U. Nawrot, T. Geernaert, B. De Pauw, D. Anastasopoulos, E. Reynders, G. De Roeck, F. Berghmans
A well-known structural health monitoring method used to detect and locate damage in civil engineering structures is vibration-based damage identification. It typically monitors the civil structure over time to spot slow or sudden changes in its natural frequencies, damping factors or modal displacements. This approach can prove very powerful, but the sensitivity of those properties to local damage can be rather low. In addition, their cross-sensitivity to environmental influences may completely mask the effect of damage, even of severe damage. Instead one can consider the modal strains and curvatures, which are much more sensitive to local damage, but direct (quasi-)distributed monitoring of these quantities with sufficient strain resolution as well as adequate spatial resolution is not straightforward with current measurement techniques. This stems from the small (sub-microstrain) amplitudes of the strain levels occurring following ambient or operational excitation of the structure under test. To deal with this issue we propose and demonstrate a novel mechanical transducer that amplifies the strain applied to an optical fiber Bragg grating sensor with a factor of about 36. In addition the transducer resonance frequencies are sufficiently high to ensure accurate dynamic strain monitoring of civil structures under ambient excitation.
{"title":"Mechanical strain-amplifying transducer for fiber Bragg grating sensors with applications in structural health monitoring","authors":"U. Nawrot, T. Geernaert, B. De Pauw, D. Anastasopoulos, E. Reynders, G. De Roeck, F. Berghmans","doi":"10.1117/12.2264614","DOIUrl":"https://doi.org/10.1117/12.2264614","url":null,"abstract":"A well-known structural health monitoring method used to detect and locate damage in civil engineering structures is vibration-based damage identification. It typically monitors the civil structure over time to spot slow or sudden changes in its natural frequencies, damping factors or modal displacements. This approach can prove very powerful, but the sensitivity of those properties to local damage can be rather low. In addition, their cross-sensitivity to environmental influences may completely mask the effect of damage, even of severe damage. Instead one can consider the modal strains and curvatures, which are much more sensitive to local damage, but direct (quasi-)distributed monitoring of these quantities with sufficient strain resolution as well as adequate spatial resolution is not straightforward with current measurement techniques. This stems from the small (sub-microstrain) amplitudes of the strain levels occurring following ambient or operational excitation of the structure under test. To deal with this issue we propose and demonstrate a novel mechanical transducer that amplifies the strain applied to an optical fiber Bragg grating sensor with a factor of about 36. In addition the transducer resonance frequencies are sufficiently high to ensure accurate dynamic strain monitoring of civil structures under ambient excitation.","PeriodicalId":198716,"journal":{"name":"2017 25th Optical Fiber Sensors Conference (OFS)","volume":"69 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114513170","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
C. Kito, Hiroshi Takahashi, K. Toge, Tetsuya Manabe
We propose a novel BOTDA that can measure a BFS change appearing on a time axis with a single-shot measurement by using a frequency-swept probe pulse. The proposed method employs a very simple laser control and detection system, without precise test light frequency control, and with an oscilloscope. We demonstrate a fast BFS distribution measurement completed within 0.33 s with 1.8 MHz BFS accuracy for a 10 km range, and discuss its advantages compared with conventional BOTDA.
{"title":"Simplified and fast acquirable BOTDA with frequency-swept probe pulse","authors":"C. Kito, Hiroshi Takahashi, K. Toge, Tetsuya Manabe","doi":"10.1117/12.2265528","DOIUrl":"https://doi.org/10.1117/12.2265528","url":null,"abstract":"We propose a novel BOTDA that can measure a BFS change appearing on a time axis with a single-shot measurement by using a frequency-swept probe pulse. The proposed method employs a very simple laser control and detection system, without precise test light frequency control, and with an oscilloscope. We demonstrate a fast BFS distribution measurement completed within 0.33 s with 1.8 MHz BFS accuracy for a 10 km range, and discuss its advantages compared with conventional BOTDA.","PeriodicalId":198716,"journal":{"name":"2017 25th Optical Fiber Sensors Conference (OFS)","volume":"66 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114516434","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This work presents an application of reactive ion etching (RIE) for an effective tuning of the spectral response and the refractive-index (RI) sensitivity of the micro-cavity in-line Mach-Zehnder interferometer (μIMZI). The μIMZIs were fabricated using femtosecond laser micromachining in a standard single-mode fiber as a form circular holes with a diameter of 54 μm. The application of RIE with SF6 and O2 used as reactive gas allows for an efficient and well-controlled etching of the fabricated structure. The process resulted in cleaning the bottom of the micro-cavity and smoothening of its sidewalls. In transmission measurements, the effect of the plasma processing was observed as an increase in both spectral depths of the minima and RI sensitivity of the structure, as well as improved wettability of the micro-cavity surface, which made the measurements faster and easier.
