Page 39 - Optical Communications Essentials

Optical Communication Systems Overview

Optical Communication Systems Overview 29

Figure 2.7. (a) Spectral interference
between adjacent wavelength chan-
nels; (b) stable channels.

2.5. Applications of Optical Fiber Links
Optical fibers can be applied to interconnections ranging from localized links
within an equipment rack to links that span continents or oceans. As Fig. 2.8 illus-
trates, networks are traditionally divided into the following three broad categories:
1. Local-area networks (LANs) interconnect users in a localized area such as
a room, a department, a building, an office or factory complex, or a campus.
Here the word campus refers to any group of buildings that are within reason-
able walking distance of one another. For example, it could be the collocated
buildings of a corporation, a large medical facility, or a university complex.
LANs usually are owned, used, and operated by a single organization.
2. Metropolitan-area networks (MANs) span a larger area than LANs. This
could be interconnections between buildings covering several blocks within a
city or could encompass an entire city and the metropolitan area surrounding
it. There is also some means of interconnecting the MAN resources with com-
munication entities located in both LANs and wide-area networks. MANs are
owned and operated by many organizations. When talking about MAN fiber optic
applications, people tend to call them metro applications.
3. Wide-area networks (WANs) span a large geographic area. The links can
range from connections between switching facilities in neighboring cities to
long-haul terrestrial or undersea transmission lines running across a country or
between countries. WANs invariably are owned and operated by many trans-
mission service providers.

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