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Our modern world essentially runs on fiber
optic communication technology.

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On our increasingly connected planet, nearly
everything we do from making a phone call,

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to checking our bank account balance, to yelling
at computers to tell them to turn the lights off,

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to watching this very video almost certainly
relied, at some point, on turning your voice,

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or input, or the data making this image into
incredibly brief, incredibly fast pulses of light,

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firing that light with *A LASER* down
a glass pipe, and counting the pulses

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on the other end.

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And probably doing that a whole bunch of times
over potentially thousands of kilometers,

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nearly instantaneously.

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And yet, in the consumer space, fiber optics
are almost nowhere to be found.

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We send digital video data over these complicated
cables with upwards of a dozen little strands

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of copper inside them.

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Networking equipment in homes and businesses
still uses Ethernet, twisted pairs of copper

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wire that need to be made more precisely
with higher tolerances each time we want

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to push the speed up another order of magnitude.

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Really, we just haven’t seemed to find a
place for fiber optics aside from piping the

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internet into your home or business, and even
then that’s not exactly common.

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Except there was that one time Toshiba
decided to connect CD players to amplifiers

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with fiber optics in 1983.

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Yes, although fiber optics may seem like the
upper echelon of communications technology

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(and in fact kinda are)

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there has been one consumer-grade fiber optic standard floating around since the early ‘80s.

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That would be TOSLINK, which is a shortening
of Toshiba Link.

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In this video, we’re going to learn a little
bit about this surprisingly old optical standard.

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Ahh, the compact disc.

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What a beautifully engineered medium for storing
uncompressed digital sound.

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As you likely know, these things store data
in millions of little pits and lands, and

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when you shine a focused laser on those bumpy
bits, the varying depth causes destructive

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interference and results in a reflected beam
that flashes light and dark, representing

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ones and zeroes.

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Note that a pit doesn’t mean 1 and a land
means 0, rather the transition from pit to

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land OR land to pit means 1, and a period
of no change means 0.

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A CD player has to do a fair bit of processing
before it can turn that raw data stream into sound.

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First it has to translate the eight-to-fourteen
modulation of the pits and lands to reveal

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8 bit words, then it has to parse the various
signalling within that datastream for things

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like track and time markers, and finally it
has to work through the cross-interleaved

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Reed-Solomon coding to actually get the individual
samples that make up digital sound.

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Once we’re at that step, we can send those
decoded samples to a DAC in order to be turned

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into electrical impulses that will drive headphones
or loudspeakers to impart mechanical impulses

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into the air that we hear as sound.

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If you’d like to learn more about the compact
disc and how digital sound works, you can

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check out these previous videos of mine.

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Now without a DAC, we can’t turn those samples
into sound.

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Since that’s the primary goal of a CD player,
the CD player itself contains a DAC, and generates

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a line level analog audio signal to be sent
to an amplifier over garden variety RCA cables.

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And for almost all intents and purposes, this
is perfectly fine.

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Unless you cross the line into audiophile
territory, you are probably delighted by the

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sound coming from these two little jacks.

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And so, for most of us, that’s the end of
the story.

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But the act of playing a CD is the very last
step in the life cycle of producing a sound

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recording on compact disc.

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In the studio, digital tape machines are creating
digital recordings from microphones or other

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analog sources, and various editing equipment
needs to access those recordings to be manipulated

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and eventually mastered into a compact disc.

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All of this is different today but just pretend
like it’s 1985, OK, everyone’s doing it anyway.

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Knowing that there’d need to be some standard
way to move digital audio streams around,

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Sony and Philips (the co-creators of the Compact
Disc standard) developed S/PDIF,

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which is often pronounced “spidiff” because, let’s
face it, that’s more fun.

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S/PDIF stands for Sony/Philips Digital Interconnect
Format, or you might also see

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Sony/Philips Digital InterFace.

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When Sony and Philips hammered out the details
on S/PDIF, they were using standard coaxial

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audio cables like these to send the digital
data over garden variety copper wires.

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And that worked fine!

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No one was complaining.

