All about DWDM (Dense Wavelength Division Multiplexing)
Information network technology developers continually strive to enhance the throughput and quality of the network data lines, while also reducing the cost-per-bit (CPB) of the networks. One such technology is, Dense Wavelength Division Multiplexing (DWDM). DWDM is a method of creating several virtual fiber optic lines, which effectively multiplies the capacity of the physical fiber optic line. Wavelength division multiplexing (WDM) uses optical multiplexing that results in increasing bandwidth over existing fiber optic cabling without needing to add additional cabling. Optical multiplexing involves combining several transmitted and received signals of different wavelengths simultaneously. The term “dense” in DWDM implies that the new method of WDM uses more densely packed frequency channels than previous “coarse” WDM (CWDM) technology.
Optical transponders with DWDM capability are needed to deploy DWDM technology, though previously installed fiber optic cabling may be reused. This often results in a much lower cost per bit for data traffic, as new cable may not be required to substantially increase the bandwidth of a fiber optic network. The latest DWDM technologies support a maximum of 192 frequencies (wavelengths) on a single pair of fiber optic lines, and with proper optical transceivers, each DWDM frequency can support a maximum of 100 gigabits per second (Gbit/s or Gbps), which future potential for ever greater throughput per pair.
Each DWDM unit requires a multiplexer and transmitter on one side of the fiber and a demultiplexer and receiver on the other side of the fiber. This makes DWDM more complex and requires the use of wideband optical amplifiers, such as erbium doped fiber amplifiers (EDFAs), as opposed to narrow band optical amplifiers. Otherwise, several optical amplifiers would be needed to amplify each DWDM wavelength. This would be increasingly expensive considering that every 100 kilometers of fiber optic cable typically requires an intermediate line repeater (amplifier) to compensate for the loss of signal strength over long runs of optical fiber. Given the density of signals, DWDM is also somewhat more sensitive to fiber quality than CWDM.
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