Optical waveguides – Optical transmission cable – With electrical conductor in the same cable
Reexamination Certificate
1998-06-30
2001-02-27
Nguyen, Thong (Department: 2872)
Optical waveguides
Optical transmission cable
With electrical conductor in the same cable
C385S100000, C385S101000, C385S103000, C385S113000, C174S02300R, C174S07000A
Reexamination Certificate
active
06195487
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a composite cable for conveying electrical and optical energy, and more particularly, a composite cable for an optical fiber network containing electrically conductive elements for supplying electrical power and optical fibers for distributing optical signals.
BACKGROUND OF THE INVENTION
Optical fiber is now used in a variety of telecommunication applications because of its small physical size and high bandwidth capacity.
An optical fiber access network provides for the distribution of telecommunications data among various locations, such as between a central office (CO) and a location remote from the CO, often called an optical network unit (ONU), over optical fibers.
In many current optical access networks, the active components in the CO, which include optical and electrical devices, are powered by the power that a power utility supplies directly to the building or facility housing the CO. The ONU likewise requires electrical power for converting optical signals to electrical signals for further processing and distribution and for converting electrical signals to optical signals for transmission back through the fiber network to the CO. This power can originate from the same source in the CO, or more often, originate from a power source located remotely from the CO. This remote power source (RPS) typically converts AC power supplied by the power utility to a lower voltage DC power suitable for handling by communications craftspersons.
The most common method of carrying the power from the CO or RPS to the ONU is via a standard copper twisted-pair telephone cable or a standard coaxial cable, neither of which contains optical fiber. In addition, it has been proposed to carry the power by using a composite cable including groups of twisted-pair telephone wires bundled together in some fashion with a plastic tube or tubes containing optical fibers. See U.S. Pat. No. 5,268,971, incorporated by reference herein.
These composite cables, however, are unsatisfactory in terms of their size, scalability, maneuverability and taut-sheath accessibility. Conventional composite cables which contain electrical conductors arranged as twisted pairs or bundles have a large diameter and are heavy in weight. These conventional cables are of such size and weight because two wires which are twisted as opposed to untwisted or wires which are grouped as opposed to layered require excess space. The space requirement of the electrical conductor portion of these composite cables typically constitutes the greatest proportion of the composite cable. The contribution of the electrical conductors to the size of the composite cable limits the scalability of the cable design in terms of the number of optical fibers and electrical conductors which can be included during cable manufacture, because the size of the cables utilized in optical fiber networks must satisfy preset standards as to duct sizes, splice enclosures entrance ports, installation equipment and termination hardware. Also, a composite cable which is heavy and has a large diameter is extremely bulky and, thus, hard to maneuver in storage and installation. In addition, conventional composite cables are not constructed to allow for ease of mid-span or taut-sheath access to the optical fibers without damage to the electrical conductors when the electrical conductors surround the optical fibers in the composite cable.
Furthermore, the need for twisting the telephone wires when they are used for power distribution is disappearing in modern fiber access networks because of an increased confidence in the reliability of the fiber network as the only communications medium and a decreased interest in having communication-grade twisted-pairs available for future use.
Therefore, there exists a need for a composite cable which is compact, has a small diameter, is lightweight, mechanically protects the optical fibers from damage, is scalable in terms of optical fiber and electrical conductor capacity, is easy to install and terminate, allows for ease of mid-span or taut-sheath fiber access without harm to either the fibers or the conductors and is compatible with modern optical access network limitations and standards.
SUMMARY OF THE INVENTION
In accordance with the present invention, a composite cable for conveying optical signals and electrical power includes at least one plastic buffer tube which loosely contains at least one optical fiber, a water swellable tape or yarn disposed around and extending longitudinally along the length of the at least one buffer tube and at least one layer of electrical conductors disposed around the water swellable tape or yarn. Each of the conductors includes a plastic insulation outer covering and is arranged in the layer of conductors to provide that the layer of conductors is compact and has a thickness which does not exceed the thickness of a single insulated conductor. In addition, the conductors are S-Z stranded longitudinally along the length of the cable to provide flexibility and ease of mid-span and taut-sheath access to optical fibers or other conductors in the composite cable surrounded by the layer of conductors. An outer plastic jacket surrounds the layer of conductors.
In a preferred embodiment, the composite cable includes a central plastic buffer tube which loosely contains at least one optical fiber and includes a flowable water blocking material, such as a thixotropic gel, which fills any empty spaces in the buffer tube and does not restrict movement of the optical fibers in the buffer rube. A first water swellable tape or yarn is disposed around and extends longitudinally along the length of the buffer tube. A layer of insulated conductors, each having substantially the same diameter, is disposed around the water swellable tape. The conductors are in side-by-side relation and are S-Z stranded longitudinally along the length of the central buffer tube. Thus, the layer of conductors has a radial thickness substantially equal to the diameters of the insulated conductors. A second water swellable tape or yarn is disposed around and extends longitudinally along the length of the layer of conductors. A layer of strength members is disposed around the second water swellable tape or yarn and extends longitudinally along the length of the cable. An inner plastic jacket surrounds the layer of strength members and a conductive armor is disposed around the inner jacket and extends longitudinally along the length of the cable. An outer plastic jacket surrounds the conductive armor.
In alternative embodiments, the central loose tube composite cable includes a plurality of radially separated layers of insulated conductors where the conductors in a layer have substantially the same diameter and are in side-by-side relation. Therefore, each layer of conductors is not thicker than the thickness of a single conductor in the layer. The conductors in at least one of the layers of conductors are S-Z stranded longitudinally along the length of the cable. A water swellable tape or yarn extending longitudinally along the length of the cable is disposed between adjacent layers of conductors and between the outermost layer of conductors and the layer of strength members.
In another preferred embodiment, the composite cable includes a central strength member surrounded by plastic insulation and a plurality of S-Z stranded plastic buffer tubes surrounding and extending longitudinally along the length of the central strength member. Each of the tubes loosely contains at least one optical fiber. A water swellable tape or yarn is disposed around the S-Z stranded buffer tubes and extends longitudinally along the length of the cable. A first inner plastic jacket surrounds the water swellable tape or yarn. At least one layer of insulated conductors having a thickness that does not exceed the diameter of the insulated conductors is disposed around the first inner jacket. The conductors in the layer of conductors are S-Z stranded longitudinally along the length of the cable. A second in
Anderson Aaron
Davidson Grant
Sach John
Brooks L. P.
Curtis Craig
Nguyen Thong
Norris, Mc Laughlin & Marcus
Pirelli Cable Corporation
LandOfFree
Composite cable for access networks does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Composite cable for access networks, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Composite cable for access networks will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2614307