A refractive index sensor based on a multi-core micro/nano fiber is proposed for low refractive index solutions. At first, the mode field distribution of the tapered multi-core fiber is analyzed with the finite elemen...A refractive index sensor based on a multi-core micro/nano fiber is proposed for low refractive index solutions. At first, the mode field distribution of the tapered multi-core fiber is analyzed with the finite element model (FEM). After that, the relationship between the refractive index sensitivity and the diameter of the multi-core micro/nano fiber is calculated. At last, four sensors with different sizes are explored, and when the taper length is 16.20 mm, the refractive index sensitivity of the sensor can reach 5815.50nm/RIU, which agrees with the theoretical analysis. The refractive index measurement error is less than 0.5 %o, which has a high practical application value. The longer the taper length is, the smaller the fiber diameter is. According to the theoretical analysis, when the fiber diameter is less than 4.864 gm, the structure sensor\ refractive index sensitivity is higher than 10000 nm/RIU. At the same time, when the sensor's taper length is 15.99 mm, its temperature sensitivity is -0.1084nm/°C. Compared with single-mode fiber, the sensor proposed here has the advantages of stability, compact structure, and high sensitivity, which has a potential in the field of seawater salinity measurement.展开更多
Based on the transverse electro-optic effect of lithium niobate crystal,combined with polarizers and Faraday rotator,this paper presents a collinear closed-loop fiber optic current transformer with spatial non-recipro...Based on the transverse electro-optic effect of lithium niobate crystal,combined with polarizers and Faraday rotator,this paper presents a collinear closed-loop fiber optic current transformer with spatial non-reciprocity modulation method,and the feasibility of the scheme is verified by both the theoretical and experimental evidences.The detection scheme avoids the limitation of the transition time of the sensing fiber coil on the phase modulation frequency,improves the sensitivity and stability of the system,and reduces the volume and cost of fiber optic current transformer.The sawtooth wave modulation scheme is adopted to realize phase bias modulation and feedback modulation through phase shift of sawtooth wave to achieve closed-loop detection effect,which enhances the signal to noise ratio and simplifies demodulation mode.The experimental results show that the current ratio errors measured at room temperature range from 1%to 120%of rated current meet the requirements of national standard GB/T 20840.8-2007 and reach the accuracy level of 0.2S.The temperature stability of the current transformer is also tested,and the ratio error measured at the rated current does not exceed±0.2%in the range of-30℃to 50℃.展开更多
基金the National Natural Science Foundation of China (Grant Nos. 61735011 and 61405173)the Hebei Province Natural Science Foundation of China (Grant Nos. F2016203389 and C2015003053)+1 种基金the Natural Science Foundation of the Xinjiang Uygur Autonomous Region (Grant No. 2018D01A25)the Project Supported by Science and Technology Program of Hebei Province for Institutions of Higher Education (Grant No. ZD2017082).
文摘A refractive index sensor based on a multi-core micro/nano fiber is proposed for low refractive index solutions. At first, the mode field distribution of the tapered multi-core fiber is analyzed with the finite element model (FEM). After that, the relationship between the refractive index sensitivity and the diameter of the multi-core micro/nano fiber is calculated. At last, four sensors with different sizes are explored, and when the taper length is 16.20 mm, the refractive index sensitivity of the sensor can reach 5815.50nm/RIU, which agrees with the theoretical analysis. The refractive index measurement error is less than 0.5 %o, which has a high practical application value. The longer the taper length is, the smaller the fiber diameter is. According to the theoretical analysis, when the fiber diameter is less than 4.864 gm, the structure sensor\ refractive index sensitivity is higher than 10000 nm/RIU. At the same time, when the sensor's taper length is 15.99 mm, its temperature sensitivity is -0.1084nm/°C. Compared with single-mode fiber, the sensor proposed here has the advantages of stability, compact structure, and high sensitivity, which has a potential in the field of seawater salinity measurement.
基金This work was supported by the National Natural Science Foundation of China(Grant No.61735011)the Science and the Key Research and Development Program of Hebei Province(Grant No.19251703D)the Local Science and Technology Development Projects of the Central Committee(Grant No.19941708G).
文摘Based on the transverse electro-optic effect of lithium niobate crystal,combined with polarizers and Faraday rotator,this paper presents a collinear closed-loop fiber optic current transformer with spatial non-reciprocity modulation method,and the feasibility of the scheme is verified by both the theoretical and experimental evidences.The detection scheme avoids the limitation of the transition time of the sensing fiber coil on the phase modulation frequency,improves the sensitivity and stability of the system,and reduces the volume and cost of fiber optic current transformer.The sawtooth wave modulation scheme is adopted to realize phase bias modulation and feedback modulation through phase shift of sawtooth wave to achieve closed-loop detection effect,which enhances the signal to noise ratio and simplifies demodulation mode.The experimental results show that the current ratio errors measured at room temperature range from 1%to 120%of rated current meet the requirements of national standard GB/T 20840.8-2007 and reach the accuracy level of 0.2S.The temperature stability of the current transformer is also tested,and the ratio error measured at the rated current does not exceed±0.2%in the range of-30℃to 50℃.
