The way networks are built is changing. With growing demand for bandwidth and efficiency, service providers are rethinking their optical transport strategies. IP-over-DWDM (IPoDWDM) has emerged as a key approach to reducing complexity, improving scalability and optimizing cost. While cloud folks have been using this approach for years, most service providers are still struggling to find the right implementation strategies to fit their more complex environments. So, how do you implement an IPoDWDM architecture that balances performance, flexibility and long-term viability?

In this blog series, I’ll explore the critical aspects of IPoDWDM network design – from architecture strategies and selecting the right open line system (OLS) to managing IPoDWDM in a multi-vendor environment. I’ll break down key considerations for building a future-ready optical transport network and share insights on how to make IPoDWDM work for your business.

Four essential steps for effective IPoDWDM implementation

To arrive at the best possible network architecture, we recommend focusing on these four strategic areas:

• Evaluate optical bypass to reduce power dissipation and improve scalability.
• Leverage transponders and muxponders together with CPEs for high-speed wholesale services.
• Implement a consistent management and operational approach for existing services and architectures alongside new IPoDWDM services.
• Adopt an open and disaggregated multi-vendor approach supported by partnerships across the IP and optical space.

Now, let’s look at each of these areas in more detail.

Optimizing network efficiency with optical bypass

Optical bypass avoids sending transit traffic through IP routers at every node, significantly cutting power usage and hardware costs. At low capacities, routers can be interconnected directly in a daisy chain, connecting each router to the next hop-by-hop – an approach sometimes called a digital ROADM, where routers act as simple pass-through nodes. While this can simplify network architectures, it becomes less efficient as traffic and the number of interconnected nodes grows. Every router forwarding all data means increased power consumption and more transceivers. That’s where optical bypass makes a real difference – it scales more effectively, remains more cost-efficient at higher traffic levels and allows easy integration of legacy services without the need for parallel networks.

In essence, there are two main approaches to building the optical layer for IPoDWDM networks. The first is a cascade of simple point-to-point links, well-suited for highly meshed scenarios or chains and rings with low capacity. This allows for simpler planning and operations, even if it can result in higher capex. The second is an architecture with optical bypass, optimized for scalability and better equipped to support additional services, such as high-speed private lines, legacy offerings and spectrum services. 

Transponders and muxponders: The key to high-speed private lines

Routers now handle virtually all packet-based services, but when it comes to high-speed private lines, transponders and muxponders still reign supreme. High-speed private line services need physical demarcation and a stringent Layer 1 SLA, ensuring full-speed committed data rates, low latency and high availability. Using transponders with OTN wrappers for performance monitoring provides the necessary reliability and cost-efficiency, while low-cost CPE enable physical demarcation on the customer premises where required. Some architectures attempt to replace them with proprietary router-based solutions like private line emulation (PLE), but these come with cost and vendor limitations. Can you imagine deploying an expensive PLE-enabled router at each customer site? Transponders and muxponders remain the practical choice for high-speed private lines, making the optical layer the unifying technology for all services without requiring a separate OTN switching layer.

Ensuring seamless operations in open packet optical networks

Open packet optical networks are built on four key pillars: multi-vendor data plane interoperability, a unified multi-vendor control plane, consistent management of IPoDWDM alongside legacy services – which remain a staple in virtually all service provider networks – and sustainable business models that benefit all stakeholders.

To achieve this, optical transport networks must support diverse terminal devices, including 400ZR+ pluggables in routers and transponders where needed, while also implementing standardized APIs and optical domain controllers for efficient optical line system management. In short: the optical network must be open. Just as important is clear end-to-end ownership of optical service management, including pluggables and the OLS. Operational workflows must evolve to incorporate IPoDWDM services in addition to existing service management workflows, enabling true end-to-end provisioning and integrated monitoring for smooth, reliable operations. 

Finally, success depends on collaboration. All stakeholders need a viable commercial framework with well-defined roles and responsibilities to ensure long-term stability.

Advancing multi-vendor interoperability

For multi-vendor interoperability to work, open and widely accepted interface definitions and implementations are essential. Industry groups like the Telecom Infra Project (TIP) and the Optical Internetworking Forum (OIF) play a vital role in selecting appropriate standards based on operator use cases. Over the years, proof-of-concept interoperability tests have led to mature vendor implementations, enabling network operators to confidently deploy multi-vendor solutions.

From a data plane perspective, OIF has conducted 400ZR coherent pluggable interoperability tests over open line systems for several years. These efforts now extend to OpenZR+ and OpenROADM specifications, as well as to 100ZR+ and 800ZR+ transceivers. 

Adtran has been at the forefront of these developments, driving the interoperability of coherent interfaces and advancing the openness of optical line systems and domain control. The FSP 3000 OLS has played a key role in industry trials and proof-of-concept demonstrations from the very beginning. At the recent OFC 2025 in San Francisco and ECOC 2024 in Frankfurt, Germany, 100ZR+, 400ZR/ZR+ and 800ZR/ZR+ transmission and interoperability were successfully demonstrated over the FSP 3000 OLS – clear proof that interoperable solutions are maturing fast.

Looking ahead, we’ll dive deeper into key aspects of IPoDWDM. In the next post, we’ll explore how to choose the right OLS for point-to-point deployments – and what to look out for when balancing cost, capacity, long-term scalability and operational aspects.