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An add/drop multiplexer (ADM) is a critical element of an optical fiber network. It can combine (i.e. multiplex) several low-bandwidth streams of data into a single light beam; and simultaneously, it can drop or remove other low-bandwidth signals from the stream of data and direct them to other network routes. The filtering technology used with ADM is called Fabry-Pérot etalon.
Add/drop multiplexers are also known as optical add/drop multiplexers.
Thank of an ADM as an on-ramp/off-ramp to a high-speed optical fiber network.
Add/drop multiplexers can be used for both expensive long-haul core networks and shorter distance networks, called metro networks. The expense in long-haul core networks comes from adapting (i.e. scaling) the technology to the high-speed data rates and the dense wavelength division multiplexing (DWDM), i.e. a technology allowing a number of carrier signals of different wavelengths (or colors) of laser light to be carried on a single optical fiber.
Recent changes in ADM technology, called multi-service provisioning platform (MSPP), is composed of equipment with legacy ADM equipment capabilities but with cross-functionality, allowing direct connections from local area networks (LANs) to an ISPs (Internet Service Providers) or other service provider’s optical fiber backbone.
Many carriers are investing in metro optical networks with an ever increasing variety of ADMs. Many of these are reconfigurable optical add-drop multiplexers (ROADMs) capable of remotely switching data traffic from a wave-length division multiplexing (WDM) system at the wavelength layer, i.e. switching based on wavelength.