Optical transport network interface structure
The optical transport network as specified in ITU-T Rec. G.872 defines two interface classes:
Inter-domain interface (IrDI);
Intra-domain interface (IaDI).
The OTN IrDI interfaces are defined with 3R processing at each 838d39i end of the interface.
The Optical Transport Module-n (OTM-n) is the information structure used to support OTN
interfaces. Two OTM-n structures are defined:
OTM interfaces with full functionality (OTM-n.m);
OTM interfaces with reduced functionality (OTM-0.m, OTM-nr.m).
The reduced functionality OTM interfaces are defined with 3R processing at each 838d39i end of the
interface to support the OTN IrDI interface class.
ITU-T Rec. G.709/Y.1331 (03/2003)
Basic signal structure
The basic structure is shown in Figure 6-1.
Clients (e.g., STM-N, ATM, IP, Ethernet, OTN ODUk)
OPUk
ODUkP
ODUk
ODUkT
OTUkV OTUk OTUkV OTUk
OCh OChr
OMSn
OPSn
OTSn
G.709/Y.1331_F6-1
OTM-n.m OTM-0.m, OTM-nr.m
Full functionality Reduced functionality
OTM interface OTM interface
Figure 6-1/G.709/Y.1331 Structure of the OTN interfaces
OCh substructure
The optical channel layer as defined in ITU-T Rec. G.872 is further structured in layer networks in order to support the network management and supervision functionalities defined in ITU-T Rec. G.872:
The optical channel with full (OCh) or reduced functionality (OChr), which provides
transparent network connections between 3R regeneration points in the
OTN.
The completely or functionally standardized optical channel transport unit (OTUk/OTUkV)
which provides supervision and conditions the signal for transport between 3R regeneration
points in the OTN.
The optical channel data unit (ODUk) which provides:
tandem connection monitoring (ODUkT);
end-to-end path supervision (ODUkP); and
adaptation of client signals via the Optical Channel Payload Unit (OPUk).
Full functionality OTM-n.m (n ≥ 1) structure
The OTM-n.m (n ≥ 1) consists of the following layers:
optical transmission section (OTSn);
optical multiplex section (OMSn):
full functionality optical channel (OCh);
completely or functionally standardized optical channel transport unit (OTUk/OTUkV);
optical channel data unit (ODUk).
ITU-T Rec. G.709/Y.1331 (03/2003)
Reduced functionality OTM-nr.m and OTM-0.m structure
The OTM-nr.m and OTM-0.m consists of the following layers:
optical physical section (OPSn);
reduced functionality optical channel (OChr);
completely or functionally standardized optical channel transport unit (OTUk/OTUkV);
optical channel data unit (ODUk).
Information structure for the OTN interfaces
The information structure for the OTN interfaces is represented by information containment relationships and flows. The principal information containment relationships are described in Figures 6-2, 6-3 and 6-4. The information flows are illustrated in Figure 6-5.
For supervision purposes in the OTN, the OTUk/OTUkV signal is terminated whenever the OCh signal is terminated.
Client
ODUk tandem connection
OTUk[V] OTUk[V]
section OH
OCh
OPUk
ODUk path ODUk
PMOH
ODUk
TCMOH
OPUk
OH
OPUk payload
OPUk
ODUk TC L1
ODUk TC Lm
ODUk
TCMOH
OTUk[V] FEC
ODUk
TCMOH 1 to 6 levels
of ODUk
tandem
connection
monitoring
OCh
OCG-n.m
OMU-n.m
OTM-n.m
OH
OCCp OCCp
OMSn
OH
OTSn
OH
OOS
OCh payload
OCCp OCCp OCCp
OMSn payload
OTSn payload
G.709/Y.1331_F6-2
Figure 6-2/G.709/Y.1331 - OTM-n.m principal information containment relationships
ITU-T Rec. G.709/Y.1331 (03/2003)
Client
ODUk tandem connection
OTUk[V] OTUk[V]
section OH
OPUk
ODUk path ODUk
PMOH
ODUk
TCMOH
OPUk
OH
OPUk payload
OPUk
ODUk TC L1
ODUk TC Lm
ODUk
TCMOH
OTUk[V] FEC
ODUk
TCMOH 1 to 6 levels
of ODUk
tandem
connection
monitoring
OChr OCh payload
OTM-0.m OPS0
G.709/Y.1331_F6-3
Figure 6-3/G.709/Y.1331 - OTM-0.m principal information containment relationships
Client
OPUk
ODUk
OPUk
OH
OPUk payload
ODUk tandem connection
OTUk[V] OTUk[V]
section OH
OChr
OCG-nr.m OCCp
OTM-nr.m
ODUk path
ODUk
TCMOH
OCCp
PMOH
OCCp
OPUk
ODUk TC L1
ODUk TC Lm
ODUk
TCMOH
OTUk[V] FEC
OCh payload
OCCp OCCp
OPSn
ODUk
TCMOH 1 to 6 levels
of ODUk
tandem
connection
monitoring
G.709/Y.1331_F6-4
Figure 6-4/G.709/Y.1331 - OTM-nr.m principal information containment relationships
ITU-T Rec. G.709/Y.1331 (03/2003)
Client Client_CI
ODUkP/CL
OPUk OCh_AI
ODUkP
ODUk
ODUkT/ODUk
ODUkT
ODUk
OTM-0
OTUk/ODUk
OTUk
OTUk
OCh/OTUk
OChr
OChr_CI
n OPS/OChr
OPS_AI OCG-n
OPS
OPS_CI
OTM-0
OTM-nr
OTM-nr (n>1)
OTUkV/ODUk
OTUkV
OTUkV
OCh/OTUkV
OCh
OCh_CI
OCh
OCh_CI
OCh_CI_PLD
OMS/OCh n
OCG-n OMS_AI
OMS
OMS_CI_PLD
OMU-n
OMS_CI
OTS/OMS
OTS_AI
OTS_CI_PLD
OTS
OTS_CI
OTM-n
OTM-n (n
OCh OH
OCh OH
OCh OH
OCh_CI_OH
OMS OH
OMS_CI_OH
OMS OH
OTS OH
OTS_CI_OH
COMMs
OSC
G.709/Y.1331_F6-5
NOTE - The model in this figure is for illustrative purposes only. represents an optical wavelength.
Figure 6-5/G.709/Y.1331 Example of information flow relationship
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