How Do Undersea Data Transmission Cables Work?

Ever wondered how YouTube videos get sent across the globe in milliseconds? Or how do people video chat with their friends in distant countries from the US in real-time?

Well, all this is made possible thanks to undersea cables that stretch thousands of miles along ocean floors to link continents, countries, and cities around the world. Laying communication cables underwater takes a lot of preparation, special cables, and some unique equipment.

Undersea Cables: Why are they so important?

With a majority of old telecom systems relying on satellites to transmit data, quite a large number of people believe that information sent over thousands of miles is first beamed to an orbiting satellite and over to another country. However, as it turns out, satellites aren’t designed to handle large flows of information. Apart from being expensive, there’s also the issue of having to deal with frequent data and signal loss. Sending several terabytes of information through space can be very expensive. In fact, according to Mental Floss, 99% of international data is transmitted through cables laid on ocean floors called submarine communications cables. A vast majority of the data sent around the world travels through over one million miles of cables sitting on ocean floors. From one point to the other, these communication cables can be as short as 81 miles to 12,427 miles long for the Asia-America Gateway cable.

Submarine transmission of information through cables is “old business”

The laying of subsea connectors along the bottom of the sea might seem like something that requires the use of advanced technology – and the tools and equipment used today are. However, we have been laying cables on ocean and seafloors for over 160 years! The first-ever communications cable, the Transatlantic cable, was laid in 1858 to help improve telegraph communications. Once finished, the cable, which connected Newfoundland, Canada to Ireland, decreased the amount of time it took to communicate from days or even weeks to a matter of minutes.

Sadly, it wasn’t long before the cable started to degrade. To keep communications and make the signal stronger going, one Wildman Whitehouse, an English Electrical experimenter, turned up the voltage, causing the cable to fry. Over the following years, two more communications cables were fried before a newer, more advanced cable was installed in 1865, resolving the issue.

Today, the cables have repeaters every 40 to 80 kilometers that help amplify the signal to ensure that it travels for thousands of miles without restrictions. The cables available today can handle well over 200Tbps of data – and such speeds over a few strands of communication cable as small as one hair. Today’s fiber-optic cables, which are about as wide as human hair, are what’s responsible for transmitting data across the ocean floor. These communication cables typically house about 4 to 12 strands of fiber optic cables.

If laid in deeper parts of the ocean or seas where it does not need as much protection, the cable is only a little larger than your thumb’s width. However, if laid in extremely deep parts of the ocean or in shallower waters, where it needs to be made a little bit tougher, then the cable is made thicker – about the width of the human wrist. Despite these sizes, the data itself is transmitted across flawless glass that’s about the size of a needle.

How are fiber optic communication cables made?

The process is pretty straightforward, the cable is covered with different layers until it’s tough enough to withstand the environment it’ll live in for 25+ years. Cables that are buried in the ocean are generally a lot smaller. Fiber optic cables are gel-coated and stay inside a tubing made of copper that carries electricity. The copper tubing is then surrounded by a plastic tube followed by stranded steel wires and an aluminum water barrier. After that, the cable may be braided with additional steel wires if extra protection is required followed by a rope made of nylon, then tar. The cable is then covered with a plastic coating to help seal it off. As a result, the difference between cables that need little protection and those that need significant protection is quite huge.

Wondering why fiber optic cables are enclosed in copper tubing? That’s because the copper carries the power needed to keep the repeaters (we mentioned earlier) running, so they can amplify the light and ensure the signal reaches its destination. These repeaters can weigh over 550 pounds (250kg).

So how are fiber optic cables installed?

First, the cable has to be loaded on a cable-lay vessel that’ll take it out to sea or ocean with some vessels being able to carry up to 2,000 km (1242 miles) of cable. Loading the cable can take 3-4 weeks, which can then be installed/laid at a rate of about 200 km/day with the right tools and equipment. Once the cable has been loaded on the vessel, it is then laid out to the water’s edge starting from the shore. The vessel laying the cable gets as close to the shore as it possibly can without grounding and starts to dig.

These vessels pull a special type of plow that not only digs a trench but also simultaneously lays the cable. Sometimes, the cables have to be picked up if they cannot be buried or if they run over another cable. There’s a lot of planning that goes into determining the route the cable-laying vessel will take – rocks, fault lines, coral reefs, valleys, and undersea mountains all need to be taken into consideration. In most cases, those responsible will do their best to lay the cables in parts of the sea or ocean that minimize the risk of damage from fishing trawlers and boat anchors. To save time, the vessels can start laying the cables from two different points until they meet and the cables are attached.

Sharks and spies!

What dangers do undersea cables face?

Sharks seem to find undersea cables quite tasty. On several occasions, these sea creatures have been caught chewing on the cables and no one knows why. According to Mental Floss, this could be due to the electromagnetic fields that the cables produce. Maybe they are just curious or they are trying to destroy our communications infrastructure before staging a land-based assault. Whatever the case, the fact remains that sharks gnaw on our internet cables, and sometimes even destroy them. In response. To prevent this, some companies like Google have now resorted to shielding their undersea communication cables with shark-proof wrappers made of wire.

Another problem that plagues undersea cables is that they lay under or on the seafloor unprotected from spies. During the cold war, the Soviet Union transmitted weakly encoded messages through a cable they thought was well guarded to be of any major concern. The US developed a special type of submarine which they named the U.S.S. Halibut to tap the cable and pick up Soviet transmissions regularly. Ever since then, tapping underwater communication cables for information has been a common occurrence.

What happens when communication cables become outdated?

There are several options for communication cables that are no longer being used. The typical lifespan for communication cables is believed to be about 25 years though they do not expire. Normally, before the 25-year period is up, new technology will have come out, meaning that the cables have become outdated. Obsolete cables are often generally repositioned and laid along new paths, which is great for regions that do not need as much capacity and would like to save on costs since operating and managing these cables generally costs hundreds of millions of dollars.

Some companies buy the rights to pull and salvage these cables for their raw materials. In some cases, the cables are left where they sit, in which case, they’re referred to as dark fiber. Even without signals passing through them, they make great seismic networks for scientists to study earthquakes and geological structures.

Read more:
How Do Undersea Data Transmission Cables Work?