Spectral and temporal investigation of self-phase modulation and stimulated Raman scattering in a single-mode optical fibre

An investigation of the spectral and temporal characteristics of the self-phase modulated pulses exiting from a germania-doped fused-silica-core single-mode optical fibre has been undertaken at 1.064 ¿¿m. For peak powers below the stimulated Raman scattering threshold the spectral data were in excellent agreement with a simple theory developed for negligible fibre group-velocity dispersion and symmetrical chirp-free input pulses. For elevated peak-power levels a complementary study of the temporal and spectral features of the first-order Stokes Raman and pump pulses has been carried out. It was observed that the onset of stimulated Raman scattering leads to both spectral and temporal pump-pulse asymmetry and hence to deviation from the theoretical spectral predictions. In addition, a simple fibre Raman oscillator was constructed and its characteristics are described in some detail.