Remember that time I made a video about TOSLINK?
I sure do, it was just last week!
(almost)
Well, before I ended that video, I left you with a question.
Why haven’t we seen fiber...
*THUNDER CLAP*
[ominous music]
You’ve angered the Hi-Fi gods!
You said TOSLINK is impervious to electromagnetic
interference
“but what does that matter in the digital space?”
But you didn’t mention ground loops and
the devastation they cause!
OK, OK, just, settle down!
I’ll address that.
Right now!
When you connect two pieces of equipment with
an RCA cable,
you also connect their respective grounds together.
In some circumstances, this can create audible
humming or buzzing because even though the
signal being sent is digital, the amplification
circuitry is not.
Because it is connected to ground, if there’s
an imbalance between the two grounds of the
sending and receiving equipment, that creates
a current in the ground of the signal wire
which can affect the analog amplification
circuitry.
Because TOSLINK is an optical signal, the
two devices are galvanically isolated and
it doesn’t matter in the slightest if there’s
a ground imbalance.
TOSLINK is, in effect, an opto-isolator and
this benefit should not be ignored.
Now, I would like to provide an explanation
for my careless oversight.
For every person who touts the benefits of
TOSLINK, there’s another that complains
about clock jitter.
Those individuals claim that if you’re encountering
a ground loop, “for the love of god don’t
use TOSLINK with all its totally real imperfections,
sort out that problem you heathens!”
Audio forums are worse than Twitter, each
of you likes what you like and anytime anyone
presents any opinion regarding the pros and
cons of one system over another,
y’all lose your minds and get real pretentious and I’m
just kinda over that.
I, admittedly, chalked up the concern for
ground loops to be one of those opinions,
but it’s not.
TOSLINK can, does, and has many times presented
a meaningful solution to the problem of ground
loops or other electrical noise issues, and
it may in fact be the entire reason Toshiba
developed it.
It is interesting to note, however, that the
ground loop problem seems to have gone away
in the age of HDMI.
Whether that’s down to better isolation
inside the equipment itself or some other
thing, it suggests that the problem could
have been solved without going to an optical fiber.
It may have just been easier (and, let’s
not forget, cooler) to use TOSLINK.
Alright, now that that’s taken care of,
let’s get back to the question at hand.
With TOSLINK being developed in 1983, why
haven’t we seen fiber...
*THUNDER CLAP*
You’ve angered the IT gods!
You referred to CAT5 cable as Ethernet!
You fool!
Ethernet is a standard series of protocols
and fiber optic cabling is routinely used
in larger networks!
You’re right.
I am but a lowly network plebeian, barely
capable of setting up a WiFi router.
Forgive my callous equation of Ethernet and
that cable.
It won’t happen again.
Wow, we’re almost three minutes into this
and we haven’t even gotten to the question at hand.
So.
Why haven’t we seen fiber optics in the
consumer space aside from TOSLINK?
Actually, in some very niche circumstances
we have, and as the IT gods reminded us, it
does exist in big networks, but I’m talking
on a broader, more basic scale.
Your average consumer is probably familiar
with things like USB, HDMI, DVI, DisplayPort,
Thunderbolt, Eth..., I mean, Cat 5 cabling
with 8P8C (often incorrectly referred to as
RJ45) connectors, and maybe FireWire or SATA
or perhaps other things.
All of these use wires, like some sort of
technologically regressive lazy person.
Why not use light?
Well, let’s start with the obvious thing.
TOSLINK works great for connecting pieces
of audio visual gear together because each
one will have its own power source.
All that needs to get sent between them is
a little bit of data.
But lots of things need power, too.
Have fun using that keyboard and mouse connected
to your computer by nothing but light.
And, as we moved away from the days of RS-232
serial connections and into the holy land
of the Universal Serial Bus, suddenly we found
that we’re not sending little bits of power
just to keep your mouse alive.
We’re sending loads of it.
I don’t want to go off on too much of a
tangent here...
Oh who am I kidding I do this all the time.
It seems like USB turned into the power delivery
standard it is today kinda by accident.
Remember that even in USB 2.0 days, officially
a device could only draw 2.5 watts, and that
was considered high power.
