Sidelight fibers are available in a variety of different versions. Polymer optical sidelight fibers, SL-POF, are the preferred material technology due to their easy processability and mechanical robustness. The following remarks are therefore limited to SL-POF.
SL-POF sidelight fibers are roughly distinguished according to the manufacturing method:
-Extruded or drawn fibers
Drawn or extruded sidelight fibers are made from thermoplastic material in a similar way to the well-known POF endlight fibers. They are coated with a low refracting resin on the lateral surface. The thermoplastic material is often PMMA, thus these fibers behave mechanically and thermally similar to PMMA POF endlight fibers. The lateral radiation is realized by the resin or a roughened jacket surface. The SL-POF fiber attenuation is significantly higher compared to endlight fibers.
Variable diameters available
PMMA sidelight fibers are available in diameters from 0.25mm to 3mm and larger. Even a 3mm thick PMMA POF can only be bent with large radii. This means that larger diameters are not feasible in many applications. Compared to cast fibers, these fibers are low-priced.
If very thin SL-POFs with diameters of 0.5mm and less are used, they must be combined to form bundles of 3, 7, 19 or more individual fibers. This ensures an economically efficient coupling to the LED modules. The light ribbon in the photo above couples 19 fibers of 0.5mm diameter each to only one red and one green PowerLED module. The cost advantage of the inexpensive fiber material is put into perspective by the number of fibers and the packaging of these into a fiber ribbon in textile production.
– Casted fibers
Alternatively sidelight fibers can be fabricated in a reaction casting process by filling a suitable plastic tube with liquid plastic. The liquid plastic hardens and forms the core of the waveguide. Casted SLPOF are very flexible, depending on the material chosen for the core and tube material. Fibers for a small radius of a few mm can be filled e.g. with PUR (polyurethan). Casted fibers are available in core diameters from about 1mm to significantly above 6mm. The total diameter results from the waveguide core and twice the wall thickness of the tube. This results in an outer diameter of 2mm and more. The costly manufacturing process increases the price compared to extruded PMMA fibers. The advantages of casted fibers are usually the high light emission over short distances and the high flexibility. Furthermore the mechanical strength is increased due to the robust jacket material.
The disadvantage of casted fibers is the large diameter which makes it difficult to use standard machines in textile production.
The image above shows the result of a new textile process that has been developed to create a luminous textile carrier by the combination of sewing and knitting techniques. Moulded fibres of a diameter from 3mm to 6mm are used.
Textile surface (1.2m x 0.6m) with integrated 6mm casted SL-POF, embedded in a passe-partout with embroidered logo; in cooperation with Textilforschungsinstitut TITV, Greiz
LEDs of 1W power only radiate light into the textile shown. It is bright enough to illuminate a medium sized room for orientation purposes at night .
For each new project a decision must be made between the two types of sidelight fibers mentioned above. The essential aspect is the question how the SL-POF is supposed to be integrated into the textile. Since casted fibers with a minimum diameter of >1mm cannot be integrated with conventional textile processing machines, they are not suitable for use in woven textiles. SL-POF made of PMMA with a diameter of 0.5 mm must be connected to an LED as a bundle fiber for efficient light coupling. This represents a new challenge for cable assembly at the textile manufacturer. In contrast the integration of the “thick” casted fibers using special embroidery techniques enables direct and efficient coupling to PowerLED modules.
For each planned application the following aspects of a sidelight fiber system should therefore be carefully examined at the beginning: the technology of textile integration, the efficiency of light emission, fiber fabrication and economic aspects.
The following are currently available as standard:
PMMA sidelight fiber:
1mm, 2mm, 3mm PMMA SL-POF are also available on request.
Moulded side light fibres
- 3mm SL-POF with transparent jacket,
- 3mm SL-POF with white jacket,
- 6mm SL-POF with white jacket,
- 2mm SL-POF with silicone jacket and 1mm PUR-Kern,
- 5mm SL-POF with silicone jacket and 3mm PUR-K
PUR-SL-POFs with a silicone coating cannot be used for white light, because the spectral components of white light are emitted with different intensity. They can therefore only be illuminated monochromatically.