An optical fiber is a thin strand of glass — sometimes plastic — that guides light from one end to the other. Because the light stays inside the core, the signal travels with very low loss and is immune to electrical interference.
Compared with copper, a single fiber carries far more bandwidth over longer distances. That is why access networks, metro rings and data centers are built on fiber, and why operators move from copper access to FTTX architectures.
In an FTTX network the fiber runs from the central office or cabinet toward the subscriber. Microduct and micro cable make it possible to install this last section quickly, and to add or replace cables later by blowing them through the existing duct.