Wavelength Division Multiplexing(WDM)
It is the same as FDM but applied to fibers, only the difference is that here the operating frequencies are much higher actually they are in the optical range. There’s great potential for fibers since the bandwidth is so huge. Fibers with different energy bands are passed through a diffraction grating prism. Combined on the long-distance link and then split at the destination. It has got high reliability and very high capacity.
It multiplexes multiple data streams onto a single fiber optic line. Different wavelength lasers(called lambdas) transmit multiple signals. Each signal carried on the fiber can be transmitted at a different rate from the other signals.
- Dense wavelength division multiplexing: It combines many (30, 40, 50, or more) channels onto one fiber. DWDM channels have a very high capacity and it keeps on improving.
- Coarse wavelength division multiplexing: It combines only a few lambdas. In this, channels are more widely spaced and are a cheaper version of DWDM.
Multiplexing (Channel Sharing) in Computer Network
Multiplexing means multiple sources but one link. An alternative approach is a Direct point-to-point connection, but it has several problems as it requires an I/O port for each device, a need line for each device, and also a large amount of wiring needed if on different floors. Instead, if we use a multiplexer approach then all devices are connected to MUX and one line to the host, the link carries multiple channels of information and several lines equal to the number of lines out.