GB2179341A - Method of and apparatus for severing optical fibres - Google Patents

Abstract

A method of simultaneously severing a plurality of optical fibres, more especially in the form of a fibre ribbon, in which the fibres are initially supported across a thin refractory metal wire which is heated by the passage of an electric current to not less than 1000 DEG C, and are then subjected to a tensional force. Such a method produces a substantially clean fracture of all the fibres where contacted by the heated wire.

Description

SPECIFICATION Method of and apparatus for severing optical fibres This invention relates to the severing of optical fibres, and in particularto the severing of a pluralityofpara- Ilel fibres simultaneously. In the case ofso-called fibre ribbons, for example, in which a plurality, for example six, eight or ten, plastic coated silica fibres are secured side-by-side it is necessary in most cases for all the fibres ofthe ribbon to be severed cleanly in the sametransverse plane, to facilitate coupling to thefibres of another ribbon. The failure of only one fibre to sever cleanly thus makes it necessary to carry out a further severing operation, with the resultant wastage of time and of fibres which this entails.

According to the invention a method of severing a plurality of parallel optical fibres comprises supporting the fibres, after removal oftheir plastic coatings, perpendicularly across a refractory metal wire having a diameterwhich is comparable with or its lessthan that of the fibres, heating the wire by the passage of an electric currentto a temperature of not less than 1000 C, and subsequently applying a tension to the fibres sufficient to effect the severing of the fibres.

The metal wire must of course be onewhich can be heated to such a temperature in air, and platinum and iridium are metals which have been found suitable for such a purpose, the wire having a diameterwhich is preferably at least 110 wm. With such materials a wire diameter of between 150to250 m,forexample approximately 200 Fm, has been found particularly suitable, the wire being heated to between 100000 and 1 250"C, for exam ple approximately 1 1 OO"C.

Preferablythefibres are held in a bowed condition across the heated wire for a period sufficient to produce a deformation thereof, for example for between 20 and 30 seconds, and the tension subsequently applied, preferably after raising the fibres from the wire. The heated wire produces imprints in the fibre surfaces, and the non-uniform stress distribution, with a maximum at the region ofthe imprints, as the fibres are subsequently tensioned, has been found to produce a substantially clean fracture at that region.

The length of time the fibres are held in contactwith the wire to effectthe most satisfactory severing will depend, inter alia, upon the diameter of the fibres to be severed, but the conditions giving the most unsatisfactory results in any particular case may readily be ascertained by trial.

The invention also relates to apparatus for use in carrying outthe method above described. According lysuch apparatus comprises meansforsupporting the fibres with any plastic coatings removed perpendicularly and in a bowed condition across a platinum or iridium wire having a diameter of between 110 m and 250 am, meansforconnecting the ends ofthe wire to a source of electric current capable of heating the wire to a temperature of between 100000 and 1250"C, and means for applying tension to the heated wires sufficient to effect the severing theroef.Conve nientlythe meansfor supporting thefibres comprises a pair of clamps disposed one on each side ofthewire and means for lowering and raising at least one ofthe clamps in orderto bring the wires into contactwith and separate them from the wire respectively.

The means for lowering and raising said clamp may comprise at least one rotatable cam, and means are preferably provided for withdrawing at least one of the clamps from the otherforapplying a required tension to the fibres.

One form of apparatus for use in severing the fibres of an optical fibre ribbon, and its method ofuse,will now be described by way of example with reference to Figures 1 to 3 ofthe accompanying drawings, in which Figure 1 represents a sectional elevation of the apparatus, Figure2 represents a plan view, and Figure 3 a transverse section of the apparatus.

The apparatus comprises a metal housing 1 having a base 2 and two upstanding end walls 3,4, and arranged to be fitted with a transparent plastic cover 5 in use.

The housing accommodates within it a support structure 6 secured to the base 2, and this carries a pairof clamps 7 disposed one at each side ofthe central region ofthe housing and arranged to support between them, so that it extends horizontally across the housing, a iridium wire 8 having a diameterof approximately 200,am. The clamps 7 are mutually insulated and in use are arranged to be connected to respective terminals of an electric supply.

At one end ofthesupportstructure6there is mounted a clamp 9 into which is arranged to besecured a length of optical fibre ribbon 11, having the end part stripped of the plastic coating covering the optical fibres 12, a slot 10 in the adjacent end wall 3 providing a passage for the ribbon. The ribbon 11 is positioned so that the exposed ends of the fibres 12, extend overthe iridium wire 8 and into afurther clamp 13 at the opposite end ofthesupportstructure.

