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5602 KiB

Open AccessArticle

A High-Sensitive Pressure Sensor Using a Single-Mode Fiber Embedded Microbubble with Thin Film Characteristics

by Guanjun Wang, Xinglin Liu, Zhiguo Gui, Yongquan An, Jinyu Gu, Meiqin Zhang, Lu Yan, Gao Wang and Zhibin Wang

Sensors 2017, 17(6), 1192; https://doi.org/10.3390/s17061192 - 23 May 2017

Cited by 17 | Viewed by 6466

Abstract

A new fiber pressure sensor is proposed and analyzed in this paper. A commercial arc fusion splicer and pressure-assisted arc discharge technology are used here to fabricate a silica hollow microbubble from a common glass tube with the characteristics of a thin film. [...] Read more.

A new fiber pressure sensor is proposed and analyzed in this paper. A commercial arc fusion splicer and pressure-assisted arc discharge technology are used here to fabricate a silica hollow microbubble from a common glass tube with the characteristics of a thin film. Then the single mode fiber is embedded into the microbubble to form a fiber Fabry–Perot interferometer by measuring the reflected interference spectrum from the fiber tip and microbubble end. As the wall thickness of the micro-bubble can reach up to several micrometers, it can then be used for measuring the outer pressure with high sensitivity. The fabrication method has the merits of being simple, low in cost, and is easy to control. Experimental results show that its pressure sensitivity can reach 164.56 pm/kPa and the temperature sensitivity can reach 4 pm/°C. Therefore, it also has the advantage of being insensitive to temperature fluctuation. Full article

(This article belongs to the Special Issue Recent Advances in Fiber Bragg Grating Sensing)

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3893 KiB

Open AccessArticle

A Cost-Effective Geodetic Strainmeter Based on Dual Coaxial Cable Bragg Gratings

by Jihua Fu, Xu Wang, Tao Wei, Meng Wei and Yang Shen

Sensors 2017, 17(4), 842; https://doi.org/10.3390/s17040842 - 12 Apr 2017

Cited by 12 | Viewed by 4947

Abstract

Observations of surface deformation are essential for understanding a wide range of geophysical problems, including earthquakes, volcanoes, landslides, and glaciers. Current geodetic technologies, such as global positioning system (GPS), interferometric synthetic aperture radar (InSAR), borehole and laser strainmeters, are costly and limited in [...] Read more.

Observations of surface deformation are essential for understanding a wide range of geophysical problems, including earthquakes, volcanoes, landslides, and glaciers. Current geodetic technologies, such as global positioning system (GPS), interferometric synthetic aperture radar (InSAR), borehole and laser strainmeters, are costly and limited in their temporal or spatial resolutions. Here we present a new type of strainmeters based on the coaxial cable Bragg grating (CCBG) sensing technology that provides cost-effective strain measurements. Two CCBGs are introduced into the geodetic strainmeter: one serves as a sensor to measure the strain applied on it, and the other acts as a reference to detect environmental noises. By integrating the sensor and reference signals in a mixer, the environmental noises are minimized and a lower mixed frequency is obtained. The lower mixed frequency allows for measurements to be taken with a portable spectrum analyzer, rather than an expensive spectrum analyzer or a vector network analyzer (VNA). Analysis of laboratory experiments shows that the strain can be measured by the CCBG sensor, and the portable spectrum analyzer can make measurements with the accuracy similar to the expensive spectrum analyzer, whose relative error to the spectrum analyzer R3272 is less than ±0.4%. The outputs of the geodetic strainmeter show a linear relationship with the strains that the CCBG sensor experienced. The measured sensitivity of the geodetic strainmeter is about −0.082 kHz/με; it can cover a large dynamic measuring range up to 2%, and its nonlinear errors can be less than 5.3%. Full article

(This article belongs to the Special Issue Recent Advances in Fiber Bragg Grating Sensing)

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3707 KiB

Open AccessArticle

Application of FBG Sensing Technology in Stability Analysis of Geogrid-Reinforced Slope

by Yijie Sun, Hongzhong Xu, Peng Gu and Wenjie Hu

Sensors 2017, 17(3), 597; https://doi.org/10.3390/s17030597 - 15 Mar 2017

Cited by 29 | Viewed by 6706

Abstract

By installing FBG sensors on the geogrids, smart geogrids can both reinforce and monitor the stability for geogrid-reinforced slopes. In this paper, a geogrid-reinforced sand slope model test is conducted in the laboratory and fiber Bragg grating (FBG) sensing technology is used to [...] Read more.

