What is PoE? A Guide to Power Over Ethernet

Power over Ethernet (PoE) is an innovative technology that enables both data and power transmission through a single Ethernet cable. This technology has revolutionized network infrastructure by eliminating the need for separate power cables, making installations simpler and more cost-effective. This article explores how PoE works, the benefits of using it, types of PoE powered devices and other considerations.

What is Power over Ethernet (PoE) technology?

Power over Ethernet (PoE) is an evolving technology that allows a single Ethernet cable to deliver both electrical power and network communications. This dual functionality makes it ideal for a variety of applications such as smart building infrastructure, enabling seamless connectivity for powered devices like surveillance cameras, VoIP phones and security card readers. Using PoE power over Ethernet vs. traditional AC power saves the installer time and money and makes for a cleaner, more attractive installation without the use of power cables at the device.

What is PoE? Power over Ethernet (PoE) is a technology that delivers data and power signals to connected devices through an ethernet cable (Category 5e, Category 6 or Category 6A). PoE can read and write data to and from a device, as well as power the device all with a single cable. In addition to an ethernet cable, PoE requires network equipment that is PoE-enabled.

There are two main ways to enable PoE power on a network device using Power Sourcing Equipment (PSE):

• Endspan (PoE switch) - an ethernet switch that has PoE already built in it. This switch can provide power to network devices.
• Midspan (PoE injector) - The midspan acts as a "booster" for non-PoE switches. This means it provides power and data to the network switch and the device.

How to upgrade your network using PoE devices

Upgrading your network to support PoE powered devices is straightforward, and you have three options. You can upgrade your existing network connection to PoE using: 1) a PoE switch or 2) a midspan PoE injector. A PoE injector can be installed at the non-PoE switch or midspan and injects electric power down the category cable to the device. Or, 3) use a PoE splitter. This device can split power to non-PoE installed devices such as IP door readers, security cameras and VoIP phones that require PoE power over Ethernet.

Need to use PoE with devices that are more than 100 meters away? Choose a PoE extender(s) for long-distance connections. PoE extenders transfer data from the injector and the switch to the powered devices to ensure a strong internet connection and the correct PoE voltage.

How does PoE power work?

PoE is used in a variety of systems. If a device is already enabled with PoE, then it only needs the network connection, as the PoE cable will already have power carrying throughout. To confirm whether your network device is PoE-compatible, connect it to a PoE network switch or injector to determine the device's power requirement.

Below are a few different ways powered devices implement PoE technology.

PoE-compatible devices

• VoIP phones - The earliest PoE application that lets phones have a sole power source to a wall adapter with the ability to be powered down remotely.
• IP cameras - Security technology is constantly improving, therefore, PoE creates faster deployment and repositioning needed for this type of application.
• Wireless devices - Most wireless devices are PoE compatible, allowing for more flexibility to move anywhere remotely. For example, RFID readers are PoE-compatible, which means they can be farther away from AC outlets and easily relocated.

What is a PoE network switch?

A PoE network switch is a networking PoE device that combines data transmission with power delivery through a single Ethernet cable. Assembling your first project using PoE technology is easy if you know exactly which type of PoE device you need. The three types are classified as: managed, smart (hybrid) and unmanaged.

• Managed PoE switch - This PoE device is used for enterprise networks and data centers. Typically, the managed switch provides 24/7 monitoring (on or off-site), remote control (on or off-site) features and network security.
• Unmanaged PoE switch - Used in home settings or small business offices with fewer than 10 computers. This switch cannot be altered and offers no security features. This is a basic plug-and-play device that is recommended for smaller networks.
• Smart or hybrid PoE switch - Used for smaller applications such as VoIP phones and small virtual local area networks (VLANs). The smart switch lets you set up virtual networks and assemble ports for your project.

What are the benefits of using PoE?

By combining power and data transmission into a single Ethernet cable, PoE power simplifies installations and enhances efficiency. This two-in-one source for connectivity allows the ethernet cable to easily and securely transmit power without the hassle of installation errors.

For example, if a project calls for five IP security cameras, the installer only needs to install one Category cable with PoE signals to each of the five cameras rather than installing Category cable plus 120v AC power wiring for power at each camera.

Key advantages of using PoE include:

• Time savings - Running one cable vs. multiple cables reduces the amount of time to complete your projects.
• Cost efficiency - Just like saving time, using PoE is cheaper because it uses fewer cables.
• Reliability - Power and data come from one organic single connection instead of a variety of diverse sources or wall sockets.
• Safety - Because PoE powered devices utilize a low Power over Ethernet voltage, the likelihood of overload and equipment damage is decreased, as is the risk for power outages.

PoE standards explained

Power over Ethernet standards are IEEE standards that define the maximum power levels that can be delivered to devices over an Ethernet cable. PoE standards help optimize power distribution and ensure that each device receives the appropriate amount of power. The three main Power over Ethernet standards include:

• IEEE 802.3af (PoE) - The original PoE standard that provides up to 15.4 watts of power at the source and guarantees 12.95 watts at the powered devices. This is sufficient for basic devices such as VoIP phones, security cameras, wireless access points, card readers and environmental sensors.
• IEEE 802.3at (PoE+) - This standard delivers up to 30 watts of power per port and guarantees 25.5 watts at the powered devices. This higher power level supports devices such as PTZ cameras, video conferencing equipment, displays, biometric readers and video intercoms.
• IEEE 802.3bt (PoE++) - This is the latest standard that provides up to 90 watts of power per port, and supports more demanding applications, including high-performance displays and advanced security systems.

Understanding PoE voltage

PoE voltage plays a critical role in ensuring that PoE powered devices receive the appropriate amount of power for optimal performance. Typically, PoE operates at a voltage between 44 and 57 volts DC, with 48 volts DC being the most common. The PoE voltage differs based on the standard. For example, IEEE 802.3af provides up to 15.4 watts with a voltage range of 44 to 57 volts, IEEE 802.3at supports up to 30 watts with a voltage range of 50 to 57 volts, and IEEE 802.3bt offers up to 90 watts with a voltage range of 50 to 57 volts.

What kind of network cable can I use with PoE?

Four pair, unshielded twisted pair (UTP) is the desired cable for PoE - specifically, Category 5e and Category 6 are adequate. However, Category 6A is suitable for network speeds up to 10 Gbs per second and offers better heat resistance to handle present and future high-power PoE applications.

Other considerations when using PoE power

PoE switches not only come in various management types, but they also come with varying power budgets - the total amount of power a PoE switch can deliver to a connected device.

Understanding the power requirements of the IoT devices and the PoE switch relationship is very important. As an installer, you should always be aware of the maximum power on the PoE switch's individual ports. Proper planning of PoE voltage and device compatibility is essential for a safe, efficient network, preventing future damage to your equipment and giving your PoE-powered devices a longer shelf life.