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Traditionally, photonic ICs (PICs) have consisted of a few components and are designed as specialized, standalone devices. We’re now seeing applications for integrated photonics become proven and commercialized. As a result, there’s a demand for higher complexity circuits and a tighter interplay between photonics and electronic ICs.
That’s why we’re seeing photonic design frameworks being integrated into familiar EDA tools to take advantage of schematic-driven workflows, verification methodologies, and reliable automated layout. With integration, however, comes a need to co-simulate both the electrical and optical/photonic parts of the design.
In most cases, the time scales of the electrical and optical signals are so different that one can run sequential simulations efficiently and link the electrical and optical domains via waveform exchange. For example, in a transceiver design, the electronic driver circuit simulation output waveform can be used as input stimulus for the optical circuit simulation. The consecutive optical circuit simulation generates an output waveform, which can then be used as an input source for a transimpedance amplifier (TIA) design simulation
However, in some cases, with tighter interplay between electronic and photonic regimes, a true co-simulation is necessary to understand and optimize circuit operation. The most common examples are control loops for laser wavelength stabilization and electro-optic oscillators.
Lumerical, a Cadence partner, has unveiled an electrical/optical co-simulation capability in its INTERCONNECT photonic IC simulator. INTERCONNECT is a time- and frequency-domain mixed-signal photonic circuit simulation engine similar to SPICE that is specially designed to account for the multi-mode, multi-channel circuits found in integrated photonics.
INTERCONNECT is part of an electronic/photonic design automation (EPDA) environment (shown below) that Lumerical developed with Cadence and PhoeniX Software, another Cadence partner. Built on Cadence’s Virtuoso custom design environment, the EPDA methodology addresses the challenges of electrical and optical circuit design in one flow. You can capture your optical circuit in Virtuoso Schematic Editor, simulate your design with Virtuoso Analog Design Environment and the INTERCONNECT engine, and implement your layout within the Virtuoso Layout Suite XL environment, using PhoeniX’s generic photonic building block library and waveguide generator.
For electrical/optical co-simulation, the EPDA framework combines INTERCONNECT and Cadence’s Spectre simulation environment. For each time step in a co-simulation scenario, both the electrical and optical domains are updated as they interact with each other. A Verilog direct programming interface (DPI) synchronizes and performs data exchange between the Spectre electrical circuit simulator and the INTERCONNECT photonic circuit simulator. With an automatically generated wrapper in Verilog-A, you can use optical sub-circuits within the Spectre environment.
“We’re at the early edge of transition into a much more streamlined design methodology for integrated photonics within a traditional EDA framework.” said Bill De Vries, Lumerical’s director of marketing. “This drives reliability, performance, and scale in next-generation designs utilizing integrated photonics technologies.”
To provide more insights into photonic IC design, Cadence and its partners are planning a photonics summit and workshop October 19 and 20 at Cadence's San Jose headquarters. Hope to see you there!