ow Network Core SDN Control Original path xponder xponder xponder xponder Flexible New path ROADM's xponder xponder xponder xponder FIGURE 13.7 Flexible ROADM's enable software reconfiguration of wavelengths. possible, through software, to reconfigure the original connections to use the express path. This would provide a lower latency path to the customer and because there is less inter- mediate equipment it would have higher reliability at a lower unit cost. This process of cleaning up the point-in-time accretive decisions of the past to optimize utilization of the resources is often referred to as optical "defrag." On demand services: Over time, as we predeploy transponders, wavelength services can be turned up, down, and moved via software without the need to dispatch technicians or move cables, thus enabling a whole new paradigm of capacity on demand services. Currently, AT&T has deployed a rich footprint of flexible ROADMs in the intercity network managed by an SDN controller capable of creating, deleting, and rearranging optical wavelengths via software control. These systems support 100G wavelengths today and have been designed to be extensible to 400G wavelengths as the technology becomes technically and economically viable. 13.1.3 OPEN ROADMs Today's optical networks are closed systems with all components (transponders, ROADM, ampli- fiers, etc.) sourced from a single supplier. Several industry efforts have been launched recently to remove the supplier lock-in and enable an optical network to be constructed by mixing and match- ing components from different suppliers. This section will specifically describe the Open ROADM activity. Visit the OpenROADM.org website to learn more about this effort, view the latest partici- pants, and download the specifications [7]. Building the Network of the Future Pluggable Optics Transponder ROADM (Wavelength Switching,.. G: Grey (client, well covered in standards) Wavelength MW: Multi-Wavelength FIGURE 13.8 Open ROADM reference architecture. Figure 13.8 shows the frame