EoW September 2009

technical article

In this way, not only can gel consumption be reduced, but good water-blocking performance of the cable can be guaranteed. Researchers performed the same experi- ment on cables with tape armour. The optimum gel parameters for a cable with 23mm wide steel tape armour are 200×19×0.2mm (if the gel is sprayed at intervals of 1m). Otherwise, either the cable samples failed in the water penetration test or the gel was likely to overflow in the production. After the optimum gel parameters had been selected, researchers employed this new method in a practical production of cables with metal tape armour. The initial pilot production and the following mass production verified that the method was quite effective since none of the cables failed in the water penetration test after the production. In addition, five drums of cables with steel tape armour and tape armour were randomly chosen for further tests. First, a temperature cycling test (-40º~+70º two cycles, lasting for 12 hours at each temperature point) was performed on the cables. Then, a mechanical performance test was carried out on the cables, including items such as vibration, repeated bending and torsion. After that a water penetration test (3m long cable sample, 1m waterhead, 24 hours) was undertaken again to testify the reliability of the method.

Water penetration test

Cable Sample

Gel parameters

A B C D A B C D E

Passed Passed Passed Passed Passed Passed Passed Passed Passed Passed

Cables with steel tape armour

200x20x0.3mm (at an interval of 1m)

Cables with aluminium tape armour

200x19x0.2mm (at an interval of 1m)

E

Table 3 ▲ ▲ : Water penetration test results after cable performance tests

Table 2 shows the test items in mechanical performance test. Table 3 records the water penetration test results after above cable performance tests. The test results show that after severe temperature cycling and mechanical performance tests, the water-blocking performance of the cables made with this new method is still very good. Thus it can be predicted that the water-blocking performance of these cables can be guaranteed within their service life. 5 Conclusions Generally, the water-blocking performance at the overlap of the metal tape in optical fibre cables cannot be absolutely

guaranteed in practical production. The layer-by-layer method for cable gel filling proposed in this paper can effectively solve the problem. This method can be easily implemented on existing sheathing lines and it can reduce production cost by using ordinary filling compound instead of water-swellable gel along the cable core. It can also save material by intermittently injecting gel along the metal tape. Moreover, researchers have foundoptimum gel parameters through experiments to minimise the gel consumption without sacrificing the water-blocking performance of the cable. The water penetration test after the temperature cycling test and the mechanical performance test of the cable shows that this new method is quite reliable and it will act as an excellent solution for cable gel filling during the production of cables with metal tape armour. n 6 Acknowledgements Special thanks should be given to those who gave their kind assistance to the implementation of this method.

Table 2 ▼ ▼ : Test items in mechanical performance test

Vibration (amplitude: ±3mm)

Repeated bending (load: 150N)

Torsion (load: 150N)

Cable Sample

±90° 30 times ±90° 60 times ±90° 100 times ±90° 100 times ±90° 100 times ±90° 30 times ±90° 60 times ±90° 100 times ±90° 100 times ±90° 100 times

±90° 10 times ±180° 20 times ±360° 100 times ±360° 100 times ±360° 100 times ±90° 10 times ±180° 20 times ±360° 100 times ±360° 100 times ±360° 100 times

A

10 min

B

20 min

Cables with steel tape armour

C

60min

7 References

D

60min

[1] IEC-60794-1-2, Optical Fibre Cables Part 1-2: Generic Specification-Basic

E

60min

This paper was first presented at the 56 th IWCS and is reproduced with the permission of the organisers.

A

10 min

B

20min

Cables with aluminium tape armour

C

60min

Yangtze Optical Fibre and Cable Co Ltd Wuhan, Hubei, PR China Email : zhouzhenfu@yofc.com

D

60min

E

60min

80

EuroWire – September 2009