curvecheck - curvature analysis and curvature-DRC for photonic paths

Smooth (Euler / clothoid) waveguide bends lose less light than circular bends because their curvature changes continuously instead of jumping. Layout tools like gdsfactory can generate those bends, but they do not check an arbitrary routed path: where is the curvature too tight, where does it jump, and how much loss does that cost? curvecheck answers that. Give it a path centerline and it returns the curvature profile, flags minimum-radius violations and curvature discontinuities, and estimates the relative bend loss.

Status

Module	What it does	State
curvature.py	signed curvature kappa(s) along a path centerline	done
mincurv.py	minimum radius of curvature and curvature-DRC (flag R < R_min)	done
discontinuity.py	detect curvature jumps (straight-to-arc junctions)	done
bendloss.py	relative bend / transition loss estimate from the curvature profile	done
pathio.py	centerline from points, a JSON file, or a gdsfactory Path	done
report.py	structured report and a curvature-profile figure	done
cli.py	curvecheck path.json end to end	done

Usage

curvecheck path.json -o review/ --r-min 10    # writes review/report.md, report.json, curvature.png

import report, pathio
rep = report.analyze(pathio.centerline("path.json"), r_min=10)
print(report.to_markdown(rep))

A circular bend and an Euler bend of the same minimum radius, side by side:

== circular 90 degree bend, minimum radius 15 um ==
- minimum radius: 15 um (max curvature 0.0668 /um)
- curvature discontinuities: 2
- estimated relative bend loss: total 1.21 (transition 0.0356, radiation 1.17)

== euler 90 degree bend, minimum radius 15 um ==
- curvature discontinuities: 0
- estimated relative bend loss: total 0.949 (transition 0, radiation 0.949)
- no curvature issues found

The bend-loss number is a documented relative proxy (it ranks paths), not a calibrated dB figure.

Run

python examples/quickstart.py          # compare a circular and an Euler bend
python run_checks.py validate <name>   # one module's self-check
python run_checks.py suite             # pytest tests/

Requirements

• numpy, matplotlib. gdsfactory is optional, for reading a Path centerline.