Optical waveguides – Optical transmission cable – Tightly confined
Reexamination Certificate
1999-08-30
2001-11-20
Mack, Ricky (Department: 2873)
Optical waveguides
Optical transmission cable
Tightly confined
C385S112000
Reexamination Certificate
active
06321012
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical fiber communication cable in which the optical fibers and/or ribbons are bound and assorted into groups by using water swellable material having indicia (e.g., different colors, color strips/prints and/or simply mono-color strips/prints) to distinguish the groups.
2. Discussion of Related Art
Conventional optical fiber cables include optical fibers that are sometimes grouped together in sets (with each set having one or more, e.g., twelve, optical fibers) with each fiber in a particular set having a unique color. Thus, within a single set, the optical fibers are coated with distinctly different colors. These distinct colors are repetitively used for each set, so that if there are three sets of optical fibers, the optical fiber cable will have, e.g., three red optical fibers, three green optical fibers, etc. In order to distinguish between optical fibers having the same color, it is necessary to color code each set of optical fibers. To accomplish this, the optical fiber sets are wrapped by different colored binder threads such that, e.g., a first set is held together by a blue binder thread, a second set is held together by a yellow binder thread and a third set is held together by an orange binder thread, and so on and so forth. In this way, one can identify the optical fibers by the specific color of the optical fiber and the associated color of the optical fiber set, e.g. red optical fiber of the blue optical fiber set or the green optical fiber of the yellow optical fiber set. This arrangement is illustrated in
FIGS. 1 and 2
showing an optical fiber cable
10
having four optical fiber sets
12
respectively held together by colored binder threads
14
. The optical fiber sets
12
are enclosed in a buffer tube
16
and a water block gel
18
is filled in the space defined between the optical fibers. The buffer tubes are then encapsulated by an outer sheath
20
having rigid strengthening members
22
.
Although not shown, it is also known to wrap the optical fiber ribbons or tubes with a water swellable material to prevent moisture from adversely affecting the optical fiber, as disclosed in U.S. Pat. No. 5,384,880.
The problem with this arrangement is that with higher and higher buffering process speeds, the gel feeding could become the bottleneck of the process. The higher buffering line speed may induce problems due to the gel not being able to fill the buffer tube, which will result in the formation of air bubbles or voids in the gel thus inhibiting the water block capacity of the gel. Also, an excessively high gel feeding speed imposes high shear stress on the gel which can potentially decompose the gel. In turn, the decomposed gel may yield compound flow failure or water penetration failure issues in the cable. The gel properties effected by the high shear stress can cause process instability and make the overall process of manufacturing the optical cable complex.
More importantly, due to the presence of the water block gel, it is inconvenient and messy to access the fibers in field applications and the exposed gel may also become a source of environmental hazard.
SUMMARY OF THE INVENTION
An object of the present invention is to simplify the overall structure of the optical fiber cable and the associated method of manufacturing the cable and to provide a cable which is more user and environmentally friendly.
According to the present invention, there is provided an optical fiber cable, comprising a plurality of optical fiber groups or sets, each groups including a plurality of optical fibers; a first water swellable material disposed around a first group of optical fibers in a continuous or intermittent manner to hold the fibers together throughout the length of the fibers and a second water swellable material similarly disposed around a second group of optical fibers, wherein the first water swellable material has a color (or other indicia) which is different from a color (or other indicia) of the second water swellable material so as to allow optical fibers of the first group to be distinguished from optical fibers of the second group; and, in some instances a sheath holding the plurality of optical fiber groups together.
The optical fiber cable may further comprise buffer tubes in which the plurality of optical fiber groups or sets are respectively disposed and the buffer tubes are surrounded by the sheath. The optical fibers of the first group have different colors as do the optical fibers of the second group. However, the colors of the optical fibers of the first group are, in some instances, the same as the colors of the optical fibers of the second group. According to the present invention, it is possible to distinguish between optical fibers having the same color by the manner in which the optical fibers are grouped by the colored water swellable material and/or component.
According to another aspect of the invention, the filling gels are replaced with a water swellable material to achieve water block protection of the optical fibers. For example, water swellable material could be used to wrap all the various groups together, and possibly, act as a substitute for the buffer tubes.
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Alcatel
Mack Ricky
Sughrue Mion Zinn Macpeak & Seas, PLLC
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