What Is Power over Ethernet (PoE)?| Everything You Need To Know

What Is Power over Ethernet (PoE)?| Everything You Need To Know
What Is Power over Ethernet (PoE)?| Everything You Need To Know

What Is Power over Ethernet (PoE)?

Power over Ethernet (PoE) is a method for supplying DC power to devices via copper Ethernet cabling, eliminating the need for separate power supplies and outlets. Although PoE does not add Ethernet data capabilities, it does offer expanded options for how and where Ethernet end devices can be placed.

Initially, Cisco developed and delivered a proprietary version of PoE in 2000 to enable scalable and manageable power delivery to Cisco IP-telephony handsets. Emulating traditional PSTN landline phones’ operation, which deliver 48V DC power over the same copper cabling used for communications, PoE initially utilized unused pairs of the four twisted pairs of copper wires found in typical Category 5 (Cat 5) cable.

To ensure interoperability across a broader range of connected powered devices and power sourcing equipment, both the IEEE and Ethernet Alliance began working to standardize PoE in 1999. The first standard, IEEE 802.3af, was ratified in 2003 and specified that the power must be able to be carried by either spare pairs (pins 4 and 5 or pins 7 and 8) or data pairs (pins 1 and 2 or pins 3 and 6). The standard also includes a mechanism to protect devices that do not support PoE: A 25-kW resistor is added between the power pairs on the powered device, and the power source provides power only if something close to that resistive value is detected.

 

Transporting both power and data across a single cable reduced cabling needs, improved safety, and simplified installation, saving time and reducing cost. The value of PoE amplified the need for more power to support a wider variety of end devices, resulting in several additions and improvements to the 802.3af standard.

In 2009, IEEE 802.3at, known as PoE+ or Type 2, was ratified, which increased power to 30W. Cisco pioneered 60W Cisco Universal Power Over Ethernet (UPOE) in 2011, leveraging all four twisted pairs and leading to the IEEE 802.3bt standard defining 4PPoE Type 3. In 2018, the 802.3bt standard was amended to increase the maximum power to 90W from the power source known as 4PPoE Type 4.

Power over Ethernet (PoE) is a technology that delivers DC power to devices over copper Ethernet cabling, eliminating the need for separate power supplies and outlets. While PoE does not increase Ethernet data capabilities, it does expand the possibilities for where and how Ethernet end devices can be placed.

Cisco introduced a proprietary version of PoE in 2000, which enabled scalable and manageable power delivery to Cisco IP-telephony handsets. Initially, PoE took advantage of unused pairs of the four twisted pairs of copper wires found in typical Category 5 (Cat 5) cable. In 2003, IEEE 802.3af established a standard for PoE to ensure interoperability across a broader range of connected powered devices and power sourcing equipment.

With each new PoE standard, backward compatibility with all previous standards is ensured, and the minimum power per port to be supplied to the powered devices is specified. This minimum requirement accounts for power loss over the length of the cable, with a maximum length of 100m. As the power increased with each new standard, so did the cabling requirements. For instance, Type 3 (60W) and Type 4 (90W) PoE require at least Cat 5 cabling.

The introduction of 90W PoE opens up new possibilities for powering a wide range of devices, such as LED lighting, kiosks, occupancy sensors, alarm systems, cameras, monitors, window shades, USB-C-capable laptops, air conditioners, and refrigerators. The elimination of traditional “power bricks” will delight end-users, especially with the ability to have a “single cable” workspace that powers the desk phone, lamp, monitor, and laptop.

Furthermore, 90W PoE is expected to bring significant changes to smart-building and industrial applications. By combining data and power in one Ethernet cable, the transition to Ethernet-based industrial control systems will accelerate, as well as the consolidation of traditionally separate operational technology (OT) and IT-managed devices (IP phones, printers, computers, etc.).

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What are the benefits of PoE?

Using Power over Ethernet provides a number of advantages during installation:

Time and cost savings

Power over Ethernet (PoE) can decrease the cost and effort associated with installing electrical power cabling. Unlike electrical cables, network cables do not need a licensed electrician to set up. This reduces the number of power outlets needed for each device, resulting in cost savings. PoE also enables centralized management of lighting, window shades, and heating and cooling, thereby decreasing energy consumption and lowering costs.

Flexibility

Devices such as monitors, security cameras, and wireless access points can be positioned in optimal locations and can be conveniently repositioned if necessary, without being tied to electrical outlets.

Safety

PoE is built to safeguard network equipment from overload, underpowering, and improper installation through smart power delivery. This technology also eliminates the risks associated with working in the vicinity of hazardous high-voltage power sources.

Reliability

The power delivered through PoE originates from a centralized source that is compatible with various devices, and it does not depend on a collection of wall adapters. Moreover, it can be supported by an uninterruptible power supply (UPS), ensuring that devices continue to function even during power outages. PoE also offers the convenience of disabling or resetting devices from a centralized controller.

Scalability

The availability of power on the network makes the installation and distribution of network connections straightforward and efficient.

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