Overview

The dramatic shift in the architecture of optical networks is chiefly due to the development of advanced optical network elements. These elements are based on the premise that the majority of the traffic that enters a node is being routed through the node en-route to its final destination as opposed to being destined for the node. This transiting traffic can potentially remain in the optical domain as it traverses the node rather than be electronically processed. By deploying technology that enables this so-called optical bypass, a significant reduction in the amount of required nodal electronic equipment can be realized.

After briefly discussing some basic optical components and switch terminology, Sections 2.2 and 2.3 review the traditional network architecture where all traffic entering a node is electronically processed. This architecture is based on a simple optical network element, the Optical Terminal. The economic and operational challenges of these legacy networks motivated the development of opticalbypass technology. The three major network elements that are capable of optical bypass are the Optical Add/Drop Multiplexer (OADM), the Multi-Degree OADM (OADM-MD), and the All-Optical Switch, all of which are discussed in Sections 2.4 through 2.7. These elements come in many flavors; the chief attributes that affect their efficiency, cost, and flexibility are covered in these sections.

The configurability of the network elements in response to changing traffic is one of the most important attributes. In some implementations, the network element does not provide sufficient configurability at the...