Unidirectional networks, or data diodes, are used extensively in high-assurance security for purposes like these:

https://www.opswat.com/blog/why-data-diodes-are-essential-is...

Strongest designs are done with light such as fiber or infrared. A number of products were analyzed and pentested by evaluators and intelligence agencies with resulting EAL7+ certification, the highest. Link below lists some of the products.

https://www.securitywizardry.com/index.php/products/boundary...

Owl's page has some more applications:

https://www.owlcyberdefense.com/

Like the Tesla Valve...

https://en.wikipedia.org/wiki/Tesla_valve

Remember the "The Simpsons Already Did It" episode of South Park? I feel like all inventors have to have a similar "Nikola Tesla Already Did It" dread when they think they've invented something. Is there anything that guy didn't do?

How do they assure unidirectional transfer with out any feedback in reverse direction (TCP Acks for example ?).

Send a manifest and checksums as part of the transfer, then the receiving end can give a summary of what didn’t work.

With a data diode, the physical medium is probably a short run with no packet loss anyway.