WDM is to combine a series of information-bearing optical signals with different wavelengths into a bundle and transmit them along a single fiber;
A communication technology in which optical signals of different wavelengths are separated by a certain method at the receiving end. This technology can transmit multiple signals on one fiber at the same time, and each signal is transmitted by a certain wavelength of light, which is a wavelength channel.
However, wavelength division can transmit a very large amount of data in an optical fiber by carrying data on multiple wavelengths and combining them. Therefore, it can be known that the application scenario of WDM mainly lies in the occasion of large-capacity data transmission. For example, the operator‘s national intercity trunk line/intra-city backbone, the interconnection of some enterprise data centers.
Optical wavelength division multiplexing generally uses wavelength division multiplexers and demultiplexers (also called multiplexers/demultiplexers), which are placed at both ends of the fiber to realize the coupling and separation of different light waves. The principle of the two devices is the same
wavelength division multiplexer
The main types of optical wavelength division multiplexers are fused taper type, dielectric film type, grating type and flat type.
Performance
Its main characteristic indicators are insertion loss and isolation
Since the wavelength division multiplexing equipment is used in the optical link, the increase of the optical link loss is called the insertion loss of the wavelength division multiplexing. When the wavelengths λ1 and λ2 are transmitted through the same fiber, the difference between the power at the input end λ2 of the demultiplexer and the power mixed in the fiber at the output end of λ1 is called isolation.
Optical wavelength division multiplexer features and advantages
Make full use of the low-loss band of the optical fiber, increase the transmission capacity of the optical fiber, and double to several times the physical limit of the information transmitted by one optical fiber. At present, we only use a very small part of the low-loss spectrum of optical fiber (1310nm-1550nm). WDM can make full use of the huge bandwidth of single-mode fiber about 25THz, and the transmission bandwidth is sufficient.
It has the ability to transmit two or more asynchronous signals in the same fiber, which is beneficial to the compatibility of digital signals and analog signals. It has nothing to do with data rate and modulation mode, and can flexibly take out or add channels in the middle of the line.
For the existing optical fiber system, especially the optical cable with a small number of cores laid in the early stage, as long as the original system has a power margin, the capacity can be further increased to realize the transmission of multiple one-way signals or two-way signals without making major changes to the original system. Has strong flexibility.
Due to a large reduction in the use of optical fibers, the construction cost is greatly reduced, and due to the small number of optical fibers, when a fault occurs, it is also quick and convenient to restore.
The sharing of active optical equipment, the transmission of multiple signals or the addition of new services reduces costs.
The active devices in the system are greatly reduced, thus improving the reliability of the system
