One of the offices where I work has just installed a new LAN; the switch is a D-Link 16 port 10/100 with an add-in 2 port gigabit module; the ports on the gigabit module are rectangular, about 30mm x 10mm (like little letterboxes) with a sort of double-headed arrow symbol on them.
The documentation is almost non-existent, I can’t find anything on DLINK.com and I don’t know what sort connector this is (or even whether it’s copper or fibre.
Can anyone out there help?
Sounds like a USB port. Why it’s on a gigabit module is a bit of a stumper, unless it’s for a console connection for configuring things. Either that or it’s a FireWire connection.
No, it’s much bigger than a USB port; it’s some sort of gigabit port, but I don’t know what sort.
(I should have mentioned that the arrow symbol is on a little metal door that is spung to open inwards).
You’re right, 30mm is a bit large for USB. I guess I should have done the conversion to inches before spouting off my knee-jerk reaction.
Another possibility is some sort of proprietary connection to allow stacking two or more switches together. That’s not at all uncommon in the industry, but I’d have to do a bit more research before I can say for sure. Do you by any chance have the model number of the DLink switch you are working with?
Sounds like a GBIC (Gigabit Interface Converter) port. A GBIC is a small rectanglar piece that can connect to the end of a standard fiber optic cable. After attaching the fiber optic cable to the GBIC, you can you can insert the GBIC into that slot to make a connection.
This product page appears to have some pictures.
Just in case you need to verbally discuss them, it’s normally pronounced “GEE-bik” 
That’s the fella! it’s GBIC socket; so it looks like I can also get one that will accept copper (if true, this is good, as I can then patch it through the regular cabling instead of having to trail the fibre optic cables out of the front of the rack housing).
OK, I think I found the module you are dealing with. Look here. It would appear to be using a 1000Base-SX ethernet connection over fiber. If that is indeed the case look for some 1000Base-SX cabling. Good luck.
Well-- keep in mind that the one that accepts copper is 1000baseT. Be careful not to trivialize that. You need something on the other end that is also 1000baseT, and in the industry, GB ethernet over copper is still largely shunned, and that should say something given what a PITA fibre is.
WARNING: PDF link
Running 1000baseT
I suppose I could use fibre; the rack is right next to where the file server is going to be (and it’s the server that specifically wants the gigabit link); it would just be nice (from the point of view of the client) not to have any trailing cables.