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Fibre duct congestion

Fibre duct congestion

Fibre duct congestion

Open access enables faster, more economic fibre network deployment. However, ducts are becoming overfull, explains Richard Moyes, Digital Solutions Business Director - Optical & Connectivity, Prysmian UK

Solving the issue of congested ducts for faster, more economic high-speed fibre rollouts

Open access to ducts — underground channels that house cables — enables providers to share infrastructure. This reduces the need for extensive digging and disruption, while lowering the environmental impact of rollout. Operators can avoid significant costs (digging trenches is one of the costliest aspects of deployment) and roll out much faster. This lowers prices and boosts availability and services. 

However, most ducts were designed for copper networks or early fibre deployments and can’t accommodate today’s fibre cable requirements. As providers try to expand their networks, they’re increasingly encountering overfull ducts. That means they may need to resort to more expensive and time-consuming alternatives, such as digging new trenches or building additional duct systems. This increases the cost of deploying fibre and delay the availability of high-speed broadband to consumers. This congestion can also limit access for new broadband providers, reducing competition and hindering development of open-access models.

The current situation in the UK clearly demonstrates the opportunities and challenges. The new government seems committed to existing targets and funding commitments to speed up the roll-out of gigabit-ready broadband. 

“Accelerating the rollout of fast broadband and modernising the country’s digital infrastructure is crucial to kickstarting an era of sustained economic growth in every part of the UK” stated Digital Infrastructure Minister Chris Bryant. 

When announcing Public Infrastructure Access (PIA) reforms in 2018, OFCOM estimated that open access would cut the cost of laying fibre by 50%. AltNets have established their businesses based on this premise. In 2022 CityFibre’s Director of Compliance Sarah Parsons conceded that “over 50% of the properties we connect with our own fibre today are serviced through PIA”. Netomnia CEO Jeremy Chelot pointed to the low cost of his company’s installation being very closely connected to its use of existing infrastructure and BT exchanges. Openreach’s Annual Review 2023 reported that 120 companies were using its physical infrastructure for full fibre builds. This included 32,000km of ducts compared to just 2,500km of ducts just four years earlier.

Free access to existing infrastructure was crucial to opening up the market for network builders, but there is a limit to its capacity and the current struggle to maximise the efficiency of existing ductwork is likely to intensify. The capacity issue intensifies when overbuild (more than one fibre line available in a given location) is added into the mix. Overbuilding is a feature of a competitive market. An analysis of full fibre rollout plans, conducted for the Financial Times, found that network operators collectively have plans to build to around 80 million premises – in a nation with a total of 31 million premises. This gives an indication of just how many operators are likely to be targeting each premises. Further pressure will be placed on already well-used ducts as the installation of new poles becomes increasingly problematic. 

Legislation allows network builders to access other utilities’ infrastructure, but there has been a marked reluctance to do so, leaving existing telecoms ducts and poles as the preferred fall-back for new fibre roll-out. In the face of opposition from residents, government called on operators to “limit installation of telegraph poles” as they risk upsetting communities by “inappropriately or unnecessarily throwing up new infrastructure”. At least one network operator has pledged to “never use poles as part of network deployment”.

Maximising capacity through miniaturisation

Maximise the capacity of the existing underground ducting network is key. This can be achieved through the introduction of ever smaller cables and technical innovations that allow them to be installed into already crowded ductwork. Innovative installation techniques such as overblow allow for retrofitting cable with minimal access required to existing ductwork. Without such innovation, the entire enterprise of enabling universal Gb could be limited by the simple problem of too little capacity in existing ductwork.

Fibre cable miniaturization is essential to addressing congestion and improving rollout efficiency, speed, and affordability. Miniaturized fibre cables have a significantly smaller diameter compared to traditional cables. This reduction in size allows more fibres to be installed in the same duct space or frees up space for future upgrades. As many legacy ducts are congested with older, larger cables, using smaller fibre cables maximizes the utilization of existing infrastructure. Higher fibre density per duct can support higher data transmission capacities and more subscribers. 

With smaller cables, operators can add fibres without digging up roads or installing new ducts, reducing civil works costs and disruptions. Smaller cables are easier and faster to install, reducing labour costs and enabling quicker fibre network rollouts. Teams can handle more fibre per project, enabling more efficient network scaling.

As network demands grow, easy upgrades without the need for additional excavation or duct expansion are possible. In urban environments, where duct congestion is particularly problematic due to limited space, miniaturized cables allow network providers to extend their fibre reach to more customers and businesses in crowded locations without significant infrastructure upgrades. Smaller fibre cables are easier to route inside buildings and tight spaces, making them ideal for providing high-speed internet to Multi-Dwelling Units such as apartment buildings, office complexes, and other high-density residences. 

In short: miniaturization of fibre cables is a critical innovation that addresses the challenge of cable duct congestion, making it possible to deploy more affordable higher speed networks. By reducing the physical size of the cables, operators can maximize the use of existing duct space, minimize civil engineering costs, speed up deployment timelines, and future-proof networks for growing capacity needs, while minimizing impact on the environment and urban landscapes.

Prysmian’s innovation teams have been steadily reducing the size of fibre cable with the Sirocco Extreme 864f microduct cable presenting the most recent step forward. This innovative cable uses BendBright 180 micron optical fibre, the only 180 micron optical fibre on the market, and can house 864 fibres within a 9.8mm diameter cable providing a fibre density of 11.5 fibres per square millimetre, making it possible to install in ducts with as little as 12mm diameter capacity. 

Prysmian’s Sirocco Extreme microduct cables not only provide cost savings to network owners and builders but also enable them to reduce carbon and environmental footprints. The cables ensuring compatibility with existing G.652 fibres and readiness for evolved systems. Sirocco Extreme cables incorporate Prysmian’s PicoTube technology, making them up to 25% smaller than previously available microduct cables. This makes it possible to install more fibres into congested duct space and enables the use of smaller ducts for new installations, reducing installation costs and raw materials usage. New and rigorous long-term ageing testing on the Sirocco family of cables, proving expected lifetime of more than 50 years, allowing operators to calculate the life cycle analysis of their networks over an extended period.