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December 18, 2023

Maximizing the Potential of 400ZR and OpenZR+ Within Your Network: Key Challenges & Opportunities


In a previous blog post, we provided a system engineering perspective on both 400ZR and OpenZR+, describing the technical differences between the standards. One of our key takeaways from that blog was the idea that 400G ZR and ZR+ variants have a lot of complexity built-in with their immense functionality. That complexity can lead to a plethora of implementation challenges, tripping up network operator deployments.

In today’s continuation of our starter guide, we analyze in more depth some of the most important implementation challenges of 400ZR and OpenZR+. Maximizing the full potential of these innovative, coherent technologies requires a partner with deep-seated systems engineering and integration experience. Fortunately, we can help – and our track record proves it. Let’s dive in.

From Hyperscalers to Cable Operators & Service Providers: 400ZR Evolution & IP over DWDM

As a brief refresher, the 400ZR Implementation Agreement is managed by the OIF, while OpenZR+ is organized as an MSA group. The 400ZR standard was born out of a hyperscaler desire to lower the cost of data center interconnection (DCI). It is only rated for 120km distances (with amplification) and does not have multiple modulation or data rate options. On the other hand, OpenZR+ is open to configuration for different modulation/data rates and longer distances, which offers greater flexibility for applications beyond single span DCI. Because of its potential reach of up to 100s of km (with amplification), OpenZR+ offers attractive capabilities for cable and telecom operators as well as transport network service providers looking to leverage it for applications involving multi-span ROADM and metro OTN transport as well as those requiring extended reach capabilities like multi-hop, metro-regional ROADM networks with OTN support.

By far, one of the most forward-looking advantages of 400ZR (continued with OpenZR+ and both standard’s variants collectively termed 400ZRx optics) is its enablement of Internet Protocol over Dense Wave Division Multiplexing (IPoDWDM) and the benefits that come with it. By leveraging the router-friendly QSFP-DD (or OSFP) form factor, which can be installed directly into a router or switch, 400ZRx optics eliminate the previous footprint penalty of Coherent DWDM optics that have historically been ~2x larger in size with CFP and CFP2 form factors. Originally a theoretical concept that started in the early 2000s, IPoDWDM describes the process of using coherent DWDM pluggable optics in IP routers and switches to directly interconnect ports in a router/switch to a DWDM optical line system. This IP-optical convergence was supposed to offer network operators a plethora of benefits including increased bandwidth, maximized efficiency, better scalability, lower costs and the simplification of their network architecture. Yet, as research firm Cignal AI notes, IPoDWDM has failed to gain traction outside of a few early adopters in the 20 years it has been around. Why?

Challenges of Adopting 400ZRx Optics & IPoDWDM

As the Cignal AI article goes on to say, 400ZRx optics have traditionally had some issues limiting their adoption, all of which have contributed (and in some cases still do contribute) to IPoDWDM’s difficulties in gaining full scale deployments across the industry From our perspective as a system engineering company, the three biggest ones have been the lower launch power of the initial 400ZRx optics, the significant impact on network operations to deploy this type of optic and the initial lack of full support for third party pluggables in Network Equipment Manufacturer (NEM) hosts.

As we noted in a whitepaper on 400G optics, the first generation of OpenZR+ transceivers had a similar TX output power to 400ZR optics, around -10 dBm. The latest developments in OpenZR+ transceivers have made it possible to achieve a higher TX output power at around 0 dBm, which enables network operators to use OpenZR+ optics in brownfield applications with existing ROADMs and legacy transport transponders that use similar power levels. Now, even more advanced modules are coming out with the capability of TX output powers up to +4 and +5 dBm. That bodes well for 400ZRx adoption and with it, IPoDWDM enablement.

One of the bigger remaining challenges for 400ZRx optics (and by extension IPoDWDM) revolves around network management and operations. Operators have typically been used to having different teams dealing with IP systems and Optical/Transport systems, each with their own management and operational tools. Now, the concepts of network disaggregation within the IP layer and the adoption of IPoDWDM is merging network functionalities and responsibilities from the two teams together, creating a myriad of internal challenges for cable operators, telcos and other network service providers. On the Transport side, operators have also been used to working with proprietary Network Management System (NMS) tools from Network Equipment Manufacturers (NEMs) for their network. However, the convergence of Transport and IP functions is creating demand for a new set of management tools that can handle all the capabilities and operational requirements that the implementation of 400ZRx pluggables and IPoDWDM require.

Finally, initial software (SW) releases from major NEMs have had limited support/compatibility for other pluggable optics outside of their own. This trend has improved dramatically over the last year and new SW releases have increased support for third party pluggable optics. This has helped make system integration and interoperability testing a great success as shown in the different plugfests and demos Precision participated in during 2023 as well as in multiple customer testing opportunities.

The Precision OT Advantage. Your Opportunity for Success

In many ways, the industry stands at an exciting turning point. The evolution of 400ZRx pluggables has now made wider adoption of IPoDWDM possible, but support from an interoperability and integration standpoint will be critical for forward-thinking network operators.

Here at Precision OT, we have a proven track record in that department. As mentioned above we’ve had the pleasure of participating in multiple plugfests and demos organized by the OIF during 2023. Here’s a quick timeline of our efforts:

The key takeaway from all these events is that our modules have performed successfully and interoperated seamlessly throughout all the testing they were put through. From a macro-environment perspective, the OIF’s whitepaper from the January event triumphantly proclaimed that the testing results indicated that the “400ZR module market has transitioned from the initial phase of basic functionality into an interoperable 400ZR ecosystem.” Furthermore, the results from the August event showed that all “ten vendors can operate 400 Gbps traffic over a DWDM optical line system as defined in the OpenZR+ MSA.”

For network operators of all kinds, these results can inspire confidence that it is possible to deploy 400ZR, OpenZR+ and other 400ZRx pluggable variants successfully within their networks. While further testing and development of the 400ZRx ecosystem is on the horizon, in Precision OT, you can find a partner with deep-seated expertise in interoperability and system integration. We can help you overcome the challenges of deploying 400ZRx optics and adopting IPoDWDM with our team of expert engineers. When you need trusted expertise and high-quality solutions, think Precision OT.

Ask us your questions today! We’d be happy to help.