UNDERSEA CABLESSubsea Communications Cables: Vital but Vulnerable

By Jocelinn Kang

Published 9 October 2024

Ensuring the resilience of the submarine cable network against disruptions is crucial. Lying deep on the ocean floor, these fiber-optic cables can transmit massive amounts of data at high speeds with low latency, making them far more efficient than satellites, which handle only a fraction of global data transmission. 

Most people never think of undersea communications cables.

Well, the people of Tasmania were thinking of them in 2022, when the state’s two main subsea cables were both severed within hours of each other. The disruption caused widespread outages, affecting flight schedules, cash machines and payment systems, even forcing some businesses to close.

Ensuring the resilience of the submarine cable network against disruptions is crucial.

Lying deep on the ocean floor, these fiber-optic cables can transmit massive amounts of data at high speeds with low latency, making them far more efficient than satellites, which handle only a fraction of global data transmission.  Satellites, however, do serve as backups to subsea cables in some cases and are well suited to serving remote areas, islands and mountainous regions where cable connectivity may be too difficult and expensive to install.

For most of their lengths, deep underwater, these cables are about as thick as garden hoses, with thin glass fibers at their cores to transmit data. Closer to shore, they become thicker and are reinforced with metal armor to prevent damage. Contrary to Youtube lore, marine life, such as sharks, pose minimal threat to them, thanks to improved cable designs and burial in shallow waters. The latest analysis by the International Cable Protection Committee registered no cable faults attributed to sharks between 2008 and 2014.

The biggest threats to subsea cables come from human activities. Data from 2007 to 2018 shows that anchors and fishing account for more than three-quarters of known cable faults. The damage occurs as anchors are dragged across the ocean floor or when bottom trawling fishing equipment entangles the cables. Although this is usually accidental, it could be done intentionally. Proving intention can be quite challenging.

Redundancy is a crucial part of subsea cable network resilience. If a cable is severed, redundancy enables the network to reroute the data across other links, such as other submarine cables, terrestrial cables or satellites. This minimizes noticeable impact to network connectivity.

Other methods of minimizing cable disruptions include preventing damage with protective measures. Physical security measures, such as making cables with armor and burying cables in shallower areas, reduce the risk of damage. Limiting access to cable landing stations, where cables come ashore and are more vulnerable, is another priority, because those points are on land and therefore accessible and because cables are concentrated at them.

Cybersecurity of the software that manages the cable network, and auxiliary systems, such as security camera networks protecting cable landing stations, and network operation centers, is equally essential.

Even with such measures, disruptions do happen, so having a repair capability is vital. Repair ships are crucial for restoring connectivity. But there are only around 70 cable ships worldwide, and only a third are set up repairs. The fleet and workforce are ageing, too. All this presents a significant challenge in maintaining cable system resilience.

In a recent report, Connecting the Indo-Pacific: the future of subsea cables and opportunities for Australia, my co-author and I highlighted the growing influence of hyperscale cloud and content providers on the industry and the broader geostrategic context of subsea communications cables for Australia, shedding light on the opportunities and challenges that lie ahead. Australia’s subsea cable resilience is generally good. This is because of several factors, including that multiple cables land at different geographic locations and offer a degree of redundancy and resilience. Another is that Australia’s enforces legislation to protect cables in the shallow waters as they make landfall, designating certain areas as cable protection zones.

However, challenges persist. The cable repair industry is the most significant gap in resilience.

Subsea cables are the backbone of our global communication system. As the economic and security value of data continues to grow, it’s crucial that we protect this critical infrastructure by enhancing physical and cybersecurity measures and invest in improving repair capabilities.

Jocelinn Kang is a program manager and technical specialist at ASPI. This article draws from her recent discussion on ASPI’s podcast, Stop the World. The episode can be found on ASPI’s websiteYoutube and Spotify.