Smart architecture for stable multipoint fiber Bragg grating sensor system

Science.gov (United States)

Yeh, Chien-Hung; Tsai, Ning; Zhuang, Yuan-Hong; Huang, Tzu-Jung; Chow, Chi-Wai; Chen, Jing-Heng; Liu, Wen-Fung

2017-12-01

In this work, we propose and investigate an intelligent fiber Bragg grating (FBG)-based sensor system in which the proposed stabilized and wavelength-tunable single-longitudinal-mode erbium-doped fiber laser can improve the sensing accuracy of wavelength-division-multiplexing multiple FBG sensors in a longer fiber transmission distance. Moreover, we also demonstrate the proposed sensor architecture to enhance the FBG capacity for sensing strain and temperature, simultaneously.

Optical fiber sensors FBG to the structural health monitoring of bridges

International Nuclear Information System (INIS)

Navarro-Henriquez, Francisco

2014-01-01

Systems with optical fiber sensors FBG (Fiber Bragg Grating) are consolidated in the Structural Health Monitoring (SHM) of bridges, static and dynamic nondestructive testing with measurements of deformation, displacement, deflection, temperature and vibrations. A brief introduction to the technology is presented and the fundamentals of optical fiber sensors, their use and comparative advantages over its traditional counterpart. The practice of the FBG sensor application is described. The characteristics of these sensors and measurement graphics are presented. Some key aspects to consider for proper use in the field are mentioned. (author) [es

Fibre Bragg grating and no-core fibre sensors

CERN Document Server

Daud, Suzairi

2018-01-01

This book focuses on the development and set-up of fibre Bragg grating (FBG) and no-core fibre (NCF) sensors. It discusses the properties of the sensors and modelling of the resulting devices, which include electronic, optoelectronic, photovoltaic, and spintronic devices. In addition to providing detailed explanations of the properties of FBG and NCF sensors, it features a wealth of instructive illustrations and tables, helping to visualize the respective devices’ functions.

Multi-Functional Measurement Using a Single FBG Sensor

NARCIS (Netherlands)

Mizutani, Y.; Groves, R.M.

2011-01-01

This paper describes the measurement of average strain, strain distribution and vibration of a cantilever beam made of Carbon Fiber Reinforced Plastics (CFRP), using a single Fibre Bragg Grating (FBG) sensor mounted on the beam surface. Average strain is determined from the displacement of the peak

Fiber Bragg Grating vibration sensor with DFB laser diode

Science.gov (United States)

Siska, Petr; Brozovic, Martin; Cubik, Jakub; Kepak, Stanislav; Vitasek, Jan; Koudelka, Petr; Latal, Jan; Vasinek, Vladimir

2012-01-01

The Fiber Bragg Grating (FBG) sensors are nowadays used in many applications. Thanks to its quite big sensitivity to a surrounding environment, they can be used for sensing of temperature, strain, vibration or pressure. A fiber Bragg grating vibration sensor, which is interrogated by a distributed feedback laser diode (DFB) is demonstrated in this article. The system is based on the intensity modulation of the narrow spectral bandwidth of the DFB laser, when the reflection spectrum of the FBG sensor is shifted due to the strain that is applied on it in form of vibrations caused by acoustic wave pressure from loud speaker. The sensor's response in frequency domain and strain is measured; also the factor of sensor pre-strain impact on its sensitivity is discussed.

Structural behavior of concrete box bridge using embedded FBG sensors

Science.gov (United States)

Chung, Wonseok; Kang, Donghoon

2012-04-01

For the structural monitoring of railway bridges, electromagnetic interference (EMI) is a significant problem as modern railway lines are powered by high-voltage electric power feeding systems. Fiber optic sensing systems are free from EMI and have been successfully applied in civil engineering fields. This study presents the application of fiber Bragg grating (FBG)-based sensing systems to precast concrete box railway bridges. A 20 m long full-scale precast concrete box railway girder was fabricated and tested in order to identify its static performance. The experimental program involved the measurement of the nonlinear static behavior until failure. Multiplexed FBG strain sensors were embedded along the length of steel rebar and a strain-induced wavelength shift was measured in order to monitor internal strains. The measured values from the FBG-based sensors are compared with the results using electric signal-based sensors. The results show that the FBG sensing system is promising and can improve the efficiency of structural monitoring for modern railway bridges.

Development of a high resolution plantar pressure monitoring pad based on fiber Bragg grating (FBG) sensors.

Science.gov (United States)

Suresh, R; Bhalla, S; Hao, J; Singh, C

2015-01-01

High importance is given to plantar pressure monitoring in the field of biomedical engineering for the diagnosis of posture related ailments associated with diseases such as diabetes and gonarthrosis. This paper presents the proof-of-concept development of a new high resolution plantar pressure monitoring pad based on fiber Bragg grating (FBG) sensors. In the proposed configuration, the FBG sensors are embedded within layers of carbon composite material (CCM) in turn conforming to an arc shape. A total of four such arc shaped sensors are instrumented in the pad at the locations of the forefoot and the hind foot. As a test of the pad, static plantar pressure is monitored on normal subjects under various posture conditions. The pad is evaluated both as a standalone platform as well as a pad inserted inside a standard shoe. An average pressure sensitivity of 1.2 pm/kPa and a resolution of approximately 0.8 kPa is obtained in this special configuration. The pad is found to be suitable in both configurations- stand-alone pad as well as an insert inside a standard shoe. The proposed set up offers a cost-effective high resolution and accurate plantar pressure measurement system suitable for clinical deployment. The novelty of the developed pressure pad lies in its ability to be used both as platform type as well as inserted in-sole type sensor system.

Analysis and Optimization of Thermodiffusion of an FBG Sensor in the Gas Nitriding Process

Directory of Open Access Journals (Sweden)

Tso-Sheng Hsieh

2016-12-01

Full Text Available In this paper, we report the numerical calculations for a thermo-optical model and the temperature sensitivity of a fiber Bragg grating (FBG sensor. The thermally-induced behaviors of a FBG sensor in the gas nitriding process were analyzed for temperatures ranging from 100–650 °C. The FBG consisted of properly chosen photosensitive fiber materials with an optimized thermo-optic coefficient. The experimental and optimized thermo-optic coefficient results were consistent in terms of temperature sensitivity. In these experiments, the temperature sensitivity of the FBG was found to be 11.9 pm/°C.

Real time transverse-force sensor based on polarization properties of fiber Bragg grating and cross-sensitivity compensation

International Nuclear Information System (INIS)

Su, Yang; Zhu, Yong; Zhang, Baofu; Peng, Hui; Ye, Zhenxing

2013-01-01

We present a new method for real-time transverse force sensor based on the measurement of the polarization properties of a uniform fiber Bragg grating (FBG) written into standard single mode fiber. Unlike the usual spectral analysis of FBG sensors, we demonstrate here that the amplitude of the first Stokes parameters of a uniform FBG in transmission can be used to obtain transverse force value. The influences of incident angle of linear polarized light launched into FBG on sensor performance are analyzed. Experimental results measured by means of a tunable laser source and a polarimeter are presented. We also propose a kind of grating structure with triangular-shaped transmission spectrum to reduce the influences of cross-sensitivity. The compensation effect can satisfy the requirements of the practical application with optimized grating parameters. (paper)

Effects of Cyclic Thermal Load on the Signal Characteristics of FBG Sensors Packaged with Epoxy Adhesives

Energy Technology Data Exchange (ETDEWEB)

Kim, Heonyoung; Kang, Donghoon [Korea Railroad Research Institute, Uiwang (Korea, Republic of)

2017-04-15

Fiber optics sensors that have been mainly applied to aerospace areas are now finding applicability in other areas, such as transportation, including railways. Among the sensors, the fiber Bragg grating (FBG) sensors have led to a steep increase due to their properties of absolute measurement and multiplexing capability. Generally, the FBG sensors adhere to structures and sensing modules using adhesives such as an epoxy. However, the measurement errors that occurred when the FBG sensors were used in a long-term application, where they were exposed to environmental thermal load, required calibration. For this reason, the thermal curing of adhesives needs to be investigated to enhance the reliability of the FBG sensor system. This can be done at room temperature through cyclic thermal load tests using four types of specimens. From the test results, it is confirmed that residual compressive strain occurs to the FBG sensors due to an initial cyclic thermal load. In conclusion, signals of the FBG sensors need to be stabilized for applying them to a long-term SHM.

Self-sensing concrete-filled FRP tube using FBG strain sensor

Science.gov (United States)

Yan, Xin; Li, Hui

2007-01-01

Concrete-filled fiber-reinforced polymer (FRP) tube is a type of newly developed structural column. It behaves brittle failure at its peak strength, and so the health monitoring on the hoop strain of the FRP tube is essential for the life cycle safety of the structure. Herein, the optic fiber Bragg grating (FBG) strain sensor was chosen as the strain measuring gauge and embedded in the inter-ply of fibers in the middle height and the hoop direction of the FRP tube. The compressive behaviors of the concrete-filled FRP tubes were experimentally studied. The hoop strain of the FRP tube was recorded in real time using the embedded FBG strain sensor as well as the embedded or surface electric resistance strain gauges. Results indicated that the FBG strain sensor can faithfully record the hoop strain ofthe concrete-filled FRP tubes in compression as compared with the embedded or surface electric resistance strain gauges, and the strain recorded can reach more than 7000μɛ.

Review of the Strain Modulation Methods Used in Fiber Bragg Grating Sensors

Directory of Open Access Journals (Sweden)

Kuo Li

2016-01-01

Full Text Available Fiber Bragg grating (FBG is inherently sensitive to temperature and strain. By modulating FBG’s strain, various FBG sensors have been developed, such as sensors with enhanced or reduced temperature sensitivity, strain/displacement sensors, inclinometers, accelerometers, pressure meters, and magnetic field meters. This paper reviews the strain modulation methods used in these FBG sensors and categorizes them according to whether the strain of an FBG is changed evenly. Then, those even-strain-change methods are subcategorized into (1 attaching/embedding an FBG throughout to a base and (2 fixing the two ends of an FBG and (2.1 changing the distance between the two ends or (2.2 bending the FBG by applying a transverse force at the middle of the FBG. This review shows that the methods of “fixing the two ends” are prominent because of the advantages of large tunability and frequency modulation.

[Development of a simultaneous strain and temperature sensor with small-diameter FBG].

Science.gov (United States)

Liu, Rong-mei; Liang, Da-kai

2011-03-01

Manufacture of the small diameter FBG was designed. Cross sensitivity of temperature and strain at sensing point was solved. Based on coupled-mode theory, optical properties of the designed FBG were studied. The reflection and transmission spectra of the designed FBG in small diameter were studied A single mode optical fiber, whose cladding diameter is 80 microm, was manufactured to a fiber Bragg grating (phi80FBG). According to spectrum simulation, the grating length and period were chosen as the wavelength was 1528 nm. The connector of the small diameter FBG with demodulation was designed too. In applications, the FBG measures the total deformation including strain due to forces applied to the structures as well as thermal expansion. In order to overcome this inconvenience and to measure both parameters at the same time and location, a novel scheme for simultaneous strain and temperature sensor was presented. Since the uniform strength beam has same deformation at all points, a pair of phi80 FBG was attached on a uniform strength cantilever. One of the FBG was on the upper surface, with the other one on the below. Therefore, the strains at the monitoring points were equal in magnitude but of opposite sign. The strain and temperature in sensing point could be discriminated by matrix equation. The determination of the K is not null and thus matrix inversion is well conditioned, even the values for the K elements are close. Consequently, the cross sensitivity of the FBG with temperature and strain can be experimentally solved. Experiments were carried out to study the strain discriminability of small-diameter FBG sensors. The temperature and strain were calculated and the errors were, respectively, 5% and 6%.

Muscular condition monitoring system using fiber bragg grating sensors

International Nuclear Information System (INIS)

Kim, Heon Young; Lee, Jin Hyuk; Kim, Dae Hyun

2014-01-01

Fiber optic sensors (FOS) have advantages such as electromagnetic interference (EMI) immunity, corrosion resistance and multiplexing capability. For these reasons, they are widely used in various condition monitoring systems (CMS). This study investigated a muscular condition monitoring system using fiber optic sensors (FOS). Generally, sensors for monitoring the condition of the human body are based on electro-magnetic devices. However, such an electrical system has several weaknesses, including the potential for electro-magnetic interference and distortion. Fiber Bragg grating (FBG) sensors overcome these weaknesses, along with simplifying the devices and increasing user convenience. To measure the level of muscle contraction and relaxation, which indicates the muscle condition, a belt-shaped FBG sensor module that makes it possible to monitor the movement of muscles in the radial and circumferential directions was fabricated in this study. In addition, a uniaxial tensile test was carried out in order to evaluate the applicability of this FBG sensor module. Based on the experimental results, a relationship was observed between the tensile stress and Bragg wavelength of the FBG sensors, which revealed the possibility of fabricating a muscular condition monitoring system based on FBG sensors.

Muscular condition monitoring system using fiber bragg grating sensors

Energy Technology Data Exchange (ETDEWEB)

Kim, Heon Young; Lee, Jin Hyuk; Kim, Dae Hyun [Seoul National University of Technology, Seoul (Korea, Republic of)

2014-10-15

Fiber optic sensors (FOS) have advantages such as electromagnetic interference (EMI) immunity, corrosion resistance and multiplexing capability. For these reasons, they are widely used in various condition monitoring systems (CMS). This study investigated a muscular condition monitoring system using fiber optic sensors (FOS). Generally, sensors for monitoring the condition of the human body are based on electro-magnetic devices. However, such an electrical system has several weaknesses, including the potential for electro-magnetic interference and distortion. Fiber Bragg grating (FBG) sensors overcome these weaknesses, along with simplifying the devices and increasing user convenience. To measure the level of muscle contraction and relaxation, which indicates the muscle condition, a belt-shaped FBG sensor module that makes it possible to monitor the movement of muscles in the radial and circumferential directions was fabricated in this study. In addition, a uniaxial tensile test was carried out in order to evaluate the applicability of this FBG sensor module. Based on the experimental results, a relationship was observed between the tensile stress and Bragg wavelength of the FBG sensors, which revealed the possibility of fabricating a muscular condition monitoring system based on FBG sensors.

Transducer-based fiber Bragg grating high-temperature sensor with enhanced range and stability

Science.gov (United States)

Mamidi, Venkata Reddy; Kamineni, Srimannarayana; Ravinuthala, Lakshmi Narayana Sai Prasad; Tumu, Venkatappa Rao

2017-09-01

Fiber Bragg grating (FBG)-based high-temperature sensor with enhanced-temperature range and stability has been developed and tested. The sensor consists of an FBG and a mechanical transducer, which furnishes a linear temperature-dependent tensile strain on FBG by means of differential linear thermal expansion of two different ceramic materials. The designed sensor is tested over a range: 20°C to 1160°C and is expected to measure up to 1500°C.

Fiber Bragg grating sensors for real-time monitoring of evacuation process

Science.gov (United States)

Guru Prasad, A. S.; Hegde, Gopalkrishna M.; Asokan, S.

2010-03-01

Fiber bragg grating (FBG) sensors have been widely used for number of sensing applications like temperature, pressure, acousto-ultrasonic, static and dynamic strain, refractive index change measurements and so on. Present work demonstrates the use of FBG sensors in in-situ measurement of vacuum process with simultaneous leak detection capability. Experiments were conducted in a bell jar vacuum chamber facilitated with conventional Pirani gauge for vacuum measurement. Three different experiments have been conducted to validate the performance of FBG sensor in monitoring vacuum creating process and air bleeding. The preliminary results of FBG sensors in vacuum monitoring have been compared with that of commercial Pirani gauge sensor. This novel technique offers a simple alternative to conventional method for real time monitoring of evacuation process. Proposed FBG based vacuum sensor has potential applications in vacuum systems involving hazardous environment such as chemical and gas plants, automobile industries, aeronautical establishments and leak monitoring in process industries, where the electrical or MEMS based sensors are prone to explosion and corrosion.

Mathematical model for a novel cryogenic flow sensor using fibre Bragg gratings

OpenAIRE

Thekkethil, S.R.; Reby Roy, K.E.; Thomas, R.J.; Neumann, H.; Ramalingam, R.

2016-01-01

In this work, a mathematical model is presented for a newly developed cryogenic flow meter which is based on fibre Bragg grating (FBG) principle. The principle of operation is to use the viscous drag force induced by a flowing fluid on an optical fibre placed transverse to the flow. An optical fibre will have a 5 mm long grating element inscribed in it and will be placed so that the sensor is at the centre of the pipe. The fibre will act as the bluff body, while the FBG sensor will pick up th...

Hybrid MEFPI/FBG sensor for simultaneous measurement of strain and magnetic field

Science.gov (United States)

Chen, Mao-qing; Zhao, Yong; Lv, Ri-qing; Xia, Feng

2017-12-01

A hybrid fiber-optic sensor consisting of a micro extrinsic Fabry-Perot Interferometer (MEFPI) and an etched fiber Bragg grating (FBG) is proposed, which can measure strain and magnetic field simultaneously. The etched FBG is sealed in a capillary with ferrofluids to detect the surrounding magnetic field. FBG with small diameter will be more sensitive to magnetic field is confirmed by simulation results. The MEFPI sensor that is prepared through welding a short section of hollow-core fiber (HCF) with single-mode fiber (SMF) is effective for strain detection. The experiment shows that strain and magnetic field can be successfully simultaneously detected based on hybrid MEFPI/FBG sensor. The sensitivities of the strain and magnetic field intensity are measured to be up to 1.41 pm/με and 5.11 pm/mT respectively. There is a negligible effect on each other, hence simultaneously measuring strain and magnetic field is feasible. It is anticipated that such easy preparation, compact and low-cost fiber-optic sensors for simultaneous measurement of strain and magnetic field could find important applications in practice.

Fiber Bragg grating sensor-based communication assistance device

Science.gov (United States)

Padma, Srivani; Umesh, Sharath; Pant, Shweta; Srinivas, Talabattula; Asokan, Sundarrajan

2016-08-01

Improvements in emergency medicine in the form of efficient life supporting systems and intensive care have increased the survival rate in critically injured patients; however, in some cases, severe brain and spinal cord injuries can result in a locked-in syndrome or other forms of paralysis, and communication with these patients may become restricted or impossible. The present study proposes a noninvasive, real-time communication assistive methodology for those with restricted communication ability, employing a fiber Bragg grating (FBG) sensor. The communication assistive methodology comprises a breath pattern analyzer using an FBG sensor, which acquires the exhalation force that is converted into strain variations on a cantilever. The FBG breath pattern analyzer along with specific breath patterns, which are programmed to give specific audio output commands, constitutes the proposed fiber Bragg grating sensor-based communication assistive device. The basic communication can be carried out by instructing the patients with restricted communication ability to perform the specific breath patterns. The present approach is intended to be an alternative to the common approach of brain-computer interface in which an instrument is utilized for learning of brain responses.

Fiber Bragg grating assisted surface plasmon resonance sensor with graphene oxide sensing layer

Science.gov (United States)

Arasu, P. T.; Noor, A. S. M.; Shabaneh, A. A.; Yaacob, M. H.; Lim, H. N.; Mahdi, M. A.

2016-12-01

A single mode fiber Bragg grating (FBG) is used to generate Surface Plasmon Resonance (SPR). The uniform gratings of the FBG are used to scatter light from the fiber optic core into the cladding thus enabling the interaction between the light and a thin gold film in order to generate SPR. Applying this technique, the cladding around the FBG is left intact, making this sensor very robust and easy to handle. A thin film of graphene oxide (GO) is deposited over a 45 nm gold film to enhance the sensitivity of the SPR sensor. The gold coated sensor demonstrated high sensitivity of approximately 200 nm/RIU when tested with different concentrations of ethanol in an aqueous medium. A 2.5 times improvement in sensitivity is observed with the GO enhancement compared to the gold coated sensor.

Fiber optic liquid-level sensor using a long fiber Bragg grating

Science.gov (United States)

Ricchiuti, Amelia L.; Barrera, David; Nonaka, Koji; Sales, Salvador

2013-05-01

A technique for liquid-level sensors based on a long fiber Bragg grating (FBG) is presented and experimentally demonstrated. The measurement system is based on the measurement of the central frequency distribution of the FBG based on time-frequency domain analysis. A short optical pulse is injected into a 10-cm long FBG mounted in a container. The back-reflected pulse is scanned by means of an oscilloscope. When part of the grating is immersed in a liquid having temperature higher than the surrounding ambient, the structure of the uniform grating is distorted and its time-frequency response changes. A spatial resolution of 2 mm, given by the input pulse duration, and a 10-cm long measurement range are achieved. Liquid-temperature sensing has also been implemented by scanning the spectral response of the FBG by means of a CW laser and an OSA.

Enhanced FBG sensor-based system performance assessment for monitoring strain along a prestressed CFRP rod in structural monitoring

DEFF Research Database (Denmark)

Kerrouche, A.; Boyle, W.J.O.; Sun, T.

2009-01-01

of the existing FBG-based system and the evaluation of the software developed to be compatible with a resolution reaching as high as +/- 0.15 mu epsilon is presented. The system has been tested under particular conditions where a prestressed CFRP (carbon fiber reinforced polymer) rod to which a FBG sensor......Fiber Bragg grating (FBG) sensor-based systems have been widely used for many engineering applications including most recently a number of applications in structural health monitoring. It is well known that strain and temperature both affect the FBG spectrum which in the interrogation system...

Finite element modelling of fibre Bragg grating strain sensors and experimental validation

Science.gov (United States)

Malik, Shoaib A.; Mahendran, Ramani S.; Harris, Dee; Paget, Mark; Pandita, Surya D.; Machavaram, Venkata R.; Collins, David; Burns, Jonathan M.; Wang, Liwei; Fernando, Gerard F.

2009-03-01

Fibre Bragg grating (FBG) sensors continue to be used extensively for monitoring strain and temperature in and on engineering materials and structures. Previous researchers have also developed analytical models to predict the loadtransfer characteristics of FBG sensors as a function of applied strain. The general properties of the coating or adhesive that is used to surface-bond the FBG sensor to the substrate has also been modelled using finite element analysis. In this current paper, a technique was developed to surface-mount FBG sensors with a known volume and thickness of adhesive. The substrates used were aluminium dog-bone tensile test specimens. The FBG sensors were tensile tested in a series of ramp-hold sequences until failure. The reflected FBG spectra were recorded using a commercial instrument. Finite element analysis was performed to model the response of the surface-mounted FBG sensors. In the first instance, the effect of the mechanical properties of the adhesive and substrate were modelled. This was followed by modelling the volume of adhesive used to bond the FBG sensor to the substrate. Finally, the predicted values obtained via finite element modelling were correlated to the experimental results. In addition to the FBG sensors, the tensile test specimens were instrumented with surface-mounted electrical resistance strain gauges.

Self-sensing concrete-filled FRP tubes using FBG strain sensors

Science.gov (United States)

Yan, Xin; Li, Hui

2007-07-01

Concrete-filled fiber-reinforced polymer (FRP) tube is a type of newly developed structural column. It behaves brittle failure at its peak strength, and so the health monitoring on the hoop strain of the FRP tube is essential for the life cycle safety of the structure. Herein, three types of FRP tubes including 5-ply tube, 2-ply tube with local reinforcement and FRP-steel composite tube were embedded with the optic fiber Bragg grating (FBG) strain sensors in the inter-ply of FRP or the interface between FRP and steel in the middle height and the hoop direction. The compressive behaviors of the concrete-filled FRP tubes were experimentally studied. The hoop strains of the FRP tubes were recorded in real time using the embedded FBG strain sensors as well as the embedded or surface electric resistance strain gauges. Results indicated that the FBG strain sensors can faithfully record the hoop strains of the FRP tubes in compression as compared with the embedded or surface electric resistance strain gauges, and the strains recorded can reach more than μɛ.

In Vivo Pattern Classification of Ingestive Behavior in Ruminants Using FBG Sensors and Machine Learning

OpenAIRE

Pegorini, Vinicius; Karam, Leandro Zen; Pitta, Christiano Santos Rocha; Cardoso, Rafael; da Silva, Jean Carlos Cardozo; Kalinowski, Hypolito Jos?; Ribeiro, Richardson; Bertotti, F?bio Luiz; Assmann, Tangriani Simioni

2015-01-01

Pattern classification of ingestive behavior in grazing animals has extreme importance in studies related to animal nutrition, growth and health. In this paper, a system to classify chewing patterns of ruminants in in vivo experiments is developed. The proposal is based on data collected by optical fiber Bragg grating sensors (FBG) that are processed by machine learning techniques. The FBG sensors measure the biomechanical strain during jaw movements, and a decision tree is responsible for th...

Highly sensitive fiber grating chemical sensors: An effective alternative to atomic absorption spectroscopy

Science.gov (United States)

Laxmeshwar, Lata. S.; Jadhav, Mangesh S.; Akki, Jyoti. F.; Raikar, Prasad; Kumar, Jitendra; prakash, Om; Raikar, U. S.

2017-06-01

Accuracy in quantitative determination of trace elements like Zinc, present in drinking water in ppm level, is a big challenge and optical fiber gratings as chemical sensors may provide a promising solution to overcome the same. This paper presents design of two simple chemical sensors based on the principle of shift in characteristic wavelength of gratings with change in their effective refractive index, to measure the concentration of Zinc in drinking water using etched short period grating (FBG) and Long period grating (LPG) respectively. Three samples of drinking water from different places have been examined for presence of Zinc. Further, the results obtained by our sensors have also been verified with the results obtained by a standard method, Atomic absorption spectroscopy (AAS). The whole experiment has been performed by fixing the fibers in a horizontal position with the sensor regions at the center of the fibers, making it less prone to disturbance and breaking. The sensitivity of LPG sensor is about 205 times that of the FBG sensor. A few advantages of Fiber grating sensors, besides their regular features, over AAS have also been discussed, that make our sensors potential alternatives for existing techniques in determination of trace elements in drinking water.

Structural Health Monitoring of Bridges with Fiber Bragg Grating Sensors

Directory of Open Access Journals (Sweden)

Francisco Navarro-Henríquez

2014-11-01

Systems with fiber optic sensors FBG (Fiber Bragg Grating are consolidated in the Structural Health Monitoring (SMH of bridges, Nondestructive Testing (NDT static and dynamic measurements of deformation, displacement, deflection, temperature and vibration. This article provides a brief introduction to the technology and the fundamentals of fiber optic sensors, also present comparative advantages over its traditional counterpart is presented. Their characteristics are described and measurement graphics are presented as an application example of the FBG sensors. Finally, some key aspects to consider for proper use in the field are mentioned.

Peak wavelength interrogation of fiber Bragg grating sensors during impact events

International Nuclear Information System (INIS)

Park, Chun; Peters, Kara; Zikry, Mohammed; Haber, Todd; Schultz, Stephen; Selfridge, Richard

2010-01-01

In this paper, we embed fiber Bragg grating (FBG) sensors in graphite fiber–epoxy woven composite laminates to detect evolving damage modes. The peak wavelengths of the FBG sensors are interrogated at 625 and 295 kHz, while the laminates are subjected to 11.0 J low-velocity impact events. It is demonstrated that 295 kHz interrogation is sufficient for accurately collecting the dynamic response of the sensors. The FBG sensors embedded at the laminate midplanes successfully reconstructed the global laminate response to impact. The maximum and full width at half-maximum (FWHM) for the relative strain histories demonstrated the same trends as the maximum and FWHM of the contact force histories measured from the impactor. More noise was present in the strain histories obtained from the FBG sensors than the contact force histories, as the embedded FBGs were sensitive to local perturbations in the stress state. The FBG sensors embedded below the midplane of the laminate were closer to the damage regions and measured complex strain histories. In one case, this strain history revealed the presence of delamination

Performance assessment of indigenously developed FBG strain ...

Indian Academy of Sciences (India)

and new structures are mainly limited to the application of electric and ... can also be measured by designing appropriate coatings or transducers. ... consuming process. .... installed on the specimen by means of spot welding. ... experiment an FBG sensor with three gratings of 30 mm (FBG1, FBG2 and FBG3), interspac-.

Temperature Compensation Fiber Bragg Grating Pressure Sensor Based on Plane Diaphragm

Science.gov (United States)

Liang, Minfu; Fang, Xinqiu; Ning, Yaosheng

2018-03-01

Pressure sensors are the essential equipments in the field of pressure measurement. In this work, we propose a temperature compensation fiber Bragg grating (FBG) pressure sensor based on the plane diaphragm. The plane diaphragm and pressure sensitivity FBG (PS FBG) are used as the pressure sensitive components, and the temperature compensation FBG (TC FBG) is used to improve the temperature cross-sensitivity. Mechanical deformation model and deformation characteristics simulation analysis of the diaphragm are presented. The measurement principle and theoretical analysis of the mathematical relationship between the FBG central wavelength shift and pressure of the sensor are introduced. The sensitivity and measure range can be adjusted by utilizing the different materials and sizes of the diaphragm to accommodate different measure environments. The performance experiments are carried out, and the results indicate that the pressure sensitivity of the sensor is 35.7 pm/MPa in a range from 0 MPa to 50 MPa and has good linearity with a linear fitting correlation coefficient of 99.95%. In addition, the sensor has the advantages of low frequency chirp and high stability, which can be used to measure pressure in mining engineering, civil engineering, or other complex environment.

Temperature Compensation Fiber Bragg Grating Pressure Sensor Based on Plane Diaphragm

Science.gov (United States)

Liang, Minfu; Fang, Xinqiu; Ning, Yaosheng

2018-06-01

Pressure sensors are the essential equipments in the field of pressure measurement. In this work, we propose a temperature compensation fiber Bragg grating (FBG) pressure sensor based on the plane diaphragm. The plane diaphragm and pressure sensitivity FBG (PS FBG) are used as the pressure sensitive components, and the temperature compensation FBG (TC FBG) is used to improve the temperature cross-sensitivity. Mechanical deformation model and deformation characteristics simulation analysis of the diaphragm are presented. The measurement principle and theoretical analysis of the mathematical relationship between the FBG central wavelength shift and pressure of the sensor are introduced. The sensitivity and measure range can be adjusted by utilizing the different materials and sizes of the diaphragm to accommodate different measure environments. The performance experiments are carried out, and the results indicate that the pressure sensitivity of the sensor is 35.7 pm/MPa in a range from 0 MPa to 50 MPa and has good linearity with a linear fitting correlation coefficient of 99.95%. In addition, the sensor has the advantages of low frequency chirp and high stability, which can be used to measure pressure in mining engineering, civil engineering, or other complex environment.

Sensitivity improvement of a fibre Bragg grating pH sensor with elastomeric coating

Science.gov (United States)

Yulianti, Ian; Supa'at, A. S. M.; Idrus, Sevia M.; Kurdi, Ojo; Anwar, M. R. S.

2012-01-01

A new optical pH sensor based on fibre Bragg grating (FBG) is demonstrated. The sensor consists of a FBG coated with pH sensitive hydrogel. The sensing was performed through the detection of wavelength shifts resulting from the induced strain on the FBG due to mechanical expansion of the hydrogel. An elastomeric coating was applied before the hydrogel coating to improve the sensitivity. The sensor performance was investigated by simulating the hydrogel swelling and the strain induced on the FBG. The swelling of hydrogel due to pH change was modelled using a free-energy function and was solved using the finite element method. With silicone rubber as the elastomer material, the results show that the sensitivity was improved by up to 66% compared to that of the FBG pH sensor without elastomeric coating.

Sensitivity improvement of a fibre Bragg grating pH sensor with elastomeric coating

International Nuclear Information System (INIS)

Yulianti, Ian; Supa'at, A S M; Idrus, Sevia M; Anwar, M R S; Kurdi, Ojo

2012-01-01

A new optical pH sensor based on fibre Bragg grating (FBG) is demonstrated. The sensor consists of a FBG coated with pH sensitive hydrogel. The sensing was performed through the detection of wavelength shifts resulting from the induced strain on the FBG due to mechanical expansion of the hydrogel. An elastomeric coating was applied before the hydrogel coating to improve the sensitivity. The sensor performance was investigated by simulating the hydrogel swelling and the strain induced on the FBG. The swelling of hydrogel due to pH change was modelled using a free-energy function and was solved using the finite element method. With silicone rubber as the elastomer material, the results show that the sensitivity was improved by up to 66% compared to that of the FBG pH sensor without elastomeric coating

Prototype fiber Bragg Grattings (FBG) sensor based on intensity modulation of the laser diode low frequency vibrations measurement

Science.gov (United States)

Setiono, Andi; Ula, Rini Khamimatul; Hanto, Dwi; Widiyatmoko, Bambang; Purnamaningsih, Retno Wigajatri

2016-02-01

In general, Fiber Bragg Grating (FBG) sensor works based on observation of spectral response characteristic to detect the desired parameter. In this research, we studied intensity response characteristic of FBG to detect the dynamic strain. Experiment result show that the reflected intensity had linier relationships with dynamic strain. Based on these characteristics, we developed the FBG sensor to detect low frequency vibration. This sensor is designed by attaching the FBG on the bronze cantilever with dimensions of 85×3×0.5 mm. Measurement results showed that the sensor was able to detect vibrations in the frequency range of 7-10 Hz at temperature range of 25-45 ˚C. The measured frequency range is still within the frequency range of digging activity, therefore this vibration sensor can be applied for oil pipelines vandalisation detection system.

Continuous liquid level monitoring sensor system using fiber Bragg grating

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Sengupta, Dipankar; Kishore, Putha

2014-01-01

The design and packaging of simple, small, and low cost sensor heads, used for continuous liquid level measurement using uniformly thinned (etched) optical fiber Bragg grating (FBG) are proposed. The sensor system consists of only an FBG and a simple detection system. The sensitivity of sensor is found to be 23 pm/cm of water column pressure. A linear optical fiber edge filter is designed and developed for the conversion of Bragg wavelength shift to its equivalent intensity. The result shows that relative power measured by a photo detector is linearly proportional to the liquid level. The obtained sensitivity of the sensor is nearly -15 mV/cm.

Fibre Bragg grating encapted with no-core fibre sensors for SRI and temperature monitoring

Directory of Open Access Journals (Sweden)

S. Daud

2018-06-01

Full Text Available In this work, a Fibre Bragg grating (FBG encapted with no-core fibre (NCF as surrounding refractive index (SRI and temperature sensors are practically demonstrated. A FBG with 1550 nm wavelength was attached with 5 cm length of no-core fibre (NCF is used as SRI and temperature sensing probe. The change of temperature and SRI induced the wavelength shift in FBG. The wavelength shift in FBG reacts directly proportional to the temperature with a sensitivity of while the sensitivity of NCF was measured as 13.13 pm °C−1. Keywords: FBG, No-core fibre (NCF, Temperature, Sensor

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

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

2016-10-04

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.

