Undersea Cables

Every time you send an email overseas or purchase a product from a foreign website, your data is likely not beaming up to a satellite – it’s racing along the ocean floor. Stretching across continents and oceans, subsea internet cables (also called submarine fiber-optic cables) form an unseen network carrying the vast majority of international internet traffic. These cables are the invisible highways of the digital world, linking nations and data centers so seamlessly that we hardly realize they exist. Yet without them, modern global trade and communication would grind to a halt. This article explores what these undersea cables are, how they work, and why they serve as the backbone of our global digital economy.

What Are Subsea Internet Cables and How Do They Work?

Subsea internet cables are bundles of optical fibers, encased in layers of insulation, steel armor, and protective coatings, that transmit data between countries under the ocean. Each fiber strand is as thin as a human hair yet can carry huge amounts of digital information as pulses of light. Lasers on one end encode data into light signals that race through these glass fibers at nearly the speed of light to receptors on the other end. For most of its length a cable is only about as thick as a garden hose, though near the shore it’s thicker with extra armor (often buried under the seabed for protection). A cross-section of a typical modern cable reveals multiple layers: a plastic polyethylene outer sheath, wound steel wires for strength, an aluminum moisture barrier, inner insulation, a copper or aluminum tube carrying power (to run amplifiers), and at the core, the optical fibers themselves surrounded by jelly for cushioning.

Because signals gradually weaken over long distances, the cable includes powered repeaters (amplifiers) at intervals (typically every 50-80 km) to boost the optical signal across thousands of kilometers of ocean. These repeaters are supplied electricity through copper wires in the cable, powered from shore stations at each end. A single cable system can span from a few dozen kilometers (for example, between neighboring countries) to over 20,000 km for trans-oceanic links. Modern cables can contain many fiber pairs; for instance, the MAREA cable across the Atlantic (completed in 2017) has 8 fiber pairs and is capable of carrying a staggering 224 terabits per second – equivalent to streaming millions of HD videos simultaneously.

Laying these cables is an engineering feat. Specialized cable-laying ships carefully deploy the cable along pre-charted routes on the seabed, avoiding coral reefs, undersea trenches, earthquake zones, and heavy ship traffic areas. Near coastlines, cables are often buried a meter or two under the seafloor to prevent damage from fishing trawlers and ship anchors. Farther out at depth, they lie directly on the ocean floor. Installing a major transoceanic cable can cost hundreds of millions of dollars and require years of planning and coordination. Typically it takes 3–4 years from project inception to completion of a new cable, plus several more years for investors to recoup costs. Each cable has an expected lifespan of about 25 years before its technology becomes outdated or maintenance costs rise (though some are extended with upgrades). After installation, these cables operate silently beneath the waves, carrying data day and night with minimal human intervention.

In short, a subsea cable is like a high-speed data pipeline connecting internet infrastructure across oceans. Light signals encoded with your emails, video calls, or bank transactions zip through these fiber strands, hop through amplifiers, and land in another continent in a fraction of a second. This physical layer of connectivity is what makes the global Internet possible.

The Global Undersea Network: Backbone of the Internet

Although invisible to users, the network of undersea cables is truly planetary in scale. As of 2025, there are over 600 active or planned submarine cables crisscrossing the world’s oceans. Combined, they span roughly 1.2–1.5 million kilometers in length – enough to circle the Earth multiple times. Virtually every country with a coastline is connected by one or more cables, and many regions have dozens of cables landing at major coastal hubs (for example, the U.K., Japan, and Singapore each host numerous international links). This dense web of fiber forms a global backbone, through which the vast majority of international data flows.

By the numbers, subsea cables carry the lion’s share of global communications:

• Over 95–99% of international internet traffic travels via undersea fiber-optic cables, not satellites. In other words, nearly all overseas emails, web pages, phone calls, and videos you send or receive go through a cable on the ocean floor. Satellites account for well under 5% of international data (for the U.S., only about 0.37% of international capacity runs over satellites) – satellites are useful for very remote areas or broadcasting to many locations, but they can’t compete with cables’ huge capacity and low cost per bit.

