Glossary of words and terms used in fibre optic lighting projects.


PMMA - this is the material from which plastic (polymer) optical fibre is made. Optical fibre can also be made from glass but this is not so suitable for domestic fibre optic lighting projects and certainly not for DIY projects.

Common end or common end ferrule - this is the interface between the fibre and the light source. The common end slides into the "optical port" at the front of the light source and ensures that the input ends of the fibres are correctly positioned in front of the LED inside the light source. The common end usually consists of two parts - the aluminium ferrule and a plastic cable gland. The common end is occasionally referred to as a "fibre head".

Dip switches - a row of little switches on the casing of a light source. By changing the position of the switches in different combinations you can select specific settings on the light source - such as twinkle speed, remote control enable/disable etc.

Home Cinema terms:

Bulkhead - a feature around the perimeter of a room, very popular in home cinemas. The bulkhead consists of a shelf or box feature which lowers the ceiling at the wall, resulting in the ceiling above appearing to be raised by comparison. This is described as a coffered ceiling since the space within the bulkhead is enclosed or boxed in. The flat surface of the bulkhead can provide a handy mounting surface for downlights or speakers, while the concealed space above the bulkhead can be used to conceal the projector, cabling, LED tape and fibre optic light sources.


Raft - a lowered area of ceiling - such as an array of our Infinity panels - which is suspended beneath the original ceiling level. Outward facing LED tape can be concealed above this to create a secondary lighting feature.

Fibre diameter - the diameter or thickness of an optical fibre determines its light carrying capacity. A thicker fibre will produce a brighter point of light than a thin one. As the fibre diameter increases the flexibility of the fibre decreases and with pmma fibre we recommend 2.5mm as the maximum useful diameter. Cheap inferior grades of fibre tend to be brittle and prone to snapping.

Where you need greater diameter than 2.5mm we'd recommend that you use multiples of fibres bundled together - typically 0.75mm fibres. In star ceilings you should aim to use combinations of diameters to create brighter and dimmer stars.

Attenuation - as light travels along the fibre some of it is lost through the side and some lost because of impurities in the transparent acrylic material. At Starscape we use excellent quality of fibre which is suitable for lengths of approaching 20 metres. As a rule of thumb you may lose 2% of light intensity per metre, but in many applications - such as star ceilings - this is not a problem, and you can compensate, if necessary, by using a brighter light source.

Colour shift - as white light travels along the fibre it gradually loses intensity (attenuation), and because this affects different frequencies of light at different rates the white light gradually starts to take on greenish hues. With the excellent fibre stocked by Starscape this shouldn't be a problem on fibre runs of less than perhaps 18 metres. On inferior grades of fibre colour shift can be observed over very short distances.

Colour Wheel - a disk of pie-segment-shaped coloured glass filter elements which modifies the colour of the optical fibres. The wheel is driven by an electric motor and mounted inside the light source in such a way that the light from the LED passes through the colour filters before entering the fibres. Typically, a colour wheel has a clear segment so that white light can be selected as well as colours. Simple light sources have one motor, allowing you to fit either a colour wheel or a twinkle wheel. More sophisticated light sources may have two motors driving overlapping twinkle and colour wheels so that colour and twinkle effects can be shown simultaneously. Colour wheels are gradually being phased out in favour of multi-coloured LEDs. See twinkle wheel.

Twinkle Wheel - An aluminium disk with holes or slits in it which creates twinkling effects in fibre optic star ceilings. The wheel is driven by an electric motor and mounted inside the light source in such a way that the light from the LED passes through the wheel before entering the optical fibres. The metal parts of the wheel block part of the light as the wheel rotates so that the brightness of the light entering each fibre is constantly varying and this results in the twinkle effect at the end of the fibre. The speed of the motor which drives the twinkle wheel can be varied in some light sources, allowing the user to select the effect which they most like. See colour wheel.

Tail - Individual optical fibres are sometimes referred to as "tails", but at Starscape we usually reserve this term for sheathed bundles of fibre. This may be the transparent sheathing of sparkle fibre or the black sheathing used in our Infinity system or our crystal end fitting kits. In our sparkle fibre there are usually 3 x 0.75mm cracked fibres within the transparent sheathing, while the Infinity tail has 100 mixed diameter fibres within its black sheathing. The tails used to carry light to our crystal fittings or accent lights have 10 fibres.

