Optical Carrier

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What Does Optical Carrier Mean?

An optical carrier is the standard unit of measure for the rate of transmission bandwidth for data being carried by Synchronous Optical Networking (SONET) fiber-optic networks.


Optical carrier transmission rate signifies the speed of a fiber-optic network and is abbreviated as OCx, where x is a variable representing a multiplier whose base rate is 51.84 Mbps. Therefore, an OC-1-rated fiber network would have a transmission rate of 51.84 Mbps, while an OC-3-rated network would have a speed of 155.52 Mbps.

Techopedia Explains Optical Carrier

Optical carriers are standardized sets of specifications for transmission bandwidths for SONET fiber networks. The following is a list of all the OC levels available and their corresponding speeds:

    • 1. OC-1 (STM-0): 51.84 Mbps


    • 2. OC-3 (STM-1 or STS-3): 155.52 Mbps


    • 3. OC-9 (STM-3): 466.56 Mbps


    • 4. OC-12 (STM-4): 622.08 Mbps


    • 5. OC-18 (STM-6): 933.12 Mbps


    • 6. OC-24 (STM-8): 1244.16 Mbps


    • 7. OC-36 (STM-12): 1866.24 Mbps


    • 8. OC-48 (STM-16): 2488.32 Mbps


    • 9. OC-192 (STM-64): 9953.28 Mbps


    • 10. OC-768 (STM-256): 40 Gbps


    11. OC-3072 (STM-1024): 160 Gbps

The Synchronous Transport Module (STM) is equivalent to the OC defined in the Synchronous Digital Hierarchy (SDH). The STM refers to how the data is being framed or arranged for transport.


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Margaret Rouse
Senior Editor
Margaret Rouse
Senior Editor

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.