Reconfigurable optical add-drop multiplexer
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A reconfigurable optical add-drop multiplexer (ROADM) is a form of optical add-drop multiplexer that adds the ability to remotely switch traffic from a WDM system at the wavelength layer. This allows individual wavelengths carrying data channels to be added and dropped from a transport fiber without the need to convert the signals on all of the WDM channels to electronic signals and back again to optical signals.
The main advantages of the ROADM are:
- The planning of entire bandwidth assignment need not be carried out during initial deployment of a system. The configuration can be done as and when required.
- ROADM allows for remote configuration and reconfiguration.
- In ROADM, as it is not clear beforehand where a signal can be potentially routed, there is a necessity of power balancing of these signals. ROADMs allow for automatic power balancing.
ROADM functionality originally appeared in long-haul DWDM equipment, but by 2005, it began to appear in metro optical systems because of the need to build out major metropolitan networks in order to deal with the traffic driven by the increasing demand for packet-based services.
The switching or reconfiguration functions of a ROADM can be achieved using a variety of switching technologies including MEMS, Liquid crystal, thermo optic and beam-steering switches in planar waveguide circuits, and tunable optical filter technology.
