Optical Add/Drop - Outside and Inside the Box

摘要

I will review the technology and applications of optical add/drop, concentrating on reconfigurable add/drop for next-generation systems. Representative designs will be presented, and discussed in terms of their flexibility, cascadability, scalability, impairments, and special features. Optical add/drop is a defining feature of true optical networking, enabling the realization of complex network topologies without regeneration of signals at every node. Virtually all Optical Add/Drop Multiplexers (OADMs) of interest today are based on wavelength selection and routing, and are used to extract individual wavelength channels from an incoming DWDM stream and to insert replacement wavelength channels into the outgoing DWDM stream. Metro ring networks have been the proving ground for OADMs, using optical pass-through to reduce regenerator costs, but first-generation systems were limited to fixed routing patterns. Next-generation metro and long-haul systems are being designed to incorporate Reconfigurable OADMs (ROADMs), to combine these cost savings with at least some of the flexibility associated with electronic (e.g. SONET) add/drop terminals.