The evolution of PoE technology

You already know that power over Ethernet (PoE) is a vital technology that can save substantial time and money. Did you also know that the newer PoE++ (Hi-PoE) is widely available and able to deliver up to 100 watts of power?

In this article we explore the latest developments in PoE technology and how they're beneficial.

What is PoE?

Power over Ethernet (PoE) technology allows network devices to receive electrical power over the same eight-wire Ethernet cable that connects them to the network. This means you only need to provision a single cable for each network device — you don't need a separate electrical power cable (or outlet).

The ability to send both power and data over one cable is especially useful for devices such as wireless access points, IP telephones, IP cameras, videoconferencing terminals, Internet of Things (IoT) devices, point of sale (PoS) terminals, and access and control devices used in facility management systems. You may also find some smaller network routers or switches using PoE as a power source, but this is less common.

A while back, we took a deep dive into the world of PoE, examining what it is, how it works, and why it is essential for network design. We also discovered that, at scale, PoE can help save a substantial amount of money, significantly reduce deployment and management complexity, and increase service redundancy and availability.

All of the benefits described in that article are still valid today. However, newer PoE technologies have gained a wider user base since then. These newer standards focus on both power efficiency and delivering additional power to more power-hungry devices.

Here are some developments that have emerged since we last visited the topic.

Standardized PoE

Last time, we discussed the IEEE 802.3af standard for PoE, the most prevalent form of standardized PoE at the time. The IEEE PoE standards describe what some call "active PoE" because devices using these standards actively negotiate the power requirements for the powered device.

For example, the 802.3af standard can send up to 15.4 W, 57 V, and 350 mA of power as needed.

The newer IEEE 802.3at and IEEE 802.3bt standards have since become more widely available, offering the option of more power to accommodate a broader range of device types. These standards, also referred to as PoE+ for standard 802.3at and PoE++ or High Power PoE (Hi-PoE) for standard 802.3bt, can deliver maximum power of up to 30 W  and 99.9 W, respectively. This is revolutionary because PoE can now support more energy-intensive applications like larger pan-tilt-zoom cameras, televisions, digital signs, kiosks, and more specialized IoT devices.

PoE device types

PoE-powered devices are subdivided into four device types, Type 1 to Type 4, which specify the classification of the powered device based on its power needs and capabilities. These types correspond to the specific standards that describe them.

The following table describes in more detail the capabilities of each device type.

Notes:

• PD = powered device. This is the device powered by PoE, such as an IP phone or IP camera.
• PSE = power sourcing equipment. This is the device that delivers the power, such as a PoE switch or PoE injector.
• The power and voltage values at the PSE are always higher than those at the PD because there is some attenuation of the power as it is sent over the wire.
• The 802.3bt standard can power both Type 3 and Type 4 devices, and is backwards-compatible with Type 1 and 2 devices.

Specialized PoE applications

The increased power output defined in the newer standards, particularly for Type 3 and 4 devices, supports many novel and innovative applications. This includes the relatively new trend of using what are known as "thin clients," which is rapidly increasing in popularity.

Thin clients are low-power computers that rely on a connection to a central server for processing activities. They are designed to handle user interface tasks like displaying graphics and receiving inputs, leaving the server to do the heavy lifting. This setup allows for easier management, lower hardware costs, and reduced energy consumption compared to traditional desktop PCs.

Most people use thin clients in business environments for tasks that don't require high-performance computing locally, enabling centralized control over applications and data security. Leveraging PoE for thin clients eliminates the need to run power cables to every device and allows power redundancy to be applied centrally, further enhancing availability and robustness.

PoE and network switches

Standardized PoE is typically made available on enterprise network switches. Unmanaged switches that support various types of standardized PoE will usually have some or all of their ports PoE-enabled, depending upon the switch model and capabilities. This setup is hardwired and cannot be modified.

Managed switches supporting PoE have additional capabilities, including enabling and disabling PoE on specific ports and limiting the power delivered to particular interfaces. Such switches can inform network administrators how much power the connected devices draw in real-time on a per-port basis and in aggregate. This information is typically provided on the management interface or via CLI commands.

In both cases, the power budget made available on a single PoE-enabled switch will depend upon its power supply. Some more advanced switches have modular power supplies that you can augment to accommodate more PoE-powered devices. Others can even accept a secondary power supply for a larger power budget, enabling power redundancy.

The use of PoE delivered by network switches generally improves efficiency and scalability in network design, catering to the growing demand for power in a wide range of devices.

Passive PoE

In a passive PoE system, the injector does not communicate with the powered device to negotiate its voltage or wattage requirements—it merely supplies the power it is rated for at all times. PoE injectors most often supply Passive PoE, although some also supply standardized (negotiated) PoE.

Passive PoE has undergone several improvements in the past few years. As a less strictly standardized type of PoE, its advancement depends more upon the innovation demonstrated by particular vendors. Passive PoE devices (both PDs and PSEs) are typically proprietary in design and produced with specific power parameters.

The latest passive PoE innovations focus on flexibility and safety. They often include auto-detection and power management features to prevent damage to non-PoE devices and enhanced thermal efficiency to reduce overheating risks. They also typically support cable runs longer than 100 meters without significant power loss, making the deployment of networked devices more versatile and safe.

Note: Standardized PoE PDs should never be plugged into passive PoE PSEs, as this could irreversibly damage both the PSE and the PD.

Conclusion

In recent years, PoE has seen remarkable innovations that have significantly broadened its application spectrum. With advancements enabling higher power delivery, PoE now supports a broader array of devices, from advanced digital signage to efficient building management solutions.

These examples highlight PoE's evolving role in powering the future of smart, interconnected devices. These developments not only enhance operational efficiency but also promise a greener, more versatile infrastructure for a wide variety of industries.

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