Digital OTN

Most service providers would agree that current and future optical transport services can be most efficiently supported over an Optical Transport Network (OTN) architecture. The OTN standards have been evolving within the ITU since the early 90s, and most recently have been completely revised with respect to a standards-based transport for Carrier Ethernet services at all data rates. Infinera’s OTN architecture is based on a solid foundation of core OTN switching, plus a modern set of client interfaces on all the Infinera transmission platforms that off a true, any to any, end to end OTN capability. The key features of our "Digital OTN" architecture include:

  • Switched OTN Operation in the Core
  • End to End Digital OTN
  • Any Service, Minimal Hardware
  • Integrated End to End Management

Switched OTN Operation in the Core

The Infinera Digital ROADM architecture has always supported ODU1 switching and sub-wavelength grooming in the core network. This capability eliminates wavelength blocking; removes the need for muxponders; and enables an end to end GMPLS control plane.

The impact of these capabilities is that far more of the transmission capacity in the core network can be used for revenue-generating services, while new services can be brought up far more quickly compared to a traditional, all-optical network.

Figure 1a illustrates the typical problem in an all-optical network. In an all-optical solution, shown in Figure 1a, a separate optical cross connect would be required to provide OTN switching within the core network. While a ROADM is able to switch beams of light, it does not include the sub-wavelength grooming capability needed to maximize network efficiency.

Figure 1b shows the situation for a Digital OTN ROADM. Here the OTN cross-connect is fully integrated in every core node. This is enabled by the use of Infinera’s unique Photonic Integrated Circuit (PIC) capability.

Using the Digital OTN approach, wavelength blocking and the "muxponder tax" can be completely eliminated.

all-optical network vs. the Digital OTN ROADM

End to End Digital OTN

All-optical networks may offer OTN client ports, but their implementation is essentially "edge to edge", shown in Figure 2. Once the service has disappeared into the core network, all digital Performance Monitoring and OAM has been lost. Typically the only PM parameter that is available in a core ROADM is an analog Optical Signal to Noise Ratio (OSNR), which does not relate directly to the bit errors that a customer would observe. In that case your customers will know there’s a problem before you do.

In contrast Figure 3 shows that a Digital OTN network offers a true End to End service which retains full digital PM and OAM throughout the core. Amongst other things, the pre-FEC and post-FEC bit error rate monitoring at every hop can allow you to detect a fibre failure even before it results in a customer outage.

Any Service, Minimal Hardware

In Figure 4 you can see the list of services supported in the new Digital OTN architecture. What’s important is that this wide variety of service types requires only 2 interface types in the DTN, or 2 interfaces types in the ATN. Each port can be individually programmed to provide the appropriate service type. This allows service providers to offer the widest range of services with the minimum investment in hardware. It even allows new service types to be implemented on Tributary Adapter Modules (TAMs) and Service Interface Modules (SIMs) that are already in place in the network.

The Digital OTN network also eliminates the need for back to back transponders at the hub sites that link metro network into the long haul aggregation and core sites. Figure 5 shows that this handoff between the Infinera ATN and DTN nodes can be performed using a simple filter system, thus offering a considerable saving in CapEx.

The Digital OTN network can also offer service adaptation within the network itself. Figure 6 gives an example of this with an OC-192 service at Point A converted on the TAM/SIM itself to an ODU2 service at Point B.

Integrated, End to End Management

The eyes and ears of the Digital OTN network is the Infinera Management Suite. In addition to the usual FCAPS management functionality, shown in Figure 7, IMS offers features such as:

  • End to end service provisioning from metro’s edge to water’s edge
  • Automated topology discovery for metro, aggregation and core
  • End to end and hop to hop digital service monitoring

For a more detailed description of the Infinera Management Suite, please click here.