Dense WDM (DWDM) uses the C-Band (1530 nm-1565 nm) transmission window but with denser channel spacing. Channel plans vary, but a typical DWDM system would use 40 channels at 100 GHz spacing or 80 channels with 50 GHz spacing. In fiber-optic communications, wavelength-division multiplexing (WDM) is a technology which multiplexes a number of optical carrier signals onto a single optical fiber by using different wavelengths (i. Typically composed of several wavelength selectors, it uses optical components like gratings or fiber Bragg gratings to arrange different wavelengths in a predefined sequence, creating a multi-wavelength optical. Dense wavelength division multiplexing (DWDM) is a fiber optic technology that sends dozens of separate data signals through a single strand of glass simultaneously, each carried on its own unique wavelength of light. This chapter addresses the operating principles of WDM.