TOSLINK: That one consumer fiber optic standard

Our modern world essentially runs on

fiber

optic

communication technology. On our increasingly connected planet, almost everything we do, from making a phone call to checking our bank account balance, yelling at computers to turn off the lights to watching this very video, almost certainly depended, at some point , of converting your voice, input, or data that creates this image into incredibly short, incredibly fast pulses of light, shooting that light with *A LASER* through a glass tube, and counting the pulses at the other end. And probably doing that many times over potentially thousands of miles, almost instantaneously. And yet, in the

consumer

space,

fiber

optic

s are almost nowhere to be found.

We send digital video data through these complicated cables with more than a dozen tiny copper wires inside. Networking equipment in homes and businesses still uses Ethernet, twisted pairs of copper cables that must be manufactured with greater precision and higher tolerances every time we want to increase speed by another order of magnitude. In reality, we don't seem to have found a place for fiber optics outside of connecting the Internet to your home or business, and even then that's not exactly common. Except Toshiba once decided to connect CD players to amplifiers with fiber optics in 1983. Yes, while fiber optics may seem like the upper echelon of communications technology (and in fact it is), there has been a grade fiber optic of consumption.

standard

floating around since the early 80s.

It would be TOSLINK, which is an abbreviation of Toshiba Link. In this video, we'll learn a little about this surprisingly old optical

standard

. Ahh, the compact disc. What a beautifully designed medium for storing uncompressed digital sound. As you probably know, these things store data in millions of little holes and terrain, and when you shine a focused laser on those bumpy bits, the varying depth causes destructive interference and results in a reflected beam that flashes in light and dark, representing to each other. zeros. Note that a hole does not mean 1 and a ground means 0, but rather the transition from hole to ground OR from ground to hole means 1, and an unchanged period means 0.

A CD player has to process quite a bit before it can convert that stream of raw data into sound. First you have to translate the eight-to-fourteen modulation of the pits and lands to reveal 8-bit words, then you have to analyze the various signals within that data stream for things like track markers and timing, and finally you have to work at through interleaved Reed-Solomon encoding to obtain the individual samples that make up the digital sound. Once we are at that step, we can send those decoded samples to a DAC to convert them into electrical impulses that will drive headphones or speakers to impart mechanical impulses to the air we hear as sound.

If you want to learn more about the compact disc and how digital sound works, you can watch these previous videos of mine. Now, without a DAC, we can't convert those samples into sound. Since that is the main purpose of a CD player, the CD player itself contains a DAC and generates a line-level analog audio signal to send to an amplifier over commonly used RCA cables. And for almost all intents and purposes, this is perfectly fine. Unless you cross the line into audiophile territory, you'll probably be delighted with the sound that comes from these two little connectors.

And then, for most of us, that's the end of the story. But the act of playing a CD is the last step in the life cycle of producing a sound recording on a compact disc. In the studio, digital tape machines create digital recordings from microphones or other analog sources, and various editing teams need to access those recordings to manipulate them and eventually master them to compact disc. This is all different today, but pretend it's 1985, okay, everyone does it anyway. Knowing that some standard method of moving digital audio streams would be necessary, Sony and Philips (the co-creators of the Compact Disc standard) developed S/PDIF, often pronounced "spidiff" because, let's face it, that's more fun.

S/PDIF stands for Sony/Philips Digital Interconnect Format, or you can also see Sony/Philips Digital Interface. When Sony and Philips worked out the details about S/PDIF, they used standard coaxial audio cables like these to send digital data over commonly used copper cables. And that worked well! Nobody complained. But then Toshiba got into the CD player business and wanted to be able to send the raw digital sound data recovered from the CD separately to an amplifier, allowing the amplifier's built-in DAC to do the digital-to-analog conversion, potentially reducing noise. and interference. So they did it. But someone at Toshiba was apparently dissatisfied with the ordinary nature of RCA cables.

