Single Pair Ethernet: A Two-Wire Cable is Transforming Industrial Communications
- SPE delivers standard Ethernet communication and power over just two wires to provide connectivity from field devices to cloud analytics platforms.
- Nearly one-third of German machine builders are already planning SPE implementation, attracted by its 1,000-meter range (10x traditional Ethernet), smaller cables, higher connector density and multi-drop capability that connects multiple sensors from a single port.
- Built on open IEEE standards, SPE serves both discrete manufacturing and process industries (through the Ethernet-APL variant), with 150+ companies collaborating to avoid the fragmentation of previous fieldbus wars.
Manufacturers want “a consistent network that provides the data they need for analytics, mission critical performance and cyber resilience,” said Simon Seereiner, head of product management at Weidmuller. “Single Pair Ethernet [SPE] delivers this by bringing standard Ethernet on just two wires. With these two wires, we can also add power over data line. And that means transparent, deterministic, high-speed communication.”
As a reference point, standard Ethernet uses 8 wires arranged in 4 twisted pairs of wires. SPE has one twisted pair of wires.
This advance in cable technology addresses a critical need in manufacturing: The need for consistent, end-to-end communication from field devices all the way to cloud-based analytics platforms.
Seereiner pointed out how much the technology's impact is already being felt in the machinery sector, where nearly one-third of German machine builders are actively planning to implement SPE in their next-generation networks.
This rapid adoption rate is particularly striking compared to industrial Ethernet protocols, such as Profinet, which took 15 years to achieve its current market position as the largest adopted protocol in industrial controls, said Ken Crawford, senior director of automation at Weidmuller USA.
SPE’s use of open standards drive confidence
A key reason for SPE's key rapid advance lies in its foundation on open, international standards. The technology is standardized by IEEE, ISO and ISC, making it what Seereiner called an “independent physical layer that can use the potential of Ethernet in many different applications."
This standardization has earned endorsement from major industrial networking organizations, with both ODVA and Profinet agreeing to collaborate on SPE development. The industry momentum behind SPE is substantial as well. The SPE System Alliance and Industrial Partner Network, representing approximately 150 companies across cables, connectors, semiconductors and device manufacturing, are working to promote the technology. Major players here include Advantech, Analog Devices, Endress+Hauser, Honeywell, Phoenix Contact, Rockwell Automation, Sick and Weidmuller.
This level of cooperation is a notable aspect of SPE's development. Unlike previous "fieldbus wars" that saw competing standards from different regions or organizations, SPE represents a unified effort where the industry, on a largely global basis, has agreed on requirements and worked with end-user communities to develop technology that fits actual needs rather than regional preferences.
SPE’s practical benefits for OEMs
Weidmuller’s Crawford sees SPE as being perfectly aligned with the industry's movement toward open-architected solutions. The technology delivers what he identified as key customer requirements: "commonality, scalability, extensibility, flexibility, capability and simplification."
As a unified network, SPE can carry voice, control signals and the software drivers for modern automation hardware operation.
One particularly valuable feature is SPE's multi-drop capability, which allows multiple sensors to communicate over a single cable from one port, rather than requiring individual sensor connections to a switch. This simplifies machine design while retaining the interoperability applications that sensor manufacturers provide.
“You can just use a single port multidrop on your machine to talk to multiple sensors off of one cable, and you still get to retain all your drivers,” said Crawford. “This means you retain the interoperability applications each sensor manufacturer makes available to you. And you don't have to have those [sensor communications] converted, which a lot of the smaller, smaller shops and machine builders don't have the capability to do. So, it really accelerates the adoption and simplifies the machine.”
The physical benefits of SPE are also compelling for machine builders. SPE's smaller cables enable higher connector density, reduced weight and improved bend radius, allowing for more compact machine designs with greater flexibility for moving parts applications, said Crawford.
Extending Ethernet's reach with SPE
Arnold Offner, strategic marketing manager for automation infrastructure at Phoenix Contact, emphasized SPE's dramatic extension of Ethernet's practical range. While traditional Ethernet is limited to 100 meters, SPE can reach 1,000 meters — matching the distance capabilities of traditional 4-20 mA loops while operating at much higher speeds. "Single Pair Ethernet at 10 megabits per second in its current format allows us to use smarter instrumentation in the field to process data far quicker," Offner said. This capability enables migration from technologies like HART Communication Foundation platforms and serial fieldbus systems to bi-directional Ethernet communication.
The extended range of SPE also creates opportunities for system designers, allowing them to explore different approaches to power and data transfer at Ethernet speeds. Unlike traditional Power over Ethernet implementations that use two or four wire pairs, which Offner said can be “confusing for somebody in the field to fix,” SPE's two-wire approach eliminates confusion about connections.
Process industry applications of SPE
While SPE was initially targeted at discrete manufacturing, its applications in process industries are expanding rapidly through Ethernet-APL (Advanced Physical Layer). Essentially, Ethernet-APL uses SPE as its foundation, with modifications to meet process industry requirements for intrinsically safe operation in hazardous environments.
"There isn't really a difference between SPE and APL in the sense that SPE forms the foundation of what we do with Ethernet-APL," Offner explained. The modifications for APL include shortened distances up to 200 meters and additional safety functionality for Zone 1, Division 1 applications, but the underlying SPE technology remains the same.
This unified approach is attracting traditional process sensor manufacturers like Pepperl+Fuchs and Endress+Hauser, who are adopting both technologies to serve different application requirements while using the same underlying 10Base-T1L standard defined in IEEE 802.3cg.
SPE’s security and TSN aspects
SPE also offers significant advantages for device management and security. Crawford pointed out that when sensors and smart devices communicate over Ethernet SPE, IT and OT administrators can more easily patch, monitor and update these devices from central locations. This scalability extends to cloud-based management, enabling better security posture management across distributed industrial networks.
In addition, SPE also supports advanced features like Time-Sensitive Networking (TSN), which provides highly deterministic communication for applications requiring precise timing.
Seereiner noted that Weidmuller has been working with Texas Instruments and other manufacturers to realize gigabit TSN capabilities, which particularly benefits robot manufacturers who gain the benefit of smaller cables with better bend radius, real-time deterministic communication and the ability to power small devices like cameras directly through the network.
The technology's rapid adoption across the discrete and process industries, along with strong industry standardization efforts suggest that SPE will play an increasingly important role in industrial communications. For manufacturers evaluating their networking strategies, SPE represents a fundamental simplification of the path from sensor to cloud.