• There are around 1.3 to 1.5 million kilometers of submarine cables in service worldwide. To put that in perspective, that’s about three times the distance from the Earth to the Moon. Individual cable systems range from short hops (e.g. 130 km between Ireland and the U.K.) to transoceanic monsters like the Asia-America Gateway, about 20,000 km long.

• Hundreds of terabits per second of data capacity span the oceans. Newer cables boast enormous bandwidth: for example, the MAREA Atlantic cable can transmit up to 224 Tbps. Global subsea capacity is measured in petabits per second (Pbps); current cables deliver over 3 Pbps and rising. Even so, demand is surging – projections show international bandwidth needs exceeding 10+ Pbps in the coming decade as cloud computing, video streaming, and data-heavy applications grow.

• These cables underpin trillions of dollars in commerce. It’s estimated that over $10 trillion worth of financial transactions every day ride on subsea cables. In fact, a single major international bank moves about $3.9 trillion per day through these cables in the course of its business. Annual cross-border payment flows exceed $150 trillion, all made possible by instant data exchange over this infrastructure. (We’ll expand more on digital trade and finance below.)

• The submarine cable ecosystem is robust but also has critical choke points. Certain hubs like Djibouti, Singapore, and Cornwall (UK) host many cable landings, making them strategic junctions of global connectivity. Most countries rely on multiple cables for redundancy – for example, the U.S. is linked to Europe by dozens of parallel Atlantic cables – but some regions with only one or two cables remain vulnerable to outages.

This undersea network is literally the backbone of the global Internet. By carrying virtually all intercontinental data, it allows the internet to be truly worldwide. Without submarine cables, using an online service based in another country (whether it’s a website, a video stream, or a cloud database) would be extremely slow or impossible. Cables provide the high-bandwidth, low-latency connections that modern digital services require. Compared to the fiber-optic “highways” under the sea, satellites are like narrow winding roads – useful in a pinch, but far more limited in capacity and with higher latency (think satellite lag on phone calls). Subsea fiber links, on the other hand, can transmit data with nearly no delay (only a few tens of milliseconds for transatlantic distances) and at costs per byte that are magnitudes lower than satellite.

Importantly, these cables make the internet highly resilient through interconnection. Data can be rerouted across alternative cables if one path fails. Major content providers and telecom carriers have agreements to automatically divert traffic when a cut or outage occurs. This redundancy is why you rarely hear about cable breaks causing internet blackouts – the network is designed to be fault-tolerant. (There are exceptions in places with sparse connectivity, as we’ll note later.) Overall, the global mesh of undersea cables acts as an always-on, behind-the-scenes infrastructure that keeps data flowing between continents 24/7.

Growth in Subsea Cables (2000–2025)

Powering Digital Trade: E-Commerce, Finance, and Communication

Submarine cables don’t just connect computers – they connect economies and people. In the digital age, huge portions of trade and commerce depend on instant data exchange, which in turn depends on these undersea links. Here are a few ways subsea cables power digital trade and everyday online activities across borders:

• E-commerce and online business: Whenever you browse an international e-commerce site or use a cloud-based service located abroad, subsea cables are doing the heavy lifting of transferring data. For example, imagine a customer in Asia purchasing an item from a European online store: the website content, payment transaction data, and order confirmation all travel across oceans via fiber-optic cable. Global online marketplaces, from Amazon to Alibaba, rely on fast undersea connections to link buyers and sellers worldwide in real time. Cloud computing services are also highly global – a company in South America might host its website on servers in North America or Europe, accessible thanks to submarine cables. In this way, cables enable even small businesses to reach international customers and participate in the global digital economy.

• Banking and finance: High-speed cables make modern finance possible on a global scale. Banks, stock exchanges, and payment networks use undersea links to transfer funds and data securely between financial hubs. International wire transfers and credit card transactions are authorized across continents via these connections. In fact, as noted, one major bank alone averages nearly $4 trillion in daily transfers through subsea cables. Global foreign exchange trading (the FX market) and stock trading across New York, London, Tokyo, etc. depend on low-latency fiber lines to arbitrage and execute trades in milliseconds. According to industry data, more than $150 trillion in cross-border payments flow each year and are increasingly conducted online – all riding on undersea networks. Payment processors require reliable, instant connections; a slight increase in latency can have real financial costs. Undersea cables thus form the circulatory system of global finance, allowing money to move around the world at the speed of light.

