Optical waveguides – Optical transmission cable – Tightly confined
Reexamination Certificate
1999-02-26
2001-01-09
Nguyen, Thong (Department: 2874)
Optical waveguides
Optical transmission cable
Tightly confined
C385S104000, C385S105000, C385S106000, C385S109000
Reexamination Certificate
active
06173100
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to cables and, in particular, to cables incorporating tapes which provide water-blocking and flame-retarding characteristics to the cables.
2. Description of the Related Art
Many products, such as telecommunications and power cables, for instance, typically are provided with one or more forms of water-blocking protection, i.e. waterproof outer jackets, water-blocking powders and yarns, etc. Generally, such water-blocking protection is intended to reduce or eliminate the possibility of water entering the product so as to reduce the potential of water damaging the product. For example, once water enters a telecommunications cable, such as through a splice closure of the cable, freezing of the water can induce microbending in the optical fibers of the cable, potentially resulting in fiber degradation or increased signal loss of the cable.
Heretofore, some prior art cables have incorporated water-blocking tape in order to prevent water penetration into and migration through the cables. Examples of such prior art cables are described in U.S. Pat. No. 4,867,526, issued to Arroyo, for instance. In the cables described in U.S. Pat. No. 4,867,526, water-blocking tape is disposed between the transmission media and the outer jacket of the cable, thereby forming a water-blocking barrier around the transmission media, i.e. optical fibers. The water-blocking tape incorporates superabsorbent materials, e.g. superabsorbent polymers (SAPs), which can absorb up to about one thousand (1000) times their weight in distilled water. The SAPs are provided in a loading of approximately 3.8-6.22 g/ft
2
, which results in a tape that weighs approximately 10-80% more than the substrate of the tape. Upon contact with water, the SAPs of the water-blocking tape absorb the water and swell, thereby preventing migration of the water through the cable. Additionally, the swollen SAPs form a physical barrier which can prevent more water from entering the cable.
In some applications, it is desirable to provide tapes which incorporate both water-blocking and flame-retarding characteristics. Heretofore, a prior art solution to attain the characteristics of water-blocking and flame-retarding has been to add flame-retardants to the SAPs of the tapes. However, adding flame-retardants to the SAPs oftentimes results in a tape which has reduced water-blocking characteristics as compared to the tape without the flame-retardants. Primarily, this is due to the chemical properties of the prior art flame-retardants which, typically, are salts or ionic compounds and are known to reduce the swelling of water-blocking materials. Generally, as more prior art flame-retardants are added to SAPs in an effort to improve the flame-retarding characteristics, the greater the water-blocking capacity of the SAPs is reduced. Frequently, the extent of reduction in water-blocking capacity of SAPs due to the incorporation of prior art flame-retardants can render the SAPs incapable of preventing water penetration.
Therefore, there is a need to provide improved cables and tapes which address these and other shortcomings of the prior art.
BRIEF SUMMARY OF THE INVENTION
Certain objects, advantages and novel features of the invention will be set forth in part in the description that follows and in part will become apparent to those skilled in the art upon examination of the following or may be learned with the practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
The present invention generally is directed to water-blocking tapes and cables with flame-retarding characteristics. In a preferred embodiment, a tape incorporates a first layer and SAPs, with the SAPs being applied to the first layer. Preferably, the first layer is formed of spun bonded non-woven polyester material, nylon spun bonded fabric, non-woven glass, polypropylene melt blown non-woven fabric, polyurethane spun bonded fabric, or TCF cellulose fabric, among others. Additionally, the SAPs are provided with a moisture content of greater than approximately 2 percent, by weight, thereby improving the flame-retarding characteristics of the tape.
In accordance with another aspect of the present invention, an embodiment of the tape incorporates greater than 6.22 grams, preferably at least 8 grams, of SAPs per square foot. Preferably, the SAPs include polyacrylates, polyacrylamides, polyvinylalcohols, and copolymers thereof, among others. In some embodiments, the SAPs can comprise at least 50% of the total weight of the tape.
In accordance with another aspect of the present invention, some embodiments of the tape can be configured with a second layer, with the SAPs being disposed between the first and second layers. Preferably, the tape is less than approximately 0.016 inches thick.
In accordance with still another aspect of the present invention, cables, such as telecommunications and power cables, for instance, are provided that possess water-blocking and flame-retarding characteristics. In a preferred embodiment, a cable of the present invention incorporates a core, an outer jacket surrounding the core, and tape disposed between the core and the outer jacket. The tape includes a first layer and SAPs, with the SAPs having a moisture content of greater than approximately 2 percent, by weight.
The numerous features and advantages of the present invention will be more readily apparent from the following detailed description read in conjunction with the accompanying drawings.
REFERENCES:
patent: 4867526 (1989-09-01), Arroyo
patent: 5133034 (1992-07-01), Arroyo
patent: 5163115 (1992-11-01), Sheu
patent: 5243675 (1993-09-01), Kathiresan
C. John Arroyo, Jim J. Sheu, and W.J. Paucke, The Use of Superabsorbent Materials in Optical Fiber Cable Design, 1991.
Fredric L. Buchholz and Nicholas A. Peppas, Superabsorbent Polymers, Science and Technology, 1993.
Fredric L. Buchholz and Andrew T. Graham, Modern Superabsorbent Polymer Technology, 1998.
Lisa-Brannon-Peppas and Ronald S. Harland, Absorbent Polymers Technology, Studies in Polymer Science 8, 1990.
Meeks Jennifer R.
Newton Wayne M.
Sheu Jim J.
Shmukler Mark I.
Wilson Carla G.
Boutsikaris Leo
Lucent Technologies - Inc.
Nguyen Thong
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