Harness - As soon as you fit a common end ferrule to a single fibre or a collection of fibres this assembly - which is ready to plug into the optical port of the light source - is referred to as a harness. It may consist of a single fibre or many hundreds of fibres. The fibres within a harness may be of a range of different diameters and cut to different lengths. Our DIY kits are normally supplied with a fibre harness, but in some projects it may suit the customer better to take loose fibre, or fibre on the spool and then fit the common end himself/herself.

Light Source - Sometimes called a light engine or (incorrectly) a driver, the light source is essentially a lamp designed specifically to illuminate optical fibres. The light source is an enclosure which contains the lamp - usually an LED these days - and other electrical and mechanical components, depending on the sophistication of the unit. Older models used halogen bulbs or metal halide bulbs, but the newer LED-based units tend to be smaller, cooler and quieter in operation, more economical to run and require less maintenance.

Light sources vary hugely in terms of size, features and cost. The simplest ones are tiny and produce just white light with no twinkle effects. More sophisticated units can twinkle, mix hundreds of colour shades, dim, shimmer and strobe, and they can be integrated within home automation/smart lighting systems using DMX technology.

DMX - a lighting control protocol or standard which allows light sources to receive instructions from a home automation system or standalone DMX controller. Light sources with DMX functionality offer much more precise control over parameters such as colour change, colour shade, speed of colour change, twinkle effects, dimming, strobing and shimmering. If you don't have a home automation system then inexpensive standalone DMX controllers are available, and it's also possible to control a light source using open source (free) DMX software on a PC. The controller is connected to the light source by DMX cable, and if there are multiple light sources in an installation they are daisy-chained together using DMX cable.

Ferrule - a metal tube, usually brass, steel or aluminium, at the end of a fibre tail. This may be the big common end ferrule at the input end of a harness, or a smaller ferrule at the output end of an Infinity tail or the thinner tails used with our crystal end fittings. The ferrule gathers a bundle of fibres together to connect to some other component and the exposed fibre ends in the ferrule are polished to ensure optimum light transmission.

Optical port - The circular opening at the front of a light source into which the common end ferrule is inserted. Although there are some common standards, not all light sources have the same size optical port. The larger the port, the more fibres can be accommodated within a harness used with that light source. Some light sources have two optical ports, each with its own LED, so as to double the capacity of the unit.

Remote control - self-explanatory really, but the remotes used with our light sources use radio frequency rather than infra red. So, they don't need line of sight to the light source. The functions of the remote control vary from one light source to another.

Dimming - the ability to increase or decrease the brightness of a light source. Most are dimmed via their remote control or via DMX. Dimming via a standard wallplate dimmer is uncommon, but available with more expensive light sources.

Solid core light guide - a type of fibre based on a softer material than ordinary pmma. This makes it far more flexible, and thus available as single strands in much larger diameters (more than 20mm), but it performs less well optically than pmma so can not project light over the same distance as pmma. It is available in end-glow and side-glow versions.

End-glow fibre - standard optical fibre designed to carry light from one end - the light source - to the other. If you cut the end off a fibre the light will emerge from the new end.

Side-glow fibre - optical fibre which has been optimised to display light leaking from its side so as to create linear lighting features. Because the light is leaking from the side of the fibre at a higher rate it projects light less far than end-glow fibre, and you have to factor this in to your design. Side-glow effects are subtle and work best where ambient light levels are low.

Sparkle fibre - a class of side-glow fibre in which the cladding of the pmma fibre has been nicked or cracked during manufacture to create tiny "windows" through which light can escape. The result is a general background glow of side-glow effect with pin-pricks of very bright light interspersed along its length. The closer the cracks the more impressive the effect, but the more quickly it diminishes over distance. So sparkle fibre can be manufactured to work best over short distances or longer distances by varying the spacing or pitch between the cracks. At Starscape we normally stock variants designed for lengths of up to around 3-4 metres and lengths of around 10 metres.

Cracked fibre - see sparkle fibre

Cladding - not be be confused with sheathing. Fibre optics work as the result of transparent materials having different refractive indices. When you put a stick into clear water it appears to bend, and this is because the refractive index of air is different to that of water. Similarly, in an optical fibre the core acrylic material has a higher refractive index than the very thin layer of cladding, and most of the light which is introduced at the light source end is reflected back into the fibre, rather than escaping through the side. The cladding can be cracked during manufacture to create sparkle fibre, or you can distress the cladding to allow more light to escape from selected areas of the fibre. If you do this too much of course the light won't flow past the damaged area, so it's best to limit this type of damage to the end of the fibre.


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Links to the latest projects:

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