can be notably increased by adding WDM devices and possibly amplifiers. On the other hand, a radio (or wireless)-based network can be re-sited fairly easily. This is much more difficult to do with the optical fiber alternative. If the metro area is large, say > 100-km circumference, LOS microwave may be a consideration. Once installed, it would be costly to resite. If the circumference is small (e.g., <100 km), one of the IEEE 802 wireless LAN standards may want to be considered. In this discussion three IEEE 802 Committee standards will be briefly outlined: IEEE 802.11 IEEE 802.15 IEEE 802.16 13.3 FIBER-OPTIC RING NETWORK Typically, a fiber-optic ring network is created when a fiber-optic cable connects the several nodes around the ring. We assume at the outset that each node connected to the Fundamentals of Telecommunications, Second Edition, by Roger L. Freeman ISBN 0-471-71045-8 Copyright © 2005 by Roger L. Freeman METROPOLITAN AREA NETWORKS MAN serves an add-drop function placing traffic into the MAN and taking traffic from the node in its "drop" function. For added protection against vandalism, the fiber-optic cable in question is buried. Several dark fibers are placed along with the active fibers to serve an expansion capability for future growth. The ring formation of the fiber-optic MAN is based on one of several possible ANSI/Telcordia standards under the umbrella term "automatic protection switching" (Refs. 3, 4). These techniques can improve availability by a factor of 100 or better. Fiber offers two approaches for future growth: (1) Add spare dark fibers to handle growth and/or (2) use WDM techniques particularly in the 1550-nm band when the user needs additional capacity. A fiber-optic MAN is much less versatile if assets have to be moved or topology changed when compared to its IEEE 802.11 radio-wireless counterpart. Once the maximum bit rate of a single thread is reached for an IEEE 802.11 system, we can expand no further unless a new access point is added. 13.4 IEEE 802.11 SYSTEM The IEEE 802.1 s