IO-Link vs Single Pair Ethernet: Sensor Connectivity

The two are not the same kind of thing: IO-Link is a complete sensor communication system, SPE is an Ethernet physical layer that carries whatever protocol the device runs.

This page compares them, alongside the other common ways to connect sensors, so you can pick the right one for each part of your plant.

What IO-Link does well

IO-Link is the established standard for connecting smart sensors and actuators to a controller. Standardised as IEC 61131-9, it runs over an unshielded three-wire cable up to 20 m and carries process data, parameters and diagnostics in both directions at 4.8, 38.4 or 230.4 kbit/s (IO-Link Interface and System Specification V1.1.4). Each sensor connects point-to-point to a port on an IO-Link master, which hands the data to the PLC.

Its strengths are real. The sensor catalogue is enormous, the device description format (IODD) makes parameterisation predictable, and integration with every major PLC platform is mature. For a machine whose sensor data exists to drive machine control, IO-Link is a well-solved problem.

Is Single Pair Ethernet an alternative to IO-Link?

Yes, Single Pair Ethernet can be an alternative to IO-Link when sensor data needs direct IP connectivity, a network identity per device or an independent path to IT systems. It is not a drop-in replacement for every IO-Link application: IO-Link remains particularly strong for PLC-centric machine control.

Alternatives to IO-Link at a glance

These technologies sit at different layers of the automation stack, and the second column says which. They are compared anyway because each is a practical way of getting sensor data from the field into control or information systems, and that is how engineers weigh them when specifying a sensor layer. Where a row is a physical layer, the comparison assumes an IP-native architecture running on it.

Scroll sideways for all columns.

