This draft European Telecommunications Standard (ETS) specifies the optical interfaces for equipment and systems relating to the Synchronous Digital Hieratchy (SDH).
PRETS 300 232-1992 history
1993PRETS 300 232-1993 Transmission and Multiplexing (TM); Optical Interfaces for Equipments and Systems Relating to the Synchronous Digital Hierachy
1992PRETS 300 232-1992 Transmission and Multiplexing (TM); Optical Parameter for Interfaces for the Synchronous Digital Hierarchy (SDH)