FEATURE
CONNECTED
BY SEA
A niche industry is responsible for placing and maintaining a dense network of fiber-optic cables that crisscrosses the ocean floor to connect the world.
Written by Tom Gibson
An offshore cable laying vessel sets course to place fiber optic connections. Photo: Getty
IN THIS AGE OF INTERNET COMMUNICATIONS, data is transmitted through the air to myriad computers, routers, servers, and cell phones. But if you look much further down, you might see wires traversing across our oceans to connect continents. They’re increasing in number and play an important role in our high-tech society.
Few people know about this undersea cable industry and it suffers a chronic worker shortage to keep it running. “Submarine cables are a critical but often forgotten part of global communications. People picture the Internet as being wireless, but these long, thin cables transmit data more cheaply and efficiently than satellites,” explained Lane Burdette, a research analyst at Washington, D.C.-based TeleGeography, which builds and maintains data sets used to monitor, forecast, and map the telecommunications industry.
Burdette, who focuses on submarine cables, data centers, and cable landing stations, added that these cables are being built all over the globe.
“There was a big boom from around 1980 to 2002, when we had the dot.com boom. There were a lot of cables built then,” said Peter Jamieson, vice chairman of the European Subsea Cables Association, a trade group of cable owners located near Yorkshire in U.K that own, operate, and maintain cables in European waters. “Then it went dormant for about 10 or 12 years. Since 2015, with the rise of social media and companies like Meta, Google, Amazon, and Microsoft, you see new cables going in all the time.”
Cross-section of a submarine fiber-optic cable showing protective layers surrounding the optical fibers. Photo: Getty
Video: Getty
NOTHING NEW
Subsea telecommunication cables have a long history, going back to the early days of the telegraph. Since the installation of the world’s first submarine cable across the Dover Strait in 1850, connecting France and England, subsea cables have become essential to the world’s communications infrastructure.
With the inception of fiber optic cables in the late 1980s, the longest cable system has been the Sea-Me-We 4 (Southeast Asia to Western Europe), measuring more than 40,000 kilometers (24,800 miles), with many landing points in the various countries situated along its route. Modern fiber optic cables carry millions of telephone calls and huge amounts of video and internet data. Submarine cables handle roughly 95 percent of the world’s telecommunication requirements. Cables are owned by the tech giants instead of the old telecommunication companies such as Bell and AT&T. Some 800,000 miles of cables crisscross the Earth’s oceans as part of nearly 600 different systems, according to TeleGeography.
But undersea cables are surprisingly thin—only about the diameter of a fat garden hose. Their protective layers consist of multiple coatings and armoring on the outside to protect against the harsh ocean environment. Lasers on one end fire rapidly down thin glass fibers to receptors at the other end. Whereas cables once connected cities, they now connect data centers. Typical of modern cables, the Anjana cable system is a 7,121-kilometer (4,415-mile) transatlantic fiber optic submarine cable connecting Myrtle Beach, S.C. in the United States and Santander, Spain. It is privately owned and operated by Meta through multiple subsidiaries. It consists of 24 fiber pairs (48 individual fibers), each with a design capacity of about 20 terabits per second (1 trillion bits).
Due to come online this year, the Anjana was supplied by NEC, a Japanese multinational information technology and electronics corporation headquartered in Tokyo, Japan. They design, manufacture, and install cables.
A 3D rendering of underwater fiber optic cables on sea floor. Photo: Getty
“Submarine cables are a critical but often forgotten part of global communications.”
– Lane Burdette, a research analyst at TeleGeography
BETTER THAN SATELLITE
“Satellite communication is fantastic in terms of broadcasting to large regions, like TV for example, and in reaching remote areas. However, satellites do not come close to the high bandwidth provided by optical fiber cables,” said Simon Webster, the U.K.-based director of submarine networks in Europe, Middle East, and Africa for NEC.
Undersea cables can transmit data at incredible speeds, exceeding terabits per second, enabling near-instantaneous global communication.
