The Power over Ethernet (PoE) simply the cabling, save time and cost. The single Ethernet cable can transmit both power and data to each edge device. Where the cables go, the power and data follow. It eliminates the extra power cord.
Usually, there are Power supply Equipment (PSE) and Powered Devices (PD) in the standard POE system. The PoE Switch, PoE injector, PoE NVR belong to PSE. This equipment can provide not only the power but also the data to the edge device. The PoE Switch looks exactly the same as a convenient switch. Only the Power source is built-in to the switch to supply the power to each edge device. The PoE IP camera, access point, VoIP belong to PD which can receive the power from the PoE Switch and regulate to suitable voltage, meanwhile, separate the data from the power for the communication.
Why PoE is safe?
The PoE Power system is a safe solution. The power transmits over the Ethernet cable is DC power. The PoE Switch or injector will convert the AC power to DC before injecting it to Ethernet cable. Moreover, there is a power handshake between the PoE Switch and the edge device. The PoE Switch or PoE injector will send a small current to verify and classify the edge device. If the edge device is not POE compatible, the PoE Switch will only provide data exchanging, working exactly the same as the regular switch. This feature answers the question of whether the POE switch can work with non-PoE devices such as PC computers or not. The answer is Yes, The PoE Switch will function as non-POE while the edge devices don’t support PoE.
The most popular PoE standard is IEE802.3af/at, also name PoE/PoE+. The PoE supply 14.4V and PoE+ can provide 30W PoE Power. Both POE/PoE+ use half of the twisted pairs to transmit the power. The power budget depends on lower standard in the system. Even the PoE Switch is PoE+, the power output will set PoE to (14.4W) while the edge device is PoE (IEEE802.3af). There is a power handshake between the PoE Switch and the PoE edge device.
Centralize PoE Power
The PoE Power system is the centralized powered solution. The power comes from the same PoE Switch and reaches each of the PoE IP devices. It is easier to manage to power, even adding UPS to backup the power becomes possible now. However, the PoE is limited to 100 meters, which means the power diameter has to be smaller than 100 meters. Is there any solution to expand the POE network?
We will need to deal with both data and power while we try to expand the PoE Network. The data seems to be easy, We know we can use topology to expand the RJ45 ports. Adding a switch to the network can create extra RJ45 ports. The power is a tricky thing. Unless there are power sources present next to the new switch, we will have sent the power from another PoE Switch at the center. There is always power loss during the transmission. The longer the distance, the more power loss will be. PoE+ only output 30W power while It will drop down to 25.5W in 100 meters.
New PoE Standard – 95W PoE++
Thanks to the IEEE802.3bt (aka PoE++), the new PoE standard can output 95W maximum power. All four twisted pairs have been employed to send the power. The power budget at the edge is set to 72W. It is about three times the PoE budget than PoE+. With such high power budget, some of the applications become possible, we can use the PoE++ to power all-in-one cameras, POS, access control, etc. Moreover, we can make use of such high power to expand the PoE Network.
Expand both distance and PoE ports – PoE Powered Switch
There is a hybrid form of PoE device name POE powered switch. We know the PSE provides the power and data to edge devices such as PoE switch, PoE injector, and PoE NVR. The PD is your edge device such as PoE IP camera, access point, VoIP. We can consider the PoE-powered switch work for both PSE and PD. One of the ports can receive the power from the PoE Switch at the center. In this perspective, the powered power switch belongs to PD, the same as the IP camera. However, the rest of the ports allows PoE Power to pass through to reach the edge device. In this way, it belongs to PSE too. The PoE power switch is not a new concept. However, the whole system may not useful while the POE budget is limited to 25.5W (PoE+). With PoE++, the maximum power budget is 71W which is enough to supply multiple IP devices at the edge. The maximum distance between POE powered switch and the edge is another 100 meters. Now the radius has expanded to 200 meters with multiple PoE ports.
While working with PoE powered switch, it is better to use IEEE802.3bt high power PoE Switch or PoE injector at the back-end. The PoE++ Power supply equipment can output 95W high power. All 4 twisted pair has been used to transport the power.
Cable is matter – Pure Copper
The cable is critical during expanding the PoE network. There is always power loss in the PoE system. The power will loss and convert to heat during the transmission. The longer the distance, the more power loss will be. The higher the power consumption, the more power loss too. While PoE expanding the PoE network, always Pick the pure copper Ethernet cable. The Copper clad aluminum (CCA) cable offers a cost-effective replacement for solid copper cable, but with much higher DC resistance than copper, It causes higher power loss inline and converts to the heat. The consequence is you may don’t have enough power at the edge.
Virtual LAN
While the PoE Network being expanding using the PoE powered switch, You may need to separate the network for traffic control, QoS or security. The L2 or L2+ PoE Switch support VLAN (virtual LAN) which can assign the different subnet to each of PoE powered switch. The routing table and DHCP are necessary for VLAN. Once the PoE-powered switch has been separated, you can have a different network configuration for each subnet domain.
