Frd Optical Fibre Testing

---
name: frd-optical-fibre-testing
description: Evaluates the focal ratio degradation (FRD) of multi-mode optical fibres under automated testing conditions to verify compliance with astronomical instrumentation specifications. It compares automated optical bench measurements against manual ring tests to ensure measurement consistency and accuracy. Use when the user has predictions and gold and needs to compute FRD (Focal Ratio Degradation).
metadata:
  skill_kind: metric
  source_arxiv: 1807.09182
  bibtex_key: monty2018automated
  confidence: high
---

# frd-optical-fibre-testing

> Automated testing of optical fibres: towards the design of the Maunakea Spectroscopic Explorer Fibre Transmission System — Monty et al. (2018) (arXiv:1807.09182, 2018)

## What this evaluates

Evaluates the focal ratio degradation (FRD) of multi-mode optical fibres under automated testing conditions to verify compliance with astronomical instrumentation specifications. It compares automated optical bench measurements against manual ring tests to ensure measurement consistency and accuracy.

## Datasets

- **MSE candidate GRACES fibre** — total 1; splits: (unstated)

## Metrics

- `FRD (Focal Ratio Degradation)` **(primary)** — range: percent
  - FRD is expressed as a percentage, derived from the ratio of the output f-number to the input f-number at the fibre. The system targets an FRD of less than 5% at f/2, with a measured value of 3.7% reported.

## Input / output format

**Input**: Collimated optical beam injected into the fibre at specific incident angles (-14° to -8° and 8° to 14°) via the Big FFW automated test bench.

**Output**: Measured output f/# and calculated FRD percentage at the fibre output, compared against manual ring test results.

## Scoring recipe

```python
1. Inject collimated beam at target incident angle.
2. Measure output f/# at 95% encircled energy.
3. Calculate FRD percentage from input/output f/# ratio.
4. Compare automated FRD against manual FRD.
5. Compute max disagreement; must be < 0.5% (systematic error threshold).
6. Verify FRD < 5% at f/2 to meet science requirement.
```

## Common pitfalls

- Calibration zero-point errors can skew incident angle symmetry and FRD calculations.
- Manual and automated measurements must be compared within the 0.5% systematic error margin to avoid false discrepancies.

## Evidence (verbatim from paper)

> FRD-proxy measurements were made for 14 different incident angles (-14∘ to -8∘, and 8∘ to 14 ∘), with the results shown in Fig.[5](#S4.F5 "Figure 5 ‣ 4 INITIAL RESULTS OF MSE-LIKE FIBRE CHARACTERIZATION ‣ Automated testing of optical fibres: towards the design of the Maunakea Spectroscopic Explorer Fibre Transmission System"). The current results suggest that we have met the science requirement of the MSE project (i.e. FRD of 3.7% at f/2, which is well within 5% science requirement of the MSE project). Additionally, the FRD of the MSE candidate GRACES fibre was determined manually and compared against the results determined by the Big FFW (see Fig.[6](#S4.F6 "Figure 6 ‣ 4 INITIAL RESULTS OF MSE-LIKE FIBRE CHARACTERIZATION ‣ Automated testing of optical fibres: towards the design of the Maunakea Spectroscopic Explorer Fibre Transmission System")). We find the maximum disagreement between results from the Big FFW and the manual Ring Test to be less than the systematic error in our analysis (i.e. systematic error of 0.5%).

## Citation

```bibtex
@misc{monty2018automated,
  title={Automated testing of optical fibres: towards the design of the Maunakea Spectroscopic Explorer Fibre Transmission System},
  author={Monty et al. (2018)},
  year={2018},
  note={arXiv:1807.09182}
}
```

- arXiv: 1807.09182