With the wide application of VoIP phones, IP cameras, and wireless access points, Power over Ethernet (PoE) has made great strides in recent years. And PoE network is expected to expand rapidly in the future due to the increasing number of IoT applications and smart device deployments and newly ratified standards designed to support more smart devices. In this article, we will provide an introduction covering various aspects of PoE such as PoE wiki, PoE standards, PoE types, PoE classes, and PoE applications.

What Is Power over Ethernet (PoE)?

PoE is a networking technology that can transmit both data and power over one single standard Ethernet cable. It allows us to use network cables such as Cat5/Cat5e/Cat6/Cat6a cables to provide data connections and electric power to wireless access points, IP cameras, VoIP phones, PoE lighting and other powered devices (PDs). With the use of PoE technology, we can easily deliver power to indoor or outdoor PDs without the need to install additional electrical infrastructure or to deploy power outlets at every endpoint.

Benefits of PoE Network—Why Use Power over Ethernet?

Besides the above-mentioned benefits, there are several more appealing reasons for adopting PoE in networking.

Time & Cost Saving: By using PoE in the network, we do not need to deploy electrical wiring and outlets for terminal PDs. This will help to save much power cabling cost especially when there are lots of PDs in the network. Furthermore, there is no need to hire a qualified electrician for the PoE network, so you may also save both time and money on electrical installations.

Flexibility: Since Ethernet network cables are easier to deploy than electrical ones, PoE networking allows us to install PDs nearly anywhere rather than near the electrical outlets. This offers a ton of flexibility for setting up and repositioning terminal devices.

Reliability: PoE power comes from a central and universally compatible source rather than a collection of distributed wall adapters. It can be backed up by an uninterruptible power supply (UPS) or controlled to easily disable or reset devices. By doing so, the PDs will run as usual even though Power Sourcing Equipment (PSE) breaks down.

Evolutionary Path of the Power over Ethernet (PoE)

Institute of Electrical and Electronics Engineers (IEEE), Cisco, and the HDBaseT Alliance have released several standards to define PoE. These standards include IEEE 802.3af, IEEE 802.3at, IEEE 802.3bt, Cisco UPOE, and Power over HDBaseT (PoH).

PoE Types

Due to different classification standards, PoE can be divided into different types. Currently, there are 4 PoE types based on IEEE PoE Standard: Type 1(IEEE 802.3af), Type 2(IEEE 802.3at), Type 3(IEEE 802.3bt), and Type 4(IEEE 802.3bt), as shown in the following chart.

PoE vs. PoE+ vs. PoE++ (UPoE )vs. PoH

PoE (IEEE 802.3af), also known as PoE type 1, provides up to 15.4 watts of power per port and is used for devices like IP phones and cameras. PoE+ (IEEE 802.3at), PoE type 2, offers up to 30 watts and powers devices like PTZ cameras. PoE++ or UPoE (IEEE 802.3bt), also referred to as PoE type 3, delivers up to 60 watts and 100 watts, PoE type 4, per port for high-performance devices. Power over HDBaseT (PoH) enables power and data transmission for AV equipment over a single cable. The figure below illustrates the common applications of different PoE types for your reference.

PoE Classes

Power over Ethernet (PoE) classes define standardized power levels for different network devices. These classes ensure compatibility between Power Sourcing Equipment (PSE) and Powered Devices (PD).

The classes, ranging from Class 1 to Class 8 as the above chart shows, correspond to specific IEEE standards, indicating the maximum power output of the PSE and the maximum power input of the PD. Let’s delve into more details about each class:

Class 1 is suitable for low-power devices such as IP phones, voice-over-IP (VoIP) devices, and basic sensors.

Class 2 is intended for devices that require slightly higher power, including wireless access points, small IP cameras, and IP intercom systems.

Class 3 is commonly used for devices that require moderate power, such as larger IP cameras, point-of-sale systems, and access control devices.

Class 4 provides increased power delivery capabilities and is suitable for power-hungry devices like pan-tilt-zoom (PTZ) cameras, video phones, and thin clients.

Class 5 introduces the support for four pairs of Ethernet wires, enabling higher power transmission. It is designed for devices with more demanding power requirements, including advanced PTZ cameras, multi-channel wireless access points, and small LED lighting systems.

Class 6 provides increased power delivery capabilities beyond the previous classes. It can support devices like high-power pan-tilt-zoom cameras, multi-radio wireless access points, and small LCD displays.

Class 7 offers even higher power capabilities introduced with the IEEE 802.3bt standard. It is suitable for devices like high-performance access points, large displays, and thin clients requiring substantial power.

Class 8 represents the highest power class defined by current PoE standards. It is designed for power-hungry devices such as video conferencing systems, advanced lighting systems, and digital signage

It’s important to note that the power levels specified for each class represent the maximum allowable values, and the actual power delivered or consumed by the PD may vary based on its specific power requirements and negotiation with the PSE. Besides, understanding PoE classes allows network administrators to ensure that the power requirements of their devices align with the capabilities of their PoE infrastructure, ensuring proper operation and avoiding potential power supply issues.

Passive PoE vs. Active PoE

Power over Ethernet can also be divided into passive PoE and active PoE in general. Active PoE is the standard PoE which refers to any type of PoE that negotiates the proper voltage between the PSE and the PD device. Passive PoE is a non-standard PoE technology. It can also deliver power over the Ethernet line but without the negotiation process.

How to Add PoE to Your Network？

The PoE supplied in the network generally comes from three different sources: PoE switch, PoE injector, and PoE splitter. The PoE switch is the easiest way to power up the PDs. You only need to run Ethernet cables from a PoE network switch port to the terminal PoE device. A PoE injector is used when there is no PoE switch in the network. It has an external power supply and is responsible to add power to data that is coming from a network switch that is not PoE-capable. PoE splitters also supply power, but they do so by splitting the power from the data and feeding it to a separate input that a non-PoE-compliant device can use. It is commonly used for deploying remote non-PoE devices with no nearby AC outlets in the network.

Common FAQs on PoE Network

Q: What is the voltage of Power over Ethernet?

A: Power over Ethernet is injected onto the Ethernet cable at a voltage between 44v and 57v DC, and typically 48v is used. This relatively high voltage allows efficient power transfer along the cable, while still being low enough to be regarded as safe.

Q: What data speed does PoE offer?

A: Generally, PoE can deliver data rates at 10/100/1000Mbps over Cat5, Cat5e and Cat6 cables. Now thanks to the widespread IEEE 802.3bt PoE standard and PoE++ technology, PoE is able to deliver speeds of 2.5 Gbps to 5 Gbps over 100m and reaches 10 Gbps in recent times.

Q: Are there any limitations of PoE network?

A: Yes, PoE network does have some pesky limitations. First, it has a restricted reach of 328 feet (100 meters) which limits the viable locations where users can operate a remote IP-enabled device. Second, a single PSE such as a PoE switch usually connects to multiple PDs. If the PSE broke down, all the PDs will stop working. Therefore, it is important to buy qualified switches from a reliable supplier. In addition, you may also consider connecting the PSE to an uninterruptible power supply system.

Q: What are PoE midspan and PoE endspan?

A: The PoE midspan is usually a PoE injector that serves as an intermediary device between a non-PoE switch and the terminal PoE-capable powered device. A PoE endspan, which is commonly called the PoE network switch, directly connects and supplies both PoE power and data to a PD. PoE endspan provides power over the data pairs, also known as PoE Mode A. PoE midspan provides power using the pins 4-5 and 7-8, also known as PoE Mode B.