{"title":"Tuning refractive index sensing properties of micro-cavity in-line Mach-Zehnder interferometer with plasma etching","authors":"M. Janik, M. Koba, W. Bock, M. Śmietana","doi":"10.1117/12.2265755","DOIUrl":"https://doi.org/10.1117/12.2265755","url":null,"abstract":"This work presents an application of reactive ion etching (RIE) for an effective tuning of the spectral response and the refractive-index (RI) sensitivity of the micro-cavity in-line Mach-Zehnder interferometer (μIMZI). The μIMZIs were fabricated using femtosecond laser micromachining in a standard single-mode fiber as a form circular holes with a diameter of 54 μm. The application of RIE with SF6 and O2 used as reactive gas allows for an efficient and well-controlled etching of the fabricated structure. The process resulted in cleaning the bottom of the micro-cavity and smoothening of its sidewalls. In transmission measurements, the effect of the plasma processing was observed as an increase in both spectral depths of the minima and RI sensitivity of the structure, as well as improved wettability of the micro-cavity surface, which made the measurements faster and easier.","PeriodicalId":198716,"journal":{"name":"2017 25th Optical Fiber Sensors Conference (OFS)","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114695481","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents a multimode fiber sensor that uses surface plasmon resonance on a metallic wire to measure refractive index. Numerical simulations based on the finite element method reveal the sensor supports several plasmon modes in the wire capable of coupling with the multiples optical fiber modes. Therefore, the sensor configuration creates multiple resonances at different wavelengths, with different values of the loss, sensitivity, among other parameters. Choosing the appropriate mode and filtering out the rest of the modes allows to optimize the sensor performance. In the present work a sensitivity of 5340nm/RlU and resolution of 1.87×10−6RlU were found.
{"title":"Optimization of modal sensitivity in nanowire SPR multimode sensor","authors":"D. F. Santos, A. Guerreiro, J. Baptista","doi":"10.1117/12.2264435","DOIUrl":"https://doi.org/10.1117/12.2264435","url":null,"abstract":"This paper presents a multimode fiber sensor that uses surface plasmon resonance on a metallic wire to measure refractive index. Numerical simulations based on the finite element method reveal the sensor supports several plasmon modes in the wire capable of coupling with the multiples optical fiber modes. Therefore, the sensor configuration creates multiple resonances at different wavelengths, with different values of the loss, sensitivity, among other parameters. Choosing the appropriate mode and filtering out the rest of the modes allows to optimize the sensor performance. In the present work a sensitivity of 5340nm/RlU and resolution of 1.87×10−6RlU were found.","PeriodicalId":198716,"journal":{"name":"2017 25th Optical Fiber Sensors Conference (OFS)","volume":"66 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116951603","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
T. Grandal, S. Fraga, Gemma Castro, Esteban Vazquez, Ander Zomoza
In this paper a fiber optic metallic embedding technique is presented based on laser Brazing manufacturing process. The embedding strategy to follow by the laser Brazing, which consists in three steps, minimizes the thermal stress of the embedded fiber, relaxes microbending strains and reduces damage on the fiber. The minimum embedded fiber optic Ni coating total diameter is 237μm for a successful process with negligible optical loss on the fiber. Fiber Bragg Gratings were successfully embedded in metallic specimens and their strain response was in accordance with their specifications.
{"title":"Laser brazing metallic embedding technique for fiber optic sensors","authors":"T. Grandal, S. Fraga, Gemma Castro, Esteban Vazquez, Ander Zomoza","doi":"10.1117/12.2263974","DOIUrl":"https://doi.org/10.1117/12.2263974","url":null,"abstract":"In this paper a fiber optic metallic embedding technique is presented based on laser Brazing manufacturing process. The embedding strategy to follow by the laser Brazing, which consists in three steps, minimizes the thermal stress of the embedded fiber, relaxes microbending strains and reduces damage on the fiber. The minimum embedded fiber optic Ni coating total diameter is 237μm for a successful process with negligible optical loss on the fiber. Fiber Bragg Gratings were successfully embedded in metallic specimens and their strain response was in accordance with their specifications.","PeriodicalId":198716,"journal":{"name":"2017 25th Optical Fiber Sensors Conference (OFS)","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117070900","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Reinhardt, D. Lancelle, O. Hagendorf, M. Schultalbers, O. Magnor, P. Duenow
Blade tip timing is an upcoming technology to research possibilities of working point identification and phenomena like stall and blade vibrations for axial compressors. This method determines blade bendings for each individual compressor blade. Due to their high timing resolution optical sensors are often used in this field. Real blade bendings are often of very small amplitudes in the range of micrometers. So it's important to have a reference system that is as accurate as possible. This paper describes a method which guarantees a high resolution and high precision reference system to improve the results of blade tip timing.
