For the cavity length demodulation of fiber-optic Fabry-Perot (FP) sensors, a frequency-doubled self-correlation algorithm was proposed. Since the frequency doubling can make the self-correlation peak sharper, the peak positioning accuracy can be effectively improved for the cavity length extraction. The feasibility and performances of the proposed algorithm was investigated by both simulation and experiment. The simulated demodulation accuracy was better than 1.9 nm. The experimental demodulation resolution for a fiber-optic FP stress sensor with an initial cavity length of 79.859 mu m reached 4.32 nm.
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