By installing FBG sensors on the geogrids, smart geogrids can both reinforce and monitor the stability for geogrid-reinforced slopes. In this paper, a geogrid-reinforced sand slope model test is conducted in the laboratory and fiber Bragg grating (FBG) sensing technology is used to measure the strain distribution of the geogrid. Based on the model test, the performance of the reinforced soil slope is simulated by finite element software Midas-GTS, and the stability of the reinforced soil slope is analyzed by strength reduction method. The relationship between the geogrid strain and the factor of safety is set up. The results indicate that the measured strain and calculated results agree very well. The geogrid strain measured by FBG sensor can be applied to evaluate the stability of geogrid-reinforced sand slopes. Full article

(This article belongs to the Special Issue Recent Advances in Fiber Bragg Grating Sensing)

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1733 KiB

Open AccessArticle

A Micro Bubble Structure Based Fabry–Perot Optical Fiber Strain Sensor with High Sensitivity and Low-Cost Characteristics

by Lu Yan, Zhiguo Gui, Guanjun Wang, Yongquan An, Jinyu Gu, Meiqin Zhang, Xinglin Liu, Zhibin Wang, Gao Wang and Pinggang Jia

Sensors 2017, 17(3), 555; https://doi.org/10.3390/s17030555 - 9 Mar 2017

Cited by 50 | Viewed by 7122 | Correction

Abstract

A high-sensitivity, low-cost, ultrathin, hollow fiber micro bubble structure was proposed; such a bubble can be used to develop a high-sensitivity strain sensor based on a Fabry–Perot interferometer (FPI). The micro bubble is fabricated at the fiber tip by splicing a glass tube [...] Read more.

A high-sensitivity, low-cost, ultrathin, hollow fiber micro bubble structure was proposed; such a bubble can be used to develop a high-sensitivity strain sensor based on a Fabry–Perot interferometer (FPI). The micro bubble is fabricated at the fiber tip by splicing a glass tube to a single mode fiber (SMF) and then the glass tube is filled with gas in order to expand and form a micro bubble. The sensitivity of the strain sensor with a cavity length of about 155 μm and a bubble wall thickness of about 6 μm was measured to be up to 8.14 pm/μϵ. Full article

(This article belongs to the Special Issue Recent Advances in Fiber Bragg Grating Sensing)

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2219 KiB

Open AccessArticle

Study on the Deformation Measurement of the Cast-In-Place Large-Diameter Pile Using Fiber Bragg Grating Sensors

by Lei Gao, Kai Yang, Xiaorui Chen and Xiangjuan Yu

Sensors 2017, 17(3), 505; https://doi.org/10.3390/s17030505 - 3 Mar 2017

Cited by 22 | Viewed by 5849

Abstract

Compared with conventional piles such as the circle pile, the cast-in-place large-diameter pile (PCC pile) has many advantages: the lateral area of PCC pile is larger and the bearing capacity of PCC pile is higher. It is more cost-effective than other piles such [...] Read more.

Compared with conventional piles such as the circle pile, the cast-in-place large-diameter pile (PCC pile) has many advantages: the lateral area of PCC pile is larger and the bearing capacity of PCC pile is higher. It is more cost-effective than other piles such as square pile under the same condition. The deformation of the PCC pile is very important for its application. In order to obtain the deformation of the PCC pile, a new type of quasi-distributed optical fiber sensing technology named a fiber Bragg grating (FBG) is used to monitor the deformation of the PCC pile. The PCC model pile is made, the packaging process of the PCC model pile and the layout of fiber sensors are designed, and the strains of the PCC model pile based on FBG sensors are monitored. The strain of the PCC pile is analyzed by the static load test. The results show that FBG technology is successfully applied for monitoring the deformation of the PCC pile, the monitoring data is more useful for the PCC pile. It will provide a reference for the engineering applications. Full article

(This article belongs to the Special Issue Recent Advances in Fiber Bragg Grating Sensing)

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8857 KiB

Open AccessArticle

Dynamic Method of Neutral Axis Position Determination and Damage Identification with Distributed Long-Gauge FBG Sensors

by Yongsheng Tang and Zhongdao Ren

Sensors 2017, 17(2), 411; https://doi.org/10.3390/s17020411 - 20 Feb 2017

Cited by 19 | Viewed by 6193

Abstract

The neutral axis position (NAP) is a key parameter of a flexural member for structure design and safety evaluation. The accuracy of NAP measurement based on traditional methods does not satisfy the demands of structural performance assessment especially under live traffic loads. In [...] Read more.

