Research On Polarized Low Coherence Interferometer And Demodulation Method Based On A Matrix CCD

Since the 1970 s,optical fiber sensing technology began to rise,and became a hot research at home and abroad.In addition to the rapid development of optical fiber sensors,the demodulation technology has also been widespread concerned and researched.The low-coherence interference demodulation method has become an important technique to measure the absolute optical path.This technique is widely used in optical coherence tomography,three-dimensional profiling and displacement sensing applications.In this paper,the problem of traditional polarized low-coherence interferometer in optical fiber sensing is improved,and a two-dimensional polarized low-coherence interferometer based on based on a matrix CCD is proposed.By which we can obtain a wide measurement range and guarantee low measurement deviation and high resolution.The presented system is then successfully applied to displacement and pressure measurement.The finished works are as follows:1?An electronically scanned polarized low-coherence interferometer based on a matrix charge-coupled-device and birefringence crystal with a two-dimensional angle is proposed.The simplified mathematical model is used to derive the two-dimensional polarized low-coherence interference demodulation method in detail.Birefringence crystal with a two-dimensional angle is designed.According to the distribution of the two-dimensional interference signal in the horizontal and vertical directions,a two-step demodulation algorithm is proposed.2?The two-dimensional polarized low-coherence interferometer based on a matrix charge-coupled-device is built and demonstrated.By using a sensing interferometer composed of the fiber end face and the glass surface,the proposed system is applied to displacement measurement.The two-dimensional interference fringes are captured and comprehensive demodulated by the two-step demodulation algorithm.The experimental results showed that,the proposed system significantly expanded the dynamic range(reach ~101dB),and meanwhile ensured low measurement deviation(kept within ± 7 nm)and high resolution(2.52 nm).3?By using the self-made fiber optic Fabry-Perot pressure sensor and the self-built atmospheric pressure testing system,the proposed system and demodulation algorithm are further validated through pressure experiment.The experimental results show that the pressure measurement error is maintained at ± 0.22 kPa and can reach 0.147% F.S in the measurement range of 3~153kPa.