GB2329485A

GB2329485A - Optical waveguide splice protection tube with coloured strength member

Info

Publication number: GB2329485A
Application number: GB9815147A
Authority: GB
Inventors: Wolfgang Beyer
Original assignee: Rehau AG and Co
Current assignee: Rehau Automotive SE and Co KG
Priority date: 1997-09-17
Filing date: 1998-07-13
Publication date: 1999-03-24
Anticipated expiration: 2018-07-13
Also published as: DE29716667U1; GB2329485B; GB9815147D0

Abstract

A splice protection tube for an optical waveguide assembly, said tube comprising a heat shrinkable outer sleeve 1 of transparent plastics material in whose cavity are located a hot-melt adhesive tube 2 into which the waveguide fibre ends (not shown) are inserted, and a strength member 3. The strength member 3 has a coloured surface which is visible through the sleeve 1 and thus enables ready identification of any splice made between fibre ends using the splice protection tube of the invention. Member 3 may be lacquer coated or comprise tinted material.

Description

"SPLICE PROTECTION TUBE" 2329485 This invention relates to a splice

protection tube for an optical waveguide assembly, comprising a heat-shrinkable sleeve with internal hotmelt adhesive layer and a longitudinally extending strength member for increasing mechanical stability under bending load.

Optical waveguide cables are the latest transmission medium and are of paramount importance in telecommunications networks already installed and under construction worldwide. Connections formed between io individual optical waveguides by means of connectors or splices are possible points of failure, which may have a negative effect on the transmission properties of the optical waveguides and must therefore be kept as small as possible.

If incorrectly assembled, such optical waveguide coupling points may cause attenuation of the light signal, wherein part of the optical radiation is not transmitted, the signal light thus being attenuated.

During construction of optical waveguide transmission lines, permanent connections - splices - are necessary, as well as detachable connections. Although the fibres may be drawn to relatively large lengths, the cables are only manufactured in lengths of from 1 to 2 km, for practical reasons. In addition to cable assembly, splice connections are also needed in the case of cable breakage or if the cable route is changed. Such splices are also needed, however, for the insertion into the transmission line of fibre optic components such as connectors and couplers, or to connect short connecting fibres from transmission and receiving elements with connectors pigtails, if the connectors cannot, for example, be directly attached to the connecting fibres.

Splice connection of the individual fibres may be effected using mechanical splicing, for example. The fibres are then clamped in position or fixed there with adhesives.

Such splice connections are generally provided in places where work cannot be carried out with an open flame, e.g. in a potentially explosive environment or if the fibre connection has to be produced without delay. Mechanical splice connections are generally enclosed in a housing, which has an anti-kink action and is thus in practice used as a protective housing for said splice connection.

Current practice in the production of splice connections between individual optical waveguide fibres is to use electric arc welding, however.

This complicated procedure has now become standard practice and is described in detail in the specialist journal "Telekom-Praxis 3191 " under the title "Lichtwellenleiter (LWL) - Verbindungstechniken" ("Optical waveguides io - connection methods"), starting on page 12 and in particular from page 24.

Weld connections welded in this way between individual optical waveguide fibres are completely unprotected after the splicing process. In order to protect the "raw splice" against external environmental influences, metal sleeves, plastics sleeves or heat-shrinkable sleeves are used, for example. Since the invention relates to splice protection by heat shrinkable sleeves, the following explanations are restricted to this technical protection method.

Known heat-shrinkable sleeves generally have a hot-melt adhesive tube, e.g. of ethylene vinyl acetate (EVA), inserted inside them. The raw splice is inserted into this hot-melt adhesive tube. In addition, a metal insert, e.g. a metal bar, is inserted into the cavity of the heat- shrinkable sleeve for mechanical reinforcement, i.e. as anti-kink protection. This technique is described on page 26 of the above-cited publication "Telekom Praxis 3191 ".

The spliced optical waveguide fibres, whose splice points are covered by the splice protection tubes, are as a rule introduced into splice cases. Such splice cases are widely known commercially and are designed to accommodate a plurality of spliced optical waveguide fibres.