In those wild west days, different companies
were coming up with their own ways to determine
the current a given port could supply, and
it wasn’t until 2007 that the first USB
Battery Charging specification appears, finally
getting everyone on the same page and allowing
for USB ports on computers to finally, officially,
provide more than 500ma when asked nicely.
Anyway, now that USB is ubiquitous, we can expect
any modern device to provide a decent amount
of power through its USB ports for things
like portable hard drives, charging your phone,
and of course the monumentally important task
of powering all those RGB LEDs in that gaming
keyboard you bought because, you know, +5
Agility.
But you may recall that the switch from USB
2 to USB 3 didn’t just involve making the
data transfer go faster.
The 4 conductors of the USB cable weren’t
enough, so we had to add more of them for USB 3.
Five more, to be exact.
Add too many more and we might as well just
start using HDMI for everything.
But with fiber optics, we could potentially
have much, MUCH faster data throughput using
only a pair of optical fibers.
Or, potentially, just one if you, for instance,
send data in each direction using two different
wavelengths of light, and separate them with
a prism on each end.
So sure, we need to send power to devices
in addition to data.
Why not create some sort of composite cable
(no, not that kind)
a cable that is a composite
of both optical and electrical?
Like a USB cable where the data lines are
replaced with optical fiber?
Then, the same cable could be used for nearly
everything!
Alls we gotta do is just make the LEDs go
blinky blinky a little faster and we coulda
been using the same cables since the ‘80s!
Well, not so fast.
Heh.
Not so fast.
Optical fiber is complicated.
It doesn’t seem like it should be, after
all what are we really doing but flashing
a light source and moving it somewhere else
so we can see the flashing and decode it,
but thanks to … PHYSICS, it’s not actually
as simple as that.
Stupid physics.
Making everything difficult.
I don’t want to get too far down this particular
path because its importance to potential consumer
standards is arguably minimal, but it’s
important nonetheless.
Since light travels at the speed of…
light, it may seem as though a pulse of light down
an optical cable will reach the other end
in exactly the same way that it was sent.
But… it won’t.
Thanks to a phenomenon called modal dispersion,
also known as multimode distortion, multimode
dispersion, modal distortion, intermodal distortion,
intermodal dispersion, and intermodal delay distortion
(jeez guys pick a name already)
the signal actually gets a little smeared.
Let’s imagine we send a pulse of light down
this optical fiber.
Will it all get to the other end at the same
time?
It seems like it should, it’s light after
all.
But just because something happens as fast
as we know things can happen doesn’t mean
geometry doesn’t apply.
If the individual photons in that pulse of
light manage to stay perfectly parallel to
the sides of the fiber, they will all arrive
at the other end simultaneously.
But this is the real world, and nothing’s
perfect.
Some of them are gonna enter the fiber at
an angle, which means they don’t take a straight path.
They bounce off the sides, and although total
internal reflection keeps them from leaving
the fiber, this zig-zag path is much longer
than a straight line so those meandering photons
will in fact arrive later.
And this limits the speed at which we can
pulse the light on and off and still have
it be intelligible on the other end.
This is that smearing of the signal.
Even though on the sending end we’re putting
in a clear-cut, on-off signal, on the receiving
end the photons who lollygagged and bounced
around in the fiber cause the signal to look
like this.
Some of the photons from the last pulse manage
to arrive at the same time as some of them
from the next one.
So, we have to limit the frequency at which
the pulses happen in order to make the received
signal decodable.
This means that optical fibers do actually
have a bandwidth limit.
Just because we’re using fiber optics doesn’t
mean we have theoretically endless upgrade capacity.
That said, you might have already surmised
that the bandwidth limit depends on how long
the optical fiber is.
No matter how poorly the light behaves in
the pipe, if it’s a short pipe then the
time difference between straight-and-true
photons and disastrously off-course photons
is quite small.
And this is why discussing the bandwidth limitations
of a given optical fiber is not really a big
deal if we’re dealing with consumer applications
where cables aren’t likely to go beyond
10 meters.
But, since it’s interesting, let’s get
into how we deal with bandwidth limits anyway.
In the land of fiber, there are two basic
kinds of fiber optic cabling.
Single-mode fiber, and multi-mode fiber.
Now, mode here doesn’t mean a method of
operation.
Here it means the field pattern of propagating
electromagnetic waves.
