We all know that fiber cable doesn’t have the capability to deliver power. So how do optical network terminals (ONTs) in a POLAN provide power over Ethernet (PoE) for phones, wireless access points (WAPs) and other PoE-enabled devices?
One way is to power ONTs locally via an AC power outlet. But a power outlet may not always be available, especially for ONTs supporting WAPs located in the ceiling. That’s why the ability to deliver power over the same copper cable used for transmitting data is a highly valued capability of traditional switch-based LAN deployments.
The good news is that ONTs can also be powered remotely using a composite copper/fiber distribution cable with fiber for information transfer and copper conductors to deliver power. Here’s what to keep in mind if you choose this route …
More Power, Greater Distance
Composite copper/fiber cables come with a variety of copper conductor options. Only two copper conductors are technically required to deliver power to the ONT, but choosing a composite cable that includes a four-pair network cable can deliver more power over greater distances.
For example: A Category 6 cable with eight 23 AWG conductors can support PoE Type 1 applications (15W) to 371 meters; two 22 AWG conductors can only support the same amount of power to 128 meters.
Of even bigger concern is the growing number of Ethernet devices that need more power. Higher-power PoE Plus applications, like Type 2 at 30W and Type 3 at 60W, make it even more apparent that a composite copper/fiber cable including a Category 6 cable is the way to go.
Category 6 supports Type 2 PoE to 252 meters and Type 3 to 126 meters. Two 22 AWG conductors fall short at just 87 meters for Type 2 PoE and 44 meters for Type 3, which is highly impractical for POLAN deployments needing to deliver higher power. To adequately support PoE Type 3 using a two-conductor cable, conductor size would need to increase to 18 or 16 AWG, which is more expensive.
Not only does a composite copper/fiber cable that includes a Category 6 cable offer greater power and distance, but it also offers an insurance policy. Unlike a two-conductor cable, a Category 6 cable can provide network access for alternative protocols, such as traditional switch-based Ethernet.
Another consideration is the fiber in the composite cable. While only one singlemode fiber is required to connect to the ONT, a cable with a duplex fiber offers a higher level of redundancy. The duplex fiber can also support alternative protocols like traditional switch-based Ethernet, which requires a duplex fiber for transmitting and receiving data.
When supporting PoE via remote power in your POLAN, keep in mind that a composite copper/fiber cable with a duplex fiber and a Category 6 cable offers the greatest futureproofing capabilities. The fiber and copper can be terminated to a wall outlet and connected to the ONT via patch cords, or used for other purposes if ever the need arises.
Belden POLAN solutions include cable options for powering ONTs locally or remotely. To learn more, download our white paper, “How You Can Optimize Passive Optical LAN through Structured Cabling”. And to learn more about PoE in your POLAN, call 1.800.BELDEN.1 or visit www.belden.com.
Throughout his career Stephane has worked in the telecommunications industry; in R&D, product management, training and marketing. Since 2014, Stephane as Director Technology and Applications is focusing on technology roadmap and ideation, networking applications and trends, and standards engagement.