Different types of fiber-optic sensors based on glass or polymeric fibers are used to evaluate material behavior or to monitor the integrity and long-term stability of load-bearing structure components. Fiber-optic se...Different types of fiber-optic sensors based on glass or polymeric fibers are used to evaluate material behavior or to monitor the integrity and long-term stability of load-bearing structure components. Fiber-optic sensors have been established as a new and innovative measurement technology in very different fields, such as material science, civil engineering, light-weight structures, geotechnical areas as well as chemical and high-voltage substations. Very often, mechanical quantities such as deformation, strain or vibration are requested. However, measurement of chemical quantities in materials and structure components, such as pH value in steel reinforced concrete members also provides information about the integrity of concrete structures. A special fiber-optic chemical sensor for monitoring the alkaline state (pH value) of the cementitious matrix in steel-reinforced concrete structures with the purpose of early detection of corrosion-initiating factors is described. The paper presents the use of several fiber-optic sensor technologies in engineering. One example concerns the use of highly resolving concrete-embeddable fiber Fabry-Perot acoustic emission (AE) sensors for the assessment of the bearing behaviour of large concrete piles in existing foundations or during and after its installation. Another example concerns fiber Bragg grating (FBG) sensors attached to anchor steels (micro piles) to measure the strain distribution in loaded soil anchors. Polymer optical fibers (POF) can be -- because of their high elasticity and high ultimate strain - well integrated into textiles to monitor their deformation behaviour. Such "intelligent" textiles are capable of monitoring displacement of soil or slopes, critical mechanical deformation in geotechnical structures (dikes, dams, and embankments) as well as in masonry structures during and after earthquakes.展开更多
Oxygen and carbon dioxide sensors are involved in many chemical and biochemical reactions. Consequently, considerable efforts over years have been devoted to discover and improve suitable techniques for measuring gas ...Oxygen and carbon dioxide sensors are involved in many chemical and biochemical reactions. Consequently, considerable efforts over years have been devoted to discover and improve suitable techniques for measuring gas concentrations by optical fiber sensors. Optical gas sensors consist of a gas-sensitive dye entrapped in a matrix with a high permeability to gas. With such sensors, gas concentration is evaluated based upon the reduction in luminescence intensity caused by gas quenching of the emitting state. However, the luminescence quenching effect of oxygen is highly sensitive to temperature. Thus, a simple, low-cost plastic optical fiber sensor for dual sensing of temperature and oxygen is presented. Also, a modified Stern-Volmer model is introduced to compensate for the temperature drift while the temperature is obtained by above dual sensor. Recently, we presented highly-sensitive oxygen and dissolved oxygen sensors comprising an optical fiber coated at one end with platinum (II) meso-tetrakis(pentafluorophenyl)porphyrin (PtTFPP) and PtTFPP entrapped core-shell silica nanoparticles embedded in an n-octyltriethoxysilane(Octyl-triEOS)/tetraethylorthosilane (TEOS) composite xerogel. Also, two-dimensional gas measurement for the distribution of chemical parameters in non-homogeneous samples is developed and is of interest in medical and biological researches.展开更多
A loop topology based white light interferometric sensor network for perimeter security has been designed and demonstrated. In the perimeter security sensing system, where fiber sensors are packaged in the suspended c...A loop topology based white light interferometric sensor network for perimeter security has been designed and demonstrated. In the perimeter security sensing system, where fiber sensors are packaged in the suspended cable or buried cable, a bi-directional optical path interrogator is built by using Michelson or Mach-Zehnder interferometer. A practical implementation of this technique is presented by using an amplified spontaneous emission (ASE) light source and standard single mode fiber, which are common in communication industry. The sensor loop topology is completely passive and absolute length measurements can be obtained for each sensing fiber segment so that it can be used to measure quasi-distribution strain perturbation. For the long distance perimeter monitoring, this technique not only extends the multiplexing potential, but also provides a redundancy for the sensing system. One breakdown point is allowed in the sensor loop because the sensing system will still work even if the embedded sensor loop breaks somewhere.展开更多
