A novel Mach-Zehnder interferometer(MZI) is proposed by splicing a section of homemade dual-core photonic crystal fiber(D-PCF) and two segments of single mode fibers(SMFs) and collapsing the air holes in the splice regions.The mode characteristics of the cross section were analyzed with the image-extracted method and the finite element method.The results show that the interferring modes of the novel MZI are the ring-core modes,which is different from the traditional interferometer.The relations between the ...