Power over Ethernet (PoE): Understanding Versions and Voltages

In the world of networking and powering devices, Power over Ethernet (PoE) has become an increasingly popular solution. With the increasing number of IP-based devices such as wireless access points, IP cameras, and VoIP phones, PoE provides an efficient and cost-effective way to deliver power and data over a single network cable. This blog aims to shed light on PoE, explore its different versions, and discuss the varying voltages involved.

Understanding Power Over Ethernet (PoE):

Power Over Ethernet is a technology that allows electrical power to be transmitted over Ethernet cables alongside data transmission. It eliminates the need for separate power cables, simplifying installation and reducing costs. PoE can provide power to devices at the endpoint, eliminating the need for local power sources and enabling remote management and monitoring.

Different Versions of PoE:

PoE (802.3af):
This is the first standardized PoE version, capable of delivering up to 15.4 watts (including power loss) to connected devices. It operates at a voltage range of 37-57V DC. An 802.3af-compliant device can be powered by either an 802.3af power sourcing equipment (PSE) or an 802.3at PSE (backward compatibility).
PoE+ (802.3at):
Also known as PoE Plus, this version significantly boosted the power capabilities of its predecessor. PoE+ can deliver up to 30 watts of power, with 25.5 watts available to the powered device after power loss considerations. It operates at a voltage range of 42.5-57V DC. PoE+ is backward compatible with 802.3af devices, and PoE+ PSEs can support both 802.3af and 802.3at devices.
PoE++ (802.3bt):
The latest version of PoE, also referred to as PoE++, offers even higher power delivery capabilities. 802.3bt-compliant devices can provide up to 90 watts of power, allowing for more demanding devices such as pan-tilt-zoom cameras and multi-radio wireless access points to be powered over Ethernet. PoE++ operates at a voltage range of 42.5-57V DC (Type 3) or 50-57V DC (Type 4). PoE++ PSEs are backward compatible with all previous versions.

Understanding Voltages:

The voltage range of PoE is generally between 37 and 57 volts. However, specific voltages depend on the PoE version:

802.3af (PoE): This version provides a voltage range between 37 and 57 volts.
802.3at (PoE+): It maintains the voltage range between 37 and 57 volts, similar to PoE.
802.3bt (PoE++): PoE++ introduces two new voltage options. Type 3 supports a range between 42.5 and 57 volts, while Type 4 operates between 50 and 57 volts. These additional voltage options enhance power delivery capabilities for demanding devices.

Conclusion:

Power over Ethernet has revolutionized network installations by facilitating the convenient transmission of both power and data over standard Ethernet cables. With different versions of PoE available, including 802.3af (PoE), 802.3at (PoE+), and 802.3bt (PoE++), network administrators can choose a suitable solution based on the power requirements of their devices. Understanding the varying voltages associated with each PoE version is crucial for deploying and managing PoE-powered networks successfully. With the flexibility and convenience provided by PoE, we can expect to see its adoption continue to grow across various industries.