Coriant originates from the Transmission Technology department of
Siemens based in Munich, Germany (Übertragungstechnik - ÜT as it was called in the 1990s). In those days the technology evolved from
Plesiochronous Digital Hierarchy (PDH) to
Synchronous Digital Hierarchy (SDH) in the
STM-4 /
STM-16 (2.5 Gbit/s) level. In the late 1990s and early 2000s
DWDM emerged to allow for even higher transmission capacity (in the
terabit per second region). This technology is also named
optical transport network (OTN), where a set of multiplex and encapsulation hierarchies is standardized. == References ==