The behavior of fiber Bragg grating (FBG)-stabilized 980-nm pump lasers is experimentally and theoretically investigated. The subkilohertz noise in the emitted power is related to the coexistence and oscillation between coherence collapsed state and narrow linewidth single-mode (SM) operation. These findings are theoretically discussed by using a multimode time-domain model that accounts for spatial harmonics and includes nonlinear gain. One additional result is an indication that kinks in the L--I curve can be explained by nonlinear mode competition.
Alberto Ferrari, Giorgio Ghislotti, Stefano Balsamo, Vittorio Spano, and Fiorenzo Trezzi, "Subkilohertz Fluctuations and Mode Hopping in High-Power Grating-Stabilized 980-nm Pumps," J. Lightwave Technol. 20, 515- (2002)