Transponders are components that convert signals from one protocol to another. In WDM, transponders operate in one of two ways:
Converting from OCN to OCH
Converting from OCH to OCN
These two cases are modeled in slightly different ways.
Classes and relationships for OCN-OCH and OCH-OCN transponders shows the classes and relationships for transponders converting from OCN to OCH and from OCH to OCN.
In the case of translating from OCH to OCN, the internal forward error correction (FEC) port is modeled by a TransponderInFecPort since alarm conditions can be raised on this port.