Abstract: The present invention provides an optical fiber suitable for the manufacture of optical fiber couplers and having low macrobending loss, low cutoff wavelength, low attenuation, and low sensitivity to variations in overclad mass. One aspect of the present invention provides an optical fiber having a core having an index profile, the index profile of the core having a value of ? of between about 1.7 and about 3.0; and a cladding region surrounding and in contact with the core, the cladding region having an outer radius of at least about 40 ?m, wherein the optical fiber has a cutoff wavelength of between about 870 nm and about 970 nm, and a macrobending loss of below about 1 dB at a wavelength of 1550 nm when wrapped one turn around a 32 mm mandrel.

Abstract: The method of fabricating an optical waveguide fiber from a preform having a centerline aperture which includes reducing the pressure in the centerline aperture, then increasing the pressure in the centerline aperture to a pressure in order to improve uniformity, circularity, and/or symmetry around the centerline aperture region.

Abstract: The present invention provides an optical fiber suitable for the manufacture of optical fiber couplers and having low macrobending loss, low cutoff wavelength, low attenuation, and low sensitivity to variations in overclad mass. One aspect of the present invention provides an optical fiber having a core having an index profile, the index profile of the core having a value of &agr; of between about 1.7 and about 3.0; and a cladding region surrounding and in contact with the core, the cladding region having an outer radius of at least about 40 &mgr;m, wherein the optical fiber has a cutoff wavelength of between about 870 nm and about 970 nm, and a macrobending loss of below about 1 dB at a wavelength of 1550 nm when wrapped one turn around a 32 mm mandrel.

Abstract: The method of fabricating an optical waveguide fiber from a preform having a centerline aperture which includes reducing the pressure in the centerline aperture, then increasing the pressure in the centerline aperture to a pressure in order to improve uniformity, circularity, and/or symmetry around the centerline aperture region.

Abstract: A method of manufacturing a flat form from blended metallic powder including a major constituent by weight having a high melting point and a minor constituent by weiht having a substantially lower melting point includes selection of the powder to provide continuous and reproducible compacted flat forms. Powder is selected on the basis of compressibility and flowability. The selected powder is compacted to a flat green form and then liquid phase sintered. The flat form may be stacked to provide a flat article of a desired thickness which will result in a monolithic or composite cross section when subsequently sintered. Liquid phase sintering is carried out in a manner designed to avoid undesirable embrittlement and to provide a uniform microstructure in the fully consolidated article. The process is especially useful in the production of tungsten heavy alloy plate.