Cross modulation instability in normal-dispersion fibre lasers and amplifiers

This paper examines instability resulting from cross phase modulation interaction between signal and pump waves in normaldispersion fibre lasers and amplifiers. From analysis of the dispersion relation for the wave vector of small harmonic perturbations, we derive dynamic spectral characteristics of the modulation gain coefficient. Its dependence on the group velocity difference between signal and pump waves is investigated. Analytical results are compared to numerical simulation data. We discuss how the general relationships obtained in this study can be used in practical applications.