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FDM TDM WDM

Time:2020-01-03 Views:480
Difference of FDM TDM WDM:

FDM is Frequency division multiplexing, a multiplexing technology in which the carrier bandwidth is divided into several subchannels with different frequency bands. Each subchannel can transmit one channel of signals in parallel. FDM is often used in analog transmission broadband networks. In a communication system, the bandwidth that a channel can provide is usually much wider than that needed to transmit a signal. If a channel transmits only one signal, it is very wasteful. In order to make full use of the bandwidth of the channel, the method of frequency division multiplexing can be used. In the frequency division multiplexing system, the available frequency bands of the channel are divided into several non overlapping frequency bands. Each signal is transmitted in one of the frequency bands, so they can be filtered out by a filter, and then demodulated and received separately.

TDM is Time division multiplexing, a technology that transmits multiple digital data, voice and video signals on the same communication medium at the same time through cross bit pulses in different channels or time slots. The basic channel bandwidth used in telecommunication is DS0, and its channel width is 64 Kbps.

WDM is Wavelength division multiplexing, a technology that combines two or more different wavelengths of optical carrier signals (carrying various kinds of information) at the sending end through multiplexers (also known as combiners, multiplexers) and couples them to the same optical fiber of the optical line for transmission; at the receiving end, the optical carriers of various wavelengths are separated by demultiplexers (also known as demultiplexers, or demultiplexers), and then the The optical receiver performs further processing to recover the original signal. This technology of transmitting two or more optical signals of different wavelengths in the same optical fiber is called wavelength division multiplexing. WDM is essentially FDM technology in optical domain. Each wavelength path is realized by frequency domain segmentation, and each wavelength path occupies a section of fiber bandwidth. WDM system adopts different wavelengths, i.e. specific standard wavelengths. In order to be different from the ordinary wavelengths of SDH system, it is sometimes called color optical interface, and the optical interface of ordinary optical system is called "white optical interface" or "white optical interface".
The design of communication system is different, and the interval width between each wavelength is also different. According to the different channel spacing, WDM can be divided into CWDM (coarse wavelength division multiplexing) and DWDM (dense wavelength division multiplexing). The channel interval of CWDM is 20nm, while that of DWDM is from 0.2nm to 1.2nm, so compared with DWDM, CWDM is called coarse WDM.