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But then, Toshiba got into the CD player business,
and they wanted to be able to send the raw

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digital sound data recovered from the CD separately
to an amplifier, letting the amplifier’s

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built-in DAC do the digital to analog conversion,
potentially reducing noise and interference.

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So they did.

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But, someone at Toshiba was apparently dissatisfied
with the ordinary nature of RCA cables.

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[in a very over-the-top fashion] 
Pfft, it’s the future!

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We’re using lasers to read sound from these
miraculously small polycarbonate discs, and

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YOU expect US to convey the data they contain
using WIRES?

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What kind of technologically regressive firm
do you think this is?

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We are TOSHIBA!

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We MAKE the future!

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And so they did.

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And really, what they did isn’t all that
remarkable.

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See, sending S/PDIF signals over copper wire
simply involved having a voltage repeatedly

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switch from high to low.

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S/PDIF uses biphase mark code, also known
as Differential Manchester encoding, to make

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the signal’s clock part of the datastream
itself, but now we’re getting into specifics

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that don’t really matter because of this
fun little truth nugget;

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TOSLINK transmits the same exact S/PDIF signals.

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Yep.

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TOSLINK is nothing more than a fancier way
to send a S/PDIF datastream to another device.

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Rather than using a wire and pulsing a voltage
through it, TOSLINK uses optical fiber and

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a pulsing light.

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Of course, the sending device had to run a
pulsing voltage through an LED to create that

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pulsing light, and then again the receiving
end has to use a photodiode to turn that pulsing

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light into a pulsing voltage, so when we get
right down to it is there really a difference at all?

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Well, yes, but, kinda, no...

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And also, it’s complicated.

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Firstly, I don’t want to sound overly harsh
here towards TOSLINK.

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Sending a signal through optical fiber is
not only objectively cooler, but does have

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some advantages.

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Though even that’s debatable.

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And secondly, while TOSLINK is indeed a fiber
optic communication standard, it is in no

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way comparable to the fiber optic networking
equipment that makes up the backbone of the internet.

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So while TOSLINK may not have much to brag
about compared to a simple coaxial S/PDIF connection

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this isn’t to say fiber optics
aren’t important.

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But back to TOSLINK.

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One of the stranger things about it is that
its history seems almost entirely unknown.

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I’ve been looking for some sort of patent
related to it but haven’t had any luck,

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and even if Toshiba did patent it, it looks
like they just let it out into the wild.

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It was fairly common on high-end CD players
by the late 1980’s, and in 1987 it was referred

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to as an ad hoc standard by Digital Audio
and Compact Disc Review.

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So it looks like, though Toshiba may have
created it (and they appear to have the trademark

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on the word TOSLINK), they let pretty much
anyone who wanted to use it, use it.

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It just sorta happened.

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Indeed, the TOSLINK connector and cable specifications
were adopted by the Electronic Industries

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Association of Japan as EIAJ RC-5720

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The physical bits of the TOSLINK standard
are actually pretty darn simple.

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Take a look at an optical audio out port and
you’ll see it glows with the red light of an LED.

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Some people think TOSLINK uses lasers, but
it’s just an LED, it’s much cheaper and

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works fine.

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Taking a look inside the device reveals that,
well, there’s not a lot going on behind

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the scenes either.

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It’s just a molded bit of plastic to hold
onto the connector and align the tip of the cable

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with the LED.

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The cable itself isn’t really special, either.

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While some high-quality cables will use bundles
of very thin glass strands, many are simple

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1mm plastic fibers that run from one end to
the other.

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Pretty much just a strand of fishing line.

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You can see that the cable will pass light
through it no matter how it loops around,

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though if you introduce an extreme kink, you
can damage the cable.

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With it plugged into the back of this CD player,
you can see that now the other end glows,

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ready to pump that pulsing light into another
device.

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On the back of an A/V receiver or other sort
of amplifier, you’ll see some other TOSLINK

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connections though these don’t glow.

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Well, some of them might if it’s also got
a return out for something like a digital

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audio recorder or MiniDisc player or whatever,
but if it’s the receiving end, it’s as

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dark as the future of Windows phone.

