Self-oscillations which are caused by the defects of fiber ends in Er/Yb co-doped double-clad fiber amplifier deteriorate the performance of amplifier.Based on the Er/Yb co-doped double-clad fiber amplifier which is designed and implemented by ourselves,the correlations between self-oscillations and signal power as well as self-oscillations and pump power are studied.The results indicate that the self-oscillations strengthen and tend to saturation with the increase of pump power.The oscillations will be res...