Dense Wave Division Multiplexing (DWDM)

Dense Wavelength Division Multiplexing (DWDM) systems provide capacity relief to fiber optic systems by combining multiple wavelengths on a fiber. DWDM systems are high capacity systems as compared to Coarse Wave Division Multiplexing (CWDM) systems and can have 40 or more wavelengths. Transponders are used to convert signals to specific DWDM wavelengths between 1530 nm and 1565 nm. They can also convert from multi-mode to single-mode and from copper to fiber. DWDM filters combine the converted wavelengths onto the fiber optic link for transport. DWDM systems can use optical fiber amplifiers (OFAs) to boost the signal strength and increase the distance all the wavelengths can be transported. Dispersion Compensation Modules (DCMs) can be used along with OFAs to counter the effects of chromatic dispersion on long fiber optic spans. All these elements can be remotely inventoried and managed in a Network Management System (NMS) as depicted in the figure below.

DWDM system can also use Reconfigurable Optical Add/Drop Multiplexers (ROADMs) to remotely add and drop wavelengths to a system. ROADMs are often combined with Optical Channel Monitors (OCMs) to remotely balance power on both new and in-service wavelengthswhenever the network is reconfigured. This is controlled remotely through the Network Management System (NMS). The combination of a ROADM and OCM gives service providers a powerful tool to add or drop capacity without having to dispatch technicians to a remote site or central office.