Indepently from any other certification or approval, both the governments of the Netherlands and Germany have evaluated the hardware data diode that is part of the Fox DataDiode. Both countries have the AQUA status and have approved the product to protect their government networks up to and including Secret. Details on these approvals can be found here.
The Fox DataDiode can be deployed in these EU member states, even to connect a state secret network to the Internet.
The EU AQUA certification/approval scheme does not apply to non-cryptographic products, otherwise the hardware data diode would have ‘automatically’ been approved for use up to and including EU Secret.