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

Directory of Open Access Journals (Sweden)

Ying-Ting Luo

2016-10-01

Full Text Available 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.

Hydrogel-coated fiber Bragg grating sensor for pH monitoring

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Pabbisetti, Vayu Nandana Kishore; Madhuvarasu, Sai Shankar

2016-06-01

We present a fiber-optic wavelength-modulated sensor for pH applications. Fiber Bragg grating (FBG) is functionalized with a stimulus-responsive hydrogel that induces a strain on FBG due to mechanical expansion of the gel in response to ambient pH changes. The gel is synthesized from the blends of poly (vinyl alcohol)/poly (acrylic acid). The induced strain results in a shift of FBG reflected peak that is monitored by an interrogator. The sensor system shows good linearity in the acidic pH range of 3 to 7 with a sensitivity of 12.16 pm/pH. In addition, it shows good repeatability and oscillator behavior, which proves it to be fit for pH sensing applications.

Crack growth monitoring in composite materials using embedded optical Fiber Bragg Grating sensor

DEFF Research Database (Denmark)

Pereira, Gilmar Ferreira; Mikkelsen, Lars Pilgaard; McGugan, Malcolm

2015-01-01

In this paper a novel method to assess a crack growing/damage event in fiber reinforced plastic, or adhesive using Fiber Bragg Grating (FBG) sensors embedded in a host material is shown. Different features of the crack mechanism that induce a change in the FBG response were identified. Double...

Fiber Bragg grating sensors for structural and railway applications

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Tam, H. Y.; Liu, S. Y.; Guan, B. O.; Chung, W. H.; Chan, T. H.; Cheng, L. K.

2005-02-01

Historically, due to the high cost of optical devices, fiber-optics sensor systems were only employed in niche areas where conventional electrical sensors are not suitable. This scenario changed dramatically in the last few years following the explosion of the Internet which caused the rapid expansion of the optical fiber telecommunication industry and substantially driven down the cost of optical components. In recent years, fiber-optic sensors and particularly fiber Bragg grating (FBG) sensors have attracted a lot of interests and are being used in numerous applications. We have conducted several field trials of FBG sensors for railway applications and structural monitoring. About 30 FBG sensors were installed on the rail tracks of Kowloon-Canton Railway Corp. for train identification and speed measurements and the results obtained show that FBG sensors exhibit very good performance and could play a major role in the realization of "Smart Railway". FBG sensors were also installed on Hong Kong's landmark TsingMa Bridge, which is the world longest suspension bridge (2.2 km) that carries both trains and regular road traffic. The trials were carried out with a high-speed (up to 20 kHz) interrogation system based on CCD and also with a interrogation unit that based on scanning optical filter (up to 70 Hz). Forty FBGs sensors were divided into 3 arrays and installed on different parts of the bridge (suspension cable, rocker bearing and truss girders). The objectives of the field trial on the TsingMa Bridge are to monitor the strain of different parts of the bridge under railway load and highway load, and to compare the FBG sensors' performance with conventional resistive strain gauges already installed on the bridge. The measured results show that excellent agreement was obtained between the 2 types of sensors.

High sensitivity optical fiber liquid level sensor based on a compact MMF-HCF-FBG structure

Science.gov (United States)

Zhang, Yunshan; Zhang, Weigang; Chen, Lei; Zhang, Yanxin; Wang, Song; Yan, Tieyi

2018-05-01

An ultra-high sensitivity fiber liquid level sensor based on wavelength demodulation is proposed and demonstrated. The sensor is composed of a segment of multimode fiber and a large aperture hollow-core fiber assisted by a fiber Bragg grating (FBG). Interference occurs due to core mismatching and different modes with different effective refractive indices. The experimental results show that the liquid level sensitivity of the sensor is 1.145 nm mm‑1, and the linearity is up to 0.996. The dynamic temperature compensation of the sensor can be achieved by cascading an FBG. Considering the high sensitivity and compact structure of the sensor, it can be used for real-time intelligent monitoring of tiny changes in liquid level.

Feasibility study of the optical fiber Bragg grating sensors in radiation environment

Energy Technology Data Exchange (ETDEWEB)

Fujita, Kaoru; Kimura, Atsushi; Nakazawa, Masaharu [Tokyo Univ., Dept. of Quantum Engineering and Systems Science, Tokyo (Japan); Takahashi, Hiroyuki [Tokyo Univ., Center of Engineering, Research into Artifacts, Tokyo (Japan); Ariyoshi, Masahiko [Japan Nuclear Cycle Development Inst., Oarai, Ibaraki (Japan)

2002-09-01

Applicability of an optical fiber Bragg grating (FBG)-based vibration sensor to radiation environment was investigated for monitoring nuclear plants. The FBG sensor is a kind of optical fiber sensors which is developing rapidly in recent years. FBGs reflect light which fulfill the Bragg condition {lambda} = 2 n L, where {lambda} is the wave length of reflecting light, n and L are the effective refractive index and length of the modulation period in grating part, respectively. The strain on FBGs influences on n and L and causes shift of {lambda}. The sensitivity to strain of FBG were investigated. The FBGs was irradiated with gamma-rays to investigate the irradiation effects on the FBGs. The Bragg wavelength of FBGs is not affected by gamma-rays up to 1.0 MGy of total absorbed dose. In vibration measurement system, two FBGs were attached to a thin iron plate. Each FBG was set up both side of the thin plate and spliced in series. An audio speaker was used as a vibration source. FBGs were irradiated at the dose rate of 50Gy/h and the vibration were observed in situ. Input signals from oscillator, the output from FBG sensors and the power spectra of the two signals were measured. The output signal was very noisy, however, the peak of the frequency is corresponding. The noise seemed to be arisen during the vibration traveled between the speaker and the plate and considered to be not essential. As a result, it is shown that a change of frequency at the vibration source could be followed by FBG-based sensors. To reduce the noise, the method for conducting the vibration to FBGs should be improved. (M. Suetake)

Feasibility study of the optical fiber Bragg grating sensors in radiation environment

International Nuclear Information System (INIS)

Fujita, Kaoru; Kimura, Atsushi; Nakazawa, Masaharu; Takahashi, Hiroyuki; Ariyoshi, Masahiko

2002-01-01

Applicability of an optical fiber Bragg grating (FBG)-based vibration sensor to radiation environment was investigated for monitoring nuclear plants. The FBG sensor is a kind of optical fiber sensors which is developing rapidly in recent years. FBGs reflect light which fulfill the Bragg condition λ = 2 n L, where λ is the wave length of reflecting light, n and L are the effective refractive index and length of the modulation period in grating part, respectively. The strain on FBGs influences on n and L and causes shift of λ. The sensitivity to strain of FBG were investigated. The FBGs was irradiated with gamma-rays to investigate the irradiation effects on the FBGs. The Bragg wavelength of FBGs is not affected by gamma-rays up to 1.0 MGy of total absorbed dose. In vibration measurement system, two FBGs were attached to a thin iron plate. Each FBG was set up both side of the thin plate and spliced in series. An audio speaker was used as a vibration source. FBGs were irradiated at the dose rate of 50Gy/h and the vibration were observed in situ. Input signals from oscillator, the output from FBG sensors and the power spectra of the two signals were measured. The output signal was very noisy, however, the peak of the frequency is corresponding. The noise seemed to be arisen during the vibration traveled between the speaker and the plate and considered to be not essential. As a result, it is shown that a change of frequency at the vibration source could be followed by FBG-based sensors. To reduce the noise, the method for conducting the vibration to FBGs should be improved. (M. Suetake)

Wavelength detection in FBG sensor networks using least squares support vector regression

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Chen, Jing; Jiang, Hao; Liu, Tundong; Fu, Xiaoli

2014-04-01

A wavelength detection method for a wavelength division multiplexing (WDM) fiber Bragg grating (FBG) sensor network is proposed based on least squares support vector regression (LS-SVR). As a kind of promising machine learning technique, LS-SVR is employed to approximate the inverse function of the reflection spectrum. The LS-SVR detection model is established from the training samples, and then the Bragg wavelength of each FBG can be directly identified by inputting the measured spectrum into the well-trained model. We also discuss the impact of the sample size and the preprocess of the input spectrum on the performance of the training effectiveness. The results demonstrate that our approach is effective in improving the accuracy for sensor networks with a large number of FBGs.

Novel glucose fiber sensor combining ThFBG with GOD

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Li, Mengmeng; Zhou, Ciming; Fan, Dian; Ou, Yiwen

2016-10-01

We propose a novel glucose fiber optic sensor combining a thinned cladding fiber Bragg grating (ThFBG) with glucose oxidase (GOD). By immobilizing GOD on the surface of a ThFBG, the fabricated sensor can obtain a high specificity to glucose. Because of the evanescent field, the sensor is very sensitive to the ambient refractive index change arising from the catalytic reaction between glucose and GOD. A four-level fiber model was simulated and verified the precision of the sensing principle. Two methods, glutaraldehyde crosslinking method (GCM) and 3-aminopropyl triethoxysilane covalent coupling method (ATCCM), were experimentally utilized to immobilize GOD. And sensor fabricated with the method ATCCM shows a measurement range of 0-0.82 mg/mL which is better than the sensor fabricated with the method GCM with measurement range of 0-0.67 mg/mL under the same condition. By using ATCCM to immobilize GOD with different concentrations, three sensors were fabricated and used for glucose measurement by monitoring the Bragg wavelength (λb) shifts, the results indicate a good linear relationship between wavelength shift and glucose concentration within a specific range, and the measurement range increases as GOD concentration increases. The highest sensitivity of sensor reaches up to 0.0549 nm/(mg.mL-1). The proposed sensor has distinct advantages in sensing structure, cost and specificity.

Early-age monitoring of cement structures using FBG sensors

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Wang, Chuan; Zhou, Zhi; Zhang, Zhichun; Ou, Jinping

2006-03-01

With more and more broad applications of the cement-based structures such as neat cement paste, cement mortar and concrete in civil engineering, people hope to find out what their performances should like. The in-service performances of cement-based structures are highly affected by their hardening process during the early-age. But it is still a big problem for traditional sensors to be used to monitor the early curing of cement-based structures due to such disadvantages as difficulties to install sensors inside the concrete, limited measuring points, poor durability and interference of electromagnetic wave and so on. In this paper, according to the sensing properties of the Fiber Bragg Grating sensors and self-characters of the cement-based structures, we have successfully finished measuring and monitoring the early-age inner-strain and temperature changes of the neat cement paste, concrete with and without restrictions, mass concrete structures and negative concrete, respectively. Three types of FBG-based sensors have been developed to monitor the cement-based structures. Besides, the installation techniques and the embedding requirements of FBG sensors in cement-based structures are also discussed. Moreover, such kind of technique has been used in practical structure, 3rd Nanjing Yangtze Bridge, and the results show that FBG sensors are well proper for measuring and monitoring the temperature and strain changes including self-shrinkage, dry shrinkage, plastic shrinkage, temperature expansion, frost heaving and so on inside different cement-based structures. This technique provides us a new useful measuring method on early curing monitoring of cement-based structures and greater understanding of details of their hardening process.

A minimally invasive in-fiber Bragg grating sensor for intervertebral disc pressure measurements

International Nuclear Information System (INIS)

Dennison, Christopher R; Wild, Peter M; Wilson, David R; Cripton, Peter A

2008-01-01

We present an in-fiber Bragg grating (FBG) based intervertebral disc (IVD) pressure sensor that has pressure sensitivity seven times greater than that of a bare fiber, and a major diameter and sensing area of only 400 µm and 0.03 mm 2 , respectively. This is the only optical, the smallest and the most mechanically compliant disc pressure sensor reported in the literature. This is also an improvement over other FBG pressure sensors that achieve increased sensitivity through mechanical amplification schemes, usually resulting in major diameters and sensing lengths of many millimeters. Sensor sensitivity is predicted using numerical models, and the predicted sensitivity is verified through experimental calibrations. The sensor is validated by conducting IVD pressure measurements in porcine discs and comparing the FBG measurements to those obtained using the current standard sensor for IVD pressure. The predicted sensitivity of the FBG sensor matched with that measured experimentally. IVD pressure measurements showed excellent repeatability and agreement with those obtained from the standard sensor. Unlike the current larger sensors, the FBG sensor could be used in discs with small disc height (i.e. cervical or degenerated discs). Therefore, there is potential to conduct new measurements that could lead to new understanding of the biomechanics

Microfiber Bragg grating hydrogen sensor base on co-sputtered Pd/Ni composite film

Science.gov (United States)

Wang, Gaopeng; Yang, Minghong; Dai, Jixiang; Cheng, Cheng; Yuan, Yinqian

2015-07-01

A novel hydrogen sensor based on Pd/Ni co-sputtered coating on micro fiber Bragg grating (MFBG) is proposed and experimentally demonstrated. The microfiber is stretched uniformly and the Bragg grating is directly inscribed on the microfiber without hydrogen loading using 193 nm ArF excimer laser and a phase mask. Palladium and nickel coatings are co-sputtered on the micro fiber Bragg grating for hydrogen sensing. The MFBG hydrogen sensors are characterized concerning their response to the hydrogen, ambient temperature and ambient refractive index, respectively. The performance of the proposed MFBG hydrogen sensor is obviously enhanced, especially when compared to standard FBG hydrogen sensors.

Fiber-MZI-based FBG sensor interrogation: comparative study with a CCD spectrometer.

Science.gov (United States)

Das, Bhargab; Chandra, Vikash

2016-10-10

We present an experimental comparative study of the two most commonly used fiber Bragg grating (FBG) sensor interrogation techniques: a charge-coupled device (CCD) spectrometer and a fiber Mach-Zehnder interferometer (F-MZI). Although the interferometric interrogation technique is historically known to offer the highest sensitivity measurements, very little information exists regarding how it compares with the current commercially available spectral-characteristics-based interrogation systems. It is experimentally established here that the performance of a modern-day CCD spectrometer interrogator is very close to a F-MZI interrogator with the capability of measuring Bragg wavelength shifts with sub-picometer-level accuracy. The results presented in this research study can further be used as a guideline for choosing between the two FBG sensor interrogator types for small-amplitude dynamic perturbation measurements down to nano-level strain.

Multipoint sensor based on fiber Bragg gratings

International Nuclear Information System (INIS)

Mendez-Zepeda, O; Munoz-Aguirre, S; Beltran-Perez, G; Castillo-Mixcoatl, J

2011-01-01

In some control and industrial measurement systems of physical variables (pressure, temperature, flow, etc) it is necessary one system and one sensor to control each process. On the other hand, there are systems such as PLC (Programmable Logic Control), which can process several signals simultaneously. However it is still necessary to use one sensor for each variable. Therefore, in the present work the use of a multipoint sensor to solve such problem has been proposed. The sensor consists of an optical fiber laser with two Fabry-Perot cavities constructed using fiber Bragg gratings (FBG). In the same system is possible to measure changes in two variables by detecting the intermodal separation frequency of each cavity and evaluate their amplitudes. The intermodal separation frequency depends on each cavity length. The sensor signals are monitored through an oscilloscope or a PCI card and after that acquired by PC, where they are analyzed and displayed. Results of the evaluation of the intermodal frequency separation peak amplitude behavior with FBG stretching are presented.

A fiber Bragg grating acceleration sensor for ground surveillance

Science.gov (United States)

Jiang, Shaodong; Zhang, Faxiang; Lv, Jingsheng; Ni, Jiasheng; Wang, Chang

2017-10-01

Ground surveillance system is a kind of intelligent monitoring equipment for detecting and tracking the ground target. This paper presents a fiber Bragg grating (FBG) acceleration sensor for ground surveillance, which has the characteristics of no power supply, anti-electromagnetic interference, easy large-scale networking, and small size. Which make it able to achieve the advantage of the ground surveillance system while avoiding the shortcoming of the electric sensing. The sensor has a double cantilever beam structure with a sensitivity of 1000 pm/g. Field experiment has been carried out on a flood beach to examine the sensor performance. The result shows that the detection distance on the walking of personnel reaches 70m, and the detection distance on the ordinary motor vehicle reaches 200m. The performance of the FBG sensor can satisfy the actual needs of the ground surveillance system.

A fiber Bragg grating--bimetal temperature sensor for solar panel inverters.

Science.gov (United States)

Ismail, Mohd Afiq; Tamchek, Nizam; Hassan, Muhammad Rosdi Abu; Dambul, Katrina D; Selvaraj, Jeyrai; Rahim, Nasrudin Abd; Sandoghchi, Reza; Adikan, Faisal Rafiq Mahamd

2011-01-01

This paper reports the design, characterization and implementation of a fiber Bragg grating (FBG)-based temperature sensor for an insulted-gate Bipolar transistor (IGBT) in a solar panel inverter. The FBG is bonded to the higher coefficient of thermal expansion (CTE) side of a bimetallic strip to increase its sensitivity. Characterization results show a linear relationship between increasing temperature and the wavelength shift. It is found that the sensitivity of the sensor can be categorized into three characterization temperature regions between 26 °C and 90 °C. The region from 41 °C to 90 °C shows the highest sensitivity, with a value of 14 pm/°C. A new empirical model that considers both temperature and strain effects has been developed for the sensor. Finally, the FBG-bimetal temperature sensor is placed in a solar panel inverter and results confirm that it can be used for real-time monitoring of the IGBT temperature.

Fiber Optic Bragg Grating Sensors for Thermographic Detection of Subsurface Anomalies

Science.gov (United States)

Allison, Sidney G.; Winfree, William P.; Wu, Meng-Chou

2009-01-01

Conventional thermography with an infrared imager has been shown to be an extremely viable technique for nondestructively detecting subsurface anomalies such as thickness variations due to corrosion. A recently developed technique using fiber optic sensors to measure temperature holds potential for performing similar inspections without requiring an infrared imager. The structure is heated using a heat source such as a quartz lamp with fiber Bragg grating (FBG) sensors at the surface of the structure to detect temperature. Investigated structures include a stainless steel plate with thickness variations simulated by small platelets attached to the back side using thermal grease. A relationship is shown between the FBG sensor thermal response and variations in material thickness. For comparison, finite element modeling was performed and found to agree closely with the fiber optic thermography results. This technique shows potential for applications where FBG sensors are already bonded to structures for Integrated Vehicle Health Monitoring (IVHM) strain measurements and can serve dual-use by also performing thermographic detection of subsurface anomalies.

Monitoring of fatigue damage in composite lap-joints using guided waves and FBG sensors

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Karpenko, Oleksii; Khomenko, Anton; Koricho, Ermias; Haq, Mahmoodul; Udpa, Lalita

2016-02-01

Adhesive bonding is being increasingly employed in many applications as it offers possibility of light-weighting and efficient multi-material joining along with reduction in time and cost of manufacturing. However, failure initiation and progression in critical components like joints, specifically in fatigue loading is not well understood, which necessitates reliable NDE and SHM techniques to ensure structural integrity. In this work, concurrent guided wave (GW) and fiber Bragg grating (FBG) sensor measurements were used to monitor fatigue damage in adhesively bonded composite lap-joints. In the present set-up, one FBG sensor was strategically embedded in the adhesive bond-line of a lap-joint, while two other FBGs were bonded on the surface of the adherends. Full spectral responses of FBG sensors were collected and compared at specific intervals of fatigue loading. In parallel, guided waves were actuated and sensed using PZT wafers mounted on the composite adherends. Experimental results demonstrated that time-of-flight (ToF) of the fundamental modes transmitted through the bond-line and spectral response of FBG sensors were sensitive to fatigue loading and damage. Combination of guided wave and FBG measurements provided the desired redundancy and synergy in the data to evaluate the degradation in bond-line properties. Measurements taken in the presence of continuously applied load replicated the in-situ/service conditions. The approach shows promise in understanding the behavior of bonded joints subjected to complex loading.

Crack Growth Monitoring by Embedded Optical Fibre Bragg Grating Sensors: Fibre Reinforced Plastic Crack Growing Detection

DEFF Research Database (Denmark)

Pereira, Gilmar Ferreira; Mikkelsen, Lars Pilgaard; McGugan, Malcolm

2015-01-01

This article presents a novel method to asses a crack growing/damage event in fibre reinforced plastic, or adhesive using Fibre Bragg Grating (FBG) sensors embedded in a host material. Different features of the crack mechanism that induce a change in the FBG response were identified. Double Canti...

Interrogation of weak Bragg grating sensors based on dual-wavelength differential detection.

Science.gov (United States)

Cheng, Rui; Xia, Li

2016-11-15

It is shown that for weak Bragg gratings the logarithmic ratio of reflected intensities at any two wavelengths within the spectrum follows a linear relationship with the Bragg wavelength shift, with a slope proportional to their wavelength spacing. This finding is exploited to develop a flexible, efficient, and cheap interrogation solution of weak fiber Bragg grating (FBGs), especially ultra-short FBGs, in distributed sensing based on dual-wavelength differential detection. The concept is experimentally studied in both single and distributed sensing systems with ultra-short FBG sensors. The work may form the basis of new and promising FBG interrogation techniques based on detecting discrete rather than continuous spectra.

Assessment of damage in composite laminates through dynamic, full-spectral interrogation of fiber Bragg grating sensors

International Nuclear Information System (INIS)

Propst, A; Peters, K; Zikry, M A; Schultz, S; Kunzler, W; Zhu, Z; Wirthlin, M; Selfridge, R

2010-01-01

In this study, we demonstrate the full-spectral interrogation of a fiber Bragg grating (FBG) sensor at 535 Hz. The sensor is embedded in a woven, graphite fiber–epoxy composite laminate subjected to multiple low-velocity impacts. The measurement of unique, time dependent spectral features from the FBG sensor permits classification of the laminate lifetime into five regimes. These damage regimes compare well with previous analysis of the same material system using combined global and local FBG sensor information. Observed transient spectral features include peak splitting, wide spectral broadening and a strong single peak at the end of the impact event. Such features could not be measured through peak wavelength interrogation of the FBG sensor. Cross-correlation of the measured spectra with the original embedded FBG spectrum permitted rapid visualization of average strains and the presence of transverse compressive strain on the optical fiber, but smeared out the details of the spectral profile

Monitoring Poisson’s Ratio Degradation of FRP Composites under Fatigue Loading Using Biaxially Embedded FBG Sensors

Science.gov (United States)

Akay, Erdem; Yilmaz, Cagatay; Kocaman, Esat S.; Turkmen, Halit S.; Yildiz, Mehmet

2016-01-01

The significance of strain measurement is obvious for the analysis of Fiber-Reinforced Polymer (FRP) composites. Conventional strain measurement methods are sufficient for static testing in general. Nevertheless, if the requirements exceed the capabilities of these conventional methods, more sophisticated techniques are necessary to obtain strain data. Fiber Bragg Grating (FBG) sensors have many advantages for strain measurement over conventional ones. Thus, the present paper suggests a novel method for biaxial strain measurement using embedded FBG sensors during the fatigue testing of FRP composites. Poisson’s ratio and its reduction were monitored for each cyclic loading by using embedded FBG sensors for a given specimen and correlated with the fatigue stages determined based on the variations of the applied fatigue loading and temperature due to the autogenous heating to predict an oncoming failure of the continuous fiber-reinforced epoxy matrix composite specimens under fatigue loading. The results show that FBG sensor technology has a remarkable potential for monitoring the evolution of Poisson’s ratio on a cycle-by-cycle basis, which can reliably be used towards tracking the fatigue stages of composite for structural health monitoring purposes. PMID:28773901

Fluoride contamination sensor based on optical fiber grating technology

Science.gov (United States)

Jadhav, Mangesh S.; Laxmeshwar, Lata S.; Akki, Jyoti F.; Raikar, P. U.; Kumar, Jitendra; Prakash, Om; Raikar, U. S.

2017-11-01

A number of distinct advantages of the optical fiber technology in the field of sensors and communications which leads to enormous applications. Fiber Bragg grating (FBG) developed from the fabrication of photosensitive fiber through phase mask technique is used in the present report. The designed fiber sensor used for the detection and determination of contaminants in drinking water at ppm & ppb level and it is considered as a special type of concentration sensor. The test samples of drinking water have been collected from different regions. In this paper we have calibrated the FBG sensor to detect Flouride concentration in drinking water in the range of 0.05-8 ppm. According to WHO, the normal range of fluoride content in drinking water is about 0.7 ppm to 1.5 ppm. The results for resultant spectral shifts for test samples are closely agree with standard values.

Cure monitoring of epoxy resin by using fiber bragg grating sensor

Energy Technology Data Exchange (ETDEWEB)

Lee, Jin Hyuk [KEPCO, Naju (Korea, Republic of); Kim, Dae Hyun [Dept. of Mechanical and Automotive Engineering, Seoul National University of Science and Technology, Seoul (Korea, Republic of)

2016-06-15

In several industrial fields, epoxy resin is widely used as an adhesive for co-curing and manufacturing various structures. Controlling the manufacturing process is required for ensuring robust bonding performance and the stability of the structures. A fiber optic sensor is suitable for the cure monitoring of epoxy resin owing to the thready shape of the sensor. In this paper, a fiber Bragg grating (FBG) sensor was applied for the cure monitoring of epoxy resin. Based on the experimental results, it was demonstrated that the FBG sensor can monitor the status of epoxy resin curing by measuring the strain caused by volume shrinkage and considering the compensation of temperature. In addition, two types of epoxy resin were used for the cure-monitoring; moreover, when compared to each other, it was found that the two types of epoxy had different cure-processes in terms of the change of strain during the curing. Therefore, the study proved that the FBG sensor is very profitable for the cure-monitoring of epoxy resin.

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

Directory of Open Access Journals (Sweden)

Guohui Lyu

2017-02-01

Full Text Available 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.

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

Science.gov (United States)

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

2017-02-15

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.

Analysis and experimental study on the strain transfer mechanism of an embedded basalt fiber-encapsulated fiber Bragg grating sensor

Science.gov (United States)

Zhang, Zhenglin; Wang, Yuan; Sun, Yangyang; Zhang, Qinghua; You, Zewei; Huang, Xiaodi

2017-01-01

The precision of the encapsulated fiber optic sensor embedded into a host suffers from the influences of encapsulating materials. Furthermore, an interface transfer effect of strain sensing exists. This study uses an embedded basalt fiber-encapsulated fiber Bragg grating (FBG) sensor as the research object to derive an expression in a multilayer interface strain transfer coefficient by considering the mechanical properties of the host material. The direct impact of the host material on the strain transfer at an embedded multipoint continuous FBG (i.e., multiple gratings written on a single optical fiber) monitoring strain sensor, which was self-developed and encapsulated with basalt fiber, is studied to present the strain transfer coefficients corresponding to the positions of various gratings. The strain transfer coefficients of the sensor are analyzed based on the experiments designed for this study. The error of the experimental results is ˜2 μɛ when the strain is at 60 μɛ and below. Moreover, the measured curves almost completely coincide with the theoretical curves. The changes in the internal strain field inside the embedded structure of the basalt fiber-encapsulated FBG strain sensor could be easily monitored. Hence, important references are provided to measure the internal stress strain of the sensor.

Effective refractive index modulation based optical fiber humidity sensor employing etched fiber Bragg grating

Science.gov (United States)

Mundendhar, Pathi; Khijwania, Sunil K.

2015-09-01

Relative humidity (RH) sensor employing etched fiber Bragg grating (FBG) is reported where RH variations are captured using effective-index-modulation, rather than traditional strain-modulation. Additionly, linear sensor response over wide dynamic range with optimum characteristics is focused. Comprehensive experimental investigation is carried out for the sensor that comprises uniformly etched cladding in the FBG region. Obtained results are observed to be in agreement with the theoretical analysis. Sensor response is observed to be linear over dynamic range 3-94%RH with ~ 0.082 pm/%RH sensitivity, ~0.6%RH resolution, ~ +/-2.5%RH accuracy, ~ +/-0.2 pm average discrepancy and ~ 0.2s response time during humidification/desiccation.

[Spectral analysis of fiber bragg grating modulated by double long period grating and its application in smart structure monitoring].

Science.gov (United States)

Lu, Ji-Yun; Liang, Da-Kai; Zhang, Xiao-Li; Zhu, Zhu

2009-12-01

Spectrum of fiber bragg grating (FBG) sensor modulated by double long period grating (LPFG) is proposed in the paper. Double LPFG consists of two LPFGS whose center wavelengths are the same and reflection spectrum of FBG sensor is located in linear range of double LPFG transmission spectrum. Based on spectral analysis of FBG and double LPFG, reflection spectrum of FBG modulated by double LPFG is obtained and studied by use of band-hider filter characteristics for double LPFG. An FBG sensor is attached on the surface of thin steel beam, which is strained by bending, and the center wavelength of FBG sensor will shift. The spectral peak of FBG sensor modulated by double LPFG is changed correspondingly, and the spectral change will lead to variation in exit light intensity from double LPFG. Experiment demonstrates that the relation of filtering light intensity from double LPFG monitored by optical power meter to center wavelength change of FBG sensor is linear and the minimum strain of material (steel beam) detected by the modulation and demodulation system is 1.05 microepsilon. This solution is used in impact monitoring of optical fibre smart structure, and FBG sensor is applied for impulse response signal monitoring induced by low-velocity impact, when impact pendulum is loaded to carbon fiber-reinforced plastics (CFP). The acquired impact response signal and fast Fourier transform of the signal detected by FBG sensor agree with the measurement results of eddy current displacement meter attached to the FBG sensor. From the results, the present method using FBG sensor is found to be effective for monitoring the impact. The research provides a practical reference in dynamic monitoring of optical fiber smart structure field.

Health monitoring system for a tall building with Fiber Bragg grating sensors

Science.gov (United States)

Li, D. S.; Li, H. N.; Ren, L.; Guo, D. S.; Song, G. B.

2009-03-01

Fiber Bragg grating (FBG) sensors demonstrate great potentials for structural health monitoring of civil structures to ensure their structural integrity, durability and reliability. The advantages of applying fiber optic sensors to a tall building include their immunity of electromagnetic interference and multiplexing ability to transfer optical signals over a long distance. In the work, FBG sensors, including strain and temperature sensors, are applied to the construction monitoring of an 18-floor tall building starting from its construction date. The main purposes of the project are: 1) monitoring the temperature evolution history within the concrete during the pouring process; 2) measuring the variations of the main column strains on the underground floor while upper 18 floors were subsequently added on; and 3) monitoring the relative displacements between two foundation blocks. The FBG sensors have been installed and interrogated continuously for more than five months. Monitoring results of temperature and strains during the period are presented in the paper. Furthermore, the lag behavior between the concrete temperature and its surrounding air temperature is investigated.

Fiber Bragg grating sensor interrogators on chip: challenges and opportunities

Science.gov (United States)

Marin, Yisbel; Nannipieri, Tiziano; Oton, Claudio J.; Di Pasquale, Fabrizio

2017-04-01

In this paper we present an overview of the current efforts towards integration of Fiber Bragg Grating (FBG) sensor interrogators. Different photonic integration platforms will be discussed, including monolithic planar lightwave circuit technology, silicon on insulator (SOI), indium phosphide (InP) and gallium arsenide (GaAs) material platforms. Also various possible techniques for wavelength metering and methods for FBG multiplexing will be discussed and compared in terms of resolution, dynamic performance, multiplexing capabilities and reliability. The use of linear filters, array waveguide gratings (AWG) as multiple linear filters and AWG based centroid signal processing techniques will be addressed as well as interrogation techniques based on tunable micro-ring resonators and Mach-Zehnder interferometers (MZI) for phase sensitive detection. The paper will also discuss the challenges and perspectives of photonic integration to address the increasing requirements of several industrial applications.

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

Science.gov (United States)

Koyama, Shouhei; Ishizawa, Hiroaki; Fujimoto, Keisaku; Chino, Shun; Kobayashi, Yuka

2016-12-28

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.

Monitoring the corrosion process of reinforced concrete using BOTDA and FBG sensors.

Science.gov (United States)

Mao, Jianghong; Chen, Jiayun; Cui, Lei; Jin, Weiliang; Xu, Chen; He, Yong

2015-04-15

Expansion and cracking induced by the corrosion of reinforcement concrete is the major factor in the failure of concrete durability. Therefore, monitoring of concrete cracking is critical for evaluating the safety of concrete structures. In this paper, we introduce a novel monitoring method combining Brillouin optical time domain analysis (BOTDA) and fiber Bragg grating (FBG), based on mechanical principles of concrete expansion cracking. BOTDA monitors concrete expansion and crack width, while FBG identifies the time and position of cracking. A water-pressure loading simulation test was carried out to determine the relationship between fiber strain, concrete expansion and crack width. An electrical accelerated corrosion test was also conducted to evaluate the ability of this novel sensor to monitor concrete cracking under practical conditions.

Long-term monitoring FBG-based cable load sensor

Science.gov (United States)

Zhang, Zhichun; Zhou, Zhi; Wang, Chuan; Ou, Jinping

2006-03-01

Stay cables are the main load-bearing components of stayed-cable bridges. The cables stress status is an important factor to the stayed-cable bridge structure safety evaluation. So it's very important not only to the bridge construction, but also to the long-term safety evaluation for the bridge structure in-service. The accurate measurement for cable load depends on an effective sensor, especially to meet the long time durability and measurement demand. FBG, for its great advantage of corrosion resistance, absolute measurement, high accuracy, electro-magnetic resistance, quasi-distribution sensing, absolute measurement and so on, is the most promising sensor, which can cater for the cable force monitoring. In this paper, a load sensor has been developed, which is made up of a bushing elastic supporting body, 4 FBGs uniformly-spaced attached outside of the bushing supporting body, and a temperature compensation FBG for other four FBGs, moreover a cover for protection of FBGs. Firstly, the sensor measuring principle is analyzed, and relationship equation of FBG wavelength shifts and extrinsic load has also been gotten. And then the sensor calibration experiments of a steel cable stretching test with the FBG load sensor and a reference electric pressure sensor is finished, and the results shows excellent linearity of extrinsic load and FBG wavelength shifts, and good repeatability, which indicates that such kind of FBG-based load sensor is suitable for load measurement, especially for long-term, real time monitoring of stay-cables.

