Optical waveguides – Optical transmission cable – Loose tube type
Reexamination Certificate
2002-03-27
2004-03-09
Zarroli, Michael C. (Department: 2839)
Optical waveguides
Optical transmission cable
Loose tube type
C385S111000, C385S114000
Reexamination Certificate
active
06704482
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical cable, which is formed by laminating together a plurality of optical fiber tape cores, in which multiple optical fiber cores are arrayed in the form of a tape, and housing this laminate inside a sheath; a device for manufacturing this optical cable; and an optical cable production method which employs this manufacturing device.
2. Background Art
Optical cables in which an optical tape core laminate, obtained by arraying multiple optical fiber cores in the form of a tape and laminating a plurality of these optical fiber tape cores together, is housed inside a pipe-shaped sheath, have been disclosed in (1) U.S. Pat. No. 4,744,631, (2) U.S. Pat. No. 5,621,842, and (3) U.S. Pat. No. 6,122,424.
The sheath in these optical cables has been filled with a jelly-like water-repelling blended material or a filling material having elastic properties. An optical cable has also been disclosed in (4) EP 1,085,359A2 in which an optical tape core laminate, that is protected by a protective tape, is covered by a sheath.
In addition, optical cables have been disclosed in (5) Japanese Patent Application, First Publication No. 3-172808, (6) Japanese Patent Application, First Publication No. 4-143710, and (7) Japanese Patent Application, First Publication No. 8-240752, which employ a spacer in which at least one or more spiral grooves (referred to as “slots” hereinafter) are formed in the surface of a long cylindrical rod consisting of a plastic material, and the optical tape core laminate is housed inside this slot. Further, (8) Japanese Patent Application, First Publication No. 2-83507 discloses an optical cable in which an optical fiber tape core laminate is housed inside spiral grooves in a spacer in which the spiral grooves reverse directions alternating from the left to the right, i.e., alternately reverse in the SZ directions, at a fixed cycle on the surface of a cylindrically shaped rod. (9) Japanese Patent Application, First Publication No. 4-182611 discloses an optical cable in which a plurality of optical fiber tape cores are laminated inside a pliable housing member (uni-slot tube) which is shaped in the form of the letter “U” in cross-section, and this pliable housing member is twisted in the SZ directions around a tension member.
However, the optical cables disclosed in patent applications (1)~(3) above employ a relatively large amount of filling material to fill the sheath, so that a spacer for this filling material is needed. Thus, a thicker cable diameter and a heavier cable weight result.
The optical cable disclosed in patent application (4) requires the step of wrapping protective tape around the optical tape core laminate, while the optical cables disclosed in patent applications (5) through (9) require the step of forming the slot in the surface of the cylindrical rod. As a result, a greater number of manufacturing steps are required to produce the optical cable, and there are also disadvantages in terms of costs. Moreover, in the optical cables disclosed in patent applications (5) through (9), distortion in the optical fiber core increases when the optical fiber tape core is mounted inside the slot, so that a cable with excellent properties is not obtained.
In addition, given the size of the distortion that occurs in an optical fiber core housed inside spiral grooves formed in a spacer which reverse from the S direction to the Z direction, and from the Z direction to the S direction, when the optical cable housing this optical fiber core is bent, (10) Japanese Patent Application, (Granted) Publication No. 7-13687 suggests that it is preferable that the track of the spiral grooves be in the form of a sine wave, and the angle of reversing be in the range of 230° to 330°, i.e., the spiral grooves reverse at every 230° to 330° rotation, with 275° providing the smallest distortion in the optical fiber core.
However, to form a spiral groove of this shape requires highly controlled techniques. Moreover, the technique disclosed in (10) is directed to optical cables in which the number of optical fiber cores is in the range of 3000~4000, or more.
On the other hand, an optical cable having a structure like that shown in
FIG. 15
has been proposed recently.
In
FIG. 15
, numeral
1
indicates an optical tape core laminate in which multiple layers of optical fiber tape cores have been laminated together. This optical tape core laminate
1
is not fixed completely in place inside a forming pipe
2
, but rather is housed with an interval of spacing between itself and the forming pipe
2
. This forming pipe
2
is formed into the shape of a pipe by employing a pipe-forming method in which tape, consisting of a rigid plastic film like polyester, polypropylene, polyethylene, polyamide, or fiber reinforced plastic (FRP), is continuously fashioned into the shape of a pipe. The seams running along the longitudinal direction of this forming pipe
2
are then joined together by meaning of adhesive tape
3
.
The Forming pipe
2
is covered with a sheath
4
consisting of polyethylene or plasticizing polyvinyl chloride or the like. The formation of the sheath
4
is carried out using the usual extruding and cladding method.
Two tension members
5
, consisting of fiber-reinforced plastic or steel, brass or other such metal wire, and two rip cords
6
, consisting of plastic cords, are embedded in the sheath
4
. The tension members
5
are disposed opposite one another with the optical tape core laminate
1
interposed between them. The rip cords
6
are disposed opposite one another with the optical tape core laminate
1
interposed between them, and so as to be perpendicular to a line joining the two tension members
5
.
In order to support and house the optical tape core laminate
1
within the forming pipe
2
without completely fixing it in place inside the pipe
2
, an intermittent filling material (not shown) consisting of a soft hot-melt adhesive is employed to fill the optical cable at intermittent points along its length.
When subsequently splitting an optical cable of this design, the sheath
4
is cut open by pulling the both rip cords
6
, thereby dividing the optical cable into two parts. However, it can be difficult to split the forming pipe
2
due to its high resistance to tearing, or because it adheres to the sheath
4
, for example. Thus, it can take some time to expose the optical tape core laminate
1
inside. In other words, this optical cable does not always demonstrate excellent properties with respect to subsequent splitting.
SUMMARY OF THE INVENTION
The present invention was designed to resolve the problems described above, and has as its objective to provide an optical cable employing optical fiber tape cores which does not need a large amount of filling material or a long cylindrical spacer in which spiral grooves are formed. Furthermore, it is the objective of the present invention to provide an optical cable with relatively few cores which has excellent cable properties even when the optical tape core laminates are twisted in an SZ arrangement and the optical cable is bent. In addition, it is the objective of the present invention to simply and efficiently provide an optical cable which is superior with respect to ease of subsequent splitting of the cable.
An optical cable according to the present invention is provided with optical fibers, a forming pipe for housing the optical fibers, a sheath provided around the forming pipe, a pair of tension members embedded in the sheath, and a pair of rip cords similarly embedded inside the sheath, and is further characterized as follows. Namely, this forming pipe is fashioned using a plurality of tapes in such a way as to be divisible along its longitudinal direction. The rip cords are provided near the seams of this forming pipe, and the distance from the surface of the tension members to the sheath's inner surface and to the sheath's outer surface are both 0.3 mm or more. The distance from the center of the rip cords to the
Hashimoto Yoshio
Miyamoto Matsuhiro
Okada Naoki
Satoh Yoshiyasu
Suematsu Michio
Darby & Darby
Fujikura Ltd.
Zarroli Michael C.
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