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Inside is a photodiode which will produce
a voltage when it sees light, and thus will

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be able to reproduce the pattern of light
pulses it receives as a pattern of voltage

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pulses to be processed, interpreted by a DAC
and finally turned into sound.

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It wasn’t just CD players that used TOSLINK.

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Wait.

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I already mentioned MiniDisc.

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Pretend I didn’t.

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Rewrites are hard.

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As more digital formats appeared on the scene,
like Digital Audio Tape in 1987, it was common

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to see TOSLINK inputs and outputs on mid-to-high-end
equipment.

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Fun fact!

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The advent of consumer digital recording really
freaked out the recording industry, as now

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it was possible to create bit-for-bit perfect
copies of a CD onto a digital audio tape cartridge.

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While TOSLINK wasn’t the only way to accomplish
this, it was pretty widely supported by then

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and we may have this little cable to at least
partially thank for the Audio Home Recording

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Act of 1992, the later Digital Millennium
Copyright Act, and the subsequent DRM schemes

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that would be cooked up in the decades to
come.

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[a large crowd chants in unison]
Thanks, Toshiba!

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One of the more interesting things I ran across
was a seemingly needless design detail that

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hints at a never-realized upgrade to TOSLINK.

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See, the connector itself is keyed, meaning
it can only be inserted with one orientation.

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This isn’t necessary given that the optical
fiber itself is centered, and there’s only one of them.

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I honestly never even thought about this.

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If, however, there were two fibers in the
same cable, say one for transmitting data

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and another for receiving, there would need
to be a way to ensure the fibers in this two-way

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cable are correctly aligned with the connector.

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It’s possible that the TOSLINK connector
was keyed for just such a cable design, though

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this never came to fruition.

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Cool.

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So TOSLINK is a simple way to turn S/PDIF
into light, push it through a pipe, and then turn

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light back into S/PDIF.

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But, um, why?

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Well, here’s where things start to seem
a little superfluous.

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One of the key advantages of using an optical
fiber to send data is that it’s not subject

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to electromagnetic interference.

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Normal audio cables like these can pick up
humming or whining or any other sort of noise

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because they act like antennae.

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But… if we’re in the digital realm, what
difference does that make?

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Sure, a coaxial cable carrying a S/PDIF signal
can pick up noise, but unless that noise gets

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so phenomenally bad that it somehow overpowers
the very powerful and not-at-all ambiguous

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high-low-high-low pattern the cable carries,
it doesn’t matter.

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Analog noise in a digital signal doesn’t
come out in the processed result.

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This has always seemed more than a little
weird to me.

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TOSLINK’s signature advantage, that it’s
immune to electromagnetic interference, would

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only really be a selling point if it were
transmitting analog signals.

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But it isn’t.

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For the most part, either a digital signal
gets through, or it doesn’t.

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Until the signal gets so bad that the receiver
can’t piece it together correctly, it will

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sound exactly the same.

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And once problems do show up, it’s gonna
get glitchy

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[audio defects begin to appear] 
or the signal will just drop out.

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It’s not gonna sound worse.

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It won’t sound right at all.

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So choosing TOSLINK over coaxial because it
is impervious to RF interference or other

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electrical noise is, well, I’d argue rather
uninformed.

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Your amplifier’s circuitry doesn’t care
how it’s getting that data.

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And once it gets to the DAC, we’re well
past the point where cables could make a difference.

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Now it can be argued that having your audio
devices entirely electrically isolated from

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one another could be advantageous because
it prevents freak occurrences like a huge

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electrical spike through your RCA jacks cooking
a chip on your amp or something

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really unlikely like that, though if you’re really
worried about electrical isolation

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for sound quality purposes, good luck avoiding the building’s electrical wiring

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they’re eventually gonna share.

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And then, well, TOSLINK actually has a lot
of disadvantages.

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The most significant practical issue is that
the longer the cable gets, the harder it is

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for light to reach the other end.

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Remember, this is largely a consumer standard,
so even the most premium cables aren’t anything

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near optically pure and the longer they get,
the more they reduce the amount of light that

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gets through.

