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/