The promise of metro DWDM solutions has been discussed for some time. However, large-scale deployment of these solutions has been held back by the relative inflexibility and associated costs of these systems [3].

Metro DWDM networks are very fluid in nature—traffic patterns are changeable and diverse. A single metro location will often share traffic with multiple locations within the same metro area. For example, a corporate site may share traffic with other corporate sites or a data center as well as connect with an Internet service provider and/or long-haul provider [3].

MANs must accommodate reconfigurations and upgrades. New customers are added to the network, leave the network, change locations, and change their bandwidth requirements and service types. Additionally, new services may be introduced by the carrier and must be supported by the network. To support changing traffic patterns and bandwidth and service requirements, optical MANs must be highly flexible. This leads to some fundamental requirements for DWDM and OADM equipment destined for metro networks [3].

MANs are particularly cost-sensitive, needing to maximize the useful life and long-term capabilities of deployed equipment while minimizing up-front investment. However, this long-term cost-effectiveness must be balanced with the required day-to-day and week-to-week flexibility of the DWDM/OADM solution [3].

5.3.1. Flexibility: What Does It Mean?

Let us define "flexibility" ...

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