Novel double-ring optical-guided-wave Vernier resonator

A theoretical study of a novel optical-guided-wave Vernier resonator is presented. The resonator is a compound configuration of two triple-coupler ring-based resonators (CTCRR) with different radii. Transmittance characteristics of the CTCRR are derived by using a combination of transfer-matrix and chain-matrix formulations. The dependence of the transmittance characteristics of the CTCRR on the amplitude-coupling ratios of the directional couplers are studied, and optimum design relationships are determined. An extensive comparison between the CTCRR and two double-ring-resonator (DRR) configurations reported in the literature is carried out. It is shown that the CTCRR features double free spectral range (FSR), higher transmission at resonance, and better crosstalk than DRRs with the same radii of curvature, waveguide propagation loss and finesse. These advantages make the CTCRR particularly attractive for those applications, such as frequency-selective filtering in high-density multichannel optical FDM systems, where conflicting requirements of wide FSR and low insertion loss have to be satisfied