Amplified Spontaneous Emission（ASE）produced by pulsed fiber laser system is an important factor restricting the peak power.Pulsed pump is an effective method to suppress the ASE among the pulses of pulsed fiber lasers.The pulse pumping characteristics of Yb doped double clad fiber amplifier are experimentally studied in this paper.An experimental model consisting of a signal source

an isolator

an amplifier stage and a filter is designed.For the pulsed pump

the pump power and pump duration are two most important factors

which are required to be determined during amplifier design.In this paper

the relationship between pulse energy and ASE with pump power and duration is studied.The conclusions are valuable for the design of pulsed pump fiber amplifier.