Optical waveguides – Optical transmission cable – Loose tube type
Reexamination Certificate
1999-09-23
2001-06-05
Spyrou, Cassandra (Department: 2872)
Optical waveguides
Optical transmission cable
Loose tube type
C385S101000, C385S104000, C385S105000, C385S103000, C385S110000, C174S112000
Reexamination Certificate
active
06243519
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical fiber cable laid underground, on the ground, overhead, or undersea and a method of making the same; and, in particular, to an optical fiber cable with jacket in which a plurality of optical fibers are assembled as being S-Z stranded, and a method of making the same.
2, Related Background Art
There has conventionally been known an optical fiber cable with a jacket in which a plurality of optical fibers are assembled as being S-Z stranded about a central member embedding therein a tension member. Such an optical fiber cable is laid underground, on the ground, overhead, or undersea. There are cases where, even after the optical fiber cable is once laid, it is necessary to take out and branch a part of the optical fibers included in the optical fiber cable by removing or ripping a part of the jacket in an intermediate portion of the optical fiber cable (so-called late intermediate branching).
Here, in an optical fiber cable containing therein a plurality of optical fibers extending in their S-Z state, the length of each contained optical fiber would be longer than the length of the optical fiber cable itself (which is identical to the length of-the central member). Therefore, if the jacket is removed from near a reverse portion of the S-Z stranded line formed by an optical fiber (referring to the portion in which the optical fiber reverses from S-strand to Z-strand or vice versa), the optical fiber can smoothly be taken out from the optical fiber cable without being pulled in excess. In view of this point, the workability at the time of branching after laying the cable will improve if the reverse portion of the S-Z stranded line formed by the optical fiber is discernible from the outside of the jacket of the optical fiber cable.
As techniques relating to the above-mentioned matter, those disclosed in U.S. Pat. Nos. 4,828,352 and 5,729,966 have been known. In the conventional optical fiber cables described in these publications, a plurality of optical fibers (optical fibers or optical fiber ribbons) are assembled as being S-Z stranded about a central member. Thus assembled optical fibers are surrounded with a jacket made of a synthetic resin or the like. The jacket is provided with a reverse-portion-indicating mark, such as a symbol, letter, or the like, at the position corresponding to a reverse portion of the S-Z stranded line formed by each optical fiber.
Such an optical fiber cable is made according to the following procedure. Namely, in the case where the steps of stranding optical fibers to forming the jacket are carried out by a single manufacture line, while a core marker apparatus is disposed downstream of a jacket-cooling water bath. Also, a signal indicative of the reversing direction of the lay plate located on the most downstream side among a plurality of lay plates used for stranding the optical fibers about the central member is taken out. When it is determined according to this signal, the feeding length of the central member, and a predetermined offset length that a reverse portion has reached the core marker apparatus, then a reverse-portion-indicating mark is formed on the jacket by the core marker apparatus.
In the case where the step of stranding the optical fibers and the step of forming the jacket are separated from each other, on the other hand, the position of the reverse portion is determined in the step of stranding the optical fibers according to a process similar to that in the above-mentioned case where the optical fiber cable is made by a single manufacture line, and then a color tape, metal tape, or the like indicative of the position of the reverse portion is attached onto a wrapping binder tape wound about the outer periphery of each optical fiber. In the step of forming the jacket, the color tape or the like attached on the wrapping binder tape is detected by a color sensor, metal sensor, or the like before extrusion-molding the jacket, and a reverse-portion-indicating mark is formed on the extrusion-molded jacket according to thus detected signal.
SUMMARY OF THE INVENTION
The optical fiber cable disclosed in the above-mentioned publications is made by attaching a reverse-portion-indicating mark onto an extrusion-molded jacket after detecting the position of a reverse portion according to a color tape or the like attached to a wrapping binder tape for indicating the position of the reverse portion or according to the operation of a lay plate and the like before disposing the jacket around optical fibers. In thus manufactured optical fiber cable, if the reverse-portion-indicating mark were not provided, it would substantially be impossible to find the position of the reverse portion inside the jacket from the outside of the jacket after the jacket is once formed. Also, when making the optical fiber cable, equipment for sticking the color tape or the like is necessary, thus increasing the cost needed for production facilities for the optical fiber cable, thereby raising the cost for making the optical fiber cable.
Further, the reverse-portion-indicating mark attached on the jacket for indicating the position of the reverse portion may disappear after the optical fiber cable is laid. In this case, it is also impossible to detect the position of the reverse portion from the outside of the jacket unless the jacket is removed completely and so forth. As a consequence, in the case where the reverse-portion-indicating mark on the jacket is peeled off, it becomes quite difficult to find the position of the reverse portion inside the jacket from the outside of the jacket, whereby the workability in the branching after laying the cable would deteriorate remarkably.
Therefore, it is an object of the present invention to provide an optical fiber cable in which a reverse portion is discernible from the outside of the jacket, from which optical fibers can be taken out favorably after the cable is laid, and which can be made easily at a low cost, and a method of making the same.
For solving the above-mentioned problems, the optical fiber cable in accordance with the present invention is an optical fiber cable with a jacket in which a plurality of optical fibers are assembled as being S-Z stranded about a central member, the optical fiber cable further comprising a ferromagnetic member disposed near an inner peripheral surface of the jacket along an S-Z stranded line formed by one of the optical fibers.
This optical fiber cable is made by the method of making an optical fiber cable in accordance with the present invention comprising the step of disposing a ferromagnetic member along an S-Z strand formed by one of optical fibers so as to position the ferromagnetic member near an inner peripheral surface of a jacket.
When a plurality of optical fibers are assembled as being S-Z stranded about a central member, the reverse portions of the S-Z stranded line formed by the optical fibers are positioned on the circumference of the same circle about the center axis of the optical fiber cable (“optical fiber” in this specification collectively referring to optical fibers, optical fiber ribbons, stacked optical fiber ribbons, tubes in which contained optical fibers, and the like). In view of this point, in the optical fiber cable and the method of making the same in accordance with the present invention, the ferromagnetic member is disposed along the S-Z stranded lines formed by one of optical fibers. Also, the ferromagnetic member is disposed near the inner peripheral surface of the jacket.
In thus manufactured optical fiber cable, the position of a reverse portion of each optical fiber can be found by detecting a reverse portion of the ferromagnetic member. Specifically, the reverse portion of the ferromagnetic member can be detected easily and reliably from the outside of the jacket by use of a metal sensor or the like. Namely, in accordance with the present invention, an optical fiber cable in which reverse portions of the S-Z stranded line formed by each optical fiber are
Araki Teruo
Haruki Tadaaki
Ishikawa Hiroki
Suetsugu Yoshiyuki
Boutsikaris Leo
McDermott & Will & Emery
Spyrou Cassandra
Sumitomo Electric Industries Ltd.
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