• Communication and collaboration: From international phone calls to Zoom video conferences, most real-time communications between countries go through undersea cables. Voice calls (which now are often transmitted as digital data) and high-quality video streams are carried by fibers across oceans so that a team meeting with colleagues half a world away feels almost as if everyone’s in the same room. Multinational companies rely on constant data exchange between branches on different continents – sending emails, sharing files, and coordinating via enterprise software. Even personal communication, like messaging your friend abroad or posting on a social media platform hosted overseas, depends on these links. During the COVID-19 pandemic, for instance, remote work and global video conferencing surged, and undersea cables handled the massive increase in international data traffic that ensued, enabling business continuity and cross-border collaboration.

• Digital services and content delivery: Many digital services we consume cross borders without us realizing it. When you stream a movie or music, the content might be coming from a data center overseas through a transoceanic cable. Popular streaming platforms and websites use content delivery networks (CDNs) that cache data globally, but even those caches are filled and updated over submarine cable links. Likewise, cloud computing often involves storing data in one country and accessing it from another – for example, backing up files to a server in the U.S. while you’re traveling in Africa, or using an AI service hosted in Europe from your office in South America. All of this is possible only because the underlying cable infrastructure makes distance essentially irrelevant to data. Subsea cables have been credited with fueling economic growth and innovation, by dramatically increasing access to high-speed internet and lowering the cost of data connectivity worldwide. They reduce barriers to digital trade, allowing even developing regions to tap into global markets, outsource services, or become part of international supply chains.

In sum, undersea cables are the digital trade routes of the 21st century, much like shipping lanes and air cargo routes are for physical trade. Instead of carrying raw materials or finished goods, they carry information – the lifeblood of modern commerce. Virtually every cross-border online transaction, whether it’s buying a product, transferring funds, or simply exchanging emails, is facilitated by these cables. This critical role often goes unnoticed because data flows are intangible, but the impact is very real: studies have shown that better international bandwidth connectivity correlates with increased economic activity, tech investment, and job creation in connected countries. From e-commerce entrepreneurs reaching customers abroad to farmers getting market price updates via internet, the spread of global internet cables has enabled broader participation in global trade and services.

Recent Developments and New Projects in the Subsea Cable Industry

The subsea cable industry has been booming in recent years, driven by our insatiable demand for data and cloud services. Significant new investments and projects are expanding cable networks to increase capacity and reach. One major trend has been the rise of big technology companies (sometimes called “hyperscalers” in this context) as key players in building and owning cables. Traditionally, consortia of telecom companies cooperated to lay international cables, often with backing from government telecom agencies. But today, private content providers like Google, Meta (Facebook), Microsoft, and Amazon have taken a leading role.

• Tech giants’ cable expansion: Over the past decade, companies such as Google and Meta have invested heavily in their own submarine cable projects to connect their global data centers and users more efficiently. Google is an owner or partner in around 33 subsea cables, Meta in over a dozen, Microsoft in at least 5, and Amazon in at least 4. Collectively, the “Big Four” tech firms now account for around half of all undersea internet capacity worldwide. This is a remarkable jump from ten years ago, when they used less than 10% of capacity – by 2024 their share had surged to roughly 71% of utilization on major routes. The reason is simple: cloud and content companies need enormous bandwidth for services like YouTube, Netflix, cloud storage, and enterprise cloud computing. Owning cable infrastructure (or fiber pairs on cables) ensures they have the needed capacity and can lower ongoing bandwidth costs. For example, Google has funded transatlantic cables like Dunant (U.S. to France) and Grace Hopper (U.S. to UK/Spain) to bolster connectivity for its services, while Meta is leading the giant 2Africa cable project around Africa.

