You could. Commercial diodes comes with special drivers and I've seen at least one with a modified nic that could sync with only one way communication. There

You could. Commercial diodes comes with special drivers and I've seen at least one with a modified nic that could sync with only one way communication. There are also software components they usually come with as the proxying is somewhat tricky with one direction communication. The real advantage of the fiber is the use can see that there is no way for a return signal, with normal Ethernet you need to have a special cable, a very special one, if it's replaced with something different the diode may be compromised. It becomes a trust issue. The diodes from some companies are very expensive too, 6 figure price tags with all the various defense type certifications.