Bell Telephone Laboratories

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

At&t Bell Laboratories

James W Fleming, Jr

Leonard G Cohen

Raymond Edward Jaeger

Thomas John Miller

John W Shiever

John Burnette MacChesney

John Thomson, Jr

Paul B O'Connor

Henry M O'Bryan, Jr

William George French

Sandra A Pardenek

The disclosed simple, economical and rapid sol-gel process for forming a silica-based glass body, termed the 'vapogel' process, comprises introduction of a silicon halide-containing gas (e.g., SiCl.sub.4 +O.sub.2) into an aqueous medium. The thus formed sol can gel within minutes, resulting in a monolithic gel from which particles having a narrow size distribution can easily be formed. The thus formed particles can be used to produce a glass body such as an optical fiber. Various techniques for forming the glass body from the gel are disclosed. Among the many advantages of the vapogel method are its ability to produce very homogeneous mixed oxide glasses of composition not obtainable by prior art sol-gel processes, and the advantageous mechanical properties of the gel produced by the method. The latter makes possible, inter alia, formation of particles having a relatively narrow size distribution.

Glass body formed from a vapor-derived gel and process for producing same

Disclosed is BeF.sub.2 -based optical fiber. Such fiber can have, in addition to low loss, other advantageous properties. For instance, BeF.sub.2 -based dispersion shifted single mode fiber can have lower core-cladding index difference and larger core diameter than the corresponding SiO.sub.2 -based fiber, and BeF.sub.2 -based graded index multimode fiber can have larger bandwidth than the corresponding SiO.sub.2 -based fiber. The inventive fibers have a core and a cladding containing at least 30 mol % BeF.sub.2, and may contain up to 40 mol % of AlF.sub.3, and one or more members of the group consisting of NaF, KF, MgF.sub.2, CaF.sub.2, PbF.sub.2, PF.sub.5, and SiF.sub.4. An exemplary and currently preferred glass has nominal composition (in mol percent) 30KF-(15-x)CaF.sub.2 -xPbF.sub.2 -10AlF.sub.3 -45BeF.sub.2, with x.ltoreq.15. Single mode fibers according to the invention have minimum total dispersion in the range 1.5-2.0 .mu.m, and typically have 0.25%.ltoreq..DELTA..sub.esi .ltoreq.0.6%, and 2.5 .mu.m.ltoreq.a.sub.esi .ltoreq.3.4 .mu.m, where .DELTA..sub.esi and a.sub.esi are the equivalent step index core-cladding index difference and core radius, respectively. Rules and techniques that can advantageously be used to design BeF.sub.2 -based single mode fibers are also disclosed.

BeF.sub.2 -based optical fibers

Optical components using a germania-silica glass are made by a gel technique. Tetra pentyloxygermane and a silicon alkoxide are hydrolyzed to form a gel, which is subsequently dried. Optical components, including optical fibers and devices, can be made using glass prepared by this technique.

Method for making germanium-silicate gel glass and articles

Aluminum metaphosphate optical fibers are disclosed. In a specific embodiment, aluminum metaphosphate, doped with from 10 to 30 mole percent of diboron trioxide, is found to yield an optical fiber which combines the desirable properties of both high numerical aperture and low material dispersion. The fiber is nonhygroscopic and has a high melting temperature. The index of refraction of the glass may be lowered by doping with silicon dioxide. Consequently, a graded fiber may be made by increasing the concentration of silicon oxide from the core to the cladding.

Aluminum metaphosphate optical fibers

Optical fiber preforms are produced by means of a duplex hot zone, a section of which is defined by an r.f. generated plasma fire ball. The process operates within a tube with gaseous precursor material reacting within the hot zone to result in deposited material of the desired preform glass composition. A 'smoothing' region within the hot zone is defined by tube surface at a temperature sufficiently elevated to consolidate any particulate material resulting from reaction. In some aspects, the disclosed procedures may be regarded as Modified Chemical Vapor Deposition. Commercial significance resides in significantly increased throughput of preforms and, consequently, in fiber.

Optical fiber fabrication by a plasma generator

A ceramic composition and processing procedure is described which is useful in electric and electronic devices such as thermistors. The ceramic composition, which may be described as a semiconducting barium titanate, exhibits a large positive temperature coefficient of resistance. Advantages are ease and convenience of fabrication with lower sintering temperature than conventional processing and use of an air atmosphere instead of nitrogen or oxygen atmospheres. This facilitates batch processing and permits convenient sintering in a continuous kiln.

Composition and processing procedure for making thermistors

A multimode optical fiber waveguide with graded refractive index for lessening modal dispersion depends upon simultaneous grading of both P.sub.2 O.sub.5 and B.sub.2 O.sub.3 within an otherwise generally unmodified silica glass. P.sub.2 O.sub.5 is at a maximum in the axial core region, while B.sub.2 O.sub.3 is generally the only modifier in the peripheral core region. The defined profile, which depends critically upon P.sub.2 O.sub.5 content in the axial composition and somewhat less critically upon the B.sub.2 O.sub.3 peripheral composition content, is near optimum from the standpoint of mode dispersion and remains so for the entire useful range of carrier wavelength (generally defined as from 0.5 to 1.1 .mu.m). Numerical aperture for fibers of the invention are typically at a level of 0.3.

Multimode optical fiber

High silica content optical glasses, containing more volatile oxides such as GeO.sub.2 and B.sub.2 O.sub.3, are produced by plasma fusion of powders without inordinately high loss of the more volatile constituents. The powders are produced by a process including the heat treatment of intimately mixed materials, which include the glass forming constituents. Small quantities of GeO.sub.2 are included in borosilicate glass to suppress bubble formation. Pairs of glass compositions have been found, with sufficient index of refraction difference to produce guidance in optical transmission lines, while possessing sufficient thermal expansion match to reduce stresses in the line.

GeO.sub.2 -B.sub.2 O.sub.3 -SiO.sub.2  Optical glass and lightguides

A multimode optical fiber waveguide with graded refractive index for lessening modal dispersion with the gradient produced at least in part by radially decreasing boron oxide content outwardly from the core center within a high silica glass core minimizes modal dispersion by use of a non-parabolic grading function. The optimum gradient for a simple binary borosilicate system for a wavelength of from approximately 0.5 to 1.1 micrometers corresponds with .alpha. = 1.77 .+-. 10 percent in the equation n = n.sub.1 [1-2.DELTA.(r/a).sup..alpha.].sup.1/2, in which n.sub.1 is the axial core index r is the distance from the fiber axis, a is the core radius, .DELTA. is the relative index difference between core center and cladding and .alpha. is a power law exponent which characterizes the profile.

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Fanwood, NJ, United States of America

James W Fleming, Jr