FI83916B - Method for installing an optical fibre network - Google Patents

Abstract

The invention concerns a method and device for installing an optical fibre network. According to the method the conduit 1 for the optical fibres 7 is first installed in position and thereafter the optical fibres are inserted into the conduit by means of a pressure difference created between the ends of the conduit. In known methods the insertion of fibres is difficult and the insertion lengths cannot be made particularly long. According to the invention the problem is solved by the transportation of the fibres 7 being carried out with the aid of a vacuum created at the final end of the conduit and by a spiral-shaped fibre duct 1.1 provided with a secondary casing being used as the conduit. The device according to the invention thus comprises a vacuum container 4 which is connected to the final end of a conduit provided with a spiral-shaped fibre duct 1.1. <IMAGE>

Description

1 83916

Method for installing an optical fiber network

The invention relates to a method for installing an optical fiber-5 reticle. According to the method, the protective structure of the optical fibers is first installed, and then the optical fibers are transferred into the protective structure by means of a pressure difference created by an overpressure generated at the beginning of the protective structure or under-pressure generated at the end of the protective structure. The method according to the invention is intended mainly for short cabling lengths, e.g. for the implementation of telecommunication networks inside or in the area of hotels, commercial properties, factories, apartment buildings, etc. with the help of optical fibers. Because the protective structure is pre-installed before the fibers are installed, the method can not only install a new transmission link, but also add more fibers to an existing transmission link as the need for transmission capacities increases.

It is already known to feed an optical fiber element into its protective structure by means of a pressure difference. For example, EP patent application 186 753 discloses an optical transmission line comprising a shield structure having a plurality of straight fiber channels into which fiber-containing support elements containing optical fibers are fed by means of a supply device located at the beginning of the shield structure. The fiber elements pass through the feed end through a drilled channel inside the protective structure. An inlet nozzle is connected to the duct, through which a gaseous medium, e.g. air, is supplied around the fiber elements. Each fiber element typically comprises a plurality of fibers surrounded by a secondary sheath.

DE patent 33 29 792 also discloses a method in which an optical fiber element is installed in a direct fiber duct inside the cable by means of an air supply device installed at the beginning of the protective structure. The apparatus 2 83916 comprises a housing with a funnel-shaped outlet part inside which a coil of fiber elements is placed. The front end of the protective structure is connected to the outlet of the housing, and compressed air is supplied inside the funnel-shaped outlet part.

5 The fiber element typically consists of optical fibers and a surrounding secondary sheath around which the wires are wound for better air support.

However, the methods described above make it difficult to feed the fibers in, and the thread lengths are not made very large. In particular, the thread lengths of the primary coated fiber alone remain small because the air support provided by these methods is based on the larger bearing surface achieved by the secondary coating of the fibers and any yarns wound around it.

The bends of the protective structure also make it very difficult to feed the fiber support elements.

The object of the present invention is therefore to increase the efficiency of the fiber supply so that the on-problems described above are considerably reduced. This is achieved by the method according to the invention, which is characterized in that a secondary jacket with a helical fiber channel known per se is used as the protective structure.

The basic idea according to the invention is to increase the supply of fibers by combining with a known installation method the advantages offered by a protective structure with a helical fiber channel known per se in such an installation method.

The solution according to the invention makes the threading lengths of the fibers 30 longer and the whole process more tolerant of the bends of the protective structure. The introduction of the fibers is simplified, and the method is also effective in the case of the primary coated fiber alone.

The secondary jacket with a helical fiber-35 channel used in the method is disclosed in Finnish patent application FI-872792. Thus, in a differential pressure installation, such a structure, especially a fiber channel structure with an open center channel, offers clear advantages, which will be described in more detail below.

The invention will now be described in more detail with reference to the examples according to the accompanying drawing, in which Figures 1 and 2 show different alternatives to the protective structure used in the method, and Figure 3 schematically shows an apparatus for carrying out the method according to the invention.