{"title":"Improved reference system for high precision blade tip timing on axial compressors","authors":"R. Reinhardt, D. Lancelle, O. Hagendorf, M. Schultalbers, O. Magnor, P. Duenow","doi":"10.1117/12.2263295","DOIUrl":"https://doi.org/10.1117/12.2263295","url":null,"abstract":"Blade tip timing is an upcoming technology to research possibilities of working point identification and phenomena like stall and blade vibrations for axial compressors. This method determines blade bendings for each individual compressor blade. Due to their high timing resolution optical sensors are often used in this field. Real blade bendings are often of very small amplitudes in the range of micrometers. So it's important to have a reference system that is as accurate as possible. This paper describes a method which guarantees a high resolution and high precision reference system to improve the results of blade tip timing.","PeriodicalId":198716,"journal":{"name":"2017 25th Optical Fiber Sensors Conference (OFS)","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116005545","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
P. Shrestha, Yurim Park, Hyunseok Kwon, Chun-Gon Kim
A low velocity impact onto a composite structure can result in the occurrence of barely visible impact damage (BVID), which is difficult to detect. Therefore, the low velocity impact monitoring of composite structures is highly desirable for impact detection and localization. In this paper, low velocity impacts on a composite wing under a simulated wing loading condition were monitored using six multiplexed fiber Bragg grating (FBG) sensors and localized using error outlier based impact localization algorithm. The impact response signals from the FBG sensors were sampled at a rate of 100 kHz using high-speed interrogator. The impacts were localized with an average error of 18.4 mm.
{"title":"Low velocity impact monitoring of composite wing structure under simulated wing loading condition using fiber Bragg grating sensors","authors":"P. Shrestha, Yurim Park, Hyunseok Kwon, Chun-Gon Kim","doi":"10.1117/12.2267541","DOIUrl":"https://doi.org/10.1117/12.2267541","url":null,"abstract":"A low velocity impact onto a composite structure can result in the occurrence of barely visible impact damage (BVID), which is difficult to detect. Therefore, the low velocity impact monitoring of composite structures is highly desirable for impact detection and localization. In this paper, low velocity impacts on a composite wing under a simulated wing loading condition were monitored using six multiplexed fiber Bragg grating (FBG) sensors and localized using error outlier based impact localization algorithm. The impact response signals from the FBG sensors were sampled at a rate of 100 kHz using high-speed interrogator. The impacts were localized with an average error of 18.4 mm.","PeriodicalId":198716,"journal":{"name":"2017 25th Optical Fiber Sensors Conference (OFS)","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116309086","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
André D. Gomes, R. André, S. Warren-Smith, J. Dellith, M. Becker, M. Rothhardt, O. Frazão
A Mach-Zehnder interferometer was created from a cavity milled in the taper region next to a microfiber knot resonator. A focused ion beam was used to mill the cavity with 47.8 μm in length. The microfiber knot resonator was created from an 11 μm diameter taper, produced using a filament fusion splicer. After milling the cavity, the microfiber knot resonator spectrum is still visible. The final response of the presented sensor is a microfiber knot resonator spectrum modulated by the Mach-Zehnder interference spectrum. A preliminary result of −8935 ± 108 nm/RIU was obtained for the refractive index sensitivity of the cavity component in a refractive index range of n = 1.333 to 1.341. Simultaneous measurement of refractive index and temperature using this combined structure is a future goal.
