In this paper an optical filter having ring resonator structure with micro rings inside it, has been investigated. By variation the radius of main and inner rings, the variation of central frequency and insertion loss of filter in communication spectrum (1.5 µm to 1.6 µm) have been studied. By increasing the radius of main ring, the central frequency of filter move toward the lower frequencies, then central frequency of filter can be adjusted by the radius of main ring. Radius variation of main ring has not considerable effect in filter loss. Also, variation of inner ring’s radius, affects the filter insertion loss, and have a little displacement on the central frequency of filter. The maintained filter will have the minimum loss, when the inner rings radius have been selected equally 0.2 micrometer. By proper selection of radius sizes one can tune the filter precisely for desired resonance frequency and loss. پرونده مقاله