Submarine fibre-optic cables carry the overwhelming majority of international data traffic, connecting economies, public services and everyday communications across oceans. They are largely built and operated by private consortia, but governments regulate landing points, maritime activities and national security. Cable failures can result from anchors, fishing, earthquakes and other causes. Their protection has become an important issue in international cooperation and geopolitical risk.
Key takeaways
- Submarine cables carry more than 99% of international data traffic, according to the ITU.
- Most cable systems are commercially owned or operated, with governments exercising regulatory roles.
- Fishing, anchors and natural hazards cause many cable faults.
- Redundant routes and rapid repairs are important for resilience.
- International cooperation can improve protection without giving any one country control of the whole network.
Why cables still matter in the satellite age
Most international internet traffic travels through fibre-optic cables laid on or beneath the seabed. Satellites provide valuable services, especially in remote places, but they do not replace the capacity and economics of the global cable network. The International Telecommunication Union reports that submarine cables carry more than 99 per cent of international data traffic. They support banking, research, cloud computing, messaging and many government services.
The network is easy to overlook because it is mostly invisible. Yet its geography resembles older maritime connections: long-distance routes link major economic centres, with landing stations concentrated along particular coasts. Earth Site’s guide to the Pacific Ocean’s trade and communication geography shows why ocean geography has always shaped international exchange.
How fibre-optic cables transmit information
Modern submarine cables contain optical fibres that carry information as pulses of light. Repeaters along long routes amplify or regenerate signals as needed, while protective layers shield the fibres from mechanical damage. Cables are engineered for deep-water pressure and harsh conditions, but they remain vulnerable near shore and in areas of intensive human activity.
A cable does not carry a single website or country’s messages in isolation. Telecommunications companies route data across interconnected networks, and traffic may switch paths when equipment fails. This flexibility is a major strength, but it depends on sufficient alternative capacity and functioning connections at both ends.
Who owns and operates submarine cables?
Many systems are financed by groups of telecommunications companies, technology firms and investors. Some are owned by a single operator or involve state participation. The owner is not necessarily the organisation that maintains every segment or controls the wider internet. Cable systems connect with terrestrial networks and data centres, creating a chain of responsibilities.
Governments regulate landing permissions, environmental requirements, security and telecommunications services within their jurisdictions. On the high seas, international law shapes rights and obligations related to laying and protecting cables. No single global authority owns all cables or decides how all internet traffic should move. This mixture of private investment and public regulation makes governance complicated.
Why routes follow particular geography
Cable planners balance distance, seabed conditions, landing sites, political risk and the cost of repairs. A shorter route may cross difficult terrain or a busy shipping area. A longer route may offer better resilience by avoiding a narrow chokepoint. Continental shelves, deep ocean basins, earthquakes and submarine landslides all influence design decisions.
The distinction between a sea, strait and ocean is useful when examining route maps. Earth Site’s seas, straits and other bodies of water provides the geographical vocabulary. Routes through narrow seas can concentrate risk because many cables may pass through a limited corridor, but cables also need access to ports and infrastructure where repairs can be organised.
What causes cable failures?
Accidental damage from fishing gear and ship anchors is a major cause of submarine cable faults. Earthquakes, underwater landslides, strong currents and equipment problems also create risks. The ITU has reported roughly 150–200 faults worldwide in a typical year, although counts vary with the period and definitions used. Most faults are not evidence of sabotage.
When a cable fails, network operators identify the affected segment and attempt to reroute traffic. A specialised repair ship may retrieve and replace damaged sections. Weather, permits, vessel availability and the depth of the fault influence repair time. The effects on users depend on how many alternative routes remain available.
Why some countries are more vulnerable
Large economies often connect through several independent cables and terrestrial networks. Some islands and smaller states have fewer international connections. If a country relies heavily on one or two routes, a single fault may cause severe disruption to communications, financial transactions and public services. The same physical event can therefore have very different consequences in different places.
Redundancy means providing alternative routes that do not all share the same vulnerable point. Building a second cable along exactly the same path may increase capacity without offering full protection against a local earthquake or anchor incident. Route diversity and cooperation between operators are important components of resilience.
Submarine cables and geopolitics
Cables are critical infrastructure because communication supports both civilian life and national security. Governments may be concerned about espionage, deliberate damage, foreign ownership or dependence on particular landing points. These concerns are legitimate subjects for policy, but allegations of intentional interference require evidence. A fault caused by fishing gear should not automatically be described as an attack.
Historical comparisons can be instructive. Earth Site’s account of the historical importance of maritime chokepoints shows how maritime chokepoints influenced trade and state power long before the internet. The analogy has limits: digital data can be rerouted more quickly than a cargo ship, and the legal and technical arrangements are different. Nevertheless, concentrated routes can create strategic vulnerabilities.
What international law says
The law of the sea provides a framework for laying and maintaining cables, while coastal states exercise rights in maritime zones subject to international rules. Domestic licensing and security laws also affect cable landings. Because a cable may cross several jurisdictions, operators need to coordinate permits, environmental assessments and repairs across borders.