Ideally we want the light to travel only in
the transverse mode, and that’s what single-mode
fiber allows us to do.
It accomplishes this by having a very small
internal diameter, what we in the business call
itty bitty.
Generally it’s between 8 and 10 micrometers
across.
This tiny size of the fiber allows the pulses
to remain distinct over longer distances because
the light traveling through the fiber mainly
stays in the transverse mode.
Because of this, long-distance links on the
order of thousands of kilometers are usually
done with single-mode fiber.
But, single-mode fiber is really finicky to
deal with, requiring special tools to make
connections since it’s so darn small.
So for applications involving shorter fiber
runs, like networking a building, we’ll
use much easier to deal with multi-mode fiber.
This thicker fiber allows us to make cable
terminations more easily at the cost of a
messier signal on the other end.
Still, it’s a fair bit of bandwidth.
Using just LEDs, gigabit speeds are easily
achievable.
And if we get into higher-grade fibers and
start using lasers as transmitters, we can
get 100 gigabit speeds over distances on the
order of 100 meters.
And remember, the shorter the run, the easier
it is to achieve high bandwidth.
But if we’re talking about a fiber like
TOSLINK, well that’s nothing like even multi-mode fiber.
It’s actually in a third category.
Generally TOSLINK is a plastic optical fiber.
It’s much thicker inside, about a hundred
times thicker than single mode fiber, so it
exhibits much greater modal dispersion, and
thus its bandwidth limit is much lower.
But how much lower is it, really?
I mean, shorter lengths make the bandwidth
go up, so even though that fishing line in
there has wicked bad modal dispersion, over
just a few meters it shouldn’t matter much, right?
Right!
In a 2009 paper by Yasuhiro Koike, the possibility
of using plastic optical fiber for high speed
networking was explored.
By using different modulation methods, it
was found that plastic fiber could easily
achieve gigabit speed at lengths up to 100
meters.
And, with the development of graded-index
plastic fiber, 40 gigabit speeds were achieved.
Pretty impressive.
But, now we’re stepping into messy territory.
Let’s rewind a bit.
Graded-index plastic optical fiber is a new
development.
And the question I’m getting at here is
why haven’t we been using fiber forever?
Imagine that in 1985 we had come up with one
standard cable, like a bidirectional TOSLINK
cable with a pair of power wires running through
it.
I’ll call it UniLINK.
Could we have been simply been using the same
cable to replace the functions of all these,
and had a future-proof design because the
speed could simply be boosted with each new
generation of hardware?
Well, maybe.
A TOSLINK cable with a 10 meter length could
perhaps pull off 10 gigabit speeds.
And so, if we had designed a cable like my
theoretical UniLINK cable, then perhaps we
could have simply had one cable to rule them
all.
Oh, and wouldn’t ya know it, I found this
product guide from Toshiba and it turns out
that TOSLINK did have a few bidirectional
connectors out there.
They are generally limited to professional
and niche applications like automation control,
but this high-speed TOSLINK connection is
capable of a quarter gigabit at 20 meters.
Not too bad, and I don’t doubt that could
be improved.
But, well, now here’s where the heavy weight
of reality steps in.
As the old adage goes, just because you can
doesn’t mean you should.
It may seem silly to use such complicated
cables when commercial fiber optic links are
now pushing past terabit speeds, but just
looking at the various connectors and cables
we’ve used through the ages doesn’t really
explain what they’re doing.
An HDMI cable doesn’t have 19 conductors
running through it for grins and giggles.
Most handle the video data in various ways,
but others handle things like the audio return channel
(and notably that pin was unused in
early versions of the standard), the display
data channel which allows displays and whatever
they’re plugged into to get a nice introduction
and learn their respective preferences (also
this is where HDCP runs along for the ride),
a 5v power supply, the consumer electronics
control which is what allows other devices
to turn on and off your TV for you, and many
of these pins have been given more and more
tasks as HDMI has matured and improved.
Could we do all of that with one single fiber
optic cable?
Perhaps.
Though HDMI 2.1 has a total bandwidth of 48
gigabits per second, which might not be possible
with plastic fiber at all.
Or at least, only over relatively short distances.
See, it’s interesting to think about the
blazing fast speeds fiber optics allow, but
a super fast serial datastream isn’t necessarily
useful for driving the pixels of an LCD panel
in a logical fashion.