Pfft, it's the future! We're using lasers to read sound from these miraculously small polycarbonate disks, and YOU expect us to transmit the data on them via WIRES? What kind of technologically regressive company do you think this is? We are TOSHIBA! WE MAKE the future! And they do it like that. And really, what they did is not that extraordinary. You see, sending S/PDIF signals over copper cable simply involved a voltage repeatedly changing from high to low. S/PDIF uses a two-phase mark code, also known as differential Manchester encoding, to make the signal clock part of the data stream itself, but now we're getting into details that don't really matter because of this fun little TRUE;

TOSLINK transmits exactly the same S/PDIF signals. Yes. TOSLINK is nothing more than a more elegant way to send an S/PDIF data stream to another device. Instead of using a cable and emitting a voltage through it, TOSLINK uses fiber optics and a pulsating light. Of course, the sending device had to run a pulsating voltage through an LED to create that pulsating light, and then again the receiving end has to use a photodiode to convert that pulsating light into a pulsating voltage, so when we get down to it Is there really any difference? Well, yes, but more or less no...

And besides, it's complicated. First of all, I don't want to seem too harsh on TOSLINK. Sending a signal over fiber optics is not only objectively cooler, but it also has some advantages. Although even that is debatable. And second, while TOSLINK is indeed a fiber optic communication standard, it is in no way comparable to the fiber optic networking equipment that forms the backbone of the Internet. So while TOSLINK may not have much to boast about compared to a simple coaxial S/PDIF connection, this doesn't mean that fiber optics aren't important. But back to TOSLINK. One of the strangest things is that its history seems almost completely unknown.

I've been looking for some kind of patent related to it, but haven't had any luck, and even if Toshiba patented it, it seems like they just let it out. It was quite common on high-end CD players in the late 1980s, and in 1987 Digital Audio and Compact Disc Review referred to it as an ad hoc standard. So it seems that even though Toshiba may have created it (and they seem to have the trademark on the word TOSLINK), they let pretty much anyone who wanted to use it use it. It just happened. In fact, the TOSLINK connector and cable specifications were adopted by the Electronic Industries Association of Japan as EIAJ RC-5720.

The physical bits of the TOSLINK standard are quite simple. Take a look at an optical audio output port and you'll see it glowing red with an LED. Some people think TOSLINK uses lasers, but it's just an LED, it's much cheaper, and it works well. Taking a look inside the device reveals that, well, not much is going on behind the scenes either. It's just a piece of molded plastic to hold the connector and align the tip of the cable with the LED. The cable itself isn't really special either. While some high-quality cables use bundles of very thin glass strands, many are simple 1mm plastic fibers running from one end to the other.

Pretty much just a strand of fishing line. You can see that the cable will pass light through it no matter how it is wound, although if you introduce extreme twist, you can damage the cable. With it plugged into the back of this CD player, you can see that the other end is now glowing, ready to pump that pulsing light to another device. On the back of an A/V receiver or other type of amplifier, you'll see other TOSLINK connections, although they don't glow. Well, some of them might if they also have a return for something like a digital audio recorder or a MiniDisc player or whatever, but if it's the receiving end, it's as dark as the future of the Windows phone.

Inside is a photodiode that will produce a voltage when it sees light and will therefore be able to reproduce the pattern of light pulses it receives as a pattern of voltage pulses to be processed, interpreted by a DAC and finally converted into sound. It wasn't just CD players that used TOSLINK. Wait. I already mentioned MiniDisc. Pretend I didn't do it. Rewrites are difficult. As more digital formats came on the scene, such as Digital Audio Tape in 1987, it was common to see TOSLINK inputs and outputs on mid- to high-end equipment. Made of fun! The advent of

consumer

digital recording really scared the recording industry, as it was now possible to create bit-for-bit perfect copies of a CD on a digital audio tape cartridge.

While TOSLINK was not the only way to achieve this, it had widespread support by then and we may have this little cable to thank, at least partially, for the Home Audio Recording Act of 1992, the subsequent Copyright of the Digital Millennium and later. DRM schemes that would be developed in the coming decades. Thanks Toshiba! One of the most interesting things I came across was a seemingly unnecessary design detail that hints at a never-made upgrade to TOSLINK. See, the connector itself is keyed, meaning it can only be inserted in one orientation. This is not necessary since the optical fiber itself is centered and there is only one.

