Absorbing boundary conditions (ABCs) are widely used for boundary absorbing which can reduce the error from the boundary reflection in simulation space. In the thesis, we explore and analyze the absorption of a convolutional perfectly matched layer (CPML) optical target under the condition of different resolutions, and different frequencies Gaussian beam source in the Finite-Difference Time-Domain (FDTD) simulations. We show the performance of CPML optical target that eliminates the impinging wave and analyze the absorption efficiency of CPML optical target with different resolutions and the influence by different frequencies source. Specific simulation results show that the absorption of the CPML optical target is dependent upon its resolution, but independent upon the source frequency. In turbid media such as biological tissue, electromagnetic (EM) wave would be scattered strongly so that makes the light come from any direction possibly. By using the optical target to absorb the impinging wave from arbitrary direction, we can model light propagation through biological tissue to a specific target posistion.