9 ms·
Building Ultra Long Range Toslink
- rcarmo 2y ago“Knowing this stuff means that it is possible to build bigger, better, more horrifying solutions/workarounds to problems.” Hear hear. Great read!
- mrb 2y agoYou can buy a spool of 100km of "OTDR launch fiber" which is quite compact as it's just raw fiber terminated by two connectors. 100km sells for only $1400: https://aliexpress.com/item/1005006978999338.html https://aliexpress.com/item/1005006978999338.html which is well within his budget as it seems he spent over $1000 on this hobby project. He could have bought two spools for 200km, laid that on his bench, and call it a day, instead of driving around data centers only to achieve 160km :-) But that's just the lazy side of me talking. Heck he could even return the spools for a refund when he's done :-)
- vluft 2y agoOn a related note, the excellent DIY Perks youtube channel recently replaced toslink leds with lasers to do a wireless surround system https://www.youtube.com/watch?v=1H4FuNAByUs https://www.youtube.com/watch?v=1H4FuNAByUs
- actionfromafar 2y agoNext step, point a TOSLINK laser at the Moon Retroreflectors!
- dylan604 2y agoThere was something posted not too long ago that bounced radio signals off of the moon that they then turned into an audio filter based on their testing on what it would do to the signal.
- jrockway 2y agohttps://en.wikipedia.org/wiki/Earth%E2%80%93Moon%E2%80%93Earth_communication https://en.wikipedia.org/wiki/Earth%E2%80%93Moon%E2%80%93Ear... I like the example audio file they have for the article, because the QSO ends with "73, bye bye" and that bounces off the moon and is received by the sender a little bit later. The moon is far away! (I also really enjoy the distortion to SSB signals that you get by tuning the "carrier" frequency slightly wrong; more likely in this case because the moon changes the frequency of the reflected signal due to the doppler effect. Also happens with satellite comms, though you might not notice if you're using FM and not SSB.)
- mey 2y agoThe dark side of the moon on continuous loop would be an interesting project.
- dylan604 2y agoWhat happens when your sub starts kicking so hard that your walls start to vibrate causing the line of sight to go intermittent?
- ragebol 2y agoThen the audio drops out, so it's a self-correcting problem! Also, the beam is a bit divergent, even if it vibrates the beam could still cover the sensor.
- dylan604 2y agoNot necessarily. The sub is not usually attached to a wall, so it wouldn't self correct like you're suggesting
- chowells 2y agoI think you missed a joke there. Loss of signal -> silence -> no vibrations -> signal resumption.
- dylan604 2y agono, you're missing the point. the subwoofer is not connect to a wall that vibrates, so it wouldn't miss the signal. the surround speakers and possibly the front and surround speakers tend to be attached to a wall. The floor doesn't shake enough for the sub to loose alignment is the point.
- ragebol 2y agoI was making a joke though. Also, if you bounce the signal off a mirror on the wall like DIY Perks did, then walls vibrating even a little bit will be an issue if the beam is narrow enough.
- simoncion 2y agoWell, (to treat this seriously, rather than the joke it was) where's your transmitter? And are there vibration-sensitive components inside of either the transmitter or receiver? Several times a month, cars idle outside my apartment with bass loud enough to severely shake my windows, and somewhat shake my walls and floor. I imagine a receiver that's physically attached (or merely very near) to a subwoofer that loud would have trouble maintaining a steady optical link.
- gorkish 2y agoThe problem with DIY perks solution is that the manchester clock+data encoding is an amplitude modulated thing and isnt really very robust to using in free space. LED bulbs, sunlight, or all manner of other stuff can and will fuss with it. This is probably why he ended up having to go with lasers instead of just a big IR blaster against the ceiling. If he modulated the OOK signal onto some kind of carrier the entire thing would be a lot more reliable and as a bonus could probably ditch the lasers. This is more or less how the infrared wireless speakers and headphones of yore (80's and 90's) did the job.
- Neywiny 2y agoSo the problem with his solution is that he needed a solution to solve a problem?
- gorkish 2y agoIt works but it's not going to be very robust without a carrier.
- amluto 2y agoIf you mean a literal “IR blaster”, those generally modulate onto a 38kHz carrier. (I built an IR blasting device out of a 555 timer and an LED once, and it worked great, and no, I did not use precision resistors or capacitors. I admit I’m not actually sure whether a standard IR blaster contains a modulator or whether the device supplying the signal is expected to pre-modulate it.). You’re not going to get anything resembling acceptable audio quantity over consumer IR tech.
