Beginner Guide-How to Use PoE (Power over Ethernet)

Have you ever been in a situation where you want to deploy more devices in a fully-carpeted network but only to find out the biggest challenge is the missing power outlet? Typically, installing a new AC outlet will cost you $185 per unit to hire a licensed electrician to walk you through all the necessary steps in the renovation. A qualified electrician is highly needed to ensure the safety of your outlet since DIY electrical projects can be notoriously dangerous. And considering all the wiring and specific code requirements involved, you cannot possibly do it by yourself. But once you’ve got the job done, expanding your existing network systems never seems to be a problem.

But the question is: How can we successfully realize network expansion whilst keeping it within an appropriate price range? With the growing need for high-performance networks and the Internet of Things (IoT), a feasible and affordable solution is highly required to meet the demands of the average population on network upgrading. Since it’d be too troublesome and costly to install a new power outlet in the ideal location, there emerges a revolutionary way to transmit power via a network cable, called Power over Ethernet.

What is Power over Ethernet (PoE)?

Power over Ethernet (PoE) is a revolutionary technology that transmits both power and data to network devices, such as PTZ cameras, WiFi-6 access points, IP video intercoms and POS machines, through the same Ethernet cable to provide a more reliable power supply from a centralized point rather than a collection of distributed power outlets. Due to its inherent advantage, less cabling is needed for network deployment and therefore eliminates additional electrical wiring and cuts down the investment in installation. PoE is widely used in out-of-/hard-to-reach places, such as parking lots and ceilings, to send 10/100/1000 Mbps of data and 15W, 30W, 60W and 100W of power to the terminal devices over the Ethernet cables for a maximum distance of 100m.

How Does PoE Work?

PoE mainly sends power down the Ethernet cables to the PoE devices, and these Ethernet cables that meet CatX standards generally consist of 4 twisted pairs. Most Ethernet cables usually only use two of these twisted pairs for power transmission, while the others (known as data pairs) are used for data communication. Considering that separate bundles of wire are being used to carry data and power and that electricity (60Hz or less) and data (10 to 100 million Hz) are transported at opposite ends of the frequency spectrum, there is no risk of interference between the two. However, in a Gigabit cable like the CAT6e/7 cable, power and data are sent over all four pairs to deliver higher bandwidth in Gigabit networks.

PoE, PoE+, PoE++ & Hi-PoE

The PoE technology is often governed by the IEEE standard 802.3. The standard is set by the Institute of Electrical and Electronics Engineers to govern how networking equipment should operate to promote interoperability between two network devices.

Under IEEE 802.3af standard, each PoE port can support a maximum power supply of up to 15.4W at the PSE.  However, some power is always lost over the length of the cable in the form of heat dissipation, so the minimum guaranteed power available at the PD is merely 12.95W per port. However, with IEEE 802.at, PSE can deliver up to 30W on a per-port basis and the PDs can be powered with up to 25.5 Watts. Moreover, the latest IEEE 802.3bt standard introduces 2 new types of PoE standards: PoE++ and Hi-PoE. With PoE+, PSE can provide up to 60W at each port to power each PD with 51W max., while the high-power PoE or Hi-PoE can supply maximum power output of 100W at PSE and the power available at the PDs is 71.3W using the Cat6e cables.

Uses for Hi-PoE

The latest IEEE 802.3bt standard is fully backward compatible with the prior PoE standards to work with the legacy network devices. Hi-PoE can be used to support more power-hungry applications including:

• Smart building and infrastructure like LED lighting

• High-power network devices such as POS terminals, RFID readers and digital signage

• High-performance network devices like WiFi6 access points

• Security camera system (PTZ cameras) and video conference system

Mode A, Mode B and 4-pair Mode in PoE standards

As previously mentioned. the Ethernet cable consists of 4 twisted pairs and these pairs often correspond to 8 pins. PoE devices often use different pinout pairs for power transmission. And there are basically 3 supported modes available in the PoE standards: Mode A, Mode B and 4-pair Mode. With Mode A, a PoE device can deliver power directly to a powered device (PD) through the data pairs (1,2 and 3,6). Devices that utilize Mode A are often referred to as end-spans. However, the PoE device that deploys Mode B usually uses the spare pairs (4,5 and 7,8) to transport power to the connected device, and such devices are often called midspans, the intermediary equipment used between non-PoE and PoE devices. The 4-pair Mode means all the twisted pairs are used for power transportation. Please refer to the following chart to find out the supported modes in each PoE standard.

