At the recent 38C3 conference in Germany, someone gave a talk about sending TOSLINK digital audio over fiber optic networks rather than the very low-end short distance fibre you’ll find behind hour CD player. This gave [Manawyrm] some ideas, so of course the IP-over TOSLINK network was born.
TOSLINK is in effect I2S digital audio as light, so it carries two 44.1 kilosamples per second 16-bit data streams over a synchronous serial connection. At 1544 Kbps, this is coincidentally about the same as a T1 leased line. The synchronous serial link of a TOSLINK connection is close enough to the High-Level Data Link Control, or HDLC, protocol used in some networking applications, and as luck would have it she had some experience in using PPP over HDLC. She could configure her software from that to use a pair of cheap USB sound cards with TOSLINK ports, and achieve a surprisingly respectable 1.47 Mbit/s.
We like this hack, though we can see it’s not entirely useful and we think few applications will be found for it. But she did it because it was there, and that’s the essence of this game. Now all that needs to happen is for someone to use it in conjunction with the original TOSLINK-over network fiber, for a network-over-TOSLINK-over-network abomination.
That’s horrendous, I love it.
Next up, morse code over fiber using laser pointer!!
Jokes aside, both cases are cool hacks :)
Would it work with 96kHz sample rate, resulting in four times the throughput?
Sure, it could go faster with a higher sample rate, but the cheap sound card that was used only supports 44.1 and 48KHz. Some sound cards can do 192KHz over TOSLINK.
Ok so now we have network over toslink. A week or so ago we had toslink over lasers to wirelessly control speakers and those lasers can travel longer distances.
The only logical next step is wireless internet (point to point) over toslink.
I love this. At what distance does modal dispersion become a problem with these plastic “fibers”?
Toslink Spec. Says 10m
Most of “commoner” fiber would be 3-5 meters as many don’t really produce these up-to-spec or quality varies greatly
TOSLINK may find some actual useful use cases. Maybe you want to communicate with some device on top of a tesla coil…
But TOSLINK is quite different from I2S. It’s the same data, but I2S uses three signals (Clock, Data, and L/R), while both TOSLINK and SPDIF use only a single channel in which the data is Manchester encoded.
Also, 44.1kHz 16 bit is quite old, 24bit 96 kHz has about 4x the data rate and was also common. As was 7 or so channel surround sound, but that uses compressed data.