Submarine Cables and the Physical Internet

Despite the popular image of data floating wirelessly through "the cloud," roughly 99% of intercontinental internet traffic is carried physically along fiber-optic cables laid on the ocean floor. According to data compiled by the industry research firm TeleGeography, more than 530 active and planned submarine cable systems span over 1.4 million kilometers of seabed as of the mid-2020s. The first transatlantic telegraph cable, championed by the American entrepreneur Cyrus Field, was completed in 1858, followed by the first transatlantic telephone cable, TAT-1, in 1956. The first fiber-optic transatlantic cable, TAT-8, went into service in 1988, built by a consortium including AT&T, France Télécom, and British Telecom, and carried a then-remarkable capacity of 280 megabits per second — a figure dwarfed many times over by modern cables carrying tens of terabits per second on a single fiber pair.