Ultra-compact directional curvature sensor using an asymmetric fiber-optic microbubble Fabry-Perot interferometer

Area of Science:

• Optoelectronics
• Fiber Optics
• Sensor Technology

Background:

• Fiber-optic sensors are crucial for remote and precise measurements.
• Existing sensors often lack directional sensitivity or are bulky.
• Asymmetric structures offer potential for enhanced directional sensing capabilities.

Purpose of the Study:

• To develop a fiber-optic directional curvature sensor with enhanced sensitivity and specificity.
• To investigate the mechanism of directional sensing in an asymmetric microbubble Fabry-Perot interferometer (AMFPI).
• To evaluate the sensor's performance in terms of sensitivity, range, and environmental resilience.

Main Methods:

• Fabrication of a tapered optical fiber with an embedded asymmetric microbubble Fabry-Perot interferometer (AMFPI).
• Utilizing asymmetric light incidence to induce asymmetrical displacement of reflection points within the spherical cavity.
• Analyzing spectral shifts (redshift/blueshift) to determine bending direction and magnitude.
• Engineering radial wall thickness asymmetry to enhance directional sensitivity.

Main Results:

• Achieved high directional curvature sensitivity of 1.06 nm/m^-1 over a range of 0-4.35 m^-1.
• Demonstrated distinct spectral shifts corresponding to bending direction due to modulated optical path difference (OPD).
• Exhibited negligible sensitivity to ambient refractive index variations and low thermal sensitivity (1.09 pm/°C).

Conclusions:

• The AMFPI sensor offers precise directional curvature detection.
• Its compact size and robustness make it suitable for harsh environments like biological fluids.
• The sensor's unique design overcomes limitations of traditional fiber-optic curvature sensors.