If you follow Nokia press releases or attended the OFC conference in San Diego, you may know that we have announced a new solution called Coherent Routing. You may wonder what hides behind this intriguing term and whether Coherent Routing may be something that has value for your business.

Operators are facing an insatiable demand for network capacity to connect people and user devices in an increasingly digital world.  Achieving this in a sustainable manner is also essential, because the resources available to support this growth are limited. The challenge for operators is to scale up their IP data networks while making a more economical use of the capital, space, power and staff required to run these networks.

Coherent Routing combines recent innovations in IP routing silicon and systems with high-density pluggable coherent interface optics and compact optical line systems to create faster and more efficient IP transport solutions for 400 Gb/s and up. It also scales and simplifies network operations by automating the management and coordination of the IP routing and optical transport domains.

Routing silicon and system integration

High-performance routers powered by the latest generation of routing silicon are the first key ingredient for scaling network capacity in more efficient ways.

Moore’s Law states that the number of transistors that can be integrated on a silicon wafer is doubling every two years. A single line card built with our 16 nm FP4 routing silicon can deliver the same port capacity as an entire router chassis equipped with our previous-generation 40 nm FP3 routing silicon. This represents an eightfold increase in fabric capacity and a 27-fold increase in port density. Our latest 7 nm FP5 silicon yields another threefold capacity increase and a 75 percent reduction in power consumption to less than 100 mW per Gbps capacity.

These leaps in router capacity and port density were made possible by a parallel evolution in the interface components used to interconnect routers. In the span of a decade, interface optics evolved from 10 Gb/s to 800 Gb/s in a pluggable module that’s about the size of your little finger.

High-density pluggable coherent optics

Recent technology advances in silicon and photonics have meanwhile succeeded in integrating digital signal processors and coherent optics with the same interface density as conventional short-reach optics. Pluggable 400G digital coherent optics (DCOs) such as 400ZR and ZR+ are game changers because they enable IP routers to interconnect directly over tunable wavelengths that can span hundreds of kilometers.

Although pluggable coherent optics easily consume twice as much power as conventional short-reach optics, this incremental cost is far outweighed by the cost, power and space savings they provide compared to using coherent optics in an external transponder.

Our high-performance aggregation, edge and core routers are design-optimized to support the full range of 400G pluggable DCOs in QSFP56-DD and CFP2 form factors without compromising on port density or operational requirements.  

Compact optical line systems and ROADMs

To connect routers equipped with 400G DCOs, operators need optical line systems with in-line amplifiers to make optimal use of the available fiber capacity and extend the reach of Coherent Routing applications over longer distances and multiple fiber spans.

Trenching fiber is costly and time consuming. Most operators have deployed line systems with reconfigurable optical add-drop multiplexer (ROADM) capabilities to virtualize and share their fiber infrastructure among multiple applications. When a dedicated fiber is not readily available to interconnect adjacent routers directly, ROADMs can provision dedicated point-to-point wavelengths that can traverse multiple fiber spans at the optical DWDM layer.

In the context of Coherent Routing, we refer to these dedicated wavelengths as IP express links because they provide direct, low-latency and zero-congestion IP transit between routers. IP express links can minimize the number of router hops that are needed to carry service traffic from source to destination. This saves on 400GE router ports, pluggable optics, and routing capacity needed for forwarding traffic, and reduces the chance that packets get lost or delayed along the way.
The savings in cost, space and power can add up quickly for 400G IP transport over metro-regional fiber rings. Depending on the ring size, the use of IP express links to connect access and aggregation routers to hub routers can reduce the number of 400G ports and associated coherent optics by a factor of three to five. 400GE router interfaces are a precious commodity that must be maximized. Every bit saved is a penny earned!

Cross-domain IP-optical coordination

As Coherent Routing applications get operationalized, this will require the IP team to coordinate operations with the optical team, which is why cross-domain IP-optical management is also an important part of the solution. However, achieving this coordination does not require a full convergence of IP routing and optical transport in one network.

There are perfectly valid reasons why so many operators manage IP routing and optical transport as separate domains and are reluctant to change this approach. Converging the IP routing and optical transport layers is complex. It can be detrimental to overall network efficiency and flexibility when the optimal IP traffic topology is constrained by the underlying fiber topology.  Nokia’s Network Service Platform (NSP) provides a rich set of cross-domain IP-optical management capabilities to allow operationalization into a wide range of network operator environments.

See it for yourself

If you missed our demo of Coherent Routing at the OFC 2022, you can watch our demo in the two videos below, and  get a glimpse of our Coherent Routing solution in action. You can also check out our Coherent Routing solution page to get more details about our solution.

Coherent Routing demonstration at OFC 2022: Part 1

Join Amir Birjandi, Principal Consulting Engineer, IP Networks, for a description of how network operators can build application-optimized IP-optical networks using Nokia’s Coherent Routing solution.

Coherent Routing demonstration at OFC 2022: Part 2

Watch Peter Landon, Product Manager for Nokia’s Network Service Platform, demonstrate end-to-end, cross-domain management of IP routers, pluggable coherent optics, and optical line systems using Nokia’s NSP platform.