Simulation-aware design
In Qfactr, transmission and loss come from the geometry you actually drew. A single Simulate action surfaces them on the canvas, so you can see the physical cost of a layout while you build it.
Most photonic layout tools treat physics as a separate, downstream step: you draw a schematic, hand it off, wait for a solver, and only then learn whether the geometry holds up. Qfactr keeps physics close to the design. Because every component carries S-matrix data and every connection is a real waveguide route between real pins, the workspace can derive transmission and loss directly from the layout you have in front of you.
This is what "simulation-aware" means here: design-time feedback grounded in the actual path geometry, fast enough to inform the next edit. It does not replace a full electromagnetic or circuit solver. It tells you, as you work, whether a route is clean or whether a detour is quietly costing you optical power.
Why geometry is the signal
In photonics, geometry is loss. Light traveling through a circuit pays for every bend, crossing, and detour. Tight bends radiate power out of the waveguide; crossings scatter light at each intersection; longer paths accumulate propagation loss along the way. Two layouts that are electrically identical as a netlist can differ substantially in insertion loss purely because of how they are routed on the chip.
Because Qfactr models a circuit as physically true geometry rather than abstract nets, it has the information needed to estimate these costs. Components contribute their S-parameter behavior; routes contribute the length and shape of the waveguide path between pins. The result is a transmission and loss estimate that reflects the design as drawn, not an idealized version of it. For the underlying mechanisms, see Waveguides and routing.
Running Simulate
Simulate is an action in the workspace toolbar. Trigger it on the current design and the workspace evaluates the routed paths and reports back on the canvas.
- Route your circuitConnect components pin to pin so the signal path is complete. Unconnected pins render red; once a route lands, they turn green. A path can only be evaluated where it actually exists.
- Trigger SimulateRun the Simulate action from the toolbar. The workspace derives transmission and loss from the current geometry.
- Read the power flowA gradient animates along the waveguides showing power flow, running teal to green to yellow to red as power drops along the path. The visualization makes lossy segments easy to spot at a glance.
- Read the lossA loss readout appears in the status bar, giving you a number to pair with the visual gradient.
- IterateAdjust placement or routing to shorten paths, relax bends, or avoid crossings, then re-run Simulate to confirm the change helped. This is the loop that lets you iterate in days, not weeks.
In-canvas feedback vs. full simulation
It helps to be precise about what this feedback is and is not. The in-workspace estimate is fast, geometry-driven, and meant to guide design decisions in real time. It is deliberately scoped to keep you in the loop while you place and route. It is not a substitute for full physical simulation.
| In-canvas Simulate | External simulation | |
|---|---|---|
| Purpose | Design-time loss awareness while you build | Detailed verification and analysis |
| Driven by | The actual routed path geometry and component S-matrices | Full circuit or electromagnetic models |
| Speed | Fast enough to inform the next edit | Heavier, run when you need depth |
| Output | Power-flow gradient plus a loss readout | Spectra, time-domain response, and more |
When you need rigorous analysis, the same design exports to dedicated solvers. Use SAX or Simphony for circuit-level, frequency-domain S-parameter simulation, and PhotonTorch for time-domain simulation on GPU. The point of the in-canvas estimate is to make sure that by the time you reach those tools, the geometry is already in good shape.
From the canvas to a simulator
Because the workspace holds one editable model carrying layout, connectivity, and physics together, there is no translation step between what you designed and what you simulate. The same circuit that produced the in-canvas loss estimate is the circuit you export. Choose the target by the question you are asking: a circuit simulator for frequency-domain S-parameter behavior, a time-domain simulator for transient and GPU-accelerated analysis.
The export targets and what each is for are covered in detail on the Export formats reference, and the export workflow itself in Exporting your design.