wavelengthdivision

Wavelength division multiplexing (WDM) is a method in fiber-optic communications that carries multiple optical carrier signals on a single optical fiber by using different wavelengths of light. Each wavelength represents a separate data stream, allowing the aggregate data rate of the link to be increased without laying more fiber.

In a typical WDM system, transmitters generate light at distinct wavelengths, which are combined by a multiplexer onto one fiber. At the remote end, a demultiplexer separates the wavelengths for detection by individual receivers. Along the way, optical amplifiers and dispersion management may be used to extend reach and preserve signal quality. WDM systems often employ wavelength-selective components such as filters, Bragg gratings, and wavelength-selective switches to direct channels.

Variants include coarse WDM (CWDM) and dense WDM (DWDM). CWDM uses wider channel spacing (on the order of tens of nanometers) and fewer channels, making it simpler and cheaper for metro networks. DWDM uses closely spaced channels (tens of gigahertz to hundred gigahertz), enabling many channels on a single fiber and is widely used for long-haul and backbone networks. DWDM systems often rely on erbium-doped fiber amplifiers, optical add-drop multiplexers (OADMs), and precise laser sources.

Applications of WDM include digital communication networks, data-center interconnects, submarine cables, and other deployments seeking higher capacity without laying additional fibers. Challenges include chromatic dispersion, nonlinear effects in the fiber, channel crosstalk, and the need for stable and well-managed wavelength control.