Structural Stability Monitoring of a Physical Model Test on an Underground Cavern Group during Deep Excavations Using FBG Sensors

Directory of Open Access Journals (Sweden)

Yong Li

2015-08-01

Full Text Available Fiber Bragg Grating (FBG sensors are comprehensively recognized as a structural stability monitoring device for all kinds of geo-materials by either embedding into or bonding onto the structural entities. The physical model in geotechnical engineering, which could accurately simulate the construction processes and the effects on the stability of underground caverns on the basis of satisfying the similarity principles, is an actual physical entity. Using a physical model test of underground caverns in Shuangjiangkou Hydropower Station, FBG sensors were used to determine how to model the small displacements of some key monitoring points in the large-scale physical model during excavation. In the process of building the test specimen, it is most successful to embed FBG sensors in the physical model through making an opening and adding some quick-set silicon. The experimental results show that the FBG sensor has higher measuring accuracy than other conventional sensors like electrical resistance strain gages and extensometers. The experimental results are also in good agreement with the numerical simulation results. In conclusion, FBG sensors could effectively measure small displacements of monitoring points in the whole process of the physical model test. The experimental results reveal the deformation and failure characteristics of the surrounding rock mass and make some guidance for the in situ engineering construction.

Intensity liquid level sensor based on multimode interference and fiber Bragg grating

International Nuclear Information System (INIS)

Oliveira, Ricardo; Aristilde, Stenio; Osório, Jonas H; Cordeiro, Cristiano M B; Franco, Marcos A R; Bilro, Lúcia; Nogueira, Rogério N

2016-01-01

In this paper an intensity liquid level sensor based on a single-mode—no-core—single-mode (SMS) fiber structure together with a Bragg grating inscribed in the later single mode fiber is proposed. As the no-core fiber is sensitive to the external refractive index, the SMS spectral response will be shifted related to the length of no-core fiber that is immersed in a liquid. By positioning the FBG central wavelength at the spectral region of the SMS edge filter, it is possible to measure the liquid level using the reflected FBG peak power through an intensity-based approach. The sensor is also self-referenced using the peak power of another FBG that is placed before and far from the sensing part. The temperature error analysis was also studied revealing that the sensor can operate in environments where the temperature changes are minimal. The possibility to use a second setup that makes the whole device temperature insensitive is also discussed. (paper)

Deflection estimation of a wind turbine blade using FBG sensors embedded in the blade bonding line

International Nuclear Information System (INIS)

Kim, Sang-Woo; Kang, Woo-Ram; Jeong, Min-Soo; Lee, In; Kwon, Il-Bum

2013-01-01

Estimating the deflection of flexible composite wind turbine blades is very important to prevent the blades from hitting the tower. Several researchers have used fiber Bragg grating (FBG) sensors—a type of optical fiber sensor (OFS)—to monitor the structural behavior of the blades. They can be installed on the surface and/or embedded in the interior of composites. However, the typical installation positions of OFSs present several problems, including delamination of sensing probes and a higher risk of fiber breakage during installation. In this study, we proposed using the bonding line between the shear web and spar cap as a new installation position of embedded OFSs for estimating the deflection of the blades. Laboratory coupon tests were undertaken preliminarily to confirm the strain measuring capability of embedded FBG sensors in adhesive layers, and the obtained values were verified by comparison with results obtained by electrical strain gauges and finite element analysis. We performed static loading tests on a 100 kW composite wind turbine blade to evaluate its deflections using embedded FBG sensors positioned in the bonding line. The deflections were estimated by classical beam theory considering a rigid body rotation near the tip of the blade. The evaluated tip deflections closely matched those measured by a linear variable differential transformer. Therefore, we verified the capability of embedded FBG sensors for evaluating the deflections of wind turbine blades. In addition, we confirmed that the bonding line between the shear web and spar cap is a practical location to embed the FBG sensors. (paper)

Strain measurements by fiber Bragg grating sensors for in situ pile loading tests

Science.gov (United States)

Schmidt-Hattenberger, Cornelia; Straub, Tilmann; Naumann, Marcel; Borm, Günter; Lauerer, Robert; Beck, Christoph; Schwarz, Wolfgang

2003-07-01

A fiber Bragg grating (FBG) sensor network has been installed into a large diameter concrete pile on a real construction site. The intention was to monitor its deformation behavior during several quasi-static loading cycles. The skin friction between pile and subsoil affecting the ultimate bearing capacity of the pile as well as the settlement behavior of the structure under investigation has been derived from our measurements. A comparison between the results of the fiber Bragg grating sensors and conventional concrete strain gages (CSG) has shown excellent correspondence.

Modeling FBG sensors sensitivity from cryogenic temperatures to room temperature as a function of metal coating thickness

Science.gov (United States)

Vendittozzi, Cristian; Felli, Ferdinando; Lupi, Carla

2018-05-01

Fiber optics with photo-imprinted Bragg grating have been studied in order to be used as temperature sensors in cryogenic applications. The main disadvantage presented by Fiber Bragg Grating (FBG) sensors is the significant drop in sensitivity as temperature decreases, mainly due to the critical lowering of the thermo-optic coefficient of the fiber and the very low thermal expansion coefficient (CTE) of fused silica at cryogenic temperatures. Thus, especially for the latter, it is important to enhance sensitivity to temperature by depositing a metal coating presenting higher CTE. In this work the thermal sensitivity of metal-coated FBG sensors has been evaluated by considering their elongation within temperature variations in the cryogenic range, as compared to bare fiber sensors. To this purpose, a theoretical model simulating elongation of metal-coated sensors has been developed. The model has been used to evaluate the behaviour of different metals which can be used as coating (Ni, Cu, Al, Zn, Pb and In). The optimal coating thickness has been calculated at different fixed temperature (from 5 K to 100 K) for each metal. It has been found that the metal coating effectiveness depends on thickness and operating temperature in accordance to our previous experimental work and theory suggest.

Measurement of temperature and pressure on the surface of a blunt cone using FBG sensor in hypersonic wind tunnel

Science.gov (United States)

Prasad, A. S. Guru; Sharath, U.; Nagarjun, V.; Hegde, G. M.; Asokan, S.

2013-09-01

Measurement of temperature and pressure exerted on the leeward surface of a blunt cone specimen has been demonstrated in the present work in a hypersonic wind tunnel using fiber Bragg grating (FBG) sensors. The experiments were conducted on a 30° apex-angle blunt cone with 51 mm base diameter at wind flow speeds of Mach 6.5 and 8.35 in a 300 mm hypersonic wind tunnel of Indian Institute of Science, Bangalore. A special pressure insensitive temperature sensor probe along with the conventional bare FBG sensors was used for explicit temperature and aerodynamic pressure measurement respectively on the leeward surface of the specimen. computational fluid dynamics (CFD) simulation of the flow field around the blunt cone specimen has also been carried out to obtain the temperature and pressure at conditions analogous to experiments. The results obtained from FBG sensors and the CFD simulations are found to be in good agreement with each other.

Measurement of temperature and pressure on the surface of a blunt cone using FBG sensor in hypersonic wind tunnel

International Nuclear Information System (INIS)

Guru Prasad, A S; Sharath, U; Asokan, S; Nagarjun, V; Hegde, G M

2013-01-01

Measurement of temperature and pressure exerted on the leeward surface of a blunt cone specimen has been demonstrated in the present work in a hypersonic wind tunnel using fiber Bragg grating (FBG) sensors. The experiments were conducted on a 30° apex-angle blunt cone with 51 mm base diameter at wind flow speeds of Mach 6.5 and 8.35 in a 300 mm hypersonic wind tunnel of Indian Institute of Science, Bangalore. A special pressure insensitive temperature sensor probe along with the conventional bare FBG sensors was used for explicit temperature and aerodynamic pressure measurement respectively on the leeward surface of the specimen. computational fluid dynamics (CFD) simulation of the flow field around the blunt cone specimen has also been carried out to obtain the temperature and pressure at conditions analogous to experiments. The results obtained from FBG sensors and the CFD simulations are found to be in good agreement with each other. (paper)

Modelling non-uniform strain distributions in aerospace composites using fibre Bragg gratings

NARCIS (Netherlands)

Rajabzadehdizaji, Aydin; Groves, R.M.; Hendriks, R.C.; Heusdens, R.; Chung, Y.; Jin, W.; Lee, B.; Canning, J.; Nakamura, K.; Yuan, L.

2017-01-01

In this paper the behaviour of fibre Bragg grating (FBG) sensors under non-uniform strain distributions was analysed. Using the fundamental matrix approach, the length of the FBG sensor was discretised, with each segment undergoing different strain values. FBG sensors that are embedded inside

Fiber Bragg grating sensors in harsh environments: considerations and industrial monitoring applications

Science.gov (United States)

Méndez, Alexis

2017-06-01

Over the last few years, fiber optic sensors (FOS) have seen an increased acceptance and widespread use in industrial sensing and in structural monitoring in civil, aerospace, marine, oil & gas, composites and other applications. One of the most prevalent types in use today are fiber Bragg grating (FBG) sensors. Historically, FOS have been an attractive solution because of their EM immunity and suitability for use in harsh environments and rugged applications with extreme temperatures, radiation exposure, EM fields, high voltages, water contact, flammable atmospheres, or other hazards. FBG sensors have demonstrated that can operate reliably in many different harsh environment applications but proper type and fabrication process are needed, along with suitable packaging and installation procedure. In this paper, we review the impact that external factors and environmental conditions play on FBG's performance and reliability, and describe the appropriate sensor types and protection requirements suitable for a variety of harsh environment applications in industrial furnaces, cryogenic coolers, nuclear plants, maritime vessels, oil & gas wells, aerospace crafts, automobiles, and others.

A IR-Femtosecond Laser Hybrid Sensor to Measure the Thermal Expansion and Thermo-Optical Coefficient of Silica-Based FBG at High Temperatures.

Science.gov (United States)

Li, Litong; Lv, Dajuan; Yang, Minghong; Xiong, Liangming; Luo, Jie

2018-01-26

In this paper, a hybrid sensor was fabricated using a IR-femtosecond laser to measure the thermal expansion and thermo-optical coefficient of silica-based fiber Bragg gratings (FBGs). The hybrid sensor was composed of an inline fiber Fabry-Perot interferometer (FFPI) cavity and a type-II FBG. Experiment results showed that the type-II FBG had three high reflectivity resonances in the wavelength ranging from 1100 to 1600 nm, showing the peaks in 1.1, 1.3 and 1.5 μm, respectively. The thermal expansion and thermo-optical coefficient (1.3 μm, 1.5 μm) of silica-based FBG, under temperatures ranging from 30 to 1100 °C, had been simultaneously calculated by measuring the wavelength of the type-II FBG and FFPI cavity length.

Fiber Bragg grating sensor based on cantilever structure embedded in polymer 3D printed material

Science.gov (United States)

Lima, Rita; Tavares, R.; Silva, S. O.; Abreu, P.; Restivo, Maria T.; Frazão, O.

2017-04-01

A cantilever structure in 3D printed based on a fiber Bragg grating (FBG) sensor embedded in polymer material is proposed. The FBG sensor was embedded in 3D printed coating and was tested under three physical parameters: displacement, temperature and vibration. The sensor was tested in displacement in two different regions of the cantilever, namely, on its midpoint and end point. The maximum displacement sensitivity achieved was (3 +/- 0.1) pm/mm for end point displacement, and a temperature sensitivity of (30 +/- 1) pm/°C was also attained. In the case of vibration measurements it was possible to obtain a 10.23Hz-low frequency oscillation.

Fiber Bragg grating sensor for simultaneous measurement of temperature and force using polymer open loop

Science.gov (United States)

Huang, Yonglin; Zhang, Shiyan

2014-07-01

A fiber Bragg grating (FBG) sensor for simultaneous measurement of temperature and force is proposed and demonstrated. Where a part of uniform FBG (about one half length of an FBG) is attached on the polymer open loop, the FBG is divided into two parts which has an equal length. So the two parts can be regarded as two FBGs. Because of the difference of the Young's modulus and the thermal expansion coefficients for two parts of the FBG, the two Bragg reflection wavelengths are shift when the temperature and force are applied on the sensor. Simultaneous measurement of temperature and force is demonstrated experimentally. The experimental results show that the linear response to temperature and force are achieved. The value of applied temperature and force can be obtained from the two Bragg wavelength shift via the coefficient matrix. This study provides a simple and economical method to measure temperature and force simultaneously.

A Fiber Bragg Grating Sensor Interrogation System Based on a Linearly Wavelength-Swept Thermo-Optic Laser Chip

Science.gov (United States)

Lee, Hyung-Seok; Lee, Hwi Don; Kim, Hyo Jin; Cho, Jae Du; Jeong, Myung Yung; Kim, Chang-Seok

2014-01-01

A linearized wavelength-swept thermo-optic laser chip was applied to demonstrate a fiber Bragg grating (FBG) sensor interrogation system. A broad tuning range of 11.8 nm was periodically obtained from the laser chip for a sweep rate of 16 Hz. To measure the linear time response of the reflection signal from the FBG sensor, a programmed driving signal was directly applied to the wavelength-swept laser chip. The linear wavelength response of the applied strain was clearly extracted with an R-squared value of 0.99994. To test the feasibility of the system for dynamic measurements, the dynamic strain was successfully interrogated with a repetition rate of 0.2 Hz by using this FBG sensor interrogation system. PMID:25177803

Multiplexed FBG and etched fiber sensors for process and health monitoring of 2-&3-D RTM components

OpenAIRE

Keulen, Casey J.; Yıldız, Mehmet; Yildiz, Mehmet; Suleman, Afzal

2011-01-01

This paper presents research being conducted on the use of a combination of fiber optic sensors for process and health monitoring of resin transfer molded (RTM) composite structures. A laboratory scale RTM apparatus has been designed and built with the capability of visually monitoring the resin filling process and embedding fiber optic sensors into the composite. Fiber Bragg gratings (FBG) and etched fiber sensors (EFS) have been multiplexed and embedded in quasi-2-D panels and 3-D hollow se...

Temperature monitoring with FBG sensor during diffuser-assisted laser-induced interstitial thermotherapy (Conference Presentation)

Science.gov (United States)

Pham, Ngot T.; Lee, Seul Lee; Lee, Yong Wook; Kang, Hyun Wook

2017-02-01

Temperature variations are often monitored by using sensors operating at the site of treatment during Laser-induced Interstitial Thermotherapy (LITT). Currently, temperature measurements during LITT have been performed with thermocouples (TCs). However, TCs could directly absorb laser light and lead to self-heating (resulting in an over-estimation). Fiber Bragg grating (FBG) sensors can instead overcome this limitation of the TCs due to its insensitivity to electromagnetic interference. The aim of the current study was to quantitatively evaluate the FBG temperature sensor with a K-type thermocouple to real-time monitor temperature increase in ex vivo tissue during diffuser-assisted LITT. A 4-W 980-nm laser was employed to deliver optical energy in continuous mode through a 600-µm core-diameter diffusing applicator. A goniometric measurement validated the uniform light distribution in polar and longitudinal directions. The FBG sensor showed a linear relationship (R2 = 0.995) between wavelength shift and temperature change in air and tissue along with a sensitivity of 0.0114 nm/˚C. Regardless of sensor type, the measured temperature increased with irradiation time and applied power but decreased with increasing distance from the diffuser surface. The temperature elevation augmented the degree of thermal coagulation in the tissue during LITT (4.0±0.3-mm at 99˚C after 120-s). The temperature elevation augmented the degree of thermal coagulation in the tissue during LITT s irradiation). The FBG-integrated diffuser was able to monitor the interstitial temperature in tubular tissue (porcine urethra) real-time during laser treatment. However, the thermal coagulation thickness of the porcine urethra was measured to be 1.5 mm that was slightly thicker ( 20%) than that of the bovine liver after 4-W 980-nm laser for 48 s. The FBG temperature sensor can be a feasible tool to real-time monitor the temporal development of the temperature during the diffuser-assisted LITT to

Oil pipeline geohazard monitoring using optical fiber FBG strain sensors (Conference Presentation)

Science.gov (United States)

Salazar-Ferro, Andres; Mendez, Alexis

2016-04-01

Pipelines are naturally vulnerable to operational, environmental and man-made effects such as internal erosion and corrosion; mechanical deformation due to geophysical risks and ground movements; leaks from neglect and vandalism; as well as encroachments from nearby excavations or illegal intrusions. The actual detection and localization of incipient and advanced faults in pipelines is a very difficult, expensive and inexact task. Anything that operators can do to mitigate the effects of these faults will provide increased reliability, reduced downtime and maintenance costs, as well as increased revenues. This talk will review the on-line monitoring of an extensive network of oil pipelines in service in Colombia using optical fiber Bragg grating (FBG) strain sensors for the measurement of strains and bending caused by geohazard risks such as soil movements, landslides, settlements, flooding and seismic activity. The FBG sensors were mounted on the outside of the pipelines at discrete locations where geohazard risk was expected. The system has been in service for the past 3 years with over 1,000 strain sensors mounted. The technique has been reliable and effective in giving advanced warning of accumulated pipeline strains as well as possible ruptures.

The characteristic of gap FBG and its application

Science.gov (United States)

Yang, Yuanhong; Hu, Jun; Liu, Xuejing; Jin, Wei

2015-07-01

A gap fiber Bragg grating (g-FBG) is fabricated by cutting a uniform FBG in the middle to introduce a small air gap between the two sections. Numerical and experimental investigations show that the g-FBG has the characteristics of both a phase shifted FBG and a Fizeau interferometer. The influence of the air-gap shift longitudinally or transversely with respect to the fiber central axis and temperature to g-FBG's spectrums are investigated with numerical simulation and experiments, and the mathematic models are made. Based on g-FBG's different sensitivity to gap width and temperature, a micro-gap and temperature simultaneous measurement sensor was demonstrated. And a g-FBG based tunable fiber ring laser with a narrow line-width is demonstrated.

Large Scale Applications Using FBG Sensors: Determination of In-Flight Loads and Shape of a Composite Aircraft Wing

Directory of Open Access Journals (Sweden)

Matthew J. Nicolas

2016-06-01

Full Text Available Technological advances have enabled the development of a number of optical fiber sensing methods over the last few years. The most prevalent optical technique involves the use of fiber Bragg grating (FBG sensors. These small, lightweight sensors have many attributes that enable their use for a number of measurement applications. Although much literature is available regarding the use of FBGs for laboratory level testing, few publications in the public domain exist of their use at the operational level. Therefore, this paper gives an overview of the implementation of FBG sensors for large scale structures and applications. For demonstration, a case study is presented in which FBGs were used to determine the deflected wing shape and the out-of-plane loads of a 5.5-m carbon-composite wing of an ultralight aerial vehicle. The in-plane strains from the 780 FBG sensors were used to obtain the out-of-plane loads as well as the wing shape at various load levels. The calculated out-of-plane displacements and loads were within 4.2% of the measured data. This study demonstrates a practical method in which direct measurements are used to obtain critical parameters from the high distribution of FBG sensors. This procedure can be used to obtain information for structural health monitoring applications to quantify healthy vs. unhealthy structures.

In Vivo Pattern Classification of Ingestive Behavior in Ruminants Using FBG Sensors and Machine Learning

Directory of Open Access Journals (Sweden)

Vinicius Pegorini

2015-11-01

Full Text Available Pattern classification of ingestive behavior in grazing animals has extreme importance in studies related to animal nutrition, growth and health. In this paper, a system to classify chewing patterns of ruminants in in vivo experiments is developed. The proposal is based on data collected by optical fiber Bragg grating sensors (FBG that are processed by machine learning techniques. The FBG sensors measure the biomechanical strain during jaw movements, and a decision tree is responsible for the classification of the associated chewing pattern. In this study, patterns associated with food intake of dietary supplement, hay and ryegrass were considered. Additionally, two other important events for ingestive behavior were monitored: rumination and idleness. Experimental results show that the proposed approach for pattern classification is capable of differentiating the five patterns involved in the chewing process with an overall accuracy of 94%.

In Vivo Pattern Classification of Ingestive Behavior in Ruminants Using FBG Sensors and Machine Learning.

Science.gov (United States)

Pegorini, Vinicius; Karam, Leandro Zen; Pitta, Christiano Santos Rocha; Cardoso, Rafael; da Silva, Jean Carlos Cardozo; Kalinowski, Hypolito José; Ribeiro, Richardson; Bertotti, Fábio Luiz; Assmann, Tangriani Simioni

2015-11-11

Pattern classification of ingestive behavior in grazing animals has extreme importance in studies related to animal nutrition, growth and health. In this paper, a system to classify chewing patterns of ruminants in in vivo experiments is developed. The proposal is based on data collected by optical fiber Bragg grating sensors (FBG) that are processed by machine learning techniques. The FBG sensors measure the biomechanical strain during jaw movements, and a decision tree is responsible for the classification of the associated chewing pattern. In this study, patterns associated with food intake of dietary supplement, hay and ryegrass were considered. Additionally, two other important events for ingestive behavior were monitored: rumination and idleness. Experimental results show that the proposed approach for pattern classification is capable of differentiating the five patterns involved in the chewing process with an overall accuracy of 94%.

Method for independent strain and temperature measurement in polymeric tensile test specimen using embedded FBG sensors

DEFF Research Database (Denmark)

Pereira, Gilmar Ferreira; McGugan, Malcolm; Mikkelsen, Lars Pilgaard

2016-01-01

to calculate independently the strain and temperature are presented in the article, together with a measurement resolution study. This multi-parameter measurement method was applied to an epoxy tensile specimen, tested in a unidirectional tensile test machine with a temperature controlled cabinet. A full......A novel method to obtain independent strain and temperature measurements using embedded Fibre Bragg Grating (FBG) in polymeric tensile test specimens is presented in this paper. The FBG strain and temperature cross-sensitivity was decoupled using two single mode FBG sensors, which were embedded...... of temperature, from 40 C to -10 C. The consistency of the expected theoretical results with the calibration procedure and the experimental validation shows that this proposed method is applicable to measure accurate strain and temperature in polymers during static or fatigue tensile testing. Two different...

Development of a Cloud Computing-Based Pier Type Port Structure Stability Evaluation Platform Using Fiber Bragg Grating Sensors.

Science.gov (United States)

Jo, Byung Wan; Jo, Jun Ho; Khan, Rana Muhammad Asad; Kim, Jung Hoon; Lee, Yun Sung

2018-05-23

Structure Health Monitoring is a topic of great interest in port structures due to the ageing of structures and the limitations of evaluating structures. This paper presents a cloud computing-based stability evaluation platform for a pier type port structure using Fiber Bragg Grating (FBG) sensors in a system consisting of a FBG strain sensor, FBG displacement gauge, FBG angle meter, gateway, and cloud computing-based web server. The sensors were installed on core components of the structure and measurements were taken to evaluate the structures. The measurement values were transmitted to the web server via the gateway to analyze and visualize them. All data were analyzed and visualized in the web server to evaluate the structure based on the safety evaluation index (SEI). The stability evaluation platform for pier type port structures involves the efficient monitoring of the structures which can be carried out easily anytime and anywhere by converging new technologies such as cloud computing and FBG sensors. In addition, the platform has been successfully implemented at “Maryang Harbor” situated in Maryang-Meyon of Korea to test its durability.

Finite element analysis-based study of fiber Bragg grating sensor for cracks detection in reinforced concrete

Science.gov (United States)

Wang, Lili; Xin, Xiangjun; Song, Jun; Wang, Honggang; Sai, Yaozhang

2018-02-01

Fiber Bragg sensor is applied for detecting and monitoring the cracks that occur in the reinforced concrete. We use the three-dimensional finite element model to provide the three-axial stresses along the fiber Bragg sensor and then converted the stresses as a wavelength deformation of fiber Bragg grating (FBG) reflected spectrum. For the crack detection, an FBG sensor with 10-mm length is embedded in the reinforced concrete, and its reflection spectrum is measured after loading is applied to the concrete slab. As a result, the main peak wavelength and the ratio of the peak reflectivity to the maximal side-mode reflectivity of the optic-fiber grating represent the fracture severity. The fact that the sharp decreasing of the ratio of the peak reflectivity to the maximal side-mode reflectivity represents the early crack is confirmed by the theoretical calculation. The method can be used to detect the cracks in the reinforced concrete and give safety evaluation of large-scale infrastructure.

Monitoring Poisson's ratio degradation of FRP composites under fatigue loading using biaxially embedded FBG sensors

OpenAIRE

Akay, Erdem; Yılmaz, Çağatay; Yilmaz, Cagatay; Kocaman, Esat Selim; Türkmen, Halit S.; Turkmen, Halit S.; Yıldız, Mehmet; Yildiz, Mehmet

2016-01-01

The significance of strain measurement is obvious for the analysis of Fiber-Reinforced Polymer (FRP) composites. Conventional strain measurement methods are sufficient for static testing in general. Nevertheless, if the requirements exceed the capabilities of these conventional methods, more sophisticated techniques are necessary to obtain strain data. Fiber Bragg Grating (FBG) sensors have many advantages for strain measurement over conventional ones. Thus, the present paper suggests a novel...

Development and Application of Smart Geogrid Embedded with Fiber Bragg Grating Sensors

Directory of Open Access Journals (Sweden)

Zheng-fang Wang

2015-01-01

Full Text Available Smart geogrids embedded with fiber Bragg grating (FBG for reinforcement as well as measurement of geotechnical structures have been developed. After the fabricating process of the geogrids is detailed, finite element (FE simulations are conducted to analyze the strain distribution of geogrids and the strain transfer characteristics from geogrids to fiber optic. Results indicate that FBG should be deployed in the middle of the geogrids rib to make sure that uniform strain distribution along the FBG. Also, PVC protective sleeves, which are used to protect fiber optic when integrated with geogrids, have smaller strain transfer loss than nylon sleeves. Tensile experiments are conducted to test strain measurement performance of proposed geogrids, and the results demonstrate that proposed smart geogrids have good linearity and consistency. Temperature experiments show that FBG embedded in geogrids has higher temperature sensitivity, and the temperature induced error can be compensated by an extra FBG strain-independent sensor. Furthermore, designed smart geogrids are used in a geotechnical model test to monitor strain during tunnel excavation. The strain tendency measured by smart geogrids and traditional strain sensor agree very well. The results indicate that smart geogrids embedded with FBGs can be an effective method to measure strains for geological engineering related applications.

Three-axis force sensor with fiber Bragg grating.

Science.gov (United States)

Hyundo Choi; Yoan Lim; Junhyung Kim

2017-07-01

Haptic feedback is critical for many surgical tasks, and it replicates force reflections at the surgical site. To meet the force reflection requirements, we propose a force sensor with an optical fiber Bragg grating (FBG) for robotic surgery. The force sensor can calculate three directional forces of an instrument from the strain of three FBGs, even under electromagnetic interference. A flexible ring-shape structure connects an instrument tip and fiber strain gages to sense three directional force. And a stopper mechanism is added in the structure to avoid plastic deformation under unexpected large force on the instrument tip. The proposed sensor is experimentally verified to have a sensing range from -12 N to 12 N, and its sensitivity was less than 0.06 N.

Femtosecond Laser Ablated FBG with Composite Microstructure for Hydrogen Sensor Application

Directory of Open Access Journals (Sweden)

Meng Zou

2016-12-01

Full Text Available A composite microstructure in fiber Bragg grating (FBG with film deposition for hydrogen detection is presented. Through ablated to FBG cladding by a femtosecond laser, straight-trenches and spiral micro-pits are formed. A Pd–Ag film is sputtered on the surface of the laser processed FBG single mode fiber, and acts as hydrogen sensing transducer. The demonstrated experimental outcomes show that a composite structure produced the highest sensitivity of 26.3 pm/%H, nearly sevenfold more sensitive compared with original standard FBG. It offers great potential in engineering applications for its good structure stability and sensitivity.

High Neutron Fluence Survivability Testing of Advanced Fiber Bragg Grating Sensors

International Nuclear Information System (INIS)

Fielder, Robert S.; Klemer, Daniel; Stinson-Bagby, Kelly L.

2004-01-01

The motivation for the reported research was to support NASA space nuclear power initiatives through the development of advanced fiber optic sensors for space-based nuclear power applications. The purpose of the high-neutron fluence testing was to demonstrate the survivability of fiber Bragg grating (FBG) sensors in a fission reactor environment. 520 FBGs were installed in the Ford reactor at the University of Michigan. The reactor was operated for 1012 effective full power hours resulting in a maximum neutron fluence of approximately 5x1019 n/cm2, and a maximum gamma dose of 2x103 MGy gamma. This work is significant in that, to the knowledge of the authors, the exposure levels obtained are approximately 1000 times higher than for any previously published experiment. Four different fiber compositions were evaluated. An 87% survival rate was observed for fiber Bragg gratings located at the fuel centerline. Optical Frequency Domain Reflectometry (OFDR), originally developed at the NASA Langley Research Center, can be used to interrogate several thousand low-reflectivity FBG strain and/or temperature sensors along a single optical fiber. A key advantage of the OFDR sensor technology for space nuclear power is the extremely low mass of the sensor, which consists of only a silica fiber 125μm in diameter. The sensors produced using this technology will fill applications in nuclear power for current reactor plants, emerging Generation-IV reactors, and for space nuclear power. The reported research was conducted by Luna Innovations and was funded through a Small Business Innovative Research (SBIR) contract with the NASA Glenn Research Center

Fiber Bragg Grating sensors for deformation monitoring of GEM foils in HEP detectors

CERN Document Server

AUTHOR|(CDS)2071648; Bianco, S; Caponero, M; Muhammad, S; Passamonti, L; Piccolo, D; Pierluigi, D; Raffone, G; Russo, A; Saviano, G

2015-01-01

Fiber Bragg Grating (FBG) sensors have been so far mainly used in high energy physics (HEP) as high precision positioning and re-positioning sensors and as low cost, easy to mount, radiation hard and low space- consuming temperature and humidity devices. FBGs are also commonly used for very precise strain measurements. In this work we present a novel use of FBGs as flatness and mechanical tensioning sensors applied to the wide Gas Electron Multiplier (GEM) foils of the GE1/1 chambers of the Compact Muon Solenoid (CMS) experiment at Large Hadron Collider (LHC) of CERN. A network of FBG sensors has been used to determine the optimal mechanical tension applied and to characterize the mechanical stress applied to the foils. The preliminary results of the test performed on a full size GE1/1 final prototype and possible future developments will be discussed.

Monitoring static shape memory polymers using a fiber Bragg grating as a vector-bending sensor

Science.gov (United States)

Li, Peng; Yan, Zhijun; Zhou, Kaiming; Zhang, Lin; Leng, Jinsong

2013-01-01

We propose and demonstrate a technique for monitoring the recovery deformation of the shape-memory polymers (SMP) using a surface-attached fiber Bragg grating (FBG) as a vector-bending sensor. The proposed sensing scheme could monitor the pure bending deformation for the SMP sample. When the SMP sample undergoes concave or convex bending, the resonance wavelength of the FBG will have red-shift or blue-shift according to the tensile or compressive stress gradient along the FBG. As the results show, the bending sensitivity is around 4.07 nm/cm-1. The experimental results clearly indicate that the deformation of such an SMP sample can be effectively monitored by the attached FBG not just for the bending curvature but also the bending direction.

Multi-parameter fibre Bragg grating sensor-array for thermal vacuum cycling test

Science.gov (United States)

Cheng, L.; Ahlers, B.; Toet, P.; Casarosa, G.; Appolloni, M.

2017-11-01

Fibre Bragg Grating (FBG) sensor systems based on optical fibres are gaining interest in space applications. Studies on Structural Health Monitoring (SHM) of the reusable launchers using FBG sensors have been carried out in the Future European Space Transportation Investigations Programme (FESTIP). Increasing investment in the development on FBG sensor applications is foreseen for the Future Launchers Preparatory Programme (FLPP). TNO has performed different SHM measurements with FBGs including on the VEGA interstage [1, 2] in 2006. Within the current project, a multi-parameter FBG sensor array demonstrator system for temperature and strain measurements is designed, fabricated and tested under ambient as well as Thermal Vacuum (TV) conditions in a TV chamber of the European Space Agency (ESA), ESTEC site. The aim is the development of a multi-parameters measuring system based on FBG technology for space applications. During the TV tests of a Space Craft (S/C) or its subsystems, thermal measurements, as well as strain measurements are needed by the engineers in order to verify their prediction and to validate their models. Because of the dimensions of the test specimen and the accuracy requested to the measurement, a large number of observation/measuring points are needed. Conventional sensor systems require a complex routing of the cables connecting the sensors to their acquisition unit. This will add extra weight to the construction under test. FBG sensors are potentially light-weight and can easily be multiplexed in an array configuration. The different tasks comply of a demonstrator system design; its component selection, procurement, manufacturing and finally its assembly. The temperature FBG sensor is calibrated in a dedicated laboratory setup down to liquid nitrogen (LN2) temperature at TNO. A temperature-wavelength calibration curve is generated. After a test programme definition a setup in thermal vacuum is realised at ESA premises including a mechanical

Advanced Interrogation of Fiber-Optic Bragg Grating and Fabry-Perot Sensors with KLT Analysis

Science.gov (United States)

Tosi, Daniele

2015-01-01

The Karhunen-Loeve Transform (KLT) is applied to accurate detection of optical fiber sensors in the spectral domain. By processing an optical spectrum, although coarsely sampled, through the KLT, and subsequently processing the obtained eigenvalues, it is possible to decode a plurality of optical sensor results. The KLT returns higher accuracy than other demodulation techniques, despite coarse sampling, and exhibits higher resilience to noise. Three case studies of KLT-based processing are presented, representing most of the current challenges in optical fiber sensing: (1) demodulation of individual sensors, such as Fiber Bragg Gratings (FBGs) and Fabry-Perot Interferometers (FPIs); (2) demodulation of dual (FBG/FPI) sensors; (3) application of reverse KLT to isolate different sensors operating on the same spectrum. A simulative outline is provided to demonstrate the KLT operation and estimate performance; a brief experimental section is also provided to validate accurate FBG and FPI decoding. PMID:26528975

Flood scour monitoring system using fiber Bragg grating sensors

Science.gov (United States)

Lin, Yung Bin; Lai, Jihn Sung; Chang, Kuo Chun; Li, Lu Sheng

2006-12-01

The exposure and subsequent undermining of pier/abutment foundations through the scouring action of a flood can result in the structural failure of a bridge. Bridge scour is one of the leading causes of bridge failure. Bridges subject to periods of flood/high flow require monitoring during those times in order to protect the traveling public. In this study, an innovative scour monitoring system using button-like fiber Bragg grating (FBG) sensors was developed and applied successfully in the field during the Aere typhoon period in 2004. The in situ FBG scour monitoring system has been demonstrated to be robust and reliable for real-time scour-depth measurements, and to be valid for indicating depositional depth at the Dadu Bridge. The field results show that this system can function well and survive a typhoon flood.

