[crote]

Such 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/st121hd2...

[1]: https://www.blackmagicdesign.com/products/miniconverters/tec...

[toast0]

If you need 4x channels, it sounds like a job for QSFP? HDMI is already differential signalling, so you don't need to do that, but you might still need level shifting.

Probably a box on the source end to manage DDC and strip HDCP.

[raron]

> You won't be able to source any kind of protocol translation chip

I think many of those chips are simple off-the-shelf parts. Probably you would need special licenses only to decode HDCP.

If you have an FPGA, you could even create valid Ethernet frames and send the data / video stream over any standard switch / media converter as long as you have enough bandwidth and no packet loss. (10G would be enough for FullHD and 25G for 4K if you make it a bit smarter and can strip the blanking interval.)

[Doohickey-d]

There's even cheaper versions of this now, "fiber" HDMI cables with the electronics in the HDMI plugs themselves, no additional power required. They go up to 100m length. I do wonder how these work, since I've never seen a good teardown of one.

[15155]

> You won't be able to source any kind of protocol translation chip

This is called an FPGA.