Analysis of material concentration in step-index fibers with alumina cores produced by means of the powder-in-tube technique.

Step-index fibers (SIFs) with alumina cores were fabricated employing the powder-in-tube technique. The fabricated SIFs have alumina concentrations of up to 32 mol%, which is the highest value reported so far for fibers with core diameters smaller than 25 μm. The mixing mechanisms between alumina and silica during fiber drawing were revealed by energy dispersive X-ray analysis of the neck-down area of the preform.