Technology	What it defines	Architecture	Device model and diagnostics	Security	Reach and speed	Best fit	Compared with IO-Link
IO-Link	Complete system: physical interface, protocol and device model (IEC 61131-9)	Point-to-point, one device per master port, star from the master. The master connects onward to a fieldbus, a PLC or, on many current masters, directly to IT over MQTT, REST or OPC UA	Standardised device description (IODD); parameters, identification and events over the same link¹	No authentication or encryption on the sensor link; the specification places security at the master and in deployment²	20 m; 4.8, 38.4 or 230.4 kbit/s¹	Smart sensors on machines with a PLC master	Reference point. The first IP address sits at the master
Single Pair EthernetIEEE 802.3 single-pair PHYs: 10BASE-T1L, 100BASE-T1 and others. Ethernet-APL builds on 10BASE-T1L. Multidrop variants such as 10BASE-T1S are out of scope here	Physical layer only (IEEE 802.3). Protocol, device model and security come from what the device runs on top. Compared here as used in an IP-native architecture	Ethernet physical layer over one twisted pair; the sensor or sensor interface becomes an addressable node on a switched IP network	Depends on device and application protocol. IP-native implementations expose parameters and diagnostics over MQTT, REST or HTTPS	Standard IP security applies at the device: TLS for transport, X.509 device certificates for per-device identity, aligned with IEC 62443-4-2 component requirements¹⁴	10BASE-T1L: 10 Mbit/s, up to 1000 m, single-pair power (PoDL / SPoE) can be supported³. 100BASE-T1: 100 Mbit/s. IEEE 802.3bw specifies a 15 m link segment⁴, industrial channel specifications reach 40 m¹³, and links over 100 m work in practice with industrial single-pair cabling. Networks are extended by daisy-chaining or standard media conversion	Sensor data that also needs to reach IT systems. Brownfield retrofit: Ethernet reaches existing machines without a new control architecture, and the interface electronics are small enough and rugged enough (IP65/67) to sit in or directly ahead of the sensor. Many devices that each need their own identity	Extends Ethernet and IP connectivity to the field device. In an IP-native architecture, sensor data reaches IT systems without an IO-Link master or protocol gateway. The first IP address sits at the field device. The PLC control path can remain in parallel
AS-InterfaceASi-3 / ASi-5	Complete system: cable, protocol and profiles (IEC 62026-2)	Bus on a flat two-wire cable, data and power together	Profile-based; ASi-5 adds extended diagnostics and parameter data	None on the bus	About 100 m per segment; longer runs with repeaters and vendor-specific bus terminations, typically to a few hundred metres, with a limit of two repeaters in series⁵	Many simple I/O points along conveyors and packaging lines	Cheaper distributed wiring, less sensor-level intelligence
PROFINET	Application protocol and profiles over standard Ethernet	Industrial Ethernet, sensors typically behind remote I/O or an IO-Link master module⁶	GSDML device description; standardised diagnostics and alarms	PROFINET Security Class 1 defined (IEC 62443-aligned), implemented at controller and device level; higher classes announced, not yet published¹⁵	Standard Ethernet reach	Plants standardised on Siemens control platforms	More infrastructure. Sensors still sit behind an I/O layer
EtherNet/IP	Application protocol (CIP) over standard Ethernet and TCP/IP	Industrial Ethernet (CIP over standard Ethernet and TCP/IP), sensors typically behind remote I/O or an IO-Link master module⁷	EDS device description; CIP object model	CIP Security: TLS and DTLS, delivered as optional security profiles, so device-dependent¹⁶	Standard Ethernet reach	Plants standardised on Rockwell control platforms	More infrastructure. Sensors still sit behind an I/O layer
EtherCAT	Protocol with its own frame processing over the Ethernet physical layer	Industrial Ethernet, line or daisy chain with on-the-fly frame processing⁸	ESI device description; CoE object dictionary	None on the segment; segments are treated as a protected zone	100 m between nodes; hard real time⁸	Motion control, high-speed machines	Hard real-time determinism beyond typical sensor requirements
CC-Link IE Field Basic	Application protocol over standard Ethernet	Industrial Ethernet, software-only implementation on standard 100 Mbit/s Ethernet⁹	Cyclic I/O data; profile-based, limited diagnostics	None in the protocol	Standard Ethernet reach	Small-scale equipment in CC-Link plants, mainly Asia	Lower cost of entry than the hardware CC-Link IE variants. Sensors still sit behind an I/O layer
Modbus TCP	Application protocol over TCP/IP	Ethernet, client/server, register model	Register map only; no standard device model, vendor-specific	None in the base protocol. MODBUS/TCP Security adds TLS and x.509 certificates, but is rarely deployed¹⁷	Standard Ethernet reach	Instruments, meters, controllers already on Ethernet	Flexible and inexpensive. No standard device model
Modbus RTU	Application protocol over RS-485	RS-485 serial multidrop, register model	Register map only; no standard device model, vendor-specific	None	Up to 1000 m trunk at 9600 baud¹⁰	Instruments, meters, slow process values	Flexible and inexpensive. No standard device model
CANopen	Application layer and device profiles over CAN	CAN bus, multi-master	Object dictionary and standardised device profiles (CiA 4xx)	None in the base protocol	1000 m at 50 kbit/s; 25 m at 1 Mbit/s¹¹	Mobile machinery, embedded systems	Mature and network-oriented. Not sensor-native
Wirelessincl. IO-Link Wireless	Radio physical layer; IO-Link Wireless adds the IO-Link protocol	Radio	Technology-dependent; IO-Link Wireless keeps the IO-Link data model¹²	Technology-dependent	Site-dependent	Rotating or hard-to-cable equipment	Removes the cable, adds RF and power planning
Discrete / analogue I/O	Signal only, no protocol	Point-to-point, 24 V or 4-20 mA	None in the analogue signal itself. HART adds parameters and diagnostics on top of a 4-20 mA loop, mainly in process instrumentation¹⁸	Not applicable	Long	Simple switches and process values	Lowest cost. No diagnostics or remote configuration

The “Best fit” and “Compared with IO-Link” columns are editorial judgement, not sourced claims.

