Acoustic emission monitoring is often used in the diagnosis of electrical and mechanical incipient faults in the high voltage apparatus. Partial discharges are a major source of insulation failure in electric power tr...Acoustic emission monitoring is often used in the diagnosis of electrical and mechanical incipient faults in the high voltage apparatus. Partial discharges are a major source of insulation failure in electric power transformers, and the differentiation from other sources of acoustic emission is of the utmost importance. This paper reports the development of a new sensor concept - a fiber laser sensor based on a phase-shifted chirped fiber grating - for the acoustic emission detection of incipient faults in oil-filled power transformers. These sensors can be placed in the inner surface of the transformer tank wall, not affecting the insulation integrity of the structure and improving fault detection and location. The performance of the sensing head is characterized and compared for different surrounding media： air, water, and oil. The results obtained indicate the feasibility of this sensing approach for the industrial development of practical solutions.展开更多
A novel distributed feedback（DFB） fiber laser sensor, which can measure acoustic and magnetic fields simultaneously, is proposed. The magnetic field can be measured by detecting the change of resonant frequency of t...A novel distributed feedback（DFB） fiber laser sensor, which can measure acoustic and magnetic fields simultaneously, is proposed. The magnetic field can be measured by detecting the change of resonant frequency of the fiber laser, and the acoustic pressure can be measured by detecting the phase shift of the fiber laser. Both of the signals can be simultaneously demodulated in the frequency domain without affecting each other. Experimental studies show that the acoustic pressure sensitivity of this sensor is about-130 d B（0 dB re 1 pm∕μPa） and the sensor has a good linearity with a magnetic field sensitivity of 0.57 Hz∕mT.展开更多
We have developed a novel optical fiber ring laser using a semiconductor optical amplifier (SOA) as the gain medium, and taking advantage of polarization anisotropy of its gain. The frequency difference of the bi-dire...We have developed a novel optical fiber ring laser using a semiconductor optical amplifier (SOA) as the gain medium, and taking advantage of polarization anisotropy of its gain. The frequency difference of the bi-directional laser is controlled by birefringence which is introduced in the ring laser cavity. The beat frequency generated by combining two counter-propagating oscillations is proportional to the birefringence, the fiber ring laser of the present study is, therefore, applicable to the fiber sensor. The sensing signal is obtained in a frequency domain with the material which causes the retardation change by a physical phenomenon to be measured. For the application to stress sensing, the present laser was investigated with a photoelastic material.展开更多
A new structure of the photonic crystal fiber（PCF）based Mach-Zednder interferometer（MZI）is fabricated and presented.The structure has microholes ablated by a femtosecond laser.The fringe visibility can be enhanced...A new structure of the photonic crystal fiber（PCF）based Mach-Zednder interferometer（MZI）is fabricated and presented.The structure has microholes ablated by a femtosecond laser.The fringe visibility can be enhanced more than 10 dB compared with the interferometer without a microhole.The interferometer is characterized by sodium chloride solutions for refractive index（RI）sensing.The RI sensitivities are greatly increased by the hole fabrication since it directly changes the cladding modes of the PCF.For the interferometer sensor with two holes,the RI sensitivity is 157.74 nm/RIU,which is 5 times than that of the sensor without a microhole.Microholes ablation with a femtosecond laser on PCF can increase the sensor＇s sensitivity dramatically.Femtosecond laser has a wide application prospect in the field of performance improvement of the sensors.展开更多
Recent progress in long-distance in-Fiber Bragg Grating （FBG） sensor systems at University of Electronic Science ＆ Technology of China （UESTC） is reviewed in this paper. Two novel approaches with a 50km transmiss...Recent progress in long-distance in-Fiber Bragg Grating （FBG） sensor systems at University of Electronic Science ＆ Technology of China （UESTC） is reviewed in this paper. Two novel approaches with a 50km transmission distance are proposed and demonstrated. The first one is based on the combination of bidirectional Raman amplification and a dual Erbium-Doped Fiber （EDF） configuration. A good Signal-to-Noise Ratio （SNR） of ～16dB is achieved with only a pump power of ～280 mW, which is ～10 dB higher than that without amplification. The second is based on a novel tunable fiber ring laser configuration with hybrid Raman/EDFA configuration. Experimental results show that an excellent optical SNR of-～60 dB has been achieved for a 50 km transmission distance with a low Raman pump power of ～170 mW and a low EDFA pump power of～40 mW at wavelength of 980 nm. It is anticipated that these long-distance FBG sensing systems could find important applications in health monitoring of large infra-structures, such as oil or gas pipelines, ultra-long bridges and tunnels, river banks, and so on.展开更多
