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

Abstract

A novel demodulation method is presented to expand the measurement dynamic range for fiber optic strain sensors using PDH technology. The new control algorithm uses two integrators to form a 2nd order control, and the FFPI strain sensor can have a dynamic range of 20 dB/octave larger than the PID control method when the input signal frequency decreases a magnitude. A strain resolution of 4.7 pɛ Hz−1/2@10Hz, a 118 dB@10Hz dynamic range without consecution, and 158 dB with consecution is obtained. The experiment results show that the new control method can improve the sensing system’s dynamic range with the corner frequency unchanged and without the system noise level degradation.