Highly Sensitive Strain Sensor by Utilizing a Tunable Air Reflector and the Vernier Effect.

Area of Science:

• Fiber optics
• Optical sensing
• Interferometry

Background:

• Fabry-Perot interferometers (FPIs) are widely used in optical sensing.
• Enhancing the sensitivity of FPI-based sensors is crucial for advanced applications.
• Cross-talk from environmental factors like temperature can limit strain sensor accuracy.

Purpose of the Study:

• To propose and experimentally demonstrate a highly sensitive strain sensor.
• To utilize tunable cascaded FPIs and the Vernier effect (VE) for enhanced strain detection.
• To achieve high resolution and low temperature sensitivity in strain sensing.

Main Methods:

• Fabrication of a sensing FPI using a hollow core fiber (HCF) segment between single-mode fibers (SMFs).
• Construction of a reference FPI with a tunable air reflector controlled by a programmable fiber holder.
• Experimental validation of the cascaded FPI sensor's performance across a 1530 nm to 1610 nm bandwidth.

Main Results:

• The cascaded FPI sensor demonstrated optimum strain sensitivities of 23.9 pm/με, 17.54 pm/με, and 14.11 pm/με for different reference FPI cavity lengths.
• Achieved strain sensitivities were 8.10 to 13.73 times higher than that of a single sensing FPI (1.74 pm/με).
• Ultra-low temperature sensitivity of 0.49 pm/°C was observed, ensuring effective isolation from temperature-strain cross-talk.

Conclusions:

• The tunable cascaded FPI sensor offers a significant improvement in strain sensitivity.
• The sensor's design provides excellent temperature-strain cross-talk isolation.
• The proposed sensor is a promising candidate for high-resolution, robust, and cost-effective strain sensing applications.