Today's telecommunication networks support an ever-increasing mixture of statistical and deterministic data traffic. Current networks rely on time division multiplexing (TDM) hierarchy, originally invented to be the most efficient multiplexing technique possible for 64-kb/s voice, but this architecture is not particularly suited to statistical data traffic. A router or ATM switch can connect into a dense wavelength division multiplexing (DWDM) transport network by mapping packets or cells directly onto a wavelength without the intervening use of a SONET or SDH TDM. In effect, a TDM can be replaced with an optical DWDM, which can increase bandwidth utilization, facilitate networking, and reduce cost. DWDM can defer or completely eliminate the need for extra fiber, which is especially significant for providers who have a fiber-exhaustion problem, and it can easily coexist with today's SONET/SDH networks or with older fiber-optic terminals (FOTs) operating on asynchronous protocols. DWDM has already revolutionized the telecommunication industry by providing the infrastructure for long-haul optical networks. As the DWDM revolution moves into the metropolitan interoffice (IOF) and access networks, it will rely on the optical add/drop multiplexer (OADM) as its fundamental network element for metro optical networking. In this paper, we examine the market needs for metro optical networking; introduce the concept, network topology, and architectures for metro optical rings; and describe the key requirements that address the needs of service providers. We also discuss the components of the network and review the general requirements that will enable the next step in the evolution — extending the DWDM ring architecture to business access customers. Metro optical networking represents a unique opportunity for service providers to begin deploying a data-centric high-bandwidth services infrastructure.