In-Fiber Collimator-Based Fabry-Perot Interferometer with Enhanced Vibration Sensitivity.

Area of Science:

• Photonics and Optical Engineering
• Sensor Technology
• Fiber Optics

Background:

• Optical fiber sensors offer advantages for remote and harsh environment monitoring.
• Fabry-Perot interferometers (FPIs) are sensitive optical devices.
• Improving the sensitivity and robustness of FPI-based sensors is crucial for practical applications.

Purpose of the Study:

• To propose and demonstrate a simple, highly-sensitive vibration sensor based on an optical fiber FPI.
• To investigate the impact of an in-fiber collimator on the FPI sensor's static and dynamic performance.
• To evaluate the sensor's potential for vibration monitoring in remote and harsh environments.

Main Methods:

• Fabrication of an FPI sensor by splicing single mode fibers (SMFs), a hollow-core fiber (HCF), and a quarter-pitch graded index fiber (GIF) with an in-fiber collimator.
• Characterization of the static displacement sensitivity of the FPI with and without the collimator.
• Measurement of vibration sensitivity at 100 Hz and across a frequency range of 40–200 Hz.

Main Results:

• The FPI with an in-fiber collimator achieved a static displacement sensitivity of 5.17 × 10^-4 μm^-1, significantly higher than without the collimator (1.73 × 10^-4 μm^-1).
• Vibration sensitivity was markedly improved with the collimator (60.22 mV/g at 100 Hz) compared to the device without (11.09 mV/g at 100 Hz).
• The proposed sensor demonstrated nearly one order of magnitude higher vibration sensitivity across the tested frequency range.

Conclusions:

• The integration of an in-fiber collimator substantially enhances the static and vibration sensitivity of the optical fiber FPI sensor.
• The developed sensor is low-cost, highly-sensitive, robust, and easy to fabricate.
• This FPI sensor shows significant potential for effective vibration monitoring in demanding and inaccessible locations.