Abstract: A novel optical filter combining ring resonator with Mach-Zehnder interferometer was designed. In this structure, four fiber ring resonators were cascaded and combined with Mach-Zehnder interferometer using coupler. Formulas of the transfer functions were deduced by fiber ring resonance theory and signal flow graph method and the simulation analysis was given as well. The results showed that output spectrum of this filter had excellent performance such as flatness filtering response, strengthening of rolloff in transition band, narrow bandwidth and high finesse. The numeral calculations showed that the fineness of this structure reached 69. 4, it is able to select and extract optical signal precisely in dense wavelength division multiplexing system.

Key words: integrated optics, optical filter, ring resonator, Mach-Zehnder interferometer, high finesse