CA1303888C - Optical fibre breakout - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A technique for protecting an optical fibre breakout particularly from a cable comprising a core, a plurality of loose fibres and a jacket. The jacket and core are stripped back and the fibres encased in protective tubes. This may be done one fibre at a time by removing a portion of cable jacket remote from the end and withdrawing each fibre from under the remaining end portion of jacket. The cable may be held in a holding tool and the fibres inserted into their protective tubes by means of an insertion tool.

Description

~ 3~3~31!3~3 This invention relates to a technique for protecting a braakout from an optical fibre cable, particularly one in which a plurality of bare optical ibres is mounted directly onto a grooved core.

Thi~ application is a divisional application of copending application No. 580~393, filed October 10, 1988, which i5 a divisional application of application No. 470,436, filed December 18, 1984, now Canadian patent 1,265,944, is~ued February 20, 1990.
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Although the in~ention is applicable to break-outs from a variety o~ multifilament cables it will be described principally in terms of the following system where the greatest advantages are expected: a plurality of optical fibres ~generally five, or multiples of five, and particularly ten for a distribution cable) are mounted on a core which has longitudinal grooves therein which generally run in a shallow helical path around the core. Each of these grooves carries one (or more) optical fibres. The core, which is generally known, and will be referred to herein by the French word "jonc"
usually comprises a polymeric material reinforced with a central wire reinforcement to pre~ent the cable being sent through a radius of curvature that would damage the optical fibres. Incidentally, the reason for the fibres following a helical, rather than a straight path along the jonc is to make the cable more tolerant of being bent. The jonc and fibres are then provided with an outer jacket comprising, for example, one or more helical wraps of a polyethylene tape.

A problem arises when two such cables are to be spliced or when such a single cable is to be terminated by connecting it, for example, to a distribution frame for connection to larger feeder cables fro~ the transmitterj or to drop terminal for connection to smaller drop cables to the consumersO The problem is ~: ;

13~13~3i!!~ii how t~ turn au en-1 portion o~ a sinyle multi-fibre cable !often as ITlUCh as 2m) into a plurality of free individually protected optical ibres. This change is kl1own as break-o-lt.

O11e aspec~ oE the proble1n is adc1ressed in European patent rublication 0063506. 11ere, the ten optical fib1:es are removed from the jonc back to a certain pOsitioll. The exposed portion of the jonc i5 then cut o~f. A sleeve (known as a a barrel) i~ then provided in the fornl oE a hollow cylinder having one closed end, which end is perforated by ten holes, from each of which extends a protective tube. The optical ~ibres are then inserted into the open end o the cylinder and then through respective holes and protective tubes. Once all ten Eibres are inserted in this way, the barrel is slid home towards the cable so that the new end o~ the cable proper lies witt1in the cylinder.

A modification of this idea is also disclosed in European patent publication 0063506. In this disclosure, the hollow cylinder or barrel has ten ribs running longitudinally along its inner surface. Each rib has a hole therein which communicates with the holes and protective tubes of the closed face. Each rib, when the sleeve or barrel is installed, lies within a groove Oe the jonc. This provides better protection for the optical fibres, and in particular prevents the barrel rotating with respect to the jonc.

Published European patent application No. 0092441 discloses a modified sleeve or barrel which abuts against an end of the jonc rather than receiving the whole jonc within it and which has a series of open channels along its outer surface into which the protective ~ tubes may be snap fitted.
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A slightly different way of installing such a device has also heen proposed. A spreader barrel is provided which is frusto conical and which has ten channels along its tapered surface. ~ portion of the jacket of the optical ~ibre cable is remo~ed, and the spreader barrel of~ered-up to the end of the jonc so that the fibres on the jonc enter the channels on the barrel and from there enter the protective tubes associated therewith. The barrel is then advanced up the jonc in stages until a sufficient length of free individually protected fibres has been providedO The exposed length of jonc is then cut-off.

In each of these techniques some form of protective sheath may be provided around the cable at the point where the fibres enter the protective tubes. This secures the protective tubes and prevents the optical fibres bending too sharply at that point.
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It can be seen from the above revlew, which is believed to summarize developments to date in this field, that considerable technical effort has been expended in protecting the fibres at the vulnerable region where they leave the jonc. The installed products have, in general, been acceptable: for example, fibre microbends can be avoided, strain relief to the protective tubes can be provided whilst leaving the fibres themselves free to move, and environmental sealing can be maintained under test conditions.

Unfortunately, installation of the products described can be unacc~ptably craft-sensitive under field conditions:
the fibre damage that one hopes to avoid by using these prDducts is likely to occur during their inætallation. For example, an attempt to advance a spreader barrel clamping all ten fibres can cause the fibres to break or to bend su~h that their attenuation is permanently increased. Alternatively, the presence X

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of up to, say, 2m length of ten free fibres before insertion into their protective tubes is likely to result in considerable fibre damage. This may also cause repeated confusion to the installer who must, for example, match colour coding of the protective tubes to fibre position on the jonc. Furthermore, considerable difficulty may be experienced in feeding the fibres into their protective tubes.

We have discovered that installation can be simplified and made more reliable.

