[MisterTea]

> An opto coupler, also known as an opto isolator, allows an electrical signal to pass from one device to another using light, preventing direct electrical connection. *This ensures data flows in a single direction, maintaining the integrity of the air gap.*

I would like to know how they come to such a conclusion as this is either a misunderstanding or an AI solution. The opto isolator does not maintain the air gap. It only provides galvanic isolation which is likely unnecessary in this situation.

Galvanic isolation is useful in situations where you want to isolate circuits from electrical potential issues (ground loops and so on) or isolation from noise and faults.

[bmgxyz]

I think they only care about preventing data flow in one direction while still allowing it in the other. This isn't strictly an air gap, but it fits their use of the term "data diode". The fact that the unidirectional flow of information is achieved through galvanic isolation is probably just a side effect. In the ideal case, no information can flow from the photosensitive element to the LED. A determined attacker could probably exploit lots of side channels here, though.

[idiotsecant]

A single optoisolator will certainly enforce one-way airgap. Two optoisolators are required for tx and rx.

[mhb]

I don't understand your point. Isn't the galvanic isolation implemented in the optoisolator by an air gap between the light transmitter and receiver? Maybe I don't know the definition of air gap?

[MisterTea]

The point is you don't need the opto isolator at all.

[mhb]

That's a separate point. Are you agreeing that if an air gap was needed an optoisolator would be suitable?

[MisterTea]

> Are you agreeing ...

No. "An air-gapped computer or network is one that has no network interfaces, either wired or wireless, connected to outside networks" https://en.wikipedia.org/wiki/Air_gap_(networking)#Use_in_cl...

[mhb]

"For this reason, some new hardware technologies are also available like unidirectional data diodes or bidirectional diodes (also called electronic airgaps), which physically separate the network and transportation layers and copy and filter the application data. "