[38C3] It’s TOSLINK, over long Distance Fibre.
If you’ve owned a CD player or other piece of digital audio gear manufactured since the 1980s, the chances are highly to has a TOSLINK port on the back. This is a interface that sends I2S digital audio data down a short length of optical fibre, and it’s designed to run between audio gear & an external DAC.
https://blog.benjojo.co.uk/post/sfp-experiment-ultra-long-range-toslink
@Olly42 You heard of Toslink over SFP, now get ready for MIDI over BIDI
@Olly42 Almost as cool as TOSLINK over air.
https://www.youtube.com/watch?v=1H4FuNAByUs