Highly precise in-plane displacement sensor based on an asymmetric fiber Fabry-Perot interferometer

Area of Science:

• Optoelectronics
• Optical Metrology
• Fiber Optic Sensors

Background:

• Accurate in-plane displacement measurement is crucial for precision engineering.
• Existing sensors often face limitations in sensitivity, resolution, or noise suppression.
• Fiber optic sensors offer advantages like miniaturization and immunity to electromagnetic interference.

Purpose of the Study:

• To propose and demonstrate a novel in-plane displacement sensor.
• To leverage an asymmetric extrinsic fiber Fabry-Perot interferometer (EFPI) for enhanced performance.
• To achieve high sensitivity and suppressed common-mode noise in displacement sensing.

Main Methods:

• Design and fabrication of an asymmetric EFPI using a step-shaped reflector and cleaved fiber.
• Theoretical analysis of the interferometer's optical characteristics.
• Experimental validation of displacement demodulation based on peak intensity differences.

Main Results:

• The asymmetric EFPI behaves as two parallel FPIs with slightly different cavity lengths.
• In-plane displacement is demodulated by calculating the peak intensity difference.
• Achieved a displacement resolution of 5 nm and a linear range of ±7µm with a 250 µm cavity length.
• Demonstrated sensitivity and linear range dependence on cavity length.

Conclusions:

• The proposed asymmetric EFPI sensor offers enhanced sensitivity and suppressed common-mode noise.
• The sensor exhibits nanometric resolution and a compact size.
• Potential applications include metrology, accelerometers, and semiconductor manufacturing.