{"title":"Combined microfiber knot resonator and focused ion beam-milled Mach-Zehnder interferometer for refractive index measurement","authors":"André D. Gomes, R. André, S. Warren-Smith, J. Dellith, M. Becker, M. Rothhardt, O. Frazão","doi":"10.1117/12.2265387","DOIUrl":"https://doi.org/10.1117/12.2265387","url":null,"abstract":"A Mach-Zehnder interferometer was created from a cavity milled in the taper region next to a microfiber knot resonator. A focused ion beam was used to mill the cavity with 47.8 μm in length. The microfiber knot resonator was created from an 11 μm diameter taper, produced using a filament fusion splicer. After milling the cavity, the microfiber knot resonator spectrum is still visible. The final response of the presented sensor is a microfiber knot resonator spectrum modulated by the Mach-Zehnder interference spectrum. A preliminary result of −8935 ± 108 nm/RIU was obtained for the refractive index sensitivity of the cavity component in a refractive index range of n = 1.333 to 1.341. Simultaneous measurement of refractive index and temperature using this combined structure is a future goal.","PeriodicalId":198716,"journal":{"name":"2017 25th Optical Fiber Sensors Conference (OFS)","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123612053","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Three different fibre Bragg grating strain sensors were tested for their suitability for measuring high strain. The sensor types were: a bare epoxied fibre Bragg grating, a standard fibre Bragg grating epoxied into a metal capillary and, finally, a metal coated fibre Bragg grating brazed into a metal capillary. The sensors were calibrated on a steel specimen up to 1400MPa (equivalent to 7.3mε). The results show that the bare epoxied Bragg grating and the metal packaged grating are suitable for measuring strains of this level.
测试了三种不同的光纤光栅应变传感器对高应变测量的适用性。传感器类型有:裸环氧化光纤布拉格光栅，环氧化成金属毛细管的标准光纤布拉格光栅，最后是钎焊成金属毛细管的金属涂层光纤布拉格光栅。传感器在高达1400MPa(相当于7.3 mm ε)的钢试样上进行校准。结果表明，裸环氧布拉格光栅和金属封装光栅均适用于该水平应变的测量。
{"title":"A comparison of brazed metal and epoxied fibre Bragg grating strain sensors under high strain regimes","authors":"I. Mckeeman, P. Niewczas, S. Khan","doi":"10.1117/12.2264997","DOIUrl":"https://doi.org/10.1117/12.2264997","url":null,"abstract":"Three different fibre Bragg grating strain sensors were tested for their suitability for measuring high strain. The sensor types were: a bare epoxied fibre Bragg grating, a standard fibre Bragg grating epoxied into a metal capillary and, finally, a metal coated fibre Bragg grating brazed into a metal capillary. The sensors were calibrated on a steel specimen up to 1400MPa (equivalent to 7.3mε). The results show that the bare epoxied Bragg grating and the metal packaged grating are suitable for measuring strains of this level.","PeriodicalId":198716,"journal":{"name":"2017 25th Optical Fiber Sensors Conference (OFS)","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121953199","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. L. Aldaba, Á. González-Vila, M. Debliquy, M. López-Amo, C. Caucheteur, D. Lahem
In this paper, we present the results of a new pH sensor based on a polyaniline (PAni) coating on the surface of a tilted fiber Bragg grating. The pH-sensitive PAni was deposited by in situ chemical oxidative polymerization. The performance of the fabricated pH sensor was tested and the obtained pH values were compared with the results obtained using a pH meter device. It was found that the sensor exhibits response to pH changes in the range of 2–12, achieving a sensitivity of 46 pm/pH with a maximum error due to the hysteresis effect of ±1.14 pH. The main advantages of this PAni-TFBG pH sensor are biochemical compatibility, temperature independence, long-term stability and remote real-time multipoint sensing features. This type of sensor could be used for biochemical applications, pipeline corrosion monitoring or remote-multipoint measurements.
{"title":"Polyaniline deposition on tilted fiber Bragg grating for pH sensing","authors":"A. L. Aldaba, Á. González-Vila, M. Debliquy, M. López-Amo, C. Caucheteur, D. Lahem","doi":"10.1117/12.2267524","DOIUrl":"https://doi.org/10.1117/12.2267524","url":null,"abstract":"In this paper, we present the results of a new pH sensor based on a polyaniline (PAni) coating on the surface of a tilted fiber Bragg grating. The pH-sensitive PAni was deposited by in situ chemical oxidative polymerization. The performance of the fabricated pH sensor was tested and the obtained pH values were compared with the results obtained using a pH meter device. It was found that the sensor exhibits response to pH changes in the range of 2–12, achieving a sensitivity of 46 pm/pH with a maximum error due to the hysteresis effect of ±1.14 pH. The main advantages of this PAni-TFBG pH sensor are biochemical compatibility, temperature independence, long-term stability and remote real-time multipoint sensing features. This type of sensor could be used for biochemical applications, pipeline corrosion monitoring or remote-multipoint measurements.","PeriodicalId":198716,"journal":{"name":"2017 25th Optical Fiber Sensors Conference (OFS)","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122140636","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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