Optical waveguides – Optical transmission cable – Ribbon cable
Reexamination Certificate
1999-11-01
2001-11-20
Bovernick, Rodney (Department: 2874)
Optical waveguides
Optical transmission cable
Ribbon cable
C385S128000
Reexamination Certificate
active
06321014
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to methods for manufacturing optical fiber ribbon and, more specifically, methods for manufacturing optical fiber ribbon containing optical fibers having coatings applied when the fibers are first drawn, the coatings being colored by the incorporation of a coloring agent, the methods advantageously avoiding a separate inking step and avoiding waste.
2. Description of the Related Prior Art
In conventional optical fiber ribbon, coated optical fibers usually in counts of four, eight or twelve fibers, are arranged in parallel and bundled together by a radiation-curable matrix material. Each fiber contains a primary coating and a secondary coating. The primary coating, which is applied directly onto the glass, is formulated to give a coating of low modulus and T
g
(glass transition temperature) in order to buffer the fiber from stresses that induce microbending of the fiber. The secondary coating is designed to have a higher modulus and T
g
to provide solvent and abrasion resistance.
The first step in the production of optical fiber ribbon includes the selection of appropriate optical fibers taking into consideration any relevant criteria and especially the coated diameter of the fibers. The coated fibers are then further coated, usually off-line, with an ink layer, typically 1 to 5 microns in thickness. That is, the fibers having the primary and secondary coatings thereon are removed from the spool and coated with an ink layer which is usually a radiation-curable coating composition containing a pigment system for color. The ink coating layer is then cured, and the,optical fiber having the primary, secondary and ink coating layers thereon is placed on a spool. The desired number of fibers coated in this manner are then placed on a so-called “payoff tree” which is an apparatus including one or more wheels that feed out the fibers in a manner whereby the tension in each fiber is controlled using a system of pulleys.
Following payoff from the spools, the coated fibers in the desired number are arranged in a flat plane, in a manner whereby they are just touching. The fibers are then encapsulated in a radiation-curable matrix material by passing the fibers through a first slit-shaped matrix die after which a liquid matrix material, usually a urethane acrylate material, is applied to the fibers. After passing through a second slit-shaped matrix die to remove excess matrix material, the fibers having the liquid matrix material applied thereto are subjected to actinic-radiation to cure the matrix material. The optical fiber ribbons are then placed on a spool, usually in 25 km lengths.
The application of the ink layer in a separate inking step is disadvantageous because it is costly. Additionally, in the conventional manner of applying the ink coating, lumps in the ink coating sometimes occur which causes variations in the thickness of the ink coating and breakage of the fiber. Also, matching the overall fiber diameters for a set of 4 to 12 fibers with different colored ink coatings is often difficult because of variations that occur in the thickness of the ink coating.
SUMMARY OF THE INVENTION
Accordingly, an object of the invention is to provide an improved method for preparing optical fiber ribbon whereby the need for a separate step for coating the optical fibers of the ribbon with an ink coating layer is eliminated.
Another object of the invention is to provide improved optical fiber ribbons containing colored optical fibers, the optical fiber ribbons being prepared without a separate inking step and including a colored secondary coating, the secondary coating and matrix material being substantially unreacted together.
These objectives and other objectives are achieved by providing a method for manufacturing optical fiber ribbon including coating a plurality of optical fibers with a primary coating composition and curing the primary coating composition to form a primary coating layer on the optical fibers. The optical fibers having the primary coating layer thereon are coated with a secondary coating composition containing pigments, dyes, and/or a colored reactive component in an amount effective for inking the optical fibers, and a photoinitiator in an amount effective for coloring initiating curing of the secondary coating composition upon exposure to actinic radiation. The preferred photoinitiator is insensitive to the free-radical quenching effects of oxygen. The oxygen adjacent said secondary coating composition is substantially eliminated and the bulk and surface of the secondary coating composition are at least substantially completely cured. The optical fibers having the primary coating layer and the secondary coating layer thereon are encapsulated with a matrix material. The encapsulation is conducted while the secondary coating composition is at least substantially completely cured, whereby the matrix material and the secondary coating are adjoining but substantially unreacted with each other.
An optical fiber ribbon is also provided. The optical fiber ribbon includes a plurality of optical fibers each of which has a primary coating layer and a secondary coating layer. The secondary coating layer is prepared from a secondary coating composition colored as described above. A matrix material encapsulates the optical fibers having the primary and secondary coating layers thereon. The matrix material and the secondary coating layer are adjoining but substantially unreacted with each other.
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Greer Robert W.
Overton Bob James
Purvis Michael B.
Stupak Peter R.
Yang Houching Michael
Alcatel
Bovernick Rodney
Connelly-Cushwa Michelle R.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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