Hacker successfully tests Toslink at unprecedented distances of up to 143 kilometers — separate test shows transmission speeds of about 1.47 Mb/s

News
By
published

With cutting-edge speeds of up to 1,536 kbit/s, or about 0.19 MB/s

Toslink cable with some optical fibers
(Image credit: Shutterstock)

On December 10, at the 38th Chaos Communication Congress (38C3, essentially a German tech conference for various hackers and other community members), hacker Benjojo discussed how he had successfully pushed Toslink traffic, generally limited to 10 meters over 143 kilometers. Then, yesterday, fellow hacker Manawyrm demonstrated IP-over-Toslink based on what that demonstration proved [h/t Hackaday]. The speeds are...not incredible since this cable isn't meant for this, but that it's possible at all is still cool.

So, what made it all possible? Benjojo uploaded a full-text version of his 38C3 conference speech to his blog, including the full technical details of how Toslink was at such an unreasonable 140+ kilometers. This move, apparently an exercise in learning more about optical data transmission, involved more than just sending unconventional data. Toslink is typically restricted to just 10 meters but was eventually tested and pushed as far as 143.2 kilometers, albeit with lots of separate contraptions and data center involvement required.

Benjojo proved that optical data transmission is impressive, and its complex rules remain in play even when restricted to yesteryear technology like a Toslink optical audio cable. However, for the typical user, Toslink cables are impractical for use as last-resort fiber networking cables, particularly when the speeds are capped at roughly 1,536 kbit/s or just 0.19 MB/s.

IP-over-Toslink: A very useless consumer fiber optic hack - YouTube IP-over-Toslink: A very useless consumer fiber optic hack - YouTube
Watch On

Meanwhile, Manawyrm's IP over the Toslink hack, detailed on her KittenLabs page, reflects real-world IP transmission speeds of about 1.47 Mb/s, or 0.18 MB/s. This isn't quite the maximum limit of Toslink (about 3% short), but it's probably as close as we're getting.

Manawyrm and Benjojo have proved that most optical data cables do almost the same. With the correct tweaks, specifically designed cables like Toslink can be extended to distances and formats beyond what their creators ever imagined.

There's a lot of beauty in that, and the technical expertise required in its execution speaks volumes of the determination necessary to push technology to its limits. Unfortunately, it is still a Toslink cable at the end of the day, so there's no practical use beyond what Benjojo and Manawyrm learned by pushing Toslink to its limits. Actual networking cables aren't going anywhere anytime soon.

Christopher Harper
Christopher Harper
Contributing Writer

Christopher Harper has been a successful freelance tech writer specializing in PC hardware and gaming since 2015, and ghostwrote for various B2B clients in High School before that. Outside of work, Christopher is best known to friends and rivals as an active competitive player in various eSports (particularly fighting games and arena shooters) and a purveyor of music ranging from Jimi Hendrix to Killer Mike to the Sonic Adventure 2 soundtrack.

27 Comments Comment from the forums
  • bit_user
    Toslink is one of those technologies from the 80's that's still good at what it does. The main drawback is that they haven't extended it to support the latest audio formats, instead preferring to keep them tied to HDMI and its content protection mechanisms. However, you can use regular Toslink for 24-bit, 96 kHz PCM stereo, which is enough for any hi-fi applications.

    BTW, 24-bit 96 kHz stereo is 4.6 Mbps. Toslink definitely supports that, even if the signal he used for testing was just 16-bit 44.1 kHz stereo.
    Reply
  • derekullo
    In the sense that he hacked together a bunch of old tech and made it function with new tech ... i guess that makes him a hacker!
    Reply
  • cpkennit83
    Its strange how brilliant minds often pursue such strange challenges. To each their own i guess.
    Reply
  • BillyBuerger
    I like how Manawyrm brought up Technology Connections on YouTube to show it working.
    Reply
  • AkroZ
    bit_user said:
    Toslink is one of those technologies from the 80's that's still good at what it does. The main drawback is that they haven't extended it to support the latest audio formats, instead preferring to keep them tied to HDMI and its content protection mechanisms. However, you can use regular Toslink for 24-bit, 96 kHz PCM stereo, which is enough for any hi-fi applications.