Figures 1 and 2 show cross-sections of two different protective structures that can be used in the method according to the invention. The protective structure 1 consists of a toi-15 sieve jacket tube with fiber channels 1.1 in which the optical fiber, fibers, fiber bundle or bundles are mounted as shown below. In the structure according to Figure 1, each of the three fiber channels has a circular cross-section and is located as a whole outside the longitudinal central axis A of the tube.

The fiber channels are spaced evenly in the circumferential direction of the tube and equidistant from the central axis A. Each fiber channel rotates helically forward in the longitudinal direction of the tube with an equal helical pitch. The twist-25 of the fiber channels 1.1 is shown by broken lines and the direction of rotation by arrow B.

Figure 2 shows a cross-section of a secondary jacket tube with one fiber channel 1.1, which is also circular in cross-section. The inner edge of the fiber channel 30 extends to the opposite side of the central axis A of the tube, whereby in the longitudinal direction of the tube a straight central channel K is formed into a helical fiber channel 1.1. Of course, a protective structure with a helically advancing fiber channel may also have other structural alternatives. However, they are not explained in more detail here, but reference is made to the above-mentioned Finnish patent application FI-872792.

Figure 3 shows schematically an apparatus for carrying out the method according to the invention. Attached to the end end of the protective structure 1 formed by the secondary jacket is a tubular connector 2, to the other end of which a pipe 3 is connected, which leads to the vacuum container 4. The vacuum is generated by means of a vacuum pump 5 through the pipe 6. The connector 2 is preferably transparent to be seen, since the fibers 7 protrude from inside the protective structure 1.

In practice, the protective structure 1 is first installed. This requires that the pipe be boxed from its end points according to needs, i.e. extensions, junctions, terminals and hermetic protections are made to the environment. The boxing is indicated in Fig. 3 by the reference mark R. In addition to the boxing, the protective structure 1 is anchored to the frame and wall elements of the building, e.g. in house installations, so that it corresponds to the stabilization principle of the optical cable. However, since the measures related to the installation of the protective structure 20 are known per se and do not fall within the scope of the actual inventive idea, they will not be described further in this context.

With the protective structure 1 in place, the optical fibers are introduced into the initial end of the protective structure (not shown) and are "sucked" into the protective structure 1 by the vacuum generated by the vacuum pump 5. The fibers are supplied with any lubricating and static control agents. When using a vacuum vessel located at the end of the protective structure, the feeding of the fibers is very simple and no complicated feeding equipment is required at the feeding end. If a lubricant or static control agent is used to feed the fibers, the use of a vacuum also guarantees a clean method, because the the substances are absorbed inside the vacuum container 4. To this end, the vacuum tank 35 is provided with a filter which prevents these substances from entering the vacuum pump 5.

5,83916

The helical fiber channel 1.1 of the protective structure directs the flow of medium provided by the vacuum, typically the air flow, into a vortex space, which detaches the fibers from the friction points formed at the bends of the protective structure 5. As a protective structure, it is advantageous to use the structure according to Fig. 2, in which an open central channel is formed, because this central channel also gives the fibers a direct propagation space. Furthermore, the vortex state of the medium flow caused by the helical space around the central channel and perhaps the partial spiraling of the fibers results in the transmission force caused by the medium flow being applied to the entire length of the fibers and not only to their initial end.

Although the invention has been described above with reference to the example according to the accompanying drawing, it is clear that the invention is not limited thereto, but can be modified in many ways within the scope of the inventive idea set forth in the appended claims. For example, the installation of a protective structure can be done in many different ways, depending on the environment in which it is installed.

Claims (2)

6,83916 A method for installing an optical fiber network, which method comprises first installing a protective structure (1) of optical fibers (7) and then transferring the optical fibers into the protective structure by means of a pressure difference characterized in that 10 secondary sheaths with a helical fiber channel (1.1), known per se, are used as the protective structure. Method according to Claim 1, characterized in that a secondary jacket with an open central channel (K) is used as the protective structure (1). 7 83916