increases can be passivated by treating the glass with deuterium. The deuterium-treated glass not only exhibits a lower rate of loss increase when later exposed to environments containing H , but also retains high transmission of light in the 1.55 and 1.31 micrometer wavelength regions immediately after the deuterium heat treatment. The method applies to Er-doped fiber, transmission fiber and planar waveguides. Under some circumstances, hydrogen can be substituted for deuterium.

Glass optical waveguides passivated against hydrogen-induced loss increases

In accordance with the invention, an optical communication system is provided with one or more automatic dispersion compensation modules. Each module has an adjustable dispersion element, a data integrity monitor and a feedback network whereby the monitor adjusts the dispersion element to optimize system performance. In a preferred embodiment the dispersion compensating modules comprise chirped fiber Bragg gratings in which the chirp is induced in the grating by passing a current along distributed thin film heaters deposited along the length of the fiber. The magnitude of the applied current determines the dispersion of the grating. A data integrity monitor is configured to sense the integrity of transmitted data and to provide electrical feedback for controlling the current applied to the grating.

Optical communication system incorporating automatic dispersion compensation modules

A high speed optical communication system (&gE;10 Gbit/s) is compensated for temperature variation by providing it with one or more automatic dispersion compensation modules. Each module has an adjustable dispersion element, a data integrity monitor and a feedback network whereby the monitor adjusts the dispersion element to compensate for temperature variation. In a preferred embodiment the dispersion compensating modules comprise chirped fiber Bragg gratings in which the chirp is induced in the grating by passing a current along distributed thin film heaters deposited along the length of the fiber. The magnitude of the applied current determines the dispersion of the grating. A data integrity monitor is configured to sense the integrity of transmitted data and to provide electrical feedback for controlling the current applied to the grating.

Optical fiber communication system incorporating automatic dispersion compensation modules to compensate for temperature induced variations

In accordance with the invention an optical fiber communication system comprising a source of optical signals and an optical fiber transmission line is provided with one or more multiple-order distributed Raman effect amplifiers downstream of the source for amplifying the transmitted signals. As compared with a communication system using conventional first order Raman amplifiers, multiple-order amplifier systems can have reduced noise, longer fiber span lengths and reduced nonlinearities. In a preferred embodiment the system uses signal wavelengths in the range 1530-1570 nm, first order Raman pumping at 1430-1475 nm and second order pumping at about 1345 nm. Advantageously, the second order pump light is copropagating with the signal light and the first order pump is counterpropagating with the signal.

Optical communication system using multiple-order Raman amplifiers

The deposition rate of MCVD processes is enhanced by applying at least a first and a second independently controlled heat source to a plurality of reactants which are used to form deposited particulate matter. The first heat source is adjusted so as to provide at least a specified rate of reaction for the reactants, and the second source is adjusted so as to provide at least a specified deposition rate for the particulate matter.

Modified chemical vapor deposition using independently controlled

A large optical preform 303 is made by a modified chemical vapor deposition (MCVD) process by depositing successive layers of core and cladding materials onto the inside surface of a rotating glass tube 33 having a hydroxyl ion (OH.sup.-) level that is less than 0.5 parts per million (ppm) by weight. The tube is then collapsed inwardly to form a core rod 301 in which the deposited core material 31 has a diameter that is greater than about 5 millimeters and the deposited cladding material 32 has an outside diameter that is less than about 15 millimeters. A machine-vision system 140, 150, 160 monitors and controls the diameter of the glass tube by regulating the pressure within the tube. Moreover, the machine-vision system monitors and controls the straightness of the tube by varying its rotational speed according to angular position. After the core rod 301 is formed, it is plasma etched to remove contaminants, and then overclad with two glass jackets 34, 35 having a hydroxyl ion (OH.sup.-) level that is less than 1.0 ppm by weight to create a large preform 303 from which about 400 kilometers of singlemode optical fiber can be drawn per meter of length.

Method of making a large MCVD single mode fiber preform by varying

We have found that the conversion efficiency of a Er/Yb-doped cladding pumped fiber amplifier increases with increasing signal input power. Thus, preamplification of the input signal by means of an Er-doped fiber amplifier can result in increased conversion efficiency of the cladding pumped power amplifier. Such increased efficiency is desirable, lessening heat removal problems and/or facilitating increased reliability.

Multi-stage optical fiber amplifier having high conversion efficiency

Magnets are used to control the amount of coupling loss between fibers. The fiber ends are attached to magnets and by controllably magnetizing the magnets, the fibers can be pulled apart or brought closer together to vary the amount of coupling loss. Preferably at least one of the magnets is latchable. The advantage of the latchable version is that a predetermined amount of loss can be latchably set by magnetizing the magnets to a particular level and afterwards no additional power is required to maintain the amount of attenuation. This is advantageous compared to other approaches in which power is required continuously to maintain a particular loss level.

Magnetically controlled variable optical attenuator

The disclosed optical fiber communication system comprises a remotely pumped erbium-doped fiber amplifier (EDFA). The pump radiation is de-tuned with respect to wavelength, the wavelength being selected longer than both the optimal wavelengths for pumping the EDFA and for producing Raman gain in the transmission fiber, respectively. Such de-tuning results in improved over-all system performance through reduced multi-path interference. Exemplarily, the pump radiation has wavelength in the range 1490-1510 nm.

Optical fiber communication system with a distributed Raman amplifier

In an optically amplified multi-wavelength optical fiber communication system, deleterious effects due to channel addition/removal can be reduced or avoided if the optical amplifiers are 'overpumped', that is to say, the system is selected such that at least 70%, preferably 90% or more, of the pump power that is introduced into the amplifier fiber is unabsorbed in the amplifier fiber.

Robust multi-wavelength optical fiber communication systems

In one embodiment, an optical transmitter, which has a modulator disposed between an pair of optical amplifiers, exhibits reduced carrier-to-noise ratio and relatively high powers. In another embodiment, an optical amplifier is disposed between the laser carrier source and the modulator, but the post-modulator amplifier is omitted. Application of the transmitters to analog systems (e.g., CATV) and digital systems is described.

Optical transmitter having pre-modulation amplification

The performance of optical fiber Raman devices can be increased by substitution of a broadband reflector (typically a multilayer dielectric mirror) for some of the narrowband reflectors (typically fiber Bragg gratings) that are conventionally used to define the optical cavities of the device. The device exemplarily is a Raman laser or amplifier, and in preferred embodiments a broadband reflector reflects all the Stokes-shifted wavelengths, such that the cavities are defined by the single broadband reflector and by a multiplicity of appropriately selected narrowband reflectors. Optionally the broadband reflector also serves to reflect the pump radiation.

Article comprising an improved cascaded optical fiber Raman device

An upgrade method in which Raman amplification is added to an existing transmission system to provide an increase in power budget and permit a substantial increase in transmission capacity either by time division multiplexing (TDM), wavelength division multiplexing (WDM), or a combination thereof. The power budget improvement permits higher transmission capacity by increasing either a single channel data rate and/or the number of wavelength division multiplexed data channels that can be accommodated by existing fiber links.

Method of upgrading transmission capacity by Raman amplification

Growing community of inventors

New Providence, NJ, United States of America

Kenneth L Walker