Experimental determination and ray-tracing simulation of bending losses in melt-spun polymer optical fibres

Abstract

The damping properties and specifically the bend losses of polymer optical fibres (POFs) have so far only been documented by experimental work, investigating bending parameters such as bending radius, length, and distance of the bends. Even though damping mechanisms and causes are wellknown, no simple, generally valid formula exists. Here, a simulation technique is shown that allows producing an optical model for any bending geometries of melt-spun polymer optical fibres. The developed model takes all relevant loss mechanisms into account, especially regarding the scattering losses at the interface of core and cladding as well as those of the cladding-air interface. The latter is caused by interfacial roughness for which experimental data have been obtained by atomic force microscopy measurements. To show the validity of the simulation, the model is compared to experimental results for several fibres and a variety of geometries. The variance between model and experimental data is low (S < 4.6%). The model not only contributes to improving the understanding of the optical properties of POFs, but it also has direct applicability to the design of photonic textile sensors for medicine, where the fibres are incorporated with small bending radii.

Enhanced Side-Illumination of Etched Polymer Optical Fiber (POF)-Incorporated Woven Polyester (PET) Fabrics

“…Correspondingly, part 1 for increase of side illumination intensity and part 2 for decrease of side illumination intensity were specified, respectively. Since POF-incorporated PET fabric consisted of POFs as weft yarns and PET yarns as warp, where side emission can be caused by micro-bends or macro-bends [21].The distance as border between part 1 and part 2 was 16.21 mm, where the maximum side illumination intensity was found as 45.75 cd • m -2 . Correspondingly, 16.21 mm could be the practical length of etched POF-incorporated PET fabric for optimal side illumination intensity.…”

An Overview on Methods for Producing Side-Emitting Polymer Optical Fibers

“…Lateral emission is considered a disadvantage in data transmission via optical fibers, which is why this phenomenon is also referred to as bending losses. The bending losses of POF were investigated simulatively and experimentally in numerous studies in the past [40,42,46,[92][93][94][95][96]. For POF sensing, bending losses can be used as a feature, e.g., when it comes to measuring displacement [97], deformation [98], strain [99], pressure [100], weight [101], humidity [102], refractive index [95], breathing rate [103] or bending itself [104], among others, or to increase the penetration depth of evanescent waves [105] in other sensing applications.…”

“…Most of the light is emitted from the convex surface of the bent fiber. Side emission can be induced by both microbends where the bending radius R is in the range of the POF radius r or smaller, as in many textiles such as woven or knitted fabrics, or macrobends with R >> r [40][41][42]. -Surface perforations (cf.…”

Obtaining artifact-corrected signals in fiber photometry: Isosbestic signals, robust regression and dF/F calculations

“…An especially problematic source of artifacts stems from animals' movements. Movement generally causes the optic ber patchcord to bend, reducing light transmission through the ber [6,7] (Figure 1B). This effect of bending on measured signal is dynamic, non-linear and can correlate with an animal's location and speci c behaviors.…”