Beneath the Ocean: The Invisible Network That Connects the World (Part 1)
When we make an international call, send a message overseas, transfer money to another country, or join a video call with someone thousands of kilometers away, it feels almost instantaneous.
It is easy to imagine that all this information is traveling through satellites somewhere above us.
In reality, most international communications travel in the opposite direction—under the sea.
Hidden on the ocean floor is an enormous network of submarine cables (海底ケーブル) connecting countries and continents. Today, these cables carry around 99% of international communications and form one of the most important pieces of infrastructure behind our connected world.
And for a company like Brastel, whose history is closely connected with international telecommunications, the story of submarine cables is also part of the story of how people around the world are able to stay connected.
From Morse Code to the Global Internet
Submarine communication began more than 170 years ago. In 1850, an underwater telegraph cable connected Britain and France, followed in 1858 by the first transatlantic cable linking Europe and North America.
Technology quickly evolved: TAT-1 enabled transatlantic telephone calls in 1956, and in 1988, TAT-8 introduced fiber-optic technology, carrying information as pulses of light. This same basic technology powers today's global communications.
What Does a Submarine Cable Actually Look Like?
A cable capable of connecting continents might sound enormous.
The core that actually carries the information, however, consists of extremely thin optical fibers.
These fibers are protected by several layers of insulation, metal, and other materials designed to withstand enormous pressure, seawater, and decades of operation.
For very long routes, repeaters are installed along the cable to amplify the optical signal. Modern systems are designed to operate thousands of meters below the surface; NEC, for example, says its systems are designed for environments reaching depths of around 8,000 meters and for approximately 25 years of operation.
Near coastlines, cables are particularly vulnerable to anchors and fishing equipment, so they can be buried beneath the seabed. In deep ocean areas, they can simply rest on the ocean floor.
Specialized cable ships are used to transport and carefully lower thousands of kilometers of cable into the ocean.
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| Image generated by AI |
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| Tiny optical fibers inside the much larger protective cable |
What Happens When You Make an International Call?
Imagine someone in Japan calling their family in Brazil.
Their voice first has to be converted into a signal that telecommunications networks can transport.
Depending on the service and networks involved, different technologies may be used. Modern telecommunications increasingly carry voice as digital/IP traffic, while connections with traditional telephone networks may still involve telephone switching infrastructure.
A simplified journey might look like this:
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| Your phone → local/mobile network → telecommunications provider → international network → submarine fiber-optic cable → overseas telecommunications network → recipient's network → recipient's phone |
Inside a fiber-optic network, the digital information representing your voice travels as optical signals.
And it travels incredibly quickly.
This is one reason modern international calls can feel almost like speaking with somebody nearby, even though the signal may travel thousands or tens of thousands of kilometers before reaching them.
Importantly, there is not necessarily one dedicated physical cable connecting the two people. Telecommunications operators interconnect with other carriers and networks, and traffic can be routed through different international paths depending on network design, agreements, availability, and destination.
Aren't International Calls Made by Satellite?
They can be — but satellites are not the main infrastructure carrying today's international communications.
Submarine fiber has enormous capacity and is well suited to transporting huge quantities of data between continents. Modern submarine cables carry not only telephone traffic but internet traffic, financial transactions, cloud services, streaming, corporate communications and many other forms of digital information.
That means the same invisible infrastructure supporting an international phone conversation also helps support things we use every day:
WhatsApp and other messaging services, video calls, international banking, credit-card payments, cloud computing, social media, streaming, online games, AI services and international business systems.
The modern world would look very different without the cables beneath the ocean.
To be continued...