An optical fiber hydrophone based on equivalent phase shift fiber Bragg grating (EPS-FBG) with temperature compensation package provides an improvement of sensitivity in underwater acoustic measurement at wide frequ...An optical fiber hydrophone based on equivalent phase shift fiber Bragg grating (EPS-FBG) with temperature compensation package provides an improvement of sensitivity in underwater acoustic measurement at wide frequency range, from 2.SkHz to 12kHz. The acoustic pressure is transduced into elastic vibration of a circle metal disk, resulting in an intensity modulation of the reflected light wave back from fiber Bragg grating (FBG). Experiment shows that the 500 EPS-FBG hydrophone has a minimum detectable acoustic pressure of about at 5 kHz and achieves about 18-dB improvement of acoustic pressure sensitivity compared with a regular apodized FBG hydrophone.展开更多
We report our recent work on distributed feedback fiber laser based hydrophones. Some issues related to sensitivity, such as fiber laser phase condition, demodulation, and packaging, are also discussed. With the devel...We report our recent work on distributed feedback fiber laser based hydrophones. Some issues related to sensitivity, such as fiber laser phase condition, demodulation, and packaging, are also discussed. With the development of appropriate digital signal processing (DSP) techniques and packaging designs, an interferometric-type distributed feedback (DFB) fiber laser hydrophone system with acoustic sensitivity of 58.0 dB·re·uPa-Hz-0.5 at 1 kHz or a minimum detectable acoustic pressure below 800 uPa during field test is attained. We have also investigated an intensity-type DFB fiber laser hydrophone system and its performance.展开更多
Fiber Bragg grating (FBG) is a mature sensing technology for the measurement of strain, vibration, acoustics, acceleration, pressure, temperature, moisture, and corrosion. It has gained rapid acceptance in civil, ae...Fiber Bragg grating (FBG) is a mature sensing technology for the measurement of strain, vibration, acoustics, acceleration, pressure, temperature, moisture, and corrosion. It has gained rapid acceptance in civil, aerospace, chemical and petrochemical, medicine, aviation and automotive industries. The most prominent advantages of FBG are: small size and light weight, distributed array of FBG transducers on a single fiber, and immunity to radio frequency interference. However, a major disadvantage of FBG technology is that conventional state-of-the-art FBG interrogation system is typically bulky, heavy, and costly bench top instruments that are typically assembled from off-the-shelf fiber optic and optical components integrated with a signal electronics board into an instrument console. Based on the industrial need for a compact FBG interrogation system, this paper describes recent progress towards the development of miniature fiber Bragg grating sensor interrogator (FBG-TransceiverTM) system based on multi-channel monolithic integrated optic sensor microchip technology. The integrated optic microchip technology enables monolithic integration of all functionalities, both passive and active, of conventional bench top FBG sensor interrogator system, packaged in a miniaturized, low power operation, 2 cmx5 cm small form factor (SFF) package suitable for long-term structural health monitoring in applications where size, weight, and power are critical for operation.展开更多
In this paper, an overview of author's research is presented, commencing at the University of Kent under Prof. David A. Jackson. Early research in short optical pulses and fiber-optic delay-line digital correlators l...In this paper, an overview of author's research is presented, commencing at the University of Kent under Prof. David A. Jackson. Early research in short optical pulses and fiber-optic delay-line digital correlators led to optical communications research in code-division multiple access networking. This research was based on broadband incoherent light, and this theme continued with research into spectrum-sliced wavelength-division multiplexing. In shifting from photonics research to biomedical optics and biophotonics in the late 1990s, the emphasis on exploiting broadband light continued with research in optical coherence tomography, amongst other topics. In addition to the research outcomes, how these outcomes were attained is described, including mention of the exceptional contributions of many of my colleagues.展开更多
