Optical waveguides – Optical transmission cable
Reexamination Certificate
1998-06-02
2001-02-27
Nguyen, Thong (Department: 2872)
Optical waveguides
Optical transmission cable
C385S103000, C385S107000
Reexamination Certificate
active
06195486
ABSTRACT:
The present invention relates to fiber optic cables and, more particularly, to water blocking features of fiber optic cables.
Fiber optic cables include optical fibers which transmit information in cable television, computer, and telephone systems. A fiber optic cable may be installed in an environment where the cable is exposed to water. The migration of water in a fiber optic cable may occur where the cable jacket has been breached and water enters the cable. The migration of water in a cable may cause the flooding of a cable passageway or enclosure, and/or it may negatively affect the performance of the optical fibers. Interstices between a jacket section and the core of the cable present potential water migration paths.
To block the flow of water in the interstices, known fiber optic cables may include a flooding compound, and/or a more craft-friendly, dry water absorbent substance. A typical water absorbent substance includes a polymer chain with reaction sites that react with water, thereby transforming the water absorbent substance into an expanded mass of viscous gel. The viscous gel acts as a physical barrier to the migration of water.
U.S. Pat. No. 5,179,611 discloses a slotted rod type fiber optic cable that includes a water absorptive tape disposed between a jacket section and the slotted rod. The tape is a non-woven fabric, a paper or other sheet-like material, which is topically coated or impregnated with a combination of a thermoplastic elastomer binding agent and a water absorptive resin combined with a water soluble resin. Application of the water absorptive tape to the slotted rod requires manufacturing equipment that is expensive to purchase and to maintain. Additionally, the water absorptive tape is a cable component that adds to the cost, size, and weight of the cable. Further, a craftsman will be obliged to perform the time consuming task of cutting and removing tape binders and the water absorptive tape in order to gain access to optical fibers in the cable.
A patent assigned to the assignee hereof discloses a fiber optic cable which eliminates the necessity for a water absorptive tape. U.S. Pat. No. 5,188,883 discloses an armor tape having an ethylene copolymer coating to which a layer of a swellable water blocking material is bonded. In a first method of making the armor tape, the layers are bonded together by heating the ethylene copolymer to soften it and then pressing the metal and water blocking tape layers together. In an alternative method of making the armor tape, the swellable material is applied directly to and is bonded with the coated metal tape layer. This alternative method is accomplished by heating and thereby softening the ethylene copolymer, and then depositing particles of the water swellable material directly on the softened copolymer by way of gravity acting on the particles as they are dispensed from a hopper. The water swellable tape of the first method may be expensive, and the application of the tapes to a cable core requires expensive manufacturing equipment. The manufacturing steps associated with wrapping the tape about the core contributes to the cost of production of the cable, and the use of a heater to soften the ethylene copolymer may likewise slow production speeds and increase costs.
OBJECTS OF THE INVENTION
In view of the foregoing, it is an object of the present invention to provide a fiber optic cable that includes a at least one optical fiber, a cable jacket, and a cable component associated with the cable jacket, the cable component including a water blocking formulation disposed on a substrate, the water blocking formulation comprising a radiation curable resin and an absorptive substance at least partially embedded therein.
It is another object of the present invention to provide a fiber optic cable that includes a cable core including at least one optical fiber, a cable component associated with the cable core and at least partially surrounding the cable core, the cable component having a water blocking formulation disposed on a substrate, the water blocking formulation comprising a radiation curable resin and an absorptive substance therein.
It is an object of the present invention to provide a fiber optic cable that includes a least one optical fiber, a component disposed within the cable between a core and a jacket section of the cable, the component including a substrate with a composite water blocking formulation disposed thereon, the composite water blocking formulation comprising a radiation curable resin, an absorptive substance at least partially embedded in the radiation curable resin, and a non-compatible material dispersed in the radiation curable resin.
It is a further object of the present invention to provide a method of making a fiber optic cable with at least one optical fiber, the method having the steps of coating a substrate with a radiation curable resin, creating a water blocking formulation by depositing an absorptive substance on the resin so that the absorptive substance becomes at least partially embedded in the resin, irradiating the water blocking formulation with a radiation source that emits radiation in the infrared wavelength region or with radiation having shorter wavelengths, curing the water blocking formulation with the radiation-emitting radiation source, and incorporating the substrate and the water blocking formulation in the fiber optic cable.
It is an object of the present invention to provide a method of making a fiber optic cable including the steps of creating a water blocking formulation comprising a radiation curable resin and an absorptive substance compounded in the radiation curable resin, coating a substrate with the water blocking formulation so that the absorptive substance is at least partially embedded in the resin, irradiating the water blocking formulation with a radiation source that emits radiation in the infrared wavelength region or with radiation having shorter wavelengths, curing the water blocking formulation with the radiation-emitting radiation source, and incorporating the substrate and water blocking formulation in the fiber optic cable.
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Field Larry W.
Patel Naren I.
Aberle Timothy J.
Boutsikaris Leo
Nguyen Thong
Siecor Operations LLC
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