In this paper, it is demonstrated, by means of simulations, the practical feasibility of an interference filter, implemented from a stack of high and low index birefringent thin films that can be used as transmission filter. Simulations were carried out with a software toolbox package implemented as Matlab™ m-files. The simulation is done by using the following linear material (AgB, ZnSe, KF2, GaAs, BaF2, TiO2) as coating material with single FBR (fabry perot resonator) structure , and KB7 glass as substrate material. Result show that difference between the values of refractive index of multi layer stack has great influence on the transmittance value, the largest possible value is the best choice for obtaining nearly 100% transmittance for the designed wavelength taken and this clearly observed in the simulation figures. In addition, Number of antireflection layer (N) effect clearly on the result, the design parameter that take GaAs as high refractive index material and BaF2 as low index material with N=4 represent good approach to the desired value for the simulated filter that’s used in (DWDM) .