I have a number of Arduino devices that are connected using simple two core cable which is carrying 12-14v DC. What I would like to do is send ethernet traffic over the same wire as is done using Power Line adapters over mains wiring (using wifi and running Ethernet is not an option in my case). I have seen examples were people have taken mains PLC devices removed the high voltage components and used them in a low volt DC setting, so it appears this does work (however these are large boards and a hack to demonstrate an idea).
Can anyone point me to an off the shelf or a circuit diagram for a low voltage (12-14v DC) PLC ethernet modem for this specific use case. The smaller the better in my case.