Science Questions with Surprising Answers
Answers provided by
Dr. Christopher S. Baird

Why do most international phone calls and data links go through satellites?

Category: Society      Published: November 22, 2013

cable laying ship
Cable laying equipment on the Great Eastern, the ship that laid the first transoceanic cable. Public Domain Image, National Maritime Museum.

Actually, most international phone calls and data links these days do not go through satellites. Instead, telecommunication signals go across earth's oceans through cables running along the bottom of the oceans. Transoceanic submarine cables have existed since 1858 when they were first introduced in order to carry telegraph signals. Detailed maps of today's submarine cables can be found on websites such as Satellite links currently account for only about 1% of international telecommunications. The rest travels through undersea cables. The reason for such a high use of submarine cables is that they can carry much more information per second and are much more reliable.

The first submarine cables were simple metal wires carrying telegraph signals. Later on, metal cables were laid that could carry telephone and data signals. Finally, optical fiber cables carrying light signals began to be laid under the oceans in the 1980's because optical fiber signals are faster and can carry more information than metal-based signals. Satellites are still used for telecommunications though, but mostly just in remote regions that do not yet have access to landlines.

Topics: optical fiber, phone, satellite, submarine cable, technology, telecommunications