Wavelength division multiplexing (WDM), including CWDM (coarse wavelength division multiplexing) and DWDM (dense wavelength division multiplexing), etc. It refers to the coupling of multiple signals of different wavelengths on a single fiber for simultaneous transmission.
What is the difference between CWDM and DWDM?
1. Different wavelength intervals
CWDM: wavelength interval ≥20nm, total 18 bands of 1270nm~1610nm with 20nm interval,
DWDM: wavelength interval <10nm, usually using 1528nm~1565nm band with wavelength interval of 200GHz (1.6nm), 100GHz (0.8nm) or 50GHz (0.4nm)
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2. Modulated lasers are different
In general, CWDM modulated lasers use uncooled lasers, while DWDM uses cooled lasers. The cooled laser uses temperature tuning, and the uncooled laser uses electronic tuning.
Conlusion, WDM has multiplexer and de-multiplexer. The multiplexer (MUX) combines multiple signal wavelengths in a single fiber for transmission at the transmitter side; the de-multiplexer (DEMUX) separates multiple wavelength signals transmitted in a single fiber at the receiver side. The main purpose of WDM is to increase the available bandwidth of the fiber, which can be expanded by WDM without the need to lay more fibers.
