The Gain Characters and Optimization of the Double-Pass Two-Stage Ytterbium-Doped Fiber Amplifier

The amplifier chains are always the important parts of fiber amplifiers. In this paper, the gain characters of double-pass two-stage ytterbium-doped fiber amplifier were analyzed in theory. Firstly, the gain and output characters were also demonstrated when the signal power and pump power changed. Secondly, the relationship between gain and the ratio of the two fibers was analyzed when the length of fiber was given. The relationship between gain and ratio of power of two pump sources was also analyzed when the total pump power was given. At last, the optimization and the ratio of two fibers of the double-pass two-stage ytterbium-doped fiber amplifier were also discussed in detail.