We demonstrate manipulating the interactions of a second-order soliton with a weak probe pulse under the condition of group velocity match and group velocity mismatch (GVMM). During these interactions, the second-order soliton acting as an effective periodic refractive-index barrier leads to the polychromatic scattering of the probe pulse, which is represented as unequally spaced narrow-band sources with adjustable spectral width. In the case of GVMM, almost all the spectral components of the narrow-band sources meet the nonlinear frequency conversion relationship by using the wavenumber-matching relationship due to the robustness of the second-order soliton under moderate high-order-dispersion perturbations, so this case is more conducive to the study of the soliton wells. In addition, different transmission states of a soliton well are demonstrated under different probe pulse properties in the fiber-optical analog of the event horizon. When the power of the probe pulse is strong enough, a dispersive wave can be generated from the collision of two fundamental solitons split from the two second-order solitons. These interesting phenomena investigated in this work as a combination of white- and black-hole horizons can be considered as promising candidates for frequency conversion and broadband supercontinuum generation.