WDM divides the fiber into channels with different wavelengths, allowing multiple signals to be transmitted simultaneously. There are three main types of WDM: WDM, CWDM, and DWDM, all of which increase the capacity of the fiber. 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.