    BTW, 24-bit 96 kHz stereo is 4.6 Mbps. Toslink definitely supports that, even if the signal he used for testing was just 16-bit 44.1 kHz stereo.
    I was using Toslink with Dolby Digital or DTS in 5.1 24bits 192khz (with Dolby Digital Live, the next version on S/PDIF (Toslinq) Dolby Digital Plus accept 16 channels and 6144 kb/s). They removed the support to go HDMI (which force a phantom screen for an audio amply) with monthly subscriptions to have full functionalities and can have issues.
    With Toslinq you just connect and its work but nowadays it's limited to PCM.
    It's false to think that Toslinq was abandonned because of it's limited specs, it was abandonned by Dolby and DTS because they have joined HDMI and forced the revokations of all licences on S/PDIF.
    Most Toslinq users were using it for surround sound, not for stereo.
    Reply
  • bit_user
    AkroZ said:
    Most Toslinq users were using it for surround sound, not for stereo.
    Yeah, it seems mostly a home theater technology, based on when it was introduced and how most people used it. Audiophiles also had the option of fancy S/T fiberoptic, which are only better in that they're less limited in length than Toslink and you can buy commodity networking cables for a lot cheaper than the audio-marketed ones.

    I've always used Toslink in my computer audio setup. It provides complete electrical isolation, interfaces with my outboard DAC, and I have a nice crossbar switch for rerouting different sources and destinations. It was sad to see Toslink ports disappearing from the rear connectors of PC motherboards, but you can buy USB -> Toslink converters quite cheaply and the one I have works perfectly (bit-perfect), even with a Raspberry Pi.
    Reply
  • Kamen Rider Blade
    We need TOSLINK 2.0.

    Toshiba made these transceivers more than 20 years ago.

    https://www.global.toshiba/ww/news/corporate/2003/02/pr2001.html
    It's capable of 150Mbps over TOSLINK optical Cables.

    Time to bring it to the larger audio world & out of car audio land exclusive tech.

    I'm sure audiofiles would have a field day with 150 Mbps to play with.

    For Reference:
    Base TOSlink 1.0 = 384 kbps
    ARC = 1 Mbps
    eARC = 38 Mbps
    TOSlink 2.0 = 150 Mbps using these old Totu133 transceivers.
    Reply
  • OldAnalogWorld
    The key difference between optical Toslink and copper (electrical) versions of SPDIF and HDMI, as well as other options, such as USB transmission, is galvanic isolation of the power supply circuits of the audio source and the DAC + amplifier, which immediately has a positive effect on the purity of the sound at the output, especially in terms of poorly protected audio circuits from interference and ground loops of motherboard circuits with a bunch of high-frequency interference and interference (including low-frequency harmonics) in PCs / laptops and other devices for outputting an audio signal with PWM power supplies and where there is no real grounding (and there is none in many places in the world).

    High-quality audio circuits are a whole science and technology. The only way to avoid such interference is galvanic isolation, i.e. transmitting audio data via optics, which also has a positive effect in terms of the safety of connecting such cables to ungrounded devices.

    Plus, optics, as shown above, easily transmits a signal over tens of meters where copper cable becomes monstrously expensive or heavy. An example is the whole 5 years of commissioning of DisplayPort 2.0 (UHBR20) version, which became a disgrace to the entire IT industry from 2019 to 2024. For 80Gbps transmission, cheap copper cables have ALREADY become a problem. And in order to get 8k@120Hz (banal smooth scrolling of text in 2D with high ppi (220-230+) for really high-quality text even in 27-32" office monitors), you need a bandwidth of 160Gbps, which is an impossible task for copper mass cheap cables. Which is proven by the shameful "newest" HDMI 2.2 (which will only be presented in hardware in 2025), which is practically no different from DisplayPort 2.0 2019 in bandwidth (80Gbps vs 96Gbps in both cases, taking into account service traffic - without it, everything is much worse and both options give nothing but 60-75Hz in 8k in lossless mode without lossy DSC compression), which is already morally obsolete without having time to be implemented in hardware. Since few people today need 8k monitors with a frame rate of only 60Hz, as well as TV.

    I personally have been using toslink for many years - it is extremely convenient and unpretentious in use.
    Reply
  • stuff and nonesense
    I use Toslink for the connections to a now positively ancient Yamaha DSP A-5. It connects a sky box, and a Samsung s95b digital out. Blu ray is connected by rca style connector cable.

