Soliton generation in optical fibers for a dual-frequency input

We analyze scenarios of soliton generation in an ideal fiber for an input that consists of either two in-phase or out-of-phase solitonlike optical pulses at different frequencies. In both cases the relationship between the structure of the emerging solitons and the frequency separation of the initial solitons is studied both analytically and numerically. Depending on the value of the frequency detuning, if the two initial solitons are in phase (symmetric input), two bound solitons with equal amplitudes (breather), a single soliton, or a pair of solitons, which have equal amplitudes and exhibit opposite velocities, can be generated. When the two initial solitons are out-of-phase (antisymmetric input), only the last scenario takes place. Also, we calculated the threshold values of the frequency separation at which the structure of the emerging solitons changes. Moreover, we demonstrated that two of these critical frequencies correspond to cusplike maxima of the energy density of the radiative modes. Finally, we show that these analytical results are entirely verified by numerical simulations.