Chirped Bragg gratings were used as reflecting planes to construct Fabry-Perot(FP) cavity.Superimposed and chirped Bragg gratings in the same position of fiber were achieved by applying stress and moving photo mask respectively.In the experiment for the photo mask with 1 nm chirp,obvious comb-like transmission spectra could be obtained by both two methods above.Free spectrum range of transmission spectrum can be 0.6 nm with the method of moving photo mask.The classical coupled mode theory is tak...