We propose a high sensitivity sensor based on a mode number-encoded multi-longitudinal mode fiber laser. The fiber laser incorporates a uniform fiber Bragg grating （FBG） and a fiber Fabry-Perot interferometer （FFPI...We propose a high sensitivity sensor based on a mode number-encoded multi-longitudinal mode fiber laser. The fiber laser incorporates a uniform fiber Bragg grating （FBG） and a fiber Fabry-Perot interferometer （FFPI） as sensitive components in the cavity. The sensor counts the number of longitudinal modes （NLM） of fiber laser, which is caused by the mismatch between the reflection band of FBG and the transmission band of FFPI resulting from the application of external perturbation to the FBG. An electrical spectrum analyzer is adopted to analyze the NLM. The strain sensor is experimentally demonstrated to have sensi- tivity of as high as 0.02 με/mode.展开更多
A novel fiber-optic magnetic field sensor is demonstrated based on a dual-polarization fiber-grating laser, which is embedded in an epoxy resin-bonded magnetostrictive composite material with doped Terfenol-D particle...A novel fiber-optic magnetic field sensor is demonstrated based on a dual-polarization fiber-grating laser, which is embedded in an epoxy resin-bonded magnetostrictive composite material with doped Terfenol-D particles. A simple structure is designed to convert the magnetic field-induced strain to transversal stress, which is applied to the fiber laser to produce beat note frequency changes for measurement purposes. The response of the proposed sensor is measured, and shows quite a good directivity and linearity with a sensitivity of 10.5 Hz/μT to the magnetic field. It also shows a large measurable range up to about 0.3 T.展开更多
A new micro-vibration sensor based on single-mode fiber ring laser is put forward. The Mach-Zehnder interferometric （MZI） detection technique is presented for interrogating laser frequency shift due to the measurand...A new micro-vibration sensor based on single-mode fiber ring laser is put forward. The Mach-Zehnder interferometric （MZI） detection technique is presented for interrogating laser frequency shift due to the measurand （piezoelectric transducer （PZT） is used to simulate the micro-vibration） induced laser cavity strain from both single- and multi-mode lasers. In the experiment, compared with multi-mode laser sensors, the single-mode laser sensor is proved to be a sensor with high resolution. When the PZT is driven by the analog signal （0.03 rad near 2 kHz）, the signal-to-noise ratio （SNR） of output signal from the single-mode laser sensor is close to 55 dB and the sensitivity of the sensor is about 5 ×10^-5 rad/Hz1/2.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
文摘Acoustic emission monitoring is often used in the diagnosis of electrical and mechanical incipient faults in the high voltage apparatus. Partial discharges are a major source of insulation failure in electric power transformers, and the differentiation from other sources of acoustic emission is of the utmost importance. This paper reports the development of a new sensor concept - a fiber laser sensor based on a phase-shifted chirped fiber grating - for the acoustic emission detection of incipient faults in oil-filled power transformers. These sensors can be placed in the inner surface of the transformer tank wall, not affecting the insulation integrity of the structure and improving fault detection and location. The performance of the sensing head is characterized and compared for different surrounding media： air, water, and oil. The results obtained indicate the feasibility of this sensing approach for the industrial development of practical solutions.
基金supported by the Key R&D Program of China(No.2017YFB0405503)the Youth Innovation Promotion Association of CAS(No.2016106)
文摘A novel distributed feedback（DFB） fiber laser sensor, which can measure acoustic and magnetic fields simultaneously, is proposed. The magnetic field can be measured by detecting the change of resonant frequency of the fiber laser, and the acoustic pressure can be measured by detecting the phase shift of the fiber laser. Both of the signals can be simultaneously demodulated in the frequency domain without affecting each other. Experimental studies show that the acoustic pressure sensitivity of this sensor is about-130 d B（0 dB re 1 pm∕μPa） and the sensor has a good linearity with a magnetic field sensitivity of 0.57 Hz∕mT.
文摘We have developed a novel optical fiber ring laser using a semiconductor optical amplifier (SOA) as the gain medium, and taking advantage of polarization anisotropy of its gain. The frequency difference of the bi-directional laser is controlled by birefringence which is introduced in the ring laser cavity. The beat frequency generated by combining two counter-propagating oscillations is proportional to the birefringence, the fiber ring laser of the present study is, therefore, applicable to the fiber sensor. The sensing signal is obtained in a frequency domain with the material which causes the retardation change by a physical phenomenon to be measured. For the application to stress sensing, the present laser was investigated with a photoelastic material.
