Samanth Subramanian on the Undersea Cables That Keep the Internet Alive

Summary of Samanth Subramanian on the Undersea Cables That Keep the Internet Alive

by Bloomberg

42m•May 13, 2026
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Overview of Samanth Subramanian on the Undersea Cables That Keep the Internet Alive

This episode of Odd Lots explores the hidden physical infrastructure behind the internet: undersea fiber-optic cables. Host Tracy Alloway and Jill Weisenthal speak with writer and author Samanth Subramanian, whose book The Web Beneath the Waves examines how these cables are built, financed, repaired, protected, and increasingly shaped by geopolitics and big tech. The conversation makes the case that the internet is far less “virtual” than people assume—it is a vast, fragile, and highly physical system.

How Undersea Cables Work

From telegraph lines to fiber optics

  • The first transatlantic cables carried electric pulses through copper wire.
  • Modern cables are made of hair-thin purified glass fibers.
  • Data travels as pulses of light, which bounce through the glass and are decoded at the other end.
  • The system uses wave division multiplexing, allowing many data streams to travel through one cable at once.

How they’re laid

  • A survey ship first maps the route, taking into account ocean-floor geography.
  • A cable-laying ship then slowly unspools the cable from a giant spool or drum.
  • Speed matters: too fast risks snapping the cable; too slow creates slack.
  • The process is still surprisingly similar to the old telegraph era, even if the technology is vastly more advanced.

Who Pays for the Internet’s Backbone

A changing ownership model

Subramanian describes three major eras:

  1. State telecom era
    • Governments and state-owned telecom firms often formed consortia to fund cables.
  2. Private investor era
    • As telecoms privatized in the 1990s and 2000s, private capital took over more of the financing.
  3. Big tech era
    • Today, companies like Google, Meta, Amazon, and Microsoft are increasingly funding and owning cables themselves.

Why big tech matters

  • A transatlantic cable can cost around $500 million.
  • Big tech sees undersea cables as strategic infrastructure because their businesses depend on data flow.
  • This raises concerns about:
    • data privacy
    • data security
    • who controls internet access
    • which regions get served

Redundancy, Geography, and Vulnerability

The system is built with backups

  • There are roughly 500–550 undersea cables worldwide.
  • About 100 cables are cut each year, usually by accident.
  • Despite that, outages are limited because of:
    • redundant routes
    • backup land cables
    • multiple undersea cables serving the same region

Geography shapes the network

  • Cables tend to land in the same places historical telegraph cables did, because the infrastructure is already there.
  • Major choke points like:
    • the Suez Canal / Egypt
    • the Strait of Hormuz
    • the Red Sea
    • parts of Southeast Asia are strategically important because they concentrate global traffic.

The internet is not a highway

  • Data does not always take the shortest route.
  • Routing depends on network conditions, server location, and redundancy.
  • A cut cable in one region can force traffic to reroute globally.

Repairing Damaged Cables

Surprisingly old-school repair methods

  • Repair ships locate the damaged section and drag grapnel hooks along the seabed to snag the cable.
  • Once aboard, the cable is repaired in a stabilized onboard lab with clean-room conditions.
  • After splicing, the cable is carefully re-lowered into the ocean and tested repeatedly.

Geopolitics and Security

Sabotage concerns are rising

  • Most cable damage is accidental, but governments increasingly worry about intentional attacks.
  • Countries are responding with:
    • naval patrols
    • coast guard monitoring
    • heightened surveillance in sensitive regions

China-U.S. tensions are reshaping the network

  • Chinese firms like HMN Tech compete with Western cable contractors.
  • Sanctions and security concerns have frozen or delayed some projects.
  • In some cases, cables have been laid but not activated because of Chinese involvement.
  • The result may be a bifurcation of the internet, with separate cable ecosystems emerging in some regions.

AI and the Future of Cable Demand

AI accelerates, not replaces, cable growth

  • The rise of AI, cloud computing, and hyperscale data centers increases demand for bandwidth.
  • Subramanian argues there is no realistic post-cable, fully wireless future anytime soon.
  • Satellites help, but they cannot handle the sheer scale of global internet traffic.

Cycles of boom and bust

  • Cable deployment slows during recessions and resumes during expansions.
  • The dot-com bust created a temporary lull, but demand later surged again.
  • AI is now driving a new wave of infrastructure investment.

Notable Takeaways

  • The internet is not just software and cloud computing; it is a physical network of cables, ships, and landing stations.
  • Control over cable routes increasingly means control over access, speed, and influence.
  • Undersea cables are both remarkably resilient and highly vulnerable.
  • The future of the internet will likely be shaped less by a move away from cables than by who builds, owns, and protects them.

Closing Thought

The episode’s core insight is that the internet’s “invisible” global connectivity depends on an elaborate and fragile undersea system that is old in concept but central to modern life. As AI, geopolitics, and big tech intensify demand, undersea cables are becoming even more important—and more contested—than ever.