8 - ROADMs and their system applications

Abstract

Subsystem and system vendors are rapidly developing and producing reconfigurable optical add/drop multiplexers (ROADMs), and carriers are installing and deploying them in their networks. This chapter is a comprehensive treatment of ROADMs and their application in WDM transmission systems and networks, comprising a review of various ROADM technologies and architectures, analyses of their routing functionalities and economic advantages, and considerations of design features and other requirements. The complex interplay between ROADM properties and optical transmission has also been explored, including a detailed discussion of static and dynamic channel power control. ROADMs enable an automated and transparent network capable of rapid reconfiguration. To fully realize this vision within the growing global communication fabric, transmission systems must be capable of dealing with continual changes, including power transients and varying transmission conditions. Network management systems must solve complex problems in routing and wavelength blocking, path verification, and more as the photonic layer assumes some of the tasks previously handled by higher layers. Advanced ROADM functionality, such as colorless add/drop ports, steerable transponders, and adaptive passbands, will be increasingly sought after, as will new and better solutions for signaling, network management, and mesh transmission. By meeting these challenges, the optical R&D community will help address the world's need for flexible, economical, and scalable networks.