Fiber laser strain sensor based on an optical phase-locked loop

Area of Science:

• Photonics and Optical Sensing
• Metrology
• Geophysics

Background:

• Fiber laser sensors (FLS) are crucial for precise measurements.
• Existing interrogation techniques face limitations in strain resolution and noise performance.
• Advanced sensing methods are needed for sensitive geophysical applications.

Purpose of the Study:

• To present a novel fiber laser-based sensor (FLS) with enhanced strain resolution.
• To introduce a new optical phase-locked loop (OPLL) interrogation technique for FLS demodulation.
• To demonstrate the sensor's capability for high-precision strain measurement in geophysical research.

Main Methods:

• Utilized a distributed feedback (DFB) fiber laser as the master laser for strain sensing.
• Employed a fiber Fabry-Perot interferometer (FFPI) as a reference for laser carrier locking via PDH technique.
• Implemented an optical phase-locked loop (OPLL) technique with a root mean square detector (RMSD) for slave laser locking to the DFB sensing element.

Main Results:

• Achieved a high strain resolution of 8.19 pε/√Hz at 1 Hz and 35.5 pε in 10 s.
• Observed a 1/f noise distribution below 0.2 Hz, attributed to low pump power and active thermostat control.
• Demonstrated the effectiveness of the OPLL interrogation technique for FLS demodulation.

Conclusions:

• The novel OPLL interrogation technique significantly enhances strain resolution in FLS.
• The developed FLS demonstrates excellent performance for precise strain measurement.
• This sensor is a powerful tool with potential applications in geophysical research.