Optical fiber pressure sensor based on fiber Bragg grating

Science.gov (United States)

Song, Dongcao

In oil field, it is important to measure the high pressure and temperature for down-hole oil exploration and well-logging, the available traditional electronic sensor is challenged due to the harsh, flammable environment. Recently, applications based on fiber Bragg grating (FBG) sensor in the oil industry have become a popular research because of its distinguishing advantages such as electrically passive operation, immunity to electromagnetic interference, high resolution, insensitivity to optical power fluctuation etc. This thesis is divided into two main sections. In the first section, the design of high pressure sensor based on FBG is described. Several sensing elements based on FBG for high pressure measurements have been proposed, for example bulk-modulus or free elastic modulus. But the structure of bulk-modulus and free elastic modulus is relatively complex and not easy to fabricate. In addition, the pressure sensitivity is not high and the repeatability of the structure has not been investigated. In this thesis, a novel host material of carbon fiber laminated composite (CFLC) for high pressure sensing is proposed. The mechanical characteristics including principal moduli in three directions and the shape repeatability are investigated. Because of it's Young's modulus in one direction and anisotropic characteristics, the pressure sensor made by CFLC has excellent sensitivity. This said structure can be used in very high pressure measurement due to carbon fiber composite's excellent shape repetition even under high pressure. The experimental results show high pressure sensitivity of 0.101nm/MPa and high pressure measurement up to 70MPa. A pressure sensor based on CFLC and FBG with temperature compensation has been designed. In the second section, the design of low pressure sensor based on FBG is demonstrated. Due to the trade off between measurement range and sensitivity, a sensor for lower pressure range needs more sensitivity. A novel material of carbon

Impact Localization Method for Composite Plate Based on Low Sampling Rate Embedded Fiber Bragg Grating Sensors

Directory of Open Access Journals (Sweden)

Zhuo Pang

2017-01-01

Full Text Available Fiber Bragg Grating (FBG sensors have been increasingly used in the field of Structural Health Monitoring (SHM in recent years. In this paper, we proposed an impact localization algorithm based on the Empirical Mode Decomposition (EMD and Particle Swarm Optimization-Support Vector Machine (PSO-SVM to achieve better localization accuracy for the FBG-embedded plate. In our method, EMD is used to extract the features of FBG signals, and PSO-SVM is then applied to automatically train a classification model for the impact localization. Meanwhile, an impact monitoring system for the FBG-embedded composites has been established to actually validate our algorithm. Moreover, the relationship between the localization accuracy and the distance from impact to the nearest sensor has also been studied. Results suggest that the localization accuracy keeps increasing and is satisfactory, ranging from 93.89% to 97.14%, on our experimental conditions with the decrease of the distance. This article reports an effective and easy-implementing method for FBG signal processing on SHM systems of the composites.

Fiber Bragg Grating Sensor for Detection of Nitrate Concentration in Water

Directory of Open Access Journals (Sweden)

A. S. LALASANGI

2011-02-01

Full Text Available The concentrations of chemical species in drinking water are of great interest. We demonstrated etched fiber Bragg grating (FBG as a concentration sensor for nitrate by analyzing the Bragg wavelength shift with concentration of chemical solution. The FBG is fabricated by phase mask technique on single mode Ge-B co-doped photosensitive fiber. Sensitivity of FBGs to the surrounding solution concentration can be enhanced by reducing diameter of the cladding with 40 % HF solution. The maximum sensitivity achieved is 1.322 ´ 10-3 nm/ppm. The overall shift of Bragg wavelength is of the order of 6.611 ´ 10-2 nm for 10 to 50 ppm concentration.

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

OpenAIRE

R. Brian Jenkins; Peter Joyce; Deborah Mechtel

2017-01-01

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. Initia...

Nuclear Power Plant Prestressed Concrete Containment Vessel Structure Monitoring during Integrated Leakage Rate Testing Using Fiber Bragg Grating Sensors

Directory of Open Access Journals (Sweden)

Jinke Li

2017-04-01

Full Text Available As the last barrier of nuclear reactor, prestressed concrete containment vessels (PCCVs play an important role in nuclear power plants (NPPs. To test the mechanical property of PCCV during the integrated leakage rate testing (ILRT, a fiber Bragg grating (FBG sensor was used to monitor concrete strain. In addition, a finite element method (FEM model was built to simulate the progress of the ILRT. The results showed that the strain monitored by FBG had the same trend compared to the inner pressure variation. The calculation results showed a similar trend compared with the monitoring results and provided much information about the locations in which the strain sensors should be installed. Therefore, it is confirmed that FBG sensors and FEM simulation are very useful in PCCV structure monitoring.

An Intrusion Detection System for the Protection of Railway Assets Using Fiber Bragg Grating Sensors

Directory of Open Access Journals (Sweden)

Angelo Catalano

2014-09-01

Full Text Available We demonstrate the ability of Fiber Bragg Gratings (FBGs sensors to protect large areas from unauthorized activities in railway scenarios such as stations or tunnels. We report on the technological strategy adopted to protect a specific depot, representative of a common scenario for security applications in the railway environment. One of the concerns in the protection of a railway area centers on the presence of rail-tracks, which cannot be obstructed with physical barriers. We propose an integrated optical fiber system composed of FBG strain sensors that can detect human intrusion for protection of the perimeter combined with FBG accelerometer sensors for protection of rail-track access. Several trials were carried out in indoor and outdoor environments. The results demonstrate that FBG strain sensors bonded under a ribbed rubber mat enable the detection of intruder break-in via the pressure induced on the mat, whereas the FBG accelerometers installed under the rails enable the detection of intruders walking close to the railroad tracks via the acoustic surface waves generated by footsteps. Based on a single enabling technology, this integrated system represents a valuable intrusion detection system for railway security and could be integrated with other sensing functionalities in the railway field using fiber optic technology.

Embedded Fibre Bragg Grating Sensor Response Model: Crack Growing Detection in Fibre Reinforced Plastic Materials

DEFF Research Database (Denmark)

Pereira, Gilmar Ferreira; Mikkelsen, Lars Pilgaard; McGugan, Malcolm

2015-01-01

This article presents a novel method to simulate the sensor output response of a Fibre Bragg Grating (FBG) sensor when embedded in a host material (Composite material or adhesive), during a crack growing/damage event. A finite element model of the crack growth mechanisms was developed, and differ...... the applicability of this technique to more complicated structures, and to be used as a structural health monitoring design tool....

The capability of fiber Bragg grating sensors to measure amputees' trans-tibial stump/socket interface pressures.

Science.gov (United States)

Al-Fakih, Ebrahim A; Osman, Noor Azuan Abu; Eshraghi, Arezoo; Adikan, Faisal Rafiq Mahamd

2013-08-12

This study presents the first investigation into the capability of fiber Bragg grating (FBG) sensors to measure interface pressure between the stump and the prosthetic sockets of a trans-tibial amputee. FBG element(s) were recoated with and embedded in a thin layer of epoxy material to form a sensing pad, which was in turn embedded in a silicone polymer material to form a pressure sensor. The sensor was tested in real time by inserting a heavy-duty balloon into the socket and inflating it by using an air compressor. This test was conducted to examine the sensitivity and repeatability of the sensor when subjected to pressure from the stump of the trans-tibial amputee and to mimic the actual environment of the amputee's Patellar Tendon (PT) bar. The sensor exhibited a sensitivity of 127 pm/N and a maximum FSO hysteresis of around ~0.09 in real-time operation. Very good reliability was achieved when the sensor was utilized for in situ measurements. This study may lead to smart FBG-based amputee stump/socket structures for pressure monitoring in amputee socket systems, which will result in better-designed prosthetic sockets that ensure improved patient satisfaction.

An optical fiber Bragg grating and piezoelectric ceramic voltage sensor

Science.gov (United States)

Yang, Qing; He, Yanxiao; Sun, Shangpeng; Luo, Mandan; Han, Rui

2017-10-01

Voltage measurement is essential in many fields like power grids, telecommunications, metallurgy, railways, and oil production. A voltage-sensing unit, consisting of fiber Bragg gratings (FBGs) and piezoelectric ceramics, based on which an optical over-voltage sensor was proposed and fabricated in this paper. No demodulation devices like spectrometer or Fabry-Perot filter were needed to gain the voltage signal, and a relatively large sensing frequency range was acquired in this paper; thus, the cost of the sensing system is more acceptable in engineering application. The voltage to be measured was directly applied to the piezoelectric ceramic, and deformation of the ceramics and the grating would be caused because of the inverse piezoelectric effect. With a reference grating, the output light intensity change will be caused by the FBG center wavelength change; thus, the relationship between the applied voltage and the output light intensity was established. Validation of the sensor was accomplished in the frequency range from 50 Hz to 20 kHz and switching impulse waves with a test platform; good linearity of the input-output characteristic was achieved. A temperature validation test was completed, showing that the sensor maintains good temperature stability. Experimental results show that the optical over-voltage sensor can be used for voltage monitoring, and if applied with a voltage divider, the sensor can be used to measure high voltage.

An optical fiber Bragg grating and piezoelectric ceramic voltage sensor.

Science.gov (United States)

Yang, Qing; He, Yanxiao; Sun, Shangpeng; Luo, Mandan; Han, Rui

2017-10-01

Voltage measurement is essential in many fields like power grids, telecommunications, metallurgy, railways, and oil production. A voltage-sensing unit, consisting of fiber Bragg gratings (FBGs) and piezoelectric ceramics, based on which an optical over-voltage sensor was proposed and fabricated in this paper. No demodulation devices like spectrometer or Fabry-Perot filter were needed to gain the voltage signal, and a relatively large sensing frequency range was acquired in this paper; thus, the cost of the sensing system is more acceptable in engineering application. The voltage to be measured was directly applied to the piezoelectric ceramic, and deformation of the ceramics and the grating would be caused because of the inverse piezoelectric effect. With a reference grating, the output light intensity change will be caused by the FBG center wavelength change; thus, the relationship between the applied voltage and the output light intensity was established. Validation of the sensor was accomplished in the frequency range from 50 Hz to 20 kHz and switching impulse waves with a test platform; good linearity of the input-output characteristic was achieved. A temperature validation test was completed, showing that the sensor maintains good temperature stability. Experimental results show that the optical over-voltage sensor can be used for voltage monitoring, and if applied with a voltage divider, the sensor can be used to measure high voltage.

Enhanced Strain Measurement Range of an FBG Sensor Embedded in Seven-Wire Steel Strands.

Science.gov (United States)

Kim, Jae-Min; Kim, Chul-Min; Choi, Song-Yi; Lee, Bang Yeon

2017-07-18

FBG sensors offer many advantages, such as a lack of sensitivity to electromagnetic waves, small size, high durability, and high sensitivity. However, their maximum strain measurement range is lower than the yield strain range (about 1.0%) of steel strands when embedded in steel strands. This study proposes a new FBG sensing technique in which an FBG sensor is recoated with polyimide and protected by a polyimide tube in an effort to enhance the maximum strain measurement range of FBG sensors embedded in strands. The validation test results showed that the proposed FBG sensing technique has a maximum strain measurement range of 1.73% on average, which is 1.73 times higher than the yield strain of the strands. It was confirmed that recoating the FBG sensor with polyimide and protecting the FBG sensor using a polyimide tube could effectively enhance the maximum strain measurement range of FBG sensors embedded in strands.

Modeling the characteristic of the optical wavelength discriminator with fiber Bragg grating

Science.gov (United States)

Sikora, Aleksandra

2017-08-01

Using the transfer matrix method, the influence of fiber Bragg gratings' (FBG) characteristics on the optical wavelength discriminator characteristics was analyzed. The wavelength discriminator forms FBG and cooperates with the identical FBG sensor. The calculation was made for uniform and chirped FBGs. The comparison of the discriminators processing range measurement was analyzed. Presented results are crucial while choosing parameters of FBG used in constructing optical wavelength discriminators for strain and pressure sensor.

Use of FBG sensors for monitoring cracks of the equestrian statue of Bartolomeo Colleoni in Venice

Directory of Open Access Journals (Sweden)

F. Felli

2014-10-01

Full Text Available The Bartolomeo Colleoni monument suffered for years damage from the local climate. The process of restoring the Colleoni equestrian statue, started in 2003, allowed to understand how the bronze statue was originally cast and manufactured and the techniques used in its construction. During this process a relevant crack on the right foreleg was investigated in correspondence of the cast-on joining the right foreleg to the front portion of the horse body. The crack was investigated experimentally by Fiber Bragg Grating (FBG sensors, avoiding any modelling because of the very complex structure of the statue. An array of FBG sensors connected in series was glued on the crack with the aim of capturing live information about the effect of applying stress on the crack opening. The monitoring system was successfully tested during repositioning of the RIDER on the horse and is available for long term inspection of the crack opening evolution.

Humidity insensitive TOPAS polymer fiber Bragg grating sensor

DEFF Research Database (Denmark)

Yuan, Scott Wu; Khan, Lutul; Webb, David J.

2011-01-01

We report the first experimental demonstration of a humidity insensitive polymer optical fiber Bragg grating (FBG), as well as the first FBG recorded in a TOPAS polymer optical fiber in the important low loss 850nm spectral region. For the demonstration we have fabricated FBGs with resonance...... wavelength around 850 nm and 1550 nm in single-mode microstructured polymer optical fibers made of TOPAS and the conventional poly (methyl methacrylate) (PMMA). Characterization of the FBGs shows that the TOPAS FBG is more than 50 times less sensitive to humidity than the conventional PMMA FBG in both...... wavelength regimes. This makes the TOPAS FBG very appealing for sensing applications as it appears to solve the humidity sensitivity problem suffered by the PMMA FBG....

Internal and External Temperature Monitoring of a Li-Ion Battery with Fiber Bragg Grating Sensors

Directory of Open Access Journals (Sweden)

Susana Novais

2016-08-01

Full Text Available The integration of fiber Bragg grating (FBG sensors in lithium-ion cells for in-situ and in-operando temperature monitoring is presented herein. The measuring of internal and external temperature variations was performed through four FBG sensors during galvanostatic cycling at C-rates ranging from 1C to 8C. The FBG sensors were placed both outside and inside the cell, located in the center of the electrochemically active area and at the tab-electrode connection. The internal sensors recorded temperature variations of 4.0 ± 0.1 °C at 5C and 4.7 ± 0.1 °C at 8C at the center of the active area, and 3.9 ± 0.1 °C at 5C and 4.0 ± 0.1 °C at 8C at the tab-electrode connection, respectively. This study is intended to contribute to detection of a temperature gradient in real time inside a cell, which can determine possible damage in the battery performance when it operates under normal and abnormal operating conditions, as well as to demonstrate the technical feasibility of the integration of in-operando microsensors inside Li-ion cells.

Experimental study on an FBG strain sensor

Science.gov (United States)

Liu, Hong-lin; Zhu, Zheng-wei; Zheng, Yong; Liu, Bang; Xiao, Feng

2018-01-01

Landslides and other geological disasters occur frequently and often cause high financial and humanitarian cost. The real-time, early-warning monitoring of landslides has important significance in reducing casualties and property losses. In this paper, by taking the high initial precision and high sensitivity advantage of FBG, an FBG strain sensor is designed combining FBGs with inclinometer. The sensor was regarded as a cantilever beam with one end fixed. According to the anisotropic material properties of the inclinometer, a theoretical formula between the FBG wavelength and the deflection of the sensor was established using the elastic mechanics principle. Accuracy of the formula established had been verified through laboratory calibration testing and model slope monitoring experiments. The displacement of landslide could be calculated by the established theoretical formula using the changing values of FBG central wavelength obtained by the demodulation instrument remotely. Results showed that the maximum error at different heights was 9.09%; the average of the maximum error was 6.35%, and its corresponding variance was 2.12; the minimum error was 4.18%; the average of the minimum error was 5.99%, and its corresponding variance was 0.50. The maximum error of the theoretical and the measured displacement decrease gradually, and the variance of the error also decreases gradually. This indicates that the theoretical results are more and more reliable. It also shows that the sensor and the theoretical formula established in this paper can be used for remote, real-time, high precision and early warning monitoring of the slope.

Monitoring Poisson's ratio of glass fiber reinforced composites as damage index using biaxial Fiber Bragg Grating sensors

OpenAIRE

Yılmaz, Çağatay; Yilmaz, Cagatay; Akalın, Çağdaş; Akalin, Cagdas; Kocaman, Esat Selim; Suleman, A.; Yıldız, Mehmet; Yildiz, Mehmet

2016-01-01

Damage accumulation in Glass Fiber Reinforced Polymer (GFRP) composites is monitored based on Poisson's ratio measurements for three different fiber stacking sequences subjected to both quasi-static and quasi-static cyclic tensile loadings. The sensor systems utilized include a dual-extensometer, a biaxial strain gage and a novel embedded-biaxial Fiber Bragg Grating (FBG) sensor. These sensors are used concurrently to measure biaxial strain whereby the evolution of Poisson's ratio as a functi...

Uniform spacing interrogation of a Fourier domain mode-locked fiber Bragg grating sensor system using a polarization-maintaining fiber Sagnac interferometer

Science.gov (United States)

Lee, Hwi Don; Jung, Eun Joo; Jeong, Myung Yung; Chen, Zhongping; Kim, Chang-Seok

2014-01-01

A novel linearized interrogation method is presented for a Fourier domain mode-locked (FDML) fiber Bragg grating (FBG) sensor system. In a high speed regime over several tens of kHz modulations, a sinusoidal wave is available to scan the center wavelength of an FDML wavelength-swept laser, instead of a conventional triangular wave. However, sinusoidal wave modulation suffers from an exaggerated non-uniform wavelength-spacing response in demodulating the time-encoded parameter to the absolute wavelength. In this work, the calibration signal from a polarization-maintaining fiber Sagnac interferometer shares the FDML wavelength-swept laser for FBG sensors to convert the time-encoded FBG signal to the wavelength-encoded uniform-spacing signal. PMID:24489440

Uniform spacing interrogation of a Fourier domain mode-locked fiber Bragg grating sensor system using a polarization-maintaining fiber Sagnac interferometer

International Nuclear Information System (INIS)

Lee, Hwi Don; Jeong, Myung Yung; Chen, Zhongping; Kim, Chang-Seok; Jung, Eun Joo

2013-01-01

A novel linearized interrogation method is presented for a Fourier domain mode-locked (FDML) fiber Bragg grating (FBG) sensor system. In a high speed regime over several tens of kHz modulations, a sinusoidal wave is available to scan the center wavelength of an FDML wavelength-swept laser, instead of a conventional triangular wave. However, sinusoidal wave modulation suffers from an exaggerated non-uniform wavelength-spacing response in demodulating the time-encoded parameter to the absolute wavelength. In this work, the calibration signal from a polarization-maintaining fiber Sagnac interferometer shares the FDML wavelength-swept laser for FBG sensors to convert the time-encoded FBG signal to the wavelength-encoded uniform-spacing signal. (paper)

Uniform spacing interrogation of a Fourier domain mode-locked fiber Bragg grating sensor system using a polarization-maintaining fiber Sagnac interferometer

Science.gov (United States)

Lee, Hwi Don; Jung, Eun Joo; Jeong, Myung Yung; Chen, Zhongping; Kim, Chang-Seok

2013-06-01

A novel linearized interrogation method is presented for a Fourier domain mode-locked (FDML) fiber Bragg grating (FBG) sensor system. In a high speed regime over several tens of kHz modulations, a sinusoidal wave is available to scan the center wavelength of an FDML wavelength-swept laser, instead of a conventional triangular wave. However, sinusoidal wave modulation suffers from an exaggerated non-uniform wavelength-spacing response in demodulating the time-encoded parameter to the absolute wavelength. In this work, the calibration signal from a polarization-maintaining fiber Sagnac interferometer shares the FDML wavelength-swept laser for FBG sensors to convert the time-encoded FBG signal to the wavelength-encoded uniform-spacing signal.

Pd/Ag coated fiber Bragg grating sensor for hydrogen monitoring in power transformers.

Science.gov (United States)

Ma, G M; Jiang, J; Li, C R; Song, H T; Luo, Y T; Wang, H B

2015-04-01

Compared with conventional DGA (dissolved gas analysis) method for on-line monitoring of power transformers, FBG (fiber Bragg grating) hydrogen sensor represents marked advantages over immunity to electromagnetic field, time-saving, and convenience to defect location. Thus, a novel FBG hydrogen sensor based on Pd/Ag (Palladium/Silver) along with polyimide composite film to measure dissolved hydrogen concentration in large power transformers is proposed in this article. With the help of Pd/Ag composite coating, the enhanced performance on mechanical strength and sensitivity is demonstrated, moreover, the response time and sensitivity influenced by oil temperature are solved by correction lines. Sensitivity measurement and temperature calibration of the specific hydrogen sensor have been done respectively in the lab. And experiment results show a high sensitivity of 0.055 pm/(μl/l) with instant response time about 0.4 h under the typical operating temperature of power transformers, which proves a potential utilization inside power transformers to monitor the health status by detecting the dissolved hydrogen concentration.

Optical fiber grating vibration sensor for vibration monitoring of hydraulic pump

Science.gov (United States)

Zhang, Zhengyi; Liu, Chuntong; Li, Hongcai; He, Zhenxin; Zhao, Xiaofeng

2017-06-01

In view of the existing electrical vibration monitoring traditional hydraulic pump vibration sensor, the high false alarm rate is susceptible to electromagnetic interference and is not easy to achieve long-term reliable monitoring, based on the design of a beam of the uniform strength structure of the fiber Bragg grating (FBG) vibration sensor. In this paper, based on the analysis of the vibration theory of the equal strength beam, the principle of FBG vibration tuning based on the equal intensity beam is derived. According to the practical application of the project, the structural dimensions of the equal strength beam are determined, and the optimization design of the vibrator is carried out. The finite element analysis of the sensor is carried out by ANSYS, and the first order resonant frequency is 94.739 Hz. The vibration test of the sensor is carried out by using the vibration frequency of 35 Hz and the vibration source of 50 Hz. The time domain and frequency domain analysis results of test data show that the sensor has good dynamic response characteristics, which can realize the accurate monitoring of the vibration frequency and meet the special requirements of vibration monitoring of hydraulic pump under specific environment.

The Capability of Fiber Bragg Grating Sensors to Measure Amputees’ Trans-Tibial Stump/Socket Interface Pressures

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Faisal Rafiq Mahamd Adikan

2013-08-01

Full Text Available This study presents the first investigation into the capability of fiber Bragg grating (FBG sensors to measure interface pressure between the stump and the prosthetic sockets of a trans-tibial amputee. FBG element(s were recoated with and embedded in a thin layer of epoxy material to form a sensing pad, which was in turn embedded in a silicone polymer material to form a pressure sensor. The sensor was tested in real time by inserting a heavy-duty balloon into the socket and inflating it by using an air compressor. This test was conducted to examine the sensitivity and repeatability of the sensor when subjected to pressure from the stump of the trans-tibial amputee and to mimic the actual environment of the amputee’s Patellar Tendon (PT bar. The sensor exhibited a sensitivity of 127 pm/N and a maximum FSO hysteresis of around ~0.09 in real-time operation. Very good reliability was achieved when the sensor was utilized for in situ measurements. This study may lead to smart FBG-based amputee stump/socket structures for pressure monitoring in amputee socket systems, which will result in better-designed prosthetic sockets that ensure improved patient satisfaction.

Multiplexed FBG Monitoring System for Forecasting Coalmine Water Inrush Disaster

Directory of Open Access Journals (Sweden)

B. Liu

2012-01-01

Full Text Available This paper presents a novel fiber-Bragg-grating- (FBG- based system which can monitor and analyze multiple parameters such as temperature, strain, displacement, and seepage pressure simultaneously for forecasting coalmine water inrush disaster. The sensors have minimum perturbation on the strain field. And the seepage pressure sensors adopt a drawbar structure and employ a corrugated diaphragm to transmit seepage pressure to the axial strain of FBG. The pressure sensitivity is 20.20 pm/KPa, which is 6E3 times higher than that of ordinary bare FBG. The FBG sensors are all preembedded on the roof of mining area in coalmine water inrush model test. Then FBG sensing network is set up applying wavelength-division multiplexing (WDM technology. The experiment is carried out by twelve steps, while the system acquires temperature, strain, displacement, and seepage pressure signals in real time. The results show that strain, displacement, and seepage pressure monitored by the system change significantly before water inrush occurs, and the strain changes firstly. Through signal fusion analyzed it can be concluded that the system provides a novel way to forecast water inrush disaster successfully.

Fiber Bragg Grating Sensor System for Monitoring Smart Composite Aerospace Structures

Science.gov (United States)

Moslehi, Behzad; Black, Richard J.; Gowayed, Yasser

2012-01-01

Lightweight, electromagnetic interference (EMI) immune, fiber-optic, sensor- based structural health monitoring (SHM) will play an increasing role in aerospace structures ranging from aircraft wings to jet engine vanes. Fiber Bragg Grating (FBG) sensors for SHM include advanced signal processing, system and damage identification, and location and quantification algorithms. Potentially, the solution could be developed into an autonomous onboard system to inspect and perform non-destructive evaluation and SHM. A novel method has been developed to massively multiplex FBG sensors, supported by a parallel processing interrogator, which enables high sampling rates combined with highly distributed sensing (up to 96 sensors per system). The interrogation system comprises several subsystems. A broadband optical source subsystem (BOSS) and routing and interface module (RIM) send light from the interrogation system to a composite embedded FBG sensor matrix, which returns measurand-dependent wavelengths back to the interrogation system for measurement with subpicometer resolution. In particular, the returned wavelengths are channeled by the RIM to a photonic signal processing subsystem based on powerful optical chips, then passed through an optoelectronic interface to an analog post-detection electronics subsystem, digital post-detection electronics subsystem, and finally via a data interface to a computer. A range of composite structures has been fabricated with FBGs embedded. Stress tensile, bending, and dynamic strain tests were performed. The experimental work proved that the FBG sensors have a good level of accuracy in measuring the static response of the tested composite coupons (down to submicrostrain levels), the capability to detect and monitor dynamic loads, and the ability to detect defects in composites by a variety of methods including monitoring the decay time under different dynamic loading conditions. In addition to quasi-static and dynamic load monitoring, the

[Monitoring of Crack Propagation in Repaired Structures Based on Characteristics of FBG Sensors Reflecting Spectra].

Science.gov (United States)

Yuan, Shen-fang; Jin, Xin; Qiu, Lei; Huang, Hong-mei

2015-03-01

In order to improve the security of aircraft repaired structures, a method of crack propagation monitoring in repaired structures is put forward basing on characteristics of Fiber Bragg Grating (FBG) reflecting spectra in this article. With the cyclic loading effecting on repaired structure, cracks propagate, while non-uniform strain field appears nearby the tip of crack which leads to the FBG sensors' reflecting spectra deformations. The crack propagating can be monitored by extracting the characteristics of FBG sensors' reflecting spectral deformations. A finite element model (FEM) of the specimen is established. Meanwhile, the distributions of strains which are under the action of cracks of different angles and lengths are obtained. The characteristics, such as main peak wavelength shift, area of reflecting spectra, second and third peak value and so on, are extracted from the FBGs' reflecting spectral which are calculated by transfer matrix algorithm. An artificial neural network is built to act as the model between the characteristics of the reflecting spectral and the propagation of crack. As a result, the crack propagation of repaired structures is monitored accurately and the error of crack length is less than 0.5 mm, the error of crack angle is less than 5 degree. The accurately monitoring problem of crack propagation of repaired structures is solved by taking use of this method. It has important significance in aircrafts safety improvement and maintenance cost reducing.

Bite force measurement based on fiber Bragg grating sensor

Science.gov (United States)

Padma, Srivani; Umesh, Sharath; Asokan, Sundarrajan; Srinivas, Talabattula

2017-10-01

The maximum level of voluntary bite force, which results from the combined action of muscle of mastication, joints, and teeth, i.e., craniomandibular structure, is considered as one of the major indicators for the functional state of the masticatory system. Measurement of voluntary bite force provides useful data for the jaw muscle function and activity along with assessment of prosthetics. This study proposes an in vivo methodology for the dynamic measurement of bite force employing a fiber Bragg grating (FBG) sensor known as bite force measurement device (BFMD). The BFMD developed is a noninvasive intraoral device, which transduces the bite force exerted at the occlusal surface into strain variations on a metal plate. These strain variations are acquired by the FBG sensor bonded over it. The BFMD developed facilitates adjustment of the distance between the biting platform, which is essential to capture the maximum voluntary bite force at three different positions of teeth, namely incisor, premolar, and molar sites. The clinically relevant bite forces are measured at incisor, molar, and premolar position and have been compared against each other. Furthermore, the bite forces measured with all subjects are segregated according to gender and also compared against each other.

Hybrid fiber gratings coated with a catalytic sensitive layer for hydrogen sensing in air.

Science.gov (United States)

Caucheteur, Christophe; Debliquy, Marc; Lahem, Driss; Megret, Patrice

2008-10-13

Using hydrogen as fuel presents a potential risk of explosion and requires low cost and efficient leak sensors. We present here a hybrid sensor configuration consisting of a long period fiber grating (LPFG) and a superimposed uniform fiber Bragg grating (FBG). Both gratings are covered with a sensitive layer made of WO(3) doped with Pt on which H(2) undergoes an exothermic reaction. The released heat increases the temperature around the gratings. In this configuration, the LPFG favors the exothermic reaction thanks to a light coupling to the sensitive layer while the FBG reflects the temperature change linked to the hydrogen concentration. Our sensor is very fast and suitable to detect low hydrogen concentrations in air whatever the relative humidity level and for temperatures down to -50 degrees C, which is without equivalent for other hydrogen optical sensors reported so far.

Fiber Bragg Gratings for High-Temperature Thermal Characterization

International Nuclear Information System (INIS)

Stinson-Bagby, Kelly L.; Fielder, Robert S.

2004-01-01

Fiber Bragg grating (FBG) sensors were used as a characterization tool to study the SAFE-100 thermal simulator at the Nasa Marshal Space Flight Center. The motivation for this work was to support Nasa space nuclear power initiatives through the development of advanced fiber optic sensors for space-based nuclear power applications. Distributed high temperature measurements, up to 1150 deg. C, were made with FBG temperature sensors. Additionally, FBG strain measurements were taken at elevated temperatures to provide a strain profile of the core during operation. This paper will discuss the contribution of these measurements to meet the goals of Nasa Marshall Space Flight Center's Propulsion Research Center. (authors)

Temperature-independent fiber-Bragg-grating-based atmospheric pressure sensor

Science.gov (United States)

Zhang, Zhiguo; Shen, Chunyan; Li, Luming

2018-03-01

Atmospheric pressure is an important way to achieve a high degree of measurement for modern aircrafts, moreover, it is also an indispensable parameter in the meteorological telemetry system. With the development of society, people are increasingly concerned about the weather. Accurate and convenient atmospheric pressure parameters can provide strong support for meteorological analysis. However, electronic atmospheric pressure sensors currently in application suffer from several shortcomings. After an analysis and discussion, we propose an innovative structural design, in which a vacuum membrane box and a temperature-independent strain sensor based on an equal strength cantilever beam structure and fiber Bragg grating (FBG) sensors are used. We provide experimental verification of that the atmospheric pressure sensor device has the characteristics of a simple structure, lack of an external power supply, automatic temperature compensation, and high sensitivity. The sensor system has good sensitivity, which can be up to 100 nm/MPa, and repeatability. In addition, the device exhibits desired hysteresis.

HF-based clad etching of fibre Bragg grating and its utilization in ...

Indian Academy of Sciences (India)

2014-02-09

Feb 9, 2014 ... Abstract. This paper presents a fiber Bragg grating (FBG) based sensor to study the concentration of laser dye in dye–ethanol solution. The FBG used in this experiment is indigenously developed using 255 nm UV radiations from copper vapour laser. The cladding of the FBG was partially removed using ...

Strain Measurement of Steel Roof Truss Using FBG Sensor during Construction of Reverse Shell Shaped Reinforced Concrete Structure

Energy Technology Data Exchange (ETDEWEB)

Lee, Kun Woo [Kyungpook National University, Daegu (Korea, Republic of); Rhim, Hong Chul; Seo, Tae Seok [Yonsei University, Seoul (Korea, Republic of)

2011-08-15

Application of FBG (Fiber Bragg Grating) sensors to measure strain of steel roof trusses has been performed. This is to check and confirm the structural integrity of an unusually shaped, reverse shell structure made of reinforced concrete. The issue was to place sensors at proper location and compare the measured values to the results from structural analysis. It has been learned that a deliberate measurement scheme is needed in order to monitor a complex structure during construction. In this study, the measured values were within allowable range of strain, thus confirming the safety of the structure during measurement and construction.

Novel RF Interrogation of a Fiber Bragg Grating Sensor Using Bidirectional Modulation of a Mach-Zehnder Electro-Optical Modulator

Science.gov (United States)

Choi, Sang-Jin; Mao, Wankai; Pan, Jae-Kyung

2013-01-01

We propose and experimentally demonstrate the novel radio-frequency (RF) interrogation of a fiber Bragg grating (FBG) sensor using bidirectional modulation of a Mach-Zehnder electro-optical modulator (MZ-EOM). Based on the microwave photonic technique and active detection, the transfer function of the proposed system was obtained, and the time delay was calculated from the change in the free spectral range (FSR) at different wavelengths over the optimal measuring range. The results show that the time delay and the wavelength variation have a good linear relationship, with a gradient of 9.31 ps/nm. An actual measurement taken with a sensing FBG for temperature variation shows the relationship with a gradient of 0.93 ps/10 °C. The developed system could be used for FBG temperature or strain sensing and other multiplexed sensor applications. PMID:23820744

A Fiber Bragg grating based tilt sensor suitable for constant temperature room

International Nuclear Information System (INIS)

Tang, Guoyu; Wei, Jue; Zhou, Wei; Wu, Mingyu; Yang, Meichao; Xie, Ruijun; Xu, Xiaofeng

2015-01-01

Constant-temperature rooms have been widely used in industrial production, quality testing, and research laboratories. This paper proposes a high-precision tilt sensor suitable for a constant- temperature room, which has achieved a wide-range power change while the fiber Bragg grating (FBG) reflection peak wavelength shifted very little, thereby demonstrating a novel method for obtaining a high-precision tilt sensor. This paper also studies the effect of the reflection peak on measurement precision. The proposed sensor can distinguish the direction of tilt with an excellent sensitivity of 403 dBm/° and a highest achievable resolution of 2.481 × 10 −5 ° (that is, 0.08% of the measuring range). (paper)

Wearable sensors in intelligent clothing for measuring human body temperature based on optical fiber Bragg grating.

