In reply to a post by Pheasant:

Did you move ahead with this or make any progress?

OK, I have made something of a decision here. The main underground section will be in Cat6 Steel Wire Armoured cable. At the remote end, I will have a switch with an SFP connection and fibre to a Fibre-to-Copper Converter, such as the MikroTik RBFTC11.

Principal factors on this decision are that I am very happy with CAT6 and I have no functional need for fibre other than for galvanic isolation between remote buildings. I also think that SWA will be more robust during the build phase than helically armoured fibre.

Thanks for circling back with an update. 🙏

I have an outbuildings >100m from house. I used CAT5E I get 1GbE across to it no problem, with a patch panel connection at each end. The cable is available from screws and the like for not much money. It does have a separate earth spike,.

It passes through my garage, where one of the patch panels is. This is 20m .from the house, I get 2.5GbE to the garage,,along same cable, without any patch panel links. Again another earth spike.

I think 1000feet of cable was <£30.

Many people forget that UTP ethernet is already galvanically isolated at both ends between the cable and electronics, required to accommodate 1.5kV AC RMS 50/60Hz for 60 sec / 2.25kV DC for 60 sec / 10 2.4kV pulses as defined in RFC 60060. If that gets exceeded between house and outbuilding with T-NCS you will likely have more to worry about that replacing odd bits of networking kit.

In reply to a post by fleddy:

... It does have a separate earth spike,.

Again another earth spike.

Why the earth spikes? And what are you earthing? Is it cable armour? Or other parts of the kit?

Earth spikes seems to be the way to cause problems of transfer potential which is what I want to eliminate, but it depends on what your earthing scheme is.

In reply to a post by tdw42:

Many people forget that UTP ethernet is already galvanically isolated at both ends between the cable and electronics, required to accommodate 1.5kV AC RMS 50/60Hz for 60 sec / 2.25kV DC for 60 sec / 10 2.4kV pulses as defined in RFC 60060. If that gets exceeded between house and outbuilding with T-NCS you will likely have more to worry about that replacing odd bits of networking kit.

Sorry, I got carried away. My electrics are T-NS, but we are bonded as though T-NCS.

Re the isolation, how is this achieved? Are the RJ45's connected to little signal transformers or capacitors with a good voltage rating?

In reply to a post by DFScale:

Sorry, I got carried away. My electrics are T-NS, but we are bonded as though T-NCS.

Either still have a direct bond between the two ends.

Re the isolation, how is this achieved? Are the RJ45's connected to little signal transformers or capacitors with a good voltage rating?

Both, the data passes through transformers, the termination ground has a capacitor to the local signal ground. See Figure 7 in https://resources.altium.com/p/gigabit-ethernet-101-... as an example.

Even PoE is galvanically isolated, the device power supply electronics have an output transformer so again there no connection between the cable and generated supply.

In reply to a post by DFScale:

OK, I have made something of a decision here. The main underground section will be in Cat6 Steel Wire Armoured cable. At the remote end, I will have a switch with an SFP connection and fibre to a Fibre-to-Copper Converter, such as the MikroTik RBFTC11.

Sorry, I don't understand this. The MikroTik converter you show has an RJ45 port and an SFP port, and you say you will bring fibre into that (presumably with a 1000baseLX SFP). What will the other end of that fibre plug into?

Are you using the Mikrotik in effect as a sort of sacrificial lightening arrester?

It seems to me that if there's going to be fibre anywhere, then between buildings is where it would be better deployed - but I don't think I have the complete picture of what's going on here.

In reply to a post by candlerb:

Sorry, I don't understand this. The MikroTik converter you show has an RJ45 port and an SFP port, and you say you will bring fibre into that (presumably with a 1000baseLX SFP). What will the other end of that fibre plug into?

Switch with SFP connector
1000baseLX SFP
Fibre
Mikrotik convertor
CAT6

In reply to a post by candlerb:

Are you using the Mikrotik in effect as a sort of sacrificial lightening arrester?

It is not intended to be sacrificial. Just galvanic isolation

In reply to a post by candlerb:

It seems to me that if there's going to be fibre anywhere, then between buildings is where it would be better deployed - but I don't think I have the complete picture of what's going on here.

Obvs not. I have some very busy trenchwork and I am not convinced about Helical Wire Armouring for fibre vs SWA for CAT6

I would probably choose a PVC duct and non-armoured, outdoor grade fibre. But clearly you've weighed up the pros and cons for your installation, which is what matters.