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17 pages, 11683 KiB

Open AccessArticle

Selection and Characterization of Packaged FBG Sensors for Offshore Applications

by Lei Wu, Muneesh Maheshwari, Yaowen Yang and Wensheng Xiao

Sensors 2018, 18(11), 3963; https://doi.org/10.3390/s18113963 - 15 Nov 2018

Cited by 22 | Viewed by 4482

Abstract

With the development in the exploitation of maritime resources, the structural health monitoring (SHM) of offshore structures becomes necessary. This study focuses on addressing the practical issues of application of fiber Bragg grating (FBG) sensors for the SHM of offshore structures, in particular [...] Read more.

With the development in the exploitation of maritime resources, the structural health monitoring (SHM) of offshore structures becomes necessary. This study focuses on addressing the practical issues of application of fiber Bragg grating (FBG) sensors for the SHM of offshore structures, in particular an FPSO (floating, production, storage, and offloading unit) vessel. Due to the harsh marine environment and tough working conditions, the FBG sensors must have sufficient protection and good repeatability for long-term monitoring. Thorough research has been conducted to identify the most suitable, commercially available protection packaging for FBG sensors for offshore applications. Further, the performance of the selected FBG sensor packaging is tested under conditions of strong sunlight, heavy rain, and salty water in order to emulate the marine environment. Moreover, the installation method of the packaged FBG sensors is equally important, as it ensures the repeatability and durability of the sensors for their long-term performance. It is shown that the packaged FBG sensors can be installed using resin-based epoxy to maintain the repeatability of the sensor over the long-term. Further, the packaged FBG sensors are installed and tested on a simple FPSO model. The experimental results under full load and ballast draft conditions show that the proposed FBG sensors are competent for the SHM of offshore structures. Full article

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

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15 pages, 5758 KiB

Open AccessArticle

Application of Fiber Bragg Grating Acoustic Emission Sensors in Thin Polymer-Bonded Explosives

by Tao Fu, Peng Wei, Xiaole Han and Qingbo Liu

Sensors 2018, 18(11), 3778; https://doi.org/10.3390/s18113778 - 5 Nov 2018

Cited by 12 | Viewed by 3462

Abstract

Fiber Bragg grating (FBG) acoustic emission (AE) sensors have been used in many applications. In this paper, based on an FBG AE sensor, the sensing principle of the interaction between the AE wave and the sensor is introduced. Then, the directionality of the [...] Read more.

Fiber Bragg grating (FBG) acoustic emission (AE) sensors have been used in many applications. In this paper, based on an FBG AE sensor, the sensing principle of the interaction between the AE wave and the sensor is introduced. Then, the directionality of the FBG AE sensor on the surface of a thin polymer-bonded explosive (PBX) material is studied. Finally, the time coefficient location method is proposed to correct the AE time detected by the FBG AE sensor, thereby improving the accuracy of location experiments. Full article

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

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12 pages, 1633 KiB

Open AccessArticle

Simultaneous Vector Bend and Temperature Sensing Based on a Polymer and Silica Optical Fibre Grating Pair

by Binbin Yan, Guoqiang Liu, Jun He, Yanhua Luo, Liwei Yang, Haifeng Qi, Xinzhu Sang, Kuiru Wang, Chongxiu Yu, Jinhui Yuan and Gang-Ding Peng

Sensors 2018, 18(10), 3507; https://doi.org/10.3390/s18103507 - 17 Oct 2018

Cited by 7 | Viewed by 2926

Abstract

The bending response of polymer optical fibre Bragg grating (POFBG) and silica optical fibre Bragg grating (SOFBG) mounted on a brass beam have been systematically studied and compared. The results indicate that POFBG has higher (almost twice as much) bend sensitivity than SOFBG. [...] Read more.

The bending response of polymer optical fibre Bragg grating (POFBG) and silica optical fibre Bragg grating (SOFBG) mounted on a brass beam have been systematically studied and compared. The results indicate that POFBG has higher (almost twice as much) bend sensitivity than SOFBG. Based on the difference between the bend and temperature sensitivity of POFBG and SOFBG, a new method of measuring vector bend and temperature simultaneously was proposed by using a hybrid sensor head with series connection of one POFBG and one SOFBG with different Bragg wavelengths. It provides high sensitivity and resolution for sensing bend and temperature changes simultaneously and independently. The proposed sensor can find some applications in the fields where high sensitivity for both bend and temperature measurements are required. Full article

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

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12 pages, 3285 KiB

Open AccessArticle

Study on the Optimal Groove Shape and Glue Material for Fiber Bragg Grating Measuring Bolts

by Yiming Zhao, Nong Zhang, Guangyao Si and Xuehua Li

Sensors 2018, 18(6), 1799; https://doi.org/10.3390/s18061799 - 2 Jun 2018

Cited by 13 | Viewed by 4070

Abstract

Fiber Bragg grating (FBG) measuring bolts, as a useful tool to evaluate the behaviors of steel bolts in underground engineering, can be manufactured by gluing the FBG sensors inside the grooves, which are usually symmetrical cuts along the steel bolt rod. The selection [...] Read more.