Science.gov (United States)

Li, Hongqiang; Yang, Haijing; Li, Enbang; Liu, Zhihui; Wei, Kejia

2012-05-21

Measuring body temperature is considerably important to physiological studies as well as clinical investigations. In recent years, numerous observations have been reported and various methods of measurement have been employed. The present paper introduces a novel wearable sensor in intelligent clothing for human body temperature measurement. The objective is the integration of optical fiber Bragg grating (FBG)-based sensors into functional textiles to extend the capabilities of wearable solutions for body temperature monitoring. In addition, the temperature sensitivity is 150 pm/°C, which is almost 15 times higher than that of a bare FBG. This study combines large and small pipes during fabrication to implant FBG sensors into the fabric. The law of energy conservation of the human body is considered in determining heat transfer between the body and its clothing. The mathematical model of heat transmission between the body and clothed FBG sensors is studied, and the steady-state thermal analysis is presented. The simulation results show the capability of the material to correct the actual body temperature. Based on the skin temperature obtained by the weighted average method, this paper presents the five points weighted coefficients model using both sides of the chest, armpits, and the upper back for the intelligent clothing. The weighted coefficients of 0.0826 for the left chest, 0.3706 for the left armpit, 0.3706 for the right armpit, 0.0936 for the upper back, and 0.0826 for the right chest were obtained using Cramer's Rule. Using the weighting coefficient, the deviation of the experimental result was ± 0.18 °C, which favors the use for clinical armpit temperature monitoring. Moreover, in special cases when several FBG sensors are broken, the weighted coefficients of the other sensors could be changed to obtain accurate body temperature.

Simultaneous measurement of refractive index and temperature based on intensity demodulation using matching grating method.

Science.gov (United States)

Qi, Liang; Zhao, Chun-Liu; Kang, Juan; Jin, Yongxing; Wang, Jianfeng; Ye, Manping; Jin, Shangzhong

2013-07-01

A solution refractive index (SRI) and temperature simultaneous measurement sensor with intensity-demodulation system based on matching grating method were demonstrated. Long period grating written in a photonic crystal fiber (LPG-PCF), provides temperature stable and wavelength dependent optical intensity transmission. The reflective peaks of two fiber Bragg gratings (FBGs), one of which is etched then sensitive to both SRI and temperature, another (FBG2) is only sensitive to temperature, were located in the same linear range of the LPG-PCF's transmission spectrum. An identical FBG with FBG2 was chosen as a matching FBG. When environments (SRI and temperature) change, the wavelength shifts of the FBGs are translated effectively to the reflection intensity changes. By monitoring output lights of unmatching and matching paths, the SRI and temperature were deduced by a signal processing unit. Experimental results show that the simultaneous refractive index and temperature measurement system work well. The proposed sensor system is compact and suitable for in situ applications at lower cost.

Long fiber Bragg grating sensor interrogation using discrete-time microwave photonic filtering techniques.

Science.gov (United States)

Ricchiuti, Amelia Lavinia; Barrera, David; Sales, Salvador; Thevenaz, Luc; Capmany, José

2013-11-18

A novel technique for interrogating photonic sensors based on long fiber Bragg gratings (FBGs) is presented and experimentally demonstrated, dedicated to detect the presence and the precise location of several spot events. The principle of operation is based on a technique used to analyze microwave photonics (MWP) filters. The long FBGs are used as quasi-distributed sensors. Several hot-spots can be detected along the FBG with a spatial accuracy under 0.5 mm using a modulator and a photo-detector (PD) with a modest bandwidth of less than 1 GHz. The proposed interrogation system is intrinsically robust against environmental changes.

An adaptive wing for a small-aircraft application with a configuration of fibre Bragg grating sensors

International Nuclear Information System (INIS)

Mieloszyk, M; Krawczuk, M; Zak, A; Ostachowicz, W

2010-01-01

In this paper a concept of an adaptive wing for small-aircraft applications with an array of fibre Bragg grating (FBG) sensors has been presented and discussed. In this concept the shape of the wing can be controlled and altered thanks to the wing design and the use of integrated shape memory alloy actuators. The concept has been tested numerically by the use of the finite element method. For numerical calculations the commercial finite element package ABAQUS ® has been employed. A finite element model of the wing has been prepared in order to estimate the values of the wing twisting angles and distributions of the twist for various activation scenarios. Based on the results of numerical analysis the locations and numbers of the FBG sensors have also been determined. The results of numerical calculations obtained by the authors confirmed the usefulness of the assumed wing control strategy. Based on them and the concept developed of the adaptive wing, a wing demonstration stand has been designed and built. The stand has been used to verify experimentally the performance of the adaptive wing and the usefulness of the FBG sensors for evaluation of the wing condition

Dynamic Strain Measurements on Automotive and Aeronautic Composite Components by Means of Embedded Fiber Bragg Grating Sensors

Directory of Open Access Journals (Sweden)

Alfredo Lamberti

2015-10-01

Full Text Available The measurement of the internal deformations occurring in real-life composite components is a very challenging task, especially for those components that are rather difficult to access. Optical fiber sensors can overcome such a problem, since they can be embedded in the composite materials and serve as in situ sensors. In this article, embedded optical fiber Bragg grating (FBG sensors are used to analyze the vibration characteristics of two real-life composite components. The first component is a carbon fiber-reinforced polymer automotive control arm; the second is a glass fiber-reinforced polymer aeronautic hinge arm. The modal parameters of both components were estimated by processing the FBG signals with two interrogation techniques: the maximum detection and fast phase correlation algorithms were employed for the demodulation of the FBG signals; the Peak-Picking and PolyMax techniques were instead used for the parameter estimation. To validate the FBG outcomes, reference measurements were performed by means of a laser Doppler vibrometer. Sensors 2015, 15 27175 The analysis of the results showed that the FBG sensing capabilities were enhanced when the recently-introduced fast phase correlation algorithm was combined with the state-of-the-art PolyMax estimator curve fitting method. In this case, the FBGs provided the most accurate results, i.e. it was possible to fully characterize the vibration behavior of both composite components. When using more traditional interrogation algorithms (maximum detection and modal parameter estimation techniques (Peak-Picking, some of the modes were not successfully identified.

Simulation and Experimental Investigations on the Strain Measurement of the Uniform Strength Beam Using a FBG sensor

International Nuclear Information System (INIS)

Tu Yumeng; Gong Huaping; Chen Jixuan; Jin Yongxing

2011-01-01

The model of force analysis on a uniform strength beam is built by the general finite element program (ANSYS software). The flexivity profile produced by uniform strength beam with different forces is simulated by ANSYS software. In experiment, a fiber Bragg grating sensor is fixed on the uniform strength beam with modified acrylate. The flexivity and strain are varied by changing the load on the end of the beam. The strain of the uniform strength beam is measured with FBG when applied force is varied from 2.45N to14.7N with a step of 2.45N. Both the simulated and experimental results show that, the strain induced by the uniform strength beam is linear with the load force. The sensitivity is 18.32με/N for experimental measurement, and 19.72με/N for simulation. The experimental results are consistent with the simulation results, with the maximum measurement error of strain being 7.4%. It indicates that, the FBG sensor fixed with modified acrylate is proved to be effectively and reliably in the applications of civil engineering.

A Robust Fiber Bragg Grating Hydrogen Gas Sensor Using Platinum-Supported Silica Catalyst Film

OpenAIRE

Marina Kurohiji; Seiji Ichiriyama; Naoki Yamasaku; Shinji Okazaki; Naoya Kasai; Yusuke Maru; Tadahito Mizutani

2018-01-01

A robust fiber Bragg grating (FBG) hydrogen gas sensor for reliable multipoint-leakage monitoring has been developed. The sensing mechanism is based on shifts of center wavelength of the reflection spectra due to temperature change caused by catalytic combustion heat. The sensitive film which consists of platinum-supported silica (Pt/SiO2) catalyst film was obtained using sol-gel method. The precursor solution was composed of hexachloroplatinic acid and commercially available silica precursor...

Model Study of the Influence of Ambient Temperature and Installation Types on Surface Temperature Measurement by Using a Fiber Bragg Grating Sensor

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Yi Liu

2016-07-01

Full Text Available Surface temperature is an important parameter in clinical diagnosis, equipment state control, and environmental monitoring fields. The Fiber Bragg Grating (FBG temperature sensor possesses numerous significant advantages over conventional electrical sensors, thus it is an ideal choice to achieve high-accuracy surface temperature measurements. However, the effects of the ambient temperature and installation types on the measurement of surface temperature are often overlooked. A theoretical analysis is implemented and a thermal transfer model of a surface FBG sensor is established. The theoretical and simulated analysis shows that both substrate strain and the temperature difference between the fiber core and hot surface are the most important factors which affect measurement accuracy. A surface-type temperature standard setup is proposed to study the measurement error of the FBG temperature sensor. Experimental results show that there are two effects influencing measurement results. One is the “gradient effect”. This results in a positive linear error with increasing surface temperature. Another is the “substrate effect”. This results in a negative non-linear error with increasing surface temperature. The measurement error of the FBG sensor with single-ended fixation are determined by the gradient effect and is a linear error. It is not influenced by substrate expansion. Thus, it can be compensated easily. The measurement errors of the FBG sensor with double-ended fixation are determined by the two effects and the substrate effect is dominant. The measurement error change trend of the FBG sensor with fully-adhered fixation is similar to that with double-ended fixation. The adhesive layer can reduce the two effects and measurement error. The fully-adhered fixation has lower error, however, it is easily affected by substrate strain. Due to its linear error and strain-resistant characteristics, the single-ended fixation will play an

Model Study of the Influence of Ambient Temperature and Installation Types on Surface Temperature Measurement by Using a Fiber Bragg Grating Sensor.

Science.gov (United States)

Liu, Yi; Zhang, Jun

2016-07-01

Surface temperature is an important parameter in clinical diagnosis, equipment state control, and environmental monitoring fields. The Fiber Bragg Grating (FBG) temperature sensor possesses numerous significant advantages over conventional electrical sensors, thus it is an ideal choice to achieve high-accuracy surface temperature measurements. However, the effects of the ambient temperature and installation types on the measurement of surface temperature are often overlooked. A theoretical analysis is implemented and a thermal transfer model of a surface FBG sensor is established. The theoretical and simulated analysis shows that both substrate strain and the temperature difference between the fiber core and hot surface are the most important factors which affect measurement accuracy. A surface-type temperature standard setup is proposed to study the measurement error of the FBG temperature sensor. Experimental results show that there are two effects influencing measurement results. One is the "gradient effect". This results in a positive linear error with increasing surface temperature. Another is the "substrate effect". This results in a negative non-linear error with increasing surface temperature. The measurement error of the FBG sensor with single-ended fixation are determined by the gradient effect and is a linear error. It is not influenced by substrate expansion. Thus, it can be compensated easily. The measurement errors of the FBG sensor with double-ended fixation are determined by the two effects and the substrate effect is dominant. The measurement error change trend of the FBG sensor with fully-adhered fixation is similar to that with double-ended fixation. The adhesive layer can reduce the two effects and measurement error. The fully-adhered fixation has lower error, however, it is easily affected by substrate strain. Due to its linear error and strain-resistant characteristics, the single-ended fixation will play an important role in the FBG sensor

Embedded fiber Bragg grating sensors for true temperature monitoring in Nb3Sn superconducting magnets for high energy physics

Science.gov (United States)

Chiuchiolo, A.; Bajas, H.; Bajko, M.; Consales, M.; Giordano, M.; Perez, J. C.; Cusano, A.

2016-05-01

The luminosity upgrade of the Large Hadron Collider (HL-LHC) planned at the European Organization for Nuclear Research (CERN) requires the development of a new generation of superconducting magnets based on Nb3Sn technology. The instrumentation required for the racetrack coils needs the development of reliable sensing systems able to monitor the magnet thermo-mechanical behavior during its service life, from the coil fabrication to the magnet operation. With this purpose, Fiber Bragg Grating (FBG) sensors have been embedded in the coils of the Short Model Coil (SMC) magnet fabricated at CERN. The FBG sensitivity to both temperature and strain required the development of a solution able to separate mechanical and temperature effects. This work presents for the first time a feasibility study devoted to the implementation of an embedded FBG sensor for the measurement of the "true" temperature in the impregnated Nb3Sn coil during the fabrication process.

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

Directory of Open Access Journals (Sweden)

R. Brian Jenkins

2017-01-01

Full Text Available 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.

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

Science.gov (United States)

Jenkins, R Brian; Joyce, Peter; Mechtel, Deborah

2017-01-27

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.

Fiber Bragg Grating Based System for Temperature Measurements

Science.gov (United States)

Tahir, Bashir Ahmed; Ali, Jalil; Abdul Rahman, Rosly

In this study, a fiber Bragg grating sensor for temperature measurement is proposed and experimentally demonstrated. In particular, we point out that the method is well-suited for monitoring temperature because they are able to withstand a high temperature environment, where standard thermocouple methods fail. The interrogation technologies of the sensor systems are all simple, low cost and effective as well. In the sensor system, fiber grating was dipped into a water beaker that was placed on a hotplate to control the temperature of water. The temperature was raised in equal increments. The sensing principle is based on tracking of Bragg wavelength shifts caused by the temperature change. So the temperature is measured based on the wavelength-shifts of the FBG induced by the heating water. The fiber grating is high temperature stable excimer-laser-induced grating and has a linear function of wavelength-temperature in the range of 0-285°C. A dynamic range of 0-285°C and a sensitivity of 0.0131 nm/°C almost equal to that of general FBG have been obtained by this sensor system. Furthermore, the correlation of theoretical analysis and experimental results show the capability and feasibility of the purposed technique.

Novel method of dual fiber Bragg gratings integrated in fiber ring laser for biochemical sensors

Science.gov (United States)

Bui, H.; Pham, T. B.; Nguyen, V. A.; Pham, V. D.; Do, T. C.; Nguyen, T. V.; Hoang, T. H. C.; Le, H. T.; Pham, V. H.

2018-05-01

Optical sensors have been shown to be very effective for measuring the toxic content in liquid and air environments. Optical sensors, which operate based on the wavelength shift of the optical signals, require an expensive spectrometer. In this paper, we propose a new configuration of the optical sensor device for measuring wavelength shift without using a spectrometer. This configuration has a large potential for application in biochemical sensing techniques, and comes with a low cost. This configuration uses dual fiber Bragg gratings (FBGs) integrated in a fiber ring laser structure of erbium-doped fiber, in which one FBG is used as a reference to sweep over the applicable spectrum of the etched-Bragg grating. The etched-FBG as a sensing probe is suitable for bio- and/or chemical sensors. The sensitivity and accuracy of the sensor system can be improved by the narrow linewidth of emission spectra from the laser, the best limit of detection of this sensor is 1.5  ×  10‑4 RIU (RIU: refractive index unit), as achieved by the optical sensor using a high resolution spectrometer. This sensor system has been experimentally investigated to detect different types of organic compounds, gasoline, mixing ratios of organic solvents in gasoline, and nitrate concentration in water samples. The experimental results show that this sensing method could determine different mixing ratios of organic solvents with good repeatability, high accuracy, and rapid response: e.g. for ethanol and/or methanol in gasoline RON 92 (RON: research octane number) of 0%–14% v/v, and nitrate in water samples at a low concentration range of 0–50 ppm. These results suggest that the proposed configuration can construct low-cost and accurate biochemical sensors.

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

Science.gov (United States)

Sun, Yijie; Xu, Hongzhong; Gu, Peng; Hu, Wenjie

2017-03-15

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.

Strain and displacement controls by fibre bragg grating and digital image correlation

DEFF Research Database (Denmark)

Waldbjørn, Jacob Paamand; Høgh, Jacob Herold; Schmidt, Jacob Wittrup

2014-01-01

the test based on measurements performed directly on the test specimen. In this paper, fibre Bragg grating (FBG) and Digital Image Correlation (DIC) are used to control a test. The FBG sensors offer the possibility of measuring strains inside the specimen, while the DIC system measures strains...

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

Directory of Open Access Journals (Sweden)

Li-Yang Shao

2016-12-01

Full Text Available 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%.

Sensitivity Enhancement for Fiber Bragg Grating Sensors by Four Wave Mixing

Directory of Open Access Journals (Sweden)

Jiangbing Du

2015-04-01

Full Text Available All-optical signal processing based on four wave mixing (FWM in a highly nonlinear fiber (HNLF to enhance the sensitivity of a fiber sensor is demonstrated and comprehensively reviewed in this paper. The principle is based on the frequency chirp magnification (FCM by FWM. Degenerated FWM, cascaded two-stage FWM and pump-pulsed FWM with optical parametric amplification (OPA are experimentally utilized for magnifying the frequency chirp. By using the pump pulse modulation to increase the peak power, OPA can be induced with the use of a dispersion-optimized HNLF. Therefore, ultra-highly efficient FWM can be realized due to the high peak power and OPA. By using the fiber Bragg grating (FBG laser as the FWM pump, the wavelength drift of the FBG can thus be magnified due to the FCM. We obtain a sensing performance of 13.3 pm/με strain sensitivity and 141.2 pm/°C temperature sensitivity for a conventional FBG, which has an intrinsic strain sensitivity of only ~1 pm/με and an intrinsic temperature sensitivity of only ~10 pm/°C, respectively.

Embedded fiber Bragg grating sensors for true temperature monitoring in Nb$_3$Sn superconducting magnets for high energy physics

CERN Document Server

Chiuchiolo, A; Bajko, M; Consales, M; Giordano, M; Perez, J C; Cusano, A

2016-01-01

The luminosity upgrade of the Large Hadron Collider (HL-LHC) planned at the European Organization for Nuclear Research (CERN) requires the development of a new generation of superconducting magnets based on Nb$_{3}$Sn technology. The instrumentation required for the racetrack coils needs the development of reliable sensing systems able to monitor the magnet thermo-mechanical behavior during its service life, from the coil fabrication to the magnet operation. With this purpose, Fiber Bragg Grating (FBG) sensors have been embedded in the coils of the Short Model Coil (SMC) magnet fabricated at CERN. The FBG sensitivity to both temperature and strain required the development of a solution able to separate mechanical and temperature effects. This work presents for the first time a feasibility study devoted to the implementation of an embedded FBG sensor for the measurement of the "true" temperature in the impregnated Nb$_{3}$Sn coil during the fabrication process. © (2016) COPYRIGHT Society of Photo-Optical Inst...

Strain measurements using Fiber Bragg Grating sensors in Structural Health Monitoring

Directory of Open Access Journals (Sweden)

Daniela ENCIU

2017-06-01

Full Text Available The paper presents some results obtained within a project of the “NUCLEU” Program financed by the Ministry of Research and Innovation-ANCS. The project supposes, among others, the design and the realization of a demonstrator for strain and stress measurements made with Fiber Bragg Gratings optical sensors. The paper details the construction of the demonstrator. The strain measurements induced in a cantilevered aluminum plate are compared with the analytical values provided by a mathematical model, and with the numerical values obtained by FEM analysis. The consistency of these comparative data indicates the achievement within the project of a level of competence necessary for later use of FBG sensors in the applicative researches involving the aerospace structures monitoring.

Simulation and analysis of sensitivity for tapered fiber Bragg grating evanescent wave sensor

Science.gov (United States)

Xu, Hong-zhi; Lou, Jun; Tan, Yao-cheng; Li, Ben-chong; Huang, Jie; Shen, Wei-min

2014-12-01

We have carried out a detailed simulative study of the tapered fiber Bragg grating (TFBG) evanescent wave sensor sensitivity by using 3-D Coupled-Mode Theory method. The method is based on the spectral interrogation mode of operation. We also make numerical simulations to figure out how the uniform waist diameter and the difference of the relative refractive indexes between fiber core and external medium affect the sensitivity of this proposed sensor. The simulation results show that the sensitivity of the tapered fiber Bragg grating will be improved when the diameter of the uniform waist decrease as well as the difference of the relative refractive indexes between fiber core and external medium. And with the fixed uniform waist diameter and tapered length, when the difference of the relative refractive index of fiber core and external medium varies is 0.015RIU, the values of wavelength shift is 5.08nm, the sensitivity of the tapered fiber Bragg grating is 317.5nm/RIU. The sensitivity is higher than that of the common FBG. The results are consistent with theoretical models. The simulation results can supply the guidance for the further experimental study and refractive index sensor design, optimization and application.

Optical Sensor of Thermal Gas Flow Based on Fiber Bragg Grating

Directory of Open Access Journals (Sweden)

Xu Jiang

2017-02-01

Full Text Available 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.

Development of an experimentally supported evaluation method for optimization and characterization of strain transfer of surface-applied Fibre Bragg Gratings (FBG); Entwicklung eines experimentell gestuetzten Bewertungsverfahrens zur Optimierung und Charakterisierung der Dehnungsuebertragung oberflaechenapplizierter Faser-Bragg-Gitter-Sensoren

Energy Technology Data Exchange (ETDEWEB)

Schlueter, Vivien Gisela

2010-05-01

Fibre Bragg Gratings (FBG) as strain sensors are implemented in those areas, where conventional electrical strain gauges reach their limits (for example in areas of high voltage, strong electro-magnetic fields, medical technology, safety relevant and radiation-exposed areas). Subject of this work is the surface application and the qualification of these sensors as strain sensors on different materials. A certified and proven method of application for surface mounted sensors is not known yet. The determination of the strain transfer and the definition of a strain transfer factor out of the relation between the Bragg wavelength change and the strain of the specimen have not yet been validated experimentally with an independent validation method. The development of an experimental methodology using a physically independent optical reference method for the determination of the strain transfer between the specimen and the FBG strain sensor is the main focus of this work. The influencing parameters on the strain distribution have been quantified experimentally and the change in Bragg wavelength has been investigated in relation to the strain measured by strain gauges. The material properties of the adhesives have been partly investigated. On the basis of these experiments a testing facility for surface applied FBG strain sensors has been developed. The functionality of the experimental methodology for the determination of the strain factor has been shown. The characterisation of the testing facility and the validity of FBG strain sensors through the experimental methodology inhere developed have been started. For the case of the strain determination in wind turbine rotor blades specially adapted FBG patches have been developed and qualified. An integration technique for FBG strain sensors into the rotor blade has been developed as well. As a first step of standardizing this measurement technique a national standard has been developed under the contribution of the author

Strain features and condition assessment of orthotropic steel deck cable-supported bridges subjected to vehicle loads by using dense FBG strain sensors

Science.gov (United States)

Wei, Shiyin; Zhang, Zhaohui; Li, Shunlong; Li, Hui

2017-10-01

Strain is a direct indicator of structural safety. Therefore, strain sensors have been used in most structural health monitoring systems for bridges. However, until now, the investigation of strain response has been insufficient. This paper conducts a comprehensive study of the strain features of the U ribs and transverse diaphragm on an orthotropic steel deck and proposes a statistical paradigm for crack detection based on the features of vehicle-induced strain response by using the densely distributed optic fibre Bragg grating (FBG) strain sensors. The local feature of strain under vehicle load is highlighted, which enables the use of measurement data to determine the vehicle loading event and to make a decision regarding the health status of a girder near the strain sensors via technical elimination of the load information. Time-frequency analysis shows that the strain contains three features: the long-term trend item, the short-term trend item, and the instantaneous vehicle-induced item (IVII). The IVII is the wheel-induced strain with a remarkable local feature, and the measured wheel-induced strain is only influenced by the vehicle near the FBG sensor, while other vehicles slightly farther away have no effect on the wheel-induced strain. This causes the local strain series, among the FBG strain sensors in the same transverse locations of different cross-sections, to present similarities in shape to some extent and presents a time delay in successive order along the driving direction. Therefore, the strain series induced by an identical vehicle can be easily tracked and compared by extracting the amplitude and calculating the mutual ratio to eliminate vehicle loading information, leaving the girder information alone. The statistical paradigm for crack detection is finally proposed, and the detection accuracy is then validated by using dense FBG strain sensors on a long-span suspension bridge in China.

Fabrication and characterization of metal-packaged fiber Bragg grating sensor by one-step ultrasonic welding

Science.gov (United States)

Zhang, Yumin; Zhu, Lianqing; Luo, Fei; Dong, Mingli; Ding, Xiangdong; He, Wei

2016-06-01

A metallic packaging technique of fiber Bragg grating (FBG) sensors is developed for measurement of strain and temperature, and it can be simply achieved via one-step ultrasonic welding. The average strain transfer rate of the metal-packaged sensor is theoretically evaluated by a proposed model aiming at surface-bonded metallic packaging FBG. According to analytical results, the metallic packaging shows higher average strain transfer rate compared with traditional adhesive packaging under the same packaging conditions. Strain tests are performed on an elaborate uniform strength beam for both tensile and compressive strains; strain sensitivities of approximately 1.16 and 1.30 pm/μɛ are obtained for the tensile and compressive situations, respectively. Temperature rising and cooling tests are also executed from 50°C to 200°C, and the sensitivity of temperature is 36.59 pm/°C. All the measurements of strain and temperature exhibit good linearity and stability. These results demonstrate that the metal-packaged sensors can be successfully fabricated by one-step welding technique and provide great promise for long-term and high-precision structural health monitoring.

Structural health monitoring method for wind turbine trailing edge: Crack growth detection using Fibre Bragg Grating sensor embedded in composite materials

DEFF Research Database (Denmark)

Pereira, Gilmar Ferreira; Mikkelsen, Lars Pilgaard; McGugan, Malcolm

2015-01-01

In this article a novel method to assess a crack growing/damage event in composite material using Fibre Bragg Grating (FBG) sensors embedded in a host material and its application into a composite material structure, Wind Turbine Trailing Edge, is presented. A Structure-Material-FBG model......, such as compression fields ahead the crack or non-uniform strain fields, and then identify the presence of such damage in the structure. Experimental tests were conducted to fully characterize this concept and support the model. Double Cantilever Beams (DCB), made with two glass fibre beams glued with structural...

WE-AB-BRA-10: Assessment of Fiber Bragg Grating (FBG)-Based Sensing for Real-Time Needle Tracking During MR-Guided Brachytherapy

International Nuclear Information System (INIS)

Borot de Battisti, M; Maenhout, M; Lagendijk, J J W; Van Vulpen, M; Moerland, M A; Denis de Senneville, B; Hautvast, G; Binnekamp, D

2016-01-01

Purpose: This study assesses the potential of Fiber Bragg Grating (FBG)-based sensing for real-time needle (including catheter or tube) tracking during MR-guided HDR brachytherapy. Methods: The proposed FBG-based sensing tracking approach involves a MR-compatible stylet composed of three optic fibers with nine sets of embedded FBG sensors each. When the stylet is inserted inside the lumen of the needle, the FBG sensing system can measure the needle’s deflection. For localization of the needle in physical space, the position and orientation of the stylet base are mandatory. For this purpose, we propose to fix the stylet base and determine its position and orientation using a MR-based calibration as follows. First, the deflection of a needle inserted in a phantom in two different configurations is measured during simultaneous MR-imaging. Then, after segmentation of the needle shapes on the MR-images, the position and orientation of the stylet base is determined using a rigid registration of the needle shapes on both MR and FBG-based measurements. The calibration method was assessed by measuring the deflection of a needle in a prostate phantom in five different configurations using FBG-based sensing during simultaneous MR-imaging. Any two needle shapes were employed for the calibration step and the proposed FGB-tracking approach was subsequently evaluated on the other three needles configurations. The tracking accuracy was evaluated by computing the Euclidian distance between the 3D FBG vs. MR-based measurements. Results: Over all needle shapes tested, the average(standard deviation) Euclidian distance between the FBG and MR-based measurements was 0.79mm(0.37mm). The update rate and latency of the FBG-based measurements were 100ms and 300ms respectively. Conclusion: The proposed FBG-based protocol can measure the needle position with an accuracy, precision, update rate and latency eligible for accurate needle steering during MR-guided HDR brachytherapy. M. Borot de

Flextensional fiber Bragg grating-based accelerometer for low frequency vibration measurement

Institute of Scientific and Technical Information of China (English)

Jinghua Zhang; Xueguang Qiao; Manli Hu; Zhongyao Feng; Hong Gao; Yang Yang; Rui Zhou

2011-01-01

@@ The intelligent structural health monitoring method,which uses a fiber Bragg grating(FBG)sensor,is a new approach in the field of civil engineering.However,it lacks a reliable FBG-based accelerometer for taking structural low frequency vibration measurements.In this letter,a flextensional FBG-based accelerometer is proposed and demonstrated.The experimental results indicate that the natural frequency of the developed accelerometer is 16.7 Hz,with a high sensitivity of 410.7 pm/g.In addition,it has a broad and flat response over low frequencies ranging from 1 to 10 Hz.The natural frequency and sensitivity of the accelerometer can be tuned by adding mass to tailor the sensor performance to specific applications.Experimental results are presented to demonstrate the good performance of the proposed FBG-based accelerometer.These results show that the proposed accelerometer is satisfactory for low frequency vibration measurements.%The intelligent structural health monitoring method, which uses a fiber Bragg grating {FBG} sensor, ie a new approach in the field of civil engineering. However, it lacks a reliable FBG-based accelerometer for taking structural low frequency vibration measurements. In this letter, a flextensional FBG-based accelerometer is proposed and demonstrated. The experimental results indicate that the natural frequency of the developed accelerometer is 16.7 Hz, with a high sensitivity of 410.7 pm/g. In addition, it has a broad and flat response over low frequencies ranging from 1 to 10 Hz. The natural frequency and sensitivity of the accelerometer can be tuned by adding mass to tailor the sensor performance to specific applications. Experimental results are presented to demonstrate the good performance of the proposed FBG-based accelerometer. These results show that the proposed accelerometer is satisfactory for low frequency vibration measurements.

An intelligent service matching method for mechanical equipment condition monitoring using the fibre Bragg grating sensor network

Science.gov (United States)

Zhang, Fan; Zhou, Zude; Liu, Quan; Xu, Wenjun

2017-02-01

Due to the advantages of being able to function under harsh environmental conditions and serving as a distributed condition information source in a networked monitoring system, the fibre Bragg grating (FBG) sensor network has attracted considerable attention for equipment online condition monitoring. To provide an overall conditional view of the mechanical equipment operation, a networked service-oriented condition monitoring framework based on FBG sensing is proposed, together with an intelligent matching method for supporting monitoring service management. In the novel framework, three classes of progressive service matching approaches, including service-chain knowledge database service matching, multi-objective constrained service matching and workflow-driven human-interactive service matching, are developed and integrated with an enhanced particle swarm optimisation (PSO) algorithm as well as a workflow-driven mechanism. Moreover, the manufacturing domain ontology, FBG sensor network structure and monitoring object are considered to facilitate the automatic matching of condition monitoring services to overcome the limitations of traditional service processing methods. The experimental results demonstrate that FBG monitoring services can be selected intelligently, and the developed condition monitoring system can be re-built rapidly as new equipment joins the framework. The effectiveness of the service matching method is also verified by implementing a prototype system together with its performance analysis.

An application of neural network for Structural Health Monitoring of an adaptive wing with an array of FBG sensors

International Nuclear Information System (INIS)

Mieloszyk, Magdalena; Skarbek, Lukasz; Ostachowicz, Wieslaw; Krawczuk, Marek

2011-01-01

This paper presents an application of neural networks to determinate the level of activation of shape memory alloy actuators of an adaptive wing. In this concept the shape of the wing can be controlled and altered thanks to the wing design and the use of integrated shape memory alloy actuators. The wing is assumed as assembled from a number of wing sections that relative positions can be controlled independently by thermal activation of shape memory actuators. The investigated wing is employed with an array of Fibre Bragg Grating sensors. The Fibre Bragg Grating sensors with combination of a neural network have been used to Structural Health Monitoring of the wing condition. The FBG sensors are a great tool to control the condition of composite structures due to their immunity to electromagnetic fields as well as their small size and weight. They can be mounted onto the surface or embedded into the wing composite material without any significant influence on the wing strength. The paper concentrates on analysis of the determination of the twisting moment produced by an activated shape memory alloy actuator. This has been analysed both numerically using the finite element method by a commercial code ABAQUS (registered) and experimentally using Fibre Bragg Grating sensor measurements. The results of the analysis have been then used by a neural network to determine twisting moments produced by each shape memory alloy actuator.

Design and analysis of FBG based sensor for detection of damage in oil and gas pipelines for safety of marine life

Science.gov (United States)

Bedi, Amna; Kothari, Vaishali; Kumar, Santosh

2018-02-01

The under laid gas and oil pipelines on the seafloor are prone to various disturbances like seismic movements of the sea bed, oceanic currents, tsunamis. These factors tend to damage such pipelines connecting different locations of the world dependent on these pipelines for their day-to-day use of oil and natural gas. If damaged, the oil spills in the water bodies cause grave loss to marine life along with serious economic issues. It is not feasible to monitor the undersea pipelines manually because of the huge seafloor depth. For timely detection of such damage, a new technique using optical Fiber Bragg grating (FBG) sensors and its installation has been given in this work. The idea of an FBG sensor for detecting damage in pipeline structure based on the acoustic emission has been worked out. The numerical calculation has been done based on the fundamental of strain measurement and the output has been simulated using MATLAB.

Development of optical FBG force measurement system for the medical application

Science.gov (United States)

Song, Hoseok; Kim, Kiyoung; Suh, Jungwook; Lee, Jungju

2010-03-01

Haptic feedback plays a very important role in medical surgery. In minimally invasive surgery (MIS), however, very long and stiff bar of instruments take haptic feeling away from the surgeon. In minimally invasive robotic surgery (MIRS), moreover, haptic feelings are totally eliminated. Previous researchers have reported that the absence of force feedback increased the average force magnitude applied to the tissue by at least 50%, and increased the peakforce magnitude by at least a factor of two. Therefore, it is very important to provide haptic information in MIRS. Recently, many sensors are being developed for MIS or MIRS, but they have some obstacles in their application to real situations of medical surgery. The most critical problems are size limit and sterilizability. Optical fiber sensors are one of the most suitable sensors for this environment. Especially, optical fiber Bragg grating (FBG) sensor has one additional advantage than the other optical fiber sensors. FBG sensor is not influenced by intensity of light source. In this paper, we would like to present the initial results of study on the application of the FBG sensor to measure reflected forces in MIRS environments and then suggest the possibility of successful application to the MIRS systems.

High speed and high resolution interrogation of a fiber Bragg grating sensor based on microwave photonic filtering and chirped microwave pulse compression.

