In the whole WDM system, the optical wavelength division multiplexer and the demultiplexer are the key components in the WDM technology, and their performance plays a decisive role in the transmission quality of the system.

Advantages of WDM wavelength division multiplexing
High capacity
An important feature of WDM is that it can make full use of the bandwidth resources of optical fibers to increase the data transmission capacity without changing the basic structure of the existing network, so that the transmission capacity of an optical fiber is many times higher than that of a single wavelength. For example, the DWDM system can support up to 192 wavelengths in a pair of fibers, and the transmission capacity of each wavelength is as high as 100Gbit/s ~ about 400Gbit/s and one Terabit/s.

Good compatibility
WDM has good compatibility with different signals. When transmitting signals of different natures such as image, data and voice in the same optical fiber, each wavelength is independent of each other and does not interfere with each other, ensuring the transparency of transmission.

High network flexibility, economy and reliability
Wavelength division multiplexing makes upgrades easier by allowing new channels to be connected as needed without disrupting the service of existing traffic. When the network is upgraded and expanded, there is no need to transform the optical cable line, and new industries can be opened or superimposed by adding wavelengths, saving a lot of optical fibers and 3R regenerators in large-capacity long-distance transmission, and the transmission cost is significantly reduced.

Wavelength routing
WDM technology is one of the key technologies to realize all-optical network. In the all-optical network that is expected to be realized in the future, by changing and adjusting the wavelength of the optical signal on the optical path, the add/drop and cross-connection of various telecommunication services can be realized.

What is Mux and Demux?
Multiplexer MUX
The main function of the multiplexer MUX is to combine multiple signal wavelengths in one optical fiber for transmission. At the sending end, N optical transmitters work on N different wavelengths respectively, and the N wavelengths are separated by appropriate intervals, which are respectively denoted as λ1, λ2...λn. The N light waves are respectively modulated by the signal as the carrier wave to carry the signal. A combiner combines these optical carrier signals of different wavelengths and couples them into a single-mode fiber. Since the optical carrier signals of different wavelengths can be regarded as independent of each other (without considering the nonlinearity of the optical fiber), multiplexing and transmission of multiple optical signals can be realized in one optical fiber. Through multiplexing, communication operators can avoid maintaining multiple lines, effectively saving operating costs.

Demultiplexer DEMUX
The main function of the demultiplexer Dwdm mux demux is to separate multiple wavelength signals transmitted in an optical fiber. In the receiving part, the optical carrier signals of different wavelengths are separated by a demultiplexer, and further processed by the optical receiver to restore the original signal. A multiplexer (Demux) is a device that reverses a multiplexer.

In principle, the device is reciprocal (bidirectionally reversible), that is, as long as the output and input of the demultiplexer are used in reverse, it is a multiplexer.