Optical fibres

Fibre Types

Roblon Lighting Division uses 2 types of material for fiber light cables: PMMA (PolyMethylMethAcrylate) and Glass.

 

From these materials three types of fiber light cables are made:

1. PMMA endlight

2. PMMA sidelight

3. Glass endlight

 

PMMA fiber cables are built of "raw fibers" with a diameter of 0.75 mm or 1 mm. Standard dimensions are from 1 mm to 10 mm. A 6 mm PMMA fiber cable consists of 50 "raw fibers", each 0.75 mm.

 

Glass fiber cables are built of "raw fibers" fine as a hair, with a diameter of 50m . Standard dimensions are from 1 mm to 6 mm. A 6 mm glass fiber cable is built from 11000 "raw fibers", each 50m .

 

 

Colour Temperature

The colour temperature changes according to the length of the fiber, and therefore it is important to be aware of the colour from PMMA and glass fiber cables respectively. Installations with strict demands on colour temperature therefore need either shorter fiber cables and / or more light generators. Glass fiber cables provide less, but "warmer" light than PMMA.

Principle drawing. The colour temperature (Kelvin) changes according to the length of the fiber cable. The colour temperature is decreased by glass(G) and increased by PMMA (P).

 

The figure shows the light temperature (Kelvin) at various lengths of the fiber cable. The values are based on halogen light sources.

 

 

Light Transmission

In a fiber light system there is a contact loss between light source and fibers, and a transmission loss inside the fiber it self. The longer the fiber, the bigger the loss. As the light from one 75 watt light generator is distributed to 9 light points, for instance, it goes without saying that the light intensity from each point is relatively small.

 Light transmission loss inside the fiber. PMMA (P) and glass (G). The ratio between the light led into fiber and the light emitted.

 

Loss from the lighting system. PMMA (P) and glass (G). The ratio between the light led towards the fibers from the light source, and the light that emits the fibers. The values are based on a 100% filled polyconnector!

 

When fiber light grows more and more popular in spite of this loss it is because of its high degree of flexibility and the facilitated maintenance. Furthermore, contrary to traditional light, which creates heat, the fiber light can be placed close to the objects, as there is no heat transmission.

 

Using fiber light the "distance law of light" is utilised, meaning that the light intensity is 4-doubled when the distance between light and object is halved.

 

 

Light intensity decreases by the distance of the power of two.

 

However, by using fiber light fittings a relatively large quantity of light is obtainable. When the light comes from the same light source and is distributed to a varying number of fiber ends, shadows can be omitted or created as required, and the lighting is visible from many angles and directions. This yields the light designer a high degree of freedom in his planning.

 

When dimensioning fiber light systems it is essential to respect the limitations connected to fiber light, for instance fiber lengths.

 

Recommendable max. fiber lengths:

Light generator

Fiber *

Fiber

mm

Max. L

m

Application

42 W

E

1/2-6

3-6/2.5-3

Star ceilings (3-6 m) and vitrines (max 2.5-3 m)

75 W 9

E

2-6

9-12

Lighting, decorative light, working light

75 W 28

E

4.5/6

6-8

Room lighting, decorative light, large star ceilings

150 W CDM SA-R

E

4.5-6

16-18

Outdoor light, facades

150 W CDM-T

E

3-6

10-13

Lighting, decorative light, large star ceilings

75 W 9

S

>4.5

12-22

Decorative, length depending on ambient light level

75 W 9

S

4.5

12-15

Recommended if very low ambient light (cinemas)

75 W 28

S

>4.5

9-14

Recommended where low ambient light

75 W 28

S

4.5

7-12

Recommended if very low ambient light (cinemas)

150 W CDM-T

S

>4.5

12-18

Decorative, length depending on ambient light

150 CDM-T

S

4.5

10-16

Decorative, length depending on ambient light

150 W CDM SA-R

S

4.5

15-20

Decorative, length depending on ambient light

150 W CDM SA-R

S

>4.5

25-35

Decorative, longest fibers if coloured light

*) E = Endlight, S = Sidelight

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