How single-pair Ethernet can simplify your data network

Single-pair Ethernet (SPE) is exactly what it sounds like, an Ethernet cable that has one twisted pair of copper conductors rather than the usual four.

By Jack Sturm February 25, 2022
Courtesy: ESD

In addition to transmitting data, single-pair Ethernet (SPE) also allows for simultaneous power supply to devices using power over data line (PoDL). Before SPE, this would require two pairs of conductors for Fast Ethernet and four pairs for Gigabit speeds. While the development of SPE brings the promise of longer distance with smaller, lighter cables, it is not meant to completely replace four-pair Ethernet cabling. As this article will explore, SPE is best used for strategic applications. For building owners and operators, SPE could be the answer for connecting various business systems that do not require extensive speed or bandwidth.

The development of SPE has been in the works for years and many believe it is nearing a tipping point for widespread application. It is currently seen in the manufacturing, automotive, aerospace, and shipbuilding industries, each with their own set of standards describing network speeds and distance limitations. The following, however, will focus on the building industry.

Speed vs. distance

The value of SPE hinges on a choice between speed and distance. You can have one or the other with a copper twisted pair, but not both. The new standard for SPE in a large building includes a distance limit of 1,000 meters (3,280 feet). However, the first generation of SPE will be limited to a very slow 10Mbps Ethernet speed. This may seem like taking a step backward; 10Mbps Ethernet on twisted pair cable was the standard 30 years ago. Since then, standards were created to boost it to 100Mbps, then 1Gbps, 10Gbps, 40Gbps, and 100Gbps.

So, what is the trade-off? Distance. All the existing Ethernet on copper cable standards are based on four-pair cabling. For a number of technical reasons, four-pair cable has a distance limitation of 100 meters as opposed to the 1000-meter limit for SPE.

Signals sent through multiple pairs need to be carefully synchronized so they all arrive at the far end within a tight time frame. Another reason is that signals on each pair radiate enough noise to cause interference in the other pairs, which gets worse over distance.

Using one pair eliminates these concerns. The signal is made possible by using electronics that put all two-way data into a single pair of conductors, something we did not have with early Ethernet configurations. 1Gbps SPE (Gigabit) is part of the standard for industrial applications and is limited to 40 meters. It may be years before we see high-speed SPE out to 1,000 meters.

Practical SPE applications

A limit of 1,000 meters is almost no limit at all inside a building. That means you could theoretically route all SPE cabling from a single independent distribution frame (IDF) in a very large facility. Would this allow you to consolidate IDFs where you might otherwise have many? Before you answer, consider the devices needing faster network speeds such as workstations, printers, displays, wireless access points (WAPs), and cameras. These will still need standard four-pair Ethernet. However, SPE could lead to fewer, smaller IDFs. And if future versions of SPE are developed to support faster Ethernet speeds at long distance, the effect of reducing IDF quantities will be greater.

SPE was originally developed in the industrial sector. Manufacturing facilities and warehouses with equipment using various cabling types and protocols for monitoring or system controls have been gradually shifting to Ethernet. Typically, a very small amount of data is transferred from these devices and 10 Mbs is more than fast enough.

The same could be said for many other types of facilities. Building owners and operators can use SPE to connect systems like building controls, elevator operation, sensors, and alarm systems, to name a few. Any building system that needs communications to span long distances but does not require extensive bandwidth can take advantage of SPE.

Traditionally, sensors and controls used specialized networks to support them. Migrating these systems to Ethernet simplifies cabling and management and can potentially eliminate purpose-made networking equipment. Even at 10Mbps, SPE may offer a speed increase compared to some of the old protocols used for these devices. SPE also allows you to apply standard network security. All of this adds up to a more robust, homogenized Internet of Things (IoT) network.

As previously mentioned, SPE also supports PoDL. This is like Power over Ethernet (PoE) but tailored for use on a single pair with up to 50 Watts of power transmitted. However, voltage drop will cause it to degrade nearly 75% at 1,000 meters. If you have devices that consume 20-40 Watts, you will be able to scale distances for a custom solution. Information about how the power drops off at various distances should be available soon. Many environmental sensors consume very little power and should not be a problem for PoDL at 1,000 meters. Do not plan on SPE to support power-hungry applications like PoE lighting.

Future standards for success

Like all network technologies, SPE relies on support from the electronics industry to create the network nodes and switches.

IEEE ratified the initial standard 802.3cg for SPE in 2019. It sets the criteria for transmission of Ethernet on a single pair. This covers not only the building industry but applications for other industries that will make use of single pair.

ANSI/TIA will be releasing the new ANSI/TIA-568.5 standard soon, hopefully within the first few months of 2022. This standard is expected to outline the performance criteria for the cabling while also covering how installations are to be certified with field test equipment.

Having both standards in place helps the manufacturers know exactly what to build in terms of cables, connectors, patch panels, and more. Greater standardization will also help create increased mindshare as customers, designers, contractors, and manufacturers accept it and start installing it.

While experts do not expect the existing Ethernet infrastructures to be completely replaced by single pair wiring, they do recognize the advantages of SPE outlined above. The development of SPE has indeed been in the works for years, but I believe we are at a turning point for its widespread application—especially in the building industry.


This article originally appeared on ESD Global’s website. ESD Global is a CFE Media content partner.

Original content can be found at www.esdglobal.com.


Jack Sturm
Author Bio: Information & Communications Technology | Senior Consultant. Jack Sturm’s responsibilities include structured cabling design, data center design and technology migration consulting. He has worked on projects ranging from corporate headquarters to campus master plans to electronic trading spaces.