What is SPE and What Does it Mean for Industrial Automation?

Single Pair Ethernet is poised to become a leading communication standard for industrial automation—here’s why.

TTI has sponsored this article.

Data communication systems were originally designed to let computers and workstations—largely stationary devices in offices and data centers—share information. Cable size and weight were of little concern, and their somewhat bulky and flimsy connectors weren’t exposed to harsh conditions. But the proliferation of the Industrial Internet of Things (IIoT) and automotive communication systems has caused network designers to consider more compact and robust cabling and connector options.

One solution that is growing in popularity is Single Pair Ethernet (SPE), based on the IEEE 802.3 Ethernet communication protocol and the IEC 63171-6 cabling and connector standard. Here’s everything engineers should know about SPE and how it’s improving industrial automation.

What is Single Pair Ethernet?

Ethernet typically employs eight wires: four pairs for transmitting and receiving. Single Pair Ethernet uses one pair of wires, with the transmitter and receiver operating at different carrier frequencies over the same pair. SPE can even carry power over the data line (PoDL).

A two-wire solution reduces cable bulk and weight, facilitates tighter bends and lowers the cost of cabling. SPE’s ability to deliver power over the data line allows IIoT devices to operate without separate power supplies or batteries, and its compact connectors are suited for smaller components like sensors and cameras. Those sensors can easily send information to the cloud for data analytics via a high-speed Ethernet connection that supports data transfers up to 10 Gbps, and the spec calls for fully-shielded cables, providing maximum protection against electromagnetic interference (EMI). Additionally, SPE offers the ability to add and remove plug-and-play devices in real time.

What is IEC 63171-6?

When you think of Ethernet, you probably think of an RJ45 connector. The original RJ45 interface was an eight-wire connector designed for analog telecommunication devices (for example, the telephone), but the RJ45 that most of us know today is a digital version that has become the de facto standard for Ethernet-based LANs. As connectors go, RJ45 isn’t particularly strong or robust because it was designed to connect PCs in offices and data centers—not exactly harsh environments.

An RJ45 connector. (Stock image.)

An RJ45 connector. (Stock image.)

Even in industrial settings, RJ45 is fine for connecting workstations and servers. But with the proliferation of the IIoT, smart devices are being placed on machinery, which calls for a hardier connector. Standard Ethernet uses unshielded twisted pair (UTP) cabling, which offers a degree of immunity against moderate EMI. Again, UTP was designed for offices and data centers, which don’t generate as much EMI as large industrial equipment. For these electrically harsh environments, it’s important to use shielded cabling.

Instead of RJ45, SPE is commonly implemented with the IEC 63171-6 connector and cabling standard. Any communication system (including Ethernet) that sends bidirectional data over two wires, has a 100 Ohm impedance, and which may need power over the same wires (drawing up to four amps of current) can use IEC 63171-6 connectors for their robustness and durability.

An IEC 63171-6 SPE connector. (Image: TTI.)

An IEC 63171-6 SPE connector. (Image: TTI.)

For challenging environments like automotive and industrial applications, IEC 63171-6 connectors are compact, rugged and field terminable. They’re also available in both IP20 and IP67 rated configurations, offering protection against vibration, dust and liquids. By adhering to existing standards, IEC 63171-6 SPE interconnects are multi-sourced, decreasing the probability of supply chain issues.

How SPE and ix Industrial work together

Ethernet represents the data-link layer of the OSI networking model, making it a flexible option for networks that use multiple communication protocols. But translating from one protocol to another can result in latency, so there is a push to go fully Ethernet from top to bottom—or cloud to edge, as it were. Ethernet’s ability to coexist with other protocols gives facility managers the flexibility to upgrade their systems a little at a time.

SPE is often complemented with ix Industrial, another Ethernet cabling system that uses eight wires (four twisted pairs) for higher performance. Essentially a small, durable replacement for the RJ45 connector, ix Industrial is based on the IEC 61076-3-124 standard. While SPE can deliver bandwidths up to 1 Gbps on runs shorter than 40 meters, ix Industrial offers 10 Gbps performance at distances up to 100 meters.

Many systems use SPE at the sensor level and ix Industrial for higher bandwidth applications. The two can work in conjunction with one another, such as an industrial robot using SPE to connect its sensors to its main controller or to communicate among machines in a manufacturing cell, and employing ix Industrial to connect robots and other machinery to the factory’s LAN. ix Industrial IP20 connectors are 75% smaller than RJ45s and offer protection against shock, vibration and EMI. IP67 ix connectors offer additional protection against particulate and liquid penetration. SPE connectors, by comparison, are about half the size of their RJ45 equivalents.

Building automation systems are now adopting SPE as well, although they’re more inclined to use cabling and connectors whose specifications aren’t as rigorous as the IEC 63171-6 model. For this reason, a variety of SPE cabling protocols will emerge.

For instance, SPE can also be implemented with IEC 63171-7, which specifies a circular connector with the popular M12 form factor. In addition to two-wire bidirectional communication, this connector includes up to four dedicated power wires that can carry up to 16 amps each. In this way, a single cable could be used for systems with motors and other devices that require more current than SPE can provide by itself.

From mobility to manufacturing, SPE is surging in popularity

The automotive industry has long used the controller area network (CAN) bus as its communication standard, and it has held up well for vehicles up to this point. However, as we move to software-defined vehicles and autonomous vehicles, CAN bus’s comparatively low bandwidth (a paltry 1 Mbps) and limited expansion capabilities have been steering the industry towards SPE.

Although SPE has been around since 2011, few outside of the automotive industry have adopted it. But SPE is now poised to enter the industrial and building automation industries. Why the renewed interest? For one thing, the natural growth of SPE was hampered by the pandemic as major design changes were put on the back burner. But in the past couple years there has been a resurgence of activity on the SPE front. The return to working on-site, coupled with the rapid growth of IIoT, provides fertile ground for developing and implementing a new standard.

There’s also been a “chicken and egg” phenomenon with companies reluctant to adopt a new standard until it becomes more widespread. Few businesses are willing to gamble on a standard that could turn out to be the next Betamax. SPE seems to have reached a turning point in that regard, with larger manufacturers taking the leap and smaller ones following suit.

There are a growing number of interconnect solutions available to meet the desire. For example, the Amphenol MSPE series of plug connectors, board mount receptacles and panel mount receptacles includes IP67 and IP20 versions for both SPE and ix Industrial. Amphenol also produces adapter cables so that a system that uses a different interface can be used with SPE devices.

SPE faces competition from other standards, but advocates believe it offers the most robust solution while maintaining compatibility with other communication standards and protocols. This allows factories and buildings to gradually incorporate SPE into certain areas while keeping legacy systems intact.

To learn more about Amphenol Commercial (ACS) SPE, ix Industrial and other industrial Ethernet solutions, visit TTI.com.