Low-Voltage Cabling Practice Test

Backbone distance is determined by how far the signal can travel without spreading or losing integrity. Single-mode optical fiber keeps light in a single propagation path, so there’s minimal modal dispersion and very low attenuation over long distances. That combination lets high-bandwidth signals travel tens or hundreds of kilometers, which is why it’s chosen for backbone links. Multimode fiber has multiple light paths that arrive at different times, causing dispersion that limits distance; older 50/62.5 multimode fiber has even shorter reach. Copper like 100-ohm UTP is limited by electrical losses and crosstalk, making it unsuitable for long backbone runs. So the fiber type that supports the greatest backbone distance is single-mode optical fiber.