Raman multi-peak solitons in photonic crystal fibers

Pulse splitting is a well-known process occurring in the very initial moments of pulse propagation in nonlinear optical fibers. According to the most accredited theory of pulse splitting, in the femtosecond regime, higher-order solitons are affected by stimulated Raman scattering and higher-order dispersion terms, becoming unstable and eventually breaking up into several fundamental solitons. However, this well-known description ignores some processes that could affect the soliton dynamics, such as interaction between solitons, and the emission of dispersive wave radiation near a zero group-velocity dispersion point. In a series of recent experiments short and intense pulses have been launched in highly nonlinear photonic crystal fibers (PCFs). The unexpected formation of long-lived two-peak soliton states for specific magic input pulse energies was observed. Such soliton states were numerically discovered and studied in 1996 by Akhmediev et al.. Inspired by the recent experimental observation of the Raman multi-peak states in and by the early numerical findings in, we investigate the issue of Raman multi-peak states in detail.