We have studied theoretically and experimentally supermode competition in a
n actively mode-locked Er-fiber laser that operates in a high harmonic mode
. Using an innovative numerical technique that allows us to properly accoun
t for the complex interaction of multiple pulses with the gain media, ive c
ould study the dynamics that leads to supermode competition, pulse dropouts
, and pulse pair generation, and to accurately predict the Limits of the st
able operating regime.