Glossary

An electric current that flows in one direction and does not reverse direction, unlike alternating current (AC). Direct current also means a current whose polarity never changes.

Directly feeding a message into a voltage-controlled oscillator.

Twisted-pair wire used inside a building, usually two- or four-pair AWG 26.

A device that samples or tests data traveling in one direction only.

A broadening or spreading of light along the propagation path due to one or more factors within the medium (such as optical fiber) through which the light is traveling. There are three major types of dispersion: modal, material, and waveguide. Modal dispersion is caused by differential optical path lengths in a multimode fiber. Material dispersion is caused by a delay of various wavelengths of light in a waveguide material. Waveguide dispersion is caused by light traveling in both the core and cladding materials in single-mode fibers and interfering with the transmission of the signal in the core. If dispersion becomes too great, individual signal components can overlap one another or degrade the quality of the optical signal. Dispersion is one of the most common factors limiting the amount of data that can be carried in optical fiber and the distance the signal can travel while still being usable; therefore, dispersion is one of the limits on bandwidth on fiber-optic cables. It is also called pulse spreading because dispersion causes a broadening of the input pulses along the length of the fiber.

A single-mode optical fiber that has a low chromatic dispersion throughout the range between 1300nm and 1600nm.

Describes cases where the dispersion of a pulse rather than loss of amplitude limits the distance an optical signal can be carried in the fiber. If this is the case, the receiving system may not be able to receive the signal.

A single-mode fiber that has its zero dispersion wavelength at 1550nm, which corresponds to one of the fiber

A single-mode optical-fiber cable that has its zero dispersion wavelength at 1300nm. Often called conventional or unshifted fiber.

Any undesired change in a waveform or signal.

In fiber-optic cable, the limiting of performance because of the distortion of a signal.

A semiconductor laser specially designed to produce a narrow spectral output for long-distance fiber optic communications.

An optical fiber cable used

A basic element of a structured distribution system. The distribution subsystem is responsible for terminating equipment and running the cables between equipment and cross connects. Also called distribution frame subsystem.

A pair in a UTP cable that has been disturbed by some source of noise during cable testing.