RP ProPulse — Numerical Simulation of Pulse Propagation
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Example Case: Soliton Self-frequency Shift
In this example, we investigate the soliton self-frequency shift arising from stimulated Raman scattering in a fiber. The Raman gain, which gets stronger towards longer wavelengths, amplifies the longer-wavelength components within the pulse spectrum at the expense of power in the shorter-wavelength parts. In effect, the pulse spectrum increasingly drifts towards longer wavelengths. Also, there is a slight decrease in pulse energy and an increase in the pulse duration. It has been assumed that there is no higher-order dispersion.
The diagram above compares the numerically simulated evolution of the center wavelength with that of a simplified analytical model. They agree well.
Below you see results of a simulation where the pulse duration is varied. In agreement with the analytical theory, the numerical model shows that the self-frequency shift becomes substantially stronger for shorter pulse durations. This is because shorter pulses have a higher peak power and a broader spectrum, within which the Raman gain (increasing with the frequency offset) can have a stronger effect.