Is PoE Safe to Your Existing Network? (Active vs Passive PoE)

oE devices that are compliant with the IEEE802.3 standards are inherently safe. No damage will be caused even when they’re connected to non-PoE devices. Before the PSE sends any power to a connected PD, it will initiate a negotiation procedure called ‘power handshake’ to verify if the PD is PoE-compatible and it’ll then decide how much power the connected device requires. But the power handshake is only available in active/standard PoE – devices that are compliant with the IEEE802.3 standards. In passive/non-standard PoE, no negotiation will take place since such devices could only operate at a pre-defined voltage. So it’s very important that you know the voltage of the connected device to prevent permanent electrical damage when connected to the wrong voltage.

The handshake is normally composed of three stages: detection, classification and operation.

Detection: During this stage, the PSE sends a low voltage pulse at 2V-10V (harmless even to non-PoE devices) to the PD to make sure only the PoE-enabled devices will be powered up. It will periodically repeat this procedure until the connection is made to avoid power outages and network crashes. If the detection fails or a non-PoE device is connected, the PSE will never send any power away.

Classification: After the detection, the PSE will decide how much power the PD requires to allocate the appropriate amount of power to that load. In the classification, the PSE will categorize the PDs into different classes depending on their power requirements on the rankings of 0-8. Each PD will only draw as much power as the PSE promises to prevent over-voltage. PoE classes ensure an efficient power distribution by measuring how much power a PD requires and reallocating surplus power to high-power devices like LED lighting.

Operation: After measuring the amount of power each terminal device needs, the PSE will provide a relatively low voltage to the PDs at first and then gradually increase to 48V. During this procedure, the PSE will simultaneously convert the AC power to DC power to reduce the interference caused by alternating currents. And if the PD is disconnected midway, the PSE will immediately withdraw the power to avoid any mismatched connections. What’s more, if overcurrent occurs, the PSE will cut off all power supplies and enter into detection again. 

Advantages of Using PoE

Applications

PoE System Architecture: PSE & PD

A typical PoE system normally consists of power sourcing equipment (PSE) and at least a powered device (PD). Simply put, PSE refers to devices that can deliver power to the PoE-compatible devices, and the most common PSEs are PoE switches (endspans) and PoE injectors (midspans). The endspan can power the connected PDs directly, so there is no need for an additional power source between the PSE and the terminal devices, while the midspan is often used as an intermediary device that injects the power into a network connection where a non-PoE network switch is to be used with a PoE device. On the other hand, PDs are devices that receive power from the PSE, such as IP surveillance cameras, wireless access points and VoIP phones.

PoE Switch: Best Network Device in PoE Applications

PoE switch is a network switch that has Power over Ethernet functionality built into it. The most obvious advantage of using a PoE switch is that it offers great flexibility for installation and relocation in places where no power is present, which greatly improves the scalability of network architecture and reduces the costs of the initial investment.

The PoE switch is hot-swappable, which makes it ultra user-friendly for average families and small and medium-sized businesses. An active PoE switch is equipped with auto-sensing PoE ports that automatically detect the compatibility of the connected devices to lower the chances of power outages, operation failures, etc., and prevent irreversible electrical damages caused to the PDs. The PoE switch is widely used in different scenarios, from home to office, industry to neighborhood, indoors and outdoors, etc.

PoE Switch vs Regular Network Switch

The primary difference between a PoE switch and a network switch is that the latter only supports data transmission, so an additional power source is demanded to power the edge devices, while the PoE switch can send power and data together down the same Ethernet cable to the PDs. By using a PoE switch, you can mix PoE and non-PoE devices in the same network, while the regular switch fails to do so on its own. However, the regular switch can become PoE-enabled when connected to a PoE injector to add electrical power to the PDs.

Advantages of Using PoE switches:

• Reduced costs: An all-in-one unit that transmits power and data at the same time.

• Greater flexibility: The PoE switch can be deployed basically anywhere and makes it easy to add new network equipment to the existing network.

• Centralized power control and monitoring: The PoE switch secures better power management and allocation by optimizing the traffic on each Ethernet port. The LED displays also provide the users with real-time power information to leverage the benefits of PoE.

