Single Pair Ethernet (SPE) extends the resources of the Industrial Internet of Things (IIoT) and helps companies to migrate to Ethernet-based operating technologies (OT) more quickly. It offers common communication protocols that are compatible with the IT network. This extension includes end-to-end solutions including switch, cable and sensor. The goal of the effort is to make the necessary changes to harmonize OT and IT operations on the most effective protocol currently available. A complete ecosystem of standards, components, end devices and applications is currently being created to fully utilize the SPE benefits.

Together with supplementary IP-based protocols, Ethernet has become the dominant data communication platform. However, other, specialized protocols still predominate where Ethernet has not yet been able to meet the requirements of the application. Multiple protocols running in parallel increase the cost and complexity of existing environments. In addition, such environments require experienced installation and maintenance personnel. AI and digitalization are increasingly leading to the use of data-based processes or machine learning. These options have been around for some time. The advantage now is that the technological dynamics of a single technology are bringing together entire system topologies. As a result, industrial Ethernet overtook traditional fieldbuses for the first time in 2018. SPE enables a homogeneous all-Ethernet network solution. The network is therefore easier to implement and manage. The single-protocol network ensures greater data transparency and increases security. The original single-pair IEEE standard 802.3cg-2019 was adopted at the beginning of 2020. At the same time, device chips were introduced to support all SPE applications in automation.

Data and energy via one line

The reduced number of wire pairs for communication reduces cable and connector size. Power and data are transported to edge devices via a single connection. Panduit's IP20 SPE connector according to IEC 63171-1 Type 1 is a small-format module with half the footprint of an RJ45 connector and has a positive latch for secure connections. Compared to terminating a 4-pair cable to the TIA-568A/B standard, terminating a 1-pair cable with the LC connector is faster and easier in the field. Using standard tools, a technician can terminate an SPE connector to the cable in half the time. In addition, 1-pair 18 AWG cables are used, which are lighter and thinner. The connection of the SPE connector is also less prone to errors.

The benefits of transmitting data and power in parallel via SPE are enormous. The IEEE 802.3bu standard provides for a decentralized DC power supply via the SPE connection, which is referred to as Power-over-Data-Line or PoDL. PoDL is comparable to Power-over-Ethernet (PoE) technology for standard Ethernet, which has already significantly changed the power supply of the data communication infrastructure in buildings. Machines, systems and buildings have single-pair twisted cable topologies that can now be used as SPE cable media. For example, many RS-485 cables have a cross-section of 18 AWG. These cables must of course be tested to ensure that they meet the TIA-568.5 standard for 10BASE-T1L transmission.

Panduit develops future communication standards. Bob Voss, senior principal engineer in Panduit's research and development department, is chairman of the Ethernet Alliance's Single-Pair Ethernet Subcommittee. The subcommittee is tasked with driving the development of a coherent roadmap for BASE-T1 Ethernet as the preferred network implementation in a single network infrastructure that integrates industrial networks into the Ethernet environment. This evolution will replace vulnerable legacy protocols with robust IP networks that offer higher data speeds, transmission distances and data and network security benefits. Due to the advantages of Ethernet and IP-based networks, consolidation to SPE environments also reduces expenses not directly related to data transmission. Ethernet networks are faster and offer advanced technologies such as Time Sensitive Networking (TSN) and Software Defined Networking (SDN).

While 4-pair Ethernet is already well established and supports higher levels in industrial networks, it is not cost effective for many edge devices. SPE is more cost-effective for wider implementation of IIoT devices. Systems currently using RS-485 serial communication can be upgraded and integrated into the Ethernet network with little modification. SPE offers increased bandwidth with data rates of up to 10 Mbps at distances of up to 1,000 meters. Compared to older protocols based on RS-485, which offer a connection speed of only 31.2 kbit/s for the same 1,000 m, the transmission speed is 300 times faster. SPE is aimed at extending data acquisition capabilities to many more edge devices for which high-speed data access was previously prohibitively expensive. The Panduit M8 connectors are MICE2/3 rated and offer IP67 protection against dust and water. As the pin coding is identical to existing sensor and fieldbus systems, the transition is made much easier.

SPE accelerates migration

Early applications for SPE include:

• Connection of skid and machine I/O blocks to the Ethernet network,
• Connection of internal machine devices to a switch,
• Connecting sensors and actuators to network switch via point-to-point or structured cable link channels, both with lengths up to 1 km,
• Connection of field devices with embedded 2-channel switches in a daisy chain
• Connection of remote I/O modules to each other, to the switch or to the controller
• Connection of control cabinet installation devices to each other via a single cable (10BASE-T1S).
• SPE is the key technology for manufacturers and industrial plants:
• Seamless networks with high transparency,
• Increased bandwidth at the network edge for the implementation of advanced diagnostics,
• Simplification of edge networks by eliminating protocol translation gateways,
• Transformation and simplification of the DC infrastructure,
• Improve cyber security,
• Connection of miniaturized micro IoT devices,
• Lower total cost of ownership

The triumph of IoT relies heavily on cost-effective technology combined with low-cost sensors to drive pervasiveness and scale. Mass-market automation products will see changes first, while specialized devices with older protocols will take longer to replace. As users see the competitive advantage of SPE, implementation of associated devices will increase dramatically and convergence to Ethernet will reduce network complexity.