If you’ve ever built a tree fort
You’ve probably also tried to send a secret message to your friend
using Morse code and a flashlight.
And fundamentally, fiber optic networking works in the same way:
Encoding data, impulses of light that travel around the world,
carrying our phone calls, business conference,
and important internet data.
But, now hold on a second.
How exactly do you send light
over great distances
and still manage to extract information from it?
I mean, fiber optic cables have to carry light,
for literally, thousands of miles, like across oceans.
Yet, if you’ve ever shined a flashlight down a long hallway,
you’ll know that over any more than a short distance,
the light scatters,
and eventually becomes too dim to make out.
Well, that is where optical fibers come in.
Those really skinny tubes that make your Christmas tree look nice
without having to string up any messy lights,
have some special characteristics that allow them to work over incredible distances.
The main way that fiber optics behave differently than your flashlight
is that they take advantages of a physical phenomenon,
called Total Internal Reflection.
You see, a fiber optic system
doesn’t just shine light down any random hollow tube.
Instead, optical cables are made up of the core of glass or plastic,
surrounded by an outer layer called Cladding.
Both the glass and the cladding have an inherent property,
called a refractive index,
which is basically a measure of how fast light can travel through something.
For the system to work properly,
the cladding needs to have a slightly lower index of refraction than the core.
Now sometimes this is achieved by using
pure glass that is silicon dioxide for the core,
and then doping the cladding with chemicals to lower its refractive index
while other times,
the core itself can be doped to raise the same value.
Either way, this difference means
that if light hits the cladding at a shallow enough angle,
it would be completely reflected at the same angle
instead of passing through the cladding.
That means that it can continue on down the fiber
in a zigzag pattern indefinitely.
Well, not quite.
Although in theory, the optical signal should
just keep going all the way until it reaches the other end of the fiber.
The pesky real world
always has a way of throwing a wrench in the pudding.
No matter how high-end and pure an optical cable is,
there will always be some imperfections,
even if they are so small
that you could only see them at the molecular level.
And these will cause some of that light to scatter,
weakening the signal over distance until eventually
it can’t be understood by the equipment at the other end.
So, to combat this,
long distance fiber runs are assisted by Repeaters or Amplifiers.
A repeater gets placed at a point down the fiber
where the signal will have weakened significantly,
but it’s still strong enough to be read.
Once the light hits the repeater,
it’s turned into the corresponding electronic signal,
which is then turned back into light
much as it was at the origination point
and then sent along on its merry way.
Repeaters come with a latency
and a complexity cost though.
So many modern long-distance systems now use amplifiers instead.
These gadgets have optical fibers which are doped with chemicals
that directly amplify light when the weakened signal hits them.
So the ions in the fibers themselves
will re-emit the same signal,
but much more strongly than what came in,
and it continues down the cable.
In this way, optical fibers runs can be designed to be really long,
making them a more viable choice for long distance communication than copper.
Optical fibers are not only more cost effective than copper wiring,
it’s more power efficient,
and it even goes farther without requiring a boost.
Also, because it’s thinner,
and doesn’t cause electromagnetic interference to the cables around it.
It’s common to bundle a bunch of optical fibers,
each of which can carry multiple wavelength of light,
into one large cable,
making it possible to transmit enormous amounts of data
without taking up too much space.
This versatility means that fiber optics have found uses outside of just communication,
such as an endoscopy,
where the flexibility allows a user to light up,
and view inside very hard-to-reach spaces.
This is useful in fields like engineering, plumbing, and even medicine.
Speaking of which,
I got to run and get to a doctor’s appointment,
and hopefully doesn’t involve sticking a fiber optic scope up somewhere embarrassing.
Oh, I know what the doctor ordered.
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If you’ve ever built a tree fort