Power over Ethernet (PoE) is a technology that allows both power and data to be transmitted through a single Ethernet cable. This eliminates the need for separate power supplies, simplifying installation, reducing costs, and enhancing network flexibility.
PoE technology is widely used in IP cameras, VoIP phones, wireless access points (WAPs), LED lighting, and industrial control systems.
Core concept: One cable — both power and data.
PoE technology is defined by the IEEE 802.3 standards and has evolved through several generations to support higher power delivery and wider applications.
| Standard | Common Name | IEEE Release Year | PSE Output Power | PD Power Available | Power Pairs Used | Typical Cable Type | Key Applications |
|---|---|---|---|---|---|---|---|
| IEEE 802.3af | PoE | 2003 | 15.4 W | 12.95 W | 2 pairs | Cat5 or higher | VoIP phones, IP cameras, WAPs |
| IEEE 802.3at | PoE+ | 2009 | 30 W | 25.5 W | 2 pairs | Cat5 or higher | PTZ cameras, thin clients |
| IEEE 802.3bt | PoE++ | 2018 | 60–100 W | 51–71 W | 4 pairs | Cat5e or higher | Wi-Fi 6 APs, PoE lighting, industrial systems |
Trend: Evolution of PoE Standards (IEEE 802.3af / at / bt)
A PoE system consists of two essential devices:
Definition:
A PSE is the power source in a PoE network, such as a PoE switch (Endspan) or PoE injector (Midspan). It detects the presence of a PD, negotiates power requirements, and supplies DC voltage through Ethernet cables.
PSE Types:
| Type | Location | Typical Device | Advantage |
|---|---|---|---|
| Endspan | Built into PoE switches | PoE switch | Simplifies installation, fewer devices |
| Midspan | Between switch and PD | PoE injector | Adds PoE to existing non-PoE networks |
Definition:
A PD is any device powered through the Ethernet cable by a PSE.
Examples:
Characteristics:
The power delivery process follows a specific IEEE-defined sequence:
LLDP (Link Layer Discovery Protocol) enhances PoE power management by enabling real-time communication between the PSE and PD.
Through LLDP-MED extensions, PDs can dynamically report their actual power consumption, allowing the PSE to allocate energy more efficiently.
Benefits:
Example: A Wi-Fi 6 access point initially requests 10W, then dynamically increases to 45W during high traffic via LLDP communication.
| Application | Description | Typical LINK-PP Product |
|---|---|---|
| VoIP Phones | Power and data via a single cable | LPJK4071AGNL |
| IP Cameras | Simplified surveillance setup | LPJG08001A4NL |
| Wireless Access Points | Enterprise and campus networks | LPJK9493AHNL |
| PoE Lighting | Smart building and energy control | LPJ6011BBNL |
| Industrial Automation | Sensors and controllers | LPJG16413A4NL |
LINK-PP offers a comprehensive range of PoE-compatible magnetic RJ45 connectors, integrated jacks, and transformers, all fully compliant with IEEE 802.3af/at/bt standards.
Highlighted Models:
| Model | Specification | Features | Applications |
|---|---|---|---|
| LPJ0162GDNL.pdf | 10/100 BASE-T, PoE | 1500Vrms, LED indicators | VoIP phones |
| LPJK9493AHNL.pdf | 10GBASE-T, IEEE 802.3bt | PoE++ support, Up to 90W, low EMI | High-performance APs |
Related Resources:
Q1: What is the maximum transmission distance of PoE?
A: Up to 100 meters (328 ft) using Cat5e or higher cables. For longer distances, PoE extenders are recommended.
Q2: Can any Ethernet cable be used for PoE?
A: Use at least Cat5 cable; Cat5e/Cat6 is recommended for PoE++.
Q3: How do I know if my device supports PoE?
A: Check the specification sheet for “IEEE 802.3af/at/bt compliant” or “PoE supported.”
Q4: What happens if a non-PoE device is connected to a PoE port?
A: PoE switches use a detection mechanism, so no power is sent unless a compliant PD is detected—safe for non-PoE devices.
PoE continues to evolve toward higher power levels (100W+), greater energy efficiency, and integration with smart building and IoT ecosystems.
Emerging applications include PoE-powered lighting systems, networked sensors, and industrial robotics.
The combination of PoE++ (IEEE 802.3bt) and intelligent power management protocols, such as LLDP, makes it a cornerstone for the next generation of networked power systems.
Power over Ethernet (PoE) has transformed network infrastructure by delivering both data and power over a single cable.
From small office deployments to industrial IoT systems, PoE simplifies installation, reduces cost, and enables smarter, more efficient connectivity.
With LINK-PP’s IEEE-compliant PoE magnetic connectors, engineers can design reliable, high-performance networks that meet modern power and data demands.