Sources

IO-Link Community, IO-Link Interface and System Specification V1.1.4, June 2024; IO-Link Design Guideline, 2018, section 2.5.
IO-Link Community, Secure Deployment Guideline 10.502 V1.0.0, June 2025.
Ethernet Alliance, 10 Mb/s Single Pair Ethernet at a Glance, 2020; IEEE 802.3cg-2019.
IEEE 802.3bw-2015 (100BASE-T1).
Bihl+Wiedemann, ASi lines longer than 100 m; AS-International Association, Technology.
PROFIBUS & PROFINET International, PROFINET.
ODVA, CIP on Ethernet Technology, PUB00138R8.
EtherCAT Technology Group, EtherCAT Technology Introduction.
CC-Link Partner Association, CC-Link IE Field Network Basic.
Modbus Organization, Modbus over Serial Line Specification and Implementation Guide V1.02, section 3.4.3.
CAN in Automation, CANopen lower layers (bit timing table, CiA 301).
IO-Link Community, IO-Link Wireless.
SPE Industrial Partner Network, Single Pair Ethernet for Industrial Applications, ANP085, 2021.
IEC, IEC 62443-4-2:2019, Security for industrial automation and control systems – Part 4-2: Technical security requirements for IACS components.
PROFIBUS & PROFINET International, PROFINET Design Guideline Security (7.362 V1.00, Nov 2025) and PROFINET Security Class 1 Guideline (7.312 V1.1).
ODVA, CIP Security.
Modbus Organization, MODBUS/TCP Security Protocol Specification V3.6, July 2021.
FieldComm Group, HART.

Two architectures, side by side

IO-Link architecture: sensors connect point to point to ports on an IO-Link master. The master holds the only IP address in the chain and passes the data on to IT systems. The sensors are not individually addressable on the network.

IP-native Single Pair Ethernet architecture: each sensor, or an interface device beside an existing sensor, holds its own IP address and reaches IT systems directly over standard IP protocols. There is no master or gateway in the data path.

The difference is not the sensor, not the PLC and, increasingly, not the protocol: MQTT at the master is common. It is where the first IP address sits, and with it identity, addressing and security.

What an IP-native SPE architecture enables

SPE brings Ethernet connectivity to the field-device layer. Sometimes that is native in the sensor; often it is an interface device sitting beside an existing sensor. What the connection is used for depends on the architecture built on top of it. An IP-native architecture, which is the approach Perinet takes, uses it like this.

Data reaches IT without a detour. The field device communicates over standard IP protocols itself. There is no IO-Link master and no protocol-conversion gateway between the sensor and the systems that consume the data. An MES, historian or analytics platform can connect to the device using standard IP protocols such as MQTT, REST or HTTPS, the same way it connects to any other IT source. IO-Link masters from several vendors offer the same protocols; the difference is that the endpoint is the master, not the sensor.

One thin cable, chained. SPE carries Ethernet over a single twisted pair, so the field cable is small. In switched architectures, field devices can be daisy-chained rather than star-wired back to a master or coupler. Power either shares the pair (PoDL / SPoE, which costs electronics at both ends and limits chaining) or runs on separate conductors in the same hybrid cable. Where a run is genuinely long, Ethernet's answer is the one it has always had: a media converter or a tunnel to the next segment. Reach is rarely the reason to choose SPE; bandwidth and device count usually are. With standard IP protocols the per-message overhead is significant, and a 10 Mbit/s segment fills up with a few dozen chatty devices where a 100 Mbit/s segment does not.

Security at the device. Per-device identity, encrypted communication and access control at the field device can help equipment makers and operators meet product-level cybersecurity requirements, including those introduced by the EU Cyber Resilience Act (Regulation (EU) 2024/2847: reporting obligations since 11 September 2026, main obligations from 11 December 2027). On the IO-Link side, the IO-Link Community's own Secure Deployment Guideline states that the sensor link provides no device authentication, authorisation or encryption, and recommends physical access control and IEC 62443 zoning as the mitigation. In a plant with a working zoning concept that is an accepted control, not a gap.

In an IP-native SPE architecture, the master layer is not required for the information path.

