Monday, 27th September 2021
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How Aerial Cable Deployment can drive broadband expansion

By Tobias Schubert, Marketing; Major Accounts; EMEA, Carrier Networks, Corning Optical Communications.

5G will fundamentally change the telecommunications world on a global scale. While most phones don’t currently support 5G and we’re yet to see any nationwide offerings yet, network operators across Europe are working to ensure that infrastructure is ready for 5G when it reaches maturity. The demand for faster connections is growing not only in the industry but also among the public.

The reason for the increasing demand for fibre optic connections is the growing need for bandwidth as more and more devices are connected to the Internet. This has proliferated even further in the wake of the COVID-19 pandemic which has seen businesses across the world transition to working from home. It is now equally important for home connections to be as fast and resilient as those in the office and these flexible working models are expected to be retained in future. Meeting this demand, requires fibre optic connections to the building and into the home or the apartment as they have a technically almost unlimited transmission capacity.

While the copper to fibre transition in the UK is still in its relatively early stages – only around 14% of the population have access currently – progress is being made. The UK is among the countries with the highest growth rates in the FTTH Council Europe’s recent Panorama report and UK Prime Minister Boris Johnson has stated his goal for 85% coverage of fibre-optic broadband by 2025.

At the same time, telecommunications companies are preparing for 5G. As the demand for bandwidth and lower latencies grows, the infrastructure must be adapted. Copper cables are being complemented or replaced by fibre optical cables, because copper will no longer be able to meet these increased requirements in the future.

So the question is: how do you get fibre to people quickly and cost-effectively, no matter where they are?

Why we need aerial deployment

Rural and remote areas are a challenge for the deployment of fibre optic cables: the distances are long and underground installation to the end customer via fibre to the home (FTTH) networks is a major cost factor and very time-consuming. Aerial fibre optic installation offers an alternative installation method for the fast and cost-effective deployment of FTTH connections in the process of broadband expansion. It is considered if underground installation is not possible or very expensive (such as in mountainous regions), or if an infrastructure (poles or power towers) already exists. This method is also suitable for temporary applications, to bridge the time before the next planned road upgrade when a cable can be moved underground more economically for example.

About 80–90% of the total costs to build fibre networks corresponds to underground deployment. As the approval and deployment processes are very complex it is a fairly unprofitable and time-consuming method. In addition, the underground fibre-optic construction requires specialists who are increasingly scarce on the labour market.

Aerial cables are also usually installed on existing infrastructure, such as wooden poles – a constantly growing infrastructure that can be leveraged for the installation of fibre optic cables, thus massively reducing costs compared to underground cabling.

Corning has already deployed aerial cables in Australia, Canada, Spain, the UK and the US among other countries. The specially protected OptiTap® and OptiTip® hardened connectors were

developed for use in outdoor installations. This enables us to help our customers worldwide to complete FTTH projects within a shorter timeframe and to meet ambitious schedules. The connectors are easy to plug in and eliminate the need for time-consuming splicing on site. All components of the plug-and-play system are resistant to environmental influences and tested for immersion in water, tension, shearing/bending, torsion, vibration, temperature changes and external pressure.

It’s all about the right cable design

When deciding which type of cable is right for your application, several factors need to be considered: the desired bandwidth for end customers, how easily network expansion or repairs can be carried out, the necessary certification requirements for installers and the ability to expand the network over time.

We generally choose from two basic network designs:

· Point-to-point deployment on dedicated routes, typically for long distance connections between urban and rural areas with very distant fibre access points

· Point-to-multipoint fibre optic installation in dense urban and suburban environments with multiple fibre access points

It is important to consider all components and the existing infrastructure when planning a network. In practice, we often see mixed forms of aerial and underground networks. For some projects, the operators decide to bury the cables in the backbone area and lay the last mile to the customer aerially. Others install the backbone infrastructure on poles and bridge the last mile underground.

Terminals or street cabinets need to ensure that the cables can be used independently from each other, whether they are aerial or underground cables, to support capacity for future upgrades, additions or changes and make the networks future-proof.