Honestly, I never thought about this. However, if there were two fibers in the same cable, say one for transmitting data and one for receiving, there would have to be a way to ensure that the fibers in this bidirectional cable are properly aligned with the connector. It is possible that the TOSLINK connector was designed for such a cable design, although this never came to fruition. Cool. So TOSLINK is a simple way to convert S/PDIF to light, push it through a tube, and then convert the light back to S/PDIF. But why? Well, this is where things start to seem a little superfluous.

One of the main advantages of using an optical fiber to send data is that it is not subject to electromagnetic interference. Regular audio cables like these can pick up hum, squeak, or any other type of noise because they act as antennas. But… if we are in the digital field, what difference does it make? Sure, a coaxial cable carrying an S/PDIF signal can pick up noise, but unless that noise is so phenomenal that it somehow overwhelms the very powerful and unambiguous high-low-high-low pattern the cable carries, it won't. it matters. Analog noise in a digital signal does not appear in the processed result.

This has always seemed more than a little strange to me. The distinct advantage of TOSLINK, that it is immune to electromagnetic interference, would only be a selling point if it were transmitting analog signals. But is not. In most cases, either a digital signal arrives or it does not. Until the signal is so bad that the receiver can't put it together correctly, it will sound exactly the same. And once problems appear, there will be failures or the signal will simply be cut off. It won't sound worse. It won't sound good at all. So choosing TOSLINK instead of coaxial because it's resistant to RF interference or other electrical noise is, well, I'd say pretty uninformed.

Your amplifier circuitry doesn't care how it gets that data. And once it gets to the DAC, we're already past the point where cables could make a difference. Now it can be argued that having your audio devices completely electrically isolated from each other could be advantageous because it prevents strange occurrences like a huge electrical spike through your RCA connectors cooking a chip in your amplifier or something really unlikely like that, although if not I'm really concerned about electrical insulation for sound quality purposes, good luck avoiding the building electrical wiring they will eventually share. And then, well, TOSLINK actually has a lot of disadvantages.

The most important practical problem is that the longer the cable, the more difficult it will be for light to reach the other end. Remember, this is very much a consumer standard, so even the most premium cables are not optically pure and the longer they get longer, the more they reducethe amount of light that passes through. Add to that the fact that it only has one small LED illuminating everything and you get a maximum cable length of 5 meters. In practice this can be and is regularly overcome, especially with the brighter LEDs and more sensitive photodiodes of newer equipment, but with a coaxial cable you can go much further before problems arise.

Now I don't want to go too far comparing TOSLINK to a coaxial S/PDIF connection, because that means getting into incredibly finicky details like clock jitter that you shouldn't even look for because, trust me, it will only make you question your sanity. So, let's talk about Mini-TOSLINK! Since the only part that actually interacts with the LED and photodiode is this little tip, the mini-TOSLINK connector was created to allow optical audio connections in the same form factor as a 3.5mm audio jack and, in fact, to combine optical audio and analog audio. in a single port. By the way, this is perhaps the biggest proof that introducing the standard TOSLINK connector was completely unnecessary unless they had plans for the future.

The TOSLINK part of this is just a tiny bit longer than a normal audio jack, just to make sure that when you plug in headphones or whatever, you don't touch the LED or photodiode. Made of fun! I didn't know this existed until I was playing with my Chromecast Audio, unplugged the audio cable and the hole started glowing. I'm not kidding, I didn't know Mini-TOSLINK existed and I found out about it by accident. I don't know exactly how common it is in the grand scheme of things, but it allowed portable devices like this MiniDisc Walkman to record from an optical source.

Clean. Apparently it was found on some laptops and other random debris. I hope it wasn't very common and I missed it until 2016 or something. By the way. If you go to Amazon and search for "

toslink

cable," you'll find that some of the most popular options feature gold-plated connectors. So far, optical audio connections have truly stood the test of time. It's pretty impressive that a digital standard introduced in 1983 is still fairly common in consumer audiovisual equipment. Many new TVs feature an optical audio output, as do game consoles, Blu-Ray players, and even some streaming boxes. Recently, that's started to change for reasons we'll get to, but overall it's still pretty common in 2019.

