Glass manufacturing – Processes of manufacturing fibers – filaments – or preforms – Process of manufacturing optical fibers – waveguides – or...
Reexamination Certificate
1999-05-27
2001-10-23
Colaianni, Michael P. (Department: 1731)
Glass manufacturing
Processes of manufacturing fibers, filaments, or preforms
Process of manufacturing optical fibers, waveguides, or...
C065S406000, C065S435000, C065S433000, C065S436000, C065S036000, C065S385000, C156S089110, C156S308200, C264S430000, C264S483000
Reexamination Certificate
active
06305195
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to optical fiber fabrication.
2. Discussion of the Related Art
Glass optical fiber has become a significant transmission medium in recent years, and its prevalence in communications systems is expected to increase. Glass optical fiber is generally produced from a glass preform, the preform typically consisting of a doped silica core surrounded by an inner silica cladding and a silica overcladding. As reflected in
FIG. 1
, and discussed in F. DiMarcello et al. “Fiber Drawing and Strength Properties,”
Optical Fiber Communications
, Vol. 1, Academic Press, Inc., 1995, at 179-248, the preform
12
is generally arranged vertically in a draw tower
10
such that a portion of the preform
12
is lowered into a furnace region
14
that typically heats the preform
12
to temperatures around 2200° C. The portion of the preform
12
placed into the furnace region
14
begins to melt, and the lower end of the preform
12
forms what is known as the neck-down region
16
, which is where the preform glass flows from the original cross-sectional area of the preform
12
to the desired cross-sectional area of the fiber
18
. From the lower tip of this neck-down region
16
, the optical fiber
18
is drawn. As the preform glass is drawn into fiber
18
, the preform
12
continues to be lowered into the furnace region
14
, until the preform
12
is exhausted.
Clearly, the need to interrupt this fiber drawing process to put a new preform in place reduces efficiency of the process and reduces the consistency of the resultant fiber. Specifically, significant down-time is accumulated when putting new preforms in place and performing the initial drop of the preform into draw position. Moreover, significant waste is generated in re-establishing the draw from each new preform. Thus, techniques for fabricating more fiber from a single preform have been sought. However, the length of preforms is somewhat limited by the processes used to make them, and increasing preform diameter has therefore been considered to be the primary method for improving the efficiency of fiber fabrication. Yet, the parameters for consistently obtaining commercially acceptable fibers from such larger diameter preforms are not clear. Problems encountered with the current preforms are likely to be exacerbated in larger diameter preforms, and new, unforeseen problems are also likely to arise.
Thus, improved methods for more efficiently fabricating optical fiber are desired, in particular methods that reduce down-time and waste.
SUMMARY OF THE INVENTION
The invention provides an improved process for fabricating a refractory a dielectric article, in particular silica optical fiber. The fabrication process involves joining of two elongated bodies—typically silica preforms—end-to-end by use of an isothermal plasma torch technique. A long preform made in this manner allows drawing of a substantial length of optical fiber with less down-time and waste than current processes. In fact, according to the invention, a continuous draw process is possible, in which discrete preforms are successively joined to the top end of a preform from which fiber is being drawn. The plasma torch technique also is able to produce a low level of perturbations around the joint area, as well as a low level of impurities such as OH, such that any detrimental effect of the joint on the drawn fiber is kept similarly low. (Refractory indicates a ceramic material of relatively low thermal conductivity that is capable of withstanding temperatures of up to about 1600° C. without essential change. Dielectric indicates an electrically insulating material, i.e., a material having a resistivity of about 10
6
ohm-cm or greater.)
According to the invention, a first elongated refractory dielectric body having at least one end face and a second elongated refractory dielectric body having at least one end face are provided. The bodies are oriented such that end faces are opposite each other, and these opposing end faces are heated with an isothermal plasma torch to lower the viscosity of, e.g., liquify, the end faces. At least one of the bodies is then moved until the end faces are joined. Advantageously, the bodies are silica-based optical fiber preforms. At least one of the preform end faces typically has a conical shape, e.g., at an angle of 3° or less, such that melting and joining of the two ends provides a desirable joint substantially free of defects and porosity. The ends of the preforms are typically placed a few centimeters apart or less prior to heating, and the preforms are generally rotated during heating and joining. After joining, excess glass and/or deposited soot produced at the joint is able to be removed with the torch, and the preform is then ready for fiber fabrication. In the case of a continuous fiber draw process, a first preform (which may be a joined preform) is placed into a draw furnace, fiber draw is initiated, and an second preform is joined to the top of the first preform by the technique presented herein.
REFERENCES:
patent: 2564738 (1951-08-01), Tank et al.
patent: 3571559 (1971-03-01), Becker et al.
patent: 4390384 (1983-06-01), Turner
patent: 4724020 (1988-02-01), Ebata et al.
patent: 4900389 (1990-02-01), Schnell et al.
patent: 5509952 (1996-04-01), Moore et al.
patent: 5551968 (1996-09-01), Pan
patent: 5578106 (1996-11-01), Fleming, Jr. et al.
patent: 5689608 (1997-11-01), Moore et al.
patent: 6178779 (2001-01-01), Drouart et al.
patent: 2932196A (1981-02-01), None
patent: 3929894A (1991-03-01), None
patent: 0656325 (1995-06-01), None
patent: 0950643A (1999-10-01), None
patent: 61197440 (1987-01-01), None
patent: 5024877 (1993-02-01), None
patent: 05024877 (1993-02-01), None
patent: 10330130 (1994-11-01), None
patent: 6329443 (1994-11-01), None
patent: 06329433 (1994-11-01), None
patent: 08109036 (1996-04-01), None
patent: 10081529 (1998-03-01), None
patent: 10330130 (1998-12-01), None
F. DiMarcello et al. “Fiber Drawing and Strength Properties,”Optical Fiber Communications,vol. 1, Academic Press, Inc., pp. 179-248 (1995).
Fleming, Jr. James William
Zydzik George John
Agere Systems Guardian Corp.
Colaianni Michael P.
Rittman Scott J.
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