Abstract: 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 H2, 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.

Abstract: Ceramic monoliths are described which exhibit tunable coefficients of thermal expansion from about −5 to −11×10−6° C.−1 near ambient temperatures. These two-phase ceramics, which are fabricated, for example, by reactive sintering of WO3 and ZrO2, consists of a matrix of ZrW2O8 with inclusions of ZrO2 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.

Abstract: Ceramic monoliths are described which exhibit tunable coefficients of thermal expansion from about −5 to −11×10−6° C.−1 near ambient temperatures. These two-phase ceramics, which are fabricated, for example, by reactive sintering of WO3 and ZrO2, consists of a matrix of ZrW2O8 with inclusions of ZrO2 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.

Abstract: Ceramic monoliths are described which exhibit tunable coefficients of thermal expansion from about −5 to −11×10−6° C.−1 near ambient temperatures. These two-phase ceramics, which are fabricated, for example, by reactive sintering of WO3 and ZrO2, consists of a matrix of ZrW2O8 with inclusions of ZrO2 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.