Hi @gon2000, I need to apologise for having misunderstood you, and because I had also misunderstood how the Fathom-X actually works.
My mistake
You’re asking about PLC, as in Power-Line Communication, which I hadn’t heard of before, so I was thinking about PLC as in Programmable Logic Controller (which are ruggedised relatively simple computers that are commonly used in industry).
Corrected Explanation
The Fathom-X uses the HomePlug AV protocol to convert ethernet communication into high-frequency AC waveforms, which are then decoded again on the other end by a paired HomePlug AV device. In the context of a BlueROV2, there is one Fathom-X on each end of one twisted pair of the tether - one inside the ROV, and one up at the top computer. In general, the HomePlug standards are an example of Powerline Communication, so they’re a type of PLC.
Fathom-X Suitability?
As for your actual question, the Fathom-X is intended for physically sending up to 200Mbits/s, and when sending packets using the internet protocol that ends up being about 80Mbits/s of actual data transfer, so they’re well-suited to sending things like streamed video and telemetry data.
I’m unsure of the voltage that the Fathom-X boards actually use on the tether (AC) side, but I don’t believe it to be as high as 230V, so if you need to interface with something that uses 230V then you’ll need to use a transformer to convert the output from a Fathom-X up to the required voltage, and to step down communication from the other direction into a voltage that won’t damage the Fathom-X or surrounding electronics. I have asked internally for confirmation on the communication voltage and will get back to you.
Recommendation
If you have a mains-level power line (e.g. >110V AC), it is probably preferable (and safer) to use a product that’s intended for that. Try searching online for “HomePlug Powerline adaptor” - there should be several options that can plug directly into a mains electrical socket and give you an ethernet port that you can plug into.