Optical Network Engineering

Over the last few years we have witnessed a wide deployment of point-to-point wavelength division multiplexing (WDM) transmission technology in the Internet infrastructure. The corresponding massive increase in network bandwidth due to WDM has heightened the need for faster switching at the core of the network. At the same time, there has been a growing effort to enhance the Internet Protocol (IP) to support traffic engineering [1, 2] as well as different levels of Quality of Service (QoS) [3]. Label Switching Routers (LSRs) running Multi-Protocol Label Switching (MPLS) [4, 5] are being deployed to address the issues of faster switching, QoS support, and traffic engineering. On one hand, label switching simplifies the forwarding function, thereby making it possible to operate at higher data rates. On the other hand, MPLS enables the Internet architecture, built upon the connectionless Internet Protocol, to behave in a connection-oriented fashion that is more conducive to supporting QoS and traffic engineering. The rapid advancement and evolution of optical technologies makes it possible to move beyond point-to-point WDM transmission systems to an all-optical backbone network that can take full advantage of the available bandwidth by eliminating the need for per-hop packet forwarding. Such a network consists of a number of optical cross-connects (OXCs) arranged in some arbitrary topology, and its main function is to provide interconnection to a number of IP/MPLS subnetworks. Each OXC can switch the optical signal coming in on a wavelength of an input fiber link to the same wavelength in an output fiber link. The OXC may also be equipped with converters that permit it to switch the optical signal on an incoming wavelength of an input fiber to some other wavelength on an output fiber link. The main mechanism of transport in such a network is the lightpath (also referred to as -channel), an optical communication channel established over the network of OXCs which may span a number of fiber links (physical hops). If no wavelength converters are used, a