Fiber Bragg grating (FBG) measuring bolts, as a useful tool to evaluate the behaviors of steel bolts in underground engineering, can be manufactured by gluing the FBG sensors inside the grooves, which are usually symmetrical cuts along the steel bolt rod. The selection of the cut shape and the glue types could perceivably affect the final supporting strength of the bolts. Unfortunately, the impact of cut shape and glue type on bolting strength is not yet clear. In this study, based on direct tension tests, full tensile load–displacement curves of rock bolts with different groove shapes were obtained and analyzed. The effects of groove shape on the bolt strength were discussed, and the stress redistribution in the cross-section of a rock bolt with different grooves was simulated using ANSYS. The results indicated that the trapezoidal groove is best for manufacturing the FBG bolt due to its low reduction of supporting strength. Four types of glues commonly used for the FBG sensors were assessed by conducting tensile tests on the mechanical testing and simulation system and the static and dynamic optical interrogators system. Using linear regression analysis, the relationship between the reflected wavelength of FBG sensors and tensile load was obtained. Practical recommendations for glue selection in engineering practice are also provided. Full article

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

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12 pages, 2998 KiB

Open AccessArticle

Sensitivity Enhancement of FBG-Based Strain Sensor

by Ruiya Li, Yiyang Chen, Yuegang Tan, Zude Zhou, Tianliang Li and Jian Mao

Sensors 2018, 18(5), 1607; https://doi.org/10.3390/s18051607 - 17 May 2018

Cited by 74 | Viewed by 7704

Abstract

A novel fiber Bragg grating (FBG)-based strain sensor with a high-sensitivity is presented in this paper. The proposed FBG-based strain sensor enhances sensitivity by pasting the FBG on a substrate with a lever structure. This typical mechanical configuration mechanically amplifies the strain of [...] Read more.

A novel fiber Bragg grating (FBG)-based strain sensor with a high-sensitivity is presented in this paper. The proposed FBG-based strain sensor enhances sensitivity by pasting the FBG on a substrate with a lever structure. This typical mechanical configuration mechanically amplifies the strain of the FBG to enhance overall sensitivity. As this mechanical configuration has a high stiffness, the proposed sensor can achieve a high resonant frequency and a wide dynamic working range. The sensing principle is presented, and the corresponding theoretical model is derived and validated. Experimental results demonstrate that the developed FBG-based strain sensor achieves an enhanced strain sensitivity of 6.2 pm/με, which is consistent with the theoretical analysis result. The strain sensitivity of the developed sensor is 5.2 times of the strain sensitivity of a bare fiber Bragg grating strain sensor. The dynamic characteristics of this sensor are investigated through the finite element method (FEM) and experimental tests. The developed sensor exhibits an excellent strain-sensitivity-enhancing property in a wide frequency range. The proposed high-sensitivity FBG-based strain sensor can be used for small-amplitude micro-strain measurement in harsh industrial environments. Full article

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

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16 pages, 47907 KiB

Open AccessArticle

A Fiber Bragg Grating Interrogation System with Self-Adaption Threshold Peak Detection Algorithm

by Weifang Zhang, Yingwu Li, Bo Jin, Feifei Ren, Hongxun Wang and Wei Dai

Sensors 2018, 18(4), 1140; https://doi.org/10.3390/s18041140 - 8 Apr 2018

Cited by 8 | Viewed by 4912

Abstract

A Fiber Bragg Grating (FBG) interrogation system with a self-adaption threshold peak detection algorithm is proposed and experimentally demonstrated in this study. This system is composed of a field programmable gate array (FPGA) and advanced RISC machine (ARM) platform, tunable Fabry–Perot (F–P) filter [...] Read more.

