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FEATURE OPTICAL FIBRE


Redefining density G


Corning’s Matthew Guinan considers how products that maximise density can help operators cope with the increasing amounts of fibre in their networks


lobal IP traffic has increased fivefold since 2010 and there is no reason to think that this growth will stop anytime soon. Attempts to


keep pace with such capacity demands have seen a dramatic increase in optical cable installations and installed optical fibre counts, causing unprecedented levels of congestion in carrier duct infrastructure. Soon, the large traditional cables installed in these ducts will reach capacity exhaust but, due to the high cost of civil works, many operators will be reluctant to invest in new duct and cable infrastructure. It is obvious that smaller cables with higher fibre counts are needed to provide vital bandwidth and optimise the use of precious duct space, but with so much extra fibre in the network comes another challenge. How can operators physically manage it all without taking on new, expensive central office space?


Smaller cables, bigger possibilities Te key to beating the cyber traffic jam lies in maximising fibre density: in other words packing more fibres into a smaller space – both in terms of cable and duct. In response, vendors have developed miniaturised cables with fibre counts up to 144 fibres that can be up to 50 per


cent smaller and 70 per cent lighter than traditional loose tube cables†


. Tis cable


miniaturisation naturally yields an increase in fibre density, in turn enabling greater fibre capacity and optimised duct utilisation today and scalable, cost-effective capacity provisioning for the future. As with loose tube cables, micro cables


typically feature 12 coloured fibres per buffer tube, but these tubes are around 40 per cent smaller, making micro cables less robust than traditional loose tube cables. Consequently they must always be deployed in single or bundled microducts for added protection. Tese mini plastic conduits sub-divide internal duct space into smaller compartments and are light so that, if space allows, a loose microduct can be safely blown or pulled alongside a loose tube cable in an occupied duct. At approximately 12mm in diameter, the largest loose tube cable that can fit into an occupied duct may only provide 96 fibres, but a Ø 12/10mm (outer diameter/inner diameter) microduct can accommodate a micro cable containing as many as 144 fibres, thereby providing up to 50 per cent more fibres to allay total capacity exhaust for longer (see Figure 1). Excavating roads and pavements can cost as


much as €110,000 per kilometre so the motivation to utilise every millimetre of legacy duct space is obvious; but eventually operators will run out of space and will be forced to deploy new duct and cable infrastructure. At this point, they can at least eliminate the need for retrenching for a significant period of time by installing one or more multi-way microduct bundles and fibre-dense micro cables. Te most common duct size in Europe is


Ø 40/33mm and the largest typical loose tube cable compatible with it provides 288 fibres. If an operator were to instead deploy a seven-way microduct bundle with Ø 12/10mm


Matthew Guinan


High-density micro cables use 24 fibres per buffer tube rather than 12


microducts, they could install seven 144-fibre micro cables and benefit from 250 per cent more fibres. Moreover, to upgrade beyond the initial 288 fibres with loose tube capacity would require months of retrenching at significant expense, whereas a micro cable upgrade would incur just the cost to purchase and install a new cable into one of five vacant microducts. Tis process could be completed in a single day and repeated another four times before the operator would have to consider opening up a trench.


Figure 1: Microducts and micro cables are an efficient way to add more capacity to traditional ducts as this example shows: a Ø 12/10mm microduct and 144-fibre micro cable is overlaid into a duct containing a legacy 288-fibre loose tube cable


† Note: All diameter, weight, and fibre density comparisons between


traditional loose tube cables, micro cables and high-density micro cables made in this article refer to Corning products only. Competitive offerings may vary.


Issue 9 • Autumn 2015 FIBRE SYSTEMS 25


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