# Submarine cables

> Cables on the ocean floor that carry almost all the internet traffic between continents.

- Level: Basic
- Topics: Networks
- URL: https://tidbit.legios.com.ar/submarine-cables/
- In Spanish: [Cables submarinos](https://tidbit.legios.com.ar/es/submarine-cables/)

When you watch a video hosted in another continent, the data almost certainly crossed the ocean through a **submarine cable**, not a satellite. There are several hundred of these cables lying on the seabed, together more than a million kilometers long, and they carry the vast majority of traffic between continents: video calls, bank transfers, cloud backups, everything.

Inside, they are surprisingly thin. The heart is a handful of fiber optic strands, each thinner than a hair, carrying light. Around them go layers of copper, plastic and, near the coast where anchors and fishing nets are a danger, steel armor; in the deep ocean the whole cable is roughly the width of a garden hose. Every 50 to 100 kilometers a **repeater** boosts the light signal, powered by electricity sent down the cable itself from the shore. Each end arrives at a **landing station** on the coast that connects it to land networks.

Cables used to be built by groups of phone companies; today Google, Meta, Amazon and Microsoft own or co-own many new ones. They break more often than you would think, mostly from ship anchors and fishing, and repair ships have to hook the cable up from the seabed. Because there are many routes, traffic usually just goes around a break, but countries served by one or two cables, especially islands, can lose most of their connection for days.

## An analogy

The highways under the sea. Satellites are like small planes: useful where there are no roads, but almost all the cargo moves by truck on the highways, because they carry far more, far cheaper.

## Keep in mind

- Carry the vast majority of internet traffic between continents.
- Fiber optic strands inside, armored near the coast, hose-thin in deep water.
- Repeaters along the route boost the signal; landing stations connect them to land.
- Big tech companies now own or co-own many of the newest cables.

## Go deeper

- [Submarine Cable Map (TeleGeography)](https://www.submarinecablemap.com/)
- [Submarine communications cable on Wikipedia](https://en.wikipedia.org/wiki/Submarine_communications_cable)

## Related terms

- [Cloud computing](https://tidbit.legios.com.ar/cloud-computing/): Renting computers over the internet instead of buying your own.
- [Backup](https://tidbit.legios.com.ar/backup/): A separate copy of your data, kept so you can get it back when the original is lost.
- [Fiber optic](https://tidbit.legios.com.ar/fiber-optic/): Thin strands of glass that carry data as pulses of light, fast and over long distances.
- [Google](https://tidbit.legios.com.ar/google/): The search company that gives most products away and makes its money on ads.
- [Meta](https://tidbit.legios.com.ar/meta/): The company behind Facebook, Instagram and WhatsApp, paid for by advertising.
- [Amazon](https://tidbit.legios.com.ar/amazon/): An online store with its own delivery network, and the company that runs AWS.
- [Microsoft](https://tidbit.legios.com.ar/microsoft/): The company of Windows and Office, now just as much a cloud company with Azure.
- [Internet](https://tidbit.legios.com.ar/internet/): A worldwide network of networks that lets any connected device reach any other.