Introduction To Dense Wave Division Multiplexing (DWDM)

This paper covers the how the need for Wave Division Multiplexing (WDM) and Dense WDM became essential and the basic difference between WDM and DWDM. Alternatives to DWDM are explored including Time Division Multiplexing (TDM) and Optical TDM (OTDM). An example of the difference between TDM and WDM is shown in a detailed example. The major components of a WDM system are explored. A few vendor products providing DWDM, the major features of each product, and the product capacities are compared. This paper concludes with some potential deficiencies of a DWDM system.

The first generation optical networks, circa 1960, used single wavelength transmission and electrical-based switches for routing and processing. By using electrical switches, the optical signal must be converted to an equivalent electrical signal, processed by the electrical-based switches, and converted back to an optical signal. This significantly slowed down the otherwise optical network, as the transmission along a particular logical path is as fast as the slowest link.

If you think of a road between two points, imagine the road surface is

nals. Fixed conversion wavelength converters are effective when there are few input wavelengths and few output wavelengths. They are not suitable to large DWDM networks that may process any useable wavelength. Wavelength converter categories can be combined within one converter. For example, a particular converter may interface between an optical network transmitting at 1310 nm and convert the signal to any wavelength within the C-band range.

OTDM and WDM are the foundation of second generation optical networks. Since OTDM and WDM can be used within the same network, they are complementary technologies in that a single fiber strand can be transmitting a several WDM signals, and each single WDM wavelength can contain OTDM multiplexed data. Using WDM and OTDM together is called an All Optical Network (AON). AON increase the efficiency and throughput while decreasing delay and errors. DWDM takes WDM, one of the second-generation optical network technologies, and takes it further.

Some topics in this essay:
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