Unidirectional Network
en.wikipedia.org
en.wikipedia.org
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:
With a data diode, the physical medium is probably a short run with no packet loss anyway.