High-assurance data diodes
A data diode has two ”sides”; an incoming which can be seen as the insecure side, and an outgoing which can be seen as the secure side.
Some systems which have two different information security zones require different electrical grids. Any hardware which is on the “insecure” (shouldn’t be taken literally; it can simply be the lower of the two) side must be connected to the ”black” electrical grid, and any hardware which is on the ”secure” side must be connected to the ”red” electrical grid.
High-assurance data diodes separate the two sides into two physically different PCB’s internally, and only connect an optical fiber between the two sides (to avoid galvanic leakage). To facilitate the full separation there are data diodes on the market which have separate power supply for the two different internal boards so that one can be connected to the respective black/red power grid.
This complete separation is possible with data diodes which doesn’t provide separate power supplies for both sides as well, using two separate data diodes, each connected to their respective red or black power grid.