There is no simple worldwide police force for undersea infrastructure. Cooperation between governments, regulators, cable owners and specialist organisations is therefore essential. The legal position can depend on where a cable lies, what activity caused damage and which states or companies are involved. Students should avoid treating every part of the ocean as if the same national law applies.
The ITU and recent resilience initiatives
The International Telecommunication Union and the International Cable Protection Committee established an International Advisory Body for Submarine Cable Resilience in 2024. International meetings in Abuja in February 2025 and Porto in February 2026 brought together governments and industry representatives to discuss practical protection, faster repairs and route diversity. These are cooperative efforts rather than a transfer of cable ownership to the United Nations.
The ITU’s 2026 communications emphasised shared responsibility across the cable system. This approach recognises that a repair delay in one jurisdiction can affect users far beyond its borders. Resilience requires cooperation before faults occur, including arrangements for ships, permits and emergency communications.
Can satellites provide a complete backup?
Satellites can restore some connectivity during emergencies and are especially valuable for remote communities. However, their capacity, latency, equipment requirements and operating costs differ from submarine fibre systems. A country might use satellite links for essential services while still experiencing serious disruption to high-volume international data exchange.
Effective contingency planning may combine satellites, terrestrial cross-border links, additional cable routes and local data infrastructure. The best mix depends on geography and economic resources. Technology choices should be evaluated against realistic traffic requirements rather than presented as a competition in which one medium must replace every other.
Environmental considerations
Cable installation can disturb parts of the seabed, particularly near coasts where burial and shore crossings are required. Environmental assessment considers sensitive habitats, fishing activity and protected areas. In deep water, cables often rest on the seabed and may have relatively limited physical footprints compared with larger infrastructure, although local conditions matter.
Repair operations can also affect marine activities and require coordination with fishing fleets. Good planning tries to reduce conflicts and protect ecosystems while maintaining connectivity. The challenge is to balance essential communications with responsible management of ocean space.
How to evaluate a cable-security headline
When a report describes a damaged cable, ask where the fault occurred, whether its cause has been independently established and how much traffic was affected. Distinguish an outage from a complete national internet shutdown. A single system may fail while alternative cables continue operating. The words sabotage, accident and suspected interference have different evidential meanings.
Students can compare a cable map with tectonic boundaries and shipping routes, then consider which risks are physical and which are political. They should also ask who supplied the information: a government, operator, independent investigator or anonymous commentator. Careful sourcing prevents dramatic claims from replacing evidence.
What happens during a cable repair
When monitoring systems identify a fault, operators estimate its location and decide whether traffic must be rerouted. A specialised ship may travel to the site, retrieve the damaged cable using appropriate equipment, remove the faulty section and join in a replacement. The repaired cable is then tested and returned to service. Deep-water operations can be technically demanding, while shallow-water work may face shipping and fishing hazards.
The repair timeline depends on vessel availability, weather, permits and the precise location. A fault is not necessarily a total outage for every user, because network operators may divert traffic. Understanding the repair process helps explain why resilience depends on both engineering and international cooperation.
Landing stations as critical infrastructure
A cable reaches the land at a landing station where its optical signals connect to terrestrial networks. These facilities require reliable power, physical security, maintenance and connections to inland data centres. Concentrating many cables at one landing site can reduce costs but also create a shared point of vulnerability.
Governments and operators therefore consider geographic diversity, flood risk, coastal erosion and security when planning new connections. A country may have several cables yet remain exposed if they converge on the same narrow coastal corridor. Resilience planning should examine the complete route from seabed to inland network, not only the number of cables shown on a map.
Practical policy options for resilient connectivity
Governments can improve resilience by streamlining emergency repair permissions, coordinating with fishing and shipping authorities and encouraging diverse routes. They may also support additional connections for remote islands or require operators to maintain contingency plans. These policies involve costs and trade-offs, so they should be assessed against the likely consequences of outages.
International cooperation is particularly important because cables cross several maritime zones. A repair ship may need to enter different jurisdictions and work around busy sea lanes. Transparent procedures and established contacts can reduce delays during emergencies. Stronger connectivity is therefore partly a governance achievement, not merely a matter of laying more fibre.
Conclusion
Submarine cables connect the modern world through physical routes shaped by geography, engineering and international cooperation. Their importance does not mean every fault is deliberate or that one organisation controls the entire network. Resilient communications require diverse routes, effective repairs, sound regulation and careful evidence when security incidents are reported.
Frequently asked questions
Do satellites carry most international internet traffic?
No. Submarine fibre-optic cables carry the overwhelming majority of international data traffic.
Who owns the cables?
Ownership varies, often involving telecommunications companies, technology firms and consortia.
What damages undersea cables most often?
Fishing gear, anchors and natural events are major causes; deliberate interference is not established for every fault.
Who repairs them?
Specialist ships and contractors work with cable operators and relevant authorities.
Why are cables a geopolitical issue?
They are critical infrastructure crossing borders and maritime zones, creating shared security and resilience concerns.
