Photonic integrated circuits (PICs) offer compelling solutions for applications in many areas due to the sufficient functionality and excellent performance. Optical interconnects and radio frequency (RF) photonics are two areas in which PICs have potential to be widely used. Optical interconnect system efficiency is dependent on the ability to optimize the transceiver circuitry for low-power and high-bandwidth operation, motivating co-simulation environments with compact optical device simulation models. Compact models for vertical-cavity surface-emitting lasers (VCSELs) and silicon carrier-injection/depletion ring modulators which include both non-linear electrical and optical dynamics are presented, and excellent matching between co-simulated and measured optical eye diagrams is achieved.
Advanced modulation schemes, such as four-level pulse-amplitude modulation (PAM4), are currently under consideration in both high-speed electrical and optical interconnect systems. How NRZ and PAM4 modulation impacts the energy efficiency of an optical link architecture based on silicon photonic microring resonator modulators and drop filters is analyzed. Two ring modulator device structures are proposed for PAM4 modulation, including a single-segment device driven with a multi-level PAM4 transmitter and a two-segment device driven by two simple NRZ (MSB/LSB) transmitters. Modeling results show that the PAM4 architectures achieve superior energy efficiency at higher data rates due to the relaxed circuit bandwidth.
While RF photonics offer the promise of chip-scale opto-electrical systems with high levels of functionality, in order to avoid long and unsuccessful design cycles, efficient models that allow for co-simulation are necessary. In order to address this, an optical element modeling framework is proposed based on Verilog-A which allows for the co-simulation of optical elements with transistor-level circuits in a Cadence design environment. Three components in the RF photonic system, Mach Zehnder (MZ) modulators, 4th order all pass filter (APF)-based optical filters, and jammer-suppression notch filters are presented to demonstrate the capability of efficient system design in co-simulation environments.
