DWDM can multiplex,demultiplex or add and drop multiplex different optical signals, which can effectively save optical fiber and networking costs. Compared with CWDM, DWDM greatly increases the number of working wavelengths, thereby greatly increasing the signal transmission speed and communication capacity. DWDM has 100GHz, 200GHz and other channel intervals, suitable large capacity long-distance trunk network or super large capacity MAN core node. It is widely used in Telecom 5G, MAN and BN.