Wavelength Division Multiplexing (WDM) is the process of using different colors of light to transmit multiple data streams through fiber optic cable. Since the different colors of light have differing wavelengths, they do not interfere with each other. Passive optics, such as couplers and prisms can be used to combine the different optical paths and to split them appart. This can drastically increae the bandwidth capibility of the fiber, as each WDM channel acts like its own seperate fiber.