Power over Ethernet (PoE) has become the colloquial term used to describe any technology that allows an Ethernet device to transmit and receive data, as well as receive power over the same cabling. The benefits of using the same cable for both data and power are numerous. It allows power to be delivered to small devices without having an electrician wire new circuits or a transformer to convert ac to dc—also referred to as a wall wart. It can also reduce the weight and cost of deployments, and when using standardized technology, it ensures a high level of safety.
However, when it comes to how PoE works from a user’s standpoint, the general term “PoE” could actually represent any number of different, incompatible technologies, which has led to considerable market confusion. To help overcome this turmoil, the Ethernet Alliance, an industry forum that aims to advance and promote IEEE Ethernet standards, is launching a certification program that will enable manufacturers to complete certification requirements to earn a branded logo. The goal is to provide a simple and easy way for users to identify what PoE products will work with each other and promote interoperability in the marketplace.
Many different implementations of PoE have been used over the past 20 years. Generally speaking, the different forms of PoE can be placed into two categories: standardized and proprietary. To help put this into context, here’s a brief history of the technology itself and how it evolved.
The advent of PoE was most commonly referred to as “power injection.” These “power injectors” operated simply by providing power, either ac or dc current, on Ethernet cabling without any true intelligent protocol or safety considerations.