This article reviews author's research work on fiber-optic sensors over the last twenty years. It includes two aspects: low-coherence interferometric sensors (LCI) and fiber Bragg grating (FBG) sensors. For LCI ...This article reviews author's research work on fiber-optic sensors over the last twenty years. It includes two aspects: low-coherence interferometric sensors (LCI) and fiber Bragg grating (FBG) sensors. For LCI sensors, author's work mainly focuses on the interrogation and multiplexing methods for Fizeau and Fabry-Perot interferometric sensors at the University of Kent at Canterbury (UKC), UK, and study on novel Fabry-Perot interferometric sensors and their multiplexing methods at Chongqing University (CQU) and University of Electronic Science & Technology of China (UESTC), China, respectively. For FBG sensors, a number of multiplexing schemes are proposed and demonstrated at UKC, and then novel methods for realization of multi-parameter measurement and long-distance measurement based on the FBG sensor and its combination with other optical fiber sensors are also reported at CQU & UESTC. Thus, author's study on these two topics can be diviaed into two periods, at UKC and at CQU & UESTC, China. This review is presented in such a time sequence.展开更多
A new optical intensity-based sensing mechanism for the measurement of refractive index and minute displacement is proposed in this paper, which is based on modifying the amount of light coupled between two parallel l...A new optical intensity-based sensing mechanism for the measurement of refractive index and minute displacement is proposed in this paper, which is based on modifying the amount of light coupled between two parallel long-period fiber gratings. The characteristics of this sensing mechanism with experiments and simulation results are demonstrated.展开更多
Broadband, high-speed wavelength-swept lasers can substantially enhance applications in optical coherence tomography, chemical spectroscopy, and fiber-optic sensing. We report the demonstration of Fourier-domain mode-...Broadband, high-speed wavelength-swept lasers can substantially enhance applications in optical coherence tomography, chemical spectroscopy, and fiber-optic sensing. We report the demonstration of Fourier-domain mode-lock lasers operating at about 90kHz effective sweep rate over a 158nm sweep range using a single-band design and over a 284nm sweep range across the 1.3 μm to 1.5μm wavelength spectrum using a unique broadband design. A novel dual-detection full-range Fourier-domain optical coherence tomography system is developed which provides 7 I-tm axial resolution (in air)at about 90 kHz axial scan rate for mirror-image resolved Doppler imaging in a human finger and an African frog tadpole.展开更多
This paper provides a short overview of the time I spent as a member of the Applied Optics Group at the University of Kent (1985-1989) followed by a review of my research during my time at Cranfield University (198...This paper provides a short overview of the time I spent as a member of the Applied Optics Group at the University of Kent (1985-1989) followed by a review of my research during my time at Cranfield University (1989 to date).展开更多
The author's research activities undertaken at the Applied Optics Group, the University of Kent at Canterbury are reviewed, during his time there from 1988-1992 and 1994-1996, followed by a summary of recent research...The author's research activities undertaken at the Applied Optics Group, the University of Kent at Canterbury are reviewed, during his time there from 1988-1992 and 1994-1996, followed by a summary of recent research. The areas of interest are high finesse ring resonators, tunable optical filters, novel optical fiber grating sensors in glass and polymer, femtosecond laser inscription and micromachining, environmental pollution monitoring, hydrogen activated Pd films on silicon and impurity measurement on silicon wafers.展开更多
In this paper the author describes research and development activities in the field of optical sensing undertaken since his time within the Applied Optics Group at the University of Kent. The main topics covered are l...In this paper the author describes research and development activities in the field of optical sensing undertaken since his time within the Applied Optics Group at the University of Kent. The main topics covered are laser vibrometry and optical range-finding techniques. The author also gives a summary of his research at University of Kent, covering 1982-1985.展开更多
Grating writing in structured optical fibers is reviewed. Various laser sources have been used including UV and near IR nanosecond and femtosecond lasers, each enabling different material processing regimes. The issue...Grating writing in structured optical fibers is reviewed. Various laser sources have been used including UV and near IR nanosecond and femtosecond lasers, each enabling different material processing regimes. The issue of scattering is modeled through simulation and compared with experiment. Good agreement has been established.展开更多
The use of near infrared, high intensity femtosecond laser pulses for the inscription of long period fiber gratings in photonic crystal fiber is reported. The formation of grating structures in photonic crystal fiber ...The use of near infrared, high intensity femtosecond laser pulses for the inscription of long period fiber gratings in photonic crystal fiber is reported. The formation of grating structures in photonic crystal fiber is complicated by the fiber structure that allows wave-guidance but that impairs and scatters the femtosecond inscription beam. The effects of symmetric and asymmetric femtosecond laser inscriptions are compared and the polarization characteristics of long period gratings and their responses to external perturbations are reported.展开更多
