Optical waveguides – Optical transmission cable – Loose tube type
Reexamination Certificate
1998-09-10
2001-07-10
Ngo, Hung N. (Department: 2874)
Optical waveguides
Optical transmission cable
Loose tube type
C385S114000
Reexamination Certificate
active
06259844
ABSTRACT:
The present invention relates to fiber optic cables, and, more particularly, to fiber optic cables of the type having at least one strength member.
Conventional fiber optic cables include optical fibers that conduct light which is used to transmit voice, video, and data information. Where the fiber optic cable is subjected to crushing forces, the optical fibers may be stressed and attenuation of the transmitted light may occur. It is therefore important for fiber optic cables to be constructed in a robust manner whereby attenuation due to crush induced stresses can be avoided. Additionally, although it is desirable for a fiber optic cable to have a high optical fiber count, it is also desirable for the cable to be as compact as possible.
Conventional fiber optic cables should be able to withstand longitudinal compression and tension, and they typically include strength members for these purposes. However, the strength members may disadvantageously affect cable bending performance during installation, and may hinder optical fiber access. A fiber optic cable having strength members located in a single plane generally will experience a preferential bending action favoring bending of the cable out of the plane defined by the strength members. On the other hand, a fiber optic cable having strength members at spaced locations encircling the center of the cable will not have a preferential bend, but the strength members typically include a helical lay so that the cable can be bent. Even taking into account the helical lay of the strength members, when bent in generally any axis, cables of the non-preferential bend type may be very stiff, a characteristic which may be highly undesirable depending upon installation requirements. Thus a cable of the preferential bend type will typically experience ease of cable bending in a preferred axis, and, as there are less strength members to deal with, may present a less time consuming optical fiber access procedure. A cable designer may therefore balance the need to have sufficient cable components for resisting crush, compression, and tension loads, against the size and stiffness contributions of the cable components that may render the cable difficult to install in a cable passageway.
An example of a known preferential bend type fiber optic cable is disclosed in U.S. Pat. No. 5,509,097. This known cable requires a hot melt adhesive or epoxy which bonds the strength members to a core tube. The adhesive/epoxy may be combined with a helically wound tape or cord wrapped about the strength members under tension, thereby applying radially inward forces to the strength members and forcing the strength members against the tube. Due to the size and stiffness contributions of the cable components, this known cable may be undesirably stiff for some cable installations. Additionally, the cord, tape, and adhesive/epoxy add expense to the cable product and may complicate/slow the manufacturing process. Moreover, large gaps exist adjacent the strength members between the jacket and the core tube which may negatively affect the crush performance of the cable.
An example of a known non-preferential bend type fiber optic cable is disclosed in U.S. Pat. No. 4,730,894, which is incorporated by reference herein in its entirety. This known cable includes a layer of strength members adhesively bonded to a plastic tape and wrapped about a core tube; however, the cable may be undesirably stiff for some cable installations. Additionally, the plastic tape and adhesive add size and expense to the cable product and may complicate/slow the manufacturing process. Moreover, the lack of a tight coupling between the plastic tape and the core tube may negatively affect the crush performance of the cable. Other non-preferential bend type cables may be expensive and/or undesirably stiff as they include, in addition to a core tube, a helically grooved outer tube having helically laid trapezium shaped reinforcing members bonded thereto. The reinforcing members are made of a material that weakly bonds to the slotted rod.
OBJECTS OF THE INVENTION
It is an object of the present invention to provide a fiber optic cable having at least one optical fiber in a tube and strength assemblies adjacent the tube for imparting crush resistance to the cable. The strength assemblies may include at least two opposed strength members imparting a preferential bend resistance to the optical cable, at least one of the strength members being in contact with a first jacket, and being surrounded by an armor tape and a second jacket.
It is another object of the present invention to provide a non-preferential bend type fiber optic cable having strength assemblies adjacent a tube for imparting crush resistance to the cable, at least one of the strength assemblies including a strength member in contact with a tube having at least one optical fiber therein. The strength member is coupled to a first jacket, and is surrounded by an armor tape and a second jacket.
It is an object of the present invention to provide a fiber optic cable comprising: at least one optical fiber in a tube; strength assemblies having at least one strength member in contact with a jacket and in contact with the tube, the jacket being in contact with the tube, so that crush loads applied to the cable create stress therein which flows to the jacket in contact with the tube, and to the tube and to the at least one strength member.
It is another object of the present invention to provide a fiber optic cable comprising: at least one optical fiber in a tube; strength assemblies having at least two longitudinally disposed strength members each that are in contact with each other, in contact with the tube, and in contact with at least one jacket surrounding the tube; the jacket being in contact with the tube, so that crush loads applied to the cable create stress which flows to the jacket in contact with the tube, to the strength members, and to the tube.
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Siecor Cable Product Code Guidebook Jul. 1997; SST-Ribbon Cables (12-216 Fibers); pp. 16 and 17.
Lucent Technology Product Sheet 1996; High Fiber Count AccuRibbon® Cable.
Gimblet Michael J.
Lail Jason C.
Logan Eric R.
Wagman Richard S.
Aberle Timothy J.
Ngo Hung N.
Siecor Operations LLC
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