When a PoE Switch is Not Enough

?

Power over Ethernet (PoE) was invented in 1997 by PowerDsine. By introducing the first Power Source Equipment (PSE) semiconductor, switch manufacturers were able to add power onto an ethernet cable which would be taken off the cable by the Powered Device (PD) semiconductor also introduced by PowerDsine.? However, in 1997, there were no switch manufacturers that incorporated PSE ICs in their switches, routers, gateways or other similar devices. So, in 1998, PowerDsine introduced the first midspan, also known as an injector.

The midspan is a device which comes after the switch with an input port for an ethernet cable containing data and an second output port for an ethernet cable which contains data combined with the power. It is easy to see why these devices were popular in the early days of PoE; however, are they really needed today?

Most every switch manufacturer today offers a switch option that provides PoE.? And yet today, PowerDsine, which became the Microchip Power over Ethernet Business Unit still offers a full line of indoor and outdoor PoE midspans.? To better understand why, it is important to understand the network landscape.

Most networks today do not provide PoE.? Only 20% of installed switches are PoE enabled.? Therefore, as devices such as IP Phones, IP Cameras, and Wireless Access Points are added to existing networks, they will require power. The easiest and most cost-efficient way to add power to an existing network is to install a PoE midspan.?

Even of the networks being deployed today, only 50% are choosing to install switches that can provide PoE. When the need arises for PoE power for networks with non-PoE switches, the midspan is the best way to provide supplemental power on ports where needed. And demand for that PoE power is increasing.

Since the beginning, the most popular devices to be powered by PoE were IP Phones, IP Cameras, and Wireless Access Points. PoE was originally developed at the request of an IP Phone manufacturer who wanted to provide power to their IP Phone the same way a wired phone gets it power, through the connection itself.? Today, there are hundreds of devices that can be powered by PoE, and the list grows every day.

PoE is becoming more popular every day.? It is safe power because the PSE will only put power on the line when a device requests power. There is no difference in installing it in Japan than in the US; all ethernet cables RJ45 connectors. ?The National Electric Code defines PoE as Class 2 power which does not require an electrician nor conduit to install; thus, it is easier and much less expensive to install or change.? That is why many device manufacturers are choosing to power their devices via PoE.

Today you can find radios, lights, window shade motors, thermostats, displays, printers, sensors, kiosks, televisions, clocks, intercoms, point of sale systems, security access systems, control systems, and many, many more all powered by PoE. And with the introduction of Class 4 Fault Managed Power by the National Electric code, the demand for PoE powered devices is increasing as PoE becomes the delivery method of choice for the next generation. ?If you want to learn more about Class 4 Fault Managed power and it’s impact, see my article on LinkedIn “The Future of Powering the World.” https://www.dhirubhai.net/pulse/future-powering-world-alan-zwiren/

Even as PoE switches become more popular, midspans will still be needed to supplement the switches. Most PoE switches come with a power budget of how much power is available to provide power over all the ports. Because larger power supplies cost significantly more and require more space, rarely does a switch, especially the larger switches with 24 or 48 ports have enough budget to supply power on all ports. So even PoE switches sometimes need supplemental power provided by a midspan.

And manufacturers who make these PoE powered devices realize that installations may require supplemental PoE power. Many manufacturers of these devices offer an optional or bundled PoE midspan as a powering option to ensure the device will have the required power. Since the manufacturers of these devices are not experienced in designing and building PoE midspans, which are highly regulated, they turn to specialists such as Microchip’s Power over Ethernet Business Unit to supply them devices for the option or bundle.

It is clear the demand for Power over Ethernet is growing, and as it grows, so will the demand for PoE switches. However, the PoE Switch does not address all the growing demand, and midspans will continue to be an important part of the topology for many years to come.

?