Some fiber really isn't

"Fiber optic," or plain "fiber," is a hot term in telecommunications. It refers to technology that moves electronic pulses through thin glass filament. That allows far more data, or bandwidth, to be carried in the same-sized pipe than with cables that use copper as a conduit.

Though various networks are described as being "fiber," Verizon FiOS is the only network we've rated that actually is all fiber, right up to the home. Most telecom networks, including AT&T U-verse, are hybrids of fiber and copper technology. That's largely because it's expensive to rip up lawns and sidewalks to lay down fiber all the way to every home.

Networks that aren't all fiber run fiber-optic cable to neighborhood distribution points and older, slower copper wiring or coaxial cable to each house. The result is akin to funneling traffic from an Interstate onto a two-lane road for the last mile of a journey. Speed and capacity can suffer, as our Ratings (available to subscribers) show. You might see a decline in Internet speeds or in the number of high-definition channels you can watch at the same time, among other things.

Last year, Time Warner Cable was criticized for inaccurately calling its hybrid system an "advanced fiber-optic network" when in fact it uses coaxial cable for the final stretch.