Parallel Cross-Correlation Algorithm for the Fast Interrogation of High-Finesse Fiber-Optic Fabry-Perot Sensors

It is still a challenge to realize the absolute optical path difference (OPD) demodulation of the high-finesse fiber-optic Fabry-Perot (FP) sensors with a high resolution and high speed. This paper proposes an improved parallel cross-correlation (PCC) algorithm for the absolute OPD interrogation of the high-finesse FP sensors. The proposed demodulation algorithm is simulated and analyzed to verify the feasibility of the algorithm for sensors with different reflectivity or OPDs with large dynamic range. A high-finesse fiber-optic FP pressure sensor with a cavity length of about 1500 μm and reflectivity of 62.5% has been used to carry out the experiment. Results show that the measurement resolution of the PCC algorithm can reach the sub-nanometer level, the sensor's sensitivity is about 3.93 nm/KPa, which is similar to the theoretical value. By exploring the effect of reflectivity on the demodulation results, it is found out that accurate results are still obtainable even though the exact reflectivity is unknown. In addition, thanks to the multi-threading of computers and the parallel computing method proposed in this paper, the demodulation speed would be further improved.