Intensity-modulated fiber Bragg grating (FBG) sensors, compared with normal wavelength-encoding FBG sensors, can reduce the cost of sensor system significantly by using cost-efficient optical power detection devices...Intensity-modulated fiber Bragg grating (FBG) sensors, compared with normal wavelength-encoding FBG sensors, can reduce the cost of sensor system significantly by using cost-efficient optical power detection devices, instead of expensive wavelength measurement instruments. Chirped-FBG (CFBG) based intensity-modulated sensors show potential applications in various sensing areas due to their many advantages, including inherent independence of temperature, high measurement speed, and low cost, in addition to the merits of all fiber-optic sensors. This paper theoretically studies the sensing principle of CFBG-based intensity-modulated sensors and briefly reviews their recent progress in measurement of displacement, acceleration, and tilt angle.展开更多
文摘Different types of fiber-optic sensors based on glass or polymeric fibers are used to evaluate material behavior or to monitor the integrity and long-term stability of load-bearing structure components. Fiber-optic sensors have been established as a new and innovative measurement technology in very different fields, such as material science, civil engineering, light-weight structures, geotechnical areas as well as chemical and high-voltage substations. Very often, mechanical quantities such as deformation, strain or vibration are requested. However, measurement of chemical quantities in materials and structure components, such as pH value in steel reinforced concrete members also provides information about the integrity of concrete structures. A special fiber-optic chemical sensor for monitoring the alkaline state (pH value) of the cementitious matrix in steel-reinforced concrete structures with the purpose of early detection of corrosion-initiating factors is described. The paper presents the use of several fiber-optic sensor technologies in engineering. One example concerns the use of highly resolving concrete-embeddable fiber Fabry-Perot acoustic emission (AE) sensors for the assessment of the bearing behaviour of large concrete piles in existing foundations or during and after its installation. Another example concerns fiber Bragg grating (FBG) sensors attached to anchor steels (micro piles) to measure the strain distribution in loaded soil anchors. Polymer optical fibers (POF) can be -- because of their high elasticity and high ultimate strain - well integrated into textiles to monitor their deformation behaviour. Such "intelligent" textiles are capable of monitoring displacement of soil or slopes, critical mechanical deformation in geotechnical structures (dikes, dams, and embankments) as well as in masonry structures during and after earthquakes.
文摘Oxygen and carbon dioxide sensors are involved in many chemical and biochemical reactions. Consequently, considerable efforts over years have been devoted to discover and improve suitable techniques for measuring gas concentrations by optical fiber sensors. Optical gas sensors consist of a gas-sensitive dye entrapped in a matrix with a high permeability to gas. With such sensors, gas concentration is evaluated based upon the reduction in luminescence intensity caused by gas quenching of the emitting state. However, the luminescence quenching effect of oxygen is highly sensitive to temperature. Thus, a simple, low-cost plastic optical fiber sensor for dual sensing of temperature and oxygen is presented. Also, a modified Stern-Volmer model is introduced to compensate for the temperature drift while the temperature is obtained by above dual sensor. Recently, we presented highly-sensitive oxygen and dissolved oxygen sensors comprising an optical fiber coated at one end with platinum (II) meso-tetrakis(pentafluorophenyl)porphyrin (PtTFPP) and PtTFPP entrapped core-shell silica nanoparticles embedded in an n-octyltriethoxysilane(Octyl-triEOS)/tetraethylorthosilane (TEOS) composite xerogel. Also, two-dimensional gas measurement for the distribution of chemical parameters in non-homogeneous samples is developed and is of interest in medical and biological researches.
基金This work was supported by the key project of Nature Science Foundation of Heilongjiang Province (No. ZD200810) and Key Project Foster Program for University and College Science and Technology Innovation (No. 708030), and partially supported by the National Nature Science Foundation of China, under grant number 60877046, 60707013, and 60807032, to the Harbin Engineering University.
