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TOSLINK: That one consumer fiber optic standard

Jun 06, 2021
Our modern world essentially runs on

fiber

optic

communication technology. In our increasingly connected planet, almost everything we do, from making a phone call to checking our bank account balance, to yelling at computers to tell them to turn off the lights, to watching this very video, was almost certainly based , at some point, to convert your voice, or input, or the data that makes up this image into incredibly brief and incredibly fast pulses of light, shooting that light with *A LASER* down a glass tube and counting the pulses in the other end. And probably doing that a bunch of times over potentially thousands of miles, almost instantly.
toslink that one consumer fiber optic standard
And yet, in the

consumer

space,

fiber

optic

s is almost nowhere to be found. We send digital video data through these complicated cables with more than a dozen tiny copper wires within them. Network equipment in homes and businesses still uses Ethernet, twisted pairs of copper wire that must be manufactured with greater precision and higher tolerances each time we want to increase speed by another order of magnitude. Really, it seems like we haven't found a place for fiber optics other than connecting the internet to your home or business, and even then that's not exactly common. Except there was a time when Toshiba decided to connect CD players to amplifiers with fiber optics in 1983.
toslink that one consumer fiber optic standard

More Interesting Facts About,

toslink that one consumer fiber optic standard...

Yes, while fiber optics may seem like the upper echelon of communications technology (and in fact it is), there has been a degree of consumption.

standard

floating around since the early '80s. That would be TOSLINK, which is short for Toshiba Link. In this video, we're going to learn a bit 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 jagged bits, the varying depth causes destructive interference and results in a reflected beam that flashes light and dark, representing some and others. zeros Note that a pit does not mean 1 and a ground means 0, rather the transition from pit to ground OR ground to pit means 1, and a no-change period means 0.
toslink that one consumer fiber optic standard
A CD player has to do some processing before you can convert that raw data stream into sound. First you have to translate the modulation from eight to fourteen of 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 time, and finally you have to work through of interleaved Reed-Solomon encoding to really get the individual samples that make up the digital sound. Once we're at that step, we can send those decoded samples to a DAC to be converted into electrical impulses that will drive headphones or speakers to impart mechanical impulses into the air that we hear as sound.
toslink that one consumer fiber optic standard
If you want to learn more about compact disc and how digital sound works, you can check out these previous videos of mine. Now, without a DAC, we can't turn 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 via garden variety 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 coming from these two little jacks. And so, 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 multiple editing teams need access to those recordings in order to manipulate them and ultimately master them onto a compact disc. This is all different today, but just pretend it's 1985, okay, everyone is doing it anyway. Knowing that there would have to be some standard way to move digital audio streams, Sony and Philips (the co-creators of the Compact Disc standard) developed S/PDIF, which is 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 of S/PDIF, they were using standard coaxial audio cables like these to send the digital data over common-variety copper cables. And that worked fine! Nobody complained. But then Toshiba got into the CD player business and they 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, which could reduce noise. and interference. So they did.
But apparently someone at Toshiba wasn't happy with the ordinary nature of RCA cables. Pfft, it's the future! We are using lasers to read sound from these miraculously small polycarbonate discs, and YOU expect us to transmit the data on them using 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 remarkable. See, sending S/PDIF signals over a copper cable simply involved a voltage repeatedly changing from high to low. S/PDIF uses biphasic marking 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 nugget of truth;
TOSLINK carries exactly the same S/PDIF signals. Yes. TOSLINK is just a more elegant way to send a stream of S/PDIF data to another device. Instead of using a wire and transmitting a voltage through it, TOSLINK uses fiber optics and pulsating light. Of course, the sending device had to run a pulsing voltage through an LED to create that pulsing light, and then again the receiving end has to use a photodiode to convert that pulsing light to a pulsing voltage, so when let's get to that. is there really a difference? Well, yes, but a little, no...
And besides, it's complicated. First of all, I don't want to sound too harsh here with TOSLINK. Sending a signal over fiber optics is not only objectively cooler, but it 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 makes up the backbone of the Internet. So while TOSLINK may not have much to brag about compared to a simple coaxial S/PDIF connection, that's not to say that fiber optics aren't important. But back to TOSLINK. One of the strangest things about it is that its history seems almost completely unknown.
I've been looking for some kind of patent related to it, but no luck, and even if Toshiba did patent it, it seems they just let it out. It was quite common in high-end CD players in the late 1980s, and by 1987 Digital Audio and Compact Disc Review referred to it as an ad hoc standard. So it seems that while Toshiba may have created it (and it seems they have the trademark on the word TOSLINK), they allowed pretty much anyone who wanted to use it to do so. 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 actually quite simple. Take a look at an optical audio-out port and you'll see that it glows red from an LED. Some people think that TOSLINK uses lasers, but it's just an LED, and it's much cheaper and works fine. Taking a look inside the device reveals that, well, there's not much going on behind the scenes either. It's just a piece of plastic molded to hold the connector and line up the tip of the wire with the LED. The cable itself isn't really special either. While some high-quality cables use bundles of very fine glass wires, many are simple 1mm plastic fibers stretched 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 put an extreme twist in it, you can damage the cable. With it plugged into the back of this CD player, you can see the other end is now glowing, ready to pump that pulsating light to another device. On the back of an A/V receiver or other type of amplifier, you'll see a few other TOSLINK connections, though these aren't glowing. Well, some of them might if they also got a return for something like a digital audio recorder or MiniDisc player or whatever, but if it's the receiving end, it's about as dark as the future of Windows Phone.
Inside it is a photodiode that will produce a voltage when it sees light, so it can 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. Not only CD players used TOSLINK. Wait. I already mentioned MiniDisc. Pretend I didn't. Rewrites are hard. As more digital formats came onto the scene, such as digital audio tape in 1987, it was common to see TOSLINK inputs and outputs on mid to high end equipment. Fun fact! The advent of

