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Single Pair Ethernet

With SPE - Single Pair Ethernet - a single twisted pair line in a cable is used for data transmission and optionally for power supply.

Single Pair Ethernet can transmit data at speeds from 10 Mbit/s up to 10 GBit/s with only one pair of wires, but requires significantly less space in the cable and much smaller connection space. This technology was initiated for the purpose of increasingly powerful Ethernet on-board networks in vehicles but nevertheless simple cabling design.

SPE - Increasingly powerful Ethernet & simple cabling design

PI has always been driving digitalization and Industrie 4.0 applications. This has not only been about communication protocols, but Time Sensitive Networking (TSN), OPC UA or Advanced Physical Layer (APL) have also been integrated into PI's technology set.

Now, with SPE, a new technology is in the starting blocks.

SPE is interesting for industrial automation, intelligent building networks, or IoT applications because the end devices - sensors or actuators - can be operated cost-effectively at the field level with sufficient data bandwidth.

They can also be connected without complexity to existing IT networks.

Many therefore see SPE as an 'enabler' for IoT applications.

Single Pair Ethernet thus fits into the 'big picture' of PI technologies and can help improve or complement the automation of diverse manufacturing.

However, SPE is not a self-runner, but first requires the definition of use-cases and their technical evaluation.


The technical evaluation of SPE

SPE bundles a number of standards that build on the specifications of the IEEE 802.3 family.

The advantage:

The previous structures of the Ethernet frame remain untouched. Only the physical layer, i.e. the cables, connection technology, and electrical signals, are redefined. PROFINET or OPC UA can use this new physical layer unchanged.

Due to the technical constraints of the intended target markets and the implementation possibilities, various sub-standards have been developed, which differ primarily in terms of data rate and possible line length. In addition, different power classes are available for power supply. Consequently, there will not be just one integration, but the best solution for an application will be used in each case.

From the user's point of view, SPE improves the device connection for devices with integrated power supply. This is interesting for sensor wiring, for example. This enables faster commissioning, more robust connections, and smaller housings.

Robots and cranes too will benefit from the greater flexibility provided by thinner cabling.

The challenge:

Suppliers of sensors and actuators usually address several target industries with their components. Should manufacturers now develop, test, approve, produce and stock each device with a different implementation?

In addition, the introduction of any new technology is often accompanied by an increased training effort for end-users. New devices, settings, and documentation are necessary. In addition, SPE consists of several technologies, encompassing different cable lengths, types, and speeds. This results in a wide range of possible combinations, but not all of them can be advanced, developed, and implemented at the same time. PI therefore accompanies this development process and evaluates the technologies based on use-cases.

General improvement of existing wiring solutions

There exist more robust connection options than RJ45.

The SPE connectors presented are robust by design and developed for industrial applications. This includes, among other things, a secure contact transition, a consistent shielding concept and a strong locking mechanism. Another argument: When assembling the connectors, only two wires need to be connected instead of four (100 Mbit/s) or eight (Gbit/s).




Wiring solutions over longer distances:


A substandard of SPE enables line lengths of up to 1000 m at 10 Mbit/s transmission rate. This specification uses Ethernet-APL and makes it possible, for example, to replace switch cascades or previously necessary fiber optic links.


Solutions for smaller I/O devices:


The smaller footprint due to the smaller connector and the integration of the power supply enables smaller housings for devices. This opens up new connection options for additional devices in machines and systems, and the collection of additional data for I4.0 use-cases.


More flexible cables:

Mechanical flexibility and weight play an important role in cabling in robotic arms. SPE could therefore play a greater role in applications where cabling with a smaller outer diameter, smaller bending radius, and low weight is required.

Expansion of existing systems:


Especially in existing systems, the integration of new components is easier than with eight-core cables. With the thinner and lighter cables, more Ethernet channels can be accommodated in existing cable trays than before.




Here you can find several frequently asked questions:

PI will maintain proven validation and deployment processes for SPE. At the same time, PI is already in contact with other user organizations to clarify standardization issues, such as aspects of cabling or connection. In the course of the process, the specification of diagnostics and configuration, the certification of the devices, and the creation of guidelines with regard to installation, commissioning, and validation will follow.

When it comes to connecting both simple and more complex sensors at the last meter within factory automation, IO-Linkhas fulfilled this role up to now. However, developments around the topic of the smart factory are constantly placing new demands on the way devices communicate with each other. From the point of view of IO-Link, for example, extensions were necessary with regard to safety applications or wireless communication.

Now a new question arises again:

With the dynamic expansion of the portfolio of IO-Link devices and the accompanying expansion of the potential fields of application, IO-Link is sometimes coming up against technological limits.

For example, there are definitely requirements to transmit IO-Link over greater distances than the currently specified 20 m. Single Pair Ethernet is filling precisely this gap and could take over such tasks.


Transmission rates range from 10 Mbit/s at a transmission length of 1,000 m to 1 Gbit/s at 40 m.

With SPE, the power supply of connected periphery can be realized via PoDL (Power over Data Line).

PoDL defines different voltage levels (12V, 24V, 48V) and different power classes up to 60 W at the PSE (Power Source Equipment).

Thus, an additional, separate supply line is not necessary.

SPE describes a group of Ethernet standards with different transmission rates. Ethernet-APL uses one of these standards and specifies properties that are important for use in process automation.

For example, screw and spring terminals are mostly used in the process industry. Explosion protection also plays a very important role, which entails additional effort in development and certification.

This is usually unnecessary for manufacturing automation, so discrete manufacturing relies on a technically less complex SPE standard. APL also defines its own power class.

For details, see APL highlight.