Thus, the invention provid~s as disclosed and claimed in Canadian patent 1,265,944 a method o~
terminating a cable comprising a plurality of optical fibres surrounded by a cable jacket, in which: (a) a length of cable jacket is removed from a portion on the cable, leaving in place a further length o~ jacket nearer to the end to be terminated; (b) the fibres are withdrawn from under said further length of jacket such that they leave the cable at said portion; (c) the fibres thus withdrawn are inserted into individual protectiYe tubes;
and (d) the further length of jacket is removed.

The invention also provides as disclosed and claimed in copending application 580,393 a kit-of-parts suitable for terminating an optical fibre cable, which comprises:
a plurality of protective tubes each suitable for housing individual optical fibres; ~ heat-shrinkable sleeve suitable for securing the tubes with respect to the terminated cable; means for indentifying respective protective tubes; and means for correlating the identification of the tubes with respective fibres of the cable.

The invention further provides as disclosed and claimed in Canadian patent 1,26~,944 ~ ~ethod of terminating a cable comprising a plurality of optical ~30388 !3 fibres surrounded by a cable jacket, in which: (a~ a length of cable jacket is removed from a portion of the cable, exposing a plurality of optical fibres; (b) the fibres are inserted into individual protective tubes; and ~c) an environmental seal is provided at either or both end portions of a protective tube by means of a gel which prevents contaminants passing along a fibre.

In a further aspect, the invention provides and claims in this application and insertion tool for inserting an optical fibre into a protective tube, which comprises: guide means for accepting an end of the fibre; means for locating the fibre; means for locating the tube, the means for locating the fibre and the mans for locating the tube being such that end portions of the fibre and tube have substantially the same axis; and mean~ for advancing the fibre and/or the tube along said axis without damaging the fibre.

The present application also provides and claims a method of using the above described tool to protect an optical fibre.

In a still further aspect, the invention provides a holding tool for holding an optical fibre cable during termination thereof, which comprises: first and second portions of the cable such that a third portion, between said first and second portions, is accessible for removal therefrom of a jacket of the cable to the expose fibres of the cable and/or for removal therefrom of fibres of the cable; and ~L3~3i3~

means for rotation of the cable about its longitudinal axis.

Each of the above tools may be provided with ~either as a separate article or as markings thereon~ means for correlating the identification of the tubes with respective fibres as mentioned above in connection with the kit of parts.

With regard to the insertion tool, the ~eans for locating the tube and tha fibre may be grooves or holes in the tool, and the guide means may be a tapered end portion of one of those grooves or holes. The advancing means preferably comprises one or more rollers (by which term we do not intend to be limited by any relative width and diameter) against which the tube or fibre bears. A pair of rollers may of course be provided, between which the tube or ~ibre passes. We prefer that the tube be held and the ~ibre be driven into the tu~e since this allows an infinite length ~f -fibre~ to be lnserted whilst employing a simple de~i~e for holding the tube. The tool may be designed to deal with one tube and fibre, or with several substantially simultaneously.
The advancing means may be driven by hand, but we pr~fer that an electric or other motor be employed. We prefer that the advancing means be capable of advancing the fibre and/or tube in each of two mutually opposite directions. ~his is particularly useful where the fibres to be protected by the tubes are ~rom two cables to be spliced as an in-line splice.
The reaso~ i5 simply that the free ends of the fibres from one cable will face the oppo~ite direction to those rom the other cable and it may be inconvenient to rotate the installation tool to deal with the different directions in which the two sets of tubes must be fed. The groove or hole of the tool within which the tube is held will preferably be ~r L~

~L3~333~3 of greater diameter than the groove or hole where the fibre is held, due to the greater diametPr of the tube. In such a case, the tube will be held fixed and the fibre will be advanced into it.

The kit comprising the protective tubes may be supplied with various means for ordering or distinguishing the protectivs tubes, for example an organizer to which the tube may be attached by for example pressure-sensitive adhesive patches, flaps stamped out of the material of the board having slots therein, and discrete hooks or clamps attached to the organizer. In general, any means for affixing may be provided that allows each tube to be identified and that allows the tube to be removed, preferably by simple lateral movemQnt away from the organizer rather than by, for example, longitudinal withdrawl through a hole closed in cross-section.
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Instead of one organizer being provided, on`which all of the protective tubes are organized, two or more organizers may be provided on each of which is located one or more tubes. This arrangement may be preferred, when the optical fibre cable is to be terminated for the purpose of making a splice to another cable. The reason for this is as follows;
splices between optical fibre cables involve the use of a splice organizer which generally comprises a series of plates on each of which lies one or more splice~ and several turns o~ fibre either side of the splice or splices. The purpose of the spare turns o~ fibre is to allow the splice to be made in a machine some short distance from the splice organizer.
It can now be seen that, with modification, such a splice organizer, can be used to organi2e the protective tubes of the present invention ~efore use. The modification required of the splice organizer is firstly that it will contain, say, ~i L~

~3~38 ten protective tubes, and secondly that each of these tubss will be broken at about their centre points (where the splice would be in a standard splice organizer3 so that fibres can be inserted into each half tube from their respective joncs and emerge at the middle of the tubes ready for splicing.

