Optical waveguides – Optical transmission cable – Ribbon cable
Reexamination Certificate
1999-09-29
2002-01-08
Mai, Huy (Department: 2873)
Optical waveguides
Optical transmission cable
Ribbon cable
C385S100000, C385S128000
Reexamination Certificate
active
06337941
ABSTRACT:
BACKGROUND
1. Field of the Invention
The present invention relates to splittable optical fiber ribbons and, in particular, optical fiber ribbons for telecommunications cables. More particularly, the present invention is directed to the interface between adjacent sub-unit ribbons within splittable double-embedded optical fiber ribbons.
2. Related Art
Related-art double-embedded optical fiber ribbons are designed with sub-unit having rounded edges. Each sub-unit is formed of a plurality of optical fibers disposed in a plane and encapsulated with a polymer thereby forming the sub-unit. Each sub-unit includes rounded edges, which are placed adjacent one another, when the sub-units are arranged side-by-side so that the optical fibers of all the sub-units lie substantially in a plane. The sub-units are then encapsulated by a second polymer coat to form one optical fiber ribbon therefrom.
A related-art sub-unit design, and ribbon made therefrom, are shown in
FIG. 1. A
first sub-unit
1
′ includes optical fibers
3
′ encapsulated within a matrix material
4
′. Similarly, a second sub-unit
2
′ includes optical fibers
3
′ encapsulated within a matrix material
4
′. Both of the first and second sub-units
1
′ and
2
′ have rounded edges.
In the related-art design, however, alignment of the sub-units so that all the optical fibers remain in a plane as the second polymer coat cures is a problem, i.e., planarity of the ribbon formed by the sub-units is poor. The sub-units
1
′ and
2
′ include rounded edges that contact one another generally at a point
6
′, i.e., as two half circles would contact. Because of the point contact, the sub-units
1
′ and
2
′ tend to rotate relative to one another about the contact point which thereby causes poor ribbon planarity. Yet good ribbon planarity is an important ribbon property. Ribbon planarity is a measure of optical fiber alignment in a ribbon and is a measure of ribbon quality. The ribbon planarity plays an important part in fusion and mechanical multi-fiber splicing, as well as in termination in the field. Ribbon planarity is measured according to industry standards wherein a planarity of zero indicates that all fibers in the ribbon lie in the same plane. Therefore, it is desirable to achieve a ribbon planarity which is as low as possible.
FIG. 1
shows a ribbon having poor—i.e., high—planarity. The rotation of the two sub-unit ribbons is due, at least in part, to the surface tension effects occurring in the second matrix material as it is cured between or among sub-unit ribbons during the curing process. In addition, rotation of the sub-unit ribbons may be due to the fact that different ribbon sub-units may be under different pay-off and take-up tensions during the ribbonizing process. Thirdly, the sub-unit ribbons may have electrostatic forces and may be under vibration during ribbon processing due to the instability of the equipment. These factors may lead to—due to the point-contact between sub- units—a higher or inconsistent ribbon planarity. For instance, the planarity may be greater than 50 &mgr;m, which is too large for certain specifications—US GR-20-CORE, issue 2, Italy's Telecom Italia, and Swedish Telia, for example—depending on the fiber count in the ribbon.
The ribbon sub-units include a minimum of two fibers and can include up to 12-fibers per sub-unit. A ribbon includes of a minimum of two ribbon sub-units and each sub-unit may include a different number of optical fibers. For example, a ribbon may have three sub-units , wherein each sub-unit may include either 2, or 4, or 6, or 8, or 12, or any other number of, optical fibers.
SUMMARY OF THE INVENTION
An object of the present invention is to overcome the problems of the related art. A further object of the present invention is to alleviate, or at the very least, minimize the related-art problem of poor—i.e., high—planarity in double-embedded optical fiber ribbons formed from sub-unit ribbons.
Planarity in a double-embedded optical fiber ribbon is improved—i.e., lowered—in the present invention, by enhancing the stability of the interface between the sub-unit ribbons from which the double-embedded optical fiber ribbon is made. The present invention enhances interface stability by shaping the sub-unit-ribbon edges so as to create an interlocking effect and a greater contact area between the sub-units. The interlocking effect and greater contact area reduce sub-unit-ribbon interfacial micro-movement during formation of the double-embedded optical fiber ribbon.
Interface stability may be enhanced by making the sub-unit ribbon edges of a complementary shape so as to create an interlocking effect. For example, the edges may be complimentarily shaped by inclusion of a non-circular surface on one edge of each sub-unit. The non-circular surfaces, when adjacent one another, reduce rotation or rolling motion of the sub-units about the interface, i.e., the non-circular surfaces tend to interlock the sub-unit ribbons. The edges of the sub-units, opposite those edges which include a non-circular surface, may be either rounded or may also include a non-circular surface.
A sub-unit ribbon wherein both edges include a non-circular surface is advantageous when producing a double-embedded optical fiber ribbon of more than two sub-units. That is, the double-embedded optical fiber ribbon may be made of any number of sub-units so that it includes the desired number of optical fibers. A sub-unit having only one edge that includes a non-circular surface is advantageously disposed on the edges of the double-embedded optical fiber ribbon. That is, a sub-unit having one rounded edge and one edge that includes a non-circular surface can be arranged so that its rounded edge is disposed toward the outer edge of the double-embedded optical fiber, whereas the edge having a non-circular surface is disposed adjacent another sub-unit's non-circular surface.
The non-circular surfaces may be included in variously shaped sub-unit edges, all of which enhance the stability of the interface between the sub-units by resisting relative rotation. The non-circular surfaces may be substantially perpendicular to the plane in which the sub-unit's optical fibers lie. Alternatively, the non-circular surface may be oblique to the plane in which the sub-unit's optical fibers lie. Further still, the non-circular surfaces may include protrusions extending therefrom. Not only do sub-units that have a non-circular surface on their edges enhance resistance to rotation, they are also complementarily shaped so as to provide an increased contact area between the sub-unit edges.
Instead of having edges with circular surfaces that point-contact one another, the stability of the interface between sub-units can be increased using rounded edges that have an increased contact area therebetween. That is, one sub-unit may have an edge with a concave circular surface, whereas an adjacent sub-unit may then have a convex circular surface which fits within the concave circular surface. Thus, instead of contacting at a point as do the circular or rounded edges in the related art, the circular or rounded edges of the present invention sub-units contact one another over a large portion of their complementarily rounded edges.
With each of the edge configurations of the present invention, the sub-units may be separated by the second matrix material, or may directly abut one another.
Not only do the above mentioned edge shapes provide an interlocking effect, they also provide a greater contact area between the sub-units, thereby further enhancing stability of the sub-unit interface. When the sub-units are separated by the second matrix material, a greater opposing surface area for limiting sub-unit rotation is achieved by the above-mentioned edge shapes. Further, when the sub-units are directly abutted, without any of the second matrix material therebetween, they are even less likely to rotate relative to one another.
Further, when there is no second poly
Thompson Justin
Yang Houching Michael
Alcatel
Mai Huy
LandOfFree
Splittable optical fiber ribbons does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Splittable optical fiber ribbons, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Splittable optical fiber ribbons will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2818877