FI69216C - FOERFARANDE FOER MONTERING AV EN OPTICAL CABLE SAOSOM LUFTKABEL - Google Patents

Description

6921 6

A method of installing an optical cable as an overhead cable

Recently, there has been an increasing effort to install optical cables as overhead cables. Overhead cables are subjected to significantly higher mechanical stresses than underground cables, and because optical fibers are very susceptible to damage, this has caused problems. In addition, great care is required in the installation of the cable, so that, for example, no pressure must be applied through the suspension members to the channels through which the optical fibers pass.

Generally, a support element separate from the actual cable has been used, most commonly a steel rope, which is first installed in place and then the optical cable is tied to the support element. The latter installation step in particular is laborious and time consuming, and the finished structure has a relatively large dimension in the vertical direction, making it vulnerable to wind.

In order to facilitate the installation work, the so-called

20 octagonal cables, wherein the support element and the optical cable are provided with a pre-common plastic sheath, whereby the support element and the cable itself can be installed simultaneously. The disadvantage of this solution is that the cable is cumbersome to manufacture and the cable 25 becomes very large, which means that it can fit less on the coil and, in addition, the susceptibility to wind has become too great.

A self-supporting structure is also known, in which the channels containing optical fibers form the core of the cable 30, around which a first insulating layer is formed, a tubular structure supporting this, around which an outer insulating layer is further formed. This structure has a more advantageous cross-sectional shape than the first two cable structures, but its manufacture 35 has proved so difficult, in particular due to the tubular support rope, that its use has been limited.

2 69216

The object is to provide a new, more economical method for installing an optical cable as an overhead cable.

The invention thus relates to a method for installing an optical cable as an overhead cable, in which the support element is formed as a core of the cable in the optical cable and a sheath with channels for optical fibers is formed around it.

The method is characterized in that the cable is surface-marked to indicate the passage of the fiber channels and that the cable is attached directly to the suspension members so that they engage the cable at a distance from the fiber channel markings. Thus, when installing the cable, the suspension members are arranged on the basis of the surface markings so that they do not apply pressure to the points where the ducts 15 pass, and alternatively the suspension members can be attached directly to the cable core-forming support element without damaging the fiber ducts.

The various installation methods will be explained in the following in detail by reference to the accompanying drawing.

Figure 1 shows a schematic perspective view of a part of an optical cable.

Figures 2 and 3 show cross-sections of two alternative embodiments.

Figures 4-6 show alternative ways of hanging the cable.

Figure 7 shows an angle suspension in which the cable makes a sharp bend.

Figure 8 shows the extension of the cable.

Fig. 9 schematically shows a cable manufacturing apparatus.

Fig. 10 shows a cross-section of the end of an extruder by means of which a mark indicating the passage of the channels of the optical fibers is provided on the surface of the cable sheath. The optical cable is generally indicated by the reference number 1. It comprises a central support element 3 6921 6, which may preferably be a steel rope or a rope made of Kevlar 49. A protective sheath 3, preferably made of plastic, is formed around the support element 2. and channels 4 for optical fibers are formed in this plastic sheath in a manner known per se. In the example case of the drawing, there are two channels 4, but of course there may be several. On the surface of the jacket 3 there are markings 5 at the channels 4, which indicate the passage of the channels 4. The markings 5 can preferably be color-10 stripes, grooves or protrusions, but of course other ways of marking can also be considered. The channels 4 are arranged with optical fibers 6, which may be one or more in each channel. In addition to the fibers, the channels may have a filling mass. The filling compound can act both as a moisture barrier and as a trainer for fiber vibrations.

Fig. 2 shows the simplest embodiment of a cable with a one-piece sheath 3. The embodiment according to Fig. 3 has a moisture shield 7 arranged around the sheath 3, preferably of aluminum laminate, 20 and an outer sheath layer 8 further formed around this moisture shield.

The channels 4 do not run directly in the jacket 3, but, as can be seen from Figure 1, they are given, for example, a reversible rotation inside the jacket 3. Alternatively, the channels can also be given a normal rotation. However, thanks to the markings 5, the location of the channels 4 along the entire length of the cable can be easily determined, which decisively facilitates the installation of the cable. Thus, as in Fig. 4, the cable can be suspended from its support element 2 between two jaws 9 penetrating through two sheaths 3, which in turn can be fastened to the column by means of fastening rings 10 and a bolt nut fit 11.

Another installation method is shown in Fig. 5. In it, the jaws 12 press the sheath 3 between them at a point where the ducts 4 are not in the immediate vicinity, thus avoiding compression of the ducts 4 4 69216 and consequent damage to the fibers 6. The jaws 12 are attached to the column in a conventional manner by means of fastening rings 13 and a combination of bolts and nuts 14.

In the solution according to Fig. 6, the sheath 5 is peeled so that the channels 4 and the optical fibers therein are not damaged, and a conventional support holder 15 is attached to the support element, which is fixed to the column by means of fastening rings 16.

A steep, almost 90 ° angular suspension can be realized according to Fig. 7 by stripping the cable sheath with a special tool, cutting off the support element 2 and connecting both ends of the support element 2 to the loops 18 attached to the post 17. The fiber ducts 4 remain intact and naturally thick. part of the protective cover 3.

The optical cable according to the invention is also quite easy to extend. Figure 8 shows an example of a dependent splice. The splice is surrounded by an outer sheath 19, inside which splice-20 sleeves 20 are arranged to extend the fibers 6, and inside these splice-sleeve 21 for extending the cable support elements 2.

One method of manufacturing an optical cable according to the invention is outlined in Figures 9 and 10. The support rope 2 and the optical fibers 6 are led from the spool 22 and 25, respectively, from the spools 23 to the extrusion end 26 of the extruder 25, where a cable jacket 3 and channels 4 The finished cable is wound on a spool 24. The press head 26 has an external annular channel 27 from which the plastic mass forming the cable sheath 30 is pressed, and nozzles 28 and 29 for forming the fiber channels 4 and the support member 2, respectively. At the nozzles 28, spikes 30 are formed in the outer circumference of the annular channel 27, which leave grooves in the surface of the cable sheath at the fiber channels 4. The dye 30 35 can be connected to a dye supply or can be replaced

II

6921 With 6 toner feeders. The reversible rotation of the fiber channels can be achieved in a manner known per se, for example as shown in Figure 1 of patent application No. 81 1966.

Claims (4)

6 6921 6 A method of installing an optical cable as an aerial cable, wherein in the optical cable a support element 5 is formed as a cable core (2) and a sheath (3) with channels (4) for optical fibers (6) is formed around it, characterized in that a cable with a surface marking (5) for indicating the passage of the fiber channels and that the cable is fastened directly to the suspension members (9, 12, 15) so that they engage the cable at a distance from the fiber channel markings. Method according to Claim 1, characterized in that the suspension element (12) is adapted to engage directly in the cable sheath (3). Method according to Claim 1, characterized in that the suspension element (9) is arranged to engage the cable support element (2) through the cable sheath (3). A method according to claim 1, characterized in that the cable sheath (3) is peeled without damaging the fiber channels (4) along the length of the suspension member (15) and the suspension member is adapted to grip the cable support element (2). Il