A break-out can be made using the kit or method the învention in a variety of different ways~ In particular the order of the various steps may be varied~ Since any one acceptable sequence of ~teps may be quite complex, the kit may contain therein a list of the steps to be taken.

Some of the basic steps are as follows:

1. Remove. the cable jacket 2. Separate the fibres from the jonc 3. Cut off exposed jonc 4. Insert fibres into protective tubes 5. Optionall'y provide a ~arrel or other''support'at the ' ' ' cut end of the jonc 6. Provide protective sheaths over break out regions.

The three basic orders in which the important steps may be performed are as follows:

(A) Remove fibres and insert into tubes both one-by-one (B) Remove all fibres ~ie remove entire end portion of cable jacket) and then insert into tubes one-by-one (C~ Remove all fibres, and then insert into tubes ;imultaneously.

It will be seen that the method of the invention allows (A) to be carried out which is far less likely to cause damage than (B) or (C). The fibres are removed from the jonc generally in a specified order, and in any case in an identifiable way, and each is inserted in-to lX

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one en(] o~ a prol-ective tube on thc organi~er. The ends of the ~ubes in~o which the fibres are inserted will be identlfied either by some characteristic oE the tubes themselves (such as hy colour coding) or by virtue of their rela~ive position on an organizer. Furthermore, the t~lbe~ will be identifiable at their other end, (aqain intrinsically or by simply tr~cing back along the tuhe) so that one can tell from the feee end oE each tube Wll;CIl fibre it contains. A preferred technique is to colour code one end of each tube, and then insert the fibre into the other end. After insertion, the free end o~ the t~t)e will thus bear an indicatinn of which fibre it contains. Each fibre in the cable will in general be lS identifiable by means of its position together with some means which malces one of the ~ibre positions unique.
The means for correlating referred to above can then be used lo tell the installer which (say colour-coded) t~abe to use over which eibre.

2U Where all fibres are removed from the jonc before any is inserted into a tube, we prefer that an organizer be provided which has means for temporarily holding the fibres so that they can be removed one-by-one in an orderly fashion for insertion into the tubes. The 2S disadvantage inherent in all prior art methods of having all the fibres loose can there~ore be avoided by the present invention, even if all ~ibres are removed from the jonc as a first step. An advantage, incidentally, of removing all the Eibres ~rom the jonc in this way is ~hat the unwanted length of jonc can be cut off early in the installation . This can be an advantage if a very long breakout is being prepared. The means for temporarily fixing the fibres to the organizer may, for examplel be one of the types described below for holding the protective 3S tubes to the organizer.

The organizer may be a board which is preferably ~3~3~
--1 o--~lat an(l serve-; also as a ~ork surface for supporting various otl)er ~ieces o equipment ~to be described below) useEul ~or performing the breakout. In one alternative, however, the organi~er comprises a cylinder S on or in which the protective tubes are mounted. One way oE mounting tlle tubes is to pass t~lem from one end plate or: t~le cylincl~r to another. ~lternativeiy, they can be mounted on the outer surEace of the cylinder by wrapping them in or example a helical pattern first with say a left-halld turn and then with a right-hand turn for easy removal.

I3Otll sides of the boar-l may be used, this being particularly preferred where a break-out Eor a spllce is to be made, since twice as as many protective tubes will be required. I~ather than having the ten tubes for one cable break-out on one side and ten for the other cable break out on the other side, we prefer that each set of ten tubes describes a certain path on one side of the board, then passes through a hole in the board and describes a further path on the other side. In this way, both sets of tubes for the two break-outs can be on the same one s-ide of the board, and both sets of tubes for the splice will be on the same other side of the board. The board is therefore used one side up for the two break-outs and then turned upside down for the splice. The tubes ~now containing the fibres) will then ; be disconnected from the board (this may require cutting the board if the tubes pass from one side to the other through a hole) and the tubes stowed into a suitable splice organizer.

In order to carry out the dificult operation of removing the fibres from the jonc, the optical fibre cable is preferably supported in the holding tool. The organizer board, where provided, may have markings thereon ~3~3~

indicat:irlg where this tool should be p~sitioned for easiest insertioll o the fibres into the tubes. In its simplest Eorm the holding means o~ tlle tool may be vice jaws, alld the holding means may be secured to the boarcl, ~or example, by a suction pad or a mechanical arrangelnellt sucll as a clamp or a nut ~lld bolt. The cable can then be held in the jaws ~ the vice while its jacket is removed, and the ~ibres separated from the jonc ancl inserted into the correct tubes.

The holding tool has means Eor rotation of the cable s(~ as to bring diEferent fibres illtO a convenient position ~or removal ~rom the jonc. 'i'llis means for rotation is pre~erably hand operated, an~l preerably indexecl so that each rotational 5tep brings a new fibre into position. Each step ~or a ten Eihre cable would thereeore be 36~. The tool is preferably able to accept a piece oE optical ~ibre cable remote Erom an end, ie any clamping arrangement in the tool should be split in cross-section allowing lateral insertion. In the cable ~0 accessories art this is described as wrap-around, as opposed to tubular. The reason is simply ease of insertion and removal o~ the cable when making long break-outs.

The tool preferably incorporates a magnifying lens to aid insertion of the fibres into the tube.
Where the lens is not part of the tool, it may simply be supplied as part o~ a kit.

