Fiber-optic extrinsic Fabry-Perot interferometer strain sensor with <50 pm displacement resolution using...

Area of Science:

• Optoelectronics
• Materials Science
• Sensor Technology

Background:

• Fiber-optic sensors offer non-destructive testing capabilities.
• Extrinsic Fabry-Perot interferometers (EFPIs) are suitable for precise measurements.
• Accurate strain measurement is critical in materials science and engineering.

Purpose of the Study:

• To demonstrate a fiber-optic extrinsic Fabry-Perot interferometer strain sensor (EFPI-S) with high displacement resolution.
• To measure the cross expansion of a PZT-ceramic plate using the developed sensor.
• To evaluate the sensor's performance with a three-wavelength digital phase demodulation method.

Main Methods:

• Fabrication of an EFPI-S with a 2.5 cm sensor length by fusing sensing and reflecting fibers within a capillary fiber.
• Implementation of an improved three-wavelength digital phase demodulation method with an arctan-phase stepping algorithm for readout.
• Varying strain sensitivity by mapping the arctan lookup table to a 16-Bit DAC range.

Main Results:

• Achieved <50 pm displacement resolution, corresponding to <2 nm/m strain resolution.
• Successfully measured the cross expansion of a PZT-ceramic plate.
• Demonstrated adjustable strain sensitivity from 188.25 kΩ/V to 11.7 kΩ/V.

Conclusions:

• The developed EFPI-S with three-wavelength digital phase demodulation provides high-resolution strain measurement.
• The sensor is effective for analyzing the mechanical behavior of materials like PZT-ceramic plates.
• The tunable sensitivity broadens the applicability of this fiber-optic sensing technology.