An in-fiber Mach-Zehnder interferometer filter based on a pair of long-period fiber gratings (LPGs) had been operated in the reflection mode by incorporating a broadband chirped-fiber Bragg grating (CFBG) or an optical fiber mirror reflector.As a result,the extinction ratio has been nearly doubled and,by tuning chirp rate,i.e.reflection bandwidth of the CFBG using a beam-bending method,channel number of the formed optical comb filter can be easily changed.In our experiment,two comb filters with channel numbers being changed among odd ones from 1 to 5 and 3 to 9 have been achieved,respectively.Even channel filtering can also be achieved if the center wavelength of the chirped fiber grating is changable.