The tool supports the cable at two posi~ions along the cable. At one of these positions the cable may merely rest in a groove and be free to rotate; at the other position, however, the tube is clamped by the means mentioned above to cause rotation, pre~erably by a wrap-around barrel which is first ~ssembled around the cable and then slid down the cable until it engages the ~ 3~93~

rotclti~l- mecl~al-lislll of the tool. This barrel may serve I~Ot only to gl^ip tlle cable but also to receive the ends of the protective t~bes when they have ~)een slid over the fibres to their full extent.

~r~le lloldinc3 tool allows the meth~-~ of break-out of the invel-tioll to be e~ficiently perFormed. The cable is positioned in the tool such that its ~ee end extends the required break-out length (say up to 2m) past the support within which the cable ;s clamped by the barrel.
Tlle passive support of the tool will hold the cable at a position about 80-180 mm towards its free end. A short piece of cable is therefore held bet~een the two supports. The jacket is then removed ~rom this piece of cable, or from part of it, a length o~ about 80-l20 rnm being preferred, to prod~ce a "window" of exposed jonc and fibres.

A fibre is then lifted of~ the jonc in this window (this can be done by flexing the cable) and pulled to withdraw it from the length of cable down-stream of the tool, which is still covered with the cable jacket.
Once a fibre has been removed in this way, it can ~hen be inserted into the appropriate protective tube. This technique therefore allows the fibres to be dealt with singly, thus avoiding the simaltaneous release of all ten unprotected fibres.

Two alternative ways of liting a fibre off the jonc will be described. First, a small tool with a pressure-sensitive adhesive applied to an end, or a piece of mastic, may be osed to lift a fibre sufficiently far o the jonc for it to be grasped by hand. Secondly, the initial lifting may be achieved by pushin~ one or more optical fibres from the free end of the cable. A special tool may be used to push the fibres from the end of the ~.3~3~815 cabLe. 1~ one Eibre only is to be ti~ted at a time the special pushir1g tool may compri~e a cylinder with a V-shaped interllal projection. 'L'he cylinder i6 pushed over the jol1c at the free end of the cable so that the V-shaped protection catches the end of the chosen fibre.
Wllere all Eibres are to be lifted at once, the pushing ~ool may comprise a cylinder haviny an annulus therein oE, for example, a resilient plastics material. When this tool i5 pushed over the free end oE the cable, the annulus catches all of the fibres. If the annulus has the correct resilience and size, the cylinder will remain at whatever position it is pushed to, and therefore all fibres wi.ll remain bowed ~way from the jonc at the.
window, ready to be retracted and then inserted one-by-one i.nto the appropri.ate protective tube.

Irrespective Oe whether the protective tubes after insertion of the fibres are locate~ around the jonc one by one, or all together as a final step, some locating means must be provided to hold them in position before positioning o~ the final environmentally protective sleeve. This locating means can in gel1eral be provided in any o~ three ways. Firstly, a barrel as ~escribed above may be used. This type o~ barre.l becomes a permanent part of the finished break-out. It holds the protective tubes by an inter~erence fit, or the protective tubes are integral with an extension thereof which slides over the cut end of the jonc. This harrel can be regarded as being tubular with respect to the jonc and either wrap-around or tubular with respect to the tubes, to use : 30 the terminology introduced above. --The second way uses an alternative type of barrel which is a temporar~ barrel which is used to assemble the protective tubes on the end of the ~onc, but is then removed. This barrel will be wrap-around with respect ~3~
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to bot11 jonc an~1 tul)es. The entls Or the ten I or however mal-y) tuhes are assemb]ed in t~1e wrap-around temporary t~arrel, ~hich is then wrapped around the jonc at a position slightly nearer the ~ree-encl than the position where the break-out is to begin~ It may be held in its wrapped-around configuration by means of a pressure-sensitive adhesive, or by a t~pe etc. The ~ibres are then inserted into respective tubes.
When t:his is done each tube is slic1 longitudinally to close the gap between it and the position where the break-out is to begin. In order to maintain a fixed position where the break-out is to hegin (ie to stop the ~ibres peeling back oE the jonc) an adhesive tape may be wrapped around the cable or an O-ring may be positioned over the cable. Thus, t:he protective tubes are slid until they abu~ the adhesive tape or O-ring. It can be seen that the wrap-around barrel should allow longitudinal movement of the tubes it holds, but not allow rotation or later:al movement which could, of course, result in the fibres being inserted in an incorrect tube.

We prefer that the barrel has means for identifying the fibres or tubes that it contains. For example the channels or holes around its circumference for the tubes could be numbered from one to ten, for a ten fibre barrel. Alternatively colour coding could be provided.
Every channel need not, of course, be marked: if for example the first, third and fourth channel ( any channel being numbered the first) were all marked, even in the same way, then all channels could be uniquely identified. This idea may be developed such that any barrel can be used for a fibre sequence that runs clockwise around the jonc and for the same sequence running anticloc~wiseO This situation may arise at a splice where the two cable ends to be joined are opposite ends of similarly manufactured reels of cable.

