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ATTENUATION
Fibre is produced to a very high optical quality but some light
will be absorbed along its length. The reduction in light with
fibre length is known as attenuation. Attenuation will increase
as the fibre length increases.
CLADDING
This may refer to either:
The material with a low refractive index that forms the outer
layer of an optical fibre.
An outer layer providing mechanical protection for each tail
and harness - see sheathing.
COLOUR SHIFT
The attenuation of light in a fibre will vary across the spectrum
depending on the fibre material. This means that the spectral
distribution at the emitter will not be the same as at the light
source. This change is the colour shift. The degree of colour
shift will increase with the fibre length.
COMMON END
The end of the harness attached to the light source, where light
is inserted into the fibre. The individual fibres are bonded
together, either with resin or heat treatment, and the ends then
polished to ensure optical clarity and low insertion loss.
EMITTER
The point in a fibre optic system where light is usefully emitted.
This may be from an end fitting, a termination, or from a length
of side emission fibre.
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END FITTINGS
These are attached to the end of most fibre optic tails. Their
role is to secure and protect the end of each tail, and to guide
and determine the characteristics of the light output.
FERRULE
See Termination.
HARNESS
The complete fibre assembly attached to an individual light source.
May also be known as a 'loom'.
LIGHT SOURCE
The light source for a fibre optic system. The light source will
contain a lamp and an optical system to focus the light onto
the common end of the harness. It may also contain filters for
infrared and UV light, and devices such as colour wheels for
special effects. May also be known as the source or projector.
MINIMUM BEND RADIUS
The minimum radius to which a given fibre optic product may be
bent without damaging the fibres or disrupting the continuity
of its lighted path.
OPTICAL FIBRE
A fibre, drawn from an optically transparent material, usually
consisting of a high refractive index core with a low refractive
index cladding. The fibre is flexible, while allowing the transmission
of light along its length due to total internal reflection. Fibres
may be made of glass or a polymer.
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PROJECTOR
See Light Source.
REFRACTION
The change in the direction of a light ray when passing from
one medium into another of a different refractive index, e.g.
when light passes from air into water.
SHEATHING
A tough material that surrounds the fibres in a harness, to protect
them from mechanical damage.
SlDE EMISSION FIBRE
An optical fibre designed to allow the gradual emission of light
along its length.
SOURCE
See Light Source.
TAIL
The length of fibre from the common end to a termination is known
as a tail. There will usually be a number of these in each harness.
TERMINATION
The end of the tail where light is emitted from the fibre. The
individual fibres are bonded together, either with resin or heat
treatment, and the ends then polished to ensure optical clarity
and low exit loss. The termination will usually include a screw
thread or other method of attaching an end fitting.
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