Implements or apparatus for applying pushing or pulling force – Method or apparatus for placement of conductive wire – By fluid pressure differential in conduit
Patent
1992-03-02
1993-09-28
Watson, Robert C.
Implements or apparatus for applying pushing or pulling force
Method or apparatus for placement of conductive wire
By fluid pressure differential in conduit
B65H 5900
Patent
active
052481280
DESCRIPTION:
BRIEF SUMMARY
This invention relates to the installation of optical fibres.
A standard requirement for the installation of an optical fibre, or bundle of fibres, is that it should be fed into a protective tube or duct which follows the route along which the fibre is to be laid. An optical fibre is delicate and excessive tension induced in it at any stage will impair its operating performance, therefore it is preferred to install optical fibres in ducts by the technique of fibre blowing which utilises viscous drag of a fluid. The fluid, usually compressed gas is blown along the tube and the optical fibre package is urged along by a force distributed over the fibre length. To aid installation the fibre, or a bundle of fibres, may be provided with a lightweight coating such as a foamed plastics material.
The basic fibre blowing method is the subject of our U.S. Pat. Nos. 4,691,896 and 4,948,097, which are herein incorporated by this reference. Developments of the fibre blowing method are described in the following European patent applications: 0287225, 0296860, 0345043, 90303168.0, 88311112.2, 88311113.0, 89304003.0. For the avoidance of doubt, the present invention may be used with any of the fibre blowing variants described or claimed in any of the aforementioned patents or applications.
Such installation methods may be used to install considerable lengths of fibre, so that the point of entry of the fibre into the duct is distant from the point of exit of the fibre at the far end of the duct. It would be of considerable assistance in fibre blowing and other installation processes which involve "pushing" fibres into ducts to have some means at the installation or entry point end of the fibre of knowing when the fibre successfully reaches the far end of the duct and the route is thus completed. This can be done by measuring the length of fibre paid out into the duct if the duct length is known, but this may not always be the case, especially for reinstallation or additional installation, and requires more documentation and information recordal.
The present invention is directed towards providing an installation completion indication that utilises a fibre unit being blown into a tube as a transmission medium to indicate whether or not the unit has completed a given route through the tube.
Accordingly the invention provides a method of determining passage along an installation route of an advancing end of an optical fibre, the method comprising introducing light into the advancing end at a predetermined location on the installation route and monitoring the fibre being installed along the route to detect transmission of the introduced light along the fibre.
The invention also provides apparatus for determining passage along an installation route of an advancing end of an optical fibre, the apparatus comprising means for introducing light into the advancing end of the fibre as it reaches proximity to a predetermined location and means for detecting the introduced light returning along the optical fibre.
The invention will now be described by way of example with reference to the accompanying drawings in which:
FIG. 1 illustrates schematically one embodiment of the invention;
FIG. 3 illustrates schematically a second embodiment of the invention;
FIG. 3 illustrates schematically a variant of the first embodiment of the invention, in which light sources are placed at intermediate points along a route;
FIG. 4 illustrates schematically the interconnection of the remote end detection means with fibre blowing apparatus, and
FIG. 5 illustrates an example of a bead lens suitable for use in the invention.
The embodiment illustrated in FIG. 1 shows a tube 1 through which a fibre unit 2 is being installed, for example by the fibre blowing technique. The fibre unit 2 for example may be a single fibre or a bundle of fibres that may include electrical wires. The fibre unit is installed from end 3 of the tube and is blown through the tube to emerge at the opposite, remote, end 4. A light source 5 is placed at the remote end 4 of the tube. The
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Baxter Peter D.
Freeman Robert A.
Warren John A.
Wills Mark R. J.
British Telecommunications public limited company
Watson Robert C.
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