consumer

digital recording really gave the recording industry a scare, as it was now possible to create perfect bit-for-bit copies of a CD on a digital audio tape cartridge.
While TOSLINK wasn't the only way to accomplish this, it was quite compatible back then, and we may have this little cable to thank, at least partially, for the Home Audio Recording Act of 1992, the subsequent Rights Act. copyright of the digital millennium and the subsequent DRM schemes that would cook up for decades to come. Thank you 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 hardcoded, which means it can only be inserted in one orientation. This is not necessary since the optical fiber itself is centered and there is only one of them.
Honestly, I didn't even think about this. However, if there were two fibers in the same cable, say one to transmit data and one to receive, there should be a way to ensure that the fibers in this bi-directional cable are correctly aligned with the connector. The TOSLINK connector may have been designed for such a cable layout, although this never came to fruition. Fresh. So TOSLINK is a simple way to convert S/PDIF to light, push it through a pipe, and then convert light back to S/PDIF. But why? Well, this is where things start to seem a bit 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, whine, or any other type of noise because they act like antennas. But… if we are in the digital realm, what difference does that make? Sure, a coaxial cable carrying an S/PDIF signal can pick up noise, but unless that noise is so phenomenal that it somehow overpowers the very powerful and unambiguous high-low-high-low pattern that the cable carries, it won't. matter. Analog noise in a digital signal does not appear in the processed result.
This has always seemed more than a little weird to me. TOSLINK's signature advantage of being immune to electromagnetic interference would only really be a selling point if you were transmitting analog signals. But is not. For the most part, a digital signal either goes through or doesn't go through. Until the signal is so bad that the receiver can't assemble it correctly, it will sound exactly the same. And once the problems appear, it will fail or the signal will just disconnect. It won't sound worse. It won't sound good at all. So choosing TOSLINK over coax because it's impervious to RF interference or other electrical noise is, well, I'd say misinformed.
Your amplifier circuit doesn't care how you get that data. And once you get to the DAC, we're 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 freak events like a big electrical spike through your RCA connectors cooking a chip in your amp or something really unlikely like that, although if I am. really concerned about electrical insulation for sound quality purposes, good luck avoiding building electrical wiring that you will eventually share. And then, well, TOSLINK actually has a lot of downsides.
The most important practical problem is that the longer the cable, the more difficult it is for light to reach the other end. Remember, this is largelya consumer standard, so even the most premium cables are far from optically pure and the longer they run, the more they reduce the amount of light that gets through. Add to that the fact that it only has one small LED lighting everything up, and you get a maximum cable length of 5 meters. In practice this can and is regularly overcome, especially with the brighter LEDs and more sensitive photodiodes in newer equipment, but with coax you can go much further before problems arise.
Now, I don't want to go too deep into comparing TOSLINK vs. a coaxial S/PDIF connection, because that means going into incredibly finicky details like clock jitter that you shouldn't even look for because trust me, it'll only make you question your sanity. So instead, let's talk about Mini-TOSLINK! Since the only part that actually interfaces with the LED and photodiode is this little tip, the mini-TOSLINK connector was created to allow for 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 best proof that keying in the standard TOSLINK connector was completely unnecessary unless they had future plans. The TOSLINK part of this is just a tiny bit longer than a normal audiojack, just to make sure that when you plug in headphones or whatever, you don't touch the LED or the photodiode. Fun fact! I didn't know this was a thing until I was playing around with my Chromecast Audio, I unplugged the audio cable and the hole started glowing. No kidding, I didn't know Mini-TOSLINK was a thing, and found out quite 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. Neat. Apparently, it was found on some laptops and other random junk. I hope it wasn't super common and I missed it until 2016 or whatever. By the way. If you go to Amazon and search for "