The ribbon clamp 9 is pivoted to the support struc- ture 6 about a pair of aligned transverse screws at 14, and its angular position can be varied by means of an outwardly extending lever 20, which projects through a vertical slot in the adjacent side wall 3, a screw 15 providing a stop which limits the downward movementor the clamp. The clamp 13 can also be raised or lowered about a pivot 20 by means of a pair of cams 16 operable by knurled knobs 17 atthe sides ofthe support structure 6, a further screw 18 similarly limit- ing the amount by which the clamp 13 can be lowered. Afurtherscrew 19 extends through a slot 21 in the adjacent end wall 4and terminates in afurther knurled knob 22 which, in use, enables the tension in the optical fibres 12 to be increased as will subsequently be described.

In order to effect a severing operation the ribbon 11 and fibre ends 12 are initially secured by the clamps9 and 13 respectively, and the knob 17 is adjusted to lower the fibre ends so that they extend downwards at an angle of about 2 to 30 to the horizontal,thereby causing the fibres to lie across the iridium wire8 in a bowed condition.

An electric current is then passed through the iri dium wire, sufficientto raise its temperatureto appro- ximately 110000, the fibres being held in contact with the heated wire for about 25 seconds, this being foundto produce a slightimprintinthefibresurfaces.

The clamp 13 is then raised, by means of the knurled knobs 17,to lift the deformed fibres from the wire 8, and tension is applied to the fibres 12 by adjustment of the knob 22, the slot 13.1 which accommodates the pivot 20 allowing the outward movementofthe clamp 13.Then, because of the non-uniform stress distribution, which has a maximum in the region of the imprints, the fibres are caused to fracture cleanly at that region, thereby producing a substantially uniform severing ofthefibres.

Theiridiumwire8ismaintainedunderaslight tension during the heating process to prevent sagging on heating, by mounting each ofthe clamps 7 on an arm 23 which is pivotable about a respectivelongi- tudinal extending pin 24, the ends of a helicalcom- pression spring 25 fitting into recesses 26 in the inner surfaces ofthe arms urging the upper ends apart.

It will be understood, however, that the method in accordance with the invention may also be carried outwith differentform of apparatus from thatde- scribed byway of example. Moreoverthe wire 8, instead of being formed of iridium, may be formed of platinum.

Claims (14)

1. Amethod ofsevering a plurality of parallel optical fibres comprising supporting the fibres, after removal oftheir plastic coatings, perpendicularly across a refractory metal wire having a diameter which is comparable with or is less than that of the fibres, heating the wire by the passage of an electric currentto a temperature of not less than 1 000"C, and subsequently applying a tension to the fibres sufficientto effectthesevering ofthefibres.

2. Amethod ofsevering a plurality of parallel optical fibres according to Claim 1 wherein the metal wire is formed of platinum or iridium.

3. A method according to Claim 2 wherein the wire has a diameter of at least 110 Fm.

4. A method according to Claim 3 wherein the wire has a diameter of between 150 m and 250 iim.

5. A method according to Claim 2,3 or 4wherein the wire has a diameter of approximately 200 am.

6. A method according to any preceding Claim wherein the wire has a diameter of approximately 1100"C.

7. A method according to any preceding Claim wherein the fibres are held in a bowed condition across the heated wirefora period sufficient to pro duce a deformation thereof, and the tension subse quentlyapplied after separation fromthewire.

8. A method according to Claim 7 wherein the fibres are held in a bowed condition across the heated wire for between 20 and 30 seconds.

9. A method of severing a plurality of parallel optical fibres carried out substantially as hereinbefore described with reference to Figures 1 to 3 ofthe accompanying drawings.

10. Apparatus for severing a plurality of parallel optical fibres by a method according to any preceding Claim, comprising meansforsupporting thefibres with any plastic coatings removed perpendicularly and in a bowed condition across a platinum or iridium wire having a diameter of between 150 ism and 250 Fm, means for connecting the ends of the wire to a source of electric current capable of heating the wire to a temperature of between 1000"C and 1 250"C so as to locally heatthe fibres, and means for applying tension to the heatedfibressufficienttoeffectthe severing thereof.

11. Apparatus according to Claim 10 in which the means for supporting the fibres comprises a pair of clamps disposed one on each side of the wire and meansforlowering and raising at least one ofthe clamps in orderto bring the fibres into contact with and separate them from the wire respectively.

12. Apparatus according to Claim 11 wherein the means for lowering and raising the said clamp comprising at least one rotatable cam.

13. Apparatus according to Claim 10, 11 or 12 including means forwithdrawing at least one of the clamps from the other for applying a required tension to the fibres.

14. Apparatus for severing a plurality of parallel optical fibres substantially as shown in and as hereinbefore described with reference to Figures 1 to 3 of the accompanying drawings.