the 3D Finite-Difference Beam Propagation Method(FD-BPM) is deducted
which is used in AWG simulations to compute and simulate the transmission process of the optical field in the array waveguide.The results show that the computation accuracy is improved by using 3-D BPM.Furthermore
as the 3-D BPM is insensitive to portrait step size
the calculation time can be shortened by increasing the step size
thus improving the accuracy with little effect on the calculation time.