scope:

The optical transport hierarchy (OTH) supports the operation and management aspects of optical networks of various architectures, e.g., point-to-point, ring and mesh architectures.

This Recommendation defines the interfaces of the optical transport network to be used within and between subnetworks of the optical network, in terms of:

- optical transport hierarchy (OTH);

- functionality of the overhead in support of multi-wavelength optical networks;

- frame structures;

- bit rates;

- formats for mapping client signals.

The interfaces defined in this Recommendation can be applied at user-to-network interfaces (UNI) and network node interfaces (NNI) of the optical transport network. It is recognized for interfaces used within optical subnetworks, aspects of the interface are optical technology dependent and subject to change as technology progresses. Therefore, optical technology dependent aspects (for transverse compatibility) are not defined for these interfaces to allow for technology changes. The overhead functionality necessary for operations and management of optical subnetworks is defined.