Lucent Technologies Inc.

At&t Bell Laboratories

At+t Corp.

Bell Telephone Laboratories

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

Agere Systems Guardian Corp.

Fitel USA Corporation

Paul Joseph Lemaire

Kenneth L Walker

Sungho Jin

Victor Mizrahi

David Wilfred Johnson

Debra Anne Fleming

Ashish Madhukar Vengsarkar

Robert M Atkins

Thomas Andrew Strasser

John David Weld

Jon W Engelberth

Arthur D Pearson

Glen Robert Kowach

Paul D Lazay

John Burnette MacChesney

Turan Erdogan

Hareesh Mavoori

George J Shevchuk

William Alfred Reed

Rolando Patricio Espindola

Alastair M Glass

Jay R Simpson

Lloyd Shepherd

Sandra Greenberg Kosinski

Richard G Huff

Paul B O'Connor

Frank Vincent DiMarcello

Justin Boyd Judkins

Donald Paul Monroe

David J Kudelko

Katherine Theresa Nelson

Thomas Henry Tiefel, Deceased

Roseann Csencsits

Paul M Rominski

Shungho Jin

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

Ceramic monoliths are described which exhibit tunable coefficients of thermal expansion from about &minus;5 to &minus;11&times;10 &deg; C. near ambient temperatures. These two-phase ceramics, which are fabricated, for example, by reactive sintering of WO and ZrO , consists of a matrix of ZrW O with inclusions of ZrO having diameters less than 10 &mgr;m. Additives may increase the density of the monoliths to greater than 98% of the calculated density. Green body densities, pre-sintered particle size distribution, sintering atmosphere, microstructure, and mechanical properties are discussed. These ceramics may be used as substrates for thermally compensating fiber Bragg gratings.

Process for making isotropic negative thermal expansion ceramics

Ceramic monoliths are described which exhibit tunable coefficients of thermal expansion from about &minus;5 to &minus;11&times;10,&deg; C.,near ambient temperatures. These two-phase ceramics, which are fabricated, for example, by reactive sintering of WO,and ZrO,, consists of a matrix of ZrW,O,with inclusions of ZrO,having diameters less than 10 &mgr;m. Additives may increase the density of the monoliths to greater than 98% of the calculated density. Green body densities, pre-sintered particle size distribution, sintering atmosphere, microstructure, and mechanical properties are discussed. These ceramics may be used as substrates for thermally compensating fiber Bragg gratings.

Isotropic negative thermal expansion cermics and process for making

A compact temperature compensating device for an optical fiber grating includes an inner expansion member disposed concentrically within and in a substantially parallel relationship with an outer expansion member. The outer expansion member has a coefficient of thermal expansion greater than that of the inner expansion member. The device further includes a base member and a pivoting lever. The base member is fixedly attached to a distal end of the outer and inner expansion members and to a distal end of the fiber grating disposed concentrically within the inner expansion member. The lever is connected to a proximal end of the inner and outer expansion members and to a proximal end of the fiber grating through joints that are flexurally deformable so that, as the expansion members expand and contract differentially within an expected temperature range, the lever pivots about the inner expansion member and imparts a desired amount of axial strain in the fiber grating to maintain the grating wavelength substantially constant.

Temperature compensating device for fiber gratings

A temperature compensating device for optical fiber gratings includes first and second expansion members having different coefficients of thermal expansion. The expansion members are elongated in a direction parallel to the fiber grating and levers are secured to both ends of the expansion members. Each lever has a first end flexibly secured to a respective end of the first expansion member and a middle portion flexibly secured to a respective end of the second expansion member. The other end of each lever is secured to a respective end of the fiber grating. The expansion members, the levers and the fiber grating all lie substantially in a single plane. There is also disclosed a package for holding four of the temperature compensating devices in two rows of two devices each, with their fiber gratings adjacent each other so that when viewed in a plane orthogonally to the longitudinal axes of the fiber gratings, the fiber gratings are each at a respective corner of a rectangle.

Temperature compensating device for fiber gratings and a package therefor

A temperature compensated optical fiber grating device comprises a longitudinally extending optical fiber grating having a length and a packaging assembly for the grating comprising a first longitudinally extending body of material having a first coefficient of thermal expansion (CTE) and second and third longitudinally extending bodies of material having CTE's lower than the first CTE. The three bodies are mechanically attached at alternate ends to form a composite structure having an effective negative CTE between two ends to which the grating is attached. The resulting grating device can be made in compact form having an overall length less than 30% more than the grating (and preferably less than 10%) and can reduce the temperature dependent wavelength change in the grating to less than 0.2 nm/100.degree. C. and preferably less than 0.05 nm/100.degree. C. In a preferred embodiment, the packaging bodies include a cylinder enclosing the grating.

Temperature-compensated optical fiber gratings with fine wavelength

A device and method for dynamically tuning a long-period grating of an optical fiber is disclosed. The grating is made tunable by using a controlled strain imposed on the fiber adjacent the grating, wherein the strain comprises an electromechanical force, magnetostrictive force, magnetic force, or a thermally-induced force. An improved optical communication system comprising a dynamically gain-equalized amplifier device, a wavelength feedback device, and the tunable long-period grating device is also disclosed. In the communications system, the grating device is reconfigured to have a desired broadband filtering frequency, thus equalizing the amplifier gain, in response to feedback from the wavelength detector.