For visual identification of the individual optical waveguide fibres and their splices, which are not fully equipped with coloured sheaths, the splice points are colour-coded. This colour-coding is generally achieved by using tinted heat-shrinkable sleeves, the different colours being associated throughout with the different splice points and the connected optical waveguide fibres. In practice, it has proven technically complex and costintensive to produce a heat-shrinkable sleeve to fit every colour used. Although the finished splices may be easily distinguished by the coloured heat-shrinkable sleeves, the splice connection cannot be monitored through the tinted heat-shrinkable sleeve during assembly. Although this monitoring would be possible if transparent plastics materials were used in producing the heat-shrinkable sleeve, colourcoding could not then be io provided for better differentiation between the individual optical waveguide fibres.

This is where the invention comes in, the object of which is to provide a splice protection tube which comprises a clear, transparent heatshrinkable sleeve with integral colour coding, wherein this coding is incorporated without technical difficulty, and thus enables easier assignment of individual splices to splice boxes, splice cases and the like. It is proposed according to the invention that the heat-shrinkable sleeve consists of clear, transparent plastics material and that the strength member be coloured at least on its surface.

The advantage of the invention is that, despite the provision of colourcoding for better differentiation between the individual splices in splice boxes, splice cases or similar closures, monitoring of the splice connection during and after assembly is still possible. Another advantage is the economic production of the colour-coding. For this purpose, the outer circumference of the strength member is lacquer-coated - if a metal pin is used for example. This coat of lacquer may extend over the entire circumference of the strength member, or it is possible, if necessary, to provide only parts of the strength member surface with a coloured coating.

The strength member may, moreover, be tinted throughout - if it is made of a hard plastics material. However, in this instance too, it is possible to provide parts, for example in the form of stripes, of the surface of the strength member with the colour-coding.

The essential advantage of the invention is that a transparent heatshrinkable sleeve may be technically simply and economically colourcoded for use as a distinguishable splice protection tube.

In order that the invention may be better understood, an embodiment thereof will now be described by way of example only and with reference to the accompanying drawings in which:- Figure 1 is a schematic perspective view of a splice protection tube constructed in accordance with the invention; and Figure 2 is an end view of the splice protection tube of Figure 1.

Referring to the drawings, the splice protection tube comprises an outer sleeve, which takes the form of a heat-shrinkable sleeve 1. A hotmelt adhesive tube 2 is inserted into the cavity of the heat-shrinkable sleeve 1. A strength member 3, which according to the invention has a coloured surface, is also located in the cavity of the heat-shrinkable sleeve 1.

The splicing process may be carried out by passing the end of one of the optical waveguide fibres to be connected through the cavity of the hotmelt adhesive tube 2. This end of the inserted optical waveguide fibre 2 is then welded to the end, to be connected, of the next optical waveguide fibre, according to standard practice. The entire assembly comprising heat-shrinkable sleeve 1, hot-melt adhesive tube 2 and strength member 3 is then pushed over the splice point and heated externally, wherein the heat-shrinkable sleeve 1 shrinks over the splice point and at the same time the hot-melt adhesive tube 2 melts through the application of heat and, upon completion of the shrinkage process, fills the remaining cavity of the heat-shrinkable sleeve 1 and thus closes it in such a manner that it is sealed with respect to the outside. The splice point itself is protected thereby from external influences and the colour-coded strength member 3 is visible to the observer from the outside through the transparent wall of the heat-shrinkable sleeve 1, such that assignment of the splice in the splice case may be effected at any time by means of this colour coding.

1. A splice protection tube for an optical waveguide assembly, comprising a heat-shrinkable sleeve with an internal hot-melt adhesive layer and a longitudinally extending strength element for increasing mechanical stability under bending load, characterised in that the heatshrinkable sleeve (1) consists of clear, transparent plastics material and in that the strength member (3) is coloured at least on its surface. 2. A splice protection tube according to claim 1, characterised in that io the supporting member (3) is lacquer-coated for the purpose of colourcoding. 3. A splice protection tube according to claim 1, characterised in that the strength member (3) comprises a tinted material.