Based on the technique of master oscillator power amplifier (MOPA), a two-stage ytterbium-doped fiber amplifier
(YDFA) with all-fiber structure is theoretically simulated. The seed signal operating at the wavelength of 1064 nm has
the characteristic of high repetition rate (10 MHz), ultrashort pulse duration (10 ps), low signal power input (20μW) and
single longitudinal mode. The gain (and amplification stimulation emission power) is calculated at the different pump
powers and gain fiber lengths of YDFA pumped by 975 nm. In addition, the amplifications at the different signal power
inputs (1-25μW) are also simulated. The numerical results can be used to optimize the YDFA.