The Fiber Connection

Two Technologies Team Up to Go the Distance - Tuesday, September 13, 2011

There’s no doubt that Power over Ethernet (PoE) is a very useful technology that offers tremendous benefits to designers, installers and end users. The ability to power devices and equipment over twisted-pair copper cabling eliminates the cost associated with delivering AC power to every device—especially in locations where providing access to AC power is complicated. That’s precisely why we’re seeing wireless access points, phones, clocks, surveillance cameras and other devices powered by DC power over the same copper cabling that transmits data packets across the network. Now the IEEE 802.3at-2009 PoE Plus standard delivers even more power—up to 24.5 Watts. This has opened the door for a wider range of PoE-enabled devices with higher power requirements, including laptops, pan-tilt-zoom cameras, routers, videophones and a variety of industrial controllers.

But PoE has one major problem. As an Ethernet protocol, twisted-pair cable from the patch panel in the telecommunications room to the device is limited to a 100-meter distance—just 28 feet longer than a football field. That’s just fine for the office phones, most of the wireless access points and a few other devices, but what do I do about that security camera located out in the parking lot, or the wireless access point in the warehouse? And what about that critical access card reader at the main gate or the phone in the security booth? With the global need for increased security and cameras located throughout large public spaces like airports, arenas and campuses, the 100-meter distance limitation is just that—a limitation.

When it comes to connecting devices located farther than 100 meters to the network for data transmission, there is another popular technology—optical fiber cabling. And if you know anything about fiber, you know that it is dielectric and carries data as light pulses. That means it can’t deliver PoE. It does however offer several other benefits like high bandwidth, small size and weight, low loss and signal security. Rather than giving up on PoE for devices located farther than 100 meters from the closet, what better way to power these remote devices than by combining two great technologies—PoE and fiber.

The combination of a media converter and PoE extender in one device is making this all possible. Media converters have been around for decades and are used to convert various types of cabling media—the most common being fiber to copper and vice versa. By combining media converters and PoE extenders in a single device, a hybrid cable can be installed from the telecommunications room (with fiber for data and copper for power) and connect to the remote media converter/PoE device. At the device, the optical signal is converted back to an IEEE 802.3 PoE- or PoE plus-compliant copper data outlet, from which unshielded, twisted-pair data cable can extend the 100 meters to the actual IP device. When all is said and done, this solution allows a PoE device to be located up to 1,100 meters from the closet—or about 13 football fields away.

Power over Ethernet, PoE, media converters, fiber optics, IP devices, security networks