Used to specify the speed of fiber optic networks. The base rate (OC-1) is 51.84 Mbps. OC-2 runs at twice the base rate, OC-3 at three times the base rate (155.52 Mbps), etc. Planned rates are: OC-1, OC-3, OC-12 (622.08 Mpbs), OC-24 (1.244 Gbps), and OC-48 (2.488 Gbps).