Optical waveguides – Optical transmission cable – Ribbon cable
Reexamination Certificate
2000-04-06
2002-11-19
Ullah, Akm E. (Department: 2874)
Optical waveguides
Optical transmission cable
Ribbon cable
Reexamination Certificate
active
06483972
ABSTRACT:
BACKGROUND
1. Field of the Invention
The present invention is directed to splittable optical-fiber ribbon products and, more particularly, to optical-fiber ribbon products containing a plurality of sub-unit ribbons that may be separated into fully functional, independent optical-fiber ribbons.
2. Related Art
In the related art, sub-unit ribbons include a plurality of optical fibers encapsulated in a matrix material. A plurality of sub-unit ribbons are then fully encapsulated together to form a splittable optical-fiber ribbon product. Although any number of sub-unit ribbons may be encapsulated together, only two sub-unit ribbons are shown in FIG.
6
. As shown in
FIG. 6
, a first subunit ribbon
10
′ includes a plurality of optical fibers
1
′ which are encapsulated by matrix material
2
′. Similarly, a second sub-unit ribbon
20
′ includes a plurality of optical fibers
1
′ which are encapsulated by matrix material
2
′. The first and second sub-unit ribbons
10
′,
20
′ are then fully encapsulated by encapsulation material
30
′ to form a splittable optical-fiber ribbon product.
A continuing problem in the development of optical-fiber cables is that of providing a high fiber count in a small cable volume in an effort to reduce costs. The related art splittable optical-fiber ribbon product suffers disadvantages in this regard. First, the encapsulation material
30
′ increases the width and thickness of the splittable optical-fiber ribbon product, thereby allowing a limited number of optical fibers
1
′ to occupy a given volume. The width of the splittable optical-fiber ribbon product is the widths w
1
and w
2
of the first and second sub-unit ribbons
10
′ and
20
′, plus twice a hinge thickness th of encapsulation material
30
′, which hinge thickness th exists on each side. Therefore, the width of the splittable optical-fiber ribbon product is increased by at least twice the hinge thickness t
h
over the width of an optical-fiber ribbon made without sub-units and having the same number of fibers as the two subunits
10
′ and
20
′ together. Similarly, the encapsulation material
30
′ is present on the top and bottom of the sub-unit ribbons
10
′,
20
′ as an overcoat having thickness t
o
. Therefore, the thickness of the splittable optical-fiber ribbon product is thicker than either sub-unit by an amount that is twice the overcoat thickness t
o
.
Further, the individual sub-units may be thicker and wider after being separated or split from the splittable ribbon than before they were joined together. Therefore, the remaining matrix material on the separated sub-units must be removed, which causes additional time delays when it is desired to use the sub-units as individual ribbons, as in connectors and other equipment, for example, after they are separated from the splittable optical-fiber ribbon product.
This increased width and thickness results in a lower packing density, i.e., a smaller fiber count within a particular volume for the splittable optical-fiber ribbon product as well as for the individual sub-units after they are split from the ribbon product.
In order to increase packing density, one related art solution involves using the encapsulation material to provide hinge coverage in the splittable optical-fiber ribbon product. That is, in this type of related art product, the individual sub-units do not have a matrix material which completely encapsulates the optical fibers. Instead, the optical-fibers are completely encapsulated only after the encapsulation material is applied. This arrangement thus attempts to increase packing density by eliminating the sub-units' hinge thicknesses. When the sub-units are split, however, there is a distinct danger of having one of the fibers on either end of the sub-unit break out of the sub-unit package. This danger is especially acute on the end of the sub-unit that was previously adhered to another sub-unit because the sub-unit hinge is too thin to have the strength necessary to withstand the forces involved in the process of fracturing the encapsulation material that binds it to the adjacent sub-unit.
Another problem related to fully encapsulating the sub-unit ribbons is high cost in both materials and production of splittable optical-fiber ribbon products. That is, the encapsulation material
30
′ can be quite expensive and, therefore, the more that is used, the more expensive the end product becomes. Further, the encapsulation material is typically cured using ultra-violet (UV) or other radiation. And the amount of energy required to cure the encapsulation material
30
′ is proportional to the amount of material used.
Yet another problem in the optical-fiber industry is that of easily and quickly accessing the optical fibers within a splittable optical-fiber ribbon product. That is, for installation, service and maintenance purposes, it often becomes necessary to perform splicing and termination operations on individual optical-fibers within a splittable optical-fiber ribbon product. In order to access the individual optical-fibers, a peeling process is typically used. The peeling process must leave the optical fibers with their individual coatings—including color coatings—intact, yet peel away all of the sub-unit's matrix material that binds them together. The sub-units of splittable ribbon products are easily split away from the combined optical-fiber ribbon product to facilitate access in the field. However, difficulty arises in that both an encapsulation material and a sub-unit matrix material must then be peeled off in order to access individual fibers. This situation will be described with reference to
FIGS. 7 and 8
.
FIG. 7
shows a first sub-unit ribbon
10
′ after it has been split apart from the combined optical-fiber ribbon product shown in FIG.
6
. As shown in
FIG. 7
, the sub-unit
10
′ and the optical fibers
1
′ are still encapsulated within encapsulation material
30
′ as well as within matrix material
2
′. Therefore, a two-step peeling process often must be performed to access the optical fibers
1
′. That is, a first peeling process performed on the split-off sub-unit
10
′ shown in
FIG. 7
typically results only in removal of the encapsulation material
30
′ leaving the sub-unit
10
′ as shown in
FIG. 8. A
second peeling process must then be performed on the split-off sub-unit
10
′ as shown in
FIG. 8
to remove the matrix material
2
′ so that the optical-fibers
1
′ can be accessed.
Performing two peeling processes to access the optical fibers
1
′ adds to installation time for workers in the field who are using such ribbons. When applied to high fiber-count installations, this added installation time can become quite sizable.
SUMMARY OF THE INVENTION
It is an object of the present invention to overcome the drawbacks of the related art. More particularly, it is an object of the present invention to provide a lower cost splittable optical-fiber ribbon product than that available in the related art, and one which also reduces external dimensions in order to increase its packing density, i.e., the space required to pack a stack of ribbons in a cable or tube. Reducing external dimensions reduces cost and increases packing density, thereby allowing a high fiber count to be provided in a small cable volume.
It is another object of the present invention to reduce the risk of fiber breakout in splittable optical-fiber ribbon products.
It is a further object of the invention to provide a splittable optical-fiber ribbon product in which individual optical fibers can be accessed easily and quickly. More particularly, it is an object of the present invention to provide a splittable optical-fiber ribbon product whose optical fibers can be accessed with only one peeling process, thereby reducing installation time in the field.
The present invention achieves the above and other objects and advantages
Paschal Kevin Scott
Thompson Justin
Alcatel
Rahll Jerry T.
Sughrue & Mion, PLLC
Ullah Akm E.
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