The cores of waveguide structure in waist of fused biconical tapered coupler

The work presents the results of investigation of wave-guide structures of fused biconical tapered couplers fabricated from single-mode quartz fibers with various GeO
₂
concentrations in the cores. It has been demonstrated that the cross-section dimensions differ in the coupler waists. The authors assume that the experimentally observed dependence of the wave-guide-to-wave-guide coupling in the coupler waist on the fusion mode is determined by a change of the cross-section areas ratio of the cores.