Spectroscopic experiments regarding the efficiency of side emission optical fibres in the UV-A and visible blue spectrum

Spectroscopic experiments were conducted to characterise commercial side emission optical fibres regarding their emission spectra and the intensity of emitted radiation in the spectral range from UV-A to visible blue. For fibres with silica core and scattering particles embedded in the cladding, the emission spectra are determined by the material of the scattering particles. While Al2O3 particles allow emission of UV-A and visible blue light, ZnO filters most of the UV-A light up to wavelengths of 380 nm. The emitted intensity ideally decays exponentially along the fibre with a decay constant that is correlated to the particle concentration. The absolute values of the emitted intensity increase with increasing fibre radius. For fibres with PMMA core and surface perforation, relatively weak background emission of UV-A and blue light and additional local emission peaks due to the surface treatment were observed. The background emission can be explained by scattering due to the intrinsic non-uniformity of the PMMA core. The surface defects cause highly non-uniform and directional emission at a relatively high intensity. Compared to the silica core fibres, higher emission intensity in the UV-A and visible blue spectrum, albeit at a non-uniform distribution, was observed although the transmission along the fibre over longer distances is significantly lower for PMMA core fibres than for fibres with silica core.