Improving the measurement range of FFPI strain sensing using second-order control PDH technology

Area of Science:

• Optoelectronics
• Sensor Technology
• Signal Processing

Background:

• Fiber optic sensors are crucial for precise strain measurement.
• Phase-generated carrier (PDH) technology is widely used in interferometric sensors.
• Expanding the dynamic range of these sensors remains a key challenge.

Purpose of the Study:

• To introduce a novel demodulation method for fiber optic strain sensors.
• To enhance the measurement dynamic range beyond conventional methods.
• To improve the performance of Fiber Fabry-Perot Interferometer (FFPI) strain sensors.

Main Methods:

• Development of a new control algorithm utilizing two integrators for 2nd order control.
• Application of the novel method to an FFPI strain sensor system.
• Comparison with Proportional-Integral-Derivative (PID) control methods.

Main Results:

• Achieved a strain resolution of 4.7 pɛ Hz^-1/2@10Hz.
• Obtained a dynamic range of 118 dB@10Hz (without consecution) and 158 dB (with consecution).
• Demonstrated a 20 dB/octave larger dynamic range compared to PID control at lower frequencies.

Conclusions:

• The novel demodulation method significantly expands the measurement dynamic range of fiber optic strain sensors.
• The new control strategy improves system performance without altering the corner frequency or increasing noise levels.
• This advancement offers enhanced capabilities for high-precision strain monitoring applications.