WDM(Wavelength Division Multiplexing) is a technology that combines two or more optical carrier signals of different wavelengths (carrying various information) at the transmitter with multiplexers (also known as multiplexers) and coupling them to the same optical fiber for transmission. At the receiving end, the optical carriers of various wavelengths are separated by a Demultiplexer, which is then further processed by the optical receiver to recover the original signal. The technique of transmitting two or more different wavelengths of light simultaneously in the same optical fiber is called wavelength division multiplexing.
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WDM technology has many advantages and has been developed rapidly. The transmission capacity of a single optical fiber is increased than that of a single wavelength transmission by utilizing the bandwidth resources of the optical fiber .
Add several times to dozens times; Multiwavelength multiplexing in single-mode fiber transmission, in large capacity long-distance transmission can save a lot of fiber; For the cables installed in the early stage, the number of cores is small, and WDM can be used to expand the capacity without major changes to the original system. Since the signal wavelength transmitted in the same optical fiber is independent from each other, it can transmit signals with completely different characteristics, and complete the synthesis and separation of all kinds of telecommunication service signals, including digital signals and analog signals, as well as the synthesis and separation of PDH signals and SDH signals. WDM channel is transparent to data format, that is, independent of signal rate and electrical modulation mode.
A WDM system can carry "service" signals in a variety of formats, such as ATM, IP, etc. In network expansion and development, it is an ideal means of capacity expansion, and also an advantageous means of introducing new broadband services (such as CATV, HDTV and b-isdn). Adding an additional wavelength can introduce any new services or capacity you want. By using WDM technology to realize network switching and recovery, it is possible to realize transparent optical network with high survivability in the future. The application of EDFA in national backbone transmission can reduce the number of SDH Repeaters in long-distance trunk line systems, thereby reducing costs.