Benefits of fiber in the access network

The speeds of fiber optic and copper cables are both limited by length, but copper is much more sharply limited in this respect. For example, gigabit Ethernet runs over relatively economical category 5e, category 6, or augmented category 6 unshielded twisted pair copper cabling but only to 100 meters. However, over the right kind of fiber, gigabit ethernet can easily reach distances of tens of kilometers.

Even in the commercial world, most computers have copper communication cables. But these cables are short, typically tens of meters. Most metropolitan network links (e.g., those based on telephone or cable television services) are several kilometers long, in the range where fiber significantly outperforms copper. Replacing at least part of these links with fiber shortens the remaining copper segments and allows them to run much faster.

Fiber configurations that bring fiber right into the building can offer the highest speeds since the remaining segments can use standard Ethernet or coaxial cable. Fiber configurations that transition to copper in a street cabinet are generally too far from the users for standard Ethernet configurations over existing copper cabling. They generally use VDSL at (downstream) speeds of several tens of megabits/sec.

Fiber is often said to be 'future proof' because the speed of the broadband connection is usually limited by the terminal equipment rather than the fiber itself, permitting at least some speed improvements by equipment upgrades before the fiber itself must be upgraded.

September 23, 2011

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