• New cables connecting the world: Dozens of new cable systems are in development or have recently been completed across various regions. One of the most ambitious is 2Africa, a 45,000 km cable system encircling Africa and connecting it to Europe and Asia. When fully operational (expected by 2024–2025), 2Africa will be the longest subsea cable in the world, linking 33 countries with high-speed internet and greatly increasing bandwidth for the African continent. It’s funded by a consortium including Meta (Facebook) and African and global telecom operators, and built by Alcatel Submarine Networks (a French company). Likewise, Google’s Equiano cable (connecting Portugal down the west coast of Africa) and the Peace cable (connecting Asia, Africa and Europe) are bringing more capacity to underserved regions. In Asia-Pacific, new regional cables are coming online to connect Southeast Asian nations, Australia, and the Pacific Islands with each other and with North America. For instance, cables like JGA-S and Hawaiki now link Australia/NZ to Japan and the U.S., improving transpacific routes.

• Investment surge: The industry has seen a significant surge in investment. Over the last decade, roughly $19 billion was invested in new subsea cables globally, and the pace is increasing. Annual investment in new cable projects is projected at around $5 billion per year for the next couple of years. This influx is driven by the explosion in data demand – especially traffic between data centers across oceans – and by the strategic push of internet giants to construct private infrastructure. Private equity and infrastructure funds have also entered the scene, seeing cables as a lucrative asset class. In fact, as of 2023, private investors (including tech firms and investment funds) account for an estimated 40% of new cable system deployments, indicating a shift from the old telco-dominated model to a more mixed ownership landscape.

• Regional developments: Geographically, some of the fastest growth in cable projects is in regions that had relatively limited connectivity before. Southeast Asia is a hotbed of new cables, as countries like Indonesia, the Philippines (both archipelagos) require more links internally and externally. Similarly, Latin America’s connectivity to North America and Europe has expanded (about 20% of recent new cable investment is in Latin America routes). The Middle East to South Asia routes have also seen about 15% of new cable development, improving links from the Gulf and India to Europe and East Asia. Even within regions, cables are being added to increase resiliency and lower latency – for example, new intra-Asia cables bypassing congested routes, or the first new trans-Atlantic cables in nearly two decades (like Grace Hopper) to meet rising traffic between North America and Europe.

• Technological advances: Submarine cable technology continues to improve. New cables often have 12, 16, or even 24 fiber pairs (versus older cables with 4 or 8 pairs), and they use advanced optical modulation techniques and wavelength multiplexing to vastly increase capacity per fiber. There’s also experimentation with space-division multiplexing, essentially running multiple parallel fiber modes, to push capacities further. These advancements mean that each successive generation of cables can carry exponentially more data. For example, the entire design capacity of a 2000s-era cable can now be dwarfed by a single pair on a modern cable. Such growth is crucial as global internet traffic continues to climb steeply each year.

It’s worth noting that not all planned cables come to fruition – some projects get delayed or canceled due to various issues (funding, politics, etc.). Recently, geopolitical tensions have affected a few high-profile projects. Several proposed cables that would have connected the U.S. directly to Hong Kong or other parts of Asia were put on hold or re-routed due to U.S. government security concerns about Chinese involvement. Nonetheless, alternate projects have emerged to ensure connectivity (for instance, cables connecting the U.S. to Taiwan, the Philippines, and Singapore have proceeded without contested landing points). The overall trajectory is clear: more cables, more capacity, and more direct routes are being added to knit the world even tighter together digitally. This growth is essential to support future technologies like 5G/6G networks and AI-driven services that will generate even greater data flows across borders.

Capacity of Major Subsea Cables

Challenges and Geopolitical Considerations

Despite their critical importance, subsea cables face a range of challenges and strategic concerns – from accidental damage to international disputes – that come with being the backbone of global communications:

• Physical vulnerabilities and outages: Submarine cables, while engineered for durability, can and do break. In fact, cable faults happen quite frequently – on the order of 200 faults per year worldwide, according to the International Cable Protection Committee. The vast majority of these are caused by mundane hazards: fishing trawler nets, ship anchors dragging along the seabed, undersea earthquakes or landslides, and occasionally natural wear and tear. Most cable breaks are repaired within days or weeks by dispatching cable repair ships to pull up the cable and splice the break. Because traffic can be rerouted to other cables, users often don’t notice these incidents. However, in regions with only one or two cables, a cut can be severely disruptive. A dramatic example occurred in 2017 when Somalia’s single major cable was severed by a ship’s anchor, plunging much of the country offline – the outage lasted 23 days and was estimated to cost Somalia about $10 million per day in lost economic output. Similarly, the Pacific island nation of Tonga experienced a weeks-long internet blackout in 2022 after a volcanic eruption damaged its only international cable. These incidents highlight the need for redundancy: many developing regions are now prioritizing additional cables (or satellite backups) to avoid total isolation in case of a break.

