A luminaire for use with power over an Ethernet emergency lighting is disclosed. The luminaire includes a rechargeable battery pack, an emergency backup LED driver, a normal lighting LED driver and an LED lamp. The luminaire also includes a power loss monitor that monitors the presence of normal lighting power present on a power over Ethernet link, and connects the emergency backup LED driver to the LED lamp through a relaying device in the event of a loss of normal lighting power. Furthermore, a method of detecting the power loss in a POE link segment is provided, wherein the method includes detecting a differential DC voltage between a first conductor in a first data pair on the POE link segment and a second conductor in a second data pair on the same POE link segment.