In DWDM the OADM is the heart of the system

OADM : optical add drop Multiplexer

OADM can be classified mainly in to :

1- FOADM
2- ROADM
3- TOADM

F : Fixed
R : reconfigurable
T : Tunable

The main difference is in the OADM flexibility

DWDM & RAN

As we know WDM solutions used to provide connectivity and Transport Traffic with high capacity for a long distance

Applications could be data centre , Enterprise , utilities

Also mobile operators use WDM a a Transport method

In Cloud RAN , we could use WDM mux and demux cabinets to link multiple RRUs or RRH to a centralized BBU

RRH : remote radio head which used for power amplification and modulation/ demodulation of Rf signals in RAN

BBU : base band unit which used for Mobile RAN service processing