PoE and the upcoming IEEE802.3bt standard

Further to our last PoE Tech Note, this brief tech note discusses the current situation with PoE above 30W (or the IEEE802.3at standard).

Although there are many IP cameras requiring greater than 30W, there is no current standard for this. However, PoE++ is being ratified (perhaps late 2017) and will be known as IEEE802.3bt.

How will IEEEE802.3bt work?

IEEE802.3bt will support power over 4 pairs as well as single or dual signature PD operation. While PDs have operated with a single signature for PoE up to 30W, the new standard will also allow for dual signature detection where a PD derives power from two PSEs.

Currently all PoE++ implementations are flying in the dark to some extent: OSD has come across a number of different interpretations which need to be resolved, almost on a case by case basis.

OSD Approach to PoE++

OSD will continue to work with its customers in the supply of PoE operating at >30W and can support dual signature if required.

OSD currently uses Linear Technology chipsets which are widely accepted by most PDs.

OSD will offer IEEE802.3bt when it is ratified and this will include single and dual signature detection.


The OSD2153P is an Industrial PoE++ Gigabit Ethernet Media Converter which supports up to 60W PoE and can operate at 100Mbps or 1000Mbps over fiber with Link Loss Forwarding for remote fault management. The OSD2153P will operate at temperatures up to 75degC with 60W of PoE. Click here for more info.



The OSD2254P is an Industrial Self-Configuring Redundant Ring Gigabit PoE++ Ethernet Switch. The OSD2254P has four fixed copper ports all supporting up to 60W PoE each as well as two 100/1000BaseX SFP ports. The OSD2254P will operate up to 75degC with 240W of PoE. Click here for more info.OSD2254P

Power over Ethernet (PoE)

PoE has emerged as a popular technology that provides power and data to network devices on the same Ethernet cable.

All Powered Devices (PDs), including security network cameras, wireless access points (WAPs), building automation and control systems, and voice-over-IP phones receive the electrical power on the Ethernet cable from a network switch or power injector which are known as Power Sourcing Equipment (PSE). Only the PSE is connected to a power supply.

Why PoE?

PoE converges the electric power and communication control network onto a single infrastructure.

PoE is safe; it doesn’t require a dedicated mains power supply connection for end devices, which also reduces the total installation cost.

PoE switches provide clean, stable, reliable DC power.

Ethernet is a global harmonized standard and IEEE has been standardising PoE to reduce the likelihood of compatibility issues. Customers should be able to use the same products anywhere on the planet.

IEEE Standards

IEEE802.3af specifies output of 15.4W

IEEE802.3at specifies output of 25.4W

IEEE 802.3af and IEEE802.3at standard support two alternatives for power injection

  • Alternative A, where power is supplied via the center taps of the coupling transformers on data pairs 1/2 and 3/6.
  • Alternative B, where power is transmitted over pairs 4/5 and 7/8

Network elements compatible only with IEEE802.3af are classified as Type 1, and elements compatible with IEEE802.3at are listed as Type 2.

  • Type 1 (over two pairs) – The PSE can supply a maximum of 15.4 W over a voltage range of 44 to 57 VDC using Category 3 cabling or better.
  • Type 2 – The PSE can supply 30 W (over two pairs)

OSD products are designed to be compatible with Type 1 and Type 2.

Future of PoE

PoE++ = 60W up to 100W

PSE will supply power over all four data pairs.

Upcoming new standard IEEE 802.3bt possible classifications:

Type 3 (over four pairs) – The PSE can supply 40W to 60W over a voltage range 47-57VDC

Type 4 (over four pairs) – The PSE can supply 75W to 90W over a voltage range 47-57VDC

Why do we need this much power?

IP cameras with PTZ, heaters and blowers, and dynamic IR may require up to 95W PoE

Industrial lighting systems may require up to 90W.

Telecommunications Base Stations may require up to 75W PoE.

Important Note

  1. As convenient as PoE is, with products needing 60 to 100W of PoE, a power supply is still required which will support these high powers and the power supply will be much larger than the PSE in some situations.
  2. Until there is a ratified standard for PoE above 25.4W, care should be taken when using power above 25.4W as different manufacturers of Power Sourcing Equipment (PSE) and Powered Devices (PD) devices may have slight;y approaches to implementation of PoE++. Bench testing is recommended prior to site installation.

Future OSD PoE Products

90W PoE++

Media Converter – OSD2153HP

Ethernet Switches –

  • 6 Port OSD2251HP
  • 8 Port OSD2254HP
  • 10 Port OSD2258HP

Telco Media Converter – OSD2175HP