Premises optical cable with S-Z stranded strength member

Details Premises optical cable with S-Z stranded strength member Premises optical cable with S-Z stranded strength member

2003-01-06

2004-04-27

Prasad, Chandrika (Department: 2839)

Optical waveguides

Optical transmission cable

Tightly confined

C385S105000

Reexamination Certificate

active

06728454

ABSTRACT:

CLAIM OF PRIORITY
This application claims priority to an application entitled “PREMISES OPTICAL CABLE WITH S-Z STRANDED STRENGTH MEMBER,” filed in the Korean Industrial Property Office on Jan. 24, 2002 and assigned Serial No. 2002-4116, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical-fiber cable and, more particularly, to a premises-fiber optical cable.
2. Description of the Related Art
Premises-fiber optical cables are employed in a network for interconnecting telephone offices to each other and in a network for connecting telephone subscribers to a distribution cable. In general, the diameter of an optical fiber is substantially smaller than that of a conventional telephone cable, but the optical fiber has a wider bandwidth. However, the optical fiber can be easily damaged by a tension stress applied to the optical fiber in the longitudinal direction or by an external impact applied to the optical fiber in the diametric direction.
FIG. 1
is a cross-sectional view of a premises-fiber optical cable having a spirally-stranded strength member, and
FIG. 2
is an exploded side view of the premises optical cable shown in FIG.
1
. As shown, the optical cable comprises twelve tightly-coated optical fibers
110
and
130
, strength members
120
and
140
, a rip cord
150
, and an outer jacket
160
. The twelve tightly-coated optical fibers
110
and
130
include three inner-coated, optical fibers
110
and nine outer-coated optical fibers
130
. The strength members
120
and
140
include an inner-strength member made of an inner yarn
120
and an outer-strength member made of an outer yarn
140
.
Th above structure is disclosed in U.S. Pat. No. 4,781,433, entitled “Optical Fiber Plenum Cable and Method of Making,” in the names of Candido J. Arroyo, et al. Each of the inner and outer-coated optical fibers
110
and
130
comprises a core
132
, a clad
134
, and a tightly-coated layer
136
. An exemplary inner-coated optical fiber
110
having an S-Z type stranded-lay configuration is disclosed in U.S. Pat. No. 4,828,352, entitled “S-Z Stranded Optical Cable,” in the name of Heinrich A. Kraft.
The inner yarn
120
surrounds the circumferences of the three inner-coated, optical fibers
110
and is spirally wound around the central member. The inner yarn
120
maintains a stranding condition of the inner-coated, optical fibers
110
and serves to buffer an external pressure applied to the optical fibers. The inner and outer yarns
120
and
140
may be made of aramid yarn. The nine, outer-coated optical fibers
130
are S-Z type stranded and surround the inner yarn
120
and the inner tightly-coated optical fibers
110
. Similarly, the outer yarn
140
surrounds the circumferences of the nine, outer-coated optical fibers
130
and are spirally stranded. Together with the inner yarn
120
, the outer yarn
140
serves to buffer the external pressure applied to the optical fibers. The outer jacket
160
is disposed at the outermost region of the optical cable and formed by extrusion. The outer jacket
160
may be made of a polymer such as Polyvinyl Chloride. The rip cord
150
is disposed adjacent to the inner wall of the outer jacket
160
to allow a worker to remove the outer jacket
160
easily.
Briefly, a method for manufacturing the conventional premises optical cable is as follows. First, the inner tightly-coated optical fibers
110
are S-Z type stranded. Second, the inner yarn
120
is spirally stranded. Third, the outer tightly-coated optical fibers
130
are S-Z type stranded. Fourth, the outer yarn
140
is spirally stranded. Fifth, the outer jacket
160
is formed by extrusion.
In the aforementioned conventional premises optical cable, the inner-coated optical fibers
110
and the outer-coated optical fibers
130
are S-Z type stranded about the central member, but the inner yarn
120
, interposed between the inner and outer tightly-coated optical fibers
110
and
130
, is spirally stranded. Therefore, in case a pressure from the outside is applied to the premises optical cable, the inner yarn
120
can not buffer the external pressure sufficiently. That is, in the section where the inner yarn
120
is stranded in the same direction of the stranding of the inner and outer-coated optical fibers
110
and
130
, the inner yarn
120
is parallel to the inner and outer coated optical fibers
110
and
130
, thus having a comparatively large area that is capable of buffering the external pressure. However, in the section where the inner yarn
120
is stranded in the opposite direction of the stranding of the inner and outer-coated optical fibers
110
and
130
, the inner yarn
120
is stranded in a crosswise direction to the inner and outer-coated optical fibers
110
and
130
, thereby having a comparatively smaller area capable of buffering the external pressure. Therefore, due to the lack of the uniformity of the buffered area, the inner yarn
120
can not achieve a sufficient buffering function.
SUMMARY OF THE INVENTION
Therefore, the present invention has been made in view of the above problems and provides additional advantages by providing premises-fiber optical cables with an improved buffering function.
In accordance with the present invention, the premises optical cable with a S-Z stranded strength member includes: a plurality of tightly-coated inner optical fibers disposed at the central region of the optical cable and being S-Z type stranded; a plurality of inner yarns S-Z type stranded for surrounding the inner tightly-coated optical fibers; a plurality of tightly-coated outer optical fibers S-Z type stranded for surrounding the circumference of the tightly coated inner optical fibers; a plurality of outer yarns spirally stranded for surrounding the tightly-coated outer optical fibers; and, an outer jacket disposed at the outermost region of the optical cable for surrounding the outer yarns.


REFERENCES:
patent: 6195487 (2001-02-01), Anderson et al.
patent: 6236789 (2001-05-01), Fitz
patent: 6389204 (2002-05-01), Hurley
patent: 6560390 (2003-05-01), Grulick et al.

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