The neutral axis position (NAP) is a key parameter of a flexural member for structure design and safety evaluation. The accuracy of NAP measurement based on traditional methods does not satisfy the demands of structural performance assessment especially under live traffic loads. In this paper, a new method to determine NAP is developed by using modal macro-strain (MMS). In the proposed method, macro-strain is first measured with long-gauge Fiber Bragg Grating (FBG) sensors; then the MMS is generated from the measured macro-strain with Fourier transform; and finally the neutral axis position coefficient (NAPC) is determined from the MMS and the neutral axis depth is calculated with NAPC. To verify the effectiveness of the proposed method, some experiments on FE models, steel beam and reinforced concrete (RC) beam were conducted. From the results, the plane section was first verified with MMS of the first bending mode. Then the results confirmed the high accuracy and stability for assessing NAP. The results also proved that the NAPC was a good indicator of local damage. In summary, with the proposed method, accurate assessment of flexural structures can be facilitated. Full article

(This article belongs to the Special Issue Recent Advances in Fiber Bragg Grating Sensing)

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5461 KiB

Open AccessArticle

Formation and Applications of the Secondary Fiber Bragg Grating

by Bai-Ou Guan, Yang Ran, Fu-Rong Feng and Long Jin

Sensors 2017, 17(2), 398; https://doi.org/10.3390/s17020398 - 18 Feb 2017

Cited by 13 | Viewed by 5819

Abstract

Being one of the most proven fiber optic devices, the fiber Bragg grating has developed continually to extend its applications, particularly in extreme environments. Accompanying the growth of Type-IIa Bragg gratings in some active fibers, a new resonance appears at the shorter wavelength. [...] Read more.

Being one of the most proven fiber optic devices, the fiber Bragg grating has developed continually to extend its applications, particularly in extreme environments. Accompanying the growth of Type-IIa Bragg gratings in some active fibers, a new resonance appears at the shorter wavelength. This new type of grating was named “secondary Bragg grating” (SBG). This paper describes the formation and applications of the SBGs. The formation of the SBG is attributed to the intracore Talbot-type-fringes as a result of multi-order diffractions of the inscribing beams. The SBG presents a variety of interesting characteristics, including dip merge, high-temperature resistance, distinct temperature response, and the strong higher-order harmonic reflection. These features enable its promising applications in fiber lasers and fiber sensing technology. Full article

(This article belongs to the Special Issue Recent Advances in Fiber Bragg Grating Sensing)

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5532 KiB

Open AccessArticle

Design of Novel FBG-Based Sensor of Differential Pressure with Magnetic Transfer

by Guohui Lyu, Guohang Che, Junqing Li, Xu Jiang, Keda Wang, Yueqiang Han and Laixu Gao

Sensors 2017, 17(2), 375; https://doi.org/10.3390/s17020375 - 15 Feb 2017

Cited by 7 | Viewed by 5550

Abstract

In this paper, a differential pressure sensor with magnetic transfer is proposed, in which the non-electric measurement based on the fiber Bragg grating (FBG) with the position limiting mechanism is implemented without the direct contact of the sensing unit with the measuring fluid. [...] Read more.

In this paper, a differential pressure sensor with magnetic transfer is proposed, in which the non-electric measurement based on the fiber Bragg grating (FBG) with the position limiting mechanism is implemented without the direct contact of the sensing unit with the measuring fluid. The test shows that the designed sensor is effective for measuring differential pressure in the range of 0~10 kPa with a sensitivity of 0.0112 nm/kPa, which can be used in environments with high temperature, strong corrosion and high overload measurements. Full article

(This article belongs to the Special Issue Recent Advances in Fiber Bragg Grating Sensing)

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1833 KiB

Open AccessArticle

Optical Sensor of Thermal Gas Flow Based on Fiber Bragg Grating

by Xu Jiang, Keda Wang, Junqing Li, Hui Zhan, Zhenan Song, Guohang Che and Guohui Lyu

Sensors 2017, 17(2), 374; https://doi.org/10.3390/s17020374 - 15 Feb 2017

Cited by 12 | Viewed by 5235

Abstract

This paper aims at solving the problem of explosion proof in measurement of thermal gas flow using electronic sensor by presenting a new type of flow sensor by optical fiber heating. A measuring unit based on fiber Bragg grating (FBG) for fluid temperature [...] Read more.

This paper aims at solving the problem of explosion proof in measurement of thermal gas flow using electronic sensor by presenting a new type of flow sensor by optical fiber heating. A measuring unit based on fiber Bragg grating (FBG) for fluid temperature and a unit for heat dissipation are designed to replace the traditional electronic sensors. The light in C band from the amplified spontaneous emission (ASE) light source is split, with one part used to heat the absorbing coating and the other part used in the signal processing unit. In the heating unit, an absorbing coating is introduced to replace the traditional resistance heating module to minimize the risk of explosion. The measurement results demonstrate a fine consistency between the flow and temperature difference in simulation. The method to enhance the measurement resolution of flow is also discussed. Full article

(This article belongs to the Special Issue Recent Advances in Fiber Bragg Grating Sensing)

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5293 KiB

Open AccessArticle

Localized Temperature Variations in Laser-Irradiated Composites with Embedded Fiber Bragg Grating Sensors

by R. Brian Jenkins, Peter Joyce and Deborah Mechtel

Sensors 2017, 17(2), 251; https://doi.org/10.3390/s17020251 - 27 Jan 2017

Cited by 15 | Viewed by 5400

Abstract

Fiber Bragg grating (FBG) temperature sensors are embedded in composites to detect localized temperature gradients resulting from high energy infrared laser radiation. The goal is to detect the presence of radiation on a composite structure as rapidly as possible and to identify its [...] Read more.

