一种通道数可变的光纤光栅梳状滤波器

利用级联长周期光纤光栅与具有宽带反射功能的啁啾光纤光栅,构成了一种反射型的光纤光栅梳状滤波器.由于光在输出前经过两次干涉滤波作用,所以该梳状滤波器的消光比与透射输出型(即反射前)相比,增加了一倍.而且,通过调节啁啾光纤光栅的反射带宽,可以改变滤波器输出信道的数目.实验中利用弹性梁弯曲的方法,获得了两个可调的光纤光栅梳状滤波器,其信道数可分别在1～5和3～9之间的奇数间调谐(如果改变啁啾光纤光栅的初始中心波长,也可以获得偶数信道间的调谐).

Hybrid Fiber Grating-based Optical Comb Filters with Changeable Channel Numbers

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.