Hybrid Fiber Grating-based Optical Comb Filters with Changeable Channel Numbers
一种通道数可变的光纤光栅梳状滤波器

An in-fiber Mach-Zehnder interferometer filter based on a pair of long-period fiber gratings (LPGs) 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 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 changeable.