Characterization of single micro-ring resonator filter with doubledfree-spectral range

The study proposes a new structure to double the free-spectral range (FSR) of a micro-ring resonator filterusing optical interference. The proposed structure adds an input light to the Add port of the conventionaltwo-bus one-ring (TBOR) filter and adds a phase shifter to tuning the light. The FSR of the conventionalTBOR filter can be doubled by the interference from the light field of the new input port. In the study, theeffects of the output spectrum depending on the phase shift, coupling coefficient, and loss are discussed.The results show that the resonance wavelength changes by tuning of the phase shifter which increasesthe choice of wavelength. Meanwhile a flat pass band, a sharpness degree of edge rolloff, a high qualityfactor as high as 105and a perfect extinction effect can be obtained by selecting a proper couplingcoefficient. However loss can bring more crosstalk which should be decreased as more as possible.