Fiber Bragg grating (FBG) temperature sensors are embedded in composites to detect localized temperature gradients resulting from high energy infrared laser radiation. The goal is to detect the presence of radiation on a composite structure as rapidly as possible and to identify its location, much the same way human skin senses heat. A secondary goal is to determine how a network of sensors can be optimized to detect thermal damage in laser-irradiated composite materials or structures. Initial tests are conducted on polymer matrix composites reinforced with either carbon or glass fiber with a single optical fiber embedded into each specimen. As many as three sensors in each optical fiber measure the temporal and spatial thermal response of the composite to high energy radiation incident on the surface. Additional tests use a 2 × 2 × 3 array of 12 sensors embedded in a carbon fiber/epoxy composite to simultaneously measure temperature variations at locations on the composite surface and through the thickness. Results indicate that FBGs can be used to rapidly detect temperature gradients in a composite and their location, even for a direct strike of laser radiation on a sensor, when high temperatures can cause a non-uniform thermal response and FBG decay. Full article

(This article belongs to the Special Issue Recent Advances in Fiber Bragg Grating Sensing)

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4733 KiB

Open AccessArticle

Ultrafast Fiber Bragg Grating Interrogation for Sensing in Detonation and Shock Wave Experiments

by George Rodriguez and Steve M. Gilbertson

Sensors 2017, 17(2), 248; https://doi.org/10.3390/s17020248 - 27 Jan 2017

Cited by 22 | Viewed by 6373

Abstract

Chirped ﬁber Bragg grating (CFBG) sensors coupled to high speed interrogation systems are described as robust diagnostic approaches to monitoring shock wave and detonation front propagation tracking events for use in high energy density shock physics applications. Taking advantage of the linear distributed [...] Read more.

Chirped ﬁber Bragg grating (CFBG) sensors coupled to high speed interrogation systems are described as robust diagnostic approaches to monitoring shock wave and detonation front propagation tracking events for use in high energy density shock physics applications. Taking advantage of the linear distributed spatial encoding of the spectral band in single-mode CFBGs, embedded ﬁber systems and associated photonic interrogation methodologies are shown as an effective approach to sensing shock and detonation-driven loading processes along the CFBG length. Two approaches, one that detects spectral changes in the integrated spectrum of the CFBG and another coherent pulse interrogation approach that fully resolves its spectral response, shows that 100-MHz–1-GHz interrogation rates are possible with spatial resolution along the CFBG in the 50 µm to sub-millimeter range depending on the combination of CFBG parameters (i.e., length, chirp rate, spectrum) and interrogator design speciﬁcs. Results from several dynamic tests are used to demonstrate the performance of these high speed systems for shock and detonation propagation tracking under strong and weak shock pressure loading: (1) linear detonation front tracking in the plastic bonded explosive (PBX) PBX-9501; (2) tracking of radial decaying shock with crossover to non-destructive CFBG response; (3) shock wave tracking along an aluminum cylinder wall under weak loading accompanied by dynamic strain effects in the CFBG sensor. Full article

(This article belongs to the Special Issue Recent Advances in Fiber Bragg Grating Sensing)

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2915 KiB

Open AccessArticle

Influence of Individual Differences on the Calculation Method for FBG-Type Blood Pressure Sensors

by Shouhei Koyama, Hiroaki Ishizawa, Keisaku Fujimoto, Shun Chino and Yuka Kobayashi

Sensors 2017, 17(1), 48; https://doi.org/10.3390/s17010048 - 28 Dec 2016

Cited by 37 | Viewed by 6289

Abstract

In this paper, we propose a blood pressure calculation and associated measurement method that by using a fiber Bragg grating (FBG) sensor. There are several points at which the pulse can be measured on the surface of the human body, and when a [...] Read more.