• Security and sabotage concerns: Of growing concern is the risk of deliberate damage to cables, especially in the context of military or geopolitical conflicts. Since cables are hard to physically secure – they lie in international waters and come ashore at relatively remote landing sites – there’s fear that hostile actors could tamper with or cut them. There have been isolated cases of undersea cables being tapped for espionage during the Cold War, and more recently, unexplained disruptions in northern Europe’s cables in 2023 raised suspicions of sabotage. NATO and other alliances have acknowledged this threat and begun initiatives to monitor and protect critical undersea infrastructure (for instance, deploying naval patrols and creating rapid repair teams) in response to increased Russian naval activity near cable routes. While a large-scale, intentional attack on cables has not occurred to date, the strategic importance of cables means they are now considered national security assets. Protecting these “digital arteries” from covert interference is an emerging priority in cyber-defense discussions.

• Geopolitical tug-of-war and ownership: Submarine cables have also become entangled in the broader great power competition between the U.S. and China. Chinese companies, notably HMN Tech (formerly Huawei Marine Networks), have rapidly grown their share of the cable construction market – they manufactured or laid about 18% of the world’s new cable length in the past few years. As part of China’s “Digital Silk Road” initiative, Chinese firms and state banks have been financing cables to connect Asia, Africa, and the Middle East, aiming to capture up to 60% of the global fiber-optic market. This expansion has raised alarm in Washington and other capitals, fearing that Chinese-built cables or landing station equipment could be used for spying or give Beijing leverage over international data flows. In response, the U.S. government has effectively blocked Chinese involvement in certain cable projects that land on U.S. shores or involve U.S. tech firms. For example, proposals for direct cables between California and Hong Kong were denied due to security reviews. Western-aligned countries are also investing in alternative routes (e.g. connecting through Taiwan, Japan, Philippines instead). This dynamic has made cable consortia and bidding processes something of a geopolitical chess match, with influences on which companies win contracts and where cables get routed. The end result may be a more bifurcated global network if tensions escalate – though presently, internet traffic still flows freely regardless of origin, and the goal on all sides is to avoid disrupting commerce.

• Digital sovereignty and regulatory issues: Beyond security, there’s a question of data sovereignty – countries wanting control over the data that traverses their borders. The European Union, for instance, has emphasized building secure infrastructure and keeping more data within Europe’s jurisdiction (through initiatives like GAIA-X and stricter data privacy laws). While the EU still relies on transatlantic cables for connectivity, it also pushes for diverse routes and European stakeholder ownership to reduce dependency. Meanwhile, some countries require that certain sensitive traffic (like government or defense data) use domestic or dedicated cables rather than foreign-owned ones. These political considerations can influence cable routes and landing points (for example, avoiding routes that pass through unfriendly nations’ waters, or adding landing stations in allied countries). Additionally, multiple governments impose regulations on landing rights: getting permits to land a cable can involve navigating complex bureaucracy and even local hiring requirements, which can delay projects by years. In some cases, differing regulatory regimes and concerns about foreign influence can lead to duplicated infrastructure – essentially cables built for political reasons rather than pure market demand.

