What is WDM channel isolation?

WDM is divided into DWDM (dense wavelength division multiplexing, a single-core fiber can simultaneously transmit N channels, channel spacing of 0.8nm and 0.4nm. Each channel can carry an SDH system, the largest commercial system in the country is 160 waves * 10G, 80 waves * 40G system has begun to test commercial) and CWDM (sparse wavelength division multiplexing, a single-core fiber can simultaneously transmit N channels, channel spacing of 20nm, the general system can be on more than 20 channels, mainly used to carry metro network GE services. CWDM (sparse wavelength division multiplexing, a single-core fiber can simultaneously transmit N channels, the channel spacing is 20nm, the general system can be on more than 20 channels, mainly used to carry the GE services of the metro network).

WDM channel isolation is a simple way of examining the extent to which a channel signal in a splitter interferes with another channel.

For example, the splitter D40 of Huawei's Optix 1600G equipment is a 40-channel splitter with one in port and 40 out ports. The light from the main optical path contains 40 channels of signals, which are input from the in port, and then output from out1~out40 according to different wavelengths. Theoretically, the light of the first channel is strictly output from out1, and the light of the second channel is strictly output from out2, and so on. The actual situation is not entirely so, the first wave will also have a very small amount of light from the out2 output, the second channel of the signal on the interference. Channel isolation looks at how much of this interference there is.

For example, if the optical power of the first channel from the in port is -5dBm, and the output from out1 is -10dBm, then -5dBm-(-10dBm)=5dB, and this 5dB is the insertion loss of the first channel. The output from out2 is -40dBm, then -5dBm-(-40dBm)=35dB, this 35dB is the channel isolation of the second channel to the first channel.

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