PoE (Power over Ethernet)

Power over Ethernet (PoE) is a technology that allows electrical power to be delivered to devices over standard Ethernet cables. This means that a single cable can provide both power and data connections, eliminating the need for separate power supplies and electrical outlets. PoE is particularly beneficial for devices like IP cameras, wireless access points, and VoIP phones, which can be installed where there are no power outlets available.

PoE works by utilizing the copper wires within an Ethernet cable to transmit DC power to devices. This is achieved through two main methods: using the spare pairs of wires in the Ethernet cable or using the data pairs themselves. The initial standard, IEEE 802.3af, also known as PoE Type 1, was introduced in 2003. It provides up to 15.4 watts of power and uses either the spare pairs or the data pairs for power transmission. It also includes a safety mechanism to prevent damage to non-PoE devices by using a 25-kΩ resistor to detect if a device is PoE-compatible.

To support devices requiring more power, the IEEE 802.3at standard, or PoE+ (Type 2), was introduced in 2009. This standard allows for up to 30 watts of power. Cisco further extended PoE capabilities with their Universal Power Over Ethernet (UPOE) technology, which provides up to 60 watts by using all four twisted pairs in the cable. The IEEE 802.3bt standard, ratified in 2018, further increased the power to 60 watts for Type 3 and 90 watts for Type 4, also known as 4PPoE.

These advancements in PoE technology have allowed for a broader range of devices to be powered, including LED lighting, kiosks, occupancy sensors, and even laptops and small appliances. PoE simplifies installations, enhances flexibility, improves safety, and allows for central management of power delivery. It also supports uninterrupted power supply (UPS) for critical devices, ensuring continuous operation even during power outages. This makes PoE an essential technology for modern network infrastructure, supporting both data and power needs efficiently.