What kind of network? What kind of hardware/software protocol? What distance ?

Surely you realize that your question is too general to answered meaningfully.

TTFN (ta ta for now)
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Our preferred architecture would be to run a fiber connection to the other building and install a switch. There are lots of options available, however. It mostly depends on the required connection speed, number of devices, and distance (like IRStuff said).

Brad Waybright

The more you know, the more you know you don't know.

<my opinion>The main</my opinion> reason to run fiber is that it provides electrical isolation, so you do not need to figure out surge protection.
Higher data speeds are possible than for fiber, which you might or might not need.

Thank you for the replies. I understand now, we would take a fibre from the existing switch to the new location and install a new switch here. We would then connect our devices ( computers, voip phones etc) into this new switch.

Thanks again

IF the distance is bellow 90 meters you can actually use metalic cable instead of optic.
If you are going to use fiber optical cable you need to check what kind of cable is the best for you (Multimode or Monomode)
Check if you have the right transceiver to match the cables or if you need to pruchase some media converters.
Check if there is enough space in the rack for the optical distribution box and switchs.
Check the cost for the splicing and testes.