A big part of why it's still so common is that in addition to uncompressed stereo PCM audio, TOSLINK also supports compressed 5.1. or 7.1 surround sound using Dolby Digital or DTS. Since many A/V receivers dating back to the '90s will still be able to process at least some of the data streams coming from a Blu-ray player or smart TV, it's remarkably future-proof. Also of note is that TOSLINK's physical specifications were borrowed from the ADAT Lightpipe or ADAT optical interface. This professional standard carries up to 8 channels of uncompressed PCM audio using the same hardware as popular TOSLINK connectors and cables, although this high-bandwidth signal is completely incompatible with our old friend S/PDIF.

So why is TOSLINK apparently on its way out? Well... for the same reason I said it was an advantage a few moments ago. It has not been updated. Absolutely. One of the things Blu-ray brought us was uncompressed surround sound formats like Dolby TrueHD, and TOSLINK doesn't have the bandwidth to support it. YOU JUST SAID THAT ADAT Lightpipe could carry 8 channels of PCM audio! You're right, I did. But actually that's not TOSLINK or S/PDIF. Just use the same cable and connectors. Look, it would be relatively easy to make the LED flash a little faster and thus increase the bit rate of the data coming over the cable.

But that means creating a new standard that all manufacturers will have to agree to. And that can be difficult! See, I can connect this new TV to this 90s A/V receiver via TOSLINK precisely because the standard has never really changed. If TOSLINK were upgraded, you would at least need to tell the TV to reduce its output to match the expected input of this receiver, and that can get complicated quickly. Remember, this is a one-way communication. It's easier to just never change it, you know? And then there's another thing called HDMI. Yes, the Handy-Dandy Movie Input not only streams digital video at a bit rate that will put your CD player to shame, it also streams digital audio at bit rates that will put your CD player to shame.

Poor CD player. You're doing it right. Since the first HDMI 1.0 version, which debuted in December 2002, 8-channel, 192 kilohertz, 24-bit uncompressed PCM audio was supported. That's a lot more fragments! With all that bandwidth, high-resolution sound is no problem. S/PDIF, and therefore TOSLINK, became obsolete once Blu-ray, and even HD-DVD, appeared on the scene offering lossless surround sound. HDMI could carry those signals without problems. Oh, and HDMI 2.0 introduced 32-channel audio, so now we're good. ALSO, in 2009 HDMI 1.4 introduced the audio return channel, which is why one of the HDMI inputs on your TV is labeled ARC. This sends the audio back through the HDMI cable to allow your sound bar or home theater system to receive the audio your TV produces, such as when you stream video on a Smart TV or simply receive over-the-air TV streaming.

Yes. HDMI has replaced TOSLINK on all fronts in the home theater space. As more sound bars and A/V receivers support audio return channel, TOSLINK increasingly finds itself in the legacy category. Which is still a bit strange! Fiber optics are capable of incredible bandwidths and while TOSLINK comes from 10 megabyte hard drives, you would think we would have seen more fiber optic standards in the home. In the following video, we'll explore why fiber optics remain little more than a novelty in the consumer space and discuss whether any of our current everyday technologies could perhaps work better with fiber optics.

Thanks for watching. I hope you found this video as enlightening as it was digital. That's terrible. And yet. I still said it. Worse yet, I wrote it! I even wrote these words! What a fool. But not as silly as selling TOSLINK cables with gold-plated connectors and claiming they offer a superior connection! Anyway, I still think that TOSLINK is quite elegant and even futuristic, even though it is already 40 years old. As always, thanks to everyone who supports this channel through Patreon, especially the great people you see scrolling up on the screen. Contributions from viewers like you make this channel sustainable and I owe you my thanks and appreciation.

If you want to join these amazing people in supporting the channel with your own pledge, you can find a link to my Patreon page in the description. Thank you for your consideration and see you next time! ♫ optically smooth jazz ♫ ...communication technology. On our increasingly connected planet, almost everything we do, from making a phone case... I didn't get very far! Since all he did was, wow! Uncompressed digital surround formats. That line is wrong!!! Oh no!!!!! That shot might have been okay, but there were some weird parts. Also of note is that the physical specifications of TOS... When... *clears throat* Pairs of copper wires that must be manufactured with greater precision and to higher tolerances euch...

AUGH! We are on the second line and the recording is...