Types of PoE Switches

There are many types of PoE switches available in the market. They can be classified as 4 or 8-port PoE switches based on their port numbers, unmanaged and managed switches according to their management as well as commercial and hardened switches due to different setup requirements.

Port Numbers: Normally, PoE switches have different port numbers, and based on the port numbers, they can be classified into 4, 8, 16, 32 and 64-port PoE switches. A 4/8-port PoE switch is normally enough for everyday use, but the larger the network is, the greater number of Ethernet ports you’ll need. Based on how many devices you’re going to add to your networks, you can choose the suitable PoE switch that fulfills your needs, but it’s always better to choose a PoE switch that has more interfaces than you actually need for a future network expansion. Wondering how to expand the network ports on your router or network switch? Please continue to read our articleEffective Ways to Get More Network Ports for IP Devices?to find out the best way for network expansion.

Unmanaged vs Managed: PoE switches can be roughly divided into managed or unmanaged switches according to their management and configurability. The unmanaged PoE switch is a relatively simple plug-and-play device that can’t be modified or managed. The unmanaged switches are normally manufactured with a fixed configuration and with merely no security features. It’s a rather affordable option normally used in local networks where only several devices are deployed. The managed PoE switch offers full management capabilities and high-level security features that allow you to prioritize and monitor the traffic coming out of each PoE port and facilitate troubleshooting. It allows users to create new VLANs and guarantees data recovery in network failures. The managed switch is equipped with advanced security features that help avoid any type of tampering on the device. It’s ideal for applications in remote control, round-the-clock monitoring and smart buildings.

Commercial vs Hardened: Given the different setup requirements in different scenarios, the PoE switches can be further categorized into commercial-grade and hardened PoE switches. The commercial switch has a low tolerance for harsh environments since they are developed for applications in a well-controlled and air-conditioned setting like office and campus. On the other hand, the hardened PoE switch has a natural resistance to vibration, electrical noise, fluctuations in temperature and exposure to chemicals or combustible environments, which makes it an ideal option for uses in factory automation, oil and mining, public transportation projects like intersection traffic monitoring, etc. And normally, the hardened switch uses a fan-less enclosure for heat dissipation, while the commercial one is usually fan-distributed.

PoE Injector & PoE Splitter: How to Mix PoE & Non-PoE?

Since most network devices in the market are non-PoE devices, it’s necessary that you know how to mix PoE and non-PoE devices in the same network. If you want to make a non-PoE PSE compatible with a PoE-enabled PD, you’ll need a PoE injector; but if you want to connect a PoE switch with a non-PoE device, you’ll need a PoE splitter.

PoE injector

PoE injector is a device that injects the PoE capability to the regular switch and makes the non-PoE network switch work with the PoE devices. Like any other PSE, it transfers power and data to the PD on the twisted-pair cabling. It’s of great help when installing a PoE device like the wireless access point in a hard-to-reach area like the ceiling since it features a smaller footprint. Additionally, it can provide power to more power-hungry devices at a higher output when fewer PoE ports are required so as to prevent power loss in long-distance transmission. Read more about PoE injectors here.

Usually, the PoE injector needs an extra power source for itself to power up and then it will convert the AC power it receives into the DC power for the low-voltage PDs. A PoE injector normally has three ports: a power input port, a data input port and a PoE/ data and power output port. To use the PoE injector, you power the injector first, use a Cat5 Ethernet cable to connect the network switch and the injector and use another cable to connect the injector and the PD. The PoE Injector from Fastcabling is compliant with the IEEE802.3bt standard, supporting 10 Gigabit network speed with a total power budget of 95W.

PoE Splitter

PoE splitter is a device used to power non-PoE devices by splitting the power from the data and feeding it to a separate input. It often works with a PoE switch or PoE injector to power non-PoE and legacy devices in hard-to-reach places where there is no power outlet nearby. Normally, the PoE splitter has a PoE input port on the one side and two short output cables (one for power and the other for data) on the other side, but the 95W industrial-grade PoE splitter from Fastcabling has transformed these two cables into power and data (LAN) interfaces, with which you can connect the PD to the splitter directly with a power cord and an Ethernet cable, ideal for long-distance deployments.

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