General coupled-mode analysis for gain-guided, index-antiguided fibers, and index-guided fibers

Coupling properties of two gain-guided, index-antiguided (GG + IAG) fibers, or GG + IAG fibers and index-guided (IG) fibers, were investigated by the further general coupled-mode theory. The theory can explain any situation of two fiber coupling. The interesting results were obtained by the numerical computation method. For two GG + IAG fiber coupling, total power was decreased as rising real-valued refractive-index difference (real part of refractive-index difference between core and cladding, RVRID), while the power of one GG + IAG fiber was damped oscillations with increased core separation. In the GG + IAG fiber and IG fiber coupler, the variation of the RVRID could change coupling characteristics. These results are different from two IG fibers coupling, and the general coupled-mode theory may provide meaningful references for new concepts of directional coupler and pumping technology of GG + IAG fiber.

Research Highlight
► Suggesting the theory that can explain any situation of two fiber coupling.
► Some interesting results have been obtained in GG+IAG fiber and IG fiber coupler.
► Providing meaningful references for new concepts of directional coupler.
► Providing meaningful references for new pumping technology of GG+IAG fiber.