Today Dense Wavelength Division Multiplexing (DWDM) is one of the most frequently applied fiber-optic transmission technologies to build core telecom networks. DWDM is an optical multiplexing system, wherein data-signals from varied sources are put together, with each signal being transmitted on a separate light wavelength. More than 80 separate wavelengths, each about 0.8 of a nanometre-wide, can share a single optical fiber.