文摘A loop topology based white light interferometric sensor network for perimeter security has been designed and demonstrated. In the perimeter security sensing system, where fiber sensors are packaged in the suspended cable or buried cable, a bi-directional optical path interrogator is built by using Michelson or Mach-Zehnder interferometer. A practical implementation of this technique is presented by using an amplified spontaneous emission (ASE) light source and standard single mode fiber, which are common in communication industry. The sensor loop topology is completely passive and absolute length measurements can be obtained for each sensing fiber segment so that it can be used to measure quasi-distribution strain perturbation. For the long distance perimeter monitoring, this technique not only extends the multiplexing potential, but also provides a redundancy for the sensing system. One breakdown point is allowed in the sensor loop because the sensing system will still work even if the embedded sensor loop breaks somewhere.
文摘An optical fiber hydrophone based on equivalent phase shift fiber Bragg grating (EPS-FBG) with temperature compensation package provides an improvement of sensitivity in underwater acoustic measurement at wide frequency range, from 2.SkHz to 12kHz. The acoustic pressure is transduced into elastic vibration of a circle metal disk, resulting in an intensity modulation of the reflected light wave back from fiber Bragg grating (FBG). Experiment shows that the 500 EPS-FBG hydrophone has a minimum detectable acoustic pressure of about at 5 kHz and achieves about 18-dB improvement of acoustic pressure sensitivity compared with a regular apodized FBG hydrophone.
文摘We report our recent work on distributed feedback fiber laser based hydrophones. Some issues related to sensitivity, such as fiber laser phase condition, demodulation, and packaging, are also discussed. With the development of appropriate digital signal processing (DSP) techniques and packaging designs, an interferometric-type distributed feedback (DFB) fiber laser hydrophone system with acoustic sensitivity of 58.0 dB·re·uPa-Hz-0.5 at 1 kHz or a minimum detectable acoustic pressure below 800 uPa during field test is attained. We have also investigated an intensity-type DFB fiber laser hydrophone system and its performance.
文摘Fiber Bragg grating (FBG) is a mature sensing technology for the measurement of strain, vibration, acoustics, acceleration, pressure, temperature, moisture, and corrosion. It has gained rapid acceptance in civil, aerospace, chemical and petrochemical, medicine, aviation and automotive industries. The most prominent advantages of FBG are: small size and light weight, distributed array of FBG transducers on a single fiber, and immunity to radio frequency interference. However, a major disadvantage of FBG technology is that conventional state-of-the-art FBG interrogation system is typically bulky, heavy, and costly bench top instruments that are typically assembled from off-the-shelf fiber optic and optical components integrated with a signal electronics board into an instrument console. Based on the industrial need for a compact FBG interrogation system, this paper describes recent progress towards the development of miniature fiber Bragg grating sensor interrogator (FBG-TransceiverTM) system based on multi-channel monolithic integrated optic sensor microchip technology. The integrated optic microchip technology enables monolithic integration of all functionalities, both passive and active, of conventional bench top FBG sensor interrogator system, packaged in a miniaturized, low power operation, 2 cmx5 cm small form factor (SFF) package suitable for long-term structural health monitoring in applications where size, weight, and power are critical for operation.
文摘In this paper, an overview of author's research is presented, commencing at the University of Kent under Prof. David A. Jackson. Early research in short optical pulses and fiber-optic delay-line digital correlators led to optical communications research in code-division multiple access networking. This research was based on broadband incoherent light, and this theme continued with research into spectrum-sliced wavelength-division multiplexing. In shifting from photonics research to biomedical optics and biophotonics in the late 1990s, the emphasis on exploiting broadband light continued with research in optical coherence tomography, amongst other topics. In addition to the research outcomes, how these outcomes were attained is described, including mention of the exceptional contributions of many of my colleagues.
文摘This article reviews author's research work on fiber-optic sensors over the last twenty years. It includes two aspects: low-coherence interferometric sensors (LCI) and fiber Bragg grating (FBG) sensors. For LCI sensors, author's work mainly focuses on the interrogation and multiplexing methods for Fizeau and Fabry-Perot interferometric sensors at the University of Kent at Canterbury (UKC), UK, and study on novel Fabry-Perot interferometric sensors and their multiplexing methods at Chongqing University (CQU) and University of Electronic Science & Technology of China (UESTC), China, respectively. For FBG sensors, a number of multiplexing schemes are proposed and demonstrated at UKC, and then novel methods for realization of multi-parameter measurement and long-distance measurement based on the FBG sensor and its combination with other optical fiber sensors are also reported at CQU & UESTC. Thus, author's study on these two topics can be diviaed into two periods, at UKC and at CQU & UESTC, China. This review is presented in such a time sequence.
