Optical waveguides – Optical transmission cable – Ribbon cable
Reexamination Certificate
1999-09-15
2001-11-13
Schuberg, Darren (Department: 2872)
Optical waveguides
Optical transmission cable
Ribbon cable
C385S110000, C385S112000, C385S113000, C385S109000
Reexamination Certificate
active
06317542
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to fiber optic cables and, more particularly, to fiber optic cables with multiple stacks of optical fiber ribbons.
BACKGROUND OF THE INVENTION
Optical fiber is a very popular medium for large bandwidth applications, and as a result there is a demand for fiber optic cables with greater numbers of optical fibers. In response to demands for increased optical fiber count in fiber optic cables, optical fiber ribbons have been developed. Optical fiber ribbons are planar arrays of optical fibers that are bonded together as a unit. Optical fiber ribbons are advantageous because many ribbons can be stacked on top of each other to form a stack of optical fiber ribbons.
It is conventional for stacks of optical fiber ribbons to be incorporated into two different types of fiber optic cables that are generally referred to as “central-core” and “loose-tube” cables. In the central-core design, a stack of optical fiber ribbons are contained within a central tube, which is located at the center of the fiber optic cable. Further, strength members are positioned between the central tube and an outer plastic jacket of the cable. In contrast, loose-tube fiber optic cables typically include a number of relatively small buffer tubes that are positioned around a central strength member, and each buffer tube encloses a stack of optical fiber ribbons. The buffer tubes are longitudinally stranded around the central strength member, meaning that the buffer tubes are rotated around the central strength member along the length of the fiber optic cable.
In an effort to increase the density of optical fibers within fiber optic cables, different arrangements of stacks of optical fiber ribbons have been proposed. For example, U.S. Pat. No. 5,878,180 discloses a fiber optic cable with uniform stacks of optical fibers in side-by-side arrangements.
Whereas advancements have been made in the area of increasing the density of optical fibers within fiber optic cables, further advancements and options in this area would be beneficial.
SUMMARY OF THE INVENTION
The present invention provides advancements and options related to increasing the density of optical fibers within fiber optic cables. For example, in accordance with one aspect of the present invention, a fiber optic cable includes multiple differently sized stacks of optical fiber ribbons. More specifically, each of those stacks is positioned within a passage defined by a jacket. The stacks include a central stack that is approximately centrally located in the jacket passage and peripheral stacks positioned radially around the central stack. In an end elevation view thereof, the periphery of each stack defines a first cross-dimension between a first pair of opposite sides that are defined by edges of the optical fiber ribbons of the stack. In the end elevation view thereof, each stack further defines a second cross-dimension between a second pair of sides that are defined by one of the lateral surfaces of one of the optical fiber ribbons of the stack and one of the lateral surfaces of another of the optical fiber ribbons of the stack. A difference exists between the dimensions of the central stack and the dimensions of one or more of the peripheral stacks. For example, the first cross-dimension of the central stack can be different from the first cross-dimension of one or more peripheral stacks and/or the second cross-dimensions of the central stack can be different from the second cross-dimension of one or more peripheral stacks. For example, optimum packing efficiency may be achieved with the central stack being wider than the peripheral stacks. Preferably a plurality of buffer encasements respectively contain the stacks, and each buffer encasement includes a longitudinally extending interior surface. For each buffer encasement, the interior surface thereof extends around and defines a longitudinally extending passage that contains the respective stack, and each interior surface closely bounds and engages the periphery of the respective peripheral stack. Preferably the buffer encasements are thin.
In accordance with another aspect of the present invention, a fiber optic cable has a jacket extending in a longitudinal direction and defining a longitudinally extending jacket passage. Multiple longitudinally extending stacks of optical fiber ribbons are within the jacket passage. The stacks include a central stack that is approximately centrally located in the jacket passage, and peripheral stacks positioned radially around the central stack. Buffer encasements that respectively contain the peripheral stacks are longitudinally stranded around the central stack. Each buffer encasement includes a longitudinally extending interior surface that extends around and defines a longitudinally extending passage that contains the respective peripheral stack, and each interior surface closely bounds and engages a substantial portion of the periphery of the respective peripheral stack. In accordance with one example, the fiber optic cable further includes a longitudinally extending central member, which can be a strength member or a spacer, defining a longitudinally extending central passage that contains the central stack, and the buffer encasements are longitudinally stranded around the central member. The exterior surface of the central member can define a generally polygon-like shape having a number of sides that corresponds to the number of peripheral stacks. In addition, the exterior surface of the central member can define a generally round shape. Further, the exterior surface of the central member can define lay lengths that correspond to the lay length defined by the peripheral stacks.
In accordance with another aspect of the present invention, a fiber optic cable includes multiple optical modules within a longitudinally extending jacket and longitudinally stranded around a central member. Each optical module includes a stack of optical fiber ribbons enclosed in a buffer encasement. Each buffer encasement includes a longitudinally extending interior surface that extends around and defines a longitudinally extending passage that contains the respective stack, with the interior surface closely bounding and engaging a substantial portion of the periphery of the respective stack. Preferably the buffer encasements are thin.
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Satomi Hatano et al., Multi-Hundred-Fiber Cable Composed of Optical Fiber Ribbons Inserted Tightly into Slots; International Wire & Cable Symposium Proceedings, 1986, pp. 17-23.
Hardwick, III Nathan E.
Jackson Kenneth Wade
Lever Clyde Jefferson
Norris Richard Hartford
Sheu Jim Jenqtsong
Boutsikaris Leo
Lucent Technologies - Inc.
Schuberg Darren
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