The impact of the OADX on the transport infrastructure is dramatic, even in today's predominantly SONET/SDH environment. With the increase of access-ring traffic, the use of IOF networks to interconnect these rings presents a challenge. Interconnecting multiple access rings via a combination of OADMs and OXCs requires multiple boxes, adding cost and complexity. Using WDM and OADMs to increase the capacity of the IOF fiber plant provides relief from fiber exhaustion but doesn't provide the required flexibility, simplicity, and intelligence for an efficient metro network.

In the example shown in Figure 1, five major POP sites are each inter-connecting 56 wavelengths evenly over the IOF network, which requires five large OXCs with 20 OADMs, creating seven fiber rings with 32 wavelengths each.

Figure 1. Complex Network Topology of OADMs + OXCs

The same application in an OADX configuration replaces the OXCs with OADXs and eliminates the requirement for OADMs. As seen in Figure 2, the fiber connectivity required for interconnecting the IOF is reduced from seven OADM rings with 32 WDM wavelengths interconnecting each POP to 10 point-to-point links with 16 WDM wavelengths each. The resulting network offers significantly better fiber utilization with the same levels of protection in a much simpler implementation, while providing better capacity for future growth.

Figure 2. Simpler Network Topology Achieved by OADXs

The result is a simplified network architecture that can dynamically respond to the service provider's need to roll out new service offerings:

• Support for ring, mesh, point-to-point, and point-to-multipoint topologies over a common fiber plant
• Protocol-independent protection levels with pre-emption capabilities of sub-50 ms, 50 to 200 ms, 2 second, and "best effort" that can be tailored to the service requirements
• Integrated wavelength conversion and reuse for non-blocking WDM transport
• Universal performance-monitoring module for non-obtrusive monitoring of optical and Layer-1 transport statistics for monitoring and diagnostics
• Bridge-and-roll wavelength management capabilities for hitless network optimization and maintenance
• Wavelength paths can be set up leveraging the dynamic capabilities of the generalized multiprotocol label switching (GMPLS) control plane. Control is equally critical in maximizing return on the optical transport network