- gorkish 2y ago> anything resembling acceptable audio quantity over consumer IR tech I don't know what you are on about. You can go to your local walmart and get IR headphones off the shelf that work exactly this way.
- pseudosavant 2y agoSuch a great video. There is a really good chance I use that technique for a remote subwoofer at some point. Really elegant solution.
- skerit 2y agoA part of me wants to use his idea to set up some kind of wireless data connection just for fun.
- glitchc 2y agoOnce you replace the TOSLINK transmitter with an SFP module, it's not the TOSLINK tx/rx that's being tested but rather the low-bandwidth S/PDIF protocol operating over a high bandwidth SFP link. So it's not really TOSLINK that's being extended but rather S/PDIF over optical fibre. Maybe I'm missing something....
- toast0 2y agoTOSLINK is S/PDIF over (usually plastic) optical fiber. S/PDIF over SFP is S/PDIF over optical fiber too, unless you're using SFP DACs.
- martijnvds 2y agoSFPDIF
- myself248 2y agoFiber techs have "talk sets" which are just little voice intercoms that you plug into an unused fiber in the bundle, so you can yammer back and forth between manholes/closets/whatever. I'm not sure whether they're even digital; it's been a while since I played with a pair.
- dtgriscom 2y agohttps://www.amazon.com/Optical-Talkset-Duplex-Digital-Communication/dp/B0BM67LJL2 https://www.amazon.com/Optical-Talkset-Duplex-Digital-Commun...
- mrguyorama 2y agoHow do you non-destructively jack into a glass fiber? Or are they limited to hooking into transceivers on the ends?
- toast0 2y agoYou're probably in the manhole to work on a fiber break anyway...
- chgs 2y agoAnd hopefully not break all the other fibres while doing it. Of course that’s why we get so concerned about pinch points with dual fibres
- 0_____0 2y agoMy guess is it's already-terminated dark fiber with an FC connector (no transceiver) Found an example here. https://www.fiberinstrumentsales.com/fis-singlemode-multimode-talk-set-w-sc-fc-interchangeable.html https://www.fiberinstrumentsales.com/fis-singlemode-multimod... You can't really "get into" an optical fiber mid-run without splicing. Splicing isn't really that hard (I've done it! Fusion splicers are little robotic wonders. Most of the work is in the prep, not the splice itself.)
- myself248 2y ago
- theandrewbailey 2y ago> TOSLINK/SPDIF turns this into a manchester coded serial signal, at around 1.5Mbps that is much more resiliant to analog interference When I was connecting my surround sound receiver to my PC, I was bummed that SPDIF standard was never improved to support 5.1 or 7.1 uncompressed surround sound. 5.1 DTS compression is the best it can do (due to the 1.5 mbps bandwidth), but PC support is rather limited. I gave up, and I've been using it with HDMI for 10 years. Running it through my video card/drivers has introduced (bearable) complexity, but I wonder why receivers to this day can't connect to PCs over USB instead. (Yes, most receivers have USB ports, but those are for playing MP3s off a flash drive. A PC isn't a flash drive.)
- dylan604 2y ago> A PC isn't a flash drive That could be a kind of cool app that would allow you to present a folder on your PC as a media device. However that would then require a dreaded USB-A to USB-A type of cable <shudder>
- EvanAnderson 2y agoTarget disk mode on a lot of older Mac machines did that over Firewire. You could boot the machine into target disk mode and it would present its mass storage over Firewire. It was pretty cool.
- dylan604 2y agoBut you couldn't use the machine at the same time. This would be like a SAMBA share, but over USB
- zokier 2y agoYou can connect two computers with usb and setup network between them, so you can just use smb/cifs. Microsoft has even handy tutorial for that: https://learn.microsoft.com/en-us/windows-hardware/design/component-guidelines/usb4-interdomain-connections https://learn.microsoft.com/en-us/windows-hardware/design/co...
- ahofmann 2y agoThis is wonderfully useless, what a great delight to read!
- fru654 2y agoI wonder if something like this is possible with HDMI? Separate 10G SFP+ for each color channel, one more for i2c, create a similar style breakout PCB, maybe add an MPO or CWDM mux… Could be a fun project. Optical HDMI cables are expensive and most of the time come with a preexisting cable which is hard to route (in conduits) due to HDMI connector size.
- psophis 2y agoNot HDMI, but SDI over fiber is basically this. It can be muxed and is used in the broadcast industry for long haul camera feeds.