文摘A new structure of the photonic crystal fiber（PCF）based Mach-Zednder interferometer（MZI）is fabricated and presented.The structure has microholes ablated by a femtosecond laser.The fringe visibility can be enhanced more than 10 dB compared with the interferometer without a microhole.The interferometer is characterized by sodium chloride solutions for refractive index（RI）sensing.The RI sensitivities are greatly increased by the hole fabrication since it directly changes the cladding modes of the PCF.For the interferometer sensor with two holes,the RI sensitivity is 157.74 nm/RIU,which is 5 times than that of the sensor without a microhole.Microholes ablation with a femtosecond laser on PCF can increase the sensor＇s sensitivity dramatically.Femtosecond laser has a wide application prospect in the field of performance improvement of the sensors.
基金Supported by the Key Project of National Natural Science Foundation of China (No.60537040)
文摘Recent progress in long-distance in-Fiber Bragg Grating （FBG） sensor systems at University of Electronic Science ＆ Technology of China （UESTC） is reviewed in this paper. Two novel approaches with a 50km transmission distance are proposed and demonstrated. The first one is based on the combination of bidirectional Raman amplification and a dual Erbium-Doped Fiber （EDF） configuration. A good Signal-to-Noise Ratio （SNR） of ～16dB is achieved with only a pump power of ～280 mW, which is ～10 dB higher than that without amplification. The second is based on a novel tunable fiber ring laser configuration with hybrid Raman/EDFA configuration. Experimental results show that an excellent optical SNR of-～60 dB has been achieved for a 50 km transmission distance with a low Raman pump power of ～170 mW and a low EDFA pump power of～40 mW at wavelength of 980 nm. It is anticipated that these long-distance FBG sensing systems could find important applications in health monitoring of large infra-structures, such as oil or gas pipelines, ultra-long bridges and tunnels, river banks, and so on.
基金supported by the Major Program of National Natural Science Foundation of China(No.60937002)the National Natural Science Foundation of China(No.60907037)the Fundamental Research Funds for the Central Universities(HUST:2011TS059)
文摘We propose a high sensitivity sensor based on a mode number-encoded multi-longitudinal mode fiber laser. The fiber laser incorporates a uniform fiber Bragg grating （FBG） and a fiber Fabry-Perot interferometer （FFPI） as sensitive components in the cavity. The sensor counts the number of longitudinal modes （NLM） of fiber laser, which is caused by the mismatch between the reflection band of FBG and the transmission band of FFPI resulting from the application of external perturbation to the FBG. An electrical spectrum analyzer is adopted to analyze the NLM. The strain sensor is experimentally demonstrated to have sensi- tivity of as high as 0.02 με/mode.
基金supported by the National Natural Science Foundation of China(Grant No.11474133 and61235005)the Planned Science and Technology Project of Guangzhou(Grant No.2012J5100028)the Project of Science and Technology New Star of Zhujiang in Guangzhou City(Grant No.2012J2200043)
文摘A novel fiber-optic magnetic field sensor is demonstrated based on a dual-polarization fiber-grating laser, which is embedded in an epoxy resin-bonded magnetostrictive composite material with doped Terfenol-D particles. A simple structure is designed to convert the magnetic field-induced strain to transversal stress, which is applied to the fiber laser to produce beat note frequency changes for measurement purposes. The response of the proposed sensor is measured, and shows quite a good directivity and linearity with a sensitivity of 10.5 Hz/μT to the magnetic field. It also shows a large measurable range up to about 0.3 T.
基金supported by the Technological Fund of Outstanding Youth of Anhui Province under Contract No.08040106903
文摘A new micro-vibration sensor based on single-mode fiber ring laser is put forward. The Mach-Zehnder interferometric （MZI） detection technique is presented for interrogating laser frequency shift due to the measurand （piezoelectric transducer （PZT） is used to simulate the micro-vibration） induced laser cavity strain from both single- and multi-mode lasers. In the experiment, compared with multi-mode laser sensors, the single-mode laser sensor is proved to be a sensor with high resolution. When the PZT is driven by the analog signal （0.03 rad near 2 kHz）, the signal-to-noise ratio （SNR） of output signal from the single-mode laser sensor is close to 55 dB and the sensitivity of the sensor is about 5 ×10^-5 rad/Hz1/2.
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.
