Crosstalk and Signal Integrity in Ring Resonator Based Optical Add/Drop Multiplexers for Wavelength-Division-Multiplexing Networks

Abstract

With 400 Gbps Ethernet being developed at the time of writing this thesis, all-optical networks are a solution to the increased bandwidth requirements of data communication allowing architectures to become increasingly integrated. High density integration of optical components leads to potential ‘Optical/Photonic’ electromagnetic compatibility (EMC) and signal integrity (SI) issues due to the close proximity of optical components and waveguides. Optical EMC issues are due to backscatter, crosstalk, stray light, and substrate modes. This thesis has focused on the crosstalk in Optical Add/Drop Multiplexers (OADMs) as an EMC problem. The main research question is: “How can signal integrity be improved and crosstalk effects mitigated in small-sized OADMs in order to enhance the optical EMC in all-optical networks and contribute to the increase in integration scalability?” To answer this question, increasing the crosstalk suppression bandwidth rather than maximizing the crosstalk suppression ratio is proposed in ring resonator based OADMs. Ring resonators have a small ‘real estate’ requirement and are, therefore, potentially useful for large scale integrated optical systems. A number of approaches such as over-coupled rings, vertically-coupled rings and rings with random and periodic roughness are adopted to effectively reduce the crosstalk between 10 Gbps modulated channels in OADMs. An electromagnetic simulation-driven optimization technique is proposed and used to optimize filter performance of vertically coupled single ring OADMs. A novel approach to analyse and exploit semi-periodic sidewall roughness in silicon waveguides is proposed. Grating-assisted ring resonator design is presented and optimized to increase the crosstalk suppression bandwidth.