Optical Crosstalk Improvement in Ring Resonator Based Add/Drop Multiplexers Using Controllable Reflectivity

In this paper, the topic of optical signal integrity is approached by studying crosstalk suppression in ring resonator based optical Add/Drop Multiplexers (OADM). The resonance splitting induced by surface corrugation is exploited to enhance signal integrity by increasing the crosstalk suppression bandwidth compared to that of a smooth-walled resonator. Sidewall roughness in silicon-on-insulator waveguides is studied using Coupled Mode Theory (time and space domain CMT). An analytical model of a corrugated ring resonator is presented, which is then exploited to estimate the spectral response of the different ports. Verification against results generated from full-wave electromagnetic numerical modeling of a randomized corrugated ring is performed. The analysis then examines the performance of an OADM with controllable reflectivity resulting from a predefined corrugation of sidewall. Gratings have been successfully used in optical filters; this paper proposes the use of a grating in an OADM, giving more controlled roughness. A grating-assisted design of a single ring OADM with 28 GHz crosstalk suppression bandwidth is presented. This bandwidth supports the dropping of 10 Gbps signals with mitigated crosstalk levels and improved signal integrity.