Where IO-Link remains the right choice

If your sensor data exists primarily for machine control and the machine already has an IO-Link master, replacing that architecture adds little. IO-Link's sensor catalogue, its parameterisation model and its integration with the PLC are mature and well supported, and the installed base is large: 71 million nodes cumulative as of 2025, after 9.7 million new installations that year. The same holds for dense, homogeneous I/O close to one master, where IO-Link's unit price per point is hard to beat; for compact machines; for sensors that only exist with an IO-Link interface; for deterministic, millisecond-range polling; for functional safety over IO-Link Safety; for actuators with real power demand on Class B ports; and for rotating or moving axes over IO-Link Wireless.

SPE becomes more interesting when the same field data also needs to reach IT, analytics or enterprise systems independently of the control path. The two coexist. Keep IO-Link where the PLC needs it. Add IP-native SPE where IT needs the data.

How Perinet implements an IP-native SPE architecture

This section describes one implementation of the architecture above. Perinet's Smart Components and periCORE use the 100BASE-T1 single-pair physical layer at 100 Mbit/s, in a daisy-chain topology rather than a star. Each hop is its own Ethernet link, so the network is not bounded by a single segment length. Power runs on separate conductors in the same cable rather than over the data pair, which keeps the device electronics small and the chain simple. Most plants do not need new sensors to do this. Existing analogue, digital and Modbus sensors connect through periNODE, available as periNODE 4-20mA, periNODE 0-10V, periNODE GPIO and periNODE Modbus. periLINE is the SPE cable. periSWITCH aggregates field devices onto the network. periMICA turns the data into monitoring, analytics and AI-ready information. Sensor manufacturers who want native SPE in their own devices embed periCORE. Each device carries its own network identity, its own certificate and its own update path.

Frequently asked questions

It can be, depending on what is built on it. SPE is a physical layer that gives a field device an Ethernet connection over one twisted pair. In an IP-native architecture, that connection lets the device deliver data directly to IT systems under its own network identity, without an IO-Link master. Where sensor data only serves machine control, IO-Link remains a strong choice.

Yes. IO-Link typically serves the control path: sensor to master to PLC. IP-native SPE serves the information path: sensor to network to IT. Many plants keep IO-Link on machines where the PLC needs the data and add SPE where analytics, monitoring or enterprise systems need it.

IO-Link is a complete sensor communication system: a physical interface, a protocol and a device description model, standardised as IEC 61131-9. 10BASE-T1L is an Ethernet physical layer standardised in IEEE 802.3cg. It defines how Ethernet runs over a single pair at 10 Mbit/s up to 1000 m, and leaves the application protocol to the device.

No. MQTT, REST and HTTPS are application protocols. SPE carries Ethernet frames, so any IP-based protocol can run over it. IP-native devices such as periNODE use MQTT and REST to publish sensor data directly to IT systems.

Not in an IP-native architecture. The sensor or sensor interface is an addressable network device, and IT systems read from it directly over standard protocols. A PLC can still read the same device or run its own control path in parallel.

No. The IO-Link Community's Secure Deployment Guideline (10.502, June 2025) states that IO-Link provides no device authentication, user authorisation or data encryption on the sensor link, and beyond a CRC no integrity protection. The recommended mitigation is physical access control and zoning per IEC 62443. IO-Link Safety, certified in 2025, is functional safety and unrelated to cybersecurity. Security for IO-Link data therefore starts at the master or the network above it; in an IP-native SPE architecture it can start at the device.

IO-Link cables are limited to 20 m between sensor and master. SPE reach depends on the physical layer: 10BASE-T1L is specified to 1000 m, and 100BASE-T1 to 15 m per link segment by IEEE 802.3bw, with industrial channel specifications reaching 40 m and links over 100 m working in practice with industrial single-pair cabling. In practice reach is rarely the deciding factor. Because SPE is Ethernet, a network is extended the way any Ethernet network is: by chaining devices, adding a switch, or bridging a long run with a standard media converter or tunnel. Bandwidth and the number of devices per segment matter more when choosing between the two PHYs.

Yes. A sensor adapter such as periNODE converts the existing 4-20 mA, 0-10 V, digital or Modbus signal into an IP-native SPE device. The sensor stays in place.

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