Ultrahigh resolution optical fiber strain sensor using dual Pound-Drever-Hall feedback loops

Area of Science:

• Optics and Photonics
• Sensor Technology
• Materials Science

Background:

• Traditional static strain sensors have limitations in resolution and sensing bandwidth.
• High-resolution, broad-bandwidth strain sensing is crucial for advanced applications, particularly in geophysics.
• Existing fiber optic sensors often struggle to meet the demanding requirements for dynamic strain measurements.

Purpose of the Study:

• To develop and demonstrate an ultrahigh resolution optical fiber strain sensor.
• To achieve a broad frequency range for strain measurements, from quasi-static to several hundred hertz.
• To significantly improve upon the resolution and sensing bandwidth of conventional strain sensors.

Main Methods:

• Utilized a π-phase shifted fiber Bragg grating for strain sensing.
• Incorporated a fiber Fabry-Perot interferometer as a reference element.
• Employed the Pound-Drever-Hall technique within two feedback loops to lock laser carrier and sideband to the sensing and reference elements, respectively.
• Achieved a sampling rate up to 500 samples/s, limited only by the frequency counter's update rate.

Main Results:

• Demonstrated an ultrahigh resolution optical fiber strain sensor.
• Achieved a strain resolution better than 0.01 nϵ at 10 Hz within a 0.01-250 Hz bandwidth, exhibiting a 1/f characteristic.
• Obtained a wide dynamic range of up to 149 dB.
• Showcased a broad frequency response from quasi-static to several hundred hertz.

Conclusions:

• The proposed optical fiber strain sensor offers significant improvements in both resolution and sensing bandwidth compared to traditional static sensors.
• The sensor's high performance makes it a powerful tool for geophysical applications requiring precise and wide-ranging strain measurements.
• This technology advances the capabilities of fiber optic sensing for demanding scientific and industrial fields.