⚡ Part 5: Wired & Optical IoT – Ethernet, KNX, Fiber, and PLC
- Eurth Engineering
- Oct 31
- 6 min read
When people think of IoT, they often imagine wireless sensors scattered everywhere. But in reality, some of the most reliable and mission-critical IoT deployments still rely on wires – whether it’s twisted pair, Ethernet cables, optical fiber, or even the power lines themselves.
Why? Because wires offer stability, bandwidth, security, and power delivery in one channel. For environments like factories, smart buildings, utilities, and heavy industry, wired and optical IoT technologies remain indispensable.
In this article, we’ll explore the wired and optical communication technologies in IoT – including Ethernet, KNX, BACnet, Modbus/RS485, CAN bus, DALI, optical fiber, Power Line Communication (PLC), and LiFi/FSO – their strengths, weaknesses, and real-world business cases.
🗺️ Why Wired & Optical Still Matter in IoT
While wireless dominates in flexibility, wired protocols thrive where:
High reliability is needed (no interference, guaranteed QoS).
High bandwidth is essential (video, SCADA).
Power + data must be delivered together (PoE, DALI).
Security requires physical connectivity.
Harsh environments (factories, refineries) limit wireless reliability.
Advantages:
Deterministic performance (critical in automation).
Long lifespan (Ethernet/fiber networks last decades).
Seamless integration with IT and industrial networks.
Challenges:
Higher installation cost (cabling).
Limited flexibility compared to wireless.
🔑 Key Wired & Optical IoT Technologies
1. Ethernet (and PoE)
Ethernet is the backbone of IT, and by extension, IoT. With Power over Ethernet (PoE), IoT devices can receive both data and power from the same cable.
Range: Up to 100 m (copper), kilometers with fiber.
Power: High (but provides PoE).
Data Rate: 10 Mbps → 1/10 Gbps+.
Use Cases:
IP cameras.
Industrial controllers (SCADA).
Access points and IoT gateways.
Smart kiosks and digital signage.
Pros:
High bandwidth, low latency.
Mature, global infrastructure.
PoE simplifies deployment.
Cons:
Cabling cost in large sites.
Limited flexibility in mobile devices.
Business Case Example: Large office buildings deploy thousands of IP cameras and access points powered by PoE, enabling secure IoT monitoring with a single cable run per device.
2. KNX (Twisted Pair, RF, IP)
KNX is the global standard for building automation, widely used in Europe and Asia.
Medium: Twisted pair, RF, or IP.
Range: 100 m (TP per segment).
Power: Low.
Data Rate: < 100 kbps.
Use Cases:
Lighting control.
HVAC (heating, ventilation, AC).
Shading/blinds.
Smart building automation.
Pros:
Standardized (ISO/IEC 14543).
Scalable for entire buildings.
Interoperability across vendors.
Cons:
Low data rate (not for video).
Requires specialized installation.
Business Case Example: Modern office skyscrapers in Europe use KNX for lighting and HVAC control across hundreds of floors, integrated into building management systems.
3. BACnet & Lon Works
BACnet and Lon Works are two other building automation standards.
BACnet: Open protocol for HVAC, lighting, fire systems. Widely used in North America.
Lon Works: Proprietary but strong in industrial and building automation.
Use Cases:
Energy management.
HVAC systems.
Building safety and fire alarms.
Pros:
Widely adopted in building management.
Standardized object models.
Cons:
Ecosystem fragmentation between BACnet and Lon Works.
Business Case Example: Hospitals use BACnet to integrate HVAC, fire detection, and access control into one interoperable system.
4. DALI (Digital Addressable Lighting Interface)
DALI is specialized for lighting control.
Range: 100 m.
Power: Low.
Data Rate: ~20 kbps.
Use Cases:
Commercial lighting systems.
Dimming, scheduling, occupancy-based control.
Pros:
Industry standard for lighting.
Cost-effective.
Fine-grained control.
Cons:
Narrow use case (lighting only).
Business Case Example: Shopping malls and airports use DALI to control thousands of lights with centralized scheduling for energy efficiency.
5. Modbus & RS-485
Modbus over RS-485 is one of the oldest and most reliable industrial IoT protocols.
Range: 100 m – 1 km (RS-485).
Power: Low.
Data Rate: ~100 kbps.
Use Cases:
Industrial automation.
Utility meters.
Factory sensors and actuators.
Pros:
Simple, robust, proven.
Huge installed base.
Cons:
Limited data model.
Not suited for modern IoT cloud integration (needs gateways).
Business Case Example: Factories across Asia continue to run legacy Modbus sensors, connected to modern IoT platforms via Modbus-to-IP gateways.
6. CAN Bus / CAN-FD
CAN (Controller Area Network) was designed for automotive systems, but is now used in industrial IoT too.
Range: Up to 40 m (1 Mbps), 1 km (low speeds).
Data Rate: 1 Mbps (CAN), 5 Mbps (CAN-FD).
Use Cases:
Automotive electronics.
Industrial machinery.
Elevators and robotics.
Pros:
Deterministic, real-time communication.
Robust error handling.
Cons:
Limited scalability without gateways.
