# Energy audit of a side-glowing fiber model

Canonical: https://www.formlightoptics.com/portfolio/side-glowing-fiber-energy-audit
Markdown: https://www.formlightoptics.com/portfolio/side-glowing-fiber-energy-audit.md

Traced a thin scattering fiber about 100 mm long and found that default ray limits were dropping launched light.

Simulation, fiber optics. 2026.

Capabilities: Simulation, Fiber optics.

### Challenge

Predict how much light leaks from the side of a thin scattering fiber about 100 mm long, and where that light goes.

### Approach

Two independent detector models, an energy-balance check, and a ray-limit sweep were used to see whether the ray trace kept the light it launched.

### Result

Default ray-trace limits silently lost about 6% of the light launched into the fiber. Raising them cut unaccounted light to about 1% and raised the predicted side emission by about 40%.

### Key figures

- ~6%: of launched light lost under default ray-trace limits
- ~1%: unaccounted light after the ray limits were raised
- ~40%: predicted side emission after the ray limits were raised

Tools: custom programs and scripts.

Related services: [Stray light and non-sequential simulation](https://www.formlightoptics.com/services/stray-light-and-non-sequential-simulation).