Dense wavelength division multiplexing
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Dense wavelength division multiplexing (DWDM) is a fiber-optic
transmission technique that employs light wavelengths to transmit data
parallel-by-bit or serial-by-character.
The role of scalable DWDM systems in enabling service providers to
accommodate consumer demand for ever-increasing amounts of
bandwidth is important. DWDM is discussed as a crucial component of
optical networks that allows the transmission of e-mail, video,
multimedia, data, and voice—carried in Internet protocol (IP),
asynchronous transfer mode (ATM), and synchronous optical
network/synchronous digital hierarchy (SONET/SDH), respectively,
over the optical layer.
Fundamentals of DWDM Technology
The emergence of DWDM is one of the most recent and important
phenomena in the development of fiber optic transmission technology.
The functions and components of a DWDM system, including the
enabling technologies, and a description of the operation of a DWDM
system are discussed below.
Development of DWDM Technology
Early WDM began in the late 1980s using the two widely spaced
wavelengths in the 1310 nm and 1550 nm (or 850 nm and 1310 nm)
regions, sometimes called wideband WDM. Figure below shows an
example of this simple form of WDM. One of the fiber pair is used to
transmit and the other is used to receive. This is the most efficient
arrangement and the one most found in DWDM systems.
The Challenges of Today's Telecommunications
To understand the importance of DWDM and optical networking, these
capabilities must be discussed in the context of the challenges faced by
the telecommunications industry, and, in particular, service providers.
Forecasts of the amount of bandwidth capacity needed for networks
were calculated on the presumption that a given individual would only
use network bandwidth six minutes of each hour. These formulas did
not factor in the amount of traffic generated by Internet access (300
percent growth per year), faxes, multiple phone lines, modems,
teleconferencing, and data and video transmission. Had these factors
been included, a far different estimate would have emerged. In fact,
today many people use the bandwidth equivalent of 180 minutes or
more each hour.