Dual-mode fiber-optic refractive-index gas thermometry with primary anchoring and continuous temperature tracking.

Authors

Musaddeque Syed, Ming Han

Published in

Optics letters. Volume 51. Issue 17. Pages 4956-4959. Sep 01, 2026.

Abstract

Extending fiber-optic refractive-index gas thermometry beyond primary-only operation, we report a dual-mode argon-filled Fabry-Perot thermometer in which the same cavity first establishes a primary temperature anchor and then performs continuous secondary-mode tracking. The primary anchor is obtained from two-pressure fringe shifts using a virial-coefficient refractivity model. During secondary operation, pressure cycling is stopped, and temperature is recovered from the monitored fringe wavelength and gas pressure using a model that includes argon refractivity, pressure-induced cavity strain, and fused-silica thermal expansion. From 310 to 1013 K, secondary-mode temperatures agreed with a reference thermocouple with 0.21 K RMSE and 0.47 K maximum error; 45-min natural furnace cooldowns were also tracked from nearby anchors with close agreement. The dual-mode method retains the empirical-calibration-free primary measurement as an in-situ reference while enabling simpler continuous tracking between anchors, addressing a practical limitation of primary-only fiber-optic refractive-index gas thermometry for high-temperature applications.

PMID:
42679289
Bibliographic data and abstract were imported from PubMed on 02 Sep 2026.

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