The threshold scheme based on nonlinear polarization rotation (NPR) enables the colorless operation with low thresholding power.The performance of the thresholder is restricted by its physical structure,as the output power of the scheme varies in a cosine-like relationship with the input power.In order to i mprove the thresholding ability of the nonlinear polarization rotation (NPR),a modifie d scheme by adding a tunable bandpass filter is proposed and corresponding experim ent is demonstrat ed.The modified scheme provides more stable output power and higher thresholding ability.By adjusting the tunable bandpass filter,the modified scheme makes the NPR suit any condition and overcomes the drawback of the classical NPR predeter mined by the physical setup.