Different optical wavelengths, also referred to as lambdas, of light are multiplexed in some optical modules using wavelength-division multiplexing (WDM). Variants include Coarse WDM (CWDM), Dense WDM (DWDM).OverviewAn optical module is a typically hot-pluggable optical transceiver used in high-bandwidth data communications applications. Optical modules typically have an electrical interface on the side that connects t. There have been multiple variants of the electrical interface of optical modules that have been used over the years. The earliest forms of optical modules had an analog electrical interface. In the transmit dir. Many different forms of optical modulation and multiplexing have been employed in optical modules. The most common modulation technique historically has been or NRZ.