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llere a Eil~re sequer-ce marked on the jonc at the end of one cable ~Yill appear clock~ise, an-i that at the end of the other cable ~ill appear anticlockwise. This versatility of the barrel can he achieved using a tubular barrel i~ ~L~posite ends of the barrel are marked accor~inf31yr ancl in the case of a ~lexible sheet wrap-around barrel it can achieved iE opposite sur~aces of the sheet are markcd accordingly, the sheet tllen being wrapped around the jonc with the appropriatc ~lce of the sheet outwards.

1`l"-~ cal~le ~particularly tlle jOIlC 0~ a cable) may o~
course be marked in a similar way to identi~y the fibres it carries. It is in conjunction with such cable markin9 that the means for correlating o khe invention is preferably used. The means or correlatirlg is preferably able to correlate the coding of the tubes with each of the clockwise and anti-clockwise sequences referred to. For example, a matching between a set oE
colours and the first, third and fourth cable markings may be provided.

The third means mentioned for locating the tube is, however, preferred, and this may comprise the end of the jonc itself, optionally with some outer restraining member such as an O-ring or a tape wrap which allows longitudinal movement of the tubes for the reason indicated above. In this case the lateral location is by means only of the jonc, and not (as in the previous case) by some discrete elementO

Some inventive features concerning the protective tubes themselves will now be discussed. One of the most dif~icult steps involved in protecting a break-out in this way is insertion of the fibres into the protective tubes. ~his is due simply to the small dimensions ~L3~3~31!38 involve(l: t~le ~ meter of tlle Fibre will generally be from 1~5-~50 Inicrons, and the interl1~l diameter of the tubes is preferahly from 200 to B00, more preferably ~rom 300-500, especially about ~150 microns. The coefficient oE ~riction Eo~ the outer m~terial of ~he fibre against that oE tlle tube will be import~nt, bu. little difficulty is found in 51 iding the fibres within the tube once the tip has been inserted, except that the job is tedious and fibre breaka~e may occur due to the large lengths that have to be inserted (a total o~ say 40m when splicing two ten fibre cables). secause of this, we pre~er to use the installation tool o~ the invention, whicl1 wi)l be discussed in detail l~elow in connection with the drawings.A preferred material ~or the tubes is nylon or polyvinylidene E}uoride,~ wh;ch is may he cross-linkec3 in order that it retain its strength under any heat which may be applied to af~ect heat-shrinlcage of any environmental seals. In this context, the requirement mentioned above that the fibres within ~he tubes must be ree to movel may be repeated.

The tubes will generally be stored in a coiled configuration'after installation. This can allow stress-reduced or stress-free thermal cycling of the temination or splice. Stress can result from the different extents of thermal expansion and contraction of the fibres and of the tubes. I~ the tubes have a large diameter and are stored in a coiled configuration then the length of fibre appropria~e to the coil will depend on where within the coi] the fibre lies: the inner surface of the coiled tube providing a shorter path than the outer surface. The fibre may be secured within the tube with both ollowing a straight line.
After the end~ of the tube have been e~fectively fixed to tho fibre (by securing the tube for example to a jonc and to a splice) the tube and fibre are then coiled.

~.3~ 8 ~17-Tllis wi]l resulL in the fibre lying along a path having a length ~etween those of the outer ~nd inner sur~aces mentioned above. ~elative expansion ancl contraction of the tube may therefore occur without damage to the fibre or to any se~ls ~t the end o~ the tui)e. The system could oL course l~e arranged such tha~ tlle ~ibre initally following t~le large path, allowing only for contraction, or intially followed the shorter path allowing only for expansion. I~ the tube remained s~raiyill: expansion ln could oE course occur. Furthermore, a length of fibre greater than the linear length o the tube could be installe~i in a straight tube, thus allowing for contraction.
The protective tubing running ~rom a jonc to a splice is preferably in three sections as follows: Kynar (trade mark) clear US ~4/.8; RNF (trade mark o Raychem) colour coded 3/32 150 LG; ancl Kynar clear 1/8 950 LG. This concept may be used in the absence of other methods or kits or articles described herein.

Various techniques have been devised for increasing the size of the tubes at the ends into which the fibres must be inserted. Firstly, the tubes may be cut at an angle to produce a larger hole. A second technique is to heat the ends of the tubes which, depending on the processing hlstory of the tubes, wi~l cause them to expand to a certain extent. A thir~ method is to expand the ends mechanicall~ or by internal pressure, and in this case cross-linking is particularly useful. The expanded region can be shaped to fit the groove in the jonc. The expansion can occur at the middle of a double length tube which is then cut~

In each of these cases, the end of increased diameter may usefully be used to help locate the tube on the jonc against longitudinal movement once it has been properly positioned. For example the enlarged end could ~3~3~

be slipped under al1 O-ring arour1d the jOllC.

A furtl1er technique for ~acilita~:ing insertion of the fibres has been devised which, although it need not involve modiEication to the tubes, can usefully be mentiol1ed here. ~ l~arrel of any oF ti~-~ types mentioned, but part;cularly a temporary barrel whict1 forrns part of the clampin~ tool may be designed in the following way.
A series oE longitudinal holes are provided, into one end of each oE whic11 a tube is inserted and into the other end o~ wl1ich the Eibre is inserted. The end for insertion of the ~ibre is ~unnel-shaped in order to guide the fibre.

