Chapter 3 - Optical Networks

Abstract

This chapter provides an introduction to optical networks, focusing on the optical network layer. This layer can be found underneath the Synchronous Optical NETwork (SONET)/Synchronous Digital Hierarchy (SDH) layer. The introduction of the optical nodes into the network, through which individual wavelength channels can pass or can be terminated to the client-layer node, allows true optical networking. These nodes lessen the need for expensive optoelectronic conversions and electrical processing equipment. It has become possible to keep the passthrough traffic demand in the optical domain, by establishing lightpaths between the client-layer node equipment. At the network nodes, the transit traffic is not always converted to the electrical domain, but can stay in the optical domain until it has reached its destination. One of the possible network architectures is the mesh-based optical networks or optical networks that interconnect a ring-based part with a mesh-based part. The key component in a meshed network architecture is the optical cross-connect (OXC), the basic functionality of which is to switch a signal from an in-going port to the appropriate outgoing port.