We proposed a scheme of fiber Bragg grating （FBG） sensor interrogation system based on all fiber Mach-Zehnder Interferometer （MZI） edge filter and tunable-FBG. The equal power signals from FBG sensor and tunable F...We proposed a scheme of fiber Bragg grating （FBG） sensor interrogation system based on all fiber Mach-Zehnder Interferometer （MZI） edge filter and tunable-FBG. The equal power signals from FBG sensor and tunable FBG are coupled into port 1 and port 2 of MZI respectively. The experimental results show that the interrogation precision of the proposed system is 0.02 nm in a range of I nm. Furthermore, the precision can be improved by adjusting the two interference arms of the filter.展开更多
One of the problems in using grating sensors is how to measure a small Bragg wavelength shift accurately. Nowadays demodulation techniques are mainly based on the edge filter, tunable filter, or interferometric scanni...One of the problems in using grating sensors is how to measure a small Bragg wavelength shift accurately. Nowadays demodulation techniques are mainly based on the edge filter, tunable filter, or interferometric scanning methods. Interferometric demodulation is widely accepted as the technology which can provide the high sensitivity. An interrogation system using the interferometric scanning method is presented, in which an unbalanced fiber M-Z interferometer is used as the wavelength scanner for temperature measurement. A novel fiber Bragg grating sensor system based on M-Z interferometric demodulation technique is presented in this paper. The temperature sensitivity measured in the experiment is almost consistent with that obtained from the theoretic calculation.展开更多
A low fineness fiber optic Fabry-Perot interferometric displacement sensor has been developed and tested.A 0.005 nm displacement resolution is obtained by using He-Ne laser with a high performance ,photodetectors with...A low fineness fiber optic Fabry-Perot interferometric displacement sensor has been developed and tested.A 0.005 nm displacement resolution is obtained by using He-Ne laser with a high performance ,photodetectors with low noise ,low drift operational amplifiers,6-pole Butterworth filters and perfect digital signal processing circuits.展开更多
Due to the limitation of Edlen Equation to compensate for air refractivity in ordinary air pressure, an experiment to study the relationship between air refractivity and temperature, along with its pressure, is design...Due to the limitation of Edlen Equation to compensate for air refractivity in ordinary air pressure, an experiment to study the relationship between air refractivity and temperature, along with its pressure, is designed and carried out from ordinary pressure to low pressure. The expansion of Edlen Equation is achieved by using the cascade-Correlation learning method, and a neural network architecture model. The applied accuracy of neural network is the same as that of Edlen Equation in an ordinary pressure zone.展开更多
The theoretic analysis indicates that if the lengths of the cascaded and paralleled Fabry-Perot sensors are properly selected, the crosstalk can be well restricted.And the experiment simulation results agree with that...The theoretic analysis indicates that if the lengths of the cascaded and paralleled Fabry-Perot sensors are properly selected, the crosstalk can be well restricted.And the experiment simulation results agree with that of the theoretic analysis.展开更多
The method for measuring the strain of an object using an optical fiber and a frequency modulation(FM) coupled cavity semiconductor laser is proposed.This method uses the coherent FM heterodyne principle of the Michel...The method for measuring the strain of an object using an optical fiber and a frequency modulation(FM) coupled cavity semiconductor laser is proposed.This method uses the coherent FM heterodyne principle of the Michelson interferometer and can avoid the π/2 nonreciprocal phase bias and phase shifting problem existing in general fiber optic interferential sensors, the maximum detection range is limited by the coherent length of the semiconductor laser and its relative factor.展开更多
The recent progresses of fiber sensor fabrication in our group are reviewed.Novel inline fiber Mach-Zehnder interferometer(MZI) sensors with various structures are proposed and manufactured by femtosecond laser fabric...The recent progresses of fiber sensor fabrication in our group are reviewed.Novel inline fiber Mach-Zehnder interferometer(MZI) sensors with various structures are proposed and manufactured by femtosecond laser fabrication and fusion splicing for high-quality sensing of refractivity-sensitive parameters such as temperature,concentration,humidity,pressure,stress and strain: a) for an MZI sensor with a trench on a single-mode fiber,the refractive index(RI) sensitivity of acetone vapor is about 104 nm/RIU(refractive index unit) and the temperature sensitivity is 51.5 pm/℃ from 200 to 875 ℃;b) For an MZI consisting of two micro-air-cavities,the sensitivity is 501.5 nm/RIU and the detection limit is 1.994×10-6 RIU at the refractive index of 1.4;c) to reduce the fabrication cost,a new fusion-splicing based method is proposed to fabricate MZI sensors;the sensitivity is 664.57 nm/RIU with a detection limit of 1.5×10-6 RIU and its cost is tens of times cheaper than those of commercialized long period fiber Gratings;Also,5×10-5 acetone vapors are successfully detected by the MZI sensors coated with zeolite thin films.展开更多
基金This study is supported by National Natural Science Foundation ofChina (No.60507007)National Basic Research Program of China(No. 2003CB314900)Program for New Century ExcellentTalents in University (NCET, Min Zhang 2007).