Insertion of the fibre into an end of a tube may be helpe(1 hy applying a vacuum to the opposite end. The vacuum may be applied by a vacuum line or a syringe.

Instead of using one protective tube for each fibre, two (or more~ may be used one of which Eits inside the other. This telescopic arrangement allows at will the total length of break-out fibre to be covered, or a part o~ it to be exposed. This is useEul when the breakout is for the purpose of making a splice since it allows a region of the fibre to be exposed for the purpose of injecting light into the fibre. The telescope can then be lengthened in order to cover the exposed region of the fibres either side o~ the splice, and also to cover the small tube within which the splice was made. A further tube around the protective tubes may be provided to straighten the tubes after they have been bent during the light launch/light read splicing technique.
The ends of the two protective tubes may be expanded in order to cover the splice tube. Such a telescopic ~L3~!3~518 , g arrangernel1t ca~ reduce stresses that may otherwise result frolll dif~erential thermal expansion or contraction betweer1 fibres al1d tubes. ~ further advantage of telescopic protective tubes is that "re-entry" can be made to the 5 splice simply by cutting the sylice oul- oE the line.
This can he dol1e since the new fibre ends can be exposed and thel^e will be plenty of length availahle in the tubes for covering a new joint.

It may be desirable that the protective tubes or a part o~ each o~ them be transparent, particularly to visible ligl-t. This allows light to be lauched through the protective t~lbes into t~e Eibres, at a bend in the c~vered f;bres, or the purpose o~ aligning the Eibres where a light launch/light read technique is used .

Some techniques by means of which the protective tubes may be identified are as ~ollows First, they may be located on an organizer in a specific way to align with marks on the board. Secondly, the tubes may themselves be marked. This may be achieved by painting or otherwise colouring the tubes or by installiny coloured bands around the tubes. ~uch bands may be shrinkable, pre~erably heat shrinkable, into engagement with the tubes. A splice between ~ibres can be identified by colouring the small tube within which the splice is made. The colouring used may involve (say) ten different colours, or the single colour or marking system described above in connection with the barrel or the cable.

The protective sleeve which may be installed over the break-out region to bridge the ends of the protective tubes is preferably heat shr;nkable~ It must grip the tubes sufficiently well, but must not cause them to collapse and grip the fibres. Suitable materials ~L3~

:ror ~llis sle~ve may ~, Eor examp'e, polyvinylidene fluoride or ~thylene/virlylacetate copolymer. The sleeve may be provided with an interna]. ad1lesi.ve or sealallt, preferab~y located as annular rings close to eacll end of the sleeve so -I:hat no contamination of the exposed fihres occurs as -they emerge Erom the slesve to enter Ihe protec~ive tubes. Sealants are preferred, particularly nastics. ~l~he sleeve nlay be provided a-t a cenl:re region thereof ~ith a liner oE precise diameter for inst.l~la~ion over the ~onc and fibres with ou~ damage.

The invention and situations in which -the invention may be used are illustrated by the Eollowing drawings in which:

~igure 1 shows a op-tical fibre cable break-out;

Figures 2-5 show four ki-ts containing protective tubes;

Figure3 6 and 7 show two physical forms of organlzer :ls board;

Figure ~ shows in greater detail the fixing of a series of tubes to the board;

Figures 9 and 10 show the use of the protec-tive tubes in the protection oE optical fibre splices;

Figure 11 shows a tool suitable Eor applying the fibres to the jonc; and : Figure 12-14 show insertion tools for Eacilitati~g insertion of fibres into protective tubes.

Figure la shows a cable 1 comprising a ~onc 2 carrying optical fibres 3. A relnforcement ~ runs throuyh the jonc. The jacket is labelled 5. ~n 0-ring or adhesive tape 6 prevents the breakout spreading along ~31~388~3 the cable. A protective tube 7 i6 shown around one of the fibres 3. Figure lb shows a window of jonc exposed; one fibre 3 has been removed fro~ the jacket at the end of the cable, and another is shown bowed ready for removal.

An environmental seal may be provided a1: an end portion of the tube 7 to prevent passage of contaminants along the fibre either into the tube or under the jacket of the cable.
Such a seal is preferably ~ade by means of a gel. Preferred gels are materials having a cone penetration value of 100-350 (10 lmm) and an ultimate elongation of at least 200%. More preferred values being 200-300 (lO lmm) and at least 500%
respectively. The cone penetration values are as measured by ASTM D217-68. An elastic modulus of less than 107 dynes/cm2 is preferred. Silicones and oil-extended polyurethanes are suitable materials. An alternative preferred material is a mastic such as a mixture of substantially non-crystalline materials for example bituminous materials, elastomers, or thermoplastic polymers optionally with inert fibrous or powdered fillers.

Figure 2 shows an organizer board B carrying a series of protective tubes 7. The tubes are held to the board by cut-outs 9 stamped from the material of the board. A holding tool 10 i5 shown within which a cable will be secured. The fibres will then be removed from the cable and inserted into respective tubes 7. The ends of the tubes 7 are held onto the board 8 by pressure sensitive adhesive pads 11. The board shown in Figure 2 is paxticularly for a break-out tschnique where all fibres are removed from the jonc before any is inserted into a protective tube. The bundle of fibres thus exposed is secured to the board in an ordsrly fashion by means of clips 12. The tubes 7 are provided with colour i~ .