- chgs 2y agoSDI over fibre with a cheap converter if you need to push multi hindered metres. Then people moves to 222-6 which packetised the SDi over IP, and now 2110 which breaks out the SDI to its components. For most long haul links people still compress, good old h264 or 265 with latencies in the 200-500ms range (plus network propagation), or J2k/JXS and NDI which are more like 50-150ms. Ultimately 200mbit of h265 is far cheaper to transmit than 10ish gbit of 2110, and in many cases the extra 500ms doesn’t matter.
- crote 2y agoSuch products are already commercially available [0][1]! DIYing it is probably too painful to be doable. You won't be able to source any kind of protocol translation chip, so you'll have to send it essentially raw into quad SFP+ transceivers. Running 4+ fibers instead of the required 2 (or even 1) is very expensive, and any kind of WDM immediately blows up your budget. Unless you're getting the stuff for free from a DC renovation or something, it's just not worth it. On top of that you also have to deal with designing board for extremely fast signals, which is pretty much impossible to debug without spending "very nice car" amounts of money on tooling. People have done it before, but I definitely don't envy them. [0]: https://www.startech.com/en-us/audio-video-products/st121hd20fxa2 https://www.startech.com/en-us/audio-video-products/st121hd2... [1]: https://www.blackmagicdesign.com/products/miniconverters/techspecs/W-CONM-29 https://www.blackmagicdesign.com/products/miniconverters/tec...
- crote 2y agoI'm surprised it works this well! A while ago I looked into this for a similar-ish hobby project, and the main dealbreaker seemed to be the mandatory AC coupling capacitors: they are intended to block DC currents, so a signal which is substantially slower than intended is essentially fighting a high-pass filter. This is also why there are special AV SPF transceivers: Unlike Ethernet, SDI suffers from "pathological patterns" consisting of extremely long runs of 1s or 0s, which can cause "DC wander" [0]. SDI transceivers need to take this (albeit extremely unlikely) possibility into account, or risk losing signal lock. For this reason I pretty much gave up on the idea of reliably going sub-100Mbps on cheap and easily available 1G / 10G SFP modules. Seeing it (mostly) work for TOSLINK at 3Mbps is beyond my wildest expectations - I bet the LVDS driver's high slew rate is doing quite a bit of work here too. [0]: https://www.ti.com/lit/an/snaa417/snaa417.pdf https://www.ti.com/lit/an/snaa417/snaa417.pdf
- MrRadar 2y agoThe article mentions S/PDIF (which TOSLINK is an optical version of) uses Manchester code[1] which eliminates the DC component by ensuring every bit has at least one transistion of the signal between high and low. [1] https://en.wikipedia.org/wiki/Manchester_code https://en.wikipedia.org/wiki/Manchester_code
- teraflop 2y agoYup, but that only works if those transitions happen frequently enough compared to the time constant of the high-pass filter. Presumably, that's why the author found that the optics only worked with signals above about 150kHz.
- crote 2y agoThe problem is the speed. S/PDIF doesn't have a DC component at the S/PDIF bit rate, but to an SFP+ transceiver that S/PDIF signal is a lot closer to DC than to its expected signal. A single S/PDIF bit viewed as if it were a 10Gbps signal looks like thousands of 1s followed by thousands of 0s. Yes, they all balance out in the end, but you can still develop quite a large drift within a single sub-S/PDIF-bit sequence. A thought experiment to clarify it: let's say you are hoisting a bucket with a DC motor. You're feeding it with a 50Hz AC power source. It's obviously not going anywhere, because it's just oscillating rapidly. You'd need for the motor to run in a single direction for a few minutes to actually lift the bucket. Now drive it with a 0.0000001Hz AC power source (which starts at peak voltage). The motor is going to reverse after 58 days, but does that actually matter? For any practical purposes, how is it different from a DC power source?
- omer9 2y agoLight travels 300.000km/h, not 200.000km/h. Or did I overlooked something?
- halestock 2y agoIt’s about 200,000km/h when traveling through fiber optic cable.
- rayhaanj 2y agoI think you meant kilometres per second, not per hour.
- crote 2y agoVery simplified: the speed of light isn't constant. The well-known 299.792.458 m/s constant is the speed of light in vacuum - and glass isn't a vacuum. Light goes significantly slower in a lot of mediums, including glass, and it's why things like lenses are possible.