Basic fiber “is an extrusion of glass at a very high purity that is built into a robust structure,” explained Pete Kohnstam, sales director for the U.S. market at Nexans Subsea Operations, which manufactures and installs cables globally. Nexans is headquartered in Paris, with manufacturing facilities in Charleston, S.C., Norway, and Belgium, and offices in New York and Houston.
A fiber optic cable consists of many strands of glass or plastic fiber optic cables packaged in ribbons. For example, an 864-count package consists of 36 ribbons each containing 24 strands of fiber as thin as a human hair. A jacket made of plastic such as PVC, polyethylene, polyurethane, or polyamide protects the bundles.
“The cable is very specifically designed,” said Kohnstam, an electrical engineer by training. “The fiber is the same as those used on land—it’s how you protect it from its environment.” The inner optical core is also encased within a high tensile steel strength member clad within a copper power conductor.
“The power conductor powers the multiple amplifiers typically required en route to periodically boost the optical signal in each fiber, and you must protect all this from the external environment,” Webster added.
A snapshot of the interactive Submarine Cable Map maintained at submarinecablemap.com showing the current network of underwater fiber optic cables. Last updated in July 2025, this interactive map is based on data found in TeleGeography’s Transport Networks Research Service. Image: Telegeography’s Submarine Cable Map
A model of a deepsea fiber optic cable along the seabed, transmitting internet signals and electricity. Photo: Getty
A MAJOR EFFORT
A lot goes into planning a new cable that will cross an ocean. Surveys identify a safe route using bathymetry and geotechnical, sub-bottom, and side-scan data. Once the route survey is complete and the cable system design is finalized, the cable is manufactured. When complete, it is loaded on a cableship, or cable layer, for deployment.
Placing a cable that spans several thousand miles across an ocean comes down to manufacturing and logistics. Extruded pieces are often several miles long. The length of the cable dictates the number of trips a cableship makes back and forth between the mid-ocean end point and the factory and landing on either end, splicing the pieces on as they go. Cable is typically buried in the seabed in shallow water near shore but rested on it at depths further out.
But no matter how carefully planned, designed, manufactured, and installed a cable is, things happen, and cable repairs are often necessary. Fortunately, there is enough redundancy in the world’s cables to make it nearly impossible for a well-connected country to be cut off. On average, breaks happen every other day, about 200 times a year.
Cable faults result from both human-made and natural events. In water depths greater than 1,000 meters (3,370 feet), faults are almost always caused by natural events such as underwater seismic activity, landslides, or current abrasion. In water depths less than 200 meters (656 feet), faults are usually caused by human activities such as fishing and anchoring. Occasionally, geopolitics and sabotage enter the realm of undersea cables. “Smaller countries often can’t afford cables, as installing them is very expensive. There are territorial issues. The Red Sea is a superhighway,” Jamieson said.
In late 2024, a Russian ship was accused of dragging its anchor across the bottom of the Baltic Sea for 60 miles and damaging a cable that runs from Estonia to Finland. Cable systems are monitored constantly so when a system becomes faulty, it is known immediately. The staff in the cable stations at each end of the cable system conduct a series of tests to locate the fault.
Siem Offshore’s Anchor Handling Tug Supply Vessel (AHTS) Siem Ruby cleared rocks and boulders along a proposed subsea cable route near Wick, Scotland, for the Caithness-Moray project in March 2017. Photo: Getty
By having the cable landing stations on either side of the ocean beam light down their end of the line and time the reflections back, they can locate the faults within a few meters. To repair a cable, a cableship mobilizes. These are placed at strategic locations worldwide and are on 24-hour standby to carry out repairs.
Upon arriving at the suspected cable fault location, the repair vessel will attempt to localize the cable fault further by using various techniques and equipment such as electroding, a remotely operated vehicle (ROV), or side-scan sonar.
The cableship will then recover the cable. The ship grapples for the cable using a large cutting grapnel—basically a hook—towing it along the seabed until it catches the cable.
