Used throughout Cisco's Product range to provide versitility amoungst their Gigabit uplinks.
Cisco offers a range of Gigabit Interface Converters (GBICs) and Small Form-factor Pluggable (SFP) for Gigabit Ethernet use. These small, modular optical interface transceivers offer a convenient and cost effective solution for the adoption of Gigabit Ethernet in data center, campus, metropolitan area access and ring networks, and storage area networks.
Have a look at 
Cisco's GBIC Range
Also Look at SFP
2 pages link to GBIC:
