Express port (EXP) It is possible to combine CWDM and DWDM, since DWDM sits in the top half (red band) of the CWDM grid. Usually when doing so, the DWDM module is connected to the upgrade port of the lower-band (blue) CWDM module. The result is that all nine channels of the red CWDM band are occupied, although DWDM actually only uses four of the CWDM wavelengths. The express port is a special upgrade port for the red- band CWDM module. It only passes the wavelengths that are required for DWDM, making the remaining five CWDM channels available. Standard setup With a standard upgrade port, the DWDM module can only be connected to a blue CWDM module. The wave- lengths of the red band can therefore not be used. Blue-band channels Blue CWDM module COM UG DWDM module COM Blue CWDM module Red CWDM module CWDM 18 channels Wavelengths 1271 1291 1311 1331 1351 1371 1391 1411 1431 1451 1471 1491 1511 1531 1551 1571 1591 1611 DWDM DWDM band Express port setup With the express upgrade port, the CWDM module is connected to the express port of a red CWDM module. This way, five additional wavelengths of the CWDM can be used. Blue-band channels Blue CWDM module Express port The express port cuts the wavelengths out of the CWDM grid which are actually needed for DWDM. Red-band channels Red CWDM module DWDM module COM UG COM EXP COM 9
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