ietary SW Figure 4-6 An example of carriers connecting using an open sources ROADM. (Courtesy of Open ROADM Multi-Source Agreement [MSA], http://OpenROADM.org) www.TechnicalPDF.com Mesh technology assumes adequate capacity on backup routes. If this capacity is not sufficient, delays will occur. It's a trade-off between flexibility in having multiple backups, idle capacity when the network is operational, cost savings, and possible congestion during emergencies. ROADMs Interoperability Plus Adding and Dropping Off Traffic Reconfigurable Optical Add/Drop Multiplexers (ROADMs) enable carriers to: Add traffic Separate out traffic Drop off traffic ROADM equipment eliminates the extra cost and maintenance for conversion equipment. Conversion equipment converts signals to electrical signals and back to light signals. Prior to the availability of ROADMs, light signals had to be converted to electrical signals before they could be added or dropped off and routed elsewhere. ROADMs were first deployed in core networks SO that, for example, some of the traffic between cities such as New York and Chicago could be more easily routed to Los Angeles. As traffic within metropolitan areas increased, ROADMs began to be used in these areas as well. Dense Wavelength Division Multiplexers (DWDMs) and OTN equipment can be equipped with ROADM cards SO fewer pieces of gear need to be maintained. ROADMs are additionally used to connect long-haul carriers to carriers in metropolitan areas. For example, ROADMs enable AT&T to drop local traffic off to local providers such as Verizon or Comcast. To transmit traffic between different telephone companies, often technicians from each company call each other to make sure their ROADMs can interoperate. The technicians often determine a way to connect via compatible www.TechnicalPDF.com Application Programming Interfaces (APIs). This causes delays in setting up connections. The Open ROADM Multi-Source Agreement (MSA), which is in tests and limited availability at providers and manufacturers, is a s