WCA January 2013

performances, together with the fire behaviour as reported in the following. In Picture 1 two cable samples are shown. 2.4 Cable characterisation The two cable designs have been manufactured with three different types of optical fibres, ie SM-R, NZD and MM. The cables have been tested according to the main international fire tests, ie IEC 60331-25 and EN50200. In Pictures 2 and 3 the fire tests performed on the cables are shown. Each type of fibre has been closed in loop and connected with a Led-Power meter, measuring the increase of attenuation at 1,310 and 1,550 nm in the circuit with SMR fibres, at 1,550 nm with NZD fibres and at 1,300 nm with MM fibres. The fire lasted 90 or 180 minutes and the recording of the attenuation values has been extended up to 15 or 30 minutes later. Examples of some test results are collected in Figures 3 to 5 . All the results are positive with very limited attenuation increase (less than 0.2 dB/fibre) for any of the fibre types tested. This really confirms that the ceramifiable protection, in combination with an appropriate cable design, is able to preserve the fibre performance from fire load also in cable solutions with high fibre density. 3 Conclusion The cable family developed with a special protective layer to preserve the fibres transmission performances from fire action is particularly effective when the application of flame is turned off and the material contractions start. The cables have been developed in metallic armoured and all dielectric version with the optical fibres organised in micromodules up to 144 fo with a very compact design, and are now available on the market. 4 Acknowledgements The authors would like to thank their many colleagues within Prysmian who have contributed to this work, and in particular Paolo Marelli and Gianluigi Radaelli for the helpful support.

Fire resistant test EN 50200 All dielectric micromodules cable 180 min fire + 30 min cooling

Attentuation [dB/fibre] Attentuation [dB/fibre]

Time (minutes)

❍ ❍ Figure 4 : Fire resistant test of all dielectric versions according to EN50200

Fire resistant test EN 50200 Armoured micromodules cable 180 min flame + 30 min cooling

Time (minutes)

❍ ❍ Figure 5 : Fire resistant test of the armoured version according to EN50200

For the dielectric version, over the central ceramifiable inner tube an intermediate flame retardant sheath is applied reinforced by two glass rods longitudinally embedded into the wall of the jacket; the glass rods withstand both tensile load and low temperature shrinkage. Then some fire resistant tapes are applied together with the outer LSZH sheath. The cross section of the all-dielectric version developed is shown in Figure 1 . For the metallic armoured version, the corrugated steel tape is applied over the ceramifiable tube followed by an outer HFFR sheath reinforced by two glass rods with the same function described above. The cross section of the armoured version developed is shown in Figure 2 . 2.3 Cable trials and production Cables in all dielectric and metallic versions have been developed from 48 to 144 fo. Many experimental trials have been carried out before the production of the final versions; then the cables have been fully characterised for optical, mechanical and thermal

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Wire & Cable ASIA – September/October 2007 Wire & Cable ASIA – January/February 13