Toward a practical fiber-optic primary thermometer for industrial applications

Area of Science:

• Metrology and Instrumentation
• Optical Physics
• Thermodynamics

Background:

• Accurate temperature measurement is crucial across scientific and industrial fields.
• Traditional thermometers face limitations in high-temperature environments and remote sensing.
• Refractive-index gas thermometry (RIGT) offers a potential pathway for primary thermometry.

Purpose of the Study:

• To develop and demonstrate a fiber-optic primary thermometer utilizing RIGT.
• To assess the performance of the developed thermometer from room temperature to 1073 K.
• To evaluate the repeatability and accuracy of the sensor compared to a reference thermocouple.

Main Methods:

• A Fabry-Pérot (FP) cavity integrated at the tip of a single-mode optical fiber was employed.
• Argon was used as the working gas for refractive-index measurements.
• Temperature was determined by analyzing FP wavelength shifts at two distinct pressure levels, employing a virial-coefficient model.

Main Results:

• Measurements from room temperature to approximately 1073 K showed agreement with a reference thermocouple within 1.0 K.
• The sensor exhibited excellent repeatability of approximately ±0.2 K at ~300 K.
• Repeatability increased to over ±1.0°C near 1073 K, demonstrating high-temperature capability.

Conclusions:

• The developed fiber-optic RIGT thermometer is a compact and high-temperature-capable primary thermometry solution.
• The sensor design shows significant promise for accurate temperature measurements in demanding industrial environments.
• This work advances the field of optical thermometry and its practical implementation.