Effects of the phase shift split on distributed-feedback (DFB) fiber Bragg gratings
Bibliographic record
Abstract
When a fiber Bragg grating (FBG) is fabricated with the proximity side-writing technique using a phase shifted phase mask, the phase shifts in the phase mask are split into two half-amplitude phase shifts. In this paper, we investigate the effects of the phase shift-split on the DFB grating, which has a single π-phase shift at mid-length. The split of the phase shift produces a slight blue-shift of the transmission peak of the DFB grating and creates spectral asymmetry errors. We model the split-phase shifted FBG as two cascaded and tightly coupled grating-based Fabry-Perot filters, and obtain a compact expression of the reflectivity spectrum with the transfer-matrix approach. The theory is able to describe the spectral asymmetry errors and the shift of the transmission peak and to show that the effects of the phase shift-split decrease with increasing FBG length and become negligible for gratings more than a few millimeters long.
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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 | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".