A new and simple numerical computational method simulating the gain characteristics of erbium and ytterbium co-doped phosphate glass waveguide amplifier(EYCDWA)is presented. This algorithm is a combination of the iterative procedure and the Finite-Differences Time-Domain based on Alternating-direction Implicit Method(ADI-FDTD), using ADI-FDTD calculating the normalized field intensity distribution of pump and signal and an iterative procedure studying the power propagation equations of the pump and signal. Numerical results demonstrate that the increase of the length and Er³⁺ concentration is two main approaches to improve the gain of EYCDWA, Yb³⁺ plays an energy transform role and 1~4 ratio of Yb/Er is better.

The optical field distribution of Erbium-doped glass planar waveguide is calculated first by the Finite-Differences Time-Domain based on Alternating-Direction Implicit Method (ADI-FDTD).The principal advantage of this method is that it can simulate the characteristics of the optical field in the waveguide.Its algorithm is simple and the results are unconditionally stable.