Intermodal soliton interaction in nearly degenerate modes of a multimode fiber

We numerically investigate the interaction of two temporal solitons propagating in the two degenerate or nearly degenerate modes of a multimode fiber. Similar to the case of single-mode fibers, the solitons are found to attract or repel each other depending on their relative phase, even though they belong to two different modes of the fiber. However, unlike the single-mode case, each soliton transfers some of its power to the other mode through intermodal four-wave mixing. Our results show that, in spite of this intermodal power transfer, each soliton keeps propagating as a bimodal soliton and interacts with the other bimodal soliton as if they were propagating inside a single-mode fiber. Indeed, the total power in the two modes evolves similar to the case of a single-mode fiber. We study the impact of varying input parameters such as the relative phase, amplitude, and spacing of the two input pulses used to excite the fundamental solitons and point out differences introduced by the intermodal nature of the nonlinear effects. (C) 2016 Optical Society of America