xWDM Transportation System， x can be CWDM, Or DWDM.
The CWDM wavelength range is 1270-1610 nm and the channel spacing is 20 nm, virtually covering all ranges of DWDM wavelengths, whereas DWDM wavelength channel spacing is much smaller (0.4 nm / 0.8 nm). So CWDM wavelengths near DWDM wavelengths can be used to transmit DWDM wavelength.In most practical applications, CWDM 1530nm and 1550nm channels are used to achieve CWDM & DWDM combined transmission.
CWDM & DWDM combined transmission solution
