There’s a loud public conversation on the resilience of subsea cable infrastructure for Internet transmission. This has been driven by more media reporting of disruptions, coupled with a growing intolerance of outages owing to the low-latency performance requirements associated with modern data-rich, cloud-based applications, and geographically disparate users.

But to put what we’re hearing into context: this is not a case of subsea cables being put to the test. 

They’ve long been tested. No single cable route is impervious to disruption. It’s why route diversity and multiple redundant cables and paths exist today, and continue to be built. 

This architectural logic isn’t limited to the subsea domain either - it’s the same for terrestrial transmission as well.

Both subsea and terrestrial cable routes face some similar challenges. Both can be susceptible to breakage: subsea cables by ships dragging anchors in a storm, commercial fishing, or sabotage, for example, and terrestrial cables during heavy earthmoving or excavation for underground cables, or by over-height vehicles and hazards like high winds for cables that run overhead on utility poles.

In all of these circumstances, being able to pinpoint the fault location and roll a truck (for terrestrial) or deploy a cable repair ship (for subsea) is important for restoring capacity in a timely manner. The combination of fiber sensing and end-to-end monitoring of network health is aiding that identification process and becomes more important as the amount of cable infrastructure underground, overhead, and on the seabed continues to multiply.

Just as important as fault identification is that there are alternative options, for the cable owner and users to be able to temporarily - and automatically - route around a broken fiber cable and maintain continuity of service and operations. Ideally, for users, that’s at the expense of only a few extra milliseconds to round-trip performance.

Here, subsea routes arguably display greater resilience characteristics and future potential than other transmission options.

More cables mean more route options

Subsea cable infrastructure is being deployed both for domestic and international traffic routing, with interconnectivity between the two. This is significantly increasing the number of available paths for traffic.

Australia, for example, has a subsea cable that runs around the Top End, connecting two states with branches to offshore oil & gas platforms. Another operator is building a subsea cable connecting multiple capital cities on the southern coast. These are the kind of cable systems that would previously have been laid terrestrially, particularly overland. As these domestic subsea cables interconnect with international cables, this will markedly increase the number of paths available for traffic rerouting, especially as more countries use subsea cables on domestic or transnational routes.

New cable builds on international routes also continue to grow at a rapid pace, mirroring changing demands for data and cloud, particularly in the AI era. AI infrastructure, such as GPUs, is compute-intensive. As a result, many organizations are choosing to run AI workloads as-a-service on cloud infrastructure, which can have scale, performance, and cost benefits. The only pathway to the cloud is via a network connection, and the fastest way to consistently make that connection to the cloud is via subsea fiber infrastructure.

Resilience on show

Network engineers have learned from past outages to minimize single points of aggregation or failure in their network topologies. The lesson is often to have ‘more than one’ of something as a backup to maintain resilience. This thinking, too, is creating an ever-growing mesh of undersea cables crisscrossing the globe that is increasingly fault-tolerant for connectivity and service delivery, even in the face of compounding problems. 

Two examples that demonstrate clear progress here: 

First, there were multiple cables in West Africa that were simultaneously impacted around this time last year. Microsoft, whose services were impacted, had both anticipated and planned for an incident involving multiple cables, and was able to inventively navigate a ‘perfect storm’ of cuts and equipment failures, all while maintaining uptime of customer services. This is the mesh principle at work.

A second example is that the parts of the world where redundant subsea options do not exist, and backup transmission is the domain of geostationary or low-earth orbit satellites, are shrinking. The most commonly cited example of a single path failure is that of Tonga, which had its subsea cable to the outside world severed by a volcanic eruption back in 2022, leading to severe communications problems. But only two short years later, a second cable is being deployed via a branch to an existing cable system. This investment again demonstrates the value of having multiple cables. While satellites are well applicable and sometimes preferred in some use cases, the most reliable backup to an existing fiber cable is another fiber cable.

As more cables are laid, this mesh of cables is creating much broader benefits for the connected world. This is by design. The core elements of the Internet were to be nimble and resilient. This was achieved using autonomous systems that interoperate but can also maintain continuity if one system fails. With the Internet being inherently designed for resilience, it makes sense for its underpinning infrastructure to follow these principles.

With each new cable laid, the subsea ecosystem gets progressively more resilient. That’s keeping the Internet on and data flowing, meeting the key requirements of both business goals and network operators alike.