If you want to do that sort of thing in a cheap way, then you can.
I'm told a box with two optical NICs in it with only one fibre in it, TX->RX, works quite well, plus a bit of software to wrap around it.
But these sorts of organisations love a bit of bureaucratic regulation, and "certified" devices and that sort of thing, so there's probably not much of a market for a data diode without the paperwork.
On the opto isolated idea - I think there was a QR-code and camera based data transfer tool posted on HN a few days ago!
Data diode hardware isn’t terribly expensive, but the software runs into the hundreds of thousands precisely because these are niche products.
To DIY it you need three NICs (or an optical isolator, which is honestly more work than it’s worth) because the transmitting NIC needs to see a link up before it transmits anything. That link is most easily provided by the second port on the transmitting side.
Developing software to reliably move data across the link, and ensure that it’s properly formatted etc will still be your problem.
I'm told a box with two optical NICs in it with only one fibre in it, TX->RX, works quite well, plus a bit of software to wrap around it.
But these sorts of organisations love a bit of bureaucratic regulation, and "certified" devices and that sort of thing, so there's probably not much of a market for a data diode without the paperwork.
On the opto isolated idea - I think there was a QR-code and camera based data transfer tool posted on HN a few days ago!