Undersea cable (submarine communications and power cables)

Structure and components

Communication cables typically include one or more optical fibre cores surrounded by multiple protective layers: waterblocking materials, dielectric insulators, metallic strength members or copper conductors for power-feeding, and outer armouring in shallow, high-risk areas. Power cables are built around conductors and heavy insulation and often use high-voltage direct current (HVDC) technology for long runs because AC transmission suffers large reactive losses undersea. Communication systems also incorporate repeaters or optical amplifiers and land-based power-feeding equipment to maintain signal strength.

History and development

Undersea telegraphy began in the 19th century with experimental and then permanent transoceanic telegraph cables; the first widely successful transatlantic telegraph link was completed in the 1860s. Over the 20th century copper and coaxial systems carried voice and data; from the late 20th century onward optical fibre cables became dominant, vastly increasing capacity and reducing latency compared with satellite links.

Installation and maintenance

Laying a submarine cable requires specialized cable ships, route surveys, and often seabed preparation such as ploughing or burial in shallow waters to reduce risk. Branching units allow multiple landings from a single trunk. When faults occur, ships recover the damaged section for repair or use remotely operated vehicles and divers; international coordination and local permissions are routinely required.

Uses, importance and examples

Undersea cables carry the vast majority of international internet and voice traffic and are critical to global finance, research, and communications. Power interconnectors link island grids or countries to share generation and improve resilience. Their role is complementary to satellites: cables provide much higher bandwidth and lower latency for most commercial and scientific uses. For technical background see technical overview and installation guidance at marine laying methods.

Vulnerabilities, protection and governance

Cables are exposed to accidental damage from fishing gear and anchors, natural hazards such as earthquakes and underwater landslides, and rare cases of deliberate tampering. To mitigate risk, cables are armored, buried in shallow waters, routed away from hazards, and monitored; repairs are handled by specialist fleets. Ownership and operation are often by international consortia or governments, and legal frameworks govern landing points and rights of way. For distinctions between power and communications technology consult power cable design and telecommunications cable technology, and for transmission mode choices see discussions of direct current and alternating current.

• Common landing and routing practices: waterway and coastal routing
• Typical maintenance operations: coordinated ship recovery and repair
• Notable historical milestone: early transoceanic telegraph cables of the 19th century