In an optical transport network (OTN), an optical channel for transporting optical data units (ODUs), which comprise native frames encapsulated in digital wrappers. ITU-T Recommendation G.709 specifies three line rates, which are listed in Table O-2, alongside their corresponding SDH/SONET line rates.

Table O-2: G.709 Line Rates and Corresponding SDH/SONET Line Rates

G.709		SDH/SONET
Interface	Line Rate	OC/STM Level	Line Rate
OTU-1	2.666 Gbps	OC-48/STM-16	2.488 Gbps
OTU-2	10.709 Gbps	OC-192/STM-64	9.953 Gbps
OTU-3	43.018 Gbps	OC-768/STM-256	39.813 Gbps

G.709 also specifies an interface for 10 GbE clients, utilizing the same digital wrapper, which results in a line rate of 11.095 Gbps. See also 10GbE, channel, digital wrapper, encapsulate, frame, ITU-T, line rate, ODU, OTN, SDH, and SONET.