Four different standardized physical implementations of Gigabit Ethernet exist. 1000BASE-SX and 1000BASE-LX are based on fiber optic media. 1000BASE-CX is a shielded copper cable. 1000BASE-T is an unshielded twisted-pair implementation that operates across four pairs of Category 5E wire.
1000BASE-SX, 1000BASE-LX, and 1000BASE-CX are based on fibre channel technology. The group is called 1000BASE-X.
For both the 1000BASE-X and 1000BASE-T physical implementations, frames or idles are transmitted continually in both directions.
Lasers are used for both multimode and single-mode 1000BASE-X fiber implementations.
Inexpensive Vertical Cavity Surface Emitting Lasers (VCSELs) support gigabit transmission across multimode cables that are hundreds ...