(1) Short for wavelength division multiplexing, a type of multiplexing developed for use on optical fiber. WDM modulates each of several data streams onto a different part of the light spectrum. WDM is the optical equivalent of FDM.
WDM works by channeling some of the work of the device driver into portions of the code that are integrated into the operating system. These portions of code handle all of the low-level buffer management, including DMA and Plug and Play device enumeration. The WDM device driver becomes more streamlined with less code and works at greater efficiency.
All versions of Microsoft Windows after Windows 95 have implemented WDM. Kernel-mode drivers that follow WDM rules are called WDM drivers.