How PoE Works

Internet connectivity is an indispensable part of today's electronic landscape. Although Wi-Fi options are widely available, many devices and network routers continue to use Ethernet ports and cables for wired internet connection. Previously, we discussed the concept of transferring data over power lines in our Power Line Communication article. Today, we delve into a related topic, "Power over Ethernet" (PoE), or the transfer of electrical power over data lines.

What is Power over Ethernet (PoE)?

PoE involves supplying electrical power through Ethernet cables. Ethernet cables, commonly used for data transfer and network connectivity, are typically not fully utilized. For instance, an Ethernet cable might have eight lines, but often only four of these lines (orange, orange-white, green, and green-white) are employed for data exchange. The other four lines remain idle and, in some lower-end Ethernet cables, may only have four lines instead of eight. These unused lines can be utilized to transfer power, giving rise to the concept of Power over Ethernet.

How Power over Ethernet Works and Why It Is Used

The primary advantage of PoE is the cost-effectiveness of providing a power supply to each peripheral connecting to the network. For instance, if you have 20 surveillance cameras distributed across a building, each camera would traditionally require a separate power supply unit. This involves running power lines to each peripheral, which is cost a lot in mean of materials , labor , containment and time wise, In such cases, PoE is an ideal solution.

Stripping Ethernet cables for each peripheral connection can be laborious. For that, we use PoE injectors and PoE splitters to make the task easier.

PoE Injector

This device has two input ports (one for connecting a regular Ethernet cable and another for connecting a DC power supply) and one output port for connecting a PoE Ethernet cable. The PoE injector's function is to provide PoE Ethernet by combining a regular Ethernet connection and DC power supply.

PoE Splitter

The PoE splitter has one input port for connecting a PoE Ethernet cable and two output ports that provide a regular Ethernet connection and DC power supply. It essentially splits the PoE Ethernet connection into regular Ethernet and a usable DC power supply, refer to Figure above

PoE Extender

A PoE extender is useful when a network spans large distances, such as in shopping malls, hotels, office buildings, campuses, and sporting venues. When regular 100-meter Ethernet connections are insufficient, a PoE extender can be used to expand network devices beyond this basic distance limit.

Today, many peripheral devices support PoE Ethernet, allowing us to bypass the splitter and connect the cable directly to the device.

For setups involving multiple appliances, purchasing a PoE injector for every device is not practical. In such cases, a PoE hub, which can replace multiple PoE injectors, is preferable.

PoE Hub

The PoE hub functions similarly to a PoE injector but can handle multiple Ethernet connections, providing corresponding PoE Ethernet outputs.

However, what if all the lines in the Ethernet cables are being used? In high-speed internet and data transfer systems where all data lines are utilized, PoE is still achievable, but it becomes more complex. Here, a special device known as a PoE switch is needed.

PoE Switch

A PoE switch is a network switch capable of providing power over Ethernet from each interface while continuing to forward frames. It acts as a port for connecting multiple PoE devices to a single PC.

PoE Standards

PoE devices follow specific standards for data communication and power delivery. These standards, which are classified based on power handling, guide the design of these devices.?

Sure, here are the Power over Ethernet (PoE) standards, which differ based on power handling capacity:

1. **IEEE802.3af (Type 1):** This standard allows for a maximum power capacity of 15.4 Watts.

2. **IEEE802.3at/PoE+ (Type 2):** Known as PoE+, this standard offers a higher power capacity of up to 30.8 Watts.

3. **IEEE802.3bt/UPoE (Type 3):** Also called Universal PoE (UPoE), it can deliver a power capacity of up to 60 Watts.

4. **IEEE802.3bt (Type 4):** This most recent standard is designed for high-powered devices and supports a maximum power capacity of 90 Watts.

PoE Applications

PoE has numerous applications, including

1- smart lighting systems,

2- smart homes,

3- security systems,

4- RFID, and alarm systems.

Limitations of PoE

Despite its many advantages, PoE has several limitations. First, the cost can be prohibitive. Although PoE can save money when dealing with numerous devices, it can be costly if only one or two PoE devices are involved. Furthermore, the complexity of installing a PoE setup may be daunting to some, with new terms and matching systems to understand whenever a new PoE device is to be installed.