Fiber digital twin — forward DAS / DTS model
Research-grade — validation in progress.
The fiber twin runs the inverse direction from every other DAS surface: given simulated geometry and pressure it PREDICTS what the fiber should have seen. VERIFIED FIDELITY TIERS: `quasi-static` is the analytic linear-elastic dipole + poroelastic heartbeat used for fast previews, while `elastodynamic` is the causal retarded-time propagator with P/S arrivals, Q attenuation, gauge low-pass and cement coupling — modeled waterfalls show arrivals, not instantaneous response. `src/lib/fiber/dasForwardStrain.ts` models the opening-mode fracture as a dipole displacement kernel u_z(s) = C·s/(s² + a²) and differentiates to ε_zz(s) = C·(a² − s²)/(s² + a²)² — extension over the fracture flanked by compression lobes (the LF-DAS 'rabbit ears', Ugueto et al. URTeC 2019-193), with amplitude C = (w/2)·a·standoffAttenuation reported in nanostrain, emitted in the exact `FiberOpticFrame` shape the live telemetry adapter uses so modeled fiber renders in the production waterfall. `dtsForwardWarmback.ts` adds the thermal warmback trace, `lfDasForward.ts` the low-frequency band, `dasFiberMatch.ts` the measured-vs-modeled match, and `twinAutoCalibrate.ts` / `twinTuning.ts` the knob inversion. Uncertainty is a seeded Monte-Carlo / bootstrap ensemble (`twinUncertainty.ts`) reduced to percentile bands, with noise auto-estimated from the uploaded CSV (`measurementNoise.ts`), worker offload, and a size-capped result cache. Raw vendor ingest for HDF5 and SEG-Y (`hdf5Ingest.ts`, `segyIngest.ts`). Live DAS overlay on `/coupled-run`. Tier-aware receipts stamp `fiber_forward_model=<quasi-static|elastodynamic>` and `fiber_causality=<instant-quasi-static|retarded-time-arrivals>`.
The quasi-static tier remains a lumped-standoff analytic preview; the elastodynamic tier is causal but still uses a reduced dipole source. Next ship: replace the dipole kernel with the DDM displacement field already computed by `runNonPlanar3DPipeline` so the modeled strain inherits real out-of-plane geometry, and close the loop by driving the tuning inversion from the coupled run instead of the analytic twin.
No phase markers extracted from this row's prose yet.
- No published error band yet — use with engineering judgment.