Add-drop multiplexer (ADM)

An add-drop multiplexer (ADM) is a telecommunications device used to multiplex and route multiple optical signals across a single optical fiber cable. It is widely used in modern telecom networks to increase the capacity of existing cables while minimizing the amount of equipment and space required.

An ADM works by taking multiple input signals, which can be either a single wavelength (λ) of light or a combination of multiple wavelengths (λs). The ADM then combines these inputs into a single stream of optical signals that are transmitted across a single optical fiber. In addition, it can be used to “drop” or add one or more of the wavelengths from the single stream onto the output fibers. This allows for efficient use of existing fiber cables, as the ADM can drop one wavelength from the single stream, and direct it to a specific output fiber, while all other wavelengths continue on the same fiber to their destination.

The ADM is made up of several components including a multiplexer, a demultiplexer, and a power splitter. The multiplexer combines the input signals into a single stream, while the demultiplexer separates the single stream into its individual wavelengths. The power splitter is used to divide the optical power of the single stream between the output fibers.

The ADM is used primarily in long-distance telecommunications networks, where multiple wavelengths are used to increase capacity. By allowing multiple channels of data to be transmitted over a single fiber, the ADM reduces the number of cables and equipment needed, thereby reducing costs and increasing efficiency.

The ADM has become increasingly popular in recent years as telecommunications networks become more complex and require higher data rates. By using an ADM, operators can easily upgrade their networks to support increasing amounts of data traffic without having to install additional cables and equipment.