I would expect that they are using a Fiber Backbone and have Optical to Wire Switches radiating out from the Optical Fiber Backbone.
If that is the case you just need to run another Optical Fiber cable to the new location insert a Suitable Switch and setup the wired computers.
However if they are running a Full Optical to the Desktop system it's horrendously expensive in the actual NIC Cards that are used in the computers.
OH if you have not worked with optical Fiber previously the tools required are not cheap and you need to develop a feel for the cable so you don't crush it or otherwise damage it when you crimp on the connectors that are required.
Basically if you have not worked with Optical Fiber previously this probably isn't a good [b]Learning Position[/b] to be in. As Optical Fiber transmits light there are no such things as Crossover Cables and anyway modern Switches/Hubs have not used Crossover cable for ages when you add extra Switches to an existing LAN.
I have worked on both types of setups and to be perfectly honest the only type of place that Needs Optical Fiber tot he Desktop are Scientific Institutions dong work that requires a High Speed LAN. In those cases because of what they are doing cost isn't overly important when compared to what a mistake costs because of a glitch in the system or the necessary Data not being available when it is required.
As the above posted said you really need to know a lot more about this Individual LAN and how it is configured and what it is configured for. So you'll need to ask lots of questions and need to know what to ask as this isn't for beginners particularly if they are using it in a Production Environment at the moment. Any mistakes are expensive in both Materials and Time. ;)
Col