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Add to that the fact that it’s only got
a weedy little LED lighting the whole thing

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up, and you get a maximum cable length of
5 meters.

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In practice this can be and is regularly exceeded,
especially with the brighter LEDs and with more

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sensitive photodiodes of more modern equipment,
but with a coaxial cable you can go a lot

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farther before issues crop up.

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Now I don’t want to get too far into comparing
TOSLINK to a coaxial S/PDIF connection, because

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that means getting into incredibly nitpicky
details like clock jitter that you shouldn’t

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even look up because trust me it will just
make you question your sanity.

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So instead, let’s talk about Mini-TOSLINK!

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Since the only part that actually interfaces
with the LED and photodiode is this little

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nib, the mini-TOSLINK connector was created
to allow optical audio connections in the

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same form factor as a 3.5mm audio jack, and
indeed to combine optical audio and analog

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audio into a single port.

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This by the way is perhaps the greatest proof
that they keying in the standard TOSLINK connector

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00:13:31,630 --> 00:13:35,690
was completely unnecessary unless they had
future plans.

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The TOSLINK part of this is just an itty bit
longer than a normal audio jack, just to make

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sure that when you plug in headphones or whatever
you don’t poke the LED or photodiode.

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Fun fact!

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I didn’t know this was a thing until I was
messing about with my Chromecast Audio, unplugged

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the audio cable from it, and the hole started
glowing.

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00:13:55,020 --> 00:14:00,860
I kid you not, I did not know Mini-TOSLINK
was a thing, and I learned about it by accident.

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I don’t know exactly how common it is in
the grand scheme of things, but it allowed

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00:14:04,560 --> 00:14:09,620
portable devices like this MiniDisc Walkman
to record from an optical source.

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00:14:09,620 --> 00:14:10,860
Neat.

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00:14:10,920 --> 00:14:14,060
Apparently it was found in some laptops and
other random junk.

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00:14:15,040 --> 00:14:19,780
I hope it wasn’t, like, super common and
I’ve just missed this until 2016 or whatever.

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00:14:19,780 --> 00:14:20,540
By the way.

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00:14:20,540 --> 00:14:24,300
If you go to Amazon and search “toslink
cable” you’ll find that some of the more

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00:14:24,300 --> 00:14:27,180
popular options feature gold-plated connectors.

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[exasperated sigh]

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So far, optical audio connections have really
withstood the test of time.

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It’s pretty impressive that a digital standard
introduced in 1983 is still quite common in

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consumer audio visual equipment.

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Loads of new TVs feature an optical audio
out, as do game consoles, Blu-Ray players,

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and even some streaming boxes.

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Recently, that’s started changing for reasons
we’ll get into, but on the whole it’s

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still a pretty common sight in 2019.

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00:14:56,380 --> 00:15:00,590
A large part of why it’s still so common
is that in addition to uncompressed stereo

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PCM audio, TOSLINK also supported compressed
5.1 or 7.1 surround sound using Dolby Digital

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or DTS.

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Since loads of A/V receivers going back to
the ‘90s will still be able to process at

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00:15:12,960 --> 00:15:18,300
least some of the datastreams coming from
a Blu-ray player or smart TV, it’s been

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remarkably future-proof.

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00:15:19,570 --> 00:15:25,350
Also of note is that the physical specifications
of TOSLINK were borrowed in the ADAT Lightpipe,

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00:15:25,350 --> 00:15:27,450
or ADAT Optical Interface.

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00:15:27,450 --> 00:15:32,420
This professional standard carries up to 8
channels of uncompressed PCM audio using the

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00:15:32,420 --> 00:15:38,000
same hardware as garden variety TOSLINK connectors
and cables, though this high-bandwidth signal

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is entirely incompatible with our old friend
S/PDIF.

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00:15:41,690 --> 00:15:45,070
So then, why is TOSLINK apparently on its
way out?

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00:15:45,070 --> 00:15:49,490
Well… because of the same thing I said was
an advantage a few moments ago.

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It’s not been updated.

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00:15:51,680 --> 00:15:53,279
Like, at all.

