Influence of signal bandwidth on mode instability threshold of fiber amplifiers

摘要

We show how signal linewidth affects the gain of stimulated thermal Rayleighscattering (STRS) which is responsible for mode instability in fiberamplifiers. The gain is reduced if the coherence time of the signal is lessthan the group velocity induced walk off between modes LP$_{01}$ and LP$_{11}$.We derive equations for short pulses, linear chirps, and general periodiccases.