~36:~38~3~

coded identification sleeves 13. Other features of the organizer board are a m~asure 14 by mean~ of which the correct extent of cable stripping etc. can b~ detexmined, and a protective sleeve 15 for - 21~ -~r ~3Q13~

insertion over t~1e brea1c-out ~egion. 'l`he sleeve is preferably heat-shrinlcable and has mastic rings 15a at its ends, or an internal coating of an adhesive such as a hot-melt adhesive.

Fi~ures 3 and 4 show alternative designs of organize~ boards 8 for use where the break out is for the purpose of making a cable splice. Each board ~herefore contains two sets of ten prol:ective tubes, 7a and 7b. Tubes from each set are joinel at a splice region, or by splice protection tubes,16. In figure 3, the two ~reak-outs are formed on the underneath of the board 8 as drawn, one to each of the dotted ends o the sets of tubes. The top side o~ the board is then used during the splicing operations. Each tube 7 consists of two tubes in telescopic arrangement, the end o~ the outermost tube being at positions marked 17. Because of the tel~scopic nature of the tubes 7 the fibres can be inserted to ~orm the breakout with the joint 16 intact.
This joint is then broken and the telescope contracted to make the splice. The joint 16 is then re-made over the fibre splIce.

In Figure 4 both the break-out and splicing operations are performed on the same side of the board 8.

The kit 8 illustrated in Figure 5 is of slightly different design. It is preferably about 1100mm long and 80mm wide. ~ series of tubes 7 (optionally telescopic3 is arranged in the kit 8 and held in a particular configuration by a strip of pressure-sensitive adhesive 11 from which they can be easily removed. Another part of the kit is shown with various other components required for cable termination or cable splicing. The components illustrated are for cable splicing.

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lhe tubes may be colour codecl or colour~coding may be provided on the strip 11. The kit may also contain the mea1ls Eor correlating the colour or other coding with identification on the cable. The means for correlating may comprise a card (generally o~ cardboard but the term as used herein includes any material) which bears the releva11t information, preEerably in ~ictorial Eorm.

Where a splice is to be made between two cables each carrying ten optical fibres, two boards as shown in Figure 5 will be required. A break-ont is constructed at an end of each cable~ Eor which the ten tubes 7 will of cour~e be required. Each of the two break-out regions is then protected as described above b~ means of a recoverable tube 15, which is preferably transparent and ~0-80 especially about 60mm lon~. Sealant strips 15a are pre~erably wrapped around the cable immediately either side of the break-out and the tube 15 shrunk over them, such that the strips 15a provide seals at each end of the tube 15. The O-rings 6 may be used as an installation aid during preparation of the break-out. The tubes 16 are for protection of the splices to be made between the fibres from each cable. These tubes are preferably 60-100 especially about 80mm long. F;ve such tubes 16 are provided in each kitr so that the two kits required will contain ten splice protection tubes, sufficient for the ten splices to be made. The ends only of the tubes 16 nee~ be recoverable. Each tube 16, which may be colour coded, is recovered over the small splice tube within which the splice is made and down onto engagement ; ~ 30 with protective tubes 7 at either si~e of the splice.
Where a kit of the general type shown in Figure 5 is to be used for a cable termination (rathQr than for a splice), ten termination protection tubes (preFerably colour coded) would be provided rather than the five tubes 16. Such termination protection tubes may be of ~3~3~38 -2~--non-unifor11 croe;s-section, having a narrow end for recovery OlltO a protective tube 7 and a wide end for recovery onto the connector or housing where the fibre is to be te~minated.

Yigure 6 shows a board ~ provided by a carton t8 in which tl-e tubes 7 are supplied~ The carton has printed thereon a set of instructions 19. The carton unfolds along fold lines 20, and iE a greater curvature is desired, extra ~olds 21 may be provided.
The carton may conveniently be made of cardboard or similar material, and will pre~erably be disposable~

An organizer board in the form oF a tubular carton 22 is shown in Figure 7.

Figure 3 shows a wrap around barrel 23 having longitudinal channels in which the tuhes 7 are a snap ~it.
:
In figures 9a, b and c the various stages in protecting a fibre splice are shown. The tubes 7 have flared ends 24 Eor encasing a colour coding tube 25 which is to cover the small splice tube 26. The splices 16 shown in Figures 3 and 4 include the identification tube 25. The original joint between the two tubes 7a and 7b is broken and the fibers are made to emerge by co}lapsing the telescope as previously described. The tube 25 is placed over one of the fibres 3a or 3b and an outer protective sheath 27 is placed over one o~ the tubes. The ~ibre splice is then made inside the tube 26, and the tube 25 is re-positioned, the telescope is extended and the sheath 27 is shrunk into position. The sheath 27 should be transparent so that the colour coded tube 25 is visible.

