Wavelength Division Multiplexing (WDM) is a technology to combine two or more optical carrier signals with different wavelengths that carry various information at the transmitting end through a multiplexer, and couple them to the same fiber in the optical path for transmission. At the receiving end, the optical carriers of various wavelengths are separated by the demultiplexer, and then further processed by the optical receiver to restore the original signal. This technique of simultaneously transmitting two or more optical signals of different wavelengths in the same fiber is called wavelength division multiplexing.
WDM is essentially a frequency division multiplexing FDM technology in the optical domain. Each wavelength channel is realized by division in the frequency domain, and each wavelength channel occupies the broadband of a section of optical fiber. The wavelengths used by WDM systems are all different, that is, specific standard wavelengths. The design of the communication system is different, and the spacing width between each wavelength is also different. According to the different channel spacing, WDM can be subdivided into CWDM coarse wavelength division multiplexing and DWDM dense wavelength division multiplexing. The channel spacing of CWDM is 20nm, while the channel spacing of DWDM is from 0.2nm to 1.2nm, so compared with DWDM, CWDM is called coarse wavelength division multiplexing technology.
Prospects of WDM
WDM is a multiplexing technology in the optical domain to form an all-optical network. It is a future trend to establish an optical network layer based on WDM and OXC optical cross-connection, realize end-to-end all-optical network connection for users, and use a pure all-optical network to eliminate the bottleneck of photoelectric conversion. The WDM technology is still based on the point-to-point method, but the point-to-point WDM technology is the first and most important step in all-optical network communication.
WDM Applications
WDM can greatly increase the capacity of existing fiber-optic infrastructures of telephone companies and other operators. Manufacturers have introduced the DWDM dense wavelength division multiplexing system. DWDM can support the simultaneous transmission of more than 150 light waves of different wavelengths, and each light wave can reach a data transmission rate of up to 10Gb/s. Such a system can provide data transfer rates in excess of 1Tb/s on a single fiber optic cable.
DWDM can combine and transmit different wavelengths simultaneously in one fiber. For validity, one fiber is converted into multiple virtual fibers. Therefore, if you plan to multiplex 8 optical fiber carriers (OC), that is, to transmit 8 signals in one optical fiber, the transmission capacity will be increased from 2.5 Gb/s to 20 Gb/s. Due to the use of DWDM technology, a single fiber Fiber can transmit data traffic up to 40Gb/s. As manufacturers add more channels to each fiber, terabits per second transmission speeds are just around the corner.
WDM Features
1. Ultra-large capacity transmission
2. Save fiber resources
3. Transparent transmission of each channel, smooth upgrade and capacity expansion
4. Using EDFA to realize ultra-long distance transmission
5. Improve system reliability
6. Can form an all-optical network
