Part V: PHOTONIC AND ELECTRONIC COMPONENT TECHNOLOGY
20
ROADM ARCHITECTURES AND WSS IMPLEMENTATION TECHNOLOGIES
20.1 INTRODUCTION
20.1.1 Optical Network Evolution
Optical networks are expanding at a dramatic rate to support the explosive growth of bandwidth-rich Internet video applications along with traditional voice and data services. Fiber-optic-based networks are ideal for this task because they can carry information further and in greater density than previous copper-based transmission systems. In particular, using dense wavelength division multiplexing (DWDM), optical fibers can carry upwards of 100 wavelength channels of information simultaneously, with each wavelength channel operating at high speeds (e.g., 2.5, 10, 40 Gbit/s). Fiber-optic communications has evolved from point-to-point transmission where information is transmitted between two nodes in the network, to intelligent fully meshed optical networks, where individual channels are added, dropped, and routed at individual nodes in the network. Thus, optical network architectures as we envision them now and as they are currently being deployed not only provide transmission capacities to higher transport levels, such as inter-router connectivity in an IP-centric infrastructure, but also provide the intelligence required for efficient routing and fast failure restoration. This is possible due to the emergence of optical network elements that have the intelligence ...
