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In today’s world, where everything from social media to financial transactions happens online, data travels at lightning speed. But have you ever wondered how information moves between continents? Many assume satellites do the heavy lifting, but in reality, submarine cables carry over 99% of intercontinental data traffic. Yes, those fiber-optic cables lying deep under the ocean floor are the true backbone of global internet connectivity.
In this article, we’ll break down what submarine cables are, how they work, and why they dominate global data transmission.
What Are Submarine Cables?
Submarine cables are fiber-optic cables laid on the seabed, connecting different continents. They allow internet service providers (ISPs), businesses, and governments to exchange data seamlessly across the world.
These cables are typically made of bundled fiber-optic strands encased in multiple protective layers, including steel and waterproof insulation. Unlike old telegraph cables, today’s submarine cables use light signals to transmit data at incredibly high speeds.
How Do Submarine Cables Work?
The technology behind submarine cables is fascinating. Here’s how they function:
- Data Transmission Using Light – Fiber-optic cables transmit data as light pulses. Each pulse represents bits of information, traveling at nearly the speed of light.
- Amplifiers for Long Distances – Since light signals weaken over long distances, repeaters (amplifiers) are placed every 50–100 km along the cable to boost the signal.
- Landing Stations – When cables reach the shore, landing stations connect them to local internet infrastructure, distributing data to end-users.
Why Do Submarine Cables Handle 99% of Global Data Traffic?
Many people assume satellites play a major role in global internet traffic. While satellites are crucial for GPS, broadcasting, and remote connectivity, they cannot handle massive data loads efficiently. Here’s why submarine cables dominate:
1. Speed & Low Latency
Fiber-optic cables can transmit data at speeds exceeding 200 terabits per second (Tbps), whereas satellites struggle with higher latency due to their distance from Earth. Even the latest low-earth orbit (LEO) satellites like Starlink have a latency of 20–40 milliseconds, whereas submarine cables offer latency as low as 5–10 milliseconds.
2. Higher Capacity
Satellites have limited bandwidth, making them unsuitable for handling the enormous data volumes required for modern activities like video streaming, cloud computing, and global financial transactions. Submarine cables provide significantly higher capacity, making them the preferred choice for ISPs and tech giants.
3. Reliability & Cost Efficiency
Submarine cables are much more reliable than satellites. Once laid, they function for 25 years or more with minimal maintenance. In contrast, satellites have a shorter lifespan, require expensive replacements, and are vulnerable to space debris.
How Many Submarine Cables Exist Today?
As of 2024, there are over 550 active submarine cables, covering over 1.3 million kilometers globally. These cables connect nearly every continent, ensuring uninterrupted global connectivity.
Some of the most famous submarine cables include:
- Grace Hopper Cable – Owned by Google, connects the U.S., U.K., and Spain.
- MAREA Cable – One of the highest-capacity cables, backed by Microsoft and Facebook.
- SEA-ME-WE 6 – Connects Southeast Asia, the Middle East, and Western Europe.
Who Owns & Maintains Submarine Cables?
While telecom companies traditionally controlled submarine cables, big tech giants like Google, Meta (Facebook), Amazon, and Microsoft now own a significant share. These companies invest heavily in undersea cables to ensure fast and reliable connectivity for their services.
Challenges & Threats to Submarine Cables
Despite their advantages, submarine cables face some challenges:
- Natural Disasters – Earthquakes, underwater landslides, and extreme weather can damage cables.
- Human Activities – Fishing trawlers, ship anchors, and accidental cuts are common threats.
- Cybersecurity Risks – As critical infrastructure, cables are vulnerable to cyberattacks and espionage.
