# LED-to-fiber coupling feasibility study

Canonical: https://www.formlightoptics.com/portfolio/led-to-fiber-coupling-study
Markdown: https://www.formlightoptics.com/portfolio/led-to-fiber-coupling-study.md

Tested whether added optics could push more LED light into a small optical fiber, and found the lower-cost answer.

Optical sensing instrument startup. 2025.

Capabilities: Illumination, Freeform, Fiber optics, Simulation.

### Challenge

The client wanted more light from an LED into a small-core fiber. Direct coupling delivered only a few percent. Any added optic would add cost, so the gain had to be real.

### Approach

We started with an etendue budget to bound what any optic could achieve. We then modeled lens trains, a freeform reflector, solid and fused tapers, and direct contact, first with an ideal source and then with the LED maker's measured ray data and a fiber model with the real numerical aperture. Two ray tracers were used to cross-check results.

### Result

No added optic beat direct contact once the measured source and fiber acceptance were included, which spared the client the cost of a custom optic. The client moved to a larger fiber, which was the effective lever.

### Key figures

- ~5% to ~40%: coupling efficiency by resizing the fiber instead of adding optics
- 4: optical concepts ruled out before any tooling

Tools: Zemax OpticStudio, TracePro.

Related services: [Illumination design](https://www.formlightoptics.com/services/illumination-design), [Zemax OpticStudio consulting](https://www.formlightoptics.com/services/zemax-opticstudio-consulting), [Stray light and non-sequential simulation](https://www.formlightoptics.com/services/stray-light-and-non-sequential-simulation).