OADM
OADM (pronounced "oudamm") is an o ptischer A dd- D ROP M ultiplexer as an assembly in remote optical transport networks .
OADM are used in optical transmission systems operated with wavelength division multiplexing for the realization of branches. They allow wavelengths coming from a branch to be fed to the main fiber (add) and wavelengths from the main fiber to the branching fiber (tributary) to be carried away (drop). Conventional OADMs receive an unchangeable configuration through structural adaptations during manufacture, which determines which wavelengths are supplied and removed. A subsequent change to this configuration is not possible. If necessary, the OADM must be replaced, which means that the operation of the entire system, including the main fiber, must be interrupted. This is often not technically and economically feasible or at least only with disproportionate effort, especially in the case of submarine fiber optic cables.
ROADM
A ROADM (where "R" r is ekonfigurierbarer) allowed, however, also to alter the configuration by electronic remote control even after the installation and by pass so more wavelengths of the main fiber to the secondary fiber (and vice versa), or such a passage between main and secondary fiber again cancel.