Term
Definition
Bend Loss
A form of increased attenuation caused by (a) having an optical fiber curved around a restrictive radius of curvature or (b) microbends caused by minute distortions in the fiber imposed by externally induced perturbations.
Bend Radius
Radius of curvature that a flat, round, fiber optic or metallic cable can bend without any adverse effects.
Breakout
The point at which a conductor or conductors are separated from a multi-conductor cable to complete circuits at various points along the main cable.
Buffer
A protective coating over an optical fiber.
Cladding
A low refractive index material that surrounds the core of an optical fiber causing the transmitted light to travel down the core and protects against surface contaminant scattering or a layer of metal applied over another. Cladding is often chosen to improve conductivity or to resist corrosion.
Core
The light conducting central portion of an optical fiber with a refractive index higher than that of the cladding. The center of a cable construction. Most often applies to a coaxial cable, where the core is the center conductor and the dielectric material applied to it.
Dispersion
The cause of bandwidth limitations in an optical fiber. Dispersion causes a broadening of input pulses along the length of the fiber. Two major types are (a) mode dispersion caused by differential optical path lengths in a multimode fiber, and (b) material dispersion caused by a differential delay of various wavelengths of light in a wave guide material.
FDDI
Fiber Distributed Data Interface.
Fiber
A single, separate optical transmission element characterized by core and cladding.
Fiber Optics
Light transmission through optical fibers for communication and signaling. A technology that transmits information as light pulses along a glass or plastic fiber. Optical fiber carries much more information than conventional copper wire and is generally not subject to interference. Most telephone company long-distance lines are optical fiber. See RUS 1755.900.
Fiber to the home (FTTH)
A technology that provides voice, data and video services from the phone company's branch office to local customers over an all-fiber optic link. Still in its infancy, FTTH technology is substantially more expensive and labor-intensive to install and maintain than competing technologies.
FTTC
Fiber-to-the-Curb.
Graded-Index
A type of optical fiber in which the refractive index of the core is in the form of a parabolic curve, decreasing toward the cladding. This type of fiber provides high bandwidth capabilities.
HFC
Hybrid Fiber/Coaxial.
Injection Laser Diode
Sometimes called the semiconductor diode. A laser in which the lasing occurs at the junction of n-type and p-type semiconductor materials.
Laser
A coherent source of light with a narrow beam and a narrow spectral bandwidth (about 2nm).
Light Emitting Diode (LED Source)
A semiconductor device that emits incoherent light formed by the P-N junction. Light intensity is roughly proportional to electrical current flow.
Mode
A single electromagnetic wave traveling in an optical fiber.
Numerical Aperture (NA)
A measure of the angular acceptance for a fiber. It is approximately the sine of the half-angle of the acceptance cone.
Optical Waveguide Fiber
A transparent filament of high refractive index core and low refractive index cladding that transmits light.
Photodetector (Receiver)
Converts light energy to electrical energy. The silicon photo diode is most commonly used for relatively fast speeds and good sensitivity in the 0.75 micron to 0.95 micron wavelength region. Avalanche photodiodes (APD) combine the detection of optical signals with internal amplification of photo-current. Internal gain is realized through avalanche multiplication of carriers in the junction region. The advantage in using an APD is its higher signal-to-noise ratio, especially at high bit rates.
Pin-diode
A photodetector used to convert optical signals to electrical signals in a receiver. See also Photodetector.
Receiver
An electronic package that converts light energy to electrical energy in a fiber optic system. Also refers to a unit that converts an RF signal to another type of signal (e.g. radio, television). See also Photodetector.
Refractive Index
The ratio of light velocity in a vacuum to its velocity in the transmitting medium.
RUS 1755.900 (aka PE90)
A specification for fiber optic cables currently in high demand by the telecommunications industry. Only a handful of U.S. manufacturers can produce fiber optic cables to this specification. Belden is one of them.
Single Mode Fiber
A fiber wave guide in which only one mode will propagate. The fiber has a very small core diameter of approximately 8 micro meters. It permits signal transmission at extremely high bandwidths and is generally used with laser diodes.
Skew Rays
A ray that does not intersect the fiber axis. Generally, a light ray that enters the fiber core at a very high angle.
SONET
Synchronous Optical Network.
Source
The device (usually LED or laser) used to convert an electrical information-carrying signal into a corresponding optical signal for transmission by an optical wave guide.
Spectral Bandwidth
The difference between wavelengths at which the radiant intensity of illumination is half its peak intensity.
Spectrum
Frequencies that exist in a continuous range and have a common characteristic. A spectrum may be inclusive of many spectrums (e.g., the electromagnetic radiation spectrum includes the light spectrum, radio spectrum, infrared spectrum, etc.).
Speed of Light ( c )
Approximately 2.998 x 10^8 meters per second.
Step-index Fiber
An optical fiber in which the core is of a uniform refractive index with a sharp decrease in the index of refraction at the core/cladding interface.
Transmitter
The electronic package that converts electrical energy to light energy in a fiber optic system. Also refers to equipment that generates RF or electrical signals for transmission through the air or space or over a transmissions line.