1. Short for Optical Carrier, OC is a term used to specify a speed of fiber-optic networks. Below is a listing of OC types and the corresponding speeds for each of those types.
OC-1 = 51.85 Mbps
OC-3 (STS-3 or STM-1) = 155.52 Mbps
OC-12 (STS-12 or STM-4) = 622.08 Mbps
OC-24 (STS-24 or STM-8) = 1.244 Gbps
OC-48 (STS-48 or STM-16) = 2.488 Gbps
OC-192 (STS-192- or STM-64) = 9.952 Gbps
OC-768 = 40 Gbps
2. OC is also an abbreviation sometimes used for overclocking.