SONET/SDH Data Rates
SONET (Synchronous Optical NETwork) and SDH (Synchronous Digital Hierarchy) are, respectively, the North American and international standards for physical layer optical communication. SONET, adopted by the American National Standards Institute, defines a base rate (OC-1) of 51.84 Mbps. Faster rates are designated as multiples of the base rate, and are referred to as Optical Carrier levels. The OC number specifies the multiple of the base rate at each level. As recommended by the International Telecommunication Union, SHD defines a base rate (STM-1) of 155.52 Mbps.
Line rates refer to the total bandwidth of the physical layer. Payload and overhead rates refer, respectively, to the useful data capacity and OAM&P (Operations, Administration, Maintenance, and Provisioning) requirements at each level.
| SONET | SDH | Line Rate (Mbps) | Payload Rate (Mbps) | Overhead Rate (Mbps) |
|---|---|---|---|---|
| OC-1 | - | 51.840 | 50.112 | 1.728 |
| OC-3 | STM-1 | 155.520 | 150.336 | 5.184 |
| OC-12 | STM-4 | 622.080 | 601.344 | 20.736 |
| OC-48 | STM-16 | 2488.320 | 2405.376 | 82.944 |
| OC-192 | STM-64 | 9953.280 | 9621.504 | 331.776 |
| OC-768 | STM-256 | 39813.120 | 38486.016 | 1327.104 |