In this paper, we propose a blood pressure calculation and associated measurement method that by using a fiber Bragg grating (FBG) sensor. There are several points at which the pulse can be measured on the surface of the human body, and when a FBG sensor located at any of these points, the pulse wave signal can be measured. The measured waveform is similar to the acceleration pulse wave. The pulse wave signal changes depending on several factors, including whether or not the individual is healthy and/or elderly. The measured pulse wave signal can be used to calculate the blood pressure using a calibration curve, which is constructed by a partial least squares (PLS) regression analysis using a reference blood pressure and the pulse wave signal. In this paper, we focus on the influence of individual differences from calculated blood pressure based on each calibration curve. In our study, the calculated blood pressure from both the individual and overall calibration curves were compared, and our results show that the calculated blood pressure based on the overall calibration curve had a lower measurement accuracy than that based on an individual calibration curve. We also found that the influence of the individual differences on the calculated blood pressure when using the FBG sensor method were very low. Therefore, the FBG sensor method that we developed for measuring the blood pressure was found to be suitable for use by many people. Full article

(This article belongs to the Special Issue Recent Advances in Fiber Bragg Grating Sensing)

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4870 KiB

Open AccessArticle

The Longitudinal Force Measurement of CWR Tracks with Hetero-Cladding FBG Sensors: A Proof of Concept

by Li-Yang Shao, Meng Zhang, Kaize Xie, Xinpu Zhang, Ping Wang and Lianshan Yan

Sensors 2016, 16(12), 2184; https://doi.org/10.3390/s16122184 - 18 Dec 2016

Cited by 12 | Viewed by 5028

Abstract

A new method has been proposed to accurately determine longitudinal additional force in continuous welded rail (CWR) on bridges via hetero-cladding fiber Bragg grating (HC-FBG) sensors. The HC-FBG sensor consists of two FBGs written in the same type of fiber but with different [...] Read more.

A new method has been proposed to accurately determine longitudinal additional force in continuous welded rail (CWR) on bridges via hetero-cladding fiber Bragg grating (HC-FBG) sensors. The HC-FBG sensor consists of two FBGs written in the same type of fiber but with different cladding diameters. The HC-FBGs have the same temperature sensitivity but different strain sensitivity because of the different areas of the cross section. The differential strain coefficient is defined as the relative wavelength differences of two FBGs with the change of applied longitudinal force. In the verification experiment in the lab, the HC-FBGs were attached on a section of rail model of which the material property is the same as that of rail on line. The temperature and differential strain sensitivity were calibrated using a universal testing machine. As shown by the test results, the linearity between the relative wavelength difference and the longitudinal additional force is greater than 0.9999. The differential strain sensitivity is 4.85 × 10⁻⁶/N. Moreover, the relative wavelength difference is not affected by the temperature change. Compared to the theoretical results, the accumulated error is controlled within 5.0%. Full article

(This article belongs to the Special Issue Recent Advances in Fiber Bragg Grating Sensing)

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2445 KiB

Open AccessArticle

An Optical Fiber Sensor and Its Application in UAVs for Current Measurements

by Felipe S. Delgado, João P. Carvalho, Thiago V. N. Coelho and Alexandre B. Dos Santos

Sensors 2016, 16(11), 1800; https://doi.org/10.3390/s16111800 - 27 Oct 2016

Cited by 19 | Viewed by 5755

Abstract

In this paper, we propose and experimentally investigate an optical sensor based on a novel combination of a long-period fiber grating (LPFG) with a permanent magnet to measure electrical current in unmanned aerial vehicles (UAVs). The proposed device uses a neodymium magnet attached [...] Read more.

In this paper, we propose and experimentally investigate an optical sensor based on a novel combination of a long-period fiber grating (LPFG) with a permanent magnet to measure electrical current in unmanned aerial vehicles (UAVs). The proposed device uses a neodymium magnet attached to the grating structure, which suffers from an electromagnetic force produced when the current flows in the wire of the UAV engine. Therefore, it causes deformation on the sensor and thus, different shifts occur in the resonant bands of the transmission spectrum of the LPFG. Finally, the results show that it is possible to monitor electrical current throughout the entire operating range of the UAV engine from 0 A to 10 A in an effective and practical way with good linearity, reliability and response time, which are desirable characteristics in electrical current sensing. Full article

(This article belongs to the Special Issue Recent Advances in Fiber Bragg Grating Sensing)

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3848 KiB

Open AccessArticle

Research on High Sensitive D-Shaped FBG Hydrogen Sensors in Power Transformer Oil

by Ying-Ting Luo, Hong-Bin Wang, Guo-Ming Ma, Hong-Tu Song, Chengrong Li and Jun Jiang

Sensors 2016, 16(10), 1641; https://doi.org/10.3390/s16101641 - 4 Oct 2016

Cited by 26 | Viewed by 6595

Abstract

Dissolved hydrogen is a symbol gas decomposed by power transformer oil for electrical faults such as overheat or partial discharges. A novel D-shaped fiber Bragg grating (D-FBG) sensor is herein proposed and was fabricated with magnetron sputtering to measure the dissolved hydrogen concentration [...] Read more.

