Amazon’s Fastnet subsea cable uses heavy armoring to keep AI and cloud traffic online

Amazon Web Services is building a new transatlantic subsea cable system called Fastnet, connecting County Cork in Ireland to Maryland on the US east coast. The system is designed for more than 320 terabits per second of capacity and uses extra physical armoring in nearshore segments to reduce the risk of accidental cuts and outages.

What Amazon is building with Fastnet

Fastnet is a private AWS-owned transatlantic cable that will land near Castlefreke in West Cork and in Maryland, with commercial service targeted for 2028. Amazon describes it as part of the next generation of global infrastructure for AI and cloud workloads, delivering secure long-term capacity and bandwidth that can be scaled as demand grows.

Key points from Amazon’s own description and regional reporting include:

A direct path between Ireland and the US East Coast, with landings in County Cork and Maryland.
Aggregate design capacity of more than 320 terabits per second, enough to support millions of simultaneous HD or AI application streams.
A role as both a primary route and a backup path if other cables in the region experience problems, improving overall resilience for AWS customers in Europe and North America.
Dedicated community benefit funds for Maryland and West Cork that will support local projects around sustainability, education, and economic development.

For Ireland, the Taoiseach has already positioned Fastnet as a vote of confidence in the country’s digital future and as a step toward making Ireland a gateway for European submarine cables. For Maryland, state officials are framing the landing as an anchor for data center and high-tech investment.

How Fastnet is armored to resist cuts

Most submarine cables already use different constructions along their length. Deep ocean segments are relatively thin, roughly the size of a garden hose, while shallow water segments near shore can be more than twice as thick due to additional armoring and sometimes burial in the seabed. The extra steel and protective layers are there to deal with anchors, fishing gear, and other human activity in busy coastal waters.

Amazon’s description of Fastnet goes further than the usual generic wording. The company highlights:

Robust cable armoring as a design goal, with shoreward sections built with heavier construction.
Additional layers of protective steel wires in nearshore areas, explicitly meant to protect against both natural and human activity.
An emphasis on keeping services running even if other regional cables encounter issues, which implies conservative mechanical design and route planning.

In practice, this means the cable cross-section and installation method will change along the route. In shallow water near Ireland and Maryland, the cable is likely to be both armored and buried below the seabed using plows or remotely operated vehicles. In deep water, where risks from anchors and trawling are much lower, the cable can use lighter armoring or no armoring at all and rest directly on the seabed.

The goal is to reduce the frequency of faults in exactly the parts of the system that are usually most vulnerable. Industry data show that most accidental cuts happen in coastal zones, often due to fishing or anchoring rather than exotic sabotage. Extra armoring and burial directly target those threats.

Why is armoring getting more attention now

AWS is not operating in a vacuum. Over the last few years, several incidents have pushed submarine cable resilience onto the political agenda.

Cables in the Red Sea and Baltic regions have suffered suspected sabotage and accidental damage, leading to slowdowns and rerouted traffic.
US lawmakers have pressed major tech firms, including Amazon, for more information on how they secure and monitor the subsea systems they fund or operate.
Strategic reports from think tanks and analysts highlight subsea cables as a critical but vulnerable part of the global internet, carrying more than 95 percent of intercontinental traffic.

Against that backdrop, Amazon’s choice to lead with “robust armoring” in its Fastnet communications is as much about narrative as it is about engineering. Extra steel wires and burial do not make a cable immune to damage, but they do help when cables share sea space with fishing fleets and shipping lanes. They also give governments and regulators a clearer story about proactive risk management.

How Fastnet fits into AWS’s global network

AWS already operates a large global fiber network, combining terrestrial links with subsea systems to connect 30+ regions and more than 100 Availability Zones. Amazon says its network now spans over 9 million kilometers of fiber, with multiple paths and automated management for rerouting traffic when faults occur.

Fastnet slots into that architecture as:

A high-capacity path between two major cloud regions, tuned for AI training clusters, analytics workloads, and latency-sensitive applications.
A source of path diversity that reduces dependence on existing high traffic routes and chokepoints in the North Atlantic.
A way to localise traffic for European customers that rely heavily on AWS but still need transatlantic connectivity for replication, backup, and multi-region deployment.

