ITU-T Defined the DWDM Wavelength, in ITU-T G.694.1, <Spectral Grids for WDM Applications: DWDM Frequency Grid >, the Latest Version Is V3.0 Approved on Oct. 2020.

50GHz Spacing DWDM, Applied in N×10Gb/S DWDM Transmission System, Which Is Still Deployed in Some Enterprise Network and Special Network.

75GHz Spacing DWDM, Applied in N×400Gb/S DWDM Transmission System.

100GHz Spacing DWDM, Applied in N×10Gb/S, N×25Gb/S, and N×100Gb/S DWDM Transmission System, Widely Used In Today Mainstream Network.

112.5GHz Spacing DWDM, Applied in N×800Gb/S DWDM Transmission System.

For System and Active Engineer, They Usually Say Frequency. For Optical Engineer and Passive Industry, Central Wavelength Is Talked More. With This Table, You Can Find All the Information You Will Meet.