Raman-induced spectral shifts in optical fibers: general theory based on the moment method

The Raman-induced spectral shift of ultrashort pulses, having its origin in the phenomenon of intrapulse Raman scattering occurring inside silica fibers, has been mostly studied in the context of optical solitons. We use the moment method to show that such a spectral shift occurs both in the normal and anomalous-dispersion regimes and depends not only on the pulse width but also on the frequency chirp associated with an optical pulse. The magnitude of spectral shift depends on the history of pulse width changes and saturates to a constant value if the pulse broadens considerably during propagation. (C) 2003 Elsevier Science B.V. All rights reserved.