And therein lies the problem.
We have a bunch of different cables to deal
with because they’re all designed to do
specific things in specific ways.
The end!
♫ unexpectedly smooth jazz ♫
Just kidding!
Though, that pretty much is the answer.
At a very fundamental level, they’re all
carrying power and data.
But how that data should best be transported
depends on what kind of data it is and what
we want to do with it.
As new standards came up, their cables were
designed to address those needs.
And oftentimes the best way to take care of
a specific need is to add another conductor
for doing just one thing.
So, while we could just send everything over
a high-speed fiber connection, the extra processing
that might be required on each end can make
the whole idea more complicated, and expensive.
And so, new cables for new applications often
make the most sense.
If you can simplify the data processing with
a more complicated cable, it’s often worth it.
And now, I’m about to shoot that argument
in the foot.
Did you know that there are HDMI cables which
are actually fiber-optic?
If you need to run an HDMI cable over a very
long distance, one of the easiest ways to
do it is to take an HDMI signal, convert it
to a fiber optic data stream, send it over
a fiber however long you need, and convert
it back to HDMI on the other end.
Commercially available products can do all
that in what looks like any ordinary HDMI
cable that just happens to be very long.
These cables actually cheat a little bit and
have four fibers going through them, probably
one for each of the three sets of data lines
and the fourth for the clock signal that a
normal HDMI cable carries, to make encoding
and decoding easier, but they demonstrate
that the actual hardware required to convert
to fiber and back again isn’t that complex.
It all fits inside these connectors.
Back in 2014, LinusTechTips demonstrated a
USB 3.Optical cable from Corning that, well
did the same thing but for USB.
The tech to convert to optical and back was
a little more expensive at the time, but it
still all fit in modules barely larger than
your basic flash drive.
So, what’s the deal then?
What exactly is stopping us from using a UniLINK
hybrid power and optical cable for everything?
Um, nothing.
Except of course for all the other cables
we already have.
This is why I love looking at technology through
a historical lens.
TOSLINK is surprisingly old for what it is,
but at the same time it’s kinda in its own little corner.
Consumers haven’t needed fiber optics for
bandwidth reasons until very recently, so
unless there was some reason electrical isolation
was absolutely necessary, using a pair of
copper wires was sufficient.
So, throughout the rise of the digital age,
we just kept on going with copper.
Because it worked.
Lots of technological progress comes from
using existing things in new ways.
Just look at how we first got the Internet
into our homes--using ordinary telephone lines!
[dial-up modem sounds] 
Just by calling a specific phone number and having
your computer screech at another one, you’re online!
And then, we adapted those phone lines into
basic broadband using DSL, and if you’ve
got cable Internet, you’re getting your
memes over the same coaxial cable that’s
been delivering ...must-watch television programming
for decades.
And it works!
Backward compatibility is also partly to blame
for keeping optical tech in the dark.
Like in the case of USB, more data lines were
added to the existing connector, rather than
create an entirely new one.
It was another case of using existing things
in new ways, though with a little more flair.
The only practical time to introduce an optical
standard is when creating an entirely new standard.
Speaking of creating entirely new standards,
Thunderbolt was almost optical.
In fact, it was originally called Light Peak.
But somewhere in the development process,
Intel realized they’d like to be able to
send power through these cables, and while
they pondered stealing my idea and bundling
copper wire with optical fibers, by 2011 they
gave up the fiber thing altogether, realizing
that copper worked just fine.
Though, it’s worth noting that in the development
stages, they were pushing 10 gigabits a second
through plastic fiber, and believed they could
get to 100.
Also of note is that, just like Corning’s
extra long optical USB cable, optical Thunderbolt
cables were a thing, but this hasn’t yet
become a reality for Thunderbolt 3.
Speaking of Thunderbolt 3, we do seem to be
headed towards a One Cable to Rule Them All future.
Or at least, maybe.
USB type C can do nearly everything we might
want a cable to do, and it can do it pretty well.
Nevermind how incredibly confusing the whole
situation is right now because the connector
is called USB type C but that doesn’t actually
mean anything in regards to what data can
go through that port or any specific cable
because the USB Implementers Forum sucks at
branding and bundling Thunderbolt into the
same thing as USB is making this mighty confusing.
