Hi, 

I'm splitting our server rack cabinet between two floors in our
building and want to connect them with a high-speed optical link
(optical to avoid interference from the machinery that we operate). I
can get Dell switches with SFP slots for optical transcievers, but um
unsure whether to get the SX (Short-wave) or LX (Long-wave) models.

What's the difference? Which is more suited to a run of around 30M?

Hello

SX is for lines up to 100m lenght (which is normally enough in a
datacenter or a building).
LX is for lines up to 10km length (typical application: Carrier/Metro-Ethernet).
ZX is for lines up to 60-80km length (typical application: longhaul
connections of carriers)

Be aware that you shoud use multimode-fibrecables with SX and
singlemode-fibrecables for the other two.

Cheers
Roman

thanks for this! how do i accept the answer?

no idea. it's the first time i used google answers.

i guess we have to ask for it. ;)