    Electrically I prefer Toslink because it gives electrical isolation between components, less electrical noise. (Yes I know it’s digital, and the processing is essentially identical but I mean noise transfer into the system that can affect power stability thus causing hum in the amp stages. I had a cheap CD player that was horrible for this. Got to remember that 0V is a relative value within a circuit. A sensor suite installation of a system across a field, both ends grounded, had a 17V offset in the measured 0V level.

    Toslink does still work with Dolby Digital and DTS just not later iterations. The content providers seeing HDMI have tied their stuff to the harder to copy/break out standard. DD and DTS are transferred through the RCA style connector digital out from my Sony Blu Ray.

    Toslink was designed for a purpose, it fulfils that purpose (lots of punny adjectives come to mind - I’ll use) transparently. Clean cabling with a simple connector that has a positive latch - it is positively idiot proof.

    For its designed purpose I’ve found no drawbacks over 30 years (old kit was a technics midi separates system. I’m still using the speakers.
    Reply
  • bit_user
    OldAnalogWorld said:
    The key difference between optical Toslink and copper (electrical) versions of SPDIF and HDMI, as well as other options, such as USB transmission, is galvanic isolation of the power supply circuits of the audio source and the DAC + amplifier, which immediately has a positive effect on the purity of the sound at the output, especially in terms of poorly protected audio circuits from interference and ground loops of motherboard circuits with a bunch of high-frequency interference and interference (including low-frequency harmonics) in PCs / laptops and other devices for outputting an audio signal with PWM power supplies and where there is no real grounding (and there is none in many places in the world).
    I don't know about HDMI, but hi fi equipment typically uses isolation transformers on S/P-DIF inputs to avoid ground loops. These cables tend to be shielded, with the shield connected only at one end, to avoid creating a path between both chassis. Hi fi equipment also tends to segregate the digital vs. analog sections via different boards or at least sectioning them off into different areas with their own power domains.

    OldAnalogWorld said:
    High-quality audio circuits are a whole science and technology. The only way to avoid such interference is galvanic isolation, i.e. transmitting audio data via optics, which also has a positive effect in terms of the safety of connecting such cables to ungrounded devices.
    I'm not going to argue against fiber optics, since I use a lot of toslink in my computer audio setup (largely with an eye towards isolating power surges between my audio rack and computers), but it does seem to me that between R/C circuits and isolation transformers, you can do a lot to block both high frequency and low frequency interference from the signal sources.

    OldAnalogWorld said:
    Plus, optics, as shown above, easily transmits a signal over tens of meters where copper cable becomes monstrously expensive or heavy.
    Again, the range advantages of optical are obvious, but not at the kinds of data rates audio uses - copper is completely fine, there. 5GBase-T supports simple Cat 5e cabling at up to 100m.

    OldAnalogWorld said:
    An example is the whole 5 years of commissioning of DisplayPort 2.0 (UHBR20) version, which became a disgrace to the entire IT industry from 2019 to 2024. For 80Gbps transmission, cheap copper cables have ALREADY become a problem.
    How do those cables compare with Cat 8? 40GBase-T supports Cat 8 cables at up to 30m. If you just use all pairs in the cable for transmit, it could hit 80 Gb/s.

    My guess is that VESA was probably trying to cheap out on the transceivers, which is why they needed such a big cable with severe length limits. However, I don't know if you've ever looked at pricing on SFP+ optical transceiver modules for 10 gigabits or above, but those things aren't exactly cheap, either.

    OldAnalogWorld said:
    And in order to get 8k@120Hz (banal smooth scrolling of text in 2D with high ppi (220-230+) for really high-quality text even in 27-32" office monitors), you need a bandwidth of 160Gbps, ...

    I personally have been using toslink for many years - it is extremely convenient and unpretentious in use.
    I'm pretty sure Toslink isn't going to get you 160 Gbps, or anywhere remotely close. So, this whole display connectivity aspect is pretty irrelevant to any discussion of Toslink or audio connectivity. Also, glass fiber optics aren't terribly consumer-friendly, which is probably why the industry has balked at their adoption.
    Reply