Principle: Uses wider wavelength spacing (20 nm, e., 1470–1610 nm), supporting 18 channels with 2. Applications: Short-haul (50–80 km) metro networks and campus links. 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 chapter addresses the operating principles of WDM. Wavelength division multiplexers are fundamental to the functioning and performance of integrated photonic circuits, with applications ranging from optical interconnects to sensing and quantum technologies. Each wavelength, or “channel,” carries an independent data stream, allowing bandwidths up to 400. ptical multiplexing techniques, wavelength division multiplexing (WDM).