Wavelength Division Multiplexer - a passive Fiber optical device used to separate signals of different wavelengths carried on one fiber.
WDM is the common abbreviation for Wavelength division multiplexing. WDM uses multiple lasers and transmits multiple wavelengths of Light over a single optical fiber.
WDM has increased the carrying capacity of fiber optic Cables and also made it possible for Data to flow both ways in a single strand of fiber. By adjusting the data streams into a different part of the light Spectrum several types of data are able to travel on its own unique color band.