How Is The Internet Connected Between Countries & Continents?

Underwater Internet Cables

It is pretty well known how internet connectivity works within houses and even within countries, where a distribution network of fiber optic cables delivers internet to different parts of the country.

But how are different countries and continents connected to each other online? How example can we send an email to someone in Australia or Skype chat with someone in India when they are the other side of the world?

The answer modern answer may be a little surprising:

In modern times 99% of international internet traffic is delivered not by satellites but by a complex network of underwater cables that are laid across the ocean floor and extend to hundreds of thousands of miles in total length.

There are now many dozens of these cables which connect countries and continents all over the world, and the newest ones can transfer data at a rate of 160 Terabits per second or more.

Satellite technology used to be widely used until fairly recently but it is known to be costly and bandwidth is limited. Latency is also very high in satellite technology where data has to be sent into space and back again. Lets look in more detail at the fascinating technology of submarine internet cables.

The growth in underwater internet cables in the last decade has been huge. For instance, in 2006, underwater cables accounted for only 1% of internet traffic. This has increased to 99% in just over a decade, showing just how effective these cables are.

They can deliver far more data far faster and ultimately more cost effectively than satellites, even though the initial costs of installation of these cables in very high.

Facts & Figures on Submarine Internet Cables

To put the scale of use of these cables into perspective, lets look at a few stats.

  • As of early 2018 there were 448 of these underwater cables in operation worldwide, adding up to over 1.2 million kilometers in total distance.
  • They can run at depths of over 8000 meters, which is as deep as Everest is tall, and connect virtually every country and continent on earth, with the exception of Antarctica.
  • Most of the modern cables can transfer data at a rate of 60 Terabits per second, whilst the ultra modern 6,600km long Marea cable that connects America with Southern Europe can transfer data at the impressive rate of 160 Terabits per second, which is equivalent to 1 million megabits per second.
  • Installing these cables is obviously a very lengthy and costly process. The cost of each one varies with the length of the cable and a host of other factors but the cost can be expected to easily run into the hundreds of millions of dollars.

The new 9000km FASTER undersea cable funded by Google for example, which connects Japan to the West Coast of America via Oregon, opened in 2016 and cost around $300 million. Whilst this is no doubt a hefty bill even for a tech giant like Google, a 60 Terabits per second data capacity easily justifies the initial investment in a world where bandwidth demands continue to grow by the day.

Cables are typically built to last 25 years, but this is not set in stone; some last less and some last longer. More cables continue to be planned and installed each year; operational cables are referred to as “lit” and non operational or decommissioned cables referred to as “dark” cables.

Global Submarine Cable Map

Submarine Cable Map

The History of Underwater Data Cables

The history of underwater cables for transferring data stretches back well over 150 years to the 1850s. The first undersea Transatlantic cable was used on the 16th July 1858, but to get to that point required an enormous amount of effort and many setbacks and failures.

The man most responsible for bringing underwater communications cables into operation was an inventor and entrepreneur called Cyrus Field.

He first had the idea of underwater cables back in the 1840s and was determined in his efforts to create and deploy the technology. He was relentless in seeking backers and investment and survived many setbacks and failed attempts to install the cables.

Without the tenacity and determination of Field to make underwater communications cables work, we may not enjoy the global connectivity structure we do today. Despite many failures and setbacks he showed it could be done and paved the way for others to refine and develop the technology in the following century and a half.

Thanks to his efforts and those that followed him data can be sent from one part of the world to virtually any other part of the world often in less than a second.

Underwater communications cables could only handle Morse code until 1956, when the technology was updated so that phone calls could also be sent. Initially the capacity was very low, with the capacity for maybe a few dozen phone calls at once.

In some countries older people will remember when you had to “wait in line” to make a phone call abroad due to the capacity limits of the cables for transferring data at the time.

In the 1980s Fibre Optic cables were introduced which allowed a much larger capacity of phone calls in the thousands. Boosters were later added in the next decade which increased the capacity to millions of phone calls. Waiting in line to make an international call was no longer needed!

The Process of Laying the Cables

The process of laying the cables is long and laborious but although technology has evolved massively since the 1850s, the general method used for installing the cables has not changed much from that used by Field in the early days. Unsurprisingly it is a very costly and time consuming process and needs to be carried out meticulously to avoid damage to the cable and the ocean ecosystem.

The cables have to be first prepared and loaded onto a ship…….

…..and then carefully laid onto the ocean floor

The cables are rolled onto several large spools to be placed on a ship and gradually laid onto the ocean floor. Given that some cables can be thousands of kilometers long this is a painstaking process requiring a lot of accuracy and attention to detail to make sure the cables don’t get snagged, kinked or otherwise damaged.

They are then send out on a ship to sea with the cable being gradually fed onto the ocean floor on a specific pre-planned route to allow minimal disruption and risk of damage to the cable.

In deeper parts of the ocean the cable is thinner (about an inch wide) and can simply be laid on the floor; closer to the shore and once on land they are often the width of a soda can and are buried slightly underground to prevent vandalism and other damage.

The cables themselves are nowadays a complex multi-layered construction, with the fibre optic strands in the middle that actually carry the data protected from the elements by multiple other layers of cable and petroleum. The number of fibre optic strands in the middle can vary from anything between 8 to several dozen. The data capacity of the cables will obviously increase as a result.

A Breakdown of a Submarine Internet Cable

breakdown of a submarine cable

The different layers are composed as follows:

  1. Polyethylene
  2. Mylar Tape
  3. Stranded metal (steel) wires
  4. Aluminium water barrier
  5. Poly-carbonate
  6. Copper or aluminium tube
  7. Petroleum jelly
  8. Optical fibers

See here for an interesting article that follows a ship crew who undertakes this work. The rate at which the cable can be laid will obviously depend on a lot of factors such as weather, currents, and the length and complexity of the cable and route.

