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

From http://www.techfest.com/networking/wan/sonet.htm