14.7 Optical Performance Monitoring
607
IP
Electrical signals
OC - N/STM -X
Optical Channel (OCh)
Optical Multiplex
Section (OMS)
Optical Transport
Section (OTS)
Ethernet
Optical Channel
Payload Unit (OPU)
Optical Channel
Data Unit (ODU)
Optical Channel
Transport Unit (OTU)
Fibre Channel
Fig. 14.17 Three-layer model for a simple link in an OTN and the three OCh sublayers
Optical
mux
Optical
demux
Optical
amplifiers
OMS
OCh
OTS
OTS
OTS
Optical
channels
Optical
channels
Fig. 14.18 The OMS layer represents a link carrying wavelengths between multiplexers or OADMs;
the OTS layer relates to a link between two optical amplifiers
Optical channel payload unit The OPU frame structure contains the client signal
payload and the overhead necessary for mapping any client signal into the OPU.
Mapping of client signals may include rate adaptation of the client signal to a constant
bit-rate signal. Examples of common signals are IP, various forms of Ethernet,
Fibre Channel, and SONET/SDH. The three payload rates associated with the OPU
sublayer are 2.5, 10, and 40 Gb/s. These correspond to standard SONET/SDH data
rates (OC-48/STM-16, OC-192/STM-64, and OC-768/STM-256, respectively) but
may be used for any client signal.
Optical channel data unit The ODU is the structure used to transport the OPU.
The ODU consists of the OPU and the associated ODU overhead and provides pathlayer connection monitoring functions. The ODU overhead contains information that