A fiber-optic cable laid across an ocean or sea floor connecting continents or islands, using DWDM to maximize usable capacity per fiber pair, terminating at coastal landing stations that connect onward into terrestrial networks.

Key Points

Carries the large majority of intercontinental internet and telecommunications traffic by volume, making submarine cable capacity and route diversity a foundational consideration for global connectivity resilience
Uses DWDM to multiply usable capacity across each fiber pair within the cable, since the enormous cost of manufacturing, laying, and maintaining a submarine cable makes maximizing capacity per fiber essential to the economics of the investment
Terminates at coastal landing stations, which connect the submarine cable's capacity onward into terrestrial transport networks and, ultimately, internet exchanges and data center infrastructure
Vulnerable to physical damage from fishing activity, anchoring, and underwater geological events, making cable route diversity and repair capability genuine resilience considerations rather than theoretical risks
Represents the fiber-based alternative to satellite communications for intercontinental connectivity, offering substantially higher capacity and lower latency where a cable route exists, at the cost of the fixed physical infrastructure investment and vulnerability a cable carries that a satellite link does not

Concept

A submarine cable carries data as light pulses through fiber-optic strands protected within a heavily armored cable structure designed to withstand the ocean environment, with DWDM equipment at each landing station multiplexing many separate wavelength channels onto each fiber pair to extract far more usable capacity than a single unmultiplexed channel could provide — directly justifying the enormous capital cost of manufacturing and laying cable across an ocean floor. This DWDM-multiplied capacity is most concretely expressed as throughput — the sustained data rate a given cable system can actually deliver — making throughput the key performance metric operators and customers use to evaluate and compare submarine cable capacity across routes.

Explainer

The economics that make submarine cable the dominant choice for intercontinental connectivity despite its high upfront capital cost come down to capacity and latency at scale — once laid, a submarine cable's DWDM-multiplied capacity can carry vastly more traffic at lower per-bit cost and lower latency than a satellite link serving the same route could achieve, meaning the enormous fixed capital investment amortizes favorably against high, sustained intercontinental traffic volume. This is precisely why satellite communications functions as a genuine alternative specifically where cable infrastructure doesn't reach or isn't economically justified — remote islands, temporary or emergency connectivity needs, or routes where traffic volume doesn't justify cable investment — rather than as a broad competitor to submarine cable for high-volume intercontinental routes generally. For CE verticals, submarine cable route diversity and landing station resilience are meaningful due-diligence considerations for any organization depending on intercontinental connectivity for critical operations — maritime, energy, and telecommunications operators evaluating international connectivity resilience need visibility into which physical cable routes and landing stations their traffic actually depends on, since a single point of physical vulnerability can affect connectivity regardless of how much capacity the underlying cable itself provides.

Cite this entry

Submarine Cable. ConnectedEarth Knowledge Base. https://connectedearth.space/knowledge-base/submarine-cable/ (updated 13 September 2026).