How One Submarine Cable Carries 99% of Internet Traffic Between Continents
How One Submarine Cable Carries 99% of Internet Traffic Between Continents
There are approximately 550 submarine cables spanning 1.4 million kilometers on the ocean floor, carrying 99.5% of all international data traffic. Not a single bit of your Netflix stream, Google search, or WhatsApp message between continents travels through satellites — it goes through hair-thin glass fibers buried in mud at the bottom of the ocean. The submarine cable network is the most important and least visible infrastructure on Earth.
The Scale
- 550+ cables in operation worldwide
- 1.4 million km of cable (enough to circle the Earth 35 times)
- 99.5% of international internet traffic travels via submarine cables (not satellites)
- $50 billion total investment in the cable network
- 10-15 new cables deployed per year
- Typical cable: 25mm diameter (about the thickness of a garden hose)
- Individual fiber: 125 micrometers diameter (thinner than a human hair)
- Each fiber carries 25+ terabits per second (one fiber can stream 5 million HD videos simultaneously)
- A single cable contains 4-16 fiber pairs = 100-400 terabits per second per cable
How Cables Work
Cable construction (from outside to inside):
- Polyethylene sheath: Waterproof outer layer (2-3mm)
- Steel wire armor: 1-2 layers of steel wire for protection against anchors and fishing trawlers
- Copper/aluminum conductor: Carries electrical power to repeaters
- Water-blocking tape: Prevents water ingress if cable is damaged
- Steel strength member: Provides tensile strength for cable laying
- Fiber optic core: 4-16 pairs of glass fibers, each thinner than a human hair
Signal amplification:
- Light signals degrade after 50-100 km (attenuation)
- Repeater stations every 50-100 km amplify the signal
- Repeaters are powered through the copper conductor (up to 15,000 volts DC)
- Modern repeaters: Fully optical (no electrical conversion needed)
- Cable power is supplied from landing stations on both ends
- Total power for a transatlantic cable: 10,000-25,000 watts
The Big Cables
MAREA (Microsoft + Facebook, 2018):
- Virginia Beach, USA → Bilbao, Spain (6,600 km)
- 160 terabits/second capacity (enough to stream 71 million HD videos simultaneously)
- 4 fiber pairs x 40 Tbps each
- Cost: $300+ million
- Laid in 2017 by the cable ship CS Responder
2Africa (Meta, 2024):
- Circumnavigates the African continent (45,000 km — longest cable ever built)
- 180 terabits/second capacity
- 16 fiber pairs
- Connects 33 countries in Africa, Europe, and the Middle East
- Cost: ~$1 billion
- Owned by Meta (Facebook) with consortium partners
FLAG (Fiber-Optic Link Around the Globe, 1997):
- UK → Japan via Mediterranean, Suez Canal, Indian Ocean (28,000 km)
- One of the first truly global cables
- Still partially operational
- Showed that global internet was economically viable
Why Not Satellites?
- Speed of light in fiber: 200,000 km/s (2/3 of vacuum speed due to refractive index)
- Speed of light to GEO satellite: 300,000 km/s (vacuum), but satellite is 36,000 km away (round trip: 72,000 km)
- Fiber latency London-NYC: 76 ms
- Satellite latency London-NYC: 250+ ms (round trip to satellite and back)
- Fiber is 3x faster for latency-sensitive applications
- Satellite capacity is a fraction of cable capacity
- Starlink uses cables for international traffic — satellites serve last-mile only
- LEO satellites (Starlink) have lower latency (~40ms) but still can't match fiber for intercontinental traffic
Vulnerabilities
Physical threats:
- Shark bites: Yes, sharks are attracted to the electromagnetic field of cables (rare but documented)
- Ship anchors: The #1 cause of cable damage (dropped anchors, dragging anchors)
- Fishing trawlers: Bottom trawling can snag and break cables
- Natural disasters: Earthquakes, submarine landslides, underwater volcanic activity
- Human sabotage: Only 3 confirmed cases, but a growing concern (Russia, China naval activity near cables)
Recent incidents:
- 2022: Three cables in the Baltic Sea were severed (sabotage suspected — linked to Nord Stream pipeline explosion)
- 2023: Red Sea cables damaged (Houthi attacks on shipping)
- 2024: Taiwan earthquake severed multiple cables to the island
- Cable repairs take 2-8 weeks and cost $1-3 million per repair
- Only 50 specialized cable repair ships exist worldwide
Who Owns the Cables?
- Tech giants now dominate: Google, Meta, Microsoft, and Amazon own or co-own 50%+ of new cables
- Historically: Telecom consortiums (multiple telcos sharing a cable)
- Shift: Big Tech is building private cables because leasing capacity from telecoms is too expensive at their scale
- Google: Owns 20+ cables (Dunant, Curie, Grace Hopper)
- Meta: Owns 15+ cables (MAREA, 2Africa, Amitié)
- China: Rapidly building its own cable network (PEACE cable, EMA cable)
- Geopolitics: Cable routing is now a national security issue
Fun Facts
- The first submarine cable: 1850 (telegraph cable across the English Channel)
- The first transatlantic cable: 1858 (Queen Victoria sent a message to President Buchanan — it took 16 hours)
- Cable ships are among the most specialized vessels on Earth (GPS-guided cable laying at 10 km/hour)
- Map of submarine cables looks like a nervous system diagram of the planet
- Total weight of all submarine cables: 10+ million tons
The Takeaway
The entire global internet — every video call, every search, every transaction between continents — depends on hair-thin glass fibers buried in mud at the bottom of the ocean. Satellites carry less than 0.5% of international traffic. The 550 cables spanning 1.4 million km are the most critical and least visible infrastructure on Earth. They're also vulnerable — to ship anchors, fishing trawlers, earthquakes, and increasingly, geopolitical sabotage. The next time you stream a video from another continent, remember: it's not coming from space. It's coming from a glass fiber, 4,000 meters below the ocean surface, powered by 15,000 volts, amplified every 80 kilometers, and laid by a ship moving at 10 km/hour through the abyss.