This Recommendation provides physical layer inter-domain interface (IrDI) specifications for
optical networks which may employ wavelength division multiplexing (WDM). The physical layer
specifications are valid for non-OTN IrDIs, while also allowing application on OTN IrDIs
according to [ITU-T Rec. G.709]/Y.1331. In the case of a non-OTN IrDI, OTN management
capabilities are not required. The IrDIs within the optical transport network (OTN) are provided by
unidirectional, point-to-point, single and multichannel line systems. Their primary purpose is to
enable transversely compatible interfaces to span the boundary between two administrative
domains. The IrDI specifications include intra-office, short-haul and long-haul applications, without
line amplifiers.
NOTE – For the purposes of this Recommendation, the term "Administrative domain" is understood to mean
the extent of resources which belong to a single player such as a network operator, a service provider, or an
end-user. Administrative domains of different players do not overlap among themselves.
The specifications are organized according to application codes, which take into account the many
possible combinations of channel counts, optical tributary signal types, span distances, fibre types
and system configurations. The reference configuration and application codes form the foundation
for specifying the optical networking physical layer parameters.
In this Recommendation the use of an optical supervisory channel has not been considered. Future
versions and other new Recommendations will further address this aspect of the OTN, possibly
involving an arrangement of optical network elements on either side of an optical subnetwork
interface that is more complex than point-to-point. For these applications, different parameters
beyond those specified for a point-to-point configuration may be required.
This Recommendation presumes that the optical tributary signals transported within optical
channels are digital rather than analogue. Specifications for systems enabling transport of analogue
optical tributary signals are for further study.