Four-core optical fiber as a calorimetric gauge

Area of Science:

• Optical Physics
• Heat Transfer
• Materials Science

Background:

• Accurate measurement of transient heat transfer is crucial in various scientific and engineering fields.
• Traditional calorimetric methods can be complex and limited in spatial resolution.
• Optical fiber sensors offer potential for non-invasive and high-resolution thermal measurements.

Purpose of the Study:

• To demonstrate a four-core optical fiber as a calorimetric gauge for one-dimensional heat transfer measurements.
• To investigate the feasibility of using laser-induced thermal effects in optical fibers for quantitative heat analysis.
• To establish a method for measuring heat flux and temperature rise using optical fiber interferometry.

Main Methods:

• A four-core optical fiber was used as the sensing element.
• Transient heat pulses were delivered to one core of the fiber using a Nd:YAG laser.
• Temperature-induced changes in refractive index and physical length caused an optical path length difference.
• Interferometric fringe pattern shifts were monitored using a CMOS camera in a reflection scheme.

Main Results:

• A phase shift of 0.43±0.015 radians was measured for 40 mW laser pulses.
• The thermal heat diffusion length in the fiber core was determined to be 2.8 mm.
• The measured heat flux was 10.9±0.38 kJ/m²s.
• A temperature rise of 1.43±0.05 K was observed in the targeted fiber core.

Conclusions:

• The four-core optical fiber functions effectively as a calorimetric gauge for heat transfer.
• The developed method allows for quantitative measurement of transient heat pulses and thermal properties.
• This technique offers a promising approach for non-contact, high-sensitivity thermal measurements.