The hidden network that makes the internet possible Sajan Saini
In 2012,
a team of Japanese and Danish researchers
set a world record,
transmitting 1 petabit of data—
that’s 10,000 hours of high-def video—
over a fifty-kilometer cable, in a second.
This wasn’t just any cable.
It was a souped-up version
of fiber optics—
the hidden network that links our planet
and makes the internet possible.
For decades,
long-distance communications
between cities and countries
were carried by electrical signals,
in wires made of copper.
This was slow and inefficient,
with metal wires limiting data rates
and power lost as wasted heat.
But in the late 20th century,
engineers mastered a far superior method
of transmission.
Instead of metal,
glass can be carefully melted and
drawn into flexible fiber strands,
hundreds of kilometers long
and no thicker than human hair.
And instead of electricity,
these strands carry pulses of light,
representing digital data.
But how does light travel within glass,
rather than just pass through it?
The trick lies in a phenomenon known
as total internal reflection.
Since Isaac Newton’s time,
lensmakers and scientists have
known that light bends
when it passes between air and
materials like water or glass.
When a ray of light inside glass hits its
surface at a steep angle,
it refracts, or bends
as it exits into air.
But if the ray travels at a shallow angle,
it’ll bend so far that it stays trapped,
bouncing along inside the glass.
Under the right condition,
something normally transparent to light
can instead hide it from the world.
Compared to electricity or radio,
fiber optic signals barely degrade
over great distances—
a little power does scatter away,
and fibers can’t bend too sharply,
otherwise the light leaks out.
Today, a single optical fiber carries many
wavelengths of light,
each a different channel of data.
And a fiber optic cable contains hundreds
of these fiber strands.
Over a million kilometers of cable
crisscross our ocean floors
to link the continents—
that’s enough to wind around the
Equator nearly thirty times.
With fiber optics,
distance hardly limits data,
which has allowed the internet to evolve
into a planetary computer.
Increasingly,
our mobile work and play rely on legions
of overworked computer servers,
warehoused in gigantic data centers
flung across the world.
This is called cloud computing,
and it leads to two big problems:
heat waste and bandwidth demand.
The vast majority of internet traffic
shuttles around inside data centers,
where thousands of servers are connected
by traditional electrical cables.
Half of their running power
is wasted as heat.
Meanwhile, wireless bandwidth demand
steadily marches on,
and the gigahertz signals used in our
mobile devices
are reaching their data delivery limits.
It seems fiber optics has been too good
for its own good,
fueling overly-ambitious cloud and mobile
computing expectations.
But a related technology, integrated
photonics, has come to the rescue.
Light can be guided not
only in optical fibers,
but also in ultrathin silicon wires.
Silicon wires don’t guide light
as well as fiber.
But they do enable engineers to shrink
all the devices in a hundred kilometer
fiber optic network
down to tiny photonic chips that plug
into servers
and convert their electrical signals
to optical and back.
These electricity-to-light chips allow for
wasteful electrical cables in data centers
to be swapped out for
power-efficient fiber.
Photonic chips can help break open
wireless bandwidth limitations, too.
Researchers are working to replace mobile
gigahertz signals
with terahertz frequencies,
to carry data thousands of times faster.
But these are short-range signals:
they get absorbed by moisture in the air,
or blocked by tall buildings.
With tiny wireless-to-fiber photonic
transmitter chips
distributed throughout cities,
terahertz signals can be relayed over
long-range distances.
They can do so via a stable middleman,
optical fiber, and make hyperfast
wireless connectivity a reality.
For all of human history,
light has gifted us with sight and heat,
serving as a steady companion while we
explored and settled the physical world.
Now, we’ve saddled light with information
and redirected it
to run along a fiber optic superhighway—
with many different integrated
photonic exits—
to build an even more expansive,
virtual world.