Dissolved hydrogen is a symbol gas decomposed by power transformer oil for electrical faults such as overheat or partial discharges. A novel D-shaped fiber Bragg grating (D-FBG) sensor is herein proposed and was fabricated with magnetron sputtering to measure the dissolved hydrogen concentration in power transformer oil in this paper. Different from the RI (refractive index)-based effect, D-FBG in this case is sensitive to curvature caused by stress from sensing coating, leading to Bragg wavelength shifts accordingly. The relationship between the D-FBG wavelength shift and dissolved hydrogen concentration in oil was measured experimentally in the laboratory. The detected sensitivity could be as high as 1.96 μL/L at every 1-pm wavelength shift. The results proved that a simple, polished FBG-based hydrogen sensor provides a linear measuring characteristic in the range of low hydrogen concentrations in transformer oil. Moreover, the stable hydrogen sensing performance was investigated by X-ray diffraction analysis. Full article

(This article belongs to the Special Issue Recent Advances in Fiber Bragg Grating Sensing)

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3855 KiB

Open AccessArticle

Strain Modal Analysis of Small and Light Pipes Using Distributed Fibre Bragg Grating Sensors

by Jun Huang, Zude Zhou, Lin Zhang, Juntao Chen, Chunqian Ji and Duc Truong Pham

Sensors 2016, 16(10), 1583; https://doi.org/10.3390/s16101583 - 25 Sep 2016

Cited by 26 | Viewed by 9679

Abstract

Vibration fatigue failure is a critical problem of hydraulic pipes under severe working conditions. Strain modal testing of small and light pipes is a good option for dynamic characteristic evaluation, structural health monitoring and damage identification. Unique features such as small size, light [...] Read more.

Vibration fatigue failure is a critical problem of hydraulic pipes under severe working conditions. Strain modal testing of small and light pipes is a good option for dynamic characteristic evaluation, structural health monitoring and damage identification. Unique features such as small size, light weight, and high multiplexing capability enable Fibre Bragg Grating (FBG) sensors to measure structural dynamic responses where sensor size and placement are critical. In this paper, experimental strain modal analysis of pipes using distributed FBG sensors ispresented. Strain modal analysis and parameter identification methods are introduced. Experimental strain modal testing and finite element analysis for a cantilever pipe have been carried out. The analysis results indicate that the natural frequencies and strain mode shapes of the tested pipe acquired by FBG sensors are in good agreement with the results obtained by a reference accelerometer and simulation outputs. The strain modal parameters of a hydraulic pipe were obtained by the proposed strain modal testing method. FBG sensors have been shown to be useful in the experimental strain modal analysis of small and light pipes in mechanical, aeronautic and aerospace applications. Full article

(This article belongs to the Special Issue Recent Advances in Fiber Bragg Grating Sensing)

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9274 KiB

Open AccessArticle

Using Custom Fiber Bragg Grating-Based Sensors to Monitor Artificial Landslides

by Qinghua Zhang, Yuan Wang, Yangyang Sun, Lei Gao, Zhenglin Zhang, Wenyuan Zhang, Pengchong Zhao and Yin Yue

Sensors 2016, 16(9), 1417; https://doi.org/10.3390/s16091417 - 2 Sep 2016

Cited by 31 | Viewed by 6772

Abstract

Four custom fiber Bragg grating (FBG)-based sensors are developed to monitor an artificial landslide located in Nanjing, China. The sensors are composed of a rod and two FBGs. Based on the strength of the rods, two sensors are referred to as “hard sensors” [...] Read more.

Four custom fiber Bragg grating (FBG)-based sensors are developed to monitor an artificial landslide located in Nanjing, China. The sensors are composed of a rod and two FBGs. Based on the strength of the rods, two sensors are referred to as “hard sensors” (Sensor 1 and Sensor 2), the other two are referred to as “soft sensors” (Sensor 3 and Sensor 4). The two FBGs are fixed on each sensor rod at distances of 50 cm and 100 cm from the top of the rod (an upper FBG and a lower FBG). In the experiment presented in this paper, the sensors are installed on a slope on which an artificial landslide is generated through both machine-based and manual excavation. The fiber sensing system consists of the four custom FBG-based sensors, optical fiber, a static fiber grating demodulation instrument (SM125), and a PC with the necessary software. Experimental data was collected in the presence of an artificial landslide, and the results show that the lower FBGs are more sensitive than the upper FBGs for all four of the custom sensors. It was also found that Sensor 2 and Sensor 4 are more capable of monitoring small-scale landslides than Sensor 1 and Sensor 3, and this is mainly due to their placement location with respect to the landslide. The stronger rods used in the hard sensors make them more adaptable to the harsh environments of large landslides. Thus, hard sensors should be fixed near the landslide, while soft sensors should be placed farther away from the landslide. In addition, a clear tendency of strain variation can be detected by the soft sensors, which can be used to predict landslides and raise a hazard alarm. Full article

(This article belongs to the Special Issue Recent Advances in Fiber Bragg Grating Sensing)

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4174 KiB

Open AccessArticle

Investigation of a Fiberoptic Device Based on a Long Period Grating in a Ring Resonator

by Cinzia Corcione, Benedetto Troia, Francesco De Leonardis and Vittorio M. N. Passaro

Sensors 2016, 16(9), 1357; https://doi.org/10.3390/s16091357 - 24 Aug 2016

Cited by 3 | Viewed by 6245

Abstract

A fiberoptic architecture based on a ring resonator (RR) including a typical long period grating (LPG) was investigated. The interactions between the fundamental core mode (LP₀₁ or HE₁₁) coupled to the RR and the cladding mode (LP₀₈ [...] Read more.