Science.gov (United States)

Xu, Ou; Zhang, Jiejun; Yao, Jianping

2016-11-01

High speed and high resolution interrogation of a fiber Bragg grating (FBG) sensor based on microwave photonic filtering and chirped microwave pulse compression is proposed and experimentally demonstrated. In the proposed sensor, a broadband linearly chirped microwave waveform (LCMW) is applied to a single-passband microwave photonic filter (MPF) which is implemented based on phase modulation and phase modulation to intensity modulation conversion using a phase modulator (PM) and a phase-shifted FBG (PS-FBG). Since the center frequency of the MPF is a function of the central wavelength of the PS-FBG, when the PS-FBG experiences a strain or temperature change, the wavelength is shifted, which leads to the change in the center frequency of the MPF. At the output of the MPF, a filtered chirped waveform with the center frequency corresponding to the applied strain or temperature is obtained. By compressing the filtered LCMW in a digital signal processor, the resolution is improved. The proposed interrogation technique is experimentally demonstrated. The experimental results show that interrogation sensitivity and resolution as high as 1.25 ns/με and 0.8 με are achieved.

In-vivo determination of chewing patterns using FBG and artificial neural networks

Science.gov (United States)

Pegorini, Vinicius; Zen Karam, Leandro; Rocha Pitta, Christiano S.; Ribeiro, Richardson; Simioni Assmann, Tangriani; Cardozo da Silva, Jean Carlos; Bertotti, Fábio L.; Kalinowski, Hypolito J.; Cardoso, Rafael

2015-09-01

This paper reports the process of pattern classification of the chewing process of ruminants. We propose a simplified signal processing scheme for optical fiber Bragg grating (FBG) sensors based on machine learning techniques. The FBG sensors measure the biomechanical forces during jaw movements and an artificial neural network is responsible for the classification of the associated chewing pattern. In this study, three patterns associated to dietary supplement, hay and ryegrass were considered. Additionally, two other important events for ingestive behavior studies were monitored, rumination and idle period. Experimental results show that the proposed approach for pattern classification has been capable of differentiating the materials involved in the chewing process with a small classification error.

Determination of Terfenol-D magnetostriction characteristics for sensor application using fiber Bragg grating

Science.gov (United States)

de Morais Sousa, Kleiton; Zandonay, Ricardo; Vagner da Silva, Erlon; Martelli, Cicero; Cardozo da Silva, Jean Carlos

2014-08-01

Electric current sensor based on magnetostriction phenomenon has been reported in several papers. In common these previous papers used a fiber Bragg grating (FBG) to determine the strain of the magnetostrictive material. However, magnetostriction sensors present few disadvantages often neglected, such as the temperature dependence of magnetostriction. In this paper a Terfenol-D rod (a giant magnetostrictive material-GMM) is used for tests. For simultaneous measurement of temperature and strain two multiplexed FBGs are used. The first test presents unipolar characteristics of Terfenol-D magnetostriction. Other test determines the Terfenol-D response for different temperatures. The Terfenol-D sensitivity increase when the temperature increases, however the saturation of the material occurs in small field values. The characteristics presented in this paper must be taken into account in the development of magnetostrictive sensors and its limitations.

Magnetic field sensor based on double-sided polished fibre-Bragg gratings

International Nuclear Information System (INIS)

Tien, Chuen-Lin; Hwang, Chang-Chou; Liu, Wen-Feng; Chen, Hong-Wei

2009-01-01

A new magnetic field sensor based on double-sided polished fibre-Bragg gratings (FBGs) coated with an iron thin film for measuring magnetic flux density was experimentally demonstrated with the sensitivity of 25.6 nm T −1 . The sensing mechanism is based on the Bragg wavelength shift as the magnetic field is measured by the proposed sensing head. Results of this study present the intensity of the reflected optical signal as a function of the applied strain on the FBG. This paper shows that an improved method for sensing the wavelength shift with changes in external magnetic field is developed by use of the double-sided polished FBGs

Optical Fiber Grating based Sensors

DEFF Research Database (Denmark)

Michelsen, Susanne

2003-01-01

In this thesis differenct optical fiber gratings are used for sensor purposes. If a fiber with a core concentricity error (CCE) is used, a directional dependent bend sensor can be produced. The CCE direction can be determined by means of diffraction. This makes it possible to produce long......-period gratings in a fiber with a CCE direction parallel or perpendicular to the writing direction. The maximal bending sensitivity is independent on the writing direction, but the detailed bending response is different in the two cases. A temperature and strain sensor, based on a long-period grating and two...... sampled gratings, was produced and investigated. It is based on the different temperature and strain response of these gratings. Both a transfer matrix method and an overlap calculation is performed to explain the sensor response. Another type of sensor is based on tuning and modulation of a laser...

Characterization of a FBG sensor interrogation system based on a mode-locked laser scheme.

Science.gov (United States)

Madrigal, Javier; Fraile-Peláez, Francisco Javier; Zheng, Di; Barrera, David; Sales, Salvador

2017-10-02

This paper is focused on the characterization of a fiber Bragg grating (FBG) sensor interrogation system based on a fiber ring laser with a semiconductor optical amplifier as the gain medium, and an in-loop electro-optical modulator. This system operates as a switchable active (pulsed) mode-locked laser. The operation principle of the system is explained theoretically and validated experimentally. The ability of the system to interrogate an array of different FBGs in wavelength and spatial domain is demonstrated. Simultaneously, the influence of several important parameters on the performance of the interrogation technique has been investigated. Specifically, the effects of the bandwidth and the reflectivity of the FBGs, the SOA gain, and the depth of the intensity modulation have been addressed.

Corrosion Resistant FBG-Based Quasi-Distributed Sensor for Crude Oil Tank Dynamic Temperature Profile Monitoring

Science.gov (United States)

da Silva Marques, Rogério; Prado, Adilson Ribeiro; da Costa Antunes, Paulo Fernando; de Brito André, Paulo Sérgio; Ribeiro, Moisés R. N.; Frizera-Neto, Anselmo; Pontes, Maria José

2015-01-01

This article presents a corrosion resistant, maneuverable, and intrinsically safe fiber Bragg grating (FBG)-based temperature optical sensor. Temperature monitoring is a critical activity for the oil and gas industry. It typically involves acquiring the desired parameters in a hazardous and corrosive environment. The use of polytetrafluoroethylene (PTFE) was proposed as a means of simultaneously isolating the optical fiber from the corrosive environment and avoiding undesirable mechanical tensions on the FBGs. The presented sensor head is based on multiple FBGs inscribed in a lengthy single mode fiber. The sensor presents an average thermal sensitivity of 8.82 ± 0.09 pm/°C, resulting in a typical temperature resolution of ~0.1 °C and an average time constant value of 6.25 ± 0.08 s. Corrosion and degradation resistance were verified by infrared spectroscopy and scanning electron microscopy during 90 days exposure to high salinity crude oil samples. The developed sensor was tested in a field pilot test, mimicking the operation of an inland crude tank, demonstrating its abilities to dynamically monitor temperature profile. PMID:26690166

All-optical fiber anemometer based on laser heated fiber Bragg gratings.

Science.gov (United States)

Gao, Shaorui; Zhang, A Ping; Tam, Hwa-Yaw; Cho, L H; Lu, Chao

2011-05-23

A fiber-optic anemometer based on fiber Bragg gratings (FBGs) is presented. A short section of cobalt-doped fiber was utilized to make a fiber-based "hot wire" for wind speed measurement. Fiber Bragg gratings (FBGs) were fabricated in the cobalt-doped fiber using 193 nm laser pulses to serve as localized temperature sensors. A miniature all-optical fiber anemometer is constructed by using two FBGs to determine the dynamic thermal equilibrium between the laser heating and air flow cooling through monitoring the FBGs' central wavelengths. It was demonstrated that the sensitivity of the sensor can be adjusted through the power of pump laser or the coating on the FBG. Experimental results reveal that the proposed FBG-based anemometer exhibits very good performance for wind speed measurement. The resolution of the FBG-based anemometer is about 0.012 m/s for wind speed range between 2.0 m/s and 8.0 m/s.

[Progressive damage monitoring of corrugated composite skins by the FBG spectral characteristics].

Science.gov (United States)

Zhang, Yong; Wang, Bang-Feng; Lu, Ji-Yun; Gu, Li-Li; Su, Yong-Gang

2014-03-01

In the present paper, a method of monitoring progressive damage of composite structures by non-uniform fiber Bragg grating (FBG) reflection spectrum is proposed. Due to the finite element analysis of corrugated composite skins specimens, the failure process under tensile load and corresponding critical failure loads of corrugated composite skin was predicated. Then, the non-uniform reflection spectrum of FBG sensor could be reconstructed and the corresponding relationship between layer failure order sequence of corrugated composite skin and FBG sensor reflection spectrums was acquired. A monitoring system based on FBG non-uniform reflection spectrum, which can be used to monitor progressive damage of corrugated composite skins, was built. The corrugated composite skins were stretched under this FBG non-uniform reflection spectrum monitoring system. The results indicate that real-time spectrums acquired by FBG non-uniform reflection spectrum monitoring system show the same trend with the reconstruction reflection spectrums. The maximum error between the corresponding failure and the predictive value is 8.6%, which proves the feasibility of using FBG sensor to monitor progressive damage of corrugated composite skin. In this method, the real-time changes in the FBG non-uniform reflection spectrum within the scope of failure were acquired through the way of monitoring and predicating, and at the same time, the progressive damage extent and layer failure sequence of corru- gated composite skin was estimated, and without destroying the structure of the specimen, the method is easy and simple to operate. The measurement and transmission section of the system are completely composed of optical fiber, which provides new ideas and experimental reference for the field of dynamic monitoring of smart skin.

Test-bed for the remote health monitoring system for bridge structures using FBG sensors

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Lee, Chin-Hyung; Park, Ki-Tae; Joo, Bong-Chul; Hwang, Yoon-Koog

2009-05-01

This paper reports on test-bed for the long-term health monitoring system for bridge structures employing fiber Bragg grating (FBG) sensors, which is remotely accessible via the web, to provide real-time quantitative information on a bridge's response to live loading and environmental changes, and fast prediction of the structure's integrity. The sensors are attached on several locations of the structure and connected to a data acquisition system permanently installed onsite. The system can be accessed through remote communication using an optical cable network, through which the evaluation of the bridge behavior under live loading can be allowed at place far away from the field. Live structural data are transmitted continuously to the server computer at the central office. The server computer is connected securely to the internet, where data can be retrieved, processed and stored for the remote web-based health monitoring. Test-bed revealed that the remote health monitoring technology will enable practical, cost-effective, and reliable condition assessment and maintenance of bridge structures.

Study on viscosity measurement using fiber Bragg grating micro-vibration

International Nuclear Information System (INIS)

Song, Le; Fang, Fengzhou; Zhao, Jibo

2013-01-01

It is now ascertained that traditional electric sensors are vulnerable to electromagnetic interference when measuring viscosity. Here, we propose a new viscosity-sensitive structure based on the fiber Bragg grating (FBG) sensing principle and a micro-vibration measurement method. The symmetric micro-vibration motivation method is also described, and a mathematical model for compensational voltage and fluid viscosity is established. The probe amplitude, which is produced by reciprocating stimulation, is accessible by means of an FBG sensor mounted on an equal-strength beam. Viscosity can be therefore calculated using a demodulation technique based on linear edge filtering with long period grating. After performing a group of verifying tests, the sensor has been subsequently calibrated with a series of standard fluids to determine uncertain parameters in the mathematical model. The results of the experiment show that the relative measurement error was less than 2% when the viscosity ranged from 200 to 500 mPa s. The proposed architecture utilizes the characteristics of anti-interference, fast response speed, high resolution and compact structure of FBG, thereby offering a novel modality to achieve an online viscosity measurement. (paper)

Combined application of FBG and PZT sensors for plantar pressure monitoring at low and high speed walking.

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Suresh, R; Bhalla, S; Singh, C; Kaur, N; Hao, J; Anand, S

2015-01-01

Clinical monitoring of planar pressure is vital in several pathological conditions, such as diabetes, where excess pressure might have serious repercussions on health of the patient, even to the extent of amputation. The main objective of this paper is to experimentally evaluate the combined application of the Fibre Bragg Grating (FBG) and the lead zirconate titanate (PZT) piezoceramic sensors for plantar pressure monitoring during walk at low and high speeds. For fabrication of the pressure sensors, the FBGs are embedded within layers of carbon composite material and stacked in an arc shape. From this embedding technique, average pressure sensitivity of 1.3 pm/kPa and resolution of nearly 0.8 kPa is obtained. These sensors are found to be suitable for measuring the static and the low-speed walk generated foot pressure. Simultaneously, PZT patches of size 10 × 10 × 0.3 mm were used as sensors, utilizing the d_{33} (thickness) coupling mode. A sensitivity of 7.06 mV/kPa and a pressure resolution of 0.14 kPa is obtained from these sensors, which are found to be suitable for foot pressure measurement during high speed walking and running. Both types of sensors are attached to the underside of the sole of commercially available shoes. In the experiments, a healthy male subject walks/runs over the treadmill wearing the fabricated shoes at various speeds and the peak pressure is measured using both the sensors. Commercially available low-cost hardware is used for interrogation of the two sensor types. The test results clearly show the feasibility of the FBG and the PZT sensors for measurement of plantar pressure. The PZT sensors are more accurate for measurement of pressure during walking at high speeds. The FBG sensors, on the other hand, are found to be suitable for static and quasi-dynamic (slow walking) conditions. Typically, the measured pressure varied from 400 to 600 kPa below the forefoot and 100 to 1000 kPa below the heel as the walking speed varied from 1

Use of first-order diffraction wavelengths corresponding to dual-grating periodicities in a single fibre Bragg grating for simultaneous temperature and strain measurement

International Nuclear Information System (INIS)

Yam, Sui P; Brodzeli, Zourab; Rollinson, Claire M; Baxter, Greg W; Collins, Stephen F; Wade, Scott A

2009-01-01

A fibre Bragg grating (FBG) sensor, fabricated using a phase mask with 536 nm uniform pitch, for simultaneous temperature and strain measurement is presented. Two peaks/dips occur, at 785 and 1552 nm, due to reflection/transmission at the Bragg wavelength and at twice the Bragg wavelength, and arising primarily from FBG periodicities associated with half the phase mask periodicity and the phase mask periodicity, respectively. This grating was simple to fabricate and by having greater reflectivity at 785 nm, compared with 1552 nm, it is better suited for long-distance operation compared with similar schemes where the greater fibre attenuation at 785 nm is a significant limitation

Performance of a distributed simultaneous strain and temperature sensor based on a Fabry-Perot laser diode and a dual-stage FBG optical demultiplexer.

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Kim, Suhwan; Kwon, Hyungwoo; Yang, Injae; Lee, Seungho; Kim, Jeehyun; Kang, Shinwon

2013-11-12

A simultaneous strain and temperature measurement method using a Fabry-Perot laser diode (FP-LD) and a dual-stage fiber Bragg grating (FBG) optical demultiplexer was applied to a distributed sensor system based on Brillouin optical time domain reflectometry (BOTDR). By using a Kalman filter, we improved the performance of the FP-LD based OTDR, and decreased the noise using the dual-stage FBG optical demultiplexer. Applying the two developed components to the BOTDR system and using a temperature compensating algorithm, we successfully demonstrated the simultaneous measurement of strain and temperature distributions under various experimental conditions. The observed errors in the temperature and strain measured using the developed sensing system were 0.6 °C and 50 με, and the spatial resolution was 1 m, respectively.

Fiber Bragg Grating Array as a Quasi Distributed Temperature Sensor for Furnace Boiler Applications

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Reddy, P. Saidi; Prasad, R. L. N. Sai; Sengupta, D.; Shankar, M. Sai; Srimannarayana, K.; Kishore, P.; Rao, P. Vengal

2011-10-01

This paper presents the experimental work on distributed temperature sensing making use of Fiber Bragg grating (FBG) array sensor for possible applications in the monitoring of temperature profile in high temperature boilers. A special sensor has been designed for this purpose which consists of four FBGs (of wavelengths λB1 = 1547.28 nm, λB2 = 1555.72 nm, λB3 = 1550.84 nm, λB4 = 1545.92 nm) written in hydrogen loaded fiber in line with a spacing of 15 cm between them. All the FBGs are encapsulated inside a stainless steel tube for avoiding micro cracks using rigid probe technique. The spatial distribution of temperature profile inside a prototype boiler has been measured experimentally both in horizontal and vertical directions employing the above sensor and the results are presented.

Performance Optimization Design for a High-Speed Weak FBG Interrogation System Based on DFB Laser

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Yiqiang Yao

2017-06-01

Full Text Available A performance optimization design for a high-speed fiber Bragg grating (FBG interrogation system based on a high-speed distributed feedback (DFB swept laser is proposed. A time-division-multiplexing sensor network with identical weak FBGs is constituted to realize high-capacity sensing. In order to further improve the multiplexing capacity, a waveform repairing algorithm is designed to extend the dynamic demodulation range of FBG sensors. It is based on the fact that the spectrum of an FBG keeps stable over a long period of time. Compared with the pre-collected spectra, the distorted spectra waveform are identified and repaired. Experimental results show that all the identical weak FBGs are distinguished and demodulated at the speed of 100 kHz with a linearity of above 0.99, and the range of dynamic demodulation is extended by 40%.

Performance Optimization Design for a High-Speed Weak FBG Interrogation System Based on DFB Laser.

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Yao, Yiqiang; Li, Zhengying; Wang, Yiming; Liu, Siqi; Dai, Yutang; Gong, Jianmin; Wang, Lixin

2017-06-22

A performance optimization design for a high-speed fiber Bragg grating (FBG) interrogation system based on a high-speed distributed feedback (DFB) swept laser is proposed. A time-division-multiplexing sensor network with identical weak FBGs is constituted to realize high-capacity sensing. In order to further improve the multiplexing capacity, a waveform repairing algorithm is designed to extend the dynamic demodulation range of FBG sensors. It is based on the fact that the spectrum of an FBG keeps stable over a long period of time. Compared with the pre-collected spectra, the distorted spectra waveform are identified and repaired. Experimental results show that all the identical weak FBGs are distinguished and demodulated at the speed of 100 kHz with a linearity of above 0.99, and the range of dynamic demodulation is extended by 40%.

Strain measurement using multiplexed fiber optic sensors

International Nuclear Information System (INIS)

Kwon, Il Bum; Kim, Chi Yeop; Yoon, Dong Jin; Lee, Seung Seok

2003-01-01

FBG(Fiber Bragg grating) sensor, which is one of the fiber optic sensors for the application of smart structures, can not only measure one specific point but also multiple points by multiplexing techniques. We have proposed a novel multiplexing technique of FBG sensor by the intensity modulation of light source. This technique is applicable to WDM(Wavelength Division Multiplexing) technique and number of sensors in this system can be increased by using this technique with WDM technique.

Dynamic fiber Bragg grating strain sensor interrogation with real-time measurement

Science.gov (United States)

Park, Jinwoo; Kwon, Yong Seok; Ko, Myeong Ock; Jeon, Min Yong

2017-11-01

We demonstrate a 1550 nm band resonance Fourier-domain mode-locked (FDML) fiber laser with fiber Bragg grating (FBG) array. Using the FDML fiber laser, we successfully demonstrate real-time monitoring of dynamic FBG strain sensor interrogation for structural health monitoring. The resonance FDML fiber laser consists of six multiplexed FBGs, which are arranged in series with delay fiber lengths. It is operated by driving the fiber Fabry-Perot tunable filter (FFP-TF) with a sinusoidal waveform at a frequency corresponding to the round-trip time of the laser cavity. Each FBG forms a laser cavity independently in the FDML fiber laser because the light travels different length for each FBG. The very closely positioned two FBGs in a pair are operated simultaneously with a frequency in the FDML fiber laser. The spatial positions of the sensing pair can be distinguished from the variation of the applied frequency to the FFP-TF. One of the FBGs in the pair is used as a reference signal and the other one is fixed on the piezoelectric transducer stack to apply the dynamic strain. We successfully achieve real-time measurement of the abrupt change of the frequencies applied to the FBG without any signal processing delay. The real-time monitoring system is displayed simultaneously on the monitor for the variation of the two peaks, the modulation interval of the two peaks, and their fast Fourier transform spectrum. The frequency resolution of the dynamic variation could reach up to 0.5 Hz for 2 s integration time. It depends on the integration time to measure the dynamic variation. We believe that the real-time monitoring system will have a potential application for structural health monitoring.

Performance of a Distributed Simultaneous Strain and Temperature Sensor Based on a Fabry-Perot Laser Diode and a Dual-Stage FBG Optical Demultiplexer

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Shinwon Kang

2013-11-01

Full Text Available A simultaneous strain and temperature measurement method using a Fabry-Perot laser diode (FP-LD and a dual-stage fiber Bragg grating (FBG optical demultiplexer was applied to a distributed sensor system based on Brillouin optical time domain reflectometry (BOTDR. By using a Kalman filter, we improved the performance of the FP-LD based OTDR, and decreased the noise using the dual-stage FBG optical demultiplexer. Applying the two developed components to the BOTDR system and using a temperature compensating algorithm, we successfully demonstrated the simultaneous measurement of strain and temperature distributions under various experimental conditions. The observed errors in the temperature and strain measured using the developed sensing system were 0.6 °C and 50 με, and the spatial resolution was 1 m, respectively.

Modeling and Analysis of a Combined Stress-Vibration Fiber Bragg Grating Sensor.

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Yao, Kun; Lin, Qijing; Jiang, Zhuangde; Zhao, Na; Tian, Bian; Shi, Peng; Peng, Gang-Ding

2018-03-01

A combined stress-vibration sensor was developed to measure stress and vibration simultaneously based on fiber Bragg grating (FBG) technology. The sensor is composed of two FBGs and a stainless steel plate with a special design. The two FBGs sense vibration and stress and the sensor can realize temperature compensation by itself. The stainless steel plate can significantly increase sensitivity of vibration measurement. Theoretical analysis and Finite Element Method (FEM) were used to analyze the sensor's working mechanism. As demonstrated with analysis, the obtained sensor has working range of 0-6000 Hz for vibration sensing and 0-100 MPa for stress sensing, respectively. The corresponding sensitivity for vibration is 0.46 pm/g and the resulted stress sensitivity is 5.94 pm/MPa, while the nonlinearity error for vibration and stress measurement is 0.77% and 1.02%, respectively. Compared to general FBGs, the vibration sensitivity of this sensor is 26.2 times higher. Therefore, the developed sensor can be used to concurrently detect vibration and stress. As this sensor has height of 1 mm and weight of 1.15 g, it is beneficial for minimization and integration.

Evaluation of fiber Bragg grating sensor interrogation using InGaAs linear detector arrays and Gaussian approximation on embedded hardware

Science.gov (United States)

Kumar, Saurabh; Amrutur, Bharadwaj; Asokan, Sundarrajan

2018-02-01

Fiber Bragg Grating (FBG) sensors have become popular for applications related to structural health monitoring, biomedical engineering, and robotics. However, for successful large scale adoption, FBG interrogation systems are as important as sensor characteristics. Apart from accuracy, the required number of FBG sensors per fiber and the distance between the device in which the sensors are used and the interrogation system also influence the selection of the interrogation technique. For several measurement devices developed for applications in biomedical engineering and robotics, only a few sensors per fiber are required and the device is close to the interrogation system. For these applications, interrogation systems based on InGaAs linear detector arrays provide a good choice. However, their resolution is dependent on the algorithms used for curve fitting. In this work, a detailed analysis of the choice of algorithm using the Gaussian approximation for the FBG spectrum and the number of pixels used for curve fitting on the errors is provided. The points where the maximum errors occur have been identified. All comparisons for wavelength shift detection have been made against another interrogation system based on the tunable swept laser. It has been shown that maximum errors occur when the wavelength shift is such that one new pixel is included for curve fitting. It has also been shown that an algorithm with lower computation cost compared to the more popular methods using iterative non-linear least squares estimation can be used without leading to the loss of accuracy. The algorithm has been implemented on embedded hardware, and a speed-up of approximately six times has been observed.

RETRACTED ARTICLE: Quasi-distributed fiber bragg grating array sensor for furnace applications

Science.gov (United States)

Reddy, P. Saidi; Sai Prasad, R. L. N.; Sen Gupta, D.; Sai Shankar, M.; Srimannarayana, K.; Ravinder Reddy, P.

2012-05-01

An experimental work on distributed temperature sensing making use of the fiber Bragg grating (FBG) array sensor for possible applications in the monitoring of the temperature profile in high temperature boilers is presented. A special sensor has been designed for this purpose which consists of four FBGs (of wavelengths λ B1 =1545.8 nm, λ B2 =1547 nm, λ B3 =1550.8 nm, λ B4 =1555.5 nm at 30 °C) written in the hydrogen-loaded fiber in line. All the FBGs are encapsulated inside a stainless steel tube using the rigid probe technique for avoiding micro cracks. The spatial distribution of the temperature profile inside a prototype boiler was measured experimentally both in horizontal and vertical directions employing the above sensor, and the results are presented. Further, the finite element simulation has been carried out by using ANSYS R11 software to predict temperature contours in the boiler, and the experimental and predicted results were found to be closely matching.

Fiber Bragg Grating Sensor for Fault Detection in Radial and Network Transmission Lines

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Mehdi Shadaram

2010-10-01

Full Text Available In this paper, a fiber optic based sensor capable of fault detection in both radial and network overhead transmission power line systems is investigated. Bragg wavelength shift is used to measure the fault current and detect fault in power systems. Magnetic fields generated by currents in the overhead transmission lines cause a strain in magnetostrictive material which is then detected by Fiber Bragg Grating (FBG. The Fiber Bragg interrogator senses the reflected FBG signals, and the Bragg wavelength shift is calculated and the signals are processed. A broadband light source in the control room scans the shift in the reflected signal. Any surge in the magnetic field relates to an increased fault current at a certain location. Also, fault location can be precisely defined with an artificial neural network (ANN algorithm. This algorithm can be easily coordinated with other protective devices. It is shown that the faults in the overhead transmission line cause a detectable wavelength shift on the reflected signal of FBG and can be used to detect and classify different kind of faults. The proposed method has been extensively tested by simulation and results confirm that the proposed scheme is able to detect different kinds of fault in both radial and network system.

A novel fast phase correlation algorithm for peak wavelength detection of Fiber Bragg Grating sensors.

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Lamberti, A; Vanlanduit, S; De Pauw, B; Berghmans, F

2014-03-24

Fiber Bragg Gratings (FBGs) can be used as sensors for strain, temperature and pressure measurements. For this purpose, the ability to determine the Bragg peak wavelength with adequate wavelength resolution and accuracy is essential. However, conventional peak detection techniques, such as the maximum detection algorithm, can yield inaccurate and imprecise results, especially when the Signal to Noise Ratio (SNR) and the wavelength resolution are poor. Other techniques, such as the cross-correlation demodulation algorithm are more precise and accurate but require a considerable higher computational effort. To overcome these problems, we developed a novel fast phase correlation (FPC) peak detection algorithm, which computes the wavelength shift in the reflected spectrum of a FBG sensor. This paper analyzes the performance of the FPC algorithm for different values of the SNR and wavelength resolution. Using simulations and experiments, we compared the FPC with the maximum detection and cross-correlation algorithms. The FPC method demonstrated a detection precision and accuracy comparable with those of cross-correlation demodulation and considerably higher than those obtained with the maximum detection technique. Additionally, FPC showed to be about 50 times faster than the cross-correlation. It is therefore a promising tool for future implementation in real-time systems or in embedded hardware intended for FBG sensor interrogation.

A spectral profile multiplexed FBG sensor network with application to strain measurement in a Kevlar woven fabric

Science.gov (United States)

Guo, Guodong; Hackney, Drew; Pankow, Mark; Peters, Kara

2017-04-01

A spectral profile division multiplexed fiber Bragg grating (FBG) sensor network is described in this paper. The unique spectral profile of each sensor in the network is identified as a distinct feature to be interrogated. Spectrum overlap is allowed under working conditions. Thus, a specific wavelength window does not need to be allocated to each sensor as in a wavelength division multiplexed (WDM) network. When the sensors are serially connected in the network, the spectrum output is expressed through a truncated series. To track the wavelength shift of each sensor, the identification problem is transformed to a nonlinear optimization problem, which is then solved by a modified dynamic multi-swarm particle swarm optimizer (DMS-PSO). To demonstrate the application of the developed network, a network consisting of four FBGs was integrated into a Kevlar woven fabric, which was under a quasi-static load imposed by an impactor head. Due to the substantial radial strain in the fabric, the spectrums of different FBGs were found to overlap during the loading process. With the developed interrogating method, the overlapped spectrum would be distinguished thus the wavelength shift of each sensor can be monitored.

Radiation resistant fiber Bragg grating in random air-line fibers for sensing applications in nuclear reactor cores.

Science.gov (United States)

Zaghloul, Mohamed A S; Wang, Mohan; Huang, Sheng; Hnatovsky, Cyril; Grobnic, Dan; Mihailov, Stephen; Li, Ming-Jun; Carpenter, David; Hu, Lin-Wen; Daw, Joshua; Laffont, Guillaume; Nehr, Simon; Chen, Kevin P

2018-04-30

This paper reports the testing results of radiation resistant fiber Bragg grating (FBG) in random air-line (RAL) fibers in comparison with FBGs in other radiation-hardened fibers. FBGs in RAL fibers were fabricated by 80 fs ultrafast laser pulse using a phase mask approach. The fiber Bragg gratings tests were carried out in the core region of a 6 MW MIT research reactor (MITR) at a steady temperature above 600°C and an average fast neutron (>1 MeV) flux >1.2 × 10 14 n/cm 2 /s. Fifty five-day tests of FBG sensors showed less than 5 dB reduction in FBG peak strength after over 1 × 10 20 n/cm 2 of accumulated fast neutron dose. The radiation-induced compaction of FBG sensors produced less than 5.5 nm FBG wavelength shift toward shorter wavelength. To test temporal responses of FBG sensors, a number of reactor anomaly events were artificially created to abruptly change reactor power, temperature, and neutron flux over short periods of time. The thermal sensitivity and temporal responses of FBGs were determined at different accumulated doses of neutron flux. Results presented in this paper reveal that temperature-stable Type-II FBGs fabricated in radiation-hardened fibers can survive harsh in-pile conditions. Despite large parameter drift induced by strong nuclear radiation, further engineering and innovation on both optical fibers and fiber devices could lead to useful fiber sensors for various in-pile measurements to improve safety and efficiency of existing and next generation nuclear reactors.

A Robust Fiber Bragg Grating Hydrogen Gas Sensor Using Platinum-Supported Silica Catalyst Film

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Marina Kurohiji

2018-01-01

Full Text Available A robust fiber Bragg grating (FBG hydrogen gas sensor for reliable multipoint-leakage monitoring has been developed. The sensing mechanism is based on shifts of center wavelength of the reflection spectra due to temperature change caused by catalytic combustion heat. The sensitive film which consists of platinum-supported silica (Pt/SiO2 catalyst film was obtained using sol-gel method. The precursor solution was composed of hexachloroplatinic acid and commercially available silica precursor solution. The atom ratio of Si : Pt was fixed at 13 : 1. A small amount of this solution was dropped on the substrate and dried at room temperature. After that, the film was calcined at 500°C in air. These procedures were repeated and therefore thick hydrogen-sensitive films were obtained. The catalytic film obtained by 20-time coating on quartz glass substrate showed a temperature change 75 K upon exposure to 3 vol.% H2. For realizing robust sensor device, this catalytic film was deposited and FBG portion was directly fixed on titanium substrate. The sensor device showed good performances enough to detect hydrogen gas in the concentration range below lower explosion limit at room temperature. The enhancement of the sensitivity was attributed to not only catalytic combustion heat but also related thermal strain.

Strain-temperature monitor of high speed railway switch by fiber Bragg grating gauges

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Li, Weilai; Huang, Xiaomei; Cheng, Jian; Pan, Jianjun

2010-10-01

On the 350km/h high speed railway there is a seamless track switch on a bridge. 32 Fiber Bragg Grating (FGB) gauges are used along the neutral line of the tracks to monitor the strain generated by thermal, geological and vibrational factors, and these FBG strain gauges have the function of strain expansion. Meanwhile other 6 FBG sensors are used to measure the temperature for strain compensating purpose. The Finite Element Analysis method is used to analyze the special shape of the gauges. A testing unit was used to test the FBG gauges and bare FBG on the track samples under measurable pressure and tension. The fixing and encapsulating technology of FBG gauges on the surface of the track and to protect the fiber cable to survive in the harsh conditions are discussed. The strain status of switch tracks could be obtained by processing the data from FBG strain gauges and FBG temperature sensors. The results of measurement showed that in 9 days, the strain in the track shifted 350 μɛ, and the strain curves closely correlated with the temperature curves.

FBG-Based Monitoring of Geohazards: Current Status and Trends

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Hong-Hu Zhu

2017-02-01

Full Text Available 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.

FBG-Based Monitoring of Geohazards: Current Status and Trends.

Science.gov (United States)

Zhu, Hong-Hu; Shi, Bin; Zhang, Cheng-Cheng

2017-02-24

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.

Stimulus responsive hydrogel-coated etched fiber Bragg grating for carcinogenic chromium (VI) sensing

Science.gov (United States)

Kishore, Pabbisetti Vayu Nandana; Madhuvarasu, Sai Shankar; Moru, Satyanarayana

2018-01-01

This paper proposes a chemo-mechanical-optical sensing approach for the detection of carcinogenic chromium (VI) metal ion using an etched fiber Bragg grating (FBG) coated with stimulus responsive hydrogel. Hydrogel synthesized from the blends of (3-acrylamidopropyl)-trimethylammonium chloride, which is highly responsive to chromium ions suffers a volume change when placed in Cr solution. When the proposed sensor system is exposed to various concentrations of Cr (VI) ion solution, FBG peak shifts due to the mechanical strain induced by the swelling of the hydrogel. The peak shift is correlated with the concentration of the Cr (VI) metal ion. Due to the reduction in the cladding diameter of FBG, wastage of swelling force due to hydrogel on FBG is lowered and utilized for more wavelength peak shift of FBG resulting in the increase in the sensitivity. The resolution of the sensor system is found to be 0.072 ppb. Trace amounts of chromium (VI) ion as low as 10 ppb can be sensed by this method. The sensor has shown good sensitivity, selectivity, and repeatability. The salient features of the sensors are its compact size, light weight, and adoptability for remote monitoring.

Sensitive detection of C-reactive protein using optical fiber Bragg gratings.