toslink

cable," you'll find that some of the more popular options feature gold-plated connectors. So far, optical audio connections have really stood the test of time. It's pretty impressive that a digital standard introduced in 1983 is still pretty common in consumer AV equipment.
Many new TVs feature an optical audio output, as do game consoles, Blu-Ray players, and even some streaming boxes. That's recently started to change for reasons we'll get to, but overall it's still a pretty common sight in 2019. A big part of why it's still so common is that, in addition to uncompressed stereo PCM audio, TOSLINK also supports 5.1 compressed . 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 been remarkably future-proofed.
Also of note, the physical specifications of TOSLINK 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 garden-variety TOSLINK cables and connectors, though this high-bandwidth signal is totally incompatible with our old friend S/PDIF. So why is TOSLINK apparently on the verge of dying out? Well... for the same reason that I said a few moments ago, it was an advantage. It has not been updated. Like, not at all. 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 that.
YOU JUST SAID that the ADAT Lightpipe could carry 8 channels of PCM audio! You're right, I did. But that's not actually TOSLINK or S/PDIF. Just use the same cable and connectors. See, it would be relatively easy to make the LED blink a bit faster and thus increase the bit rate of the data going over the wire. But that means creating a new standard that will be agreed upon by all manufacturers. And hey, that can be hard! Look, I can connect this new TV to this A/V receiver from the 90s via TOSLINK precisely because the standard has never changed.
If TOSLINK was upgraded, you'd at least have to tell the TV to downsample its output to match this receiver's expected input, and that can get messy quickly. Remember, this is a one-way communication. It's easier to just never change it, you know? And then there's this other thing called HDMI. Yes, Handy-Dandy Movie Input not only streams digital video at bitrates that will put your CD player to shame, it also streams digital audio at bitrates that will put your CD player to shame. Poor CD player. You're doing it right. Since the first version 1.0 of HDMI, which debuted in December 2002, uncompressed 24-bit, 192 kilohertz, 8-channel PCM audio has been supported.
That's like a lot more bits! With all that bandwidth, high-resolution sound is no problem. S/PDIF, and therefore TOSLINK, became obsolete once Blu-ray, and even HD-DVD, came on the scene offering lossless surround sound. HDMI could carry those signals with no problem. Oh, and HDMI 2.0 introduced 32-channel audio, so we're good to go now. ALSO, in 2009, HDMI 1.4 introduced 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 that your own TV produces, such as when streaming video on a Smart TV or just receiving a TV broadcast. by air.
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 finds itself more and more in the legacy category. Which is still, a little weird! Fiber optics are capable of some incredible bandwidths, and while TOSLINK hails from the era of 10-megabyte hard drives, you'd think we'd have seen more fiber-optic standards in the home. In the next video, we'll explore why fiber optics has remained a novelty in the consumer space and discuss whether any of our current day-to-day technologies could perhaps be better served by fiber optics.
Thanks for watching. I hope you found this video as enlightening as it is digital. That's terrible. And yet. I still said it. Worse still, 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 it makes a superior connection! Anyway, I still think TOSLINK is pretty cool and even futuristic, even though it's already 40 years old. As always, thanks to everyone who supports this channel through Patreon, particularly the good people you see scrolling up your screen. Contributions from viewers like you make this channel sustainable and I owe you my thanks and appreciation.
If you'd like to join these amazing people in supporting the channel with a contribution of your own, 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. In our increasingly connected planet, almost everything we do from making a phone ca... I didn't get very far! From the only wat that, oops! Uncompressed digital surround formats. That line is wrong!!! Oh no!!!!! That take could have been okay, but there were some weird parts. Also worth noting is that the physical specifications of TOS...
When... *clears throat* Pairs of copper wires that need to be manufactured with higher precision and tighter tolerances euch... AUGH! We're on the second line, and the recording is...

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