July 18, 2019

The Potential Perils of CAT5 and PoE

Most operators of WISP backhaul networks have had difficult experiences with Power over Ethernet (PoE) cabling solutions, affecting both the economics and operations of their networks. Today, Aviat Networks is recommending, with increasing frequency, a dual cable system: fiber to carry data at high speeds, and copper to carry DC power only. This solution offers significant advantages over CAT5 cabling, which carries both data and DC power over a single Ethernet cable.

The Way It Was

The challenges of CAT5/PoE systems fall into five main categories: cable distance limitations, capacity limitations, vulnerability to lightning and electrical issues, a critical need for precisely optimized connections, and the significant extra expense incurred in addressing the previous four challenges. The following are just a few of the specific issues operators have experienced:

• Ethernet extends only up to 100 meters (328 feet). So, an expensive addition, such as a network switch installed on the tower, is often necessary.
• The wire stranding of CAT5 cables are vulnerable to lightning strikes—foil and shields on the wires can be inadequate, and shields on network cables need to be grounded. Double-shielded cables with ground returns are an improvement, but they are expensive and hard to terminate, making precision craftsmanship critical.
• Surge protection is a necessary feature on the device and at the bottom of the tower. Most, if not all, users of this method have had radios and CAT5 cables hit by lightning and damaged or destroyed. Thus, extra money has to be spent on higher-quality CAT5 or CAT6 cables, and specialized tools and personnel—and the technology remains vulnerable.
• Limited capacity can be a waste of radio power since current radios can deliver up to 1.5 Gbit/sec capacity.

The Way It Can be

Dual-cable Fiber DC systems eliminate cable distance and capacity limitations, eliminate vulnerability to lightning and other electrical issues, eliminate the need for precisely optimized connections, and save operators the expense incurred in trying to address those challenges. Specific advantages include:

• Carries up to 10 Gbit/sec capacity
• Practically speaking: unlimited distance.
• Outdoor-rated fiber can’t be harmed by lightning.
• Power-only cables are easy to connect and ground.
• Dual-cable Fiber DC solutions can use the full 1.5 Gbit/sec capacity of current radios.

Conclusion

Operators who’ve never worked with fiber can get nervous considering it. Is it fragile? You don’t want to bend fiber, right? Installation must be a bear! Yes, fiber is physically different from CAT5. But the fears are unfounded. Newsflash! Fiber is essentially bend-proof. And if you’ve never installed it, take it from those who have: installation of fiber gives an experience like that of installing CAT5, as far as cable handling goes. When you add in the longer distance and lower vulnerability to lightning, all at a comparable cost, dual-cable Fiber DC is a solution with a great upside.

Aviat Networks recommends dual-cable Fiber DC solutions over PoE solutions in WISP backhaul and other critical networks using the WTM 4000. Don’t trust your backhaul systems to inadequate power schemes.