The influence of refractive index disturbance of ring-core fiber with central air hole on modes separating.

• Due to the production process, the refractive index of the fiber is different from the ideal refractive index. We studied the effect of this difference on the performance of the separating vector mode of the ring fiber. • Established a model to simulate how impact the ring thickness, the maximum refractive index of the ring and curve steepness have on the mode separation. • Fabricated two ring-core fiber and compared their performances. In this paper, the influences of the ring thickness, the maximum refractive index of the ring and curve steepness on the mode separation are analyzed. The model is established with considering the actual fiber fabrication, especially the transition range between two adjacent layers are studied. Then we manufacture the ring-core fiber with central air hole. This study has reference significance for the structure design of vortex optical fibers. [ABSTRACT FROM AUTHOR]