Optical fiber (or
"fiber optic") refers to the medium and the technology associated with
the transmission of information as light pulses along a glass or plastic wire
or fiber. Optical fiber carries much more information than conventional copper
wire and is in general not subject to electromagnetic interference and the need
to retransmit signals. Most telephone company long-distance lines are now of optical
fiber.
Transmission on optical
fiber wire requires repeaters at distance intervals. The glass fiber requires
more protection within an outer cable than copper. For these reasons and because
the installation of any new wiring is labor-intensive, few communities yet have
optical fiber wires or cables from the phone company's branch office to local
customers (known as local loops).
Optical
fiber consists of a core, cladding, and a protective outer coating, which guide
light along the core by total internal reflection. The core, and the higher-refractive-index
cladding, are typically made of high-quality silica glass, though they can both
be made of plastic as well. An optical fiber can break if bent too sharply. Due
to the microscopic precision required to align the fiber cores, connecting two
optical fibers, whether done by fusion splicing or mechanical splicing, requires
special skills and interconnection technology.
Two
main categories of optical fiber used in fiber optic communications are multi-mode
optical fiber and single-mode optical fiber. Multimode fiber has a larger core
allowing less precise, cheaper transmitters and receivers to connect to it as
well as cheaper connectors