GB2038015A

GB2038015A - Splicing and termination of optical fibres

Info

Publication number: GB2038015A
Application number: GB7849253A
Authority: GB
Original assignee: Standard Telephone and Cables PLC
Current assignee: STC PLC
Priority date: 1978-12-20
Filing date: 1978-12-20
Publication date: 1980-07-16
Also published as: GB2038015B

Abstract

To make a splice between two plastics (e.g. silicone) clad optical fibres, or a termination for one such fibre, the cladding is removed from the end region of the or each fibre and replaced by a sleeve of a heat- shrinkable fluorinated or perfluorinated carbon polymer or copolymer, which is heated to shrink it on to the fibres or the fibre. The material used for the sleeve is so chosen as to have a light-guiding function for light in the fibres; an exemplified material is polyvinylidene fluoride. In the case of the termination the end is polished back so that the end face of the sleeve is flush with the end face of the fibre end. In both cases an outer protective sheath is subsequently applied.

Description

SPECIFICATION Splicing and termination of optical fibres The present invention relates to the splicing together of optical fibres and to the termination of such fibres.

When using plastics clad silica or glass optical fibres some difficulties arise because of the relatively soft nature of the claddings used, these often being silicone resins. Hence an object of the invention is to provide a technique for use in making an optical fibre splice or a termination for a single optical fibre.

According to the invention there is provided a method of making a splice between the ends of two plastics-clad optical fibres, or a termination for a single such fibre, in which the claddings in the regions of the fibre ends in the case of the splice or the cladding in the region of the fibre end in then case of the termination is removed and replaced by a sleeve of a fluorinated or perfluorinated carbon polymer or co-polymer, in which after the replacement the sleeve is subjected to heat to cause it to shrink on to the splice or the termination, and in which the sleeve is of a material such that after it has been shrunk on to the fibres or the fibre it performs a lightguiding function for light negotiating the fibres or the fibre.

According to the invention there is also provided a method of making a splice between the ends of two silicone-clad silica optical fibres, in which the claddings in the regions of the fibre ends to be spliced are removed and replaced by a sleeve of polyvynilidene fluoride, which sleeve causes the splice and the unclad ends of the fibres, in which after the splice has been made and the sleeve has been positioned the sleeve is subjected to heat to cause it to shrink on to the splice, and in which the sleeve thus applied to the splice performs a light-guiding function for light negotiating the fibres.

According to the invention there is further provided a method of making a termination for a silicone-clad silica optical fibre in which the cladding in the region of the fibre end is removed and replaced by a sleeve of polyvynilidene fluoride, in which after the sleeve has been thus applied it is subjected to heat to cause it to shrink on to the termination, in which the end is polished so that the end face of the sleeve and of the fibre end are flush, and in which the sleeve thus applied to the termination performs a light-guiding function for light negotiating the fibre.

In the arrangements to be described herein there are two aspects to consider. One of these is the termination of a single optical fibre while the other is a splice for interconnecting two such fibres in a non-demountable manner.

In the case of the termination, the cladding in the vicinity of the end to be terminated is removed and a sleeve of a heat-shrinkable fluorinate or perfluorinate carbon polymer or co-polymer is applied to the fibre end in place of the removed silicone cladding. This sleeve is then heated to cause it to shrink on to the fibre end so that it is securely attached thereto The material used is so chosen as to have a light-guiding function in respect of its fibre. The sleeve thus attached to the fibre has a length such as to extend beyond the end of the fibre and then is polished back until its end face is flush (or as near flush as is desired) with the fibre end.It should be noted that the reverse can be used, i.e. the fibre end projects from the sleeve and is then polished back, but this is not preferred as care is needed to ensure that the silica is not subjected to flaking.

In the case of the splice, the two fibre ends to be spliced have the silicone cladding removed at their ends, and then a short length of the heat shrinkable sleeve is fitted over the end of one of the fibres to be joined. Next the fibre ends are brought together and joined, e.g. by arc fusion.

Then the sleeve is positioned over the joined fibre ends, and subjected to heat to cause it to shrink on to the joined fibres.

In both the case of the termination and the splice it will be necessary to provide some outer covering. In the case of the termination this may involve securing the termination with its sleeve in place within a ferrule, e.g. by the use of an epoxy or other suitable glue, which could be of the heat curable type. For the splice a convenient outer covering would be a two-part split sleeve which is secured in place over the heat-shrinkable sleeve by some suitable glue or the like.

The arrangements above described have been implemented using a 350 ,um silica optical fibre with a silicone cladding of about 450 yrn. In this case the heat-shrinkable sleeves are of a material marketed under the Registered Trade Mark KYNAR, which is a polyvynilidene fluoride, the inside diameter being such as to be a fairly loose fit over the fibre when its cladding has been removed.

Other materials usable for the heat-shrinkable sleeves include other fluorinated or perfluorinated carbon polymers or co-polymers, and examples are fluorinated ethylene polymers (FEP) or polytetrafluorethylene (PTFE). These latter adhere quite well to glass or silica, but FEP and PTFE do not adhere quite as well to the metal of a ferrule.

However, in such a case the ferrule can be secured 1n some other way, e.g. by crimping, so as to avoid the time penalty incurred when using adhesives.

The fluorinated and perfluorinated polymers and co-polymers (and the term fluorinated as used herein should be interpreted to include perfluorinated) are selected for use in the arrangements described herein because of their low refractive indices, typically from 1.33 to 1.42 and high transparency, with lenses of the order of 5dB/cm. This makes them very suitable for use as a replacement cladding for silica, whose refractive index is about 1.45, especially for short lengths.

They also have high mechanical strength and chemical inertness, and remain stable over a wide temperature range, typically from below -500C to above +2000 C.

Claims

1. A method of making a splice between the ends of two plastics-clad optical fibres, or a termination for a single such fibre, in which the claddings in the regions of the fibre ends in the case of the splice or the cladding in the region of the fibre end in the case of the termination is removed and replaced by a sleeve of a fluorinated or perfluorinated carbon polymer or co-polymer, in which after the replacement the sleeve is subjected to heat to cause it to shrink on to the splice or the termination, and in which the sleeve is of a material such that after it has been shrunk on to the fibres or the fibre it performs a lightguiding function for light negotiating the fibres or the fibre.

2. A method as claimed in claim 1, and in which the fibres or the fibre are silica fibres with silicone claddings.

3. A method as claimed in claim 1 or 2, and.in which the heat shrinkable sleeve is of polyvynilidene fluoride.

4. A method of making a splice between the ends of two silicone-clad silica optical fibres, in which the claddings in the regions of the fibre ends to be spliced are removed and replaced by a sleeve of polyvynilidene fluoride, which sleeve causes the splice and the unclad ends of the fibres, in which after the splice has been made an the sleeve has been positioned the sleeve is subjected to heat to cause it to shrink on to the splice, and in which the sleeve thus applied to the splice performs a light-guiding function for light negotiating the fibres.

5. A method of making a termination for a silicone-clad silica optical fibre in which the cladding in the region of the fibre end is removed and replaced by a sleeve of polyvynilidene fluoride, in which after the sleeve has been thus applied it is subjected to heat to cause it to shrink on to the termination, in which the end is polished so that the end face of the sleeve and af the fibre end are flush, and in which the sleeve thus applied to the termination performs a light-guiding function for light negotiating the fibre.

6. A method of making a splice between two optical fibres, substantially as herein described.

7. An optical fibre splice made by the method of any one of claims 1,2,3,4 or 6.

8. A method of making a termination for an optical fibre, substantially as herein described.

9. An optical fibre termination made by the method of any one of claims 1, 2, 3, 5 or 8.