“…As a rule, in the study of multicore fibers, primary attention is paid to the in-phase supermode [37,39,40]. However, in the recent analytical, numerical, and experimental works, it has been shown that an out-of-phase supermode (in which the phases of the fields in neighboring cores differ by π) can also be of great interest due to its stability in different nonlinear regimes [41][42][43][44]. Multicore fibers allow operation with pulse energies and powers higher than those of one-core fibers [41,42,44] (however, for ultrashort pulses, spatial walk-off of supermodes should be taken into account [45,46]).…”