Cables
or: lasers on the ocean floor for dog videos
We make glass so pure you could see through miles of it, pull it into strands thinner than a hair, wrap them in armor so sharks stop biting them, and lay hundreds of thousands of miles of it across the ocean floor, some of it nearly five miles deep. Then we flash lasers through it in dozens of colors at once, with amplifiers on the seabed boosting the light so it can cross an entire ocean faster than you can blink.
How it works, badly
We make glass so pure you could see through miles of it.
We lay it across the ocean floor, sometimes miles deep.
We armor it, because sharks. Then lasers go through it.
Then we use it to send each other dogs falling off couches.
Wait, is that real?
Yes, sharks included, sort of.
The glass
Optical fiber is ultra-pure silica glass. The light travels through a core about 9 microns wide; a human hair is roughly 70. It’s so clear that light can travel dozens of miles through it before it needs a boost.
The ocean floor
More than 600 submarine cables are active or planned, and the ones in service add up to over 1.5 million kilometers, or more than 900,000 miles. In deep water a cable is about as wide as a garden hose; near shore, where anchors and fishing gear can hit it, it gets layers of steel armor. Specially built ships lay them from huge onboard spools, and some run through trenches around 8,000 meters, or nearly five miles, deep.
The lasers
Each fiber carries dozens of different laser colors at once, each one a separate data channel. Repeaters spaced roughly every 40 to 50 miles along the seabed amplify the light. A signal crosses the Atlantic in about 30 milliseconds; a blink takes 100 milliseconds or more. Satellites carry well under 1% of US international data capacity, so cables handle nearly all of it.
The fine print
Sharks really have bitten cables, and some operators wrapped cables in tougher sheathing because of it. But the armor is mostly for ships: dragged anchors and fishing gear cause about two-thirds of all cable faults, and from 2007 to 2014 fish bites, sharks included, caused zero recorded faults.