Subsea cable (submarine cable)

A subsea cable (submarine cable) is a fiber-optic cable laid across an ocean or sea floor to carry internet and telecom traffic between countries and continents. Modern systems use multiple fiber pairs, each carrying tens of terabits per second via dense wavelength-division multiplexing, with newer cables reaching over 300 Tbps of total design capacity. More than 550 active submarine cables span over 1.4 million km worldwide and carry the large majority of intercontinental internet traffic, with satellite links handling only a small residual share. Cables typically cost $200-500 million and take 2-3 years to plan, permit and lay, and their landing stations tie directly into nearby carrier-neutral data centers and meet-me rooms. Because a handful of narrow chokepoints — the Red Sea, the Luzon Strait, the English Channel — carry a disproportionate share of global routes, a single cable fault from anchor drag or fishing gear can degrade connectivity for entire regions until repair ships restore service, sometimes over several weeks.