Cable takes the knocks without armour

Pirelli has developed a novel range of dielectric fibre optic cables offering greatly improved resistance to crush and impact, thanks to a unique integrated protection system.

Pirelli has developed a novel range of dielectric fibre optic cables offering greatly improved resistance to crush and impact, thanks to a unique integrated protection system.

The Air Bag cable is based on a composite structure of extruded polymeric materials, each with its own specially selected mechanical properties.

Designed to replace heavy, rigid metal-armoured cables in situations where damage protection is a major concern, Air Bag cable is not only lighter, more flexible and easier to install than armoured alternatives, but offers much better resistance to compression and shocks, which can damage or even permanently disable cable performance.

Developed by optical specialists at Pirelli Labs, Air Bag cable is set to go into full-scale production at all of Pirelli's optical cable plants around the world, following successful trials at the company's Livorno Ferraris plant, near Milan.

The most important first market for the new cable has been railway-based communications networks, where the traditional practice of laying cables in open trenches or in galleries exposes them to high risk of mechanical damage.

Pirelli is already working on a pilot implementation of the Air Bag cable with customers in Austria and Holland, and will be showcasing the new designs to major railways and rail network operators across Europe in coming months.

According to Agusti Valls, Vice-President, Pirelli Telecom Cables and Systems R and D, the unique structure of these Air Bag cable designs, which incorporate an optical fibre core, specially developed filling compounds with high mechanical resistance, dielectric rodent protection and flame-retardant inner and outer layers, effectively acts as a shock absorber, allowing the cable to resist damage and recover its shape after crushing or impact without permanent deformation.

"When subjected to a sudden shock, metal-armoured cables often suffer nonrecoverable deformation that can generate permanent stress in the cable core", he said.

"Air Bag cable protection technology helps protect an organisation's costly investment in cable infrastructure by combining state-of-the-art optical fibre with very high energy absorption capability, for unbeatable overall resistance to both crush and impact".

Totally compatible with existing cabling networks and traditional accessories, the Air Bag cable protection technology, which replaces the metallic moisture barrier used in armoured cable, along with its specially-designed dielectric armour of treated glass yarns, which replace standard metallic rodent protection, allows the new cable to easily match traditional metal-armoured cable for long-term reliability.

However, the reduced weight of the Air Bag cable - up to 50% less than armoured alternatives - and its much greater physical flexibility makes installation faster, cheaper and easier.

With current trends in trunk and access network deployment driving strong demand for fully dielectric optical cables, new installation techniques like cable blowing and exploitation of existing rights of way are favouring smaller, lightweight cable solutions.

At the same time, increased penetration of optical fibre transport into the local loop to support emerging broadband services will increasingly mean smaller, more flexible, lightweight, cost-effective cables.

The first cable system to effectively address these trends through a light, flexible structure incorporating exceptionally high mechanical performance, Pirelli Air Bag cable protection technology promises significantly reduced cable and installation costs, unprecedented reliability and exceptionally long service life.

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