SFP module (Small Form-factor Pluggable)
SFP modules followed on from GBIC modules and are used in both ethernet and fibre channel switches (and others too), they are usually optical I/O modules although RJ45 copper Ethernet ones are available. Ethernet modules are most commonly 1GB/s but 10GB/s and higher are available. SFP used for Fibre channel can be 1 or 2GB/s but most common is 4GB/s.
All the optical interfaces are either single or multimode fibre terminated on LC connectors.
Although less common, SFP modules can have an RJ45 socket for copper connectivity.