OC48

OC-48 stands for Optical Carrier level 48, a SONET (Synchronous Optical Network) line rate with a nominal payload of 2.48832 gigabits per second. It is the signal corresponding to STS-48 in the SONET hierarchy and, in the SDH (Synchronous Digital Hierarchy) framework, is equivalent to STM-16. OC-48 is part of a family of optical carrier levels that scale by the basic STS-1 rate of 51.84 Mbps.

An OC-48 signal is formed by multiplexing 48 STS-1 channels (each 51.84 Mbps) using the SONET framing structure, which includes overhead for framing, signaling, and management. The resulting line rate is 2.488 Gbps, but the usable payload is reduced by overhead. The optical signal is carried over fiber, typically in the 1310 nm or 1550 nm windows, and modern networks frequently use dense wavelength-division multiplexing (DWDM) to combine multiple OC-level channels onto a single fiber pair.

Reach and deployment depend on fiber quality, dispersion, amplification, and regeneration. OC-48 links are commonly used in regional and backbone networks, with DWDM and optical amplifiers extending their reach across long-haul paths. As technology progressed, higher-rate standards such as OC-192 (approximately 9.95 Gbps) and beyond have largely supplanted OC-48 in new deployments, though OC-48 remains in service in some legacy networks and equipment. OC-48-compatible equipment supports interoperability within the SONET framework and, by extension, the SDH ecosystem in regions that used both standards.