From a network design perspective, Fastnet allows AWS to keep more traffic on its own infrastructure for a larger percentage of the journey between data centers, instead of relying on third-party transit providers. That can simplify performance tuning and capacity planning, especially for predictable, high-volume services like AI model training and large-scale content delivery.

Resilience and fault scenarios

Subsea cable owners plan for faults as a matter of routine. Each system is expected to experience periodic issues over a 25-year design life, from accidental cuts to amplifier failures. What matters in practice is how often faults occur, how quickly they are located and repaired, and how easily traffic can be rerouted while repairs are underway.

Fastnet contributes to resilience in several ways:

Physical hardening in high-risk zones reduces the likelihood of shallow water cuts that would take a span out of service.
Additional transatlantic path diversity means that if another cable in the region fails, AWS can shift more traffic onto Fastnet and other routes to keep customer workloads running.
Integration with AWS traffic engineering lets Amazon move flows dynamically between cables and terrestrial routes, keeping latency and loss within bounds even when capacity is temporarily reduced.

None of this removes the need for classic subsea repair processes. Specialized cable ships will still be required to locate and fix faults, and repairs can still take days or weeks in bad conditions. What changes is the probability and impact profile of those events when the cable itself is physically more robust and the surrounding network has more options.

Why Ireland and Maryland matter as landing points

Landing locations for subsea cables are chosen partly for geography and partly for regulatory and commercial reasons.

In the case of Fastnet:

County Cork already serves as a landing region for several transatlantic cables and sits close to major Irish and European backbone routes. It gives AWS a direct path into the Irish cluster of data centers that serve both domestic and European customers.
Maryland is close to major East Coast population centers and existing AWS regions, while offering coastal geography that works for shore landings and cable protection.

By choosing a direct Cork, Maryland, route, Amazon can avoid some of the busiest chokepoints in the subsea network and reduce the number of intermediate systems that traffic has to cross. That reduces risk and simplifies capacity planning for high-growth workloads, especially AI-centric services that move large volumes of data between training clusters and storage.

Environmental and local impact

Subsea cables generally have a small physical footprint compared to pipelines or offshore energy infrastructure. When properly installed, they tend to become part of the seabed and can even act as artificial reefs in some areas. The main environmental concerns are around shore landings, burial operations, and interactions with other marine activities.

Amazon’s public information on Fastnet references community benefit funds and engagement with local stakeholders in both Cork and Maryland. In practice, that usually includes:

Consultation on landing station siting and access routes.
Coordination with fishing groups and shipping interests to map cable protection zones.
Environmental assessments for coastal works and nearshore burial.

Heavier armoring itself has a limited environmental impact, since it simply changes the mechanical design of the cable rather than how it is deployed. The buried, armored segments are intended to reduce future seabed disturbance by lowering the risk of repeat repair operations in busy coastal waters.

What to watch as Fastnet progresses

Between now and the 2028 target, several milestones will show how the project is progressing and how Amazon intends to operate it:

Final route survey and permitting for the Cork and Maryland landings, including published maps of cable protection zones.
Construction reports and updates from the cable manufacturer and laying vessel operators that confirm cable design details and armoring schemes.
AWS regional announcements about how Fastnet capacity will be exposed to customers, for example, through dedicated connectivity products, private backbone features, or new region pairings.
Any follow-on cables that mirror Fastnet’s design would suggest that heavy nearshore armoring and similar resilience features are becoming a standard pattern for AWS-owned systems.

If Fastnet performs well and the region avoids major outages, it will add weight to the argument that more aggressive armoring and route planning should be standard for new hyperscaler-owned cables.

Editor’s take

Amazon’s Fastnet cable is not the first heavily armored subsea system in the world, but it is a clear example of how hyperscalers are tuning physical infrastructure for AI era risk models. The interesting part is not just the raw capacity figure, but the explicit focus on nearshore armoring and resilience in the way AWS is framing the project.

From a technical point of view, extra steel in shallow water is an obvious step, and cable operators have been doing it for years. From a strategic point of view, stating that choice up front signals to regulators and customers that AWS is taking cable cuts and sabotage risks seriously. Given how much of the world’s AI and cloud activity now depends on a handful of transoceanic routes, that is a story Amazon needs to be able to tell.