4 nm (100 GHz/50 GHz grid). This small channel spacing allows to transmit simultaneously more information. Currently a restriction on wavelengths between 1530 nm and 1625 nm exists which corresponds to the C and L band. In fiber-optic communications, wavelength-division multiplexing (WDM) is a technology which multiplexes a number of optical carrier signals onto a single optical fiber by using different wavelengths (i. Learn how it works and how DWDM solutions can help supercharge your business's connectivity. What is Dense Wavelength Division Multiplexing (DWDM)? How. This chapter provides an overview of dense wavelength division multiplexing (DWDM) systems.