We purchased four Fathom-X SPE modules and a switch from Blue Robotics to establish a data link between pressure housings A, B, and C. SPE1 is connected directly to SPE2 via a 100 m twisted-pair cable, and SPE3 and SPE4 are connected in the same way. The switch is located in unit B and links SPE2 with SPE3.
The issue is that communication only works between SPE1 and SPE2 when SPE3 is offline. It seems like there may be crosstalk, as SPE1 can detect both SPE2 and SPE3, which leads to network instability.
Has anyone set up a similar configuration and found a reliable solution?
You can indeed have multiple Fathom-X on the same, shared twisted pair. However length limits to the overall tether can still apply! If you have 100m between SPE1 and SPE2, what are the additional distances? Is the same twisted pair connected to all the Fathom-X modules? I’m not sure what you mean by switch - you have an ethernet switch and are doing normal ethernet signals for some portion of your links?
so far we connected each Fathom-X one by one. 100m twisted pair between 1&2 and 100m between 3&4, two separate cables. Module 2 and 3 are only connected via your 5-port Ethernet switch, together with 3 instruments. If I got you right, you suggest to skip fathom-x module 3 and have modules 1-2-4 all on the same twisted pair cable (200m in total), which would be an easy fix for now. And for our field tests next week.
In the future we plan to have longer cables between each unit. My guess is, that we have some unshielded sections where module 2 and 3 crosstalk and both allow access to the payload instruments, which causes the network problems. This is harder to fix, since we have to locate where the crosstalk occurs and to replace some cables. But hopefully work as well…
Maybe a diagram would help illustrate your setup. I don’t think you’re going to be able to run connections of that length without the Fathom-X. Each tether can only carry one fathom-x signal, through a single twisted pair. Having a second pair of Fathom-X units talking through the same tether on a different pair does not work. The Fathom-X is multi-drop, so if your twisted pair goes from one to the next unit, 100m away, the next tether twisted pair should connect to the same points and go on to the third unit in the chain.
How far apart are module 2 and 3?
What total bandwidth do you need from between your enclosures and to the topside?