Temperature-insensitive optical fiber strain sensor fabricated by two parallel connection Fabry-Perot interferometers...

Area of Science:

• Fiber Optic Sensors
• Interferometry
• Strain Sensing Technology

Background:

• Fabry-Perot interferometers (FPI) are optical sensors sensitive to external stimuli.
• Single-mode fiber (SMF) fabrication techniques enable micro-scale optical structures.
• Vernier effect enhances sensor sensitivity by combining multiple interferometers.

Purpose of the Study:

• To propose and demonstrate a novel strain sensor based on a parallel FPI configuration.
• To investigate the effect of air bubble size on FPI strain sensitivity.
• To enhance strain sensitivity using the Vernier effect and evaluate temperature cross-sensitivity.

Main Methods:

• Fabrication of FPIs using femtosecond laser processing of SMF to create micro air bubbles.
• Manufacturing FPIs with varying air bubble sizes (63, 78, and 93 µm).
• Parallel connection of FPIs to create Vernier effect strain sensors.

Main Results:

• FPIs exhibited strain sensitivities of 2.9, 2.0, and 1.5 pm/µε for decreasing air bubble sizes.
• Vernier effect strain sensors achieved sensitivities of -14.9 and -14.5 pm/µε, a 5.1x and 7.3x increase.
• The proposed sensors demonstrated extremely low temperature cross-sensitivity due to the air cavity FPIs.

Conclusions:

• Smaller air bubble FPIs yield higher strain sensitivity.
• Parallel FPI configuration with Vernier effect significantly amplifies strain sensitivity.
• The developed sensor offers high strain sensitivity and negligible temperature cross-sensitivity, suitable for precise measurements.