An OC designation on a circuit means Optical Carrier, that is, the circuit is carried over optical fiber. It is typically used to refer to two different transport layers that can be carried over optical fiber ATM or SONET. The baseline rate for OC Circuits is 51.84 Mb/s (oc-1) hence OC-3 is 155.52Mb/s, oc-12 is 622.08Mb/s, oc-48 is 2488.32Mb/s and so on.

OC-192 router interfaces are just now(2nd quarter 2000) becoming commercially available. OC-192 (10Gb/s) circuits are now widely deployed in the US long-haul telecommunications infrastructure and newer submarine cables. Currently interfaces at oc-1536 (80Gb/s) line rates and faster exist in the labs of Major Telco hardware manufactures.