文摘A new optical intensity-based sensing mechanism for the measurement of refractive index and minute displacement is proposed in this paper, which is based on modifying the amount of light coupled between two parallel long-period fiber gratings. The characteristics of this sensing mechanism with experiments and simulation results are demonstrated.
基金Acknowledgement This work was supported in part by the Florida I4 Corridor, the New York State Foundation for Science, Technology, and Innovation (NYSTAR), the Royal Thai Government, and the Photonics Technology Access Program (PTAP) sponsored by the Defense Advanced Research Projects Agency and National Science Foundation (DARPA & NSF).
文摘Broadband, high-speed wavelength-swept lasers can substantially enhance applications in optical coherence tomography, chemical spectroscopy, and fiber-optic sensing. We report the demonstration of Fourier-domain mode-lock lasers operating at about 90kHz effective sweep rate over a 158nm sweep range using a single-band design and over a 284nm sweep range across the 1.3 μm to 1.5μm wavelength spectrum using a unique broadband design. A novel dual-detection full-range Fourier-domain optical coherence tomography system is developed which provides 7 I-tm axial resolution (in air)at about 90 kHz axial scan rate for mirror-image resolved Doppler imaging in a human finger and an African frog tadpole.
文摘This paper provides a short overview of the time I spent as a member of the Applied Optics Group at the University of Kent (1985-1989) followed by a review of my research during my time at Cranfield University (1989 to date).
文摘The author's research activities undertaken at the Applied Optics Group, the University of Kent at Canterbury are reviewed, during his time there from 1988-1992 and 1994-1996, followed by a summary of recent research. The areas of interest are high finesse ring resonators, tunable optical filters, novel optical fiber grating sensors in glass and polymer, femtosecond laser inscription and micromachining, environmental pollution monitoring, hydrogen activated Pd films on silicon and impurity measurement on silicon wafers.
文摘In this paper the author describes research and development activities in the field of optical sensing undertaken since his time within the Applied Optics Group at the University of Kent. The main topics covered are laser vibrometry and optical range-finding techniques. The author also gives a summary of his research at University of Kent, covering 1982-1985.
文摘Grating writing in structured optical fibers is reviewed. Various laser sources have been used including UV and near IR nanosecond and femtosecond lasers, each enabling different material processing regimes. The issue of scattering is modeled through simulation and compared with experiment. Good agreement has been established.
文摘The use of near infrared, high intensity femtosecond laser pulses for the inscription of long period fiber gratings in photonic crystal fiber is reported. The formation of grating structures in photonic crystal fiber is complicated by the fiber structure that allows wave-guidance but that impairs and scatters the femtosecond inscription beam. The effects of symmetric and asymmetric femtosecond laser inscriptions are compared and the polarization characteristics of long period gratings and their responses to external perturbations are reported.
基金This work was co-supported by the National Basic Research Program of China (973 Program) under Grant No. 2010CB327804, the National Natural Science Foundation of China under Grant No. 60807021, and the Natural Science Foundation of Zhejiang Province, China under Grant No. RI080087. The author thanks all the collaborators and students who contributed to this work.
文摘Intensity-modulated fiber Bragg grating (FBG) sensors, compared with normal wavelength-encoding FBG sensors, can reduce the cost of sensor system significantly by using cost-efficient optical power detection devices, instead of expensive wavelength measurement instruments. Chirped-FBG (CFBG) based intensity-modulated sensors show potential applications in various sensing areas due to their many advantages, including inherent independence of temperature, high measurement speed, and low cost, in addition to the merits of all fiber-optic sensors. This paper theoretically studies the sensing principle of CFBG-based intensity-modulated sensors and briefly reviews their recent progress in measurement of displacement, acceleration, and tilt angle.