Hybrid fiber grating-based optical comb filters with changeable channel numbers

摘要

An in-fiber Mach-Zehnder interferometer filter based on a pair of long-period fiber gratings (LPFGs) has 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 from 1 to 5 and 3 to 9 have been achieved, respectively.