ECHNOLOGIES There are exciting advances in photonic technology. The first theme is around technologies that make it possible to build a flexible optical network where optical connections can be created between arbitrary endpoints through centralized software control. This level of flexibility is a huge enabler for process automation, improved reliability, and capacity on-demand services. The second major theme is open systems. Today's optical systems are closed proprietary systems that must be sourced from a single supplier. Industry efforts are now moving toward a model where a flexible optical network can be built by mixing and matching components from multiple suppliers-reducing cost and increasing the velocity of introduction of innovative technologies. This section starts with a short primer on the basics of optical networking and then expands on the flexible technologies and open optical systems. On the top of Figure 13.3, we show a simple triangle connection between three routers. There would not typically be a dedicated pair of fiber supporting each of the connections (A-B, B-C, and A-C). Instead, the interconnections between the routers in each of the three offices are supported by an optical transport system that provides the following functions: Multiplexing-since the deployed fiber is a precious resource its utilization needs to be maximized. To do so, technology is deployed in central offices that multiplex many optical signals onto a single fiber pair. 2. Reach-optical amplifiers (OAs) are installed inline along the fiber to boost the power of the optical signal to reverse the effects of propagation loss. 3. Switching-consider what is happening in office B in the figure. The signals from A-B and B-C are terminated in this office. However, the signal from A-C passes through office B. The optical transport system should be able to selectively allow some signals to be added/dropped while others get expressed. Today's typical commercially available optical transport systems can multiplex 96 signals, eac