Date: Thu, 18 Dec 1997 02:47:47 GMT Server: BESTWWWD/1.0 MIME-version: 1.0 Content-type: text/html Content-length: 4972 Last-modified: Sat, 01 Feb 1997 20:51:04 GMT Fiberstars' Glossary


Fiber Optic Lighting GLOSSARY


Acceptance angle: the maximum beam spread of light (measured from the fiber's axis) that will enter one end of the fiber.

Attenuation: a measurement of how much reduction in light is experienced per unit length of fiber. It is measured in decibels per foot.

BritePak: the newest patented form of side-emitting fiber optic tubing wherein fiber optic strands are bundled into groups, then twisted and drawn through an outer jacket via a proprietary machine tool. The BritePak method allows more fiber optic strands to be packed into a given diameter of tubing, and facilitates lumen output due to both the greater density and the bundling/twisting.

Color rendering index: a measure of the degree of color shift objects undergo when illuminated by the light source, as compared with the color of the same objects when illuminated by a reference light source of comparable color temperature. Incandescent light and North-sky daylight are both rated 100 on a numbering system ranging from 1 to 100. The higher the number, the "truer" the color of objects appear.

Fiber optic port or master ferrule: a metal or plastic connector attached to one end of a plastic fiber optic bundle, allowing it to be readily inserted into an illuminator for maximum light output. Porting of a fiber optic bundle can be done by the manufacturer before the illuminator and tubing are shipped to the installer or job site, or can be accomplished or modified in the field to suit changing job conditions.

Fiber optic tubing: clear, opaque or patterned PVC outer tubing available in differing diameters, and containing varying densities of fiber optic strands, to suit specific types of installations and designs. Often referred to as cabling.

Illuminator: the power unit for a fiber optic lighting system, containing the light source. Sometimes referred to as "the shoe box" since illuminators are generally rectangular shaped boxes, roughly comparable in size to a shoe box. Illuminators are constructed of lightweight, ventilated metal or high-impact plastic. They can be linked in tandem or series for powering large or complex fiber optic installations.

Large core fiber: a solid polymer fiber, up to 20mm in diameter, which is clad with a thin material having a lower refractive index to the core. Creates a light guide effect. Generally manufactured with a thermal set process to specific pre-set lengths.

Small core fiber: a solid polymer fiber, up to 2mm in diameter, which is clad with a thin material having a lower refractive index to the core. Creates a light guide effect. Can be extruded to any length, and remains flexible throughout a 20-year life.

Metal halide lamp: a high-intensity discharge lamp in which most of the light is produced from an arc in a mixture of metal halides and metallic gasses, such as mercury, operating slightly above normal atmospheric pressure.

Numerical aperture: the difference of refractive indexes of the core and the cladding determines the numerical aperture (NA) for the fiber. The NA is the acceptance angle for the fiber above which light can enter the core but will not be guided by the cladding. A smaller or larger NA does not necessarily mean better output, other factors such as angle modes have as much or more to do with output.

Refractive Index: refers to the angle at which light is "bent" on entry or exit, and is related to the speed of light in the material.

        








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