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00:15:53,279 --> 00:15:58,820
One of the things Blu-ray brought us was uncompressed
surround sound formats like Dolby TrueHD,

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00:15:58,820 --> 00:16:01,161
and TOSLINK doesn’t have the bandwidth to
support that.

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00:16:01,161 --> 00:16:02,980
[angry yelling off-screen]
YOU JUST SAID ADAT Lightpipe

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00:16:02,980 --> 00:16:05,400
could carry 8 channels of PCM audio!

258
00:16:05,740 --> 00:16:07,420
You’re right, I did.

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00:16:07,420 --> 00:16:10,600
But that’s not actually TOSLINK or S/PDIF.

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It just uses the same cable and connectors.

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00:16:12,540 --> 00:16:13,240
[offscreen person mutters angrily]

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00:16:13,240 --> 00:16:17,300
See, it would be relatively easy to just make
the LED go blinky blinky a little faster and

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00:16:17,300 --> 00:16:20,760
thus increase the bitrate of the data coming
through the cable.

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00:16:20,760 --> 00:16:26,480
But that means creating a new standard to
be agreed upon by all the manufacturers out there.

265
00:16:26,480 --> 00:16:29,100
And, uh, that can be difficult!

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00:16:29,110 --> 00:16:33,520
See, I can connect this brand new television
to this A/V receiver from the ‘90s over

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00:16:33,520 --> 00:16:37,750
TOSLINK precisely because the standard hasn’t
really ever changed.

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00:16:37,750 --> 00:16:42,610
If TOSLINK were updated, at the very least
I’d need to tell the TV to downgrade its

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output to match this receiver’s expected
input, and that can get messy fast.

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Remember, this is one-way communication.

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00:16:50,920 --> 00:16:53,480
Easier to just never change it up, ya know?

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00:16:53,480 --> 00:16:56,840
And then there’s this other thing called
HDMI.

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00:16:56,840 --> 00:17:01,140
Yeah, the Handy-Dandy Movie Input not only
transmits digital video at a bitrate that

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00:17:01,140 --> 00:17:05,679
will put your CD player to shame, but it also
transmits digital audio at bitrates that will

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00:17:05,679 --> 00:17:07,879
put your CD player to shame.

276
00:17:07,879 --> 00:17:09,089
Poor CD player.

277
00:17:09,089 --> 00:17:10,730
You’re doing alright.

278
00:17:10,730 --> 00:17:18,260
Since the very first HDMI version 1.0, debuting
in December 2002, uncompressed 8 channel,

279
00:17:18,260 --> 00:17:23,280
192 kilohertz, 24 bit PCM audio was supported.

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00:17:23,280 --> 00:17:25,420
That’s like way more bits!

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00:17:25,429 --> 00:17:29,649
With all that bandwidth, high-resolution sound
is no problem at all.

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00:17:29,649 --> 00:17:36,100
S/PDIF, and thus TOSLINK, sorta became obsolete
once Blu-ray, and even HD-DVD, appeared on

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00:17:36,100 --> 00:17:39,049
the scene offering lossless surround sound.

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00:17:39,049 --> 00:17:41,950
HDMI could carry those signals no problem.

285
00:17:41,950 --> 00:17:49,380
Oh and HDMI 2.0 introduced 32 channel audio,
so we're fine now.

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00:17:49,380 --> 00:17:56,120
ALSO, in 2009 HDMI 1.4 introduced the audio-return
channel, that’s why one of the HDMI inputs

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00:17:56,130 --> 00:17:58,750
on your TV is labeled ARC.

288
00:17:58,750 --> 00:18:03,869
This sends audio back through the HDMI cable
to enable your soundbar or home theater system

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00:18:03,869 --> 00:18:08,210
to receive the audio that your TV itself is
producing, such as when streaming video on

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00:18:08,210 --> 00:18:13,020
a Smart TV or simply receiving over-the-air
broadcast television.

291
00:18:13,020 --> 00:18:13,520
Yeah.

292
00:18:13,520 --> 00:18:18,140
HDMI has superseded TOSLINK on all fronts
in the home theater space.