The different cable types

There are three types of air cable designs commonly deployed: full-dielectric self-supporting cables (ADSS), Figure 8 aerial cables and standard outside plant cables (OSP). Before deciding which cable best suits your needs, you should take a closer look at their specific designs and characteristics.

ADSS

ADSS cables, like the Corning SOLO® ADSS, are commonly used in Spain, Portugal, Poland, Germany and Romania among other European locations. They are suitable for point-to-point connections over long distances in rural areas or for inter-city links. The choice depends on various factors: span between poles, sag and environmental influences, such as wind or ice loads on the cable throughout its lifetime.

ADSS cables do not require any additional supporting lines (messengers) and are therefore suitable for installation in the vicinity of high-voltage lines up to 12kV in accordance with IEEE 1222 guidelines. This allows for installation in existing power lines and reduces costs. As the cables are metal-free, they do not require grounding. This makes installation easier and keeps costs down.

However, not all ADSS cables are the same: for a long service life without negative effects on the optical transmission performance, ADSS cables must be manufactured using aramid yarns. When temperatures rise in summer, plastic components in the cables tend to expand. Aramid yarn, on the other hand, contracts inside the cable construction, reducing cable sag in summer.

Figure-8 cables

When installing aerial cables on wooden telecommunication poles without any electrical line nearby, Figure-8 self-supporting cables are an alternative solution to ADSS cables. Figure-8 cables are manufactured by incorporating an additional steel wire into the cable sheath. It then carries the load of the fibre optic cable when it is installed between poles and prevents an increase in attenuation throughout the life of the cable. Figure-8 cables can be installed with a span of up to 80 meters and require fewer accessories for mounting on the poles compared to ADSS cables. This allows installation costs to be reduced if there are no electrical potentials affecting the optical cable. However, the problem of lightning strikes in the steel wire still persists and must be considered.

OSP

OSP cables like SST-Ribbon™ cables are perfect for point-to-multipoint applications in an urban or suburban area. OSP cables are available with armoring or full dielectric construction and can be tied to existing cables or steel messengers. This type of installation is generally preferred when a high fibre count connection is required. The steel messenger is used to support the weight of the fibre optic cable and to withstand weather conditions, thus reducing the load on the optical fibres.

However, despite all the advantages, there are also some challenges that must be taken into account when considering an OSP deployment. If an OSP cable cannot simply be attached to existing cables, the need for a new steel messenger could lead to additional costs. It is also necessary to check that the load capacity of the poles is not exceeded by the new cables. Steel messengers and armoured aerial cables also require grounding, which can also lead to additional investments. OSP cables are rarely used as an aerial cable solution in Europe.

Aerial deployment in the UK

Aerial cable installation in the UK is particularly challenging as there are strict recommendations and rules regarding cables that can be installed aerially across road crossings. The main issues are around minimum sag allowed, but mainly pole loading. The aim is to eliminate the chance of a vehicle strike bringing the pole and all the remaining infrastructure along the route down.

To this end most operators insist on a cable tensile limit. This ensures that the cable acts as a “fuse” that will safely break should it be struck by a vehicle or any other potential obstacle such as trees. This makes the design of aerial optical cables even more of a challenge in balancing the span, mechanical and environmental considerations against the fibre and tensile limit requirements – this often leads to some novel concepts and designs.

Conclusion

5G is coming and the broadband roll-out is progressing steadily, but for Governments across Europe to achieve their ambitious goals, alternative installation methods must be considered.

In the UK, underground installation will of course play a key role in delivering the Government’s ambitious rollout targets but the deployment of aerial cables will also be essential in reaching remote and rural areas and also for temporary network connections. This way, customers can be provided with fast Internet until the cables can be laid underground at a lower cost. Aerial cables are relatively easy to install and the infrastructure already exists in many places. Thus, the use of aerial cables speeds up the expansion process at a fraction of the cost.

Cable types, existing infrastructure and components as well as future requirements and expected costs play a role in the choice of installation method. Aerial cabling can play a major role in building a future-proof network in the UK, supporting its economic recovery, and supplying all customers with fibre connections, no matter where they are.

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