Mumbai University > Electronics and telecommunication > Sem 7 > optical communication and networks

Marks: 08

Years: DEC 2015

• Optical filters are essential components in transmission systems for at least two applications: to multiplex and demultiplex wavelengths in a WDM system—these devices are called multiplexers/ demultiplexers—and to provide equalization of the gain and filtering of noise in optical amplifiers.

• A simple filter is a two-port device that selects one wavelength and rejects all others. It may have an additional third port on which the rejected wavelengths can be obtained.

• Multiplexer combines signals at different wavelengths on its input ports onto a common output port, and a demultiplexer performs the opposite function. Multiplexers and demultiplexers are used in WDM terminals as well as in larger wavelength crossconnects and wavelength add/drop multiplexers.

In Fig 4.6 (a) A simple filter, which selects one wavelength and either blocks the remaining wavelengths or makes them available on a third port.

(b) A multiplexer, which combines multiple wavelengths into a single fiber. In the reverse direction, the same device acts as a demultiplexer to separate the different wavelengths.