It describes WDM as a technology that uses the properties of refracted light to combine and separate optical signals based on their wavelengths. Key components of a WDM system include optical multiplexers and demultiplexers, optical amplifiers, and transponder units. The "basie" transmission rate of SONET is 64 kbps for supporting voice communications. It can perform additional roles like providing redundancy, supporting advanced topologies, reducing hardware and cost, etc. The idea is to divide. This chapter provides an overview of dense wavelength division multiplexing (DWDM) systems. The following topics are covered in this chapter: • Time Division Multiplexing Versus Wave Division Multiplexing • Wavelength Division Multiplexing Versus Dense Wavelength Division Multiplexing • Value of.