To utilize the bandwidth for high data rates and low channel spacing used in high dense WDM system. We adopt High data rates has range from 2.5 Gbits/s to 40 Gbits/s and channel spacing is 200 GHZ, 100 GHZ, 50 GHZ, 25 GHZ. The WDM system has draw back like crosstalk between two adjacent channels due to which signal get distort. So we can use high data rates which is used in this paper i.e. 2.5 Gbits/s and 10.52Gbits/s and low channel spacing. For getting the high channel isolation we can use two FBG filter which are connect back to back each other and different apodization profile like Uniform apodization, Gaussian apodization, Tanh (Hyperbolic Tangent) apodization profile. In this paper simulation has been carried for different apodization profile in which Tanh (Hyperbolic Tangent) has best performance than other two apodization profiles.