What is OC-1, OC-3, OC-12, OC-24, OC-48?

OC-1, OC-3, OC-12, OC-24, OC-48 — Optical Carrier transmission speeds, used in fiber optic networks conforming to SONET standard. OC-1 is 51.85 Mbps. Higher levels are multiples of that speed.