Frequency-shifted Mach-Zehnder interferometer for locating multiple weak reflections along a fiber link
Bibliographic record
Abstract
We propose and demonstrate a novel technique for measuring fiber lengths and locating multiple weak reflections along the fiber using a low-cost continuous wave source, a folded Mach-Zehnder interferometer (MZI), and a frequency shifter. By sweeping the frequency of the shifter, which is located in one path of the MZI, the optical length of the test fiber can be determined precisely from the interference pattern constructed by the reflected signals from the fiber end. Experimentally, for fibers shorter than 10 km, the standard deviations are less than 1 mm. Furthermore, by incorporating lock-in detection and fast Fourier transform techniques, both the locations and the reflectance of multiple reflection sites along one fiber can be resolved with a spatial resolution of about 5 m and a sensitivity better than -67dB. This could be a powerful interrogating technique for optical fiber sensor arrays.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".