A fiberoptic architecture based on a ring resonator (RR) including a typical long period grating (LPG) was investigated. The interactions between the fundamental core mode (LP₀₁ or HE₁₁) coupled to the RR and the cladding mode (LP₀₈), excited into the cavity by means of the LPG, allow a peculiar spectral response characterized by two splitting resonances to be achieved. The new LPGRR architecture is investigated theoretically and a mathematical modelling based on the transfer matrix method (TMM) is proposed. The theoretical results are compared with the experiments measured by an open-loop LPG, while the performance of the relative LPGRR was estimated by a theoretical parametric analysis. Finally, an overview of the possible LPGRR sensing applications is provided by investigating the features of a strain sensor operating in different environmental conditions. Full article

(This article belongs to the Special Issue Recent Advances in Fiber Bragg Grating Sensing)

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4959 KiB

Open AccessArticle

The Reusable Load Cell with Protection Applied for Online Monitoring of Overhead Transmission Lines Based on Fiber Bragg Grating

by Guoming Ma, Naiqiang Mao, Yabo Li, Jun Jiang, Hongyang Zhou and Chengrong Li

Sensors 2016, 16(6), 922; https://doi.org/10.3390/s16060922 - 21 Jun 2016

Cited by 25 | Viewed by 6939

Abstract

Heavy ice coating of high–voltage overhead transmission lines may lead to conductor breakage and tower collapse causing the unexpected interrupt of power supply. The optical load cell applied in ice monitoring systems is immune to electromagnetic interference and has no need of a [...] Read more.

Heavy ice coating of high–voltage overhead transmission lines may lead to conductor breakage and tower collapse causing the unexpected interrupt of power supply. The optical load cell applied in ice monitoring systems is immune to electromagnetic interference and has no need of a power supply on site. Therefore, it has become a hot research topic in China and other countries. In this paper, to solve the problem of eccentric load in measurement, we adopt the shearing structure with additional grooves to improve the strain distribution and acquire good repeatability. Then, the fiber Bragg grating (FBG) with a permanent weldable package are mounted onto the front/rear groove of the elastic element by spot welding, the direction deviation of FBGs is 90° from each other to achieve temperature compensation without an extra FBG. After that, protection parts are designed to guarantee high sensitivity for a light load condition and industrial safety under a heavy load up to 65 kN. The results of tension experiments indicate that the sensitivity and resolution of the load cell is 0.1285 pm/N and 7.782 N in the conventional measuring range (0–10 kN). Heavy load tension experiments prove that the protection structure works and the sensitivity and resolution are not changed after several high load (65 kN) cycles. In addition, the experiment shows that the resolution of the sensor is 87.79 N in the large load range, allowing the parameter to be used in heavy icing monitoring. Full article

(This article belongs to the Special Issue Recent Advances in Fiber Bragg Grating Sensing)

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Review

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3556 KiB

Open AccessReview

Optical Fiber Grating Hydrogen Sensors: A Review

by Jixiang Dai, Li Zhu, Gaopeng Wang, Feng Xiang, Yuhuan Qin, Min Wang and Minghong Yang

Sensors 2017, 17(3), 577; https://doi.org/10.3390/s17030577 - 12 Mar 2017

Cited by 67 | Viewed by 8424

Abstract

In terms of hydrogen sensing and detection, optical fiber hydrogen sensors have been a research issue due to their intrinsic safety and good anti-electromagnetic interference. Among these sensors, hydrogen sensors consisting of fiber grating coated with sensitive materials have attracted intensive research interests [...] Read more.

In terms of hydrogen sensing and detection, optical fiber hydrogen sensors have been a research issue due to their intrinsic safety and good anti-electromagnetic interference. Among these sensors, hydrogen sensors consisting of fiber grating coated with sensitive materials have attracted intensive research interests due to their good reliability and distributed measurements. This review paper mainly focuses on optical fiber hydrogen sensors associated with fiber gratings and various materials. Their configurations and sensing performances proposed by different groups worldwide are reviewed, compared and discussed in this paper. Meanwhile, the challenges for fiber grating hydrogen sensors are also addressed. Full article

(This article belongs to the Special Issue Recent Advances in Fiber Bragg Grating Sensing)

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Fabrication of Polymer Optical Fibre (POF) Gratings

by Yanhua Luo, Binbin Yan, Qijin Zhang, Gang-Ding Peng, Jianxiang Wen and Jianzhong Zhang

Sensors 2017, 17(3), 511; https://doi.org/10.3390/s17030511 - 4 Mar 2017

Cited by 55 | Viewed by 7223

Abstract

Gratings inscribed in polymer optical fibre (POF) have attracted remarkable interest for many potential applications due to their distinctive properties. This paper overviews the current state of fabrication of POF gratings since their first demonstration in 1999. In particular we summarize and discuss [...] Read more.

