OCx, or Optical Carrier, is a standard for the transmission of data over optical fiber networks. Developed as part of the Synchronous Optical Networking (SONET) framework in the United States, it is equivalent to the Synchronous Digital Hierarchy (SDH) framework used elsewhere. Both SONET and SDH are standardized methods for transferring multiple digital bitstreams over optical fiber using lasers or LEDs.
The “x” in OCx refers to the level of the standard, with each level having a specified data rate. Here are some of the common OC levels:
- OC-1: 51.84 Mbps
- OC-3: 155.52 Mbps (often just referred to as STM-1 in SDH)
- OC-12: 622.08 Mbps (STM-4 in SDH)
- OC-24: 1.244 Gbps (non-standard rate but occasionally referenced)
- OC-48: 2.488 Gbps (STM-16 in SDH)
- OC-192: 9.953 Gbps (STM-64 in SDH)
- OC-768: 39.813 Gbps (STM-256 in SDH)
Some key points to consider about OCx:
- Scalability: The OC framework is scalable, allowing networks to upgrade by adding additional OC levels as data transmission requirements grow.
- Multiplexing: Lower OC levels can be multiplexed into higher OC levels. For example, four OC-3s can be multiplexed to form one OC-12.
- Infrastructure: The transition from one OC level to another often requires a change or upgrade in infrastructure, including transceivers and multiplexers.
- Applications: Different OC levels find applications in different scenarios. For example, OC-3 and OC-12 are commonly used for enterprise connections and internet backbones, while OC-48 and OC-192 are used in larger backbone and intercontinental connections.
OCx and its associated standards have played a significant role in the development and expansion of modern telecom and data communication networks, allowing for high-speed, reliable, and scalable data transmission over optical fiber. As technology progresses, even higher data rates are being achieved using more advanced modulation techniques and fiber technologies beyond the traditional OCx levels.