Design and analysis of novel multilayer-core fiber with large mode area and low bending loss

A novel multilayer-core intrinsically single-mode large-mode-area fiber is proposed in this paper. The multilayer structure in the core which is constituted of alternating low- and high-refractive index rings could achieve a very low equivalent core-cladding refractive index difference. The single-mode large mode area of 100–12,000μm2 could be achieved in the fiber. The effective area Aeff can be further enlarged by increasing the parameters of low-refractive index rings or the number of layers. Furthermore, the bending property could be improved by 1–2 orders of magnitude in this multilayer-core structure when the outermost layer is depressed-index ring. We have experimentally verified the proposed fiber structure that follows the target of large Aeff along with ultra low bending loss at 1.55μm. These characteristics of multilayer-core fiber suggest that it can be used in large-mode-area high-capacity transmission, or high-power optical fiber laser and amplifier in the optical communications.