ANALYSIS OPINION


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Miniaturisation and the space races


Cable miniaturisation in FTTH deployments: choosing the right 200-micron fibre for outside plant networks, by Vanesa Diaz, Corning


O


ne major factor that currently inhibits fibre to the home (FTTH) roll-outs is that the current access network infrastructure in many


European countries is crowded and the level of investment required to install new plants in the ground is still very high (amounting to as much as 56 per cent of the overall deployment costs[1]


). As a result, incumbents and


alternative operators are looking at new technologies that can minimise the cost of new deployments and/or maximise use of their current infrastructure capabilities to deliver a more positive FTTH business case.


Miniaturisation is only made possible by the smaller, tighter designs of minicables


The miniaturisation of cables and fibre infrastructure in FTTH deployments To alleviate the high levels of investment required to deploy a FTTH network and to maximise current conduit usage, many operators are opting for the miniaturisation of materials and installation equipment. Microtrenching technologies, alongside microducts and small diameter cables (so-called minicables) are some of the most relevant examples of these technologies. In new deployments, microtrenching claims to reduce civil costs by 80 per cent[2]


by


replacing traditional trenches with a narrow slit that is sawn in the surface of the road, into which microducts with narrow, vertical cross-sections are placed. Microducts sub-divide the internal duct space into smaller compartments into which minicables are installed, allowing efficient sharing of overall duct-space and leasing of spare ducts. Tis technology also allows the addition of increased network capacity in the future by installing new minicables in spare microducts. In greenfield deployments, this enables a lower initial level of investment and later ‘pay-as-you-go’ upgrades of the network infrastructure. In brownfield networks, the smaller, lighter, and more flexible design of minicables makes them perfect to be


12 FIBRE SYSTEMS Issue 5 • Autumn 2014


Vanesa Diaz


air-blown into existing, crowded ducts that otherwise would be deemed full. Fundamentally, miniaturisation is only


made possible by the smaller, tighter designs of minicables. Until recently, the cable industry had managed to deliver some modest reductions in cable size using standard G.652 fibres while still meeting industry-required cable performance. However, a new generation of single-mode optical fibres with a smaller coating diameter has recently been developed, making it possible to reduce cable size even further.


Introducing 200-micron diameter fibres ITU-T Recommendations G.652 and G.657 describe the geometrical, mechanical, and transmission attributes of single-mode optical fibres[3]


. Although these fibres have evolved


greatly since the first commercially-viable product was introduced by Corning back in 1970, their geometrical dimensions have always remained the same. Core (9µm) and cladding (125µm) trap the light using the principle of internal reflection while a 250µm


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