Perfectly Matched Layer(PML) in FDTD method.

In FDTD method we are truncated the problem space.But in truncating we face the problem of reflection in its boundary.The absorbing boundary condition(ABC)but its quite difficult to make 2D ABC and make use in FDTD method.
This problem is solved by PML.Suppose a wave propagating outward,it will eventually come to the edge of the allowable space,which is dictated by how the matrices have been dimensioned in the program.This probel is solved by this PML.