• 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.e., colors) of laser light.
• This technique enables bidirectional communications over one strand of fiber, as well as multiplication of capacity.
• The term wavelength-division multiplexing is commonly applied to an optical carrier (which is typically described by its wavelength), whereas frequency-division multiplexing typically applies to a radio carrier (which is more often described by frequency). Since wavelength and frequency are tied together through a simple directly inverse relationship, in which the product of frequency and wavelength equals c (the propagation speed of light), the two terms actually describe the same concept.

ADVANTAGES OF DWDM

1. The DWDM point-to-point architecture is simple to build and troubleshoot .
2. It enables protocol transparency, increme-ntal growth, and capacity expansion over time, while dramatically reducing start-up costs.
3. Point-to-point solutions are also extremely efficient.
4. No amplifiers or additional equipment required.