Glass manufacturing – Processes of manufacturing fibers – filaments – or preforms – Process of manufacturing optical fibers – waveguides – or...
Reexamination Certificate
1999-05-20
2002-06-04
Hoffmann, John (Department: 1731)
Glass manufacturing
Processes of manufacturing fibers, filaments, or preforms
Process of manufacturing optical fibers, waveguides, or...
C065S408000, C065S410000, C065S411000, C065S043000
Reexamination Certificate
active
06397636
ABSTRACT:
FIELD OF THE INVENTION
This application pertains to methods of making an optical fiber bundle, and to articles (e.g., an optical fiber amplifier or laser) that comprises such a bundle.
BACKGROUND OF THE INVENTION
Fiber bundles are used in a wide variety of optical applications including optical fiber amplifiers, couplers, splitters and cladding-pumped fiber lasers. In an exemplary application, a fiber bundle is used to couple light from a multiplicity of diode light sources to the inner cladding of a double clad fiber device. The bundle is made by fusing together individual optical fibers, typically also tapering the bundle to provide increased light intensity.
It is relatively straightforward to simply fuse multiple fibers into a bundle. However, it is generally difficult to make with high yield fiber bundles having high optical throughput. Thus, it would be desirable to have available a method of manufacturing reliably articles that comprise a fused fiber bundle and have high optical throughput. This application discloses such a method, and articles made be the method.
The technology for fusing two fibers together is well known. See, for instance, U.S. Pat. No. 4,439,221. See also Patent Abstracts of Japan, Unexamined Applications, Vol. 97, No. 8; 96JP-0014873, which discloses a process of making a fiber coupler that comprises coating the two bare fibers with a sol obtained by hydrolysis of silica acid ester (frequently referred to as “TEOS”), followed by heating of the coated fibers to fuse the fibers.
In a conventional process, two fibers are twisted together to bring them into intimate contact, and they are heated while the ends are being pulled apart. To combine more than two fibers, the same technique is conventionally used. See, for instance, U.S. patent applications Ser. Nos. 08/897,195 and 08/999,429, respectively filed Jul. 21, 1997 and Dec. 29, 1997 by DiGiovanni et al. for “Tapered Fiber Bundles for Coupling Light Into and Out of Cladding-Pumped Fiber Devices”, and “Method and Apparatus for Producing Fused Fiber Bundles”, respectively. U.S. Pat. Nos. 5,500,917 and 5,682,453 disclose an optical assembly that comprises a glass-based bonding compound and a method of making the assembly, respectively.
All patents, patent applications and other references cited herein are incorporated herein by reference.
Glossary and Definitions
By a “glass precursor material” we mean herein a liquid or particle-containing liquid which, upon heating, leaves an inorganic residue that comprises glassy silica as a major component. Such a material may be a colloidal sol in which glassy particles are suspended in a carrier liquid, e.g., fumed silica in an aqueous medium, or may be a silicon-containing compound which can be converted to silica by heating. An example of such a compound is waterglass (sodium silicate), which condenses upon drying and an subsequently be vitrified thermally. An exemplary organic silicon-containing compound is tetramethyl ammonium silicate, which forms a hard residue upon evaporation of its aqueous solvent. This residue reacts upon heating, forming a glass film as the organics burn away.
A “particle-free” glass precursor material is a glass precursor material to which no colloidal particles are intentionally added, and a “particle-containing” glass precursor material is a glass precursor material to which colloidal particle are added, or which forms colloidal particles.
By a “substantially planar” surface of an optical fiber we mean herein a surface that is nominally planar except for (typically unavoidable) minor departure from planarity. Such departures are inherent in, for instance, fibers that have been drawn from a preform of quadratic, rectangular, hexagonal, etc. cross section.
SUMMARY OF THE INVENTION
The instant invention is embodied in a method of making an article (e.g., an optical fiber amplifier or laser) that comprises a fused bundle of optical fibers, the method comprising the steps of providing a bundle of optical fibers, and heating said bundle of optical fibers such that said fused bundle of optical fibers results. Significantly, the method also comprises the step of applying, prior to said heating step, a glass precursor material to said bundle of fibers.
In a first embodiment of the invention, the glass precursor material comprises a colloidal sol (i.e., comprises colloidal particles), and in a second embodiment at least two of the optical fibers comprise substantially planar surfaces facing each other, and with the glass precursor material being particle-free glass precursor material.
Exemplary of colloidal particles that can be used in the practice of the invention is fumed silicia, and exemplary of particle-free precursor material is TEOS (partially hydrolized tetraethyl orthosilicate).
The former precursor material typically is used with bundles of fiber that contain (or are likely to contain) undesirably “gaps”, exemplarily bundles of fibers of nominally circular cross section, but not excluding bundles of fibers with substantially planar surfaces. A particle-free precursor material is typically used with substantially gap-less bundles that comprise fibers having substantially planar surface regions (e.g., fibers with quadratic, rectangular or hexagonal cross section, or with “D” shaped cross section). The particle-free precursor material serves to maintain, prior to fusing them, the fibers in the bundle in place, resulting in improved fused bundles.
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U.S. application No. 08/897,195 filed Jul. 21, 1997, by D.J. DiGiovanni, “Taped Fiber Bundles for Coupling Light Into and Out of Cladding-Pumped Fiber Devices”.
U.S. application No. 08/999,429 filed Dec. 29, 1997 by D.J. GiGiovanni, “Method and Apparatus for Producing Fused Fiber Bundles”.
DiGiovanni David John
Fishteyn Mikhail
Hoffmann John
Lowenstein & Sandler PC
Lucent Technologies - Inc.
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