~3~3~3Eil~3 Arl eTld pOI. t i OIl oE the tubes 7a or 7~) may be provided r.~ith an environmenta:L seal to prevent contam~ ants passing along tlle fibre. SUCh a seal is preferably made by means of a gel, r~reEerred mater;als beillg described above.

~n array oE splices is shown in Fi~lre lo.

Figure 11 shows an inventive encapsulation for a splice between two optical :Elbres in protective tubes. A convoluted s-train-relief -tube is provided which is surrourlded by a support tube. Inside each end of the strain-relief tube is pruvided a transition tube ~drawn cross-hatched). A heat-shrinkable sleeve th~n extends from each end of the transition tube to provide a seal between the ingoing protective tubes an~ the transition tube. The spli.ced optical fibres and their protective tubes are omit-ted froln the drawing for clarity. The purpose oE the :15 corrugated straln relieE tube is to allow relative movement bet~leen the protective tubes and the internal optical fibre that may result from their different coefficien-ts of thermal expansion. The op-tical fibres may be effectively fixed rela-tive to their protec-tive tubes at the break-ou-t position on the jonc, and therefore relative movement must be accommoda-ted elsewhereO
The corrugated tube can be compressed in response when the system is heated (the protective tube having in general a higher coeff.i.cient of expansion than the glass optical fibres) and can extend on cooling, thus allowing thermal cycl:lng. ~ change ln length of the corrugated tube o~ at least 5mm, pre~erably at least lOmm, especially at least 25mm is preferred such as allowabte change may be attainable from the rest position by compression, by extension or by both.

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I;igure 12-l~ SIlOW various embodiments of a tool ~or Eaclilit:atil-(J insertion o~ fibres into protective tubes.

FiCJUL-e 12 5hows a block 2B whicll may be used alone but whicl- is pre~erably used together with a substantially mirror ima~e block which lies on top oC it. Grooves 29 (or wl-ere a sinc~le block is used, I-oles 29) are provided ~or example by macllinin~. ~t one end, tlle grooves 29 broaden into a Eunnel shaped portion 30. A central portion 31 is o~ smaller size and pre~erbly oE V-~haped cross-section. ~rhe other end 32 oE each groove 29 is broader and also may terminate in a funnel shaped portion. The portion 30 serves as a guide means for insertin~ the ~ibres into the narrow groove 29. The protective tubes are inserted into the broader grooves 32. ~]l portions of the grooves 29 preEerably have a commoll axis. A gripping means 33, such as a ~oam or rubber strip, is provided to retain the protective tubcs in the groove 32. A means for advancing the fibres into the protective tubes is provided at 34. The means for advancing is preferably a roller, which may be rotated by hand but which is preferably rotated by means of an electric motor. Where two blocks 2B are provided each may contain a roller 43~ or only one roller may be provided.

The dimensions shown in Figure l are preferably as follows:

A 5-15 more preferably about 10mm B 2-6 more preferably about 4mm C 2-5 more preferably about 3mm D 0.5-1.5 more preferably about 0.9 E 0.15-0.35 ~ore preferably about 0.27 F 3-7 more preferably about 5 G 3-10 more preferably about 6.

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'l'lle tool shown in Figure 13 may also be used as shown, but prefel:ably a second mirror image block is combined Witll the one shown. DiEEerences from Figure 13 are that pegs are sllown for locating the two mirror image bloclcs in correct aligrlment, that only five fibres can be dealt with at a time, that tlle driving roller is positioned outside the grooves, and tllat remote guiding means 35 are provided for the Eibres. ~ fibre 3 and a protective tube 7 are ShOWIl in part.

Figllre 14 illustrates a similar tool, but designed Eor a sinclle fibre. The means for advancing the flbre comprises a ~air oE rollers 34 positioned such that the fibre passes through their nip. ~s beforer a second block 2~ is preferably used in conjunction with the one shown, and the rollers are preEerahly driven by an electric motor.

~ n advantage o providing the tool as two blocks 28 is that the tubes and fibres can easily be placed in groove portions 32 and 30 respectively when the blocks 2~ are separated. Then, the blocks can be brought together, and the means for advancing operated.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of protecting an optical fibre by a protective tube applied over the fibre by means of an insertion tool, which method comprises (a) inserting the tube into means of the tool for locating the tube; (b) inserting the fibre through guide means of the tool into means of the tool for locating the fibre, the means for locating the tube and the means for locating the fibre being such that end portions of the tube and of the fibre have substantially the same axis; and (c) advancing the tube and/or the fibre along said axis by advancing means of the tool.

2. A method according to claim 1, in which the insertion tool additional has the function of a holding tool for the cable and has means for rotating the cable about its longitudinal axis.

3. An insertion tool for inserting an optical fibre into a protective tube, which comprises guide means for accepting an end of the fibre; means for locating the fibre; means for locating the tube, the means for locating the fibre and the means for locating the tube being such that end portions of the fibre and tube have substantially the same axis; and means for advancing the fibre and/or the tube along said axis without damaging the fibre.

4. An insertion tool according to claim 3, in which the means for advancing comprises at least one of roller against which a fibre or tube bears.

5. An insertion tool according to claim 4, in which at least one of the rolls is powered by electricity.

6. An insertion tool according to claim 5, which is capable of advancing the fibre and/or tube in each of two mutually opposite directions.