Numerical simulation of characteristics of high power ytterbium-doped double-clad fiber amplifier

The theoretical model of high-power ytterbium-doped double-clad fiber amplifier was described, and the method for calculating amplified spomtaneous emission(ASE) was analyzed, with the amplifier operating in CW regime and pulse regime. The characteristics of steady-state and pulse amplifiers were respectively simulated by Runge-Kutta method and finite-difference method. The results show that the pulse gets sharper and narrower on the condition of saturation gain, and utilizing double clad large mode fiber and backward pump scheme can reduce ASE and bad nonlinear effect dramatically.