Single Pair Ethernet (SPE): A Valuable Option for Modern Designs

Estimated reading time: 4 minutes

When it comes to designing PCBs and full systems for increasingly complex electronics hardware, who doesn’t want to reduce complexity and cost? Single-Pair Ethernet (SPE) has emerged as a solution and is gaining rapid attention across industrial electronics and PCB design because it enables Ethernet communication over a single twisted pair, replacing the traditional two- or four-pair cabling used in standard Ethernet networks. This seemingly simple shift has significant implications for designers: smaller connectors, reduced cable weight, longer reach, and the ability to carry both data and power over a single pair.

Simon Seereiner, business development manager at Weidmuller, and Thomas Keller, product manager, interconnect, at Rosenberger, say the solution is Single-Pair Ethernet(SPE). In this interview, they offer insight into this solution for designers grappling with today’s greatest design challenges.

Marcy LaRont: Thomas and Simon, you gave a presentation at January’s Pan-European Design Conference about SPE. Will you tell me about it and why this is such a compelling issue right now.

Simon Seereiner: Our presentation was titled, “Why Single-Pair Ethernet (SPE) is Ushering in a New Era.” SPE closes the last gap in industrial networking by making one converged Ethernet viable from edge sensors to enterprise systems, leading to simpler designs, faster rollouts, better diagnostics and security with native IP, and a clean migration path for brownfield plants. Combined with technologies like TSN and OPC UA, and with APL options for process automation, SPE turns previously isolated or cost‑prohibitive endpoints into first‑class IP participants.

LaRont: In one of your slides, you stated, “Innovation is driven by simplicity and functionality.” Can one of you reflect on that statement in view of SPE?

Thomas Keller: SPE perfectly demonstrates this statement: one pair instead of four and clear standards, while maintaining full Ethernet functionality. The simplicity of SPE lowers cost and complexity, while the functionality enables new industrial applications. That is what drives innovation.

LaRont: Please outline some key advantages for the industry.

Seereiner: Yes, key advantages include:

• Lower cost and faster installation: Thinner two‑wire cabling, smaller bend radii, and compact connectors cut material and labor while boosting port density.
• Long reach and flexible topologies: Up to 1 km on a single pair (T1L) and multidrop with T1S reduces the number of field switches and enables lean architectures.
• Data plus power on one pair: Power over Data Line (PoDL) can power and connect devices over the same conductor—up to 50 W in certain classes—simplifying panels, avoiding extra power cablesand speeding commissioning.
• Unified IP and IT/OT convergence: Native Ethernet down to the sensor streamlines software tooling, cybersecurity policies, remote service, and lifecycle management.
• Brownfield‑ready modernisation: Reuse of existing two‑wire runs and simplified retrofits make scalable condition monitoring and digitization practical.

LaRont: Now, in this industry, we talk about the need for standards and guidelines for emerging technologies. Most of us agree that having that common foundation will help accelerate our collective ability to innovate and scale more rapidly. Is that, in part, what SPE allows for on the broader communication infrastructure side for companies?

Seereiner: Yes. SPE matters in part because it is fully standards-based; IEEE 802.3 defines the PHYs (an integrated circuit that implements a physical layer), and PoDL (Power Over Data Lines), and IEC 63171-7 ensures interoperable connectors, creating a true multi-vendor ecosystem. It’s compelling because it brings Ethernet down to the smallest field devices over a single pair, combining long‑reach 10BASE‑T1L, multidrop 10BASE‑T1S, compact connectors, and standardized power to enable a consistent, scalable sensor‑to‑cloud architecture.

It converts multipair and fieldbus silos into a single converged IP network, meaning that instead of parallel fieldbuses and separate sensor wiring, plants can run a single Ethernet stack down to the device. This simplifies tools, diagnostics, and security policies across IT/OT.

Also, it allows the shift from heavy, short-reach cabling to long-reach, two-wire simplicity,  up to 1 km on a single pair, enabling coverage of sprawling lines and brownfield areas without adding layers of switches and multidrop options, further cutting infrastructure.

The bottom line is that standards-based SPE doesn’t just add another physical layer; it unlocks scale. By giving industry a single, interoperable, and power-capable Ethernet right to the edge, it accelerates product development, simplifies integration, and speeds global deployment, exactly the role you want standards to play when moving from legacy systems to a modern, IP-first plant architecture.

It facilitates today’s fragmented fieldbus and multi‑pair wiring with one converged IP network, simplifying tools, diagnostics, and security across IT/OT. Long‑reach two‑wire cabling reduces installation effort and allows coverage of large or brownfield areas without layering extra switches; multidrop further trims infrastructure.

LaRont: What is the “Age of Industrial Communication” and what does that mean practically from the designer’s viewpoint?

Keller: SPE marks the shift from decades of discrete wiring and fieldbus silos to a consistent, end-to-end Ethernet era. This takes the Age of Industrial Communication to the next level, extending Ethernet to the smallest sensors, dissolving the old IT/OT divide, and giving designers a single IP stack from edge to cloud. With its compact form factor and power efficiency, SPE enables smaller, leaner devices; at the same time, it plugs seamlessly into digital‑twin workflows and cloud systems. Crucially, Ethernet’s standardized hardware and software, rich networking capabilities, and stronger cyber resilience deliver what many fieldbuses cannot: scalable, interoperable connectivity fit for an increasingly connected world.

LaRont: What are some of the real-world use cases for SEP that PCB and system designers would relate to?

Keller: Real-world use cases include all applications that involve intelligent sensors and actuators, field devices in process and factory automation, robotics and modular machines, condition monitoring, and predictive maintenance. SPE reduces pin count, PCB area, and EMC complexity.

LaRont: In your presentation, you mention a partnership between Siemens and NVIDIA. What is that and what does it provide?

Seereiner: It connects Siemens Xcelerator with NVIDIA Omniverse to build high-fidelity, physics-based digital twins; when fuelled with SPE-based plant data, real SPE networks can be mirrored, simulated, and optimized end-to-end, from development through operations. This closes the loop between engineering and the shop floor, reducing integration risk, accelerating commissioning, and keeping assets continuously optimized with GPU-accelerated AI.

LaRont: As we wrap up, do you have any closing words of wisdom for design engineers today, especially the young ones who are just starting out and still learning?

Seereiner: SPE is unstoppable. The future industry demands a seamless, compact, high‑performance, and cost‑effective network architecture, and SPE is the Ethernet path that scales. Based on our analysis, the long‑term opportunity exceeds one billion SPE nodes, and those who think “Ethernet‑first” from the smallest sensor to the cloud will move fastest. You already speak Ethernet, so use that strength: Design with SPE early, and you’ll implement faster in your industry while reducing complexity and cost.