AU605646B2 - Optical cable jointing method - Google Patents

Description

605646 coc 0 0 0 o oo o 0 0 a00Q 00000C 0 C 0 0 00 000 00 0 0 0 0 Q 00 0 00C 0 0 0 0 00 0 00 *C 0 0 COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952-1969 COMPLETE SPECIFICATION FOR THE INVENTION ENTITLED 0 000000 0 0 000o0~ 0 0 "OPTICAL CABLE JOINTINO METHOD" 00 o 0 00 0 0 The following statement is a full description of this invention, including the best method of performing known to us:- 4 This invention relates to fibre optic cables and in particular to a method for jointing fibre optic cables of the type in which the optical fibres are arranged in slots or grooves in a grooved element. Such cables are well known.

An object of the present invention is to provide a cable joint which has a flexibility comparable with that of the cable and which can take up the longitudinal strain in the cable core under all manufacturing, installation and operating conditions.

Accirdingly, there is provided a method of jointing two 0 3 fibre optic cables of the type comprising a plurality of op- 0000 tical fibres arranged within slots of a slotted element, a 0000 0 0 0, central strain relief member arranged within said element, 0 0 0 at least one outer sheath member surrounding said element, and water repellant material filling spaces between said outer sheath member and said element, said method including F the steps of splicing said optical fibres of each fibre optic cable, terminating the relief member of each said cable in a terminating sleeve, and fixedly enclosing both spaced terminating sleeves within a jointing tube.

The method of the present invention is particularly C C CC useful in connection with making factory joints of submarine Cfibre optic cables. The method may, however, also be useful in connection with making repair joints. In order that the invention may be clearly understood, embodiments thereof will now be described with reference to the accompanying drawings, In which: Fig. 1 schematically, illustrates the main principles of the invrention; Figs. 2 and 3 illustrate one embodiment of a termination sleeve, and Fig. 4 shows details of a complete joint.

In Fig. 1 a fibre optic cable I is to be jointed to a fibre optic cable 2. For simplicity only the grooved elements 3 and 4~ respectively and the central strain relief members 5 and 6 respectively of the cables are shown. The grooved element is usually extruded closely around the strain relief member, which may be an FRP (Fibre Rleinforced Plastic) string. The optical fibres (not shown) are arrangud in the grooves or slots which are filled with a silicon compound or similar water repellant material. The optical fibres (not shown) are also arranged in the slots or 0 open grooves 22 (Fig. 3) in termination sleeves 7 and 8.

These grooves are also filled with the water repellant cornpound. The termination sleeves are shown in greater detail in Fig. 2. The cables should be arranged in a jig (not shown) so as to define the distance between the two cable eands. The sleeves 7 and 8 abut the ends of the elements 3 and 4i. The strain relief members 5 arid 6 are respectively secured to the sleeves 7 and 8.The relief members are in- *serted through central holes 20 (Fig. 2) In the sleeves. A wedge like device (not shown) miay be applied to the end of the mem~bers 5, 6 appearing In the conical end 21 of the bore for locking the elem~ents to the sleeves. Gluing agents may also be applied, Before jointing the fibres, a tube 9 i~s pulled over one or the cables to the side of the jointing area. Aftev' splicing the optical fibres, the tube 9 is pulled back and the sleeves 7 and 8 are secured to a tube member 9 Ly filling corresponding recesses 10, 11. in the in- 3 L ner surface of the tube 9 and recesses 12, 13 1 n the outor surface of the sleeves 7 and 9 with a moldable material. 1ike epoxy. The filling holes are not shown. Care must be taken to ensure that none of the jointed fibres have any longitudinal strain. The jointing tube should preferably be made of a transparent material Kith a relatively high module of elasticity and a high tensile strength factor. In the preferred embodiment the jointing tube is made of a polycarbonate material having a module of elasticity in the order of 2.200 N/mm squared and a break elongation factor in the order of In Figs. 2 and 3 a termination sleeve 7 is illustrated.

Fig. 2 shows a partial cut through Fig. 3. The termrination sleeve is provided with a central bore for insertion of the strain relief member. The sleeve is provided with a number of slots or grooves 22 to accommodate the optical fibres and the end 23 of the sleeve abutting the groove element 3 (Fig.

1) is conically formed to allow for a certain dispacement of the optical fibres. The slots 22 may follows the same curvabure as the grooves of the groove element or they can also be parallel with the longitudinal axis of the sleeve. The right hand end 21 of the bore through the sleeve is as mentioned a little wider T'han the left hand side of the bore, so that then the strain relief' member is inserted through the sleeve from the left hand side and cut In alignment with the sleeve end appearing In Fig. 3, it may be locked within the bore by a wedge like device (not shown) and glue.

Before molding the sleeve 7 (and 8) to the tube 9, the fibre slots 241 in the recess area 12 are filled with a compound compatible with the cable compound, and covered with a '4 L i tape (not shown), so that the epoxy glue does not enter the fibre slots.

Fig. 4 shows a partially sectionalized view of some de tails which completes the left part of the joint. This figure schematically illustrates, as in Fig 1, the cable 1, the grooved element 3, the strain relieve member 5, the termination sleeve 7 and the tube 9. Three fibres 30 are illustrated within the tube 9. The tube has holes 31 for filling the joint with water proof compound, and holes 32 for filling the recess space 10, 12 with epoxy glue. After filling, these holes are closed. A glue stopping tape 33 or the like is indicated in the bottom of the recess 12. The end of the o *tube 9 may be closed by a bushing 311, and the outer layers 36 of the cable may be replaced as shown and .orared by a shrink tube 37. The termination sleeve(s) 7 (and 8) as well as the bushing 34 are preferably made of a sea water resistant material such as stainless steel.

The above detailed description of embodiments of this invention must be taken as examples only and should not' be considered as limitations on the scope of protection.

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Claims (8)

1. A method of jointing two fibre optic cables of the type comprising a plurality of optical fibres arranged within slots of a slotted element, a central strain relief member arranged within said element, at least one outer sheath member surrounding said element, and water repellant material filling spaces between said outer sheath member and said element, said method including the steps of splicing said optical fibres of each fibre optic cable, terminating the relief member of each said cable in a terminating sleeve, and fixedly enclosing both spaced terminating sleeves within a jointing tube.

2. A method as claimed in claim 1, wherein said joint- ing tube comprises a transparent materLal with a relatively high module of elasticity and a high tensile strength.

3. A method as claimed in claim 1 or 2, wherein said jointing tube comprises poljcarbonate material having a mod- ule of elasticity in the order of 2.200 N/mm squared and a tensile strength factor in the order of'

4. A method as claimed in any one of the proceding claims, wherein each said terminatir. 6 sleeve includes a cen- tral bore into which the respective strain relief member is passed and fixedly secured.

A method as claimed in olaim 4, wherein said central bore is cone shaped for receiving a wedge member for fixedly securing the strain relief member in the terminating sleeve.

6. A method as claimed in any one of the preceding claims, wherein said terminating sleeves each contain slots which align with the slots of said slotted elements.

7. A method as claimed in any one of the preceding claims, wherein each terminating sleeve is provided with one or more recesses in its outer surface which correspond with i one or more recesses provided in the inner surface of the said jointing tube, and filling said recesses with hardening material to lock the terminating sleeve to the jointing tube to prevent longitudinal movement.

8. A fibre optic cable joint substantially as herein described with reference to Figs. 1 to 4 of the accompanying drawings. DATED THIS TWENTY-FOURTH DAY OF OCTOBER, 1988 ALCATEL N.V.