We present new results regarding a novel melt spinning process for the continuous production of polymer optical fibers (POF) with a graded index profile. The fabrication process comprises a conventional melt spinning process of PMMA and a conclusive abrupt cooling of the monofilament. During the quenching, the outer part of the fiber cools down faster than the inner part, which leads to a density gradient within the fiber due to the time difference for thermal expansion along the fiber radius. This results in a radial density and by that in a refractive-index profile. The density of the POFs is determined with a pycnometer. Moreover, the structural properties of the fibers are investigated by small-angle X-ray scattering (SAXS). Lastly, the resulting optical parameters such as refractive-index profile, fiber attenuation and scattering properties, are studied and related to the manufacturing parameters. The measurements of the density and refractive index show that the refractive-index profile of a PMMA fiber can be strongly influenced in the outer sector of the fiber, but the influence decreases radially inwards. The SAXS measurements indicate different polymer chain structures within the fiber form.
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