An overview of the most important methods for producing side-emitting polymer optical fibers is given. Based on a systematic literature and patent search, the methods that are applied in practice and explored in research are identified. The fabrication methods are classified into four groups according to the physical phenomenon that hinders total internal reflection: bulk scattering, bending, surface perforations and luminescence. Subdivisions are made regarding the actual processing steps. The production methods are described in detail and discussed with respect to their customizability and applications.

A 3×3 textile integrated force-sensor array is presented that is based on the cross coupling of optical fibers and provides multi-touch capability. The force sensing relies on cross coupling between two fibers that are aligned orthogonally to each other. The actual coupling is improved by an increased contact area and higher scattering at the fiber crossing. A systematic analysis of different parameters is done for the driving and the sensing fiber, which involves materials, size, fabrication parameters as well as the cross-section shape. The results reveal that the combination of a rather stiff driving fiber and a flexible sensing fiber from elastomer (TPU) lead to the highest sensitivities in the range of 45.5 pW/N. The application of non-circular cross sections can improve the coupling efficiency by directing the sideemitted light better towards the sensing fiber. A trilobal-shaped driving fiber lead to an increase of 5 dBs, whereas the shaping of the sensing fiber improved the efficiency by another 7.5 dB.

The force-enhanced light coupling between two optical fibres is investigated for the application in a pressure or force sensor, which can be arranged into arrays and integrated into textile surfaces. The optical coupling mechanisms such as the influence of the applied force, the losses at the coupling point and the angular alignment of the two fibres are studied experimentally and numerically. The results reveal that most of the losses occur at the deformation of the pump fibre. Only a small percentage of the cross-coupled light from the pump fibre is actually captured by the probe fibre. Thus, the coupling and therefore the sensor signal can be strongly increased by a proper crossing angle between the fibres, which lead to a coupling efficiency of 3%, a sensitivity improvement of more than 20 dB compared to the orthogonal alignment of the two fibres.

Ultraviolet (UV) bonding technology is widely used across industries. As the curing reaction is initiated via an external light source, the use of fast-curing structural UV acrylates has so far been limited to joint designs with at least one transparent joining part. By introducing a side-emitting polymer optical fiber textile into the adhesive layer, which acts as an embedded light source, the technology can be made accessible for applications with nontransparent substrates such as metals. This paper describes the development of extra thin polymer optical fiber narrow fabrics designed to enable curing of structural adhesive joints. Polymer optical fibers (warp) were combined with different low-titer polyester weft yarns in two fabric design types with different primary out-coupling mechanisms: undulation and surface modification of the polymer optical fibers. The effect of yarn properties, thread densities and weave on fabric quality, geometry and lateral light intensity of each type were investigated. Results showed that narrow fabric production within the tight geometric limits required is feasible. Fabrics manufactured with nontextured yarns at low titers and low weft densities exhibited the highest lateral light intensities for the surface modification type fabric. To compensate for intensity loss over fabric length, investigating light coupling from both sides is recommended for this fabric type. For the undulation type fabric, the lateral light intensity characteristics indicated that the high tenacity yarns are promising candidates for the fabrication of low sidelight attenuation fabrics through modulation of the weft density.

UV bonding technology’s biggest limitation is the need of a transparent joining part to be able to cure the adhesive with an external light source. This is to be solved with ribbon fabrics made with polymer optical fibres (POF) which guide the UV light into the adhesive bond. On the basis of previously published experiments, a set of POF fabrics with different thread densities and weft materials is evaluated optically regarding the emitted UV light intensity and mechanically regarding the shear strength of the adhesive bonds. A factorial experiment plan indicates that higher tensile lap-shear strength comes with lower weft fineness and higher weft density. The maximum shear strength achieved was 8.3 MPa with potential room for improvement due to non-cohesive failure, relatively high weft densities and a comparatively low powered UV light source.