A distributed fiber sensor was fabricated by splicing two single-mode fibers(SMFs)using the few-mode fiber(FMF)technique.A Brillouin optical time domain analysis(BOTDA)system was developed to measure the sensor’s tem...A distributed fiber sensor was fabricated by splicing two single-mode fibers(SMFs)using the few-mode fiber(FMF)technique.A Brillouin optical time domain analysis(BOTDA)system was developed to measure the sensor’s temperature and bending performance.Two-mode and four-mode step FMFs were combined to splice the few-mode segment.The results indicate that the temperature response coefficients of the few-mode segment are only slightly higher than those of the connected single-mode segment,measuring at 1.13 MHz/℃and 1.12 MHz/℃,respectively.The minimum bending radius for the sensor is 0.9 cm,and the four-mode bending response curve is superior to that of the two-mode one,proving that 4-SI-FMF offers better bending sensitivity.展开更多
In this paper,the influence of laser wavelength instability,polarization fading and phase fluctuation on local heterodyne detection wavelength scanning Brillouin optical time domain reflectometer(WS-BOTDR)is theoretic...In this paper,the influence of laser wavelength instability,polarization fading and phase fluctuation on local heterodyne detection wavelength scanning Brillouin optical time domain reflectometer(WS-BOTDR)is theoretically analyzed,and a local heterodyne detection WS-BOTDR system is built for experimental verification.The experimental results show that with the increase of sensing distance,the adverse effect of laser wavelength instability,polarization fading and phase fluctuation on local heterodyne detection WS-BOTDR is gradually aggravated,which will lead to the broadening and distortion of the wavelength power spectrum(WPS),resulting in large errors in demodulated Brillouin central wavelength(BCW)and temperature.The average temperature measurement errors at the positions of 1 km,5 km,9 km non-heating section and 9.45 km heating section are 1.76℃,3.42℃,3.89℃and 4.3℃,respectively.展开更多
A simple and inexpensive sensing structure,single mode fiber(SMF)alignment fusion to 62.5μm stepped index-multimode fiber(SI-MMF),combined with Brillouin optical time domain reflectometry(BOTDR)system,is used as a di...A simple and inexpensive sensing structure,single mode fiber(SMF)alignment fusion to 62.5μm stepped index-multimode fiber(SI-MMF),combined with Brillouin optical time domain reflectometry(BOTDR)system,is used as a distributed sensor in the field of structural safety and health monitoring(SSHM)of large infrastructures in terms of its prominent bending resistance.The bend loss principle and influencing factors of the fiber are analyzed,and the bending resistances of different fibers are discussed on the basis of theoretical and experimental comparisons.The bend-tolerant capacity and temperature sensing characteristics of the 5 km sensing structure are measured by using the self-developed frequency-shifted local heterodyne BOTDR system.The results show that the proposed sensing structure has excellent bend-tolerant capacity with a minimum bend radius and temperature measurement error of 1.25 mm and 0.69℃,respectively,which indicates that the proposed sensing structure has huge potential in the field of SSHM of large infrastructures.展开更多
基金The National Natural Science Foundation of China(Nos.21773012,U2032112,21572234,21661132006,91833304,21905163)National Key Research and Development Program of China(Nos.2019YFA0705900,2017YFA0204701)。
基金supported by the National Science Foundation for Distinguished Young Scholars(No.62205105)the National Natural Science Foundation of China(Nos.61775057,52177141 and 62171185)。
文摘A distributed fiber sensor was fabricated by splicing two single-mode fibers(SMFs)using the few-mode fiber(FMF)technique.A Brillouin optical time domain analysis(BOTDA)system was developed to measure the sensor’s temperature and bending performance.Two-mode and four-mode step FMFs were combined to splice the few-mode segment.The results indicate that the temperature response coefficients of the few-mode segment are only slightly higher than those of the connected single-mode segment,measuring at 1.13 MHz/℃and 1.12 MHz/℃,respectively.The minimum bending radius for the sensor is 0.9 cm,and the four-mode bending response curve is superior to that of the two-mode one,proving that 4-SI-FMF offers better bending sensitivity.
基金supported by the National Natural Science Foundation of China(Nos.52177141,62171185 and 61775057)the Natural Science Foundation of Hebei Province of China(Nos.F2019502112 and E2020502010)+1 种基金the Fundamental Research Funds for the Central Universities(Nos.2019MS086 and 2017MS112)the S&T Program of Hebei,China(No.SZX2020034)。
文摘In this paper,the influence of laser wavelength instability,polarization fading and phase fluctuation on local heterodyne detection wavelength scanning Brillouin optical time domain reflectometer(WS-BOTDR)is theoretically analyzed,and a local heterodyne detection WS-BOTDR system is built for experimental verification.The experimental results show that with the increase of sensing distance,the adverse effect of laser wavelength instability,polarization fading and phase fluctuation on local heterodyne detection WS-BOTDR is gradually aggravated,which will lead to the broadening and distortion of the wavelength power spectrum(WPS),resulting in large errors in demodulated Brillouin central wavelength(BCW)and temperature.The average temperature measurement errors at the positions of 1 km,5 km,9 km non-heating section and 9.45 km heating section are 1.76℃,3.42℃,3.89℃and 4.3℃,respectively.
基金supported by the National Natural Science Foundation of China(Nos.61775057 and 51607066)the Natural Science Foundation of Hebei Province of China(Nos.F2019502112 and E2019502177)+1 种基金the Fundamental Research Funds for the Central Universities(Nos.2019MS086 and 2021MS071)the S&T Program of Hebei(No.SZX2020034)。
文摘A simple and inexpensive sensing structure,single mode fiber(SMF)alignment fusion to 62.5μm stepped index-multimode fiber(SI-MMF),combined with Brillouin optical time domain reflectometry(BOTDR)system,is used as a distributed sensor in the field of structural safety and health monitoring(SSHM)of large infrastructures in terms of its prominent bending resistance.The bend loss principle and influencing factors of the fiber are analyzed,and the bending resistances of different fibers are discussed on the basis of theoretical and experimental comparisons.The bend-tolerant capacity and temperature sensing characteristics of the 5 km sensing structure are measured by using the self-developed frequency-shifted local heterodyne BOTDR system.The results show that the proposed sensing structure has excellent bend-tolerant capacity with a minimum bend radius and temperature measurement error of 1.25 mm and 0.69℃,respectively,which indicates that the proposed sensing structure has huge potential in the field of SSHM of large infrastructures.