Gratings inscribed in polymer optical fibre (POF) have attracted remarkable interest for many potential applications due to their distinctive properties. This paper overviews the current state of fabrication of POF gratings since their first demonstration in 1999. In particular we summarize and discuss POF materials, POF photosensitivity, techniques and issues of fabricating POF gratings, as well as various types of POF gratings. Full article

(This article belongs to the Special Issue Recent Advances in Fiber Bragg Grating Sensing)

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3969 KiB

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FBG-Based Monitoring of Geohazards: Current Status and Trends

by Hong-Hu Zhu, Bin Shi and Cheng-Cheng Zhang

Sensors 2017, 17(3), 452; https://doi.org/10.3390/s17030452 - 24 Feb 2017

Cited by 133 | Viewed by 12769

Abstract

In recent years, natural and anthropogenic geohazards have occured frequently all over the world, and field monitoring is becoming an increasingly important task to mitigate these risks. However, conventional geotechnical instrumentations for monitoring geohazards have a number of weaknesses, such as low accuracy, [...] Read more.

In recent years, natural and anthropogenic geohazards have occured frequently all over the world, and field monitoring is becoming an increasingly important task to mitigate these risks. However, conventional geotechnical instrumentations for monitoring geohazards have a number of weaknesses, such as low accuracy, poor durability, and high sensitivity to environmental interferences. In this aspect, fiber Bragg grating (FBG), as a popular fiber optic sensing technology, has gained an explosive amount of attention. Based on this technology, quasi-distributed sensing systems have been established to perform real-time monitoring and early warning of landslides, debris flows, land subsidence, earth fissures and so on. In this paper, the recent research and development activities of applying FBG systems to monitor different types of geohazards, especially those triggered by human activities, are critically reviewed. The working principles of newly developed FBG sensors are briefly introduced, and their features are summarized. This is followed by a discussion of recent case studies and lessons learned, and some critical problems associated with field implementation of FBG-based monitoring systems. Finally the challenges and future trends in this research area are presented. Full article

(This article belongs to the Special Issue Recent Advances in Fiber Bragg Grating Sensing)

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Fiber Bragg Grating Sensors for the Oil Industry

by Xueguang Qiao, Zhihua Shao, Weijia Bao and Qiangzhou Rong

Sensors 2017, 17(3), 429; https://doi.org/10.3390/s17030429 - 23 Feb 2017

Cited by 170 | Viewed by 14410

Abstract

With the oil and gas industry growing rapidly, increasing the yield and profit require advances in technology for cost-effective production in key areas of reservoir exploration and in oil-well production-management. In this paper we review our group’s research into fiber Bragg gratings (FBGs) [...] Read more.

With the oil and gas industry growing rapidly, increasing the yield and profit require advances in technology for cost-effective production in key areas of reservoir exploration and in oil-well production-management. In this paper we review our group’s research into fiber Bragg gratings (FBGs) and their applications in the oil industry, especially in the well-logging field. FBG sensors used for seismic exploration in the oil and gas industry need to be capable of measuring multiple physical parameters such as temperature, pressure, and acoustic waves in a hostile environment. This application requires that the FBG sensors display high sensitivity over the broad vibration frequency range of 5 Hz to 2.5 kHz, which contains the important geological information. We report the incorporation of mechanical transducers in the FBG sensors to enable enhance the sensors’ amplitude and frequency response. Whenever the FBG sensors are working within a well, they must withstand high temperatures and high pressures, up to 175 °C and 40 Mpa or more. We use femtosecond laser side-illumination to ensure that the FBGs themselves have the high temperature resistance up to 1100 °C. Using FBG sensors combined with suitable metal transducers, we have experimentally realized high- temperature and pressure measurements up to 400 °C and 100 Mpa. We introduce a novel technology of ultrasonic imaging of seismic physical models using FBG sensors, which is superior to conventional seismic exploration methods. Compared with piezoelectric transducers, FBG ultrasonic sensors demonstrate superior sensitivity, more compact structure, improved spatial resolution, high stability and immunity to electromagnetic interference (EMI). In the last section, we present a case study of a well-logging field to demonstrate the utility of FBG sensors in the oil and gas industry. Full article

(This article belongs to the Special Issue Recent Advances in Fiber Bragg Grating Sensing)

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