Metropolitan Optical Networks

The coming of the modern information age has brought about phenomenal growth in telecommunications-based services, driven primarily by the Internet. Once where megabits were sufficient, even terabits do not suffice. As the burgeoning expansion of the Internet continues along an unprecedented and unpredictable path, many new applications are foreseen and expected. These applications are placing increasing demands from both business and private customers for ultra-scalable, flexible, transparent, terabit speed, customized bandwidth services. In concert, rapid advances in Dense Wave Division Multiplexing (DWDM) technology and the ensuing bandwidth explosion are ushering in altogether new paradigms for telecommunications networks. Driven by the increasing demand and nature of traffic, DWDM is now beginning to expand from a network core technology towards the metropolitan and access networks arenas. The successful deployment of many long-haul DWDM solutions has yielded a windfall in core transport capacity. Now, the focus is beginning to shift towards metropolitan optical networks (MONs), with the goal of bringing the benefits (cost and networks efficiencies) of the optical networking revolution to the end-users.

Popularly, MONs are defined as optical networks spanning distances up to several hundred kilometers, typically serving large, concentrated metropolitan areas. MONs bridge the space between long-haul and access networks, interconnecting a full-range of client protocols from enterprise/private customers in access networks to backbone service provider networks. This definition and responsibility of MONs presents many engineering challenges, especially in light of the large existing base of legacy SONET/SDH (Synchronous Optical Network/Synchronous Digital Hierarchy) infrastructure prevalent in current metro-area networks. These traditional TDM (time-division multiplexing) networks were originally designed to transport a limited set of traffic types, mainly multiplexed voice and private line services (such as DS-1 and DS-3). However, today's metro market is being driven by the need to streamline network efficiencies (by making them simple) under rapidly growing capacity demands and increasingly variable traffic patterns. Hence there is a strong desire to migrate from the current SONET/SDH-based network architecture into a more proactive (dynamic and intelligent), multi-service optical network. This allows service providers to avoid having to perform forklift upgrades or laying more fiber (which is time and cost intensive and legally challenging), thereby cost-effectively migrating towards a "future-proof" network.

Overall, the MON market presents many new, exciting challenges and opportunities for both equipment vendors and service providers alike. In particular, vendors who can develop timely, effective solutions to support a wide range of revenue-generating services can expect to capitalize on a vast service provider market. This gives birth to a new definition of metro optical networks called the Proactive Metro Optical Network (PMON), based on providing solutions for metro applications as opposed to solutions that are distance based. A more in-depth treatment is now presented.