Through analyzing theoretically the temperature effect of the optical-fiber Raman backscattering,a distributed temperature sensor is designed based on the single-mode fiber. Demodulation methods of temperature transdu...Through analyzing theoretically the temperature effect of the optical-fiber Raman backscattering,a distributed temperature sensor is designed based on the single-mode fiber. Demodulation methods of temperature transduction are compared,and then the demodulation method using the ratio of the anti-Stokes and the Stokes Raman backscattering intensity is adopted. Both the hardware composition and the software realization of the system are introduced in detail. The experiment shows that the distinguishing ability of the temperature and that of the space are 1℃ and 2m,respectively,and that the system response time is about 180 s with a sensing range of 5km and with a temperature measurement range of 0-100℃.展开更多
To overcome the invalid phase and phase jump phenomenon generated during the phase unwrapping, a phase error correction method based on the Gaussian filtering algorithm and intensity variance is proposed in this paper...To overcome the invalid phase and phase jump phenomenon generated during the phase unwrapping, a phase error correction method based on the Gaussian filtering algorithm and intensity variance is proposed in this paper. First, a threshold of fringe intensity variance is set to identify and clear the phase in the invalid region. Then, the Gaussian filtering algorithm is employed to correct the phase order at the fringe junction, and then the absolute phase is corrected. Finally, the phase correction experiments of different geometric objects are carried out to verify the feasibility and accuracy of the proposed method. The method proposed in this paper can be extended to the correction of absolute phase error obtained by any coding method.展开更多
In this paper, to reduce the non-linear phase error caused by gamma effect of the digital projector, a novel phase difference extraction method is proposed. First, through multi-layer discrete wavelet decomposition(DW...In this paper, to reduce the non-linear phase error caused by gamma effect of the digital projector, a novel phase difference extraction method is proposed. First, through multi-layer discrete wavelet decomposition(DWT), the components of the original phase difference at different frequencies are extracted. Subsequently, the effective components are taken by the orthogonal matching pursuit(OMP) algorithm, and the phase difference is reconstructed. According to the upper and lower envelopes of the original phase difference extracted by cubic spline interpolation, the residual threshold of OMP is set. According to the results of three-dimensional(3-D) reconstruction experiment on a standard sphere, the proposed method is capable of reducing the errors in the original phase difference and achieving a better imaging result.展开更多
When a structure material is damaged by impact events, the reliability and lifetime of the material will be severely af- fected. So impact location is considered as the prime approach for structural health and damage ...When a structure material is damaged by impact events, the reliability and lifetime of the material will be severely af- fected. So impact location is considered as the prime approach for structural health and damage monitoring. In this study, a novel fiber Bragg grating （FBG） impact location system based on broadband light source is designed, aiming at the shortcoming of existing location systems based on FBG. An improved localization algorithm based on the time difference of arrival （TDoA） is proposed for impact location. According to this algorithm, the impact position can be accurately predicted without wave velocity. Impact planar location experiments are carried out for verification of the FBG impact location system and algorithm on a 400 mmx400 mmx3 mm aluminum alloy plate. The resulted locating error shows high precision and good stability of the proposed system.展开更多
基金Shandong Province Natural Science Foundation (No.Z2006G06)The Excellent Youth Scientist Award Foundation of Shandong Province (No.2006 BS 01001)
文摘Through analyzing theoretically the temperature effect of the optical-fiber Raman backscattering,a distributed temperature sensor is designed based on the single-mode fiber. Demodulation methods of temperature transduction are compared,and then the demodulation method using the ratio of the anti-Stokes and the Stokes Raman backscattering intensity is adopted. Both the hardware composition and the software realization of the system are introduced in detail. The experiment shows that the distinguishing ability of the temperature and that of the space are 1℃ and 2m,respectively,and that the system response time is about 180 s with a sensing range of 5km and with a temperature measurement range of 0-100℃.
基金supported by the National Natural Science Foundation of China(Nos.61873333 and 61903225)the Fundamental Research Funds of Shandong University in China(No.2018JCG06)+3 种基金the Shandong Provincial Natural Science Foundation in China(Nos.ZR2017PEE023 and ZR2017BF007)the National Key Research and Development Project(No.2018YFE02013)the Key Research and Development Plan of Shandong Province(No.2019TSLH0301)the Young Scholars Program of Shandong University(No.2016WLJH30)。
文摘To overcome the invalid phase and phase jump phenomenon generated during the phase unwrapping, a phase error correction method based on the Gaussian filtering algorithm and intensity variance is proposed in this paper. First, a threshold of fringe intensity variance is set to identify and clear the phase in the invalid region. Then, the Gaussian filtering algorithm is employed to correct the phase order at the fringe junction, and then the absolute phase is corrected. Finally, the phase correction experiments of different geometric objects are carried out to verify the feasibility and accuracy of the proposed method. The method proposed in this paper can be extended to the correction of absolute phase error obtained by any coding method.
基金This work has been supported by the National Natural Science Foundation of China(No.61873333)the Fundamental Research Funds of Shandong University in China(No.2018JCG06)+3 种基金the Shandong Provincial Natural Science Foundation of China(Nos.ZR2017PEE023 and ZR2017BF007)the National Key Research and Development Project(No.2018YFE02013)the Key Research and Development Plan of Shandong Province(No.2017CXGC0610)the Young Scholars Program of Shandong University(No.2016WLJH30).
文摘In this paper, to reduce the non-linear phase error caused by gamma effect of the digital projector, a novel phase difference extraction method is proposed. First, through multi-layer discrete wavelet decomposition(DWT), the components of the original phase difference at different frequencies are extracted. Subsequently, the effective components are taken by the orthogonal matching pursuit(OMP) algorithm, and the phase difference is reconstructed. According to the upper and lower envelopes of the original phase difference extracted by cubic spline interpolation, the residual threshold of OMP is set. According to the results of three-dimensional(3-D) reconstruction experiment on a standard sphere, the proposed method is capable of reducing the errors in the original phase difference and achieving a better imaging result.
基金supported by the National Natural Science Foundation of China(Nos.61503218,61403233,61573226 and 61473176)the Excellent Young and Middle-Aged Scientist Award Grant of Shandong Province of China(No.BS2013DX018)the Natural Science Foundation of Shandong Province for Outstanding Young Talents(No.ZR2015JL021)
文摘When a structure material is damaged by impact events, the reliability and lifetime of the material will be severely af- fected. So impact location is considered as the prime approach for structural health and damage monitoring. In this study, a novel fiber Bragg grating （FBG） impact location system based on broadband light source is designed, aiming at the shortcoming of existing location systems based on FBG. An improved localization algorithm based on the time difference of arrival （TDoA） is proposed for impact location. According to this algorithm, the impact position can be accurately predicted without wave velocity. Impact planar location experiments are carried out for verification of the FBG impact location system and algorithm on a 400 mmx400 mmx3 mm aluminum alloy plate. The resulted locating error shows high precision and good stability of the proposed system.