• Maintenance, environment, and other challenges: Running a subsea cable network isn’t just “set and forget.” Besides repairs, operators must maintain the landing stations and deal with power supply (repeaters draw power from shore, consuming a considerable amount of electricity over a cable’s length). The industry is also grappling with environmental and permitting challenges. Some coastal areas have environmental protections that restrict where cables can land, and communities occasionally object to landing sites due to construction disruption. There is also the environmental footprint of manufacturing and installing cables (though relatively small compared to other infrastructure), and discussions on making cables more energy-efficient. Lastly, insurance and liability for cable breaks is an ongoing issue – for instance, if a ship accidentally cuts a cable, determining responsibility and compensation can be tricky under international law (treaties like UNCLOS recognize cables as critical infrastructure, but enforcement is difficult on the high seas). Industry groups like the International Cable Protection Committee work to address these issues by coordinating between cable owners, governments, and marine industries to minimize risks and ensure quick restoration when problems occur.

In navigating these challenges, many stakeholders are involved: private companies, international consortia, naval forces, policymakers, and engineers. The key is that subsea cables, though out of sight, are now firmly on the agenda for national security and economic strategy discussions. Ensuring their resilience and security has become a global priority, as any prolonged disruption would have far-reaching effects on economies and daily life. Encouragingly, the track record so far shows the cable network to be quite resilient, and cooperation usually prevails in keeping the world connected – even adversarial nations have a mutual interest in not severing the lines that their own economies depend on. Still, as data grows more critical, we can expect continued focus on strengthening this “invisible” infrastructure against both man-made and natural threats.

“Invisible” but Critical Infrastructure

It’s often said that submarine cables are the unsung heroes of the internet age – invisible to the public, yet absolutely essential. Unlike data centers with their blinking servers or cell towers dotting the landscape, undersea cables do their job in darkness and silence at the bottom of the ocean. We typically become aware of them only when something goes wrong. But as we’ve seen, these fiber-optic strands underpin everything from our daily Zoom calls to the global financial system. They truly are the invisible backbone of global digital trade and communication.

Why “invisible”? For one, they’re literally out of sight – thousands of kilometers of cable lie hidden under water, far from where any user can see. There’s no flashy presence; a cable landing station on shore might just look like an unremarkable fenced compound. The internet feels wireless and cloud-like to users, but in reality it relies on very tangible, physical connections – over 99% of international data is grounded in this undersea cable infrastructure, not satellites or magic. This paradox often surprises people. It’s a testament to how well the system works that we forget it’s even there.

Yet “critical” is not an overstatement for their importance. These cables have been described as the nerve system of the modern global economy. If they were to suddenly disappear, entire economies and societies would be shocked: international trade would be paralyzed, financial markets would falter, and communications between continents would be reduced to a trickle (only what limited satellites could support). No streaming video, no cloud apps, no instant payments – the world would feel much bigger and more isolated. In many ways, subsea cables do for data what container ships and airplanes do for goods: they allow exchanges across oceans at massive scale and relatively low cost, making our world interconnected and enabling globalization in the digital realm.

It’s also critical to understand that maintaining this infrastructure requires continuous effort and innovation. New cables must be laid to add capacity and connect underserved areas; existing cables must be repaired or upgraded; and cybersecurity measures must evolve to protect data in transit. Encouragingly, international cooperation in this arena has been strong – multiple countries and companies collaborate on cable projects, since everyone benefits from robust global connectivity. Even rival firms co-own cables, and even rival nations often agree on pragmatic steps to safeguard cables, because the alternative is mutual loss.

As we forge ahead into an era of even greater digital integration – with trends like remote work, telemedicine, e-learning, cloud computing, and AI only accelerating – the demands on undersea cables will continue to grow. More investment and strategic planning will be needed to expand this hidden network. The good news is that stakeholders recognize this: billions are being poured into new cables, and initiatives are underway to improve resiliency and oversight of undersea infrastructure.

In closing, the next time you video-chat with someone overseas, binge-watch a show produced abroad, or conduct a cross-border business deal online, take a moment to appreciate the engineering marvel beneath the ocean that makes it all possible. Those thin strands of glass under the seabed are carrying the world’s data and, with it, the world’s commerce and connections. Subsea internet cables may be invisible, but they are indisputably critical – the backbone of our global digital village. Our ability to buy, sell, communicate, and collaborate worldwide in real time depends on them. In a very real sense, these undersea cables tie the world together, driving digital trade and linking communities from shore to shore. Without them, the global internet as we know it would not exist – and neither would the thriving digital economy of today’s interconnected world.