Dense Wavelength Division Multiplexing (dwdm,wdm,Dense wavelength division multiplexer) refers originally to optical signals multiplexed within the
1550 nm band so as to leverage the capabilities (and cost) of erbium doped fiber amplifiers (EDFAs)， which are effective for wavelengths between approximately 1525- 1565 nm (C band), or 1570 -1610 nm (L band).
