Study of the reabsorption effect on the ytterbium-doped fiber amplifiers

In this paper, the rate equation of ytterbium (Yb) ion concentration in the upper level and the transmission equations of seed signal, pump, and amplified spontaneous emission (ASE) in the Yb-doped fiber amplifier are solved simultaneously by the explicit Runge–Kutta method. Finally, a full seed signal power spectrum simulation with the range of 1000–1130 nm is achieved. This paper focuses on the amplification of seed signals at different peak wavelengths in different Yb-doped fiber lengths. The main works are as follows: By constructing a 3D data structure of the seed signal, a parallel computing work on the propagation process of Gaussian-lineshape seed spectrum with a peak wavelength of 1000–1100 nm in Yb-doped fiber with a length of 1–30 m has been done, which significantly reduces the calculation time. Furthermore, the accuracy of calculation results has been improved by the iterative method. Finally, the reabsorption effect on the seed signals at different peak wavelengths and the competition between the seed signal and ASE have been analyzed in both single-mode and large-mode-area fibers, and the optimal gain fiber length corresponding to the different peak wavelengths of the seed signal has also been discussed.