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. This is often compared to using a fiber as a single-lane road, where each service requires its own path. With WDM, multiple wavelengths travel in parallel, like. This guide gives a top level understanding of Wavelength Division Multiplexing, Coarse Wavelength Division Multiplexing and Dense Wavelength Division Multiplexing. Each wavelength, or “channel,” carries an independent data stream, allowing bandwidths up to 400.