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Glossary of broadband terminology: O

OC3

An OC3 is a 155 Mbps connection

Open Systems Interconnection

A seven-layer architecture model for communications systems; the OSI model was created by the International Standards Organization (ISO).

Operations, Administration, and Maintenance

A group of network management functions that proved network fault notification, performance information, and diagnosis functions.

Optical Carrier

Base unit found in the SONET hierarchy; the "x"represents increments of 51.84 Mbps (so, OC-1 is 51.84 Mbps, OC-3 is 155Mbps, and OC-12 is 622 Mbps). See also Synchronous Optical Network.

Optical Network Unit

A form of access node that converts optical signals transmitted via fiber to electrical signals that can be transmitted via coaxial cable or twisted pair copper writing to individual subscribers.