DWDM stands for Dense Wavelength Division Multiplexing. It is a technology used in optical fiber communication networks to increase the capacity of data transmission over long distances. In DWDM, multiple signals are transmitted simultaneously over a single fiber optic cable by using different wavelengths of light. Each signal is assigned a specific wavelength, and these signals are combined into a single beam of light that is transmitted through the fiber optic cable. At the receiving end, the signals are separated back into their individual wavelengths using a demultiplexer. DWDM allows for the efficient use of available bandwidth in optical fibers and enables the transmission of large amounts of data over long distances at high speeds. It is widely used in telecommunications networks, including internet backbone networks, to meet the increasing demand for high-speed data transmission.