Optical waveguides – Optical transmission cable – Loose tube type
Reexamination Certificate
1999-10-29
2001-07-03
Palmer, Phan T. H. (Department: 2874)
Optical waveguides
Optical transmission cable
Loose tube type
C385S106000, C385S112000, C385S107000
Reexamination Certificate
active
06256438
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to fiber optic cables and, more particularly, to fiber optic cables having water swellable elements for facilitating a dry construction.
BACKGROUND OF THE INVENTION
Fiber optic cables can be employed in a variety of applications including the transmission of voice and data in cable television, computer and telephone systems. Fiber optic cables can generally be classified into two categories, namely, trunk and distribution cables that are designed to span relatively long distances, and drop cables that span much shorter distances and that typically terminate at a home or business. Trunk and distribution cables are generally relatively large and rigid. For example, trunk and distribution cables typically include a relatively thick jacket and large core components protecting the optical fibers. Trunk and distribution cables can include one or more strength members resisting sharp twists or turns of the cable. As a result of their construction, trunk and distribution cables are generally expensive.
In contrast to trunk and distribution cables, fiber optic drop cables are typically relatively flexible. This flexibility facilitates twisting and turning of the drop cable during installation. Since fiber optic drop cables generally include fewer optical fibers and extend across shorter distances than fiber optic trunk and distribution cables, fiber optic drop cables are comparatively smaller and less expensive.
The introduction of water into a fiber optic cable and the migration of water therethrough can be a problem. Fiber optic cables typically define one or more internal passageways through which the optical fibers extend. Water that enters the passageway can migrate in the internal passageway and be conducted to a closure or other termination device. The water can then physically degrade the closure or other termination device and/or can damage electronics mounted within the closure or other termination device. In addition, any water that remains in the passageway defined by the fiber optic cable can disadvantageously subject the optical fibers to additional forces if the water were to freeze.
Several methods have been employed to inhibit the migration of water. For example, fiber optic cables have included a hydrophobic grease or gel that fills the internal passageways. While the hydrophobic grease or gel blocks the migration of moisture through the passageways, the fiber optic cable must be designed and the hydrophobic grease or gel must be selected such that the hydrophobic grease or gel is compatible with the materials that form the other elements of the fiber optic cable with which the hydrophobic grease or gel may contact. A buffer tube can define the internal passageway that is filled with hydrophobic grease or gel, in which case the buffer tube may have to be formed of a more expensive compatible polymer. In addition, fiber optic cables that include a hydrophobic grease or gel are generally more difficult to handle during their manufacture, installation and repair.
Fiber optic cables have also been designed that include elements formed of water swellable material, for a super absorbent polymer. The water swellable material is typically carried by yarns or tapes that are disposed within a passageway in the fiber optic cable. Upon contact with water, the water swellable material will absorb the water and swell so as to physically close the passageway, thereby preventing migration of water through the passageway. See, for example, U.S. Pat. Nos. 5,684,904 and 5,039,197, the contents of both of which are expressly incorporated herein by reference.
While various fiber optic cables have been designed to prevent the introduction of water into and the migration of water through the internal passageways defined by the fiber optic cables, most of these fiber optic cables are relatively large and/or expensive cables that are best suited for use as trunk and distribution cables.
SUMMARY OF THE INVENTION
In view of the foregoing, a fiber optic cable according to one aspect of the present invention comprises an armor layer having inner and outer surfaces and defining a passageway therethrough; a water swellable layer on at least one of the inner and outer surfaces of the armor layer for inhibiting water migration; a protective jacket surrounding the armor layer and the water swellable layer; and at least one optical fiber extending lengthwise through the passageway defined by the armor layer, the optical fiber being capable of contacting at least one of the water swellable layer and the armor layer.
A fiber optic cable according to another aspect of the present invention comprises an armor layer having inner and outer surfaces and defining a passageway therethrough, the armor layer comprising a metallic layer and a plastic coating on at least the inner surface of the metallic layer, the metallic layer being at least twice as thick as the plastic coating; a water swellable element disposed within the passageway defined by the armor layer for absorbing water that enters the passageway; a protective jacket surrounding the armor layer; and at least one optical fiber extending lengthwise through the passageway defined by the armor layer, the optical fiber being capable of contacting the plastic coating on the inner surface of the armor layer.
According to yet another aspect of the present invention, the fiber optic cable comprises a drop cable having an armor layer defining a passageway therethrough; a protective jacket surrounding the armor layer and having an outer diameter of about 6.4 mm; and at least one optical extending lengthwise through the passageway defined by the armor layer, wherein the fiber optic drop cable exhibits shape retention whereby the fiber optic drop cable retains a bent shape once the fiber optic drop cable has been bent. In one embodiment, the fiber optic cable of this aspect of the present invention can also include a water swellable element, such as a water swellable layer on the armor layer and/or at least one water swellable yarn disposed within the passageway.
REFERENCES:
patent: 3651244 (1972-03-01), Silver et al.
patent: 4322574 (1982-03-01), Bow et al.
patent: 4832444 (1989-05-01), Takahashi et al.
patent: 4846573 (1989-07-01), Taylor et al.
patent: 4867526 (1989-09-01), Arroyo
patent: 5000533 (1991-03-01), Gerwers
patent: 5039197 (1991-08-01), Rawlyk
patent: 5157752 (1992-10-01), Greveling et al.
patent: 5268971 (1993-12-01), Nilsson et al.
patent: 5684904 (1997-11-01), Bringuier et al.
patent: 5778652 (1998-07-01), Kunze
patent: 5917977 (1999-06-01), Barrett
patent: 6088499 (2000-07-01), Newton et al.
patent: 0 703 478 A1 (1995-03-01), None
Aberle Timothy J.
Palmer Phan T. H.
Siecor Operations LLC
LandOfFree
Fiber optic drop cable does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Fiber optic drop cable, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fiber optic drop cable will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2556182