Look a little closer
Most intercontinental Internet traffic does not travel through satellites. It crosses oceans in fiber-optic cables on the seabed; the International Telecommunication Union estimates they carry about 99 percent of international Internet data.
At the center are strands of glass roughly comparable to a human hair. Shore equipment converts data into rapidly pulsed laser light, which travels along the fiber while remaining guided within the glass.
Light gradually weakens across an ocean. Long routes therefore place optical amplifiers called repeaters at intervals to boost the signal. Landing stations connect the wet section to terrestrial networks and supply electrical power along the cable.
A deep-ocean cable may be only about the width of a garden hose, with waterproofing, insulation and strength layers surrounding the fibers. Near coasts, where anchors and fishing pose greater risks, cables receive heavier armor or are buried below the seabed.
When a cable breaks, a specialized ship locates the fault, retrieves the line and splices in a replacement section. Operators can reroute data through other cables, but regions with few alternatives may experience serious slowdown or outages.
Satellites are valuable for remote and mobile connections, yet submarine fiber is the hidden core of high-capacity links between continents. Opening an overseas server can send pulses of light across several ocean floors.