- somat 2y agoIt is also why high speed trading firms invest in microwave radio links the speed of light through air is enough faster enough than the speed of light through glass that they feel this gives them a trading edge. Honestly, gaming the system this hard really worries me, a lot of our economic ability is tied up in these trading system(the stock market). and I can see something going wrong far faster than our ability to fix it.
- Vecr 2y agoFlash crash. It's really hard to put in fair minimum times on things. A basic delay isn't really any better.
- formerly_proven 2y agoSpeed of light in a medium is c/index of refraction, which is about 1.5 for every glass and highly transparent plastic.
- PaulHoule 2y agoI think it's amusing that optic fiber connectors have had so little success in the market though I have a few TOSLINK and the coaxial equivalent in my upstairs home theater (I have a Sony 300 disc CD changed packed with DTS 5.1 Music Discs so I'm living the surround music dream) and downstairs (computer to stereo, computer to minidisc recorder, etc.) I recently got a cable to hook up a Meta Quest 3 to a PC for PCVR. My understanding is that works like a high-spec USB 3 cable but has an optic fiber in it for the data so it can be really long.
- synchrone 2y agoI tore down oculus link cable - it's just copper internally. Also oculus works fine over the "charging" type c cable + type-c to type-a + a classic copper usb3.0 extender of another 1.8 meters.
- PaulHoule 2y agoI use it for other things and it performs admirably. (In particularly my Sony camera has trouble with cheap cables) It is one of two "elite" USB-C cables I keep near my computer, the other one is the shorter cable that came with the Looking Glass Go.
- zokier 2y agoYou can see the fibers clearly in this teardown video: https://www.youtube.com/watch?v=Spa_pAn871c https://www.youtube.com/watch?v=Spa_pAn871c
- TacticalCoder 2y ago> I think it's amusing that optic fiber connectors have had so little success in the market though I have a few TOSLINK and the coaxial equivalent in my upstairs home theater ... Is TOSLINK that unsuccessful? I was already using TOSLINK a very long time ago (in the nineties) and I'm still using TOSLINK today. Enter any audio store and they have TOSLINK cables. It's very old by now though and I take it there's better stuff but TOSLINK still does the job. My "music" path doesn't use TOSLINK: source, eg QOBUZ for (lossless) streaming -> ethernet -> integrated amp (which has a DAC) -> speakers But my "movie" (no home theater anymore atm) path uses TOSLINK: TV -> TOSLINK -> same integrated amp -> speakers For whatever reason that amp is quite new and has all the bells and whistles (ARC and network streaming, for example) yet that amp still comes with not one but two (!) TOSLINK inputs. I'd say that's quite a successful life for a standard that came out in the mid eighties.
- pclmulqdq 2y agoLarge-scale audio systems will often use synchronous Ethernet or other similar protocols instead of things like TOSLINK at this point. Also, a general solution to "send low-bandwidth over an SFP" is to use FM or phase modulation to carry the signal on top of a carrier wave that is fast enough for the retimers in question. Buffer and retimer chips will not respect amplitude in a modulation system, but they will largely preserve frequency and phase.
- iancmceachern 2y agoYeah, there is a whole standard for it https://en.m.wikipedia.org/wiki/Audio_over_Ethernet https://en.m.wikipedia.org/wiki/Audio_over_Ethernet This is what most professional places have
- dekhn 2y agoI had a dream many years ago where I could connect all my house devices; all the TVs, stereos, etc, all to one ether network (ideally the same physical network as my switched Internet ports) and send AV from any source to any dest without having to worry that much about formats or bandwidth limits. It never really happened and each company came up with their own bespoke solution, seemingly with "mobile phone-first" philosophy.
- iancmceachern 2y agoThey have this too, it's how thise fancy systems in rich peoples mansions work and fancy board rooms. A famous company in that world is Crestron. They make stuff that let's you do this, control everything from one central system. The protocol for the video is GigE vision. It's how many fancy broadcast, CCD security, and fancy home theater/office setups work
- rdtsc 2y agoIndeed. I worked with CobraNet for some years. I kind like their isochronous protocol. But being a layer 2 protocol I believe it's outdated at this point. Also greetings, again (I believe?) from a fellow assembly username HNer!
- khaki54 2y agoI love when people do random stuff like this. I couldn't even suss out his reasoning for taking this project on. Normally there is at least a notional but absurd use case. Cool project though, and I'm sure he had fun.