On a good day, a crew working on this can expect to lay 100 to 200km of cable. It is important to proceed at a slow methodical pace an if they attempt to lay the cable too fast then snags and kinks can develop which can take time to untangle.

Once onshore the cables are sent, usually underground, to a distribution center of some sort where the data is then fed out to the rest of the country. These locations that these cables come onshore and where they are fed to is often kept very secretive because of fears of terrorism or other vandalism.

Because of the sheer amount of data that is being sent and the power demands of fiber optic cables, electricity bills at these distribution centers can run into tens of thousands per month. See here for a fascinating article on the subject from the UK.

A submarine cable coming onshore

What If Underwater Cables Get Damaged and Broken?

With well over 400 underwater cables currently in operation, damage to them is common. The article here reports that there are typically around two faults per week or 100 per year somewhere in the world.

The most common cause is fishing vessels unwittingly dropping anchor or trawling on top of a cable, cutting or damaging it by dragging it along the ocean floor. Earthquakes and underground volcanoes can also damage submarine cables.

In these cases a specialized ship and crew are sent out to find and repair the damaged cable. In remote and/or deep parts of the ocean this can be painstaking work and often requires expensive equipment to retrieve snapped or damaged cables and haul them to the surface to be repaired.

In deep parts of the ocean special Remote Operated Vehicles (ROVs) have to be deployed to find the cable with the help of cameras and special hooks or claws. In cases where the cable has been broken in two then all the separate fibre optic strands must be married back up correctly to their other half; not easy when these strands are less than the thickness of a human hair!


When a cable breaks or malfunctions internet users may or may not be affected. Nowadays there are so many cables in existence that even if one cable breaks others will pick up the slack and the traffic will go through those instead.

With multiple cables going to countries and continents especially in the developed world, traffic is often re-routed through alternate cables so browsers will hardly notice any difference in their internet speeds.

However, broken submarine cables can sometimes noticeably affect internet users in some parts of the world. In 2008 internet speeds ground to a halt in India and other countries as a cable in the Mediterranean was cut by a ship anchor, drastically reducing internet speeds in India, Egypt, UAE and other countries for several days.

A similar disruption also happened in 2011, slowing internet speeds in the Middle East. Another broken cable off the coast of Kenya in 2012 left several African countries without internet.

Multinational Companies in on the Action

With the continued growth in undersea internet cables it is probably no surprise that Multinational companies are also getting involved in the industry. Google, Facebook, Microsoft and Amazon all now have investments in submarine cables in various parts of the world.

Often it is so these companies have additional bandwidth and dedicated service for some of their own services, such as Microsoft with its various services like Skype, Office365, Azure and Xbox Live.

We have already mentioned the $300 million FASTER cable which Google has a stake in which connects Japan and the USA. It was launched in June 2016 and has a 60 terabits per second capacity. Google also has an investment in the 11,000km MONET cable which connects the USA with Brazil with six fibre pairs and a capacity of 64T/bits per second. It has been in operation since late 2017.

Microsoft and Facebook partially funded the 4000 mile MAREA cable which launched in early 2018 and connects the Virginia on the east coast of the USA to Bilbao in Spain with a 160 Tb/s capacity.

Elsewhere Amazon and Facebook are also invested in the new 14,000km Trans-Pacific JUPITER cable which will connect Japan and the USA and is set to be completed in early 2020 ready for the Tokyo Olympics. It too will boast a 60 Terabits per second capacity and will allow increased demands for VR and 4K/8K video streaming with no problems.

It is not difficult to see why large multinationals want to get involved in building submarine communications cables. With global bandwidth demands continuing to grow and new technology developing every year it makes sense for large global companies to have their own submarine cables so they have dedicated channels through which they can send their data and services worldwide and stay on top of the game.

Submarine Fibre Optic Cables Round the World – The TAT-14,  SEA-ME-WE 5, MAREA, and MONET Submarine Cables

The TAT-14 Cable – North America to Europe and Back Again

TAT-14 Submarine Cable
The South East Asia – Middle East – Western Europe (SEA-ME-WE-5) Cable – a huge cable spanning 20,000 kilometers
SEA-ME-WE-5 Submarine Cable
MAREA Cable – 4000 mile cable connecting North America with Bilbao in Spain
Marea Submarine Cable
MONET Cable – connects North America to Brazil
Monet Submarine Cable

The Future of Submarine Internet Cables

There is no sign of data demands letting up around the world as new data bandwidth hungry devices and technologies continue to arrive on the scene year after year. Video resolutions keep getting higher and higher and VR technology is also a growing market.

In addition more and more devices such as tablets, iPhones, iPads, Games Consoles and other gadgets and connecting to the internet, bandwidth demands, both domestic and international, keep growing all the time.

Thankfully, there is no letting up in the laying of new submarine data cables to keep up with this increased demand. In just 12 years between 2006 and 2018 the percentage of international traffic delivered by submarine cables grew from 1% to 99%, indicating just how fast they have grown and displaced satellites as the number one way to send data between countries and continents.

The investments are huge and the logistics and maintenance complex but the rewards are even greater with lightning fast data transfers anywhere in the world.

In addition the new cables tend to carry with them an impressive data capacity of 60 terabits per second, with the potential to increase this further, which should be able to absorb even a large increase in bandwidth demand in the years to come.

The technology and process used to lay these cables has also been refined and perfected over the last few decades, as has the repair process, so cables can now be installed and fixed much more quickly than before. The future looks good for global connectivity.


Online gamer and general home networking enthusiast. I like to create articles to help people solve common home networking problems.

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