Tunable long-period optical grating device and optical systems employing

A tunable fiber grating comprises a temperature-sensitive body secured to a fiber having a fiber grating region for transmitting thermally-induced strain to the grating. The amount of strain and hence the degree of wavelength tuning are controlled by adjusting the temperature of the temperature-sensitive body, wherein the extent of adjustment is preferably pre-determined according to feedback from a wavelength detector. Large thermal strains obtainable with the present invention allow a wide range of wavelength tuning with a relatively small and convenient temperature change near ambient temperature. In a preferred embodiment, the temperature-sensitive body is cylindrical and comprised of a nickel-titanium alloy bonded to the grating. In alternative arrangements, the thermal strain effect can be amplified. An add/drop multiplexer employing the tunable gratings is also described.

Device for tuning wavelength response of an optical fiber grating

A temperature compensating optical waveguide device including an optical fiber in which a grating formed of grating elements embedded within the fiber core reflects fiber-transmitted light within a range about a central wavelength that varies with temperature and with an axial strain applied to the grating. A top surface of a compensating member is affixed to a portion of the fiber that includes the grating and a tension adjusting member is connected to the compensating member. The tension adjusting member and the compensating member are formed of materials selected so that as the temperature of the device decreases, the tension adjusting member contracts more than the compensating member so as to control the deformation of the compensating member and thereby impose an axial strain on the grating. The controlled application of tensile stress to the optical fiber in the region of the grating causes changes in the central wavelength of reflected light to compensate for central wavelength variations resulting from changes in the grating temperature.

Fiber grating package

In accordance with the invention, a tunable fiber grating comprises a fiber grating secured to a magnetostrictive body so that magnetostrictive strain will be transmitted to the grating. An electromagnet is disposed adjacent the magnetostrictive body for applying a magnetic field along the body. Control of the current applied to the electromagnet permits control of the strain transmitted to the fiber grating, and thus control of the grating spacing and reflection frequency. In a preferred embodiment the magnetostrictive body is cylinder bonded along the grating. In alternative arrangements, the magnetostrictive effect can be mechanically amplified. An add/drop multiplexer employing the tunable gratings is described.

Magnetostrictively tunable optical fiber gratings

In accordance with the invention, a tunable fiber grating comprises a fiber grating secured between a pair of magnets so that magnetic force (repulsive or attractive) applied to the magnets is transmitted to the grating. An electromagnet is disposed adjacent the magnets for applying the field to magnetize them. Control of the current applied to the electromagnet permits control of the force transmitted to the fiber grating and, thus, control of the grating strain, spacing and reflection frequency. In a preferred embodiment the electromagnet is actuated to produce magnetic pulses which control the remanent force between the two magnets, eliminating the need for continuous power. An add/drop multiplexer employing the tunable gratings is described.

Magnetically tunable optical fiber gratings

The present applicants have discovered that one can fabricate a long-period grating wherein the grating peak wavelength .lambda..sub.p will be shifted in different directions when the grating is subject to temperature and tensile strain, respectively. Accordingly, a long-period grating can be designed and packaged such that a temperature-induced shift in .lambda..sub.p is compensated by a corresponding strain-induced shift arising from a single packaging material. Thus, by proper design of the grating and choice of the packaging material expansion coefficient, a temperature stable grating having temperature sensitivity of less than 4 nm per 100.degree. C. can comprise a grating fiber encased in or attached to a package comprising a single material such as glass, polymer or metal. Such designs permit the use of long-period grating devices without temperature control.

Long-period fiber grating devices packaged for temperature stability

Conventional optical gratings are relatively temperature sensitive. This sensitivity is generally undesirable but can be reduced or eliminated by attaching the grating to a support member having a negative coefficient of thermal expansion. Exemplarily the member comprises Zr-tungstate and/or Hf-tungstate. The thermal expansion can be tailored by admixture of positive expansion coefficient material (e.g., Al.sub.2 O.sub.3, SiO.sub.2) to the negative expansion coefficient material (e.g., ZrW.sub.2 O.sub.8), or by a variety of other techniques.

Article comprising a temperature compensated optical fiber refractive

The present invention is predicated upon the discovery by applicants of a relationship describing thermal decay of radiation-induced index changes and a mechanism which permits stabilization by accelerated aging. Specifically, the induced index change decays in proportion to 1/(1+At.sup..alpha.) where A and .alpha. are functions of temperature, and the decay can be accelerated by heat treatment. As a consequence, the extent of decay can be determined for arbitrary time and temperature and, significantly, an appropriate heat treatment can be scheduled for making a device stable within predeterminable limits.

Method of making stable optical devices employing radiation-induced

In accordance with the invention, the index of refraction of a glassy material is increased by treating the material with hydrogen and applying heat. Specifically, the glass is exposed to hydrogen or deuterium at pressure in the range 14-11,000 p.s.i. and a temperature in the range 21.degree.-150.degree. C. for a time sufficient for the hydrogen to diffuse into the glass. The glass is then subjected to heat in excess of about 500.degree. C., as by application of a flame or infrared radiation. The duration of heating can be less than a second. The result is a substantial and long-lived increase in the normalized refractive index. For example, flame heating of H.sub.2 loaded commercial GeO.sub.2 doped optical fibers (AT&T Accutether single mode fiber) has produced normalized index changes .increment.n/n of 4.times.10.sup.-3. This process can be used to make and adjust a variety of optical waveguide devices.

Growing community of inventors

Madison, NJ, United States of America

Paul Joseph Lemaire