Thanks @greg_f I really appreciate the info and support.
The CA thread is a good resource, although probably more technical than I need. My goal is to try a better SFP module to see if it will improve the fibre feed to my Lumin U2. I'd read that Finisar modules were recommended by many on this site.
I'll reach out to Cisco to see if I can get the specs for my Catalyst 2960 switch, and see what modules might be compatible -- and which might offer a SQ improvement.
Many thanks,
JAMES.