Optical fiber ribbon in which the end fibers are protected...

Details Optical fiber ribbon in which the end fibers are protected... Optical fiber ribbon in which the end fibers are protected...

2000-01-10

2001-12-04

Palmer, Phan T. H. (Department: 2874)

Optical waveguides

Optical transmission cable

Ribbon cable

C385S102000

Reexamination Certificate

active

06327409

ABSTRACT:

BACKGROUND
1. Field of the Invention
The present invention relates to an improved optical fiber ribbon cable in which the stress experienced by fibers located along the outside edge of the cable is minimized to improve the attenuation of those fibers.
2. Related Art
Referring to
FIG. 1
, conventional optical fiber ribbon cables
10
includes one or more optical fiber ribbons
12
each including a plurality of optical fibers (usually twelve)
14
disposed in a plane and encapsulated with a polymer containing an ultraviolet curable resin
16
. Surrounding the optical fiber ribbon(s)
12
is a plastic jacket
18
with an aramid yam
20
, or the like, located in the space
22
between the ribbon
12
and the jacket
18
.
As shown in
FIG. 1
, the space
22
between the optical fiber ribbon
12
and the jacket
18
is substantially uniform around the periphery of the ribbon. The problem with this conventional design is that the optical fibers on the outside edge (“edge fibers”), identified by reference numeral
24
, experience excessive stress during the manufacturing, installation and use of the cable, as compared to the interior fibers, identified by reference numeral
26
. Hence, the attenuation of the edge fibers increases, as compared to the neighboring optical fibers. The stresses are magnified at temperature extremes (e.g., −20 degrees C.).
As noted above, the stress to which the fibers may be subjected is generated during the manufacturing process, the installation of the cable and during the static use of the cable. For example, the step of extruding the outerjacket onto the optical fiber ribbon naturally generates stresses in the optical fibers and particularly on the edge fibers
24
. One reason for this is that when the outer jacket is extruded, coating is applied in a melted state and then cooled resulting in constriction of the fibers, and particularly the edge fibers. In addition, during the handling of the cable, pressure is inevitably applied to the jacket. However, due to the fact that the edge fibers
24
are on the outside edge of the cable, they are generally subjected to greater stress than the interior fibers
26
. When a shock force is applied to the center portion of the cable, it is absorbed by many of the interior fibers such that the pressure (stress) experienced by any one of the interior fibers
26
is relatively small. In contrast, when the same shock is applied to the edge of the cable, a single edge fiber
24
absorbs the shock (i-e., it is not absorbed to by the interior fibers
26
) such that the pressure (stress) experienced by the edge fiber is relatively large. These same considerations come into play during use of the cable when an external force is applied.
Finally, when the cable is subjected to a substantial change in temperature, the expansion and contraction of the jacket can damage the fibers and particularly the edge fibers
24
.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an optical fiber ribbon cable in which the edge fibers do not experience excessive stresses so that the attenuation is within an acceptable range of the neighboring fibers.
This and other objects are achieved by an optical fiber ribbon cable including an optical fiber ribbon having a plurality of optical fibers arranged in parallel including edge fibers respectively located on opposite edges of the ribbon and interior fibers located between the edge fibers; and an optical fiber jacket surrounding the ribbon and defining a first space between the jacket and each of the edge fibers and a second space, contiguous with the first space, between the jacket and the interior fibers. The width of the first space adjacent the edge fibers is greater than a width of the second space adjacent the interior fibers. The cable further includes a strengthening filler disposed in the first and second spaces.
According to the preferred embodiment, the first and second spaces combine to have a dogbone shape. Alternatively, the width of the second space can gradually increase from a center of the optical fiber ribbon toward the opposite edges in a linear or non-linear matter. Further, the cable can include a plurality of ribbons arranged vertically or horizontally.


REFERENCES:
patent: 4715677 (1987-12-01), Saito et al.
patent: 4900126 (1990-02-01), Jackson et al.
patent: 5293443 (1994-03-01), Eoll et al.
patent: 5457762 (1995-10-01), Lochkovic et al.
FOTP-3, Procedure to Measure Temperature Cycling Effects on Optical Fibers, Optical Cable, and Other Passive Fiber Optic Components; EIA/TIA—455-3A, American National Standard, ANSI/EIA-TIA-455-3A-1989, Electronic Industries Association Engineering Department, May 1989.

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