Fiber is a great dependable way to connect the two switches without taking away from your copper ports. Here is some info on the transceivers I have listed for the 7048.   Transceivers Part number, WTRD1, SFP+ SR Optic, 10GbE Multi mode, 850nm, 62.5 micrometers multimode fiber cabling it has a maximum range of 26 meters   Part number, RN84N, SFP+ LR Optic, 10GbE Single mode, 1310nm, 10GBASE-LR has a specified reach of 10 kilometers   Part number, DT87G, SFP+ LRM Optic, 10GbE Long Reach Multimode, 1310nm, 10GBASE-LRM supports distances up to 220 meters(720 ft)   Talking with your sales rep will be the best way to find out which parts are readily available in your area and suite your businesses financial goal.   Another option if you have available copper ports is to LAG multiple ports together to link between the switches. This will provide some redundancy but not the 10Gbe speed.
I'm looking at installing a new core network for two small server rooms and using Powerconnect 7048's in a stack in each room.  I'm not sure how best to connect them though.  The two server rooms are about 40m apart and I am assuming fiber would be preferential over copper at that distance and it would be less susceptible to interference.  I'm thinking I can put the optional 10gb Modules with SFP+ ports in the 7048's but I'm not sure which transceivers or fibre cable I should use for a 10gb connection?, any idea's or recommendation please? Or if I should be doing something else.
What fiber to use between two server rooms for 7048's