4.3 Undersea Cables, Satellites, and Global Infrastructure
In the previous section, we learned that Internet service providers, Autonomous Systems, and network exchanges help move data between networks.
After looking at who carries Internet traffic, next we will look at how that information physically travels around the world.
- When someone in California visits a website hosted in Europe, how does the data cross the Atlantic Ocean?
- When someone in Australia sends a message to Canada, how does that information travel between continents?
Many people imagine the Internet as something wireless, virtual, or floating in the cloud. In reality, the Internet depends on a vast physical infrastructure made of cables, data centers, routers, exchanges, and communication equipment spread across the globe. The Internet may feel invisible, but much of it exists in the physical world.
The Physical Internet
When people use Wi-Fi, mobile phones, or wireless devices, it is easy to assume that most Internet traffic travels through the air.
Wireless technologies are certainly important. Your phone may connect wirelessly to a cellular tower. Your laptop may connect wirelessly to a home router. However, once that information enters the larger Internet, it usually travels through physical infrastructure.
The modern Internet relies heavily on fiber-optic cables. These cables carry enormous amounts of data between cities, countries, and continents. In many ways, fiber-optic networks form the backbone of the Internet. A backbone network is a major high-capacity network that carries large amounts of traffic between other networks. Without these backbone connections, global Internet communication would not be possible.
Fiber-Optic Cables
A fiber-optic cable contains thin strands of glass or plastic that transmit information using pulses of light. Much of the Internet travels as light moving through fiber.
When data is transmitted through a fiber-optic cable, electronic information is converted into optical signals. These light signals travel through the fiber and are later converted back into electronic information when they reach their destination.
Fiber-optic communication offers several advantages.
- It can carry large amounts of data.
- It can transmit information over long distances.
- It is generally fast and reliable.
- It is also less vulnerable to certain forms of electrical interference than traditional copper wiring.
Because of these advantages, fiber-optic infrastructure has become one of the most important technologies supporting the modern Internet.
Undersea Cables
One of the most remarkable parts of Internet infrastructure is the global network of submarine cables.
A submarine cable is an undersea fiber-optic cable placed on the ocean floor.
These cables connect continents and carry enormous amounts of international Internet traffic. Today, hundreds of submarine cable systems connect countries around the world.
Many people assume satellites carry most global Internet traffic. In reality, the overwhelming majority of international Internet traffic travels through submarine fiber-optic cables.
These cables connect North America, South America, Europe, Africa, Asia, Australia, and many island nations.
For example, when a user in the United States accesses a website hosted in Europe, the data often crosses the Atlantic Ocean through one or more submarine cable systems.
Similarly, communication between Asia and North America frequently relies on cables crossing the Pacific Ocean.
Without these cables, modern global communication would be dramatically slower, more expensive, and less reliable.
Cable Landing Stations
Submarine cables do not simply emerge from the ocean and connect directly to homes. Instead, they connect to facilities called cable landing stations.
A cable landing station is a location where an undersea cable reaches land and connects to terrestrial networks.
These facilities contain networking equipment that helps move traffic between submarine systems and regional Internet infrastructure.
From a landing station, traffic can continue across national fiber networks, Internet exchanges, data centers, and other communication systems.
Although most users never see them, cable landing stations are important links between global and local Internet infrastructure.
Satellites and Internet Connectivity
Satellites also play an important role in global communication.
A communications satellite is a spacecraft that receives, processes, and transmits signals between locations on Earth.
Satellite Internet can provide connectivity to places where traditional wired infrastructure is difficult or expensive to build.
For example, satellite systems may serve:
- Remote rural communities
- Ships at sea
- Aircraft
- Scientific expeditions
- Disaster response operations
Satellite technology has improved significantly over time. Older satellite Internet services often relied heavily on satellites positioned far above Earth in geostationary orbit. Because signals had to travel such long distances, users often experienced noticeable delays known as latency.
Latency refers to the time required for information to travel from one point to another.
High latency can make activities such as gaming, video calls, and interactive applications feel slower or less responsive.
Low-Earth-Orbit Satellite Networks
Low-Earth-orbit satellite systems have also become increasingly important.
Low-Earth-orbit, often abbreviated LEO, refers to satellites operating much closer to Earth than traditional geostationary satellites.
Because these satellites are closer, signals travel shorter distances. This generally reduces latency and improves responsiveness.
Modern LEO satellite networks use large constellations of satellites working together to provide coverage across broad geographic areas. LEO systems have significantly expanded Internet access in many rural and underserved regions around the world. Although they do not replace terrestrial infrastructure, they provide valuable connectivity options where other solutions may be difficult to deploy.
Why Satellites Do Not Replace Cables
Given the success of modern satellite systems, some people wonder why the entire Internet is not moved into space.
The answer largely comes down to capacity, efficiency, and cost.
Fiber-optic cables can carry enormous amounts of traffic. They provide extremely high bandwidth and can support vast numbers of users simultaneously. For most large-scale communication needs, fiber remains more efficient than satellite communication. As a result, satellites and fiber often complement one another rather than compete directly.
Fiber handles much of the world’s high-capacity Internet traffic.
Satellites help extend connectivity to locations where fiber may not be practical.
Both technologies contribute to the global Internet.
Redundancy and Reliability
The Internet was designed to be resilient. One reason for this resilience is redundancy.
Redundancy means having multiple paths, systems, or components available in case something fails.
For example, many regions are connected through multiple fiber routes rather than a single cable. Large networks often maintain backup connections. Data may be rerouted through alternative paths when disruptions occur.
This does not mean the Internet is immune to outages. Submarine cables can be damaged by natural events, accidents, fishing activity, or construction work. Network equipment can fail. Power disruptions can occur.
However, the existence of multiple routes helps reduce the impact of individual failures. This redundancy is one reason the Internet can continue functioning even when parts of its infrastructure experience problems.
Why Infrastructure Matters
Behind websites, apps, videos, and online services lies a vast global infrastructure.
- Fiber-optic cables carry data between cities and countries.
- Submarine cables connect continents.
- Cable landing stations link international networks to local infrastructure.
- Satellites extend connectivity to remote locations.
- Routers, exchanges, and service providers help move traffic between networks.
Together, these systems form the physical foundation of the Internet. Without them, the digital world that people use every day could not exist.
Looking Ahead
Now that we have examined how information is addressed, routed, and transported across the world, we will look at:
- Where do websites, applications, cloud services, and online platforms actually live?
- When you visit a website, where is the server located?
- How do companies support millions or even billions of users at the same time?
In the next section, we will explore data centers, cloud infrastructure, and the massive facilities that power the modern Internet.