Business Case Example: Automobiles use CAN bus to connect hundreds of sensors and ECUs, a precursor to IoT before cloud integration.
7. Optical Fiber for IoT
Optical fiber is the ultimate medium for high bandwidth and reliability. Beyond backhaul, fiber sensors are also used directly in IoT.
Range: 1–50 km.
Data Rate: Gbps+.
Use Cases:
High-speed IoT backhaul.
Structural health monitoring (bridges, dams).
Industrial vibration/temperature monitoring.
Pros:
Virtually unlimited bandwidth.
Immune to EMI.
Can double as a sensing medium.
Cons:
High installation cost.
Not battery-sensor friendly (infrastructure-heavy).
Business Case Example: Fiber Bragg Grating (FBG) sensors embedded in bridges detect structural stress and temperature changes for preventive maintenance.
8. PLC (Power Line Communication)
PLC uses existing electrical wiring for data transmission.
Range: 100 m – 1 km.
Power: Medium.
Data Rate: 10 kbps – 100 Mbps (depending on standard: G3-PLC, PRIME).
Use Cases:
Smart grids and smart meters.
Home automation.
Utility demand-response.
Pros:
No new cabling needed.
Strong adoption in smart grids.
Cons:
Noise interference on power lines.
Variable performance.
Business Case Example: Utilities worldwide deploy PLC in millions of smart electricity meters to communicate usage data without cellular costs.
9. LiFi & Free-Space Optics (FSO)
LiFi (Light Fidelity) uses visible/infrared light for wireless IoT, while FSO uses lasers for point-to-point optical links.
Range: LiFi (<10 m), FSO (100 m – 10 km).
Power: Medium.
Data Rate: 100 Mbps – Gbps.
Use Cases:
Secure indoor IoT networks.
Smart offices.
Point-to-point industrial links.
Pros:
High speed, interference-free.
Secure (light doesn’t penetrate walls).
Cons:
Line-of-sight required.
Ecosystem still developing.
Business Case Example: LiFi is being piloted in hospitals to create interference-free patient monitoring networks where Wi-Fi isn’t allowed.
📊 Comparison Table
Technology | Range | Power | Data Rate | Best Use Cases |
Ethernet/PoE | 100 m–km | High | Mbps–Gbps | Cameras, industrial controllers |
KNX | 100 m–1 km | Low | <100 kbps | Building automation (lighting, HVAC) |
BACnet | 100 m–1 km | Low | <100 kbps | HVAC, safety, fire alarms |
DALI | 100 m | Low | 20 kbps | Lighting control |
Modbus/RS-485 | 100 m–1 km | Low | 100 kbps | Industrial, utilities |
CAN Bus | 40 m–1 km | Low | 1–5 Mbps | Automotive, robotics |
Optical Fiber | 1–50 km | High | Gbps+ | Backhaul, structural monitoring |
PLC (Power Line) | 100 m–1 km | Medium | 10 kbps–100 Mbps | Smart grid, metering |
LiFi/FSO | 10 m–10 km | Medium | 100 Mbps–Gbps | Secure indoor IoT, P2P links |
⚖️ Business Cases
Smart Buildings (KNX/BACnet/DALI):Large commercial buildings integrate lighting (DALI), HVAC (BACnet), and blinds/shutters (KNX) into one automated management system.
Factories (Ethernet vs Modbus):Modern sensors connect over Ethernet/PoE, but legacy Modbus sensors remain in use – gateways bridge both worlds.
Automotive IoT (CAN Bus):Every car is essentially an IoT network on wheels, with 50–100+ CAN-connected sensors. Future EVs integrate CAN with cloud IoT via gateways.
Smart Grids (PLC vs NB-IoT):PLC is dominant in European smart meters. In contrast, NB-IoT is being trialed in Asia – both approaches solve the same problem with different trade-offs.
Critical Infrastructure (Fiber Sensors):Oil pipelines and dams embed fiber optic sensors to monitor stress, temperature, and leaks in real time.
Hospitals (LiFi):Patient rooms use LiFi for medical IoT devices to avoid interference with sensitive equipment where Wi-Fi is restricted.
🚀 Future Outlook
Ethernet/PoE → Expanding with higher PoE power classes for more IoT devices.
KNX/Matter convergence → KNX continues in buildings, but integration with Matter is growing.
Fiber sensing → Emerging as a new category of IoT sensor.
PLC evolution → Becoming smarter and more resilient to noise.
LiFi adoption → Early deployments in offices and hospitals; will expand with cost reductions.
🏁 Conclusion
While wireless often steals the spotlight, wired and optical IoT technologies remain the backbone of mission-critical IoT. From smart grids powered by PLC, to skyscrapers automated with KNX, to pipelines monitored by fiber optic sensors, these technologies deliver determinism, reliability, and bandwidth that wireless cannot always guarantee.
For IoT architects, the choice isn’t “wired vs wireless” – it’s about using both together:
Ethernet, fiber, and PLC for backbone reliability.
KNX, BACnet, DALI for building control.
Wireless LPWAN and short-range for distributed sensors.
The future of IoT will be hybrid by design – and wired/optical will always be part of the foundation.
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