Article Categories: News, Cables,

Monitoring Subsea Telecoms Cables in a Connectivity Hungry World

We live in a world driven by a thirst for ever faster connectivity. The responsibility for monitoring and maintaining cables to protect telecoms uptime, meet customer expectations, and avoid business-critical outages weighs heavy on telecoms providers. And no wonder…as this new submarine cable map shows, more than 1.3 million kilometres of subsea cables span the globe, whilst the next three years look set to see a further $8 billion of investment into further cable infrastructure worldwide.

What’s more, our seemingly limitless demand for always-on data is changing the face of offshore cable infrastructure. Whilst, in 2012, telecoms accounted for around 10% of the global subsea cable network share, by 2020 we saw that share surge to 66%. The biggest players – Google, Facebook, Microsoft etc – are playing a key role in this shift. As an example, Google and Facebook plan to boost APAC Connectivity with Project Apricot, which will link six APAC countries with more than 12,000 kilometres of new subsea cable lines by 2024. This is complemented by Facebook’s investment into Echo and Bifrost – two new subsea cables that will connect Singapore, Indonesia and the US, promising a 70% increase in overall transpacific cable capacity offshore.

These and other major project investments represent a business boom for telecoms giants – but, of course, with that opportunity comes business-critical risk. Maintaining uptime is a crucial consideration to guarantee ever faster services to a global population. Indeed, according to The International Cable Protection Committee, interruptions to underwater fibre optic telecoms systems can cost operators as much as $1.5 million every hour.

Why are Offshore Telecoms Cables So Difficult to Monitor and Repair?

The subsea environment is a hostile and hard to reach terrain, plus it is constantly changing as a result of both our changing climate and natural shifts in undersea geography. Just as pipeline monitoring in remote environments presents considerable difficulties, so subsea cable monitoring has its own challenges. Traditional monitoring strategies, such as ROV (remotely operated vehicle) passes, and bathometric surveys, can miss potential problems. Clearly, attempting to manually monitor vast lengths of subsea cables involves unrealistic levels of time and resources. Plus, when a fault is detected and eventually located, repairs are difficult and potentially dangerous to undertake.

Increasingly, customers around the globe are turning to evolving technology to solve the problem. Thanks to the power of modern distributed acoustic sensing, the fibre optics that run our connectivity can also become the very sensor by which cable faults, breakdowns and damage can be more efficiently detected, analysed and repaired.

How does DAS technology monitor subsea cable faults?

Often, DAS (Distributed Acoustic Sensing) technology is deployed to a cable to monitor not the cable itself, but an asset running alongside, such as a pipeline, perimeter, or border. In the case of telecoms, the operational principles of DAS are the same, but the acoustic signatures can be used to monitor and detect events affecting the fibre optic, warning telecoms operators of problems as they occur.

Once the DAS interrogator is connected, it sends pulses of light along the length of the cable at a rate of thousands of pulses every second. Rayleigh Backscatter then reflects a proportion of that light back along the cable to the interrogator. As different events occur (for example, a marine vessel threatening anchor drag damage, a subsea cable becoming unburied, or a fault occurring within the cable itself) the pattern of the acoustic vibrations is disturbed.

This has game-changing implications when it comes to offshore cable monitoring. It enables early warning of potentially compromising events along the length of the cable. It provides valuable intelligence as to the nature of the event, so that repairs can be accurately deployed, warnings can be issued to nearby marine vessels, and so on. Repair teams can act in a far quicker time scale, reducing the risk associated with underwater cable repairs.

DAS also mitigates the risk of unnecessary cost and time spent inspecting the wrong location, or pre-assessing the nature of the damage before a repair can be planned. And, with the right additional modular technology, it enables subsea cable operators to gather, record and revisit fibre optic acoustic data over time, so that an informed understanding of historical event patterns can input into future subsea cable monitoring strategies.

Repairing Telecoms Cable Issues without Causing Further Damage

Another key benefit of applying DAS to cable monitoring and maintenance is a reduction in the need for multiple diagnostic flashover tests. Used by engineers to discover the exact location of a cable fault, flashover tests create a clear, high amplitude acoustic signal that indicates where the fault has occurred. However, flashovers can also cause a serious risk of secondary damage to an already compromised cable.

Whilst flashovers are commonly applied to power cables, multiple flashovers can present an equal risk to fibre optic cables, since they are often co-located and vulnerable to the same secondary damage. Similarly, flashover tests risk causing damage to onshore and offshore cables alike.

As an onshore case study example, Fotech’s Helios DAS® monitoring platform was used to investigate a fault in a 150kV underground cable running between two electrical power substations. The resulting data was so specific that it equipped repair teams to identify the exact location of suspected cable damage with only a single flashover test. The result was a fast, effective repair with minimal risk and cost. The application of DAS to this cable repair therefore minimised not only the risk of secondary damage, but also the risk of a safety incident, as well as significant cost, time and manpower that is typically incurred by traditional cable monitoring methods.

Meanwhile, in a live offshore environment for a Fotech client, Helios DAS® was able to pinpoint the location of the subsea cable fault to less than a metre. As a result, the operator was able to reduce the cable cutting and repair site to just 3.5 metres. Localising the repair in this way reduced the cost, risk and downtime that would be associated with a more traditional cable fault detection method, ultimately saving the client millions of pounds in lost productivity, repair, and downtime.

You can download the subsea cable fault case study here.

More Resources on Subsea Cable Monitoring

For more resources and information on subsea cable monitoring for both power and telecoms companies, visit the Fotech resource section. Or, for more information on Fotech’s modular onshore and offshore cable monitoring systems with DAS, you can contact one of Fotech’s offices in your region.

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