Generation of two colliding pulses with tunable THz range frequency difference in high-nonlinear photonic crystal fiber

For generation of pairs of femtosecond colliding soliton pulses near 1550 nm with controllable frequency difference in THz range the use of splitting of each pulse from pulse train in highly nonlinear microstructure fiber is considered. The pulse with self-induced Raman shift collides with another consequent pulse which have no or less shift from the same pulse train.