Optical waveguides – Optical transmission cable – Tightly confined
Reexamination Certificate
2003-02-28
2004-08-10
Prasad, Chandrika (Department: 2839)
Optical waveguides
Optical transmission cable
Tightly confined
C385S108000
Reexamination Certificate
active
06775444
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to fiber optic assemblies and methods of making of the same. More specifically, the invention relates to fiber optic assemblies that are manufactured using a single optical fiber strander.
BACKGROUND OF THE INVENTION
FIGS. 1 and 2
illustrate prior art fiber optic cables containing multiple tight-buffered optical fibers.
FIG. 1
depicts a single layer cable
100
that includes multiple tight-buffered optical fibers
101
stranded around a rigid over-coated glass reinforced plastic (GRP) strength member
102
. Strength member
102
serves as an anti-buckling member protecting the tight-buffered optical fibers
101
from buckling loads applied to the cable
100
; however, it makes for a relatively large and stiff cable. As depicted, aramid yarns
103
are stranded around tight-buffered optical fibers
101
. Aramid yarns
103
act as a binder to hold the lay of the optical fibers
101
before extruding jacket
104
thereover. Additionally, aramid yarns
103
inhibit jacket
104
from sticking to the tight-buffered optical fibers
103
, thereby preserving optical performance. Prior art cable
100
also includes a ripcord
105
for removing jacket
104
.
Prior art cable
100
generally performs poorly in crush and bend testing due to rigid central member
102
. During crush testing, optical fibers
101
can be pressed against rigid central member
102
, thereby affecting the optical performance of the same. During bend testing, rigid central member
102
can interfere with the movement of the optical fibers within a bend segment. The tight-buffered fibers at the outer edge of the bend have to travel a longer distance than the fibers on the inner edge of the bend. To compensate for the differential length during bending, the optical fibers are stranded so that they are adjacent to, for example, the outside of the bend radius for a portion of the bend, then move towards the inside of the bend radius for an adjacent portion of the bend. If the bend length is less than the lay length of the optical fibers, the optical fibers may kink causing optical attenuation. For this prior art cable, the fiber optic lay length can effectively limit the minimum bend radius for which acceptable optical performance can be achieved.
FIGS. 2 and 3
respectively depict a prior art dual-layer optical fiber cable
200
and a stranding portion of the manufacturing line therefor. As shown, this prior art cable requires tight-buffered optical fibers
201
stranded in an inner layer and an outer layer, which are separated by a intermediate layer of aramid yarns
203
. Prior art cable
200
also includes a ripcord
206
and a jacket
205
. As shown in
FIG. 3
, the inner layer of optical fibers and the outer layer of optical fibers must be stranded by a first optical fiber strander
301
A, and a second optical fiber strander
301
B. Thus, this dual-layer prior art cable is more complicated to manufacture than prior art cable
100
. However, optical fibers
201
of cable
200
have more freedom to move compared with optical fibers
101
of cable
100
, thereby enabling a smaller bend radius than cable
100
.
Likewise, as depicted in
FIG. 3
, a first and a second yarn strander
302
A,
302
B must also be employed during the manufacture of this prior art dual-layer cable
200
. A significant amount of set-up time is required for manufacturing cable
200
because four separate stranders are required for making the same.
Specifically, prior art cable
200
requires three tight-buffered optical fibers
201
stranded around a central aramid yarn
202
using first optical fiber strander
301
A, thereby forming the inner layer of optical fibers. Next, intermediate layer of aramid yarns
203
is stranded around the inner layer of tight-buffered optical fibers for maintaining the stranding of the same. Intermediate layer of aramid yarns
203
are stranded using first yarn strander
302
A. Thereafter, the outer layer of optical fibers
201
is stranded around intermediate layer of aramid yarns
203
using second optical fiber strander
301
B. Then an outer layer of aramid yarns
204
is stranded around the outer layer of optical fibers
203
using second yarn strander
302
B. Intermediate layer of aramid yarns
203
and outer layer of aramid yarns
204
hold the tight-buffered optical fibers together and maintain the stranded lay of each respective layer. Moreover, intermediate layer of aramid yarns
203
inhibits tight-buffered optical fibers
203
from migrating between layers. In other words, individual optical fibers are generally confined to one layer, which prevents entanglement of optical fibers
201
between layers, which may cause undesirable optical attenuation.
SUMMARY OF THE INVENTION
The present invention is directed to a fiber optic cable including at least one central strength member, a first layer of optical fibers, a second layer of optical fibers, and a jacket surrounding the first and second layers of optical fibers. Where the at least one central strength member essentially lacks anti-buckling strength. Additionally, the fiber optic cable excludes a separation layer between the first layer of optical fibers and the second layer of optical fibers.
The present invention is also directed to a fiber optic cable including a central member, a first plurality of S-Z stranded optical fibers, a second plurality of S-Z stranded optical fibers, and a jacket disposed about the second plurality of S-Z stranded optical fibers. The first and second layers of S-Z stranded optical fiber being disposed in respective radial locations and having lay lengths that are the same. Additionally, the first plurality of S-Z stranded optical fibers are in phase with the second plurality of S-Z stranded optical fibers along the length of the cable because they are both stranded by a common strander.
The present invention is further directed to a fiber optic assembly including a plurality of optical fibers, and a binder layer. The plurality of optical fibers being stranded around in at least two radially distinct adjoining layers. The optical fibers in the adjoining layers having the same lay length and are in phase so that the optical fibers are free to radially migrate between adjoining layers in response to external forces.
Additionally, the present invention is directed to a method of manufacturing an optical fiber assembly including the steps of paying off a plurality of optical fibers, stranding the plurality of optical fibers in a single stranding process, placing a binder layer about the second layer of optical fibers. The plurality of optical fibers forming a first layer and second adjoining layers.
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Carroll. Jr. Michael E.
Corning Cable Systems LLC
Prasad Chandrika
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