Get it together, people!
So where does this leave us?
To put it simply, it’s complicated.
We do sort of see fiber optics in the consumer
space.
Though most of those implementations are indirect
and just a way of getting around cable length limits.
It doesn’t seem likely that we’d end up
with a TOSLINK-like cable that sends only
optical data, because we need copper to send
power, anyway.
And if we need some copper, why not just do
it all with copper?
I imagine that’s the conclusion Intel came
to in the development of Thunderbolt.
Will another attempt at creating a truly optical
standard find success?
Well, I’m doubtful.
Thunderbolt 3 and/or USB 3.2 or wherever we
are in this situation is probably way faster
than what any casual consumer is gonna need
for a while.
I won’t say ever, cause you just can’t
do that when it comes to tech, but then there’s
this other elephant in the room I haven’t
mentioned yet;
WiFi.
[in a Valley Girl voice] 
Wires are sooo yesssterday.
Why use a wire when I could live life untethered?
Ugh, so gross these wires.
I hate to break it to you, but your average
consumer is not your average enthusiast, and
so if there’s a wireless option, that’s
probably preferred.
Why do you think headphone jacks are going
away?
I mean, I was mad at OnePlus for ditching
it but today I rarely miss it.
So yeah.
There will always be a need for super-fast
wired connections in the professional space,
and lots of you enthusiasts out there love
to live in that same tier.
But let’s be honest.
You’re not the average user.
That’s not a bad thing, not at all!
But it deserves to be said.
For now, I imagine optical connectors will
stay right where they are.
Simultaneously at the very bottom with TOSLINK,
and at the very top with crazy fast networking equipment.
For everything else, copper’s pretty OK.
And for everything else else, microwaves are
fine, too.
And for those weird niche cases where we are
running fiber as a Frankenstein solution to
getting around a length limitation, well to
that I say, why not?
Thanks for watching.
There’s a lot I didn’t get to before ending
this video, so as these fine Patreon supporters
start scrolling up your screen, I’ll bring
a few of them up.
When we make long-distance fiber optic links,
we usually can’t send light all the way
from one end to the other because even the
best optical fibers do attenuate the signal
somewhat.
In the past, we used electronic repeaters
which simply read the incoming signal and
repeated it using another laser to enable
longer connections.
However, these days we use optical amplifiers
which use some physics magic to passively
make the light beam more intense without actually
creating a new beam of light.
Because you don’t need a bunch of active
devices repeating the signal along the fiber’s
length, you can speed up data transmission
within it.
I don’t understand the operating principle
of optical amplifiers well enough to provide
a good explanation of how they work, so if
anyone in the comments wants to take a crack
at it please do.
Also, I do want to point out a valid criticism
from the last video.
HDMI sure does have more audio bandwidth than
TOSLINK, but what if you only want to send
audio?
Since HDMI is primarily a video interface,
audio-only just isn’t a thing it does.
And, that’s a fair point.
However, when we’re dealing with multichannel
high-resolution audio, I think it’s fair
to say that we’re usually talking about
the home theater space, and that’s why I
was ignoring that potential use case.
Also!
The Audio Return Channel was until HDMI 2.1
limited to S/PDIF, meaning until very recently
TOSLINK and the ARC were essentially the same
thing, and since many people reported having
issues with the ARC, TOSLINK provided an alternative
with just-as-good audio and with better compatibility.
Now, though, the ARC is truly better, so assuming
you don’t run into problems, it leaves TOSLINK
in the dust.
Another fun little thing was that I did run
across some research looking into how to send
electrical power over optical fiber.
Yep, power over optical fiber is a thing,
but I can’t seem to find any specifications
on exactly how much power can be sent.
And I doubt it’s very much at all, though
I’m willing to be surprised.
And lastly, following along those lines, one
of the things that CAT5 cabling lets us do
is send power in addition to data over the
same lines.
This is called Power over Ethernet, and …
wait.
It’s called power over ethernet, eh?
Hmm.
How interesting.
Anyway, power over Ethernet allows for things
like powering wireless access points without
needing an A/C power source at the location,
providing power to IP phones in office buildings,
or any other such need.
And up to 50 watts!
That’s some powerful stuff, that Ethernet
is.
♫ abridgedly smooth jazz ♫
