What Does Wavelength Division Multiplexing (WDM) Mean?
Wavelength division multiplexing (WDM) is a technology or technique modulating numerous data streams, i.e. optical carrier signals of varying wavelengths (colors) of laser light, onto a single optical fiber. WDM enables bi-directional communication as well as multiplication of signal capacity.
Techopedia Explains Wavelength Division Multiplexing (WDM)
Wavelength division multiplexing systems can combine signals with multiplexing and split them apart with a demultiplexer. And with the proper fiber cable, the two can be done simultaneously; moreover, these two devices can also function as an add/drop multiplexer (ADM), i.e. simultaneously adding light beams while dropping other light beams and rerouting them to other destinations and devices. Formerly, such filtering of light beams was done with etalons, devices called Fabry–Pérot interferometers using thin-film-coated optical glass. The first WDM technology was conceptualized in the early 1970s and realized in the laboratory in the late 1970s; but these only combined two signals, and many years later were still very expensive.