文摘We proposed a scheme of fiber Bragg grating （FBG） sensor interrogation system based on all fiber Mach-Zehnder Interferometer （MZI） edge filter and tunable-FBG. The equal power signals from FBG sensor and tunable FBG are coupled into port 1 and port 2 of MZI respectively. The experimental results show that the interrogation precision of the proposed system is 0.02 nm in a range of I nm. Furthermore, the precision can be improved by adjusting the two interference arms of the filter.
文摘One of the problems in using grating sensors is how to measure a small Bragg wavelength shift accurately. Nowadays demodulation techniques are mainly based on the edge filter, tunable filter, or interferometric scanning methods. Interferometric demodulation is widely accepted as the technology which can provide the high sensitivity. An interrogation system using the interferometric scanning method is presented, in which an unbalanced fiber M-Z interferometer is used as the wavelength scanner for temperature measurement. A novel fiber Bragg grating sensor system based on M-Z interferometric demodulation technique is presented in this paper. The temperature sensitivity measured in the experiment is almost consistent with that obtained from the theoretic calculation.
文摘A low fineness fiber optic Fabry-Perot interferometric displacement sensor has been developed and tested.A 0.005 nm displacement resolution is obtained by using He-Ne laser with a high performance ,photodetectors with low noise ,low drift operational amplifiers,6-pole Butterworth filters and perfect digital signal processing circuits.
文摘Due to the limitation of Edlen Equation to compensate for air refractivity in ordinary air pressure, an experiment to study the relationship between air refractivity and temperature, along with its pressure, is designed and carried out from ordinary pressure to low pressure. The expansion of Edlen Equation is achieved by using the cascade-Correlation learning method, and a neural network architecture model. The applied accuracy of neural network is the same as that of Edlen Equation in an ordinary pressure zone.
文摘The theoretic analysis indicates that if the lengths of the cascaded and paralleled Fabry-Perot sensors are properly selected, the crosstalk can be well restricted.And the experiment simulation results agree with that of the theoretic analysis.
文摘The method for measuring the strain of an object using an optical fiber and a frequency modulation(FM) coupled cavity semiconductor laser is proposed.This method uses the coherent FM heterodyne principle of the Michelson interferometer and can avoid the π/2 nonreciprocal phase bias and phase shifting problem existing in general fiber optic interferential sensors, the maximum detection range is limited by the coherent length of the semiconductor laser and its relative factor.
基金supported by the National Natural Science Foundation of China(Nos.90923039 and 51025521)the 111 Project of China(No.B08043)
文摘The recent progresses of fiber sensor fabrication in our group are reviewed.Novel inline fiber Mach-Zehnder interferometer(MZI) sensors with various structures are proposed and manufactured by femtosecond laser fabrication and fusion splicing for high-quality sensing of refractivity-sensitive parameters such as temperature,concentration,humidity,pressure,stress and strain: a) for an MZI sensor with a trench on a single-mode fiber,the refractive index(RI) sensitivity of acetone vapor is about 104 nm/RIU(refractive index unit) and the temperature sensitivity is 51.5 pm/℃ from 200 to 875 ℃;b) For an MZI consisting of two micro-air-cavities,the sensitivity is 501.5 nm/RIU and the detection limit is 1.994×10-6 RIU at the refractive index of 1.4;c) to reduce the fabrication cost,a new fusion-splicing based method is proposed to fabricate MZI sensors;the sensitivity is 664.57 nm/RIU with a detection limit of 1.5×10-6 RIU and its cost is tens of times cheaper than those of commercialized long period fiber Gratings;Also,5×10-5 acetone vapors are successfully detected by the MZI sensors coated with zeolite thin films.