A broken cable is then fixed on the maintenance vessel deck by patching the break with a piece of new cable. However, since the break is miles away on the ocean floor, this must be done in several steps. After completing the splice, crews will rebury the cable on the seafloor using the ROV. For much of the 20th century, cable maintenance wasn’t a separate business. Vertically integrated telecommunication monopolies did it as part of their everyday business. As they started laying coaxial cables in the 1950s, they decided to pool resources. Rather than each company having its own repair vessel mostly sitting idle, they divided the oceans into zones, each with a few designated repair ships. “Possibly the biggest challenge facing the industry is the fact there are a limited number of cable installation and repair vessels and a lot of demand for their services,” Webster explained. In addition, few people set out to join the profession, mostly because few people know it exists.
There are 77 cable ships in the world, according to SubTel Forum, a trade publication, but most are focused on the more profitable work of laying new systems. Only 22 are designated for repair, and it’s an aging fleet. Boats are often converted tugboats or ferries. With the advent of offshore wind farms around the world, more power cables are springing up to interconnect wind towers and carry the power to land masses. This leads to the distinction between data cables for fiber optics and power cables for renewable energy.
“Cables for wind farms carry much higher voltages. Copper or aluminum is used for transmitting power. These are 8 to 10 inches in diameter, and the conductor itself is 3 to 4 inches for copper. They are very substantial,” Kohnstam said. “We’re providing the cable for the first wind farm in the States, the Southmore project in Long Island. We’re working with customers to bring power to Europe right now.”
A submarine cable repair ship. Photo: Getty
OPPORTUNITIES AVAILABLE
Optical engineers are always working on new technologies to keep up with global bandwidth demand and transmit data faster, further, and cheaper, Burdette explained.
“In recent years, the focus has been on multicore fiber, and how packing multiple cores into each optical strand might increase bandwidth outputs,” he said. “This of course also involves reconfiguring optical amplifiers, which are attached to ‘repeatered’ cables that carry signals across long distances. Folks are also interested in expanding the band of wavelengths that can be used to send optical signals.”
As Webster sees it, the next technological challenge for some of the hyperscalers is to get to petabit-per-second transoceanic subsea cables—a petabit equals one quadrillion bits. The Anjana transatlantic cable will deliver about half that capacity, based on a high fiber count.
How to double that? There are three main possibilities: double the number of fibers to 96 individual strands, double the number of data-carrying cores per fiber with new fiber designs, or double the bandwidth of each core with novel optical amplification techniques. The race is on, and the winners may reveal themselves within the next couple of years.
But the subsea cable industry has “been a small niche area for a long time. The skillsets are not typically widely available on the market. It doesn’t get the headlines some of the other industries do. So, it’s always a challenge bringing folks in. For us, engineering is one of the bottlenecks,” Kohnstam said. As for which engineering disciplines are necessary in the field, “You name it,” Jamieson said. “They are telecommunication engineers, civil engineers, and mechanical engineers. I’m a civil engineer originally, but I cross-pollinated into a telecommunications engineer.”
Webster envisions jobs emerging all across the sector, from engineering to project management to sales. “Yes, there will definitely be a need for more engineers, including those brave souls who are willing to leave their desks and get on board a cableship,” he continued. “Less adventurous types—like me—will also be needed in fields such as electronics, optics, materials science, and production engineering, to name a few. My first degree was in physics and my master’s was in electrical engineering.”
Getting more young people involved and training them is on everyone’s mind. For example, Nicole Starosielski, a film and media professor at the University of California at Berkeley, has developed a curriculum to teach students about submarine cabling and internet infrastructure. She conducts research on global internet and media distribution and communications infrastructures ranging from data centers to undersea cables.
Some organizations in the industry are actively promoting careers in the cable industry. TeleGeography, for one, has a summer internship where students are trained in all things telecom, Burdette said. “It’s not uncommon for young people to be totally blind to Internet infrastructure but become very interested in the topic after learning about it,” he added.
Kohnstam agreed: “It's an interesting world to be in.”
Tom Gibson, P.E., is a consulting mechanical engineer specializing in machine design, sustainability, and recycling and a freelance writer specializing in engineering, technology, and sustainability. He is based in Sugar Grove, Va.
Engineering professionals collaborating on telecommunications and subsea cable projects, reflecting the industry’s demand for diverse technical expertise. Photo: Getty
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