In this work, step-index optical fibers with up to 0.88 numerical aperture (NA) were designed, modeled, fabricated, and tested. Both ray-tracing and wave-optics propagation analysis were utilized to model the NAs that can be achieved for a step-index optical fiber by modifying the cone angle of the fiber tip. Cone-shaped optical fibers with conical semiangles up to 29°, which renders to NAs around 0.88 in air, were fabricated by static etching and tested when utilized as illumination sources.