This is a great question. We haven’t actually done any testing with two independent sets of Fathom-X in one cable. I would guess that there would be some cross-talk since the pairs aren’t shielded and that would definitely have detrimental effects. If the cross-talk was strong enough, the boards could potentially communicate with each other on a single network.
We’ve done several tests where we attached multiple devices to the same network of Fathom-Xs. They can be connected in parallel so, for instance, you could have two on the ROV (one for ROV and one for payload) and have them connected to the same twisted pair. Then, the board at the surface would be able to access both devices. You could add a network switch or another Fathom-X at the surface to allow another surface computer to connect to the network.
What type of sensor are you using, if you don’t mind me asking? What sort of bandwidth does it use?