Dense wavelength division multiplexing (DWDM) is a technology that puts data from different sources together on an optical fiber, with each signal carried at the same time on its own separate light wavelength. Using DWDM, up to 80 (and theoretically more) separate wavelengths or channels of data can be multiplexed into a lightstream transmitted on a single optical fiber.
Each channel carries a wave division multiplexed (WDM) signal. WDM is a method of combining multiple signals on laser beams at various infared (IR) wavelengths for transmission along fiber optic media. In a system with each channel carrying 2.5 Gbps (billion bits per second), up to 200 billion bits can be delivered a second by the optical fiber.
Since each channel is demultiplexed at the end of the transmission back into the original source, different data formats being transmitted at different data rates can be transmitted together. Specifically, Internet (IP) data, Synchronous Optical Network data (SONET), and asynchronous transfer mode (ATM) data can all be travelling at the same time within the optical fiber.
DWDM promises to solve the fiber exhaust problem and is expected to be the central technology in the all-optical networks of the future.
Coarse wavelength division multiplexing (CWDM) is an alternative method of combining multiple signals on laser beams at various wavelengths for transmission along fiber optic cables, such that the number of channels is fewer than in DWDM but more than in standard WDM.