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00:18:18,140 --> 00:18:23,860
As more sound bars and A/V receivers support
the audio-return channel, TOSLINK increasingly

294
00:18:23,869 --> 00:18:26,639
finds itself in the legacy category.

295
00:18:26,640 --> 00:18:29,800
Which is still, just kinda weird!

296
00:18:29,800 --> 00:18:35,040
Fiber-optics are capable of some insane bandwidths,
and while TOSLINK hails from the age of 10

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00:18:35,040 --> 00:18:40,760
megabyte hard drives, you’d think that we’d
have seen more fiber optic standards in the home.

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00:18:40,760 --> 00:18:45,320
In the next video, we’ll explore why fiber
optics have remained little more than a novelty

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00:18:45,320 --> 00:18:49,600
in the consumer space, and discuss whether
any of our current everyday technologies could

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00:18:49,600 --> 00:18:52,139
perhaps be better served with fiber optics.

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00:18:52,139 --> 00:18:53,260
Thanks for watching.

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00:18:53,260 --> 00:18:57,140
I hope you found this video to be as enlightening
as it is digital.

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00:18:57,860 --> 00:19:00,400
That is terrible.

304
00:19:00,400 --> 00:19:01,120
And yet.

305
00:19:01,120 --> 00:19:02,060
I still said it.

306
00:19:02,060 --> 00:19:03,380
Worse, I wrote it!

307
00:19:03,400 --> 00:19:04,900
I even wrote these words!

308
00:19:04,900 --> 00:19:06,009
How silly.

309
00:19:06,009 --> 00:19:10,210
But not as silly as selling TOSLINK cables
with gold plated connectors and claiming that

310
00:19:10,210 --> 00:19:12,320
makes a superior connection!

311
00:19:12,320 --> 00:19:17,690
Anyway, I still think TOSLINK is pretty neat
and even futuristic, even though it’s pushing

312
00:19:17,690 --> 00:19:19,399
40 years old now.

313
00:19:19,399 --> 00:19:23,139
As always, thank you to everyone who supports
this channel through Patreon, particularly

314
00:19:23,139 --> 00:19:25,990
the fine folks you see scrolling up your screen.

315
00:19:25,990 --> 00:19:30,100
Contributions from viewers like you make this
channel sustainable and I owe you my thanks

316
00:19:30,100 --> 00:19:31,570
and appreciation.

317
00:19:31,570 --> 00:19:34,440
If you’d like to join these awesome people
in supporting the channel with a pledge of

318
00:19:34,440 --> 00:19:38,279
your own, you can find a link to my Patreon
page in the description.

319
00:19:38,280 --> 00:19:40,800
Thanks for your consideration, and I’ll
see you next time!

320
00:19:41,660 --> 00:19:44,020
♫ optically smooth jazz ♫

321
00:19:45,660 --> 00:19:47,279
...communication technology.

322
00:19:47,280 --> 00:19:52,000
On our increasingly connected planet, nearly
everything we do from making a phone ca…

323
00:19:53,580 --> 00:19:56,140
I didn’t get very far!

324
00:19:56,140 --> 00:19:57,940
Since the only wat that, whoops?

325
00:19:59,460 --> 00:20:03,059
Uncompressed digital surround formats.

326
00:20:03,059 --> 00:20:04,640
That line is wrong!!!

327
00:20:04,640 --> 00:20:05,640
Oh no!!!!!

328
00:20:05,840 --> 00:20:10,480
That take might have been fine, but there
were some weird bits.

329
00:20:10,480 --> 00:20:13,780
Also of note is that the physical specifications
of TOS…

330
00:20:13,780 --> 00:20:15,520
Whe.. *clears throat*

331
00:20:16,100 --> 00:20:17,700
Pairs of copper wire that need to be made

332
00:20:17,700 --> 00:20:20,640
more precisely and with higher tolerances euch…

333
00:20:20,640 --> 00:20:21,980
AUGH!

334
00:20:22,340 --> 00:20:26,860
We are on the second line, and recording is…

335
00:20:26,860 --> 00:20:28,620
[unintelligible]