Science.gov (United States)

Sridevi, S; Vasu, K S; Asokan, S; Sood, A K

2015-03-15

An accurate and highly sensitive sensor platform has been demonstrated for the detection of C-reactive protein (CRP) using optical fiber Bragg gratings (FBGs). The CRP detection has been carried out by monitoring the shift in Bragg wavelength (ΔλB) of an etched FBG (eFBG) coated with an anti-CRP antibody (aCRP)-graphene oxide (GO) complex. The complex is characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and atomic force microscopy. A limit of detection of 0.01mg/L has been achieved with a linear range of detection from 0.01mg/L to 100mg/L which includes clinical range of CRP. The eFBG sensor coated with only aCRP (without GO) show much less sensitivity than that of aCRP-GO complex coated eFBG. The eFBG sensors show high specificity to CRP even in the presence of other interfering factors such as urea, creatinine and glucose. The affinity constant of ∼1.1×10(10)M(-1) has been extracted from the data of normalized shift (ΔλB/λB) as a function of CRP concentration. Copyright © 2014 Elsevier B.V. All rights reserved.

Dynamic strain distribution measurement and crack detection of an adhesive-bonded single-lap joint under cyclic loading using embedded FBG

International Nuclear Information System (INIS)

Ning, Xiaoguang; Murayama, Hideaki; Kageyama, Kazuro; Wada, Daichi; Kanai, Makoto; Ohsawa, Isamu; Igawa, Hirotaka

2014-01-01

In this study, the dynamic strain distribution measurement of an adhesive-bonded single-lap joint was carried out in a cyclic load test using a fiber Bragg grating (FBG) sensor embedded into the adhesive/adherend interface along the overlap length direction. Unidirectional carbon fiber reinforced plastic (CFRP) substrates were bonded by epoxy resin to form the joint, and the FBG sensor was embedded into the surface of one substrate during its curing. The measurement was carried out with a sampling rate of 5 Hz by the sensing system, based on the optical frequency domain reflectometry (OFDR) throughout the test. A finite element analysis (FEA) was performed for the measurement evaluation using a three-dimensional model, which included the embedded FBG sensor. The crack detection method, based on the longitudinal strain distribution measurement, was introduced and performed to estimate the cracks that occurred at the adhesive/adherend interface in the test. (paper)

Statistical Analysis of Stress Signals from Bridge Monitoring by FBG System

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Xiao-Wei Ye

2018-02-01

Full Text Available In this paper, a fiber Bragg grating (FBG-based stress monitoring system instrumented on an orthotropic steel deck arch bridge is demonstrated. The FBG sensors are installed at two types of critical fatigue-prone welded joints to measure the strain and temperature signals. A total of 64 FBG sensors are deployed around the rib-to-deck and rib-to-diagram areas at the mid-span and quarter-span of the investigated orthotropic steel bridge. The local stress behaviors caused by the highway loading and temperature effect during the construction and operation periods are presented with the aid of a wavelet multi-resolution analysis approach. In addition, the multi-modal characteristic of the rainflow counted stress spectrum is modeled by the method of finite mixture distribution together with a genetic algorithm (GA-based parameter estimation approach. The optimal probability distribution of the stress spectrum is determined by use of Bayesian information criterion (BIC. Furthermore, the hot spot stress of the welded joint is calculated by an extrapolation method recommended in the specification of International Institute of Welding (IIW. The stochastic characteristic of stress concentration factor (SCF of the concerned welded joint is addressed. The proposed FBG-based stress monitoring system and probabilistic stress evaluation methods can provide an effective tool for structural monitoring and condition assessment of orthotropic steel bridges.

An Optical Fibre Depth (Pressure) Sensor for Remote Operated Vehicles in Underwater Applications

Science.gov (United States)

Duraibabu, Dinesh Babu; Poeggel, Sven; Omerdic, Edin; Capocci, Romano; Lewis, Elfed; Newe, Thomas; Leen, Gabriel; Toal, Daniel; Dooly, Gerard

2017-01-01

A miniature sensor for accurate measurement of pressure (depth) with temperature compensation in the ocean environment is described. The sensor is based on an optical fibre Extrinsic Fabry-Perot interferometer (EFPI) combined with a Fibre Bragg Grating (FBG). The EFPI provides pressure measurements while the Fibre Bragg Grating (FBG) provides temperature measurements. The sensor is mechanically robust, corrosion-resistant and suitable for use in underwater applications. The combined pressure and temperature sensor system was mounted on-board a mini remotely operated underwater vehicle (ROV) in order to monitor the pressure changes at various depths. The reflected optical spectrum from the sensor was monitored online and a pressure or temperature change caused a corresponding observable shift in the received optical spectrum. The sensor exhibited excellent stability when measured over a 2 h period underwater and its performance is compared with a commercially available reference sensor also mounted on the ROV. The measurements illustrates that the EFPI/FBG sensor is more accurate for depth measurements (depth of ~0.020 m). PMID:28218727

Experimental testing of a self-sensing FRP-concrete composite beam using FBG sensors

Science.gov (United States)

Wang, Yanlei; Hao, Qingduo; Ou, Jinping

2009-03-01

A new kind of self-sensing fiber reinforced polymer (FRP)-concrete composite beam, which consists of a FRP box beam combined with a thin layer of concrete in the compression zone, was developed by using two embedded FBG sensors in the top and bottom flanges of FRP box beam at mid-span section along longitudinal direction, respectively. The flexural behavior of the proposed self-sensing FRP-concrete composite beam was experimentally studied in four-point bending. The longitudinal strains of the composite beam were recorded using the embedded FBG sensors as well as the surfacebonded electric resistance strain gauges. Test results indicate that the FBG sensors can faithfully record the longitudinal strain of the composite beam in tension at bottom flange of the FRP box beam or in compression at top flange over the entire load range, as compared with the surface-bonded strain gauges. The proposed self-sensing FRP-concrete composite beam can monitor its longitudinal strains in serviceability limit state as well as in strength limit state, and will has wide applications for long-term monitoring in civil engineering.

MEMS Bragg grating force sensor

DEFF Research Database (Denmark)

Reck, Kasper; Thomsen, Erik Vilain; Hansen, Ole

2011-01-01

We present modeling, design, fabrication and characterization of a new type of all-optical frequency modulated MEMS force sensor based on a mechanically amplified double clamped waveguide beam structure with integrated Bragg grating. The sensor is ideally suited for force measurements in harsh...... environments and for remote and distributed sensing and has a measured sensitivity of -14 nm/N, which is several times higher than what is obtained in conventional fiber Bragg grating force sensors. © 2011 Optical Society of America....

Research on FBG-Based CFRP Structural Damage Identification Using BP Neural Network

Science.gov (United States)

Geng, Xiangyi; Lu, Shizeng; Jiang, Mingshun; Sui, Qingmei; Lv, Shanshan; Xiao, Hang; Jia, Yuxi; Jia, Lei

2018-06-01

A damage identification system of carbon fiber reinforced plastics (CFRP) structures is investigated using fiber Bragg grating (FBG) sensors and back propagation (BP) neural network. FBG sensors are applied to construct the sensing network to detect the structural dynamic response signals generated by active actuation. The damage identification model is built based on the BP neural network. The dynamic signal characteristics extracted by the Fourier transform are the inputs, and the damage states are the outputs of the model. Besides, damages are simulated by placing lumped masses with different weights instead of inducing real damages, which is confirmed to be feasible by finite element analysis (FEA). At last, the damage identification system is verified on a CFRP plate with 300 mm × 300 mm experimental area, with the accurate identification of varied damage states. The system provides a practical way for CFRP structural damage identification.

Optical Fiber Grating Hydrogen Sensors: A Review.

Science.gov (United States)

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

2017-03-12

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.

Characteristics of the Fiber Laser Sensor System Based on Etched-Bragg Grating Sensing Probe for Determination of the Low Nitrate Concentration in Water.

Science.gov (United States)

Pham, Thanh Binh; Bui, Huy; Le, Huu Thang; Pham, Van Hoi

2016-12-22

The necessity of environmental protection has stimulated the development of many kinds of methods allowing the determination of different pollutants in the natural environment, including methods for determining nitrate in source water. In this paper, the characteristics of an etched fiber Bragg grating (e-FBG) sensing probe-which integrated in fiber laser structure-are studied by numerical simulation and experiment. The proposed sensor is demonstrated for determination of the low nitrate concentration in a water environment. Experimental results show that this sensor could determine nitrate in water samples at a low concentration range of 0-80 ppm with good repeatability, rapid response, and average sensitivity of 3.5 × 10 -3 nm/ppm with the detection limit of 3 ppm. The e-FBG sensing probe integrated in fiber laser demonstrates many advantages, such as a high resolution for wavelength shift identification, high optical signal-to-noise ratio (OSNR of 40 dB), narrow bandwidth of 0.02 nm that enhanced accuracy and precision of wavelength peak measurement, and capability for optical remote sensing. The obtained results suggested that the proposed e-FBG sensor has a large potential for the determination of low nitrate concentrations in water in outdoor field work.

Characteristics of the Fiber Laser Sensor System Based on Etched-Bragg Grating Sensing Probe for Determination of the Low Nitrate Concentration in Water

Directory of Open Access Journals (Sweden)

Thanh Binh Pham

2016-12-01

Full Text Available The necessity of environmental protection has stimulated the development of many kinds of methods allowing the determination of different pollutants in the natural environment, including methods for determining nitrate in source water. In this paper, the characteristics of an etched fiber Bragg grating (e-FBG sensing probe—which integrated in fiber laser structure—are studied by numerical simulation and experiment. The proposed sensor is demonstrated for determination of the low nitrate concentration in a water environment. Experimental results show that this sensor could determine nitrate in water samples at a low concentration range of 0–80 ppm with good repeatability, rapid response, and average sensitivity of 3.5 × 10−3 nm/ppm with the detection limit of 3 ppm. The e-FBG sensing probe integrated in fiber laser demonstrates many advantages, such as a high resolution for wavelength shift identification, high optical signal-to-noise ratio (OSNR of 40 dB, narrow bandwidth of 0.02 nm that enhanced accuracy and precision of wavelength peak measurement, and capability for optical remote sensing. The obtained results suggested that the proposed e-FBG sensor has a large potential for the determination of low nitrate concentrations in water in outdoor field work.

Fiber Bragg Grating Measuring System for Simultaneous Monitoring of Temperature and Humidity in Mechanical Ventilation

Directory of Open Access Journals (Sweden)

Carlo Massaroni

2017-04-01

Full Text Available During mechanical ventilation, the humidification of the dry air delivered by the mechanical ventilator is recommended. Among several solutions, heated wire humidifiers (HWHs have gained large acceptance to be used in this field. The aim of this work is to fabricate a measuring system based on fiber Bragg grating (FBG for the simultaneous monitoring of gas relative humidity (RH and temperature, intended to be used for providing feedback to the HWHs’ control. This solution can be implemented using an array of two FBGs having a different center wavelength. Regarding RH monitoring, three sensors have been fabricated by coating an FBG with two different moisture-sensitive and biocompatible materials: the first two sensors were fabricated by coating the grating with a 3 mm × 3 mm layer of agar and agarose; to investigate the influence of the coating thickness to the sensor response, a third sensor was developed with a 5 mm × 5 mm layer of agar. The sensors have been assessed in a wide range of RH (up to 95% during both an ascending and a subsequent descending phase. Only the response of the 3 mm × 3 mm-coated sensors were fast enough to follow the RH changes, showing a mean sensitivity of about 0.14 nm/% (agar-coated and 0.12 nm/% (agarose-coated. The hysteresis error was about <10% in the two sensors. The contribution of temperature changes on these RH sensors was negligible. The temperature measurement was performed by a commercial FBG insensitive to RH changes. The small size of these FBG-based sensors, the use of biocompatible polymers, and the possibility to measure both temperature and RH by using the same fiber optic embedding an array of two FBGs make intriguing the use of this solution for application in the control of HWHs.

High-sensitivity bend angle measurements using optical fiber gratings.

Science.gov (United States)

Rauf, Abdul; Zhao, Jianlin; Jiang, Biqiang

2013-07-20

We present a high-sensitivity and more flexible bend measurement method, which is based on the coupling of core mode to the cladding modes at the bending region in concatenation with optical fiber grating serving as band reflector. The characteristics of a bend sensing arm composed of bending region and optical fiber grating is examined for different configurations including single fiber Bragg grating (FBG), chirped FBG (CFBG), and double FBGs. The bend loss curves for coated, stripped, and etched sections of fiber in the bending region with FBG, CFBG, and double FBG are obtained experimentally. The effect of separation between bending region and optical fiber grating on loss is measured. The loss responses for single FBG and CFBG configurations are compared to discover the effectiveness for practical applications. It is demonstrated that the sensitivity of the double FBG scheme is twice that of the single FBG and CFBG configurations, and hence acts as sensitivity multiplier. The bend loss response for different fiber diameters obtained through etching in 40% hydrofluoric acid, is measured in double FBG scheme that resulted in a significant increase in the sensitivity, and reduction of dead-zone.

Uniform spacing interrogation of a Fourier domain mode-locked fiber Bragg grating sensor system using a polarization-maintaining fiber Sagnac interferometer

OpenAIRE

Lee, Hwi Don; Jung, Eun Joo; Jeong, Myung Yung; Chen, Zhongping; Kim, Chang-Seok

2013-01-01

A novel linearized interrogation method is presented for a Fourier domain mode-locked (FDML) fiber Bragg grating (FBG) sensor system. In a high speed regime over several tens of kHz modulations, a sinusoidal wave is available to scan the center wavelength of an FDML wavelength-swept laser, instead of a conventional triangular wave. However, sinusoidal wave modulation suffers from an exaggerated non-uniform wavelength-spacing response in demodulating the time-encoded parameter to the absolute ...

Analysis of simultaneous measurement of temperature and strain using different combinations of FBG

Science.gov (United States)

Ashik T., J.; Kachare, Nitin; Kalyani bai, K.; Kumar, D. Sriram

2017-06-01

The Fiber Bragg Grating (FBG) can be used for measuring temperature and or strain. In this paper analysis of different combinations of FBG is made. Certain parameters of FBG are considered such as Bandwidth, Side lobes, Peak power, and Sensitivity. Simultaneous measurement of temperature and strain is made using two combinations of FBG. The setup is simulated using two software. Optigrating 4.2.2 is used for designing different types of gratings such as Uniform, Apodized, Tilted and Superstructure. After designing, these files are exported to Optisystem 12 to simulate the spectrum and to observe the parameters.

Crack Detection in Fibre Reinforced Plastic Structures Using Embedded Fibre Bragg Grating Sensors: Theory, Model Development and Experimental Validation

DEFF Research Database (Denmark)

Pereira, Gilmar Ferreira; Mikkelsen, Lars Pilgaard; McGugan, Malcolm

2015-01-01

properties. When applying this concept to different structures, sensor systems and damage types, a combination of damage mechanics, monitoring technology, and modelling is required. The primary objective of this article is to demonstrate such a combination. This article is divided in three main topics......: the damage mechanism (delamination of FRP), the structural health monitoring technology (fibre Bragg gratings to detect delamination), and the finite element method model of the structure that incorporates these concepts into a final and integrated damage-monitoring concept. A novel method for assessing...... by the end-user. Conjointly, a novel model for sensor output prediction (virtual sensor) was developed using this FBG sensor crack monitoring concept and implemented in a finite element method code. The monitoring method was demonstrated and validated using glass fibre double cantilever beam specimens...

Optical Fiber Thermometer Based on Fiber Bragg Gratings

Science.gov (United States)

Rosli, Ekbal Bin; Mohd. Noor, Uzer

2018-03-01

Fiber Bragg grating has generated much interest in use as sensors to measure strain, temperature, and other physical parameters. It also the most common component used to develop this sensor with the advantages of simple, intrinsic sensing elements, electrically passive operation, EMI immunity, high sensitivity, compact size and potentially low cost [6]. This paper reports the design of an optical fiber thermometer based on fiber Bragg gratings. The system was developed for detecting temperature and strain by monitoring the shift of Bragg wavelength. The shifting of Bragg wavelength is used to indicate the temperature and strain due to the change in the surrounding temperature and strain. When the temperature and strain reach the exact wavelength level of the system, the temperature and strain value will display on the Arduino liquid crystal display (LCD). The optical fiber will provide the broadband light source and after passing the FBG the Bragg wavelength into the optical spectrum analyzer (OSA). The system is based on FBG as a physical quantity sensor. The temperatures measured is taken from the water bath and that of the strain is provided by amount of slotted mass used. The outcome of this project is to characterize the Bragg wavelength shifting from the fiber Bragg grating output. As the conclusion, this project provides an efficient optical fiber thermometer in measuring temperature and strain in order to replace the use of conventional electrical instruments.

Aluminum-thin-film packaged fiber Bragg grating probes for monitoring the maximum tensile strain of composite materials.

Science.gov (United States)

Im, Jooeun; Kim, Mihyun; Choi, Ki-Sun; Hwang, Tae-Kyung; Kwon, Il-Bum

2014-06-10

In this paper, new fiber Bragg grating (FBG) sensor probes are designed to intermittently detect the maximum tensile strain of composite materials, so as to evaluate the structural health status. This probe is fabricated by two thin Al films bonded to an FBG optical fiber and two supporting brackets, which are fixed on the surface of composite materials. The residual strain of the Al packaged FBG sensor probe is induced by the strain of composite materials. This residual strain can indicate the maximum strain of composite materials. Two types of sensor probes are prepared-one is an FBG with 18 μm thick Al films, and the other is an FBG with 36 μm thick Al films-to compare the thickness effect on the detection sensitivity. These sensor probes are bonded on the surfaces of carbon fiber reinforced plastics composite specimens. In order to determine the strain sensitivity between the residual strain of the FBG sensor probe and the maximum strain of the composite specimen, tensile tests are performed by universal testing machine, under the loading-unloading test condition. The strain sensitivities of the probes, which have the Al thicknesses of 18 and 36 μm, are determined as 0.13 and 0.23, respectively.

Long-term strain response of polymer optical fiber FBG sensors

DEFF Research Database (Denmark)

Bundalo, Ivan-Lazar; Nielsen, Kristian; Woyessa, Getinet

2017-01-01

We report on the viscoelastic response of PMMA microstructured polymer optical fibers (mPOFs) when exposed to long periods of strain and relaxation, with the strain period ranging from 0.5 min to 50 min. The behavior of the fibers was monitored by inscribing a fiber Bragg grating (FBG) in them...... and tracking the reflection peak. We demonstrate that the fiber, when relaxing from strains of up to 0.9%, has a two-phase recovery: initially linear (elastic driven) and subsequently nonlinear (viscoelastic driven) contraction. The linear (elastic) relaxation wavelength range depends both on the strain level...

Design and performance investigation of a highly accurate apodized fiber Bragg grating-based strain sensor in single and quasi-distributed systems.

Science.gov (United States)

Ali, Taha A; Shehata, Mohamed I; Mohamed, Nazmi A

2015-06-01

In this work, fiber Bragg grating (FBG) strain sensors in single and quasi-distributed systems are investigated, seeking high-accuracy measurement. Since FBG-based strain sensors of small lengths are preferred in medical applications, and that causes the full width at half-maximum (FWHM) to be larger, a new apodization profile is introduced for the first time, to the best of our knowledge, with a remarkable FWHM at small sensor lengths compared to the Gaussian and Nuttall profiles, in addition to a higher mainlobe slope at these lengths. A careful selection of apodization profiles with detailed investigation is performed-using sidelobe analysis and the FWHM, which are primary judgment factors especially in a quasi-distributed configuration. A comparison between the elite selection of apodization profiles (extracted from related literature) and the proposed new profile is carried out covering the reflectivity peak, FWHM, and sidelobe analysis. The optimization process concludes that the proposed new profile with a chosen small length (L) of 10 mm and Δnac of 1.4×10-4 is the optimum choice for single stage and quasi-distributed strain-sensor networks, even better than the Gaussian profile at small sensor lengths. The proposed profile achieves the smallest FWHM of 15 GHz (suitable for UDWDM), and the highest mainlobe slope of 130 dB/nm. For the quasi-distributed scenario, a noteworthy high isolation of 6.953 dB is achieved while applying a high strain value of 1500 μstrain (με) for a five-stage strain-sensing network. Further investigation was undertaken, proving that consistency in choosing the apodization profile in the quasi-distributed network is mandatory. A test was made of the inclusion of a uniform apodized sensor among other apodized sensors with the proposed profile in an FBG strain-sensor network.

Coherent pulse interrogation system for fiber Bragg grating sensing of strain and pressure in dynamic extremes of materials.

Science.gov (United States)

Rodriguez, George; Jaime, Marcelo; Balakirev, Fedor; Mielke, Chuck H; Azad, Abul; Marshall, Bruce; La Lone, Brandon M; Henson, Bryan; Smilowitz, Laura

2015-06-01

A 100 MHz fiber Bragg grating (FBG) interrogation system is described and applied to strain and pressure sensing. The approach relies on coherent pulse illumination of the FBG sensor with a broadband short pulse from a femtosecond modelocked erbium fiber laser. After interrogation of the FBG sensor, a long multi-kilometer run of single mode fiber is used for chromatic dispersion to temporally stretch the spectral components of the reflected pulse from the FBG sensor. Dynamic strain or pressure induced spectral shifts in the FBG sensor are detected as a pulsed time domain waveform shift after encoding by the chromatic dispersive line. Signals are recorded using a single 35 GHz photodetector and a 50 G Samples per second, 25 GHz bandwidth, digitizing oscilloscope. Application of this approach to high-speed strain sensing in magnetic materials in pulsed magnetic fields to ~150 T is demonstrated. The FBG wavelength shifts are used to study magnetic field driven magnetostriction effects in LaCoO3. A sub-microsecond temporal shift in the FBG sensor wavelength attached to the sample under first order phase change appears as a fractional length change (strain: ΔL/L-4) in the material. A second application used FBG sensing of pressure dynamics to nearly 2 GPa in the thermal ignition of the high explosive PBX-9501 is also demonstrated. Both applications demonstrate the use of this FBG interrogation system in dynamical extreme conditions that would otherwise not be possible using traditional FBG interrogation approaches that are deemed too slow to resolve such events.

Remote (250 km Fiber Bragg Grating Multiplexing System

Directory of Open Access Journals (Sweden)

Manuel Lopez-Amo

2011-09-01

Full Text Available We propose and demonstrate two ultra-long range fiber Bragg grating (FBG sensor interrogation systems. In the first approach four FBGs are located 200 km from the monitoring station and a signal to noise ratio of 20 dB is obtained. The second improved version is able to detect the four multiplexed FBGs placed 250 km away, offering a signal to noise ratio of 6–8 dB. Consequently, this last system represents the longest range FBG sensor system reported so far that includes fiber sensor multiplexing capability. Both simple systems are based on a wavelength swept laser to scan the reflection spectra of the FBGs, and they are composed by two identical-lengths optical paths: the first one intended to launch the amplified laser signal by means of Raman amplification and the other one is employed to guide the reflection signal to the reception system.

Embedding silica and polymer fibre Bragg gratings (FBG) in plastic 3D-printed sensing patches

DEFF Research Database (Denmark)

Zubel, Michal G.; Sugden, Kate; Webb, David J.

2016-01-01

This paper reports the first demonstration of a silica fibre Bragg grating (SOFBG) embedded in an FDM 3-D printed housing to yield a dual grating temperature-compensated strain sensor. We also report the first ever integration of polymer fibre Bragg grating (POFBG) within a 3-D printed sensing...

Analytical investigation of response of birefringent fiber Bragg grating sensors in distributed monitoring system based on optical frequency domain reflectometry

Science.gov (United States)

Wada, D.; Murayama, H.

2014-01-01

When Fiber Bragg gratings (FBGs) are used as strain sensors, both longitudinal and lateral strain can be applied uniformly or non-uniformly over the length of the FBGs. In order for the demodulation of such FBG signal, this paper investigates the response of birefringent FBGs which are monitored by distributed measurement system based on optical frequency domain reflectometry. A numerical model of the distributed measurement system is built based on piece-wise uniform approach, which considers polarization states of propagating lights. The numerical model simulates analytical response of birefringent FBGs especially when birefringence induces power fluctuations in the distributed spectra, which can be noise or new opportunity for sensitive monitoring of birefringence. Simulation results show the relationships between the power fluctuations and the polarization states of the propagating lights. Consequently, appropriate methods of polarization control for sensitive distributed birefringent FBG monitoring are discussed.

Fabrication of Fiber Bragg Grating Coating with TiO2 Nanostructured Metal Oxide for Refractive Index Sensor

Directory of Open Access Journals (Sweden)

Shaymaa Riyadh Tahhan

2017-01-01

Full Text Available To increase the sensitivity of biosensor a new approach using an optical fiber Bragg grating (FBG coated with a suitable nanostructured metal oxide (NMO is proposed which is costly effective compared to other biosensors. Bragg grating was written on a D-shaped optical fiber by phase mask method using a 248 nm KrF excimer laser for a 5 min exposure time producing a grating with a period of 528 nm. Titanium dioxide (TiO2 nanostructured metal oxide was coated over the fiber for the purpose of increasing its sensing area. The etched D-shaped FBG was then coated with 312 nm thick TiO2 nanostructured layer to ensure propagating the radiation modes within the core. The final structure was used to sense deionized water and saline. The etched D-shaped FBG original sensitivity before coating to air-deionized water and to air-saline was 0.314 nm/riu and 0.142 nm/riu, respectively. After coating the sensitivity became 1.257 nm/riu for air-deionized water and 0.857 nm/riu for air-saline.

Monitoring the Como Railway Bridge based on dynamic FBG sensor system

Science.gov (United States)

Zhang, Jianzhong; Sun, Weimin; Peng, G. D.; Yuan, Libo

2007-07-01

A FBG-based dynamic strain sensor system, whose responding frequency and resolution can be high as 16Hz and ~1μɛ respectively, is described and the system is applied to monitor the dynamic strain of Como Railway Bridge in Australia. The results of one-month long measurement show that the system can figure out all dynamic strain caused by passed trains and also prove the stability of the sensor system.

Guided wave and damage detection in composite laminates using different fiber optic sensors.

Science.gov (United States)

Li, Fucai; Murayama, Hideaki; Kageyama, Kazuro; Shirai, Takehiro

2009-01-01

Guided wave detection using different fiber optic sensors and their applications in damage detection for composite laminates were systematically investigated and compared in this paper. Two types of fiber optic sensors, namely fiber Bragg gratings (FBG) and Doppler effect-based fiber optic (FOD) sensors, were addressed and guided wave detection systems were constructed for both types. Guided waves generated by a piezoelectric transducer were propagated through a quasi-isotropic carbon fiber reinforced plastic (CFRP) laminate and acquired by these fiber optic sensors. Characteristics of these fiber optic sensors in ultrasonic guided wave detection were systematically compared. Results demonstrated that both the FBG and FOD sensors can be applied in guided wave and damage detection for the CFRP laminates. The signal-to-noise ratio (SNR) of guided wave signal captured by an FOD sensor is relatively high in comparison with that of the FBG sensor because of their different physical principles in ultrasonic detection. Further, the FOD sensor is sensitive to the damage-induced fundamental shear horizontal (SH(0)) guided wave that, however, cannot be detected by using the FBG sensor, because the FOD sensor is omnidirectional in ultrasound detection and, in contrast, the FBG sensor is severely direction dependent.

Vibration monitoring for aircraft wing model using fiber Bragg grating array packaged by vacuum-assisted resin transfer molding

Science.gov (United States)

Zhang, Wen; Liu, Xiaolong; He, Wei; Dong, Mingli; Zhu, Lianqing

2017-09-01

For the improvement of monitoring accuracy, a vibration monitoring for aircraft wing model using a fiber Bragg grating (FBG) array packaged by vacuum-assisted resin transfer molding (VARTM) is proposed. The working principle of the vibration monitoring using FBG array has been explained, which can theoretically support the idea of this paper. VARTM has been explained in detail, which is suitable for not only the single FBG sensor but also the FBG array within a relatively large area. The calibration experiment has been performed using the FBG sensor packaged by VARTM. The strain sensitivity of the VARTM package is 1.35 pm/μɛ and the linearity is 0.9999. The vibration monitoring experiment has been carried out using FBG array packaged by VARTM. The measured rate of strain changes across the aluminum test board used to simulate the aircraft wing is 0.69 μɛ/mm and the linearity is 0.9931. The damping ratio is 0.16, which could be further used for system performance evaluation. Experimental results demonstrate that the vibration monitoring using FBG sensors packaged by VARTM can be efficiently used for the structural health monitoring. Given the validation and great performance, this method is quite promising for in-flight monitoring and holds great reference value in other similar engineering structures.

Fiber Bragg Grating Based pH Sensor

Science.gov (United States)

Yulianti, Ian; Sahmah, Abu; Supa'at, M.; Idrus, M.; Kassim, Norazan M.; Al-hetar, Abdulaziz M.

2011-05-01

This paper demonstrates the modeling of pH sensor based on pH sensitive hydrogel coated FBG. The modeling was done by simulating the hydrogel swelling behavior, then calculating the strain induced by hydrogel expansion. Meshless numerical method was adopted to solve the Poison Nernst Planck equation coupled to mechanical equation to simulate the hydrogel swelling. The strain induced in the FBG due to mechanical expansion of hydrogel was calculated analytically. Strain of more than 10 μɛ was obtained at pH> 5. At pH of 5, λB shift of more than 10 pm was achieved.

Bandwidth-Tunable Fiber Bragg Gratings Based on UV Glue Technique

Science.gov (United States)

Fu, Ming-Yue; Liu, Wen-Feng; Chen, Hsin-Tsang; Chuang, Chia-Wei; Bor, Sheau-Shong; Tien, Chuen-Lin

2007-07-01

In this study, we have demonstrated that a uniform fiber Bragg grating (FBG) can be transformed into a chirped fiber grating by a simple UV glue adhesive technique without shifting the reflection band with respect to the center wavelength of the FBG. The technique is based on the induced strain of an FBG due to the UV glue adhesive force on the fiber surface that causes a grating period variation and an effective index change. This technique can provide a fast and simple method of obtaining the required chirp value of a grating for applications in the dispersion compensators, gain flattening in erbium-doped fiber amplifiers (EDFAs) or optical filters.

Compact and cost-effective multi-channel optical spectrometer for fine FBG sensing in IoT technology

Science.gov (United States)

Konishi, Tsuyoshi; Yamasaki, Yu

2018-02-01

Optical fiber sensor networks have attracted much attention in IoT technology and a fiber Bragg grating is one of key sensor devices there because of their advantages in a high affinity for optical fiber networks, compactness, immunity to electromagnetic interference and so on. Nevertheless, its sensitivity is not always satisfactory so as to be usable together with widespread cost-effective multi-channel spectrometers. In this paper, we introduce a new cost-effective approach for a portable multi-channel spectrometer with high spectral resolution and demonstrates some preliminary experimental results for fine FBG sensing.

Dynamic Error Analysis Method for Vibration Shape Reconstruction of Smart FBG Plate Structure

Directory of Open Access Journals (Sweden)

Hesheng Zhang

2016-01-01

Full Text Available Shape reconstruction of aerospace plate structure is an important issue for safe operation of aerospace vehicles. One way to achieve such reconstruction is by constructing smart fiber Bragg grating (FBG plate structure with discrete distributed FBG sensor arrays using reconstruction algorithms in which error analysis of reconstruction algorithm is a key link. Considering that traditional error analysis methods can only deal with static data, a new dynamic data error analysis method are proposed based on LMS algorithm for shape reconstruction of smart FBG plate structure. Firstly, smart FBG structure and orthogonal curved network based reconstruction method is introduced. Then, a dynamic error analysis model is proposed for dynamic reconstruction error analysis. Thirdly, the parameter identification is done for the proposed dynamic error analysis model based on least mean square (LMS algorithm. Finally, an experimental verification platform is constructed and experimental dynamic reconstruction analysis is done. Experimental results show that the dynamic characteristics of the reconstruction performance for plate structure can be obtained accurately based on the proposed dynamic error analysis method. The proposed method can also be used for other data acquisition systems and data processing systems as a general error analysis method.

Bragg gratings: Optical microchip sensors

Science.gov (United States)

Watts, Sam

2010-07-01

A direct UV writing technique that can create multiple Bragg gratings and waveguides in a planar silica-on-silicon chip is enabling sensing applications ranging from individual disposable sensors for biotechnology through to multiplexed sensor networks in pharmaceutical manufacturing.

Robust tracking of dexterous continuum robots: Fusing FBG shape sensing and stereo vision.

Science.gov (United States)

Rumei Zhang; Hao Liu; Jianda Han

2017-07-01

Robust and efficient tracking of continuum robots is important for improving patient safety during space-confined minimally invasive surgery, however, it has been a particularly challenging task for researchers. In this paper, we present a novel tracking scheme by fusing fiber Bragg grating (FBG) shape sensing and stereo vision to estimate the position of continuum robots. Previous visual tracking easily suffers from the lack of robustness and leads to failure, while the FBG shape sensor can only reconstruct the local shape with integral cumulative error. The proposed fusion is anticipated to compensate for their shortcomings and improve the tracking accuracy. To verify its effectiveness, the robots' centerline is recognized by morphology operation and reconstructed by stereo matching algorithm. The shape obtained by FBG sensor is transformed into distal tip position with respect to the camera coordinate system through previously calibrated registration matrices. An experimental platform was set up and repeated tracking experiments were carried out. The accuracy estimated by averaging the absolute positioning errors between shape sensing and stereo vision is 0.67±0.65 mm, 0.41±0.25 mm, 0.72±0.43 mm for x, y and z, respectively. Results indicate that the proposed fusion is feasible and can be used for closed-loop control of continuum robots.

Fiber-Optic Thermal Sensor for TiN Film Crack Monitoring

Directory of Open Access Journals (Sweden)

Hsiang-Chang Hsu

2017-11-01

Full Text Available The study focuses on the thermal and temperature sensitivity behavior of an optical fiber sensor device. In this article, a titanium nitride (TiN-coated fiber Bragg grating (FBG sensor fabricated using an ion beam sputtering system was investigated. The reflection spectra of the FBG sensor were tested using R-soft optical software to simulate the refractive index sensitivity. In these experiments, the temperature sensitivity of the TiN FBG was measured at temperatures ranging from 100 to 500 °C using an optical spectrum analyzer (OSA. The results showed that the temperature sensitivity of the proposed TiN FBG sensor reached 12.8 pm/°C for the temperature range of 100 to 300 °C and 20.8 pm/°C for the temperature range of 300 to 500 °C. Additionally, we found that the produced oxidation at temperatures of 400-500 °C caused a crack, with the crack becoming more and more obvious at higher and higher temperatures.

