What is PoE ? I have a PoE device and how do we integrate it ?

PoE stands for power over Ethernet where the same cable is used for carrying both data and DC power to power the equipment. In normal case data and power cable is separate and you may have situation where you need an IP device to be mounted but have no power outlet nearby (like CCTV camera locations).  Typically Wireless AP and IP camera (incl. CCTV) are the devices that are PoE enabled and many homes will need one or both. Then there are others like VoIP phones, Video Door phones etc that may be powered via PoE. PoE is especially useful for ceiling mounting devices (in false ceiling) or a separate housing near the ceiling. Many small switches used for extending ports are also powered by PoE

The main PoE standards comprise IEEE 802.3af (PoE) amd 802.3at (PoE+) which can supply 15.4 and 30.8W respectively over Ethernet cable to any device. Typically all IP cameras are PoE while many high end Wifi AP (with multiple antenna) may need PoE+. 

To power and use these devices the LAN cable must run from the point of device location to a star point, just as any other data point. At the star point you either need to connect to on of:

(1) PoE/PoE+ Injector per PoE port, the data port of which is connected to LAN switch and Power adapter cable to an AC plug source.
(2) PoE/PoE+ Mid-span Injector - This is an array of PoE injectors (used especially in CCTV applications) to provide a lot of PoE ports without creating the cabling mess that accompanies each POE injector (3 cables). Generally these are rack mount devices.  They may come in 8, 16, 24 or 48 port capacities mirroring the ports typical;ly found on LAN switches.

(3) Separate PoE/PoE+ switch one port of which is connected to your LAN switch/router and all other ports provide active (auto-sensing) PoE output

You may familiarize yourself with these devices through the following video:

NOTE: It is extremely important to ensure that the Power grade of PoE device (i.e PoE or PoE+) must match the capability  of injector and switch, otherwise it may fail to provide sufficient power to power the equipment. You should also ensure that the injector and device support same standard. For eg., 24V and 48V non-802.3af compliant injectors are also used by some vendors like Ubiquiti and Cisco for their APs. Similarly there would be other incompatibilities like fast Ethernet or gigabit Ethernet power injection, active or passive injection etc.


- Suman Kumar Luthra @ APRC-P3 Telecom Sub-Committee