A Fiber Bragg Grating (FBG) interrogation system with a self-adaption threshold peak detection algorithm is proposed and experimentally demonstrated in this study. This system is composed of a field programmable gate array (FPGA) and advanced RISC machine (ARM) platform, tunable Fabry–Perot (F–P) filter and optical switch. To improve system resolution, the F–P filter was employed. As this filter is non-linear, this causes the shifting of central wavelengths with the deviation compensated by the parts of the circuit. Time-division multiplexing (TDM) of FBG sensors is achieved by an optical switch, with the system able to realize the combination of 256 FBG sensors. The wavelength scanning speed of 800 Hz can be achieved by a FPGA+ARM platform. In addition, a peak detection algorithm based on a self-adaption threshold is designed and the peak recognition rate is 100%. Experiments with different temperatures were conducted to demonstrate the effectiveness of the system. Four FBG sensors were examined in the thermal chamber without stress. When the temperature changed from 0 °C to 100 °C, the degree of linearity between central wavelengths and temperature was about 0.999 with the temperature sensitivity being 10 pm/°C. The static interrogation precision was able to reach 0.5 pm. Through the comparison of different peak detection algorithms and interrogation approaches, the system was verified to have an optimum comprehensive performance in terms of precision, capacity and speed. Full article

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

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13 pages, 9062 KiB

Open AccessArticle

A Newly Designed Fiber-Optic Based Earth Pressure Transducer with Adjustable Measurement Range

by Hou-Zhen Wei, Dong-Sheng Xu and Qing-Shan Meng

Sensors 2018, 18(4), 932; https://doi.org/10.3390/s18040932 - 21 Mar 2018

Cited by 26 | Viewed by 5296

Abstract

A novel fiber-optic based earth pressure sensor (FPS) with an adjustable measurement range and high sensitivity is developed to measure earth pressures for civil infrastructures. The new FPS combines a cantilever beam with fiber Bragg grating (FBG) sensors and a flexible membrane. Compared [...] Read more.

A novel fiber-optic based earth pressure sensor (FPS) with an adjustable measurement range and high sensitivity is developed to measure earth pressures for civil infrastructures. The new FPS combines a cantilever beam with fiber Bragg grating (FBG) sensors and a flexible membrane. Compared with a traditional pressure transducer with a dual diaphragm design, the proposed FPS has a larger measurement range and shows high accuracy. The working principles, parameter design, fabrication methods, and laboratory calibration tests are explained in this paper. A theoretical solution is derived to obtain the relationship between the applied pressure and strain of the FBG sensors. In addition, a finite element model is established to analyze the mechanical behavior of the membrane and the cantilever beam and thereby obtain optimal parameters. The cantilever beam is 40 mm long, 15 mm wide, and 1 mm thick. The whole FPS has a diameter of 100 mm and a thickness of 30 mm. The sensitivity of the FPS is 0.104 kPa/με. In addition, automatic temperature compensation can be achieved. The FPS’s sensitivity, physical properties, and response to applied pressure are extensively examined through modeling and experiments. The results show that the proposed FPS has numerous potential applications in soil pressure measurement. Full article

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

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Review

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32 pages, 3444 KiB

Open AccessReview

Review of Chirped Fiber Bragg Grating (CFBG) Fiber-Optic Sensors and Their Applications

by Daniele Tosi

Sensors 2018, 18(7), 2147; https://doi.org/10.3390/s18072147 - 4 Jul 2018

Cited by 115 | Viewed by 14059

Abstract

Fiber Bragg Gratings (FBGs) are one of the most popular technology within fiber-optic sensors, and they allow the measurement of mechanical, thermal, and physical parameters. In recent years, a strong emphasis has been placed on the fabrication and application of chirped FBGs (CFBGs), [...] Read more.

Fiber Bragg Gratings (FBGs) are one of the most popular technology within fiber-optic sensors, and they allow the measurement of mechanical, thermal, and physical parameters. In recent years, a strong emphasis has been placed on the fabrication and application of chirped FBGs (CFBGs), which are characterized by a non-uniform modulation of the refractive index within the core of an optical fiber. A CFBG behaves as a cascade of FBGs, each one reflecting a narrow spectrum that depends on temperature and/or strain. The key characteristic of CFBGs is that their reflection spectrum depends on the strain/temperature observed in each section of the grating; thus, they enable a short-length distributed sensing, whereas it is possible to detect spatially resolved variations of temperature or strain with resolution on the order of a millimeter over the grating length. Based on this premise, CFBGs have found important applications in healthcare, mechanical engineering, and shock waves analysis, among others. This work reviews the present and emerging trends in CFBG sensors, focusing on all aspects of the sensing element and outlining the application case scenarios for which CFBG sensors have been demonstrated. Full article

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

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Other

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1 pages, 149 KiB

Open AccessErratum

Erratum: Zhao, Y.; Zhang, N.; Si, G.; Li, X. Study on the Optimal Groove Shape and Glue Material for Fiber Bragg Grating Measuring Bolts. Sensors 2018, 18, 1799

by Yiming Zhao, Nong Zhang, Guangyao Si and Xuehua Li

Sensors 2019, 19(7), 1723; https://doi.org/10.3390/s19071723 - 10 Apr 2019

Cited by 2 | Viewed by 2500

Abstract

The authors wish to correct the affiliation of co-author Guangyao Si, due to name changes of which he was unaware during his leave of absence [...] Full article

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

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