A comb-filter based on fiber Mach-Zehnder interferometer(MZI) is fabricated by placing a section of single mode twin-core fiber(TCF) between two single mode fibers(SMFs).The relationships between the wavelength space between the adjacent transmission peaks of the transmission spectrum of the MZI and the wavelength,the length of the TCF and the effective index difference between the two cores are analyzed by using the interference theory.The results show that when a central wavelength is set,the wavelength s...