- brudgers 2y agoRecently, I described Toslink in an internet conversation...the other person expected it to be like USB. It is pretty amazing how old this technology is and how little anyone complains about it. There just aren't Toslink horror stories floating around the popular internet (SPDIF is another WTF-a-75Ω-RCA-cable? story). Toslink is a technology that just works (and the normal limit is a generous 10m)
- blt 2y agoTOSLink was kind of a silly idea because digital electrical signals would also prevent ground loops. The key is digital vs. analog, not optical vs. electrical.
- ielillo 2y agoGround loops comes from the ground mismatch between two electrically connected devices. When you use an optical link, you isolate those two devices since there is no common ground and the hum goes away. Same if connect a battery device to a grounded device.
- exabrial 2y agoLaugh, but this probably does have some real world applications for Live Audio. Digital Live audio mixing is taking over, but it suffers one flaw compared to analog: Latency. Humans can adjust pretty easily to performing an action and hearing a delayed response (that's pretty natural in our daily lives, basically think of it as echolocation). This is sort of like standing farther from a guitar amplifier (sound travels roughly 1 ms per foot). However, singers have it the worst: there is 0 latency from their voice to the ear canal, so monitor systems try to use analog as much as possible. For digital audio links, every time you join then end-to-end or decode them, you get a bit of latency added. There are a few audio interconnects that run on Ethernet's OSI Layer 0 (physical medium) * AES50 is standardized, basically you can think of it as the 100Base-T of digital live audio. It's synchronously clocked with a predictable latency; with roughly ~62us per link. Pretty nice. Cat5e cables are dirt cheap and musicians are destructive as feral cats, so it it's a pretty good solution. Max length is 100meters. * AudioDante is also popular but actually relies on IP Layer 3, so latency is variable. Typical values are 1ms - 10ms. Max length is pretty much unlimited, with a lot of asterisks. FTA: 11us is _unbelievably good_ digital latency, but with near unlimited length is actually a pretty good value proposition for Live Audio. There may be a niche demand for a product like this: slap in some SFP adapters, transmit a channel of digital audio over whatever medium you like.
- toast0 2y ago> FTA: 11us is _unbelievably good_ digital latency, but with near unlimited length is actually a pretty good value proposition for Live Audio. There may be a niche demand for a product like this: slap in some SFP adapters, transmit a channel of digital audio over whatever medium you like. Used to be you could get an PRI (ISDN/T1) phone line for this kind of work, but I think it's pretty doubtful that you can keep it end-to-end low latency PRI with modern telephony. You'd have to be ok with single channel 8-bit, 8k uLaw, but that's not that bad; you could probably orchestrate multiple calls for multiple channels. Someone is going to convert it to SIP with 20ms packets and there goes your latency.
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- no_identd 2y ago…now complete the circle, and run a 56k V.92(*) link over it. 8) (* important, cuz despite claims to the contrary V.90 ain't at the Shannon limit, but V.92 is — kind of. See https://news.ycombinator.com/item?id=4344349 https://news.ycombinator.com/item?id=4344349 )
- no_identd 2y agoFollow up, quoting from the article: >It is tempting to attach a “dialup” modem to both sides, this would probably create the greatest modern day waste of a 100 GHz optical channel, given that it gives a final output bandwidth of ~40 kbit/s, and I assume this would probably confuse an intelligence agency if they were tapping the line. Regardless of the fact that 48 kbps seems more likely, I'd really like to know the noise floor & SNR of that link
- jrockway 2y agoI fear that I'm about to be nerd sniped because I really want to try to make this work as a "proper" 10G signal. I feel that if you over sample the SPDIF signal and line code it to not have a DC bias, and do the opposite on the receive end, it would work. That is maybe too much transformation to be interesting, however. So I wonder what happens if you sample the signal at the 10G ethernet sample rate like a 1 bit ADC does, transmit that, and smooth the too-high-frequency result with a capacitor? I am very worried that I may end up trying this ;)
- Aloha 2y agoI never would have considered using an SFP to transmit arbitrary signals over a mux, this is fun and kinda crazy.
- m463 2y agoI thought I read somewhere where someone had somehow jammed a fiber cable into a toslink/spdif port (doing all this optically without sfp) can't seem to find the article. (janky in comparison to this article, which is amazing!)
- martinmunk 2y agoI did basically this exact same thing at work a few years ago. For time-correlating audio measurements around the office buildings I needed a analog reference signal in sync. So I drew up a PCB design with a toslink in/out connector, and a connector for a SFP module and just a lvds driver in between. It worked straight away (more luck than skill) I could then re-use network fibers already run around the basement, and convert it to analog in the MDF rooms of each building, and run the analog signal up to the 3rd floor through existing RJ45 cables.