Determination of actual interaction length for self-frequency shift of Raman solitons and their independence of pump intensities

The behavior of the soliton self-frequency shift is studied experimentally. To clarify the actual interaction length for the Raman effect and a soliton, multicolor Raman soliton pulses with different shifted wavelengths (10-120 nm) are induced by using a single pump source and a 5.0-km-long highly nonlinear fiber. Although the pump intensities and frequency shift magnitudes are different, the frequency shifts cease at the same interaction lengths (same propagation distance). Then, they gradually diverge due to the chromatic dispersion of the fiber as they propagate further