Reliability evaluation of fiber optic sensors exposed to cyclic thermal load

Energy Technology Data Exchange (ETDEWEB)

Kim, Heon Young; Kim, Dong Hoon [Advanced Materials Research Team, Korea Railroad Research Institute, Uiwang (Korea, Republic of); Kim, Dae Hyun [Dept. of Mechanical and Automotive Engineering, Seoul National University of Science and Technology, Seoul (Korea, Republic of)

2016-06-15

Fiber Bragg grating (FBG) sensors are currently the most prevalent sensors because of their unique advantages such as ease of multiplexing and capability of performing absolute measurements. They are applied to various structures for structural health monitoring (SHM). The signal characteristics of FBG sensors under thermal loading should be investigated to enhance the reliability of these sensors, because they are exposed to certain cyclic thermal loads due to temperature changes resulting from change of seasons, when they are applied to structures for SHM. In this study, tests on specimens are conducted in a thermal chamber with temperature changes from - to for 300 cycles. For the specimens, two types of base materials and adhesives that are normally used in the manufacture of packaged FBG sensors are selected. From the test results, it is confirmed that the FBG sensors undergo some degree of compressive strain under cyclic thermal load; this can lead to measurement errors. Hence, a pre-calibration is necessary before applying these sensors to structures for long-term SHM.

Test and Evaluation of Fiber Optic Sensors for High-Radiation Space Nuclear Power Applications

International Nuclear Information System (INIS)

Klemer, Daniel; Fielder, Robert S.; Stinson-Bagby, Kelly L.

2004-01-01

Fiber optic sensors can be used to measure a number of parameters, including temperature, strain, pressure and flow, for instrumentation and control of space nuclear power systems. In the past, this technology has often been rejected for use in such a high-radiation environment based on early experiments that revealed a number of degradation phenomena, including radiation-induced fiber attenuation, or 'graying', and Fiber Bragg Grating (FBG) fading and wavelength shift. However, this paper reports the results of recent experimental testing that demonstrates readability of fiber optic sensors to extremely high levels of neutron and gamma radiation. Both distributed Fiber Bragg Grating (FBG) sensors and single-point Extrinsic Fabry Perot Interferometer (EFPI) sensors were continuously monitored over a 2-month period, during which they were exposed to combined neutron and gamma radiation in both in-core and ex-core positions within a nuclear reactor. Total exposure reached approximately 2 x 10 19 cm -2 fast neutron (E > 1 MeV) fluence and 8.7 x 10 8 Gy gamma for in-core sensors. FBG sensors were interrogated using a standard Luna Innovations FBG measurement system, which is based on optical frequency-domain reflectometer (OFDR) technology. Approximately 74% of the 19 FBG sensors located at the core centerline in the in-core position exhibited sufficient signal-to-noise ratio (SNR) to remain readable even after receiving the maximum dose. EFPI sensors were spectrally interrogated using a broadband probe source operating in the 830 nm wavelength region. While these single-point sensors failed early in the test, important additional fiber spectral transmission data was collected, which indicates that interrogation of EFPI sensors in alternate wavelength regions may allow significant improvement in sensor longevity for operation in high-radiation environments. This work was funded through a Small Business Innovative Research (SBIR) contract with the Nasa Glenn Research

Deformation Monitoring for Chinese Traditional Timber Buildings Using Fiber Bragg Grating Sensors

Directory of Open Access Journals (Sweden)

Ni-Lei Li

2018-06-01

Full Text Available The Fiber Bragg Grating (FBG sensing technique is suitable for a wide variety of measurements, including temperature, pressure, acceleration, liquid level, etc., and has been applied to many bridges and buildings in the past two decades. The fact that the FBG technique can only monitor and measure strain data for most cases when it is used for deformation measurements impedes application of the FBG sensing technique in civil infrastructures. This paper proposes FBG sensing-based deformation monitoring methods that are applicable to monitoring beam deflection, column inclination angle and mortise-tenon joint dislocation for Chinese traditional timber structures. On the basis of improved conjugated beam theory and geometrical trigonometric function relationship, the relationships between the FBG sensing strain values and the deflection of beam, inclination angle of column, as well as the amount of dislocation of mortise-tenon joint are deducted for Chinese traditional buildings. A series of experiments were conducted to verify the applicability and effectiveness of the proposed deformation monitoring methods. The results show that a good agreement is obtained between the values given by the methods proposed in this paper and other methods. This implies that the proposed deformation monitoring methods are applicable and effective in the health monitoring of Chinese traditional timber structures.

A novel method for length of chirped fiber Bragg grating sensor

Science.gov (United States)

Li, Zhenwei; Wei, Peng; Liu, Taolin

2018-03-01

Length of chirped fiber Bragg grating sensor is very important for detonation velocity. Different from other ways, we proposed a novel method based on the optical frequency domain reflection theory to measure the length of chirped fiber grating sensor in non-contact condition. This method adopts a tunable laser source to provide wavelength scanning laser, which covers the Full Width at Half Maximum of spectrum of the chirped fiber Bragg grating sensor. A Michelson interferometer is used to produce optical interference signal. Finally, the grating's length is attainable by distance domain signal. In theory, length resolution of chirped fiber Bragg grating sensor could be 0.02 mm. We perform a series of length measurement experiments for chirped fiber grating sensor, including comparison experiments with hot-tip method. And the experiment results show that the novel method could accurately measure the length of chirped fiber Bragg grating sensors, and the length differences between the optical frequency domain reflection method and the hot-tip probe method are very small.

An armored-cable-based fiber Bragg grating sensor array for perimeter fence intrusion detection

Science.gov (United States)

Hao, Jianzhong; Dong, Bo; Varghese, Paulose; Phua, Jiliang; Foo, Siang Fook

2012-01-01

In this paper, an armored-cable-based optical fiber Bragg grating (FBG) sensor array, for perimeter fence intrusion detection, is demonstrated and some of the field trial results are reported. The field trial was conducted at a critical local installation in Singapore in December 2010. The sensor array was put through a series of both simulated and live intrusion scenarios to test the stability and suitability of operation in the local environmental conditions and to determine its capabilities in detecting and reporting these intrusions accurately to the control station. Such a sensor array can provide perimeter intrusion detection with fine granularity and preset pin-pointing accuracy. The various types of intrusions included aided or unaided climbs, tampering and cutting of the fence, etc. The unique sensor packaging structure provides high sensitivity, crush resistance and protection against rodents. It is also capable of resolving nuisance events such as rain, birds sitting on the fence or seismic vibrations. These sensors are extremely sensitive with a response time of a few seconds. They can be customized for a desired spatial resolution and pre-determined sensitivity. Furthermore, it is easy to cascade a series of such sensors to monitor and detect intrusion events over a long stretch of fence line. Such sensors can be applied to real-time intrusion detection for perimeter security, pipeline security and communications link security.

Phase-shifted fiber Bragg grating inscription by fusion splicing technique and femtosecond laser

Science.gov (United States)

Jiang, Yajun; Yuan, Yuan; Xu, Jian; Yang, Dexing; Li, Dong; Wang, Meirong; Zhao, Jianlin

2016-11-01

A new method for phase-shifted fiber Bragg grating (PS-FBG) inscription in single mode fiber by fusion splicing technique and femtosecond laser is presented. The PS-FBG is produced by exposing the fusion spliced fiber with femtosecond laser through a uniform phase mask. The transmission spectrum of the PS-FBG shows a nonlinear red shift during the inscription process, and two or three main dips can be observed due to the formation of one or two FBG-based Fabry-Pérot structures by controlling the exposure intensity and time of the laser. For a peak power density of 4.8×1013 W/cm2, the induced refractive index modulation can reach to 6.3×10-4 in the fiber without sensitization. The PS-FBG's temperature, strain and pressure characteristics are also experimentally studied. These PS-FBGs can be potentially used for multiple wavelength fiber lasers, filters and optical fiber sensors.

Conception and preliminary evaluation of an optical fibre sensor for simultaneous measurement of pressure and temperature

International Nuclear Information System (INIS)

Bremer, K; Moss, B; Leen, G; Mueller, I; Lewis, E; Lochmann, S

2009-01-01

This paper presents a novel concept of simultaneously measuring pressure and temperature using a silica optical fibre extrinsic Fabry-Perot interferometric (EFPI) pressure sensor incorporating a fibre Bragg grating (FBG), which is constructed entirely from fused-silica. The novel device is used to simultaneously provide accurate pressure and temperature readings at the point of measurement. Furthermore, the FBG temperature measurement is used to eliminate the temperature cross-sensitivity of the EFPI pressure sensor.

High Pressure Sensing and Dynamics Using High Speed Fiber Bragg Grating Interrogation Systems

Energy Technology Data Exchange (ETDEWEB)

Rodriguez, G. [LANL; Sandberg, R. L. [LANL; Lalone, B. M. [NSTec; Marshall, B. R. [NSTec; Grover, M. [NSTec; Stevens, G. D. [NSTec; Udd, E. [Columbia Gorge Research

2014-06-01

Fiber Bragg gratings (FBGs) are developing into useful sensing tools for measuring high pressure dynamics in extreme environments under shock loading conditions. Approaches using traditional diode array coupled FBG interrogation systems are often limited to readout speeds in the sub-MHz range. For shock wave physics, required detection speeds approaching 100 MHz are desired. We explore the use of two types of FBG sensing systems that are aimed at applying this technology as embedded high pressure probes for transient shock events. Both approaches measure time resolved spectral shifts in the return light from short (few mm long) uniform FBGs at 1550 nm. In the first approach, we use a fiber coupled spectrometer to demultiplex spectral channels into an array (up to 12) of single element InGaAs photoreceivers. By monitoring the detectors during a shock impact event with high speed recording, we are able to track the pressure induced spectral shifting in FBG down to a time resolution of 20 ns. In the second approach, developed at the Special Technologies Lab, a coherent mode-locked fiber laser is used to illuminate the FBG sensor. After the sensor, wavelength-to-time mapping is accomplished with a chromatic dispersive element, and entire spectra are sampled using a single detector at the modelocked laser repetition rate of 50 MHz. By sampling with a 12 GHz InGaAs detector, direct wavelength mapping in time is recorded, and the pressure induced FBG spectral shift is sampled at 50 MHz. Here, the sensing systems are used to monitor the spectral shifts of FBGs that are immersed into liquid water and shock compressed using explosives. In this configuration, the gratings survive to pressures approaching 50 kbar. We describe both approaches and present the measured spectral shifts from the shock experiments.

High pressure sensing and dynamics using high speed fiber Bragg grating interrogation systems

Science.gov (United States)

Rodriguez, G.; Sandberg, R. L.; Lalone, B. M.; Marshall, B. R.; Grover, M.; Stevens, G.; Udd, E.

2014-06-01

Fiber Bragg gratings (FBGs) are developing into useful sensing tools for measuring high pressure dynamics in extreme environments under shock loading conditions. Approaches using traditional diode array coupled FBG interrogation systems are often limited to readout speeds in the sub-MHz range. For shock wave physics, required detection speeds approaching 100 MHz are desired. We explore the use of two types of FBG sensing systems that are aimed at applying this technology as embedded high pressure probes for transient shock events. Both approaches measure time resolved spectral shifts in the return light from short (few mm long) uniform FBGs at 1550 nm. In the first approach, we use a fiber coupled spectrometer to demultiplex spectral channels into an array (up to 12) of single element InGaAs photoreceivers. By monitoring the detectors during a shock impact event with high speed recording, we are able to track the pressure induced spectral shifting in FBG down to a time resolution of 20 ns. In the second approach, developed at the Special Technologies Lab, a coherent mode-locked fiber laser is used to illuminate the FBG sensor. After the sensor, wavelength-to-time mapping is accomplished with a chromatic dispersive element, and entire spectra are sampled using a single detector at the modelocked laser repetition rate of 50 MHz. By sampling with a 12 GHz InGaAs detector, direct wavelength mapping in time is recorded, and the pressure induced FBG spectral shift is sampled at 50 MHz. Here, the sensing systems are used to monitor the spectral shifts of FBGs that are immersed into liquid water and shock compressed using explosives. In this configuration, the gratings survive to pressures approaching 50 kbar. We describe both approaches and present the measured spectral shifts from the shock experiments.

Highly birefringent phase-shifted fiber Bragg gratings inscribed with femtosecond laser.

Science.gov (United States)

He, Jun; Wang, Yiping; Liao, Changrui; Wang, Qiaoni; Yang, Kaiming; Sun, Bing; Yin, Guolu; Liu, Shen; Zhou, Jiangtao; Zhao, Jing

2015-05-01

We demonstrate a highly birefringent phase-shifted fiber Bragg grating (PS-FBG) inscribed in H2-free fiber with a near-infrared femtosecond Gaussian laser beam and uniform phase mask. The PS-FBG was fabricated from an ordinary fiber Bragg grating (FBG) in a case in which overexposure was applied. The spectral evolution from FBG to FS-FBG was observed experimentally with a decrease in transmission loss at dip wavelength, blueshift of the dip wavelength, decrease in the cladding mode loss, and an increase in the insertion loss. A high birefringence was demonstrated experimentally with the existence of PS-FBG only in TM polarization. The formation of the PS-FBG may be due to a negative index change induced by the higher intensity in the center of the Gaussian laser beam.

Review of High-Speed Fiber Optic Grating Sensors Systems

Energy Technology Data Exchange (ETDEWEB)

Udd, E; Benterou, J; May, C; Mihailov, S J; Lu, P

2010-03-24

Fiber grating sensors can be used to support a wide variety of high speed measurement applications. This includes measurements of vibrations on bridges, traffic monitoring on freeways, ultrasonic detection to support non-destructive tests on metal plates and providing details of detonation events. This paper provides a brief overview of some of the techniques that have been used to support high speed measurements using fiber grating sensors over frequency ranges from 10s of kHz, to MHZ and finally toward frequencies approaching the GHz regime. Very early in the development of fiber grating sensor systems it was realized that a high speed fiber grating sensor system could be realized by placing an optical filter that might be a fiber grating in front of a detector so that spectral changes in the reflection from a fiber grating were amplitude modulated. In principal the only limitation on this type of system involved the speed of the output detector which with the development of high speed communication links moved from the regime of 10s of MHz toward 10s of GHz. The earliest deployed systems involved civil structures including measurements of the strain fields on composite utility poles and missile bodies during break tests, bridges and freeways. This was followed by a series of developments that included high speed fiber grating sensors to support nondestructive testing via ultrasonic wave detection, high speed machining and monitoring ship hulls. Each of these applications involved monitoring mechanical motion of structures and thus interest was in speeds up to a few 10s of MHz. Most recently there has been interest in using fiber grating to monitor the very high speed events such as detonations and this has led to utilization of fiber gratings that are consumed during an event that may require detection speeds of hundreds of MHz and in the future multiple GHz.

Field tests of Fibre Bragg Grating sensors incorporated into CFRP for Railway Bridge strengthening condition monitoring

DEFF Research Database (Denmark)

Täljsten, Björn; Kerrouche, Abdelfathe; Leighton, J

2008-01-01

made with the FBG- based system were found to be in agreement with the changes expected in the structure (together with the embedded reinforcement), produced by the loading applied. The study has demonstrated the successful use of FBG-based technology pre-mounted in ‘smart’ carbon fiber composite...... project ‘Sustainable Bridges’. The FBG sensors were embedded in Carbon Fibre Reinforced Polymers (CFRP) rods incorporated into grooves specially created in the concrete cover of the bridge structure and interrogated using a compact system based on Wavelength Division Multiplexing (WDM). Throughout...... the study, the FBG sensors were continuously monitored, allowing the incremental increases in the strain to be seen and through the yield point of the carbon composite reinforcement. The sensors were able to follow the resulting induced changes in strain of over a range in excess of 4000µε. The measurements...

Underwater Acoustic Sensors Based on Fiber Bragg Gratings

Directory of Open Access Journals (Sweden)

Giuseppe Parente

2009-06-01

Full Text Available We report on recent results obtained with a fiber optic hydrophone based on the intensity modulation of the laser light in a FBG (Fiber Bragg Grating under the influence of the sound pressure. In order to control the behavior of the hydrophone in terms of sensitivity and bandwidth, FBGs have been coated with proper materials, characterized by different elastic modulus and shapes. In particular, new experiments have been carried out using a cylindrical geometry with two different coating, showing that the sensitivity is not influenced by the shape but by the transversal dimension and the material characteristics of the coating.

Fiber Bragg Grating Temperature Sensors in a 6.5-MW Generator Exciter Bridge and the Development and Simulation of Its Thermal Model

Directory of Open Access Journals (Sweden)

Kleiton de Morais Sousa

2014-09-01

Full Text Available This work reports the thermal modeling and characterization of a thyristor. The thyristor is used in a 6.5-MW generator excitation bridge. Temperature measurements are performed using fiber Bragg grating (FBG sensors. These sensors have the benefits of being totally passive and immune to electromagnetic interference and also multiplexed in a single fiber. The thyristor thermal model consists of a second order equivalent electric circuit, and its power losses lead to an increase in temperature, while the losses are calculated on the basis of the excitation current in the generator. Six multiplexed FBGs are used to measure temperature and are embedded to avoid the effect of the strain sensitivity. The presented results show a relationship between field current and temperature oscillation and prove that this current can be used to determine the thermal model of a thyristor. The thermal model simulation presents an error of 1.5 °C, while the FBG used allows for the determination of the thermal behavior and the field current dependence. Since the temperature is a function of the field current, the corresponding simulation can be used to estimate the temperature in the thyristors.

Fiber Bragg grating temperature sensors in a 6.5-MW generator exciter bridge and the development and simulation of its thermal model.

Science.gov (United States)

de Morais Sousa, Kleiton; Probst, Werner; Bortolotti, Fernando; Martelli, Cicero; da Silva, Jean Carlos Cardozo

2014-09-05

This work reports the thermal modeling and characterization of a thyristor. The thyristor is used in a 6.5-MW generator excitation bridge. Temperature measurements are performed using fiber Bragg grating (FBG) sensors. These sensors have the benefits of being totally passive and immune to electromagnetic interference and also multiplexed in a single fiber. The thyristor thermal model consists of a second order equivalent electric circuit, and its power losses lead to an increase in temperature, while the losses are calculated on the basis of the excitation current in the generator. Six multiplexed FBGs are used to measure temperature and are embedded to avoid the effect of the strain sensitivity. The presented results show a relationship between field current and temperature oscillation and prove that this current can be used to determine the thermal model of a thyristor. The thermal model simulation presents an error of 1.5 °C, while the FBG used allows for the determination of the thermal behavior and the field current dependence. Since the temperature is a function of the field current, the corresponding simulation can be used to estimate the temperature in the thyristors.

Performance assessment of indigenously developed FBG strain ...

Indian Academy of Sciences (India)

Use of FBG sensors for real time health monitoring of various civil engineering structures is well-established in western world since last decade, whereas in the Indian context this technology is still in a nascent stage. In this paper, performance assessment of indigenously developed FBG sensors for the application of health ...

Strain and temperature measurement in pultrusion processes by fiber Bragg grating sensors

Science.gov (United States)

Tucci, Fausto; Rubino, Felice; Carlone, Pierpaolo

2018-05-01

Injection Pultrusion (IP) is one of the most effective processes, in terms of productivity and costs, to manufacture fiber reinforced polymers. In IP roving of fiber are driven through an injection chamber in which they are impregnated by the resin and then formed in a shaped die. The die is heated in order to cure the resin. Pultruded products are in most cases characterized by constant cross-section profile, whereas unidirectional long fibers are mainly used as reinforcing material. Two relevant phenomena occur within the injection chamber and the heated die, namely the impregnation of the fibers and the polymerization of the resin. Furthermore, thermal expansion, resin chemical shrinkage and the interaction between the die and the impregnated fibers strongly influence the process [1]. Clearly, thermal and mechanical fields significantly impact on these strictly chained behaviours. The use of thermocouples to evaluate temperature within pultrusion die is already widespread, but they are not capable to acquire any information concerning stress-strain levels. In the present work Fibers Bragg Gratings (FBG) sensors were used to measure thermal and strain profiles in selected material location within the injection chamber and the curing die. Being the differences among the spectres transmitted and received are related to the variations in both temperature and strain, commercial FBG sensors were opportunely modified and calibrated. The optical fibers were hooked to the fibers entering into the injection pultrusion die. Taking the pulling speed into account, each waveform acquired was correlated to a position within the die. Obtained data highlight the effect of the heat generation due to resin reaction as well as longitudinal strains related to the pulling force, the thermal expansion and the chemical shrinkage of the resin system.

Fibre gratings for high temperature sensor applications

Science.gov (United States)

Canning, J.; Sommer, K.; Englund, M.

2001-07-01

Phosphosilicate fibre gratings can be stabilized at temperatures in excess of 500 °C for sensor applications by optimizing thermal and UV presensitization recipes. Furthermore, the use of 193 nm presensitization prevents the formation of OH absorption bands, extending the use of fibre gratings across the entire wavelength spectrum. Gratings for operation at 700 °C retaining up to 70% reflectivity after 30 min are demonstrated.

Dynamic strain measurement of hydraulic system pipeline using fibre Bragg grating sensors

Directory of Open Access Journals (Sweden)

Qiang Wang

2016-04-01

Full Text Available Fatigue failure is a serious problem in hydraulic piping systems installed in the machinery and equipment working in harsh operational conditions. To alleviate this problem, health monitoring of pipes can be conducted by measuring and analysing vibration-induced strain. Fibre Bragg grating is considered as a promising sensing approach for dynamic load monitoring. In this article, dynamic strain measurements based on fibre Bragg grating sensors for small-bore metal pipes have been investigated. The quasi-distributed strain sensing of fibre Bragg grating sensors is introduced. Two comparison experiments were carried out under vibration and impact loads among the methods of electrical strain gauge, piezoelectric accelerometer and fibre Bragg grating sensor. Experimental results indicate that fibre Bragg grating sensor possesses an outstanding ability to resist electromagnetic interference compared with strain gauge. The natural frequency measurement results, captured by fibre Bragg grating sensor, agree well with the modal analysis results obtained from finite element analysis. In addition, the attached fibre Bragg grating sensor brings a smaller impact on the dynamic characteristics of the measured pipe than the accelerometer due to its small size and lightweight. Fibre Bragg grating sensors have great potential for the quasi-distributed measurement of dynamic strain for the dynamic characteristic research and health monitoring of hydraulic system pipeline.

The Use of Fiber Bragg Grating Sensors in Biomechanics and Rehabilitation Applications: The State-of-the-Art and Ongoing Research Topics

Science.gov (United States)

Al-Fakih, Ebrahim; Osman, Noor Azuan Abu; Adikan, Faisal Rafiq Mahamd

2012-01-01

In recent years, fiber Bragg gratings (FBGs) are becoming increasingly attractive for sensing applications in biomechanics and rehabilitation engineering due to their advantageous properties like small size, light weight, biocompatibility, chemical inertness, multiplexing capability and immunity to electromagnetic interference (EMI). They also offer a high-performance alternative to conventional technologies, either for measuring a variety of physical parameters or for performing high-sensitivity biochemical analysis. FBG-based sensors demonstrated their feasibility for specific sensing applications in aeronautic, automotive, civil engineering structure monitoring and undersea oil exploration; however, their use in the field of biomechanics and rehabilitation applications is very recent and its practicality for full-scale implementation has not yet been fully established. They could be used for detecting strain in bones, pressure mapping in orthopaedic joints, stresses in intervertebral discs, chest wall deformation, pressure distribution in Human Machine Interfaces (HMIs), forces induced by tendons and ligaments, angles between body segments during gait, and many others in dental biomechanics. This article aims to provide a comprehensive overview of all the possible applications of FBG sensing technology in biomechanics and rehabilitation and the status of ongoing researches up-to-date all over the world, demonstrating the FBG advances over other existing technologies. PMID:23201977

The Use of Fiber Bragg Grating Sensors in Biomechanics and Rehabilitation Applications: The State-of-the-Art and Ongoing Research Topics

Directory of Open Access Journals (Sweden)

Faisal Rafiq Mahamd Adikan

2012-09-01

Full Text Available In recent years, fiber Bragg gratings (FBGs are becoming increasingly attractive for sensing applications in biomechanics and rehabilitation engineering due to their advantageous properties like small size, light weight, biocompatibility, chemical inertness, multiplexing capability and immunity to electromagnetic interference (EMI. They also offer a high-performance alternative to conventional technologies, either for measuring a variety of physical parameters or for performing high-sensitivity biochemical analysis. FBG-based sensors demonstrated their feasibility for specific sensing applications in aeronautic, automotive, civil engineering structure monitoring and undersea oil exploration; however, their use in the field of biomechanics and rehabilitation applications is very recent and its practicality for full-scale implementation has not yet been fully established. They could be used for detecting strain in bones, pressure mapping in orthopaedic joints, stresses in intervertebral discs, chest wall deformation, pressure distribution in Human Machine Interfaces (HMIs, forces induced by tendons and ligaments, angles between body segments during gait, and many others in dental biomechanics. This article aims to provide a comprehensive overview of all the possible applications of FBG sensing technology in biomechanics and rehabilitation and the status of ongoing researches up-to-date all over the world, demonstrating the FBG advances over other existing technologies.

Tunable Fiber Bragg Grating Ring Lasers using Macro Fiber Composite Actuators

Science.gov (United States)

Geddis, Demetris L.; Allison, Sidney G.; Shams, Qamar A.

2006-01-01

The research reported herein includes the fabrication of a tunable optical fiber Bragg grating (FBG) fiber ring laser (FRL)1 from commercially available components as a high-speed alternative tunable laser source for NASA Langley s optical frequency domain reflectometer (OFDR) interrogator, which reads low reflectivity FBG sensors. A Macro-Fiber Composite (MFC) actuator invented at NASA Langley Research Center (LaRC) was selected to tune the laser. MFC actuators use a piezoelectric sheet cut into uniaxially aligned rectangular piezo-fibers surrounded by a polymer matrix and incorporate interdigitated electrodes to deliver electric fields along the length of the piezo-fibers. This configuration enables MFC actuators to produce displacements larger than the original uncut piezoelectric sheet. The FBG filter was sandwiched between two MFC actuators, and when strained, produced approximately 3.62 nm of wavelength shift in the FRL when biasing the MFC actuators from 500 V to 2000 V. This tunability range is comparable to that of other tunable lasers and is adequate for interrogating FBG sensors using OFDR technology. Three different FRL configurations were studied. Configuration A examined the importance of erbium-doped fiber length and output coupling. Configuration B demonstrated the importance of the FBG filter. Configuration C added an output coupler to increase the output power and to isolate the filter. Only configuration C was tuned because it offered the best optical power output of the three configurations. Use of Plastic Optical Fiber (POF) FBG s holds promise for enhanced tunability in future research.

Three-axial Fiber Bragg Grating Strain Sensor for Volcano Monitoring

Science.gov (United States)

Giacomelli, Umberto; Beverini, Nicolò; Carbone, Daniele; Carelli, Giorgio; Francesconi, Francesco; Gambino, Salvatore; Maccioni, Enrico; Morganti, Mauro; Orazi, Massimo; Peluso, Rosario; Sorrentino, Fiodor

2017-04-01

Fiber optic and FBGs sensors have attained a large diffusion in the last years as cost-effective monitoring and diagnostic devices in civil engineering. However, in spite of their potential impact, these instruments have found very limited application in geophysics. In order to study earthquakes and volcanoes, the measurement of crustal deformation is of crucial importance. Stress and strain behaviour is among the best indicators of changes in the activity of volcanoes .. Deep bore-hole dilatometers and strainmeters have been employed for volcano monitoring. These instruments are very sensitive and reliable, but are not cost-effective and their installation requires a large effort. Fiber optic based devices offer low cost, small size, wide frequency band, easier deployment and even the possibility of creating a local network with several sensors linked in an array. We present the realization, installation and first results of a shallow-borehole (8,5 meters depth) three-axial Fiber Bragg Grating (FBG) strain sensor prototype. This sensor has been developed in the framework of the MED-SUV project and installed on Etna volcano, in the facilities of the Serra La Nave astrophysical observatory. The installation siteis about 7 Km South-West of the summit craters, at an elevation of about 1740 m. The main goal of our work is the realization of a three-axial device having a high resolution and accuracy in static and dynamic strain measurements, with special attention to the trade-off among resolution, cost and power consumption. The sensor structure and its read-out system are innovative and offer practical advantages in comparison with traditional strain meters. Here we present data collected during the first five months of operation. In particular, the very clear signals recorded in the occurrence of the Central Italy seismic event of October 30th demonstrate the performances of our device.

Structural Health Monitoring of Superconducting Magnets at CERN Using Fiber Bragg Grating Sensors

CERN Document Server

Chiuchiolo, A; Perez, J C; Bajas, H; Guinchard, M; Giordano, M; Breglio, G; Consales, M; Cusano, A

2014-01-01

The use of Fiber Bragg Grating sensors is becoming particularly challenging for monitoring different parameters in extreme operative conditions such as ultra-low temperatures, high electromagnetic fields and strong mechanical stresses. This work reports the use of the FBG for a new generation of accelerator magnets with the goal to develop an adequate sensing technology able to provide complementary or alternative information to the conventional strain gauges through the whole service life of the magnet. The study is focused on the mechanical performances of the magnet structure, which has to preserve the sensitive coils from any damage during the entire magnet fabrication process preventing even microscopic movements of the winding that can eventually initiate a transition from superconducting to normal conducting state of the material used (called in the specific literature as “quench”). The FBGs have been glued on the aluminium structure of two magnets prototypes by using an adhesive suitable for cryog...

Strain and high-temperature discrimination using a Type II fiber Bragg grating and a miniature fiber Fabry-Perot interferometer.

Science.gov (United States)

Jiang, Yajun; Yang, Dexing; Yuan, Yuan; Xu, Jian; Li, Dong; Zhao, Jianlin

2016-08-10

A novel method for simultaneous measurement of strain and high temperature using a Type II fiber Bragg grating (FBG) and a miniature fiber Fabry-Perot interferometer (MFFPI) is proposed. The MFFPI is produced by fusion splicing a short section of quartz capillary tube with two single-mode fibers, and then it is exposed by a focused femtosecond laser and a phase mask to inscribe a Type II FBG nearby. The reflection spectrum of this sensor is the superposition of the reflection spectrum of the FBG and the interference fringe of the MFFPI. This sensor shows perfect high-temperature and strain responses. Because of the different responses to the uniform variations of strain and temperature, by measuring the reflection peak of FBG and one of the interference dips of the MFFPI, strain and temperature can be simultaneously determined. The resolutions of this particular sensor in measuring strain and temperature are estimated to be ±8.4  μϵ and ±3.3°C, respectively, in the range from 0 to 1122 μϵ and from 23°C to 600°C.

Humidity Responsive Photonic Sensor based on a Carboxymethyl Cellulose Mechanical Actuator

OpenAIRE

Hartings, Matthew; Douglass, Kevin O.; Neice, Claire; Ahmed, Zeeshan

2017-01-01

We describe an intuitive and simple method for exploiting humidity-driven volume changes in carboxymethyl cellulose (CMC) to fabricate a humidity responsive actuator on a glass fiber substrate. We optimize this platform to generate a photonic-based humidity sensor where CMC coated on a fiber optic containing a fiber Bragg grating (FBG) actuates a mechanical strain in response to humidity changes. The humidity-driven mechanical deformation of the FBG results in a large lin...

Dense Wavelength Division (De Multiplexers Based on Fiber Bragg Gratings

Directory of Open Access Journals (Sweden)

S. BENAMEUR

2014-05-01

Full Text Available This study is to measure the impact of demultiplexers based on Fiber Bragg Grating (FBG filter on performance of DWDM system for optical access network. An optical transmission link has been established in which we have inserted a demultiplexer based on four different FBG filters. The first step will be the characterization of FBG’s filters (i.e. uniform FBG, Gaussian apodized Grating, chirped FBG to explain their behavior in the optical link. The simulations were conducted for different fiber’s lengths, filter bandwidth and different received power to get the best system performance. This helped to assess their impact on the link performance in terms of Bit Error Rate (BER.

A conductive grating sensor for online quantitative monitoring of fatigue crack

Science.gov (United States)

Li, Peiyuan; Cheng, Li; Yan, Xiaojun; Jiao, Shengbo; Li, Yakun

2018-05-01

Online quantitative monitoring of crack damage due to fatigue is a critical challenge for structural health monitoring systems assessing structural safety. To achieve online quantitative monitoring of fatigue crack, a novel conductive grating sensor based on the principle of electrical potential difference is proposed. The sensor consists of equidistant grating channels to monitor the fatigue crack length and conductive bars to provide the circuit path. An online crack monitoring system is established to verify the sensor's capability. The experimental results prove that the sensor is suitable for online quantitative monitoring of fatigue crack. A finite element model for the sensor is also developed to optimize the sensitivity of crack monitoring, which is defined by the rate of sensor resistance change caused by the break of the first grating channel. Analysis of the model shows that the sensor sensitivity can be enhanced by reducing the number of grating channels and increasing their resistance and reducing the resistance of the conductive bar.

Real-time temperature monitoring during radiofrequency treatments on ex-vivo animal model by fiber Bragg grating sensors

Science.gov (United States)

Palumbo, Giovanna; Tosi, Daniele; Schena, Emiliano; Massaroni, Carlo; Ippolito, Juliet; Verze, Paolo; Carlomagno, Nicola; Tammaro, Vincenzo; Iadicicco, Agostino; Campopiano, Stefania

2017-05-01

Fiber Bragg Grating (FBG) sensors applied to bio-medical procedures such as surgery and rehabilitation are a valid alternative to traditional sensing techniques due to their unique characteristics. Herein we propose the use of FBG sensor arrays for accurate real-time temperature measurements during multi-step RadioFrequency Ablation (RFA) based thermal tumor treatment. Real-time temperature monitoring in the RF-applied region represents a valid feedback for the success of the thermo-ablation procedure. In order to create a thermal multi-point map around the tumor area to be treated, a proper sensing configuration was developed. In particular, the RF probe of a commercial medical instrumentation, has been equipped with properly packaged FBGs sensors. Moreover, in order to discriminate the treatment areas to be ablated as precisely as possible, a second array 3.5 cm long, made by several FBGs was used. The results of the temperature measurements during the RFA experiments conducted on ex-vivo animal liver and kidney tissues are presented herein. The proposed FBGs based solution has proven to be capable of distinguish different and consecutive discharges and for each of them, to measure the temperature profile with a resolution of 0.1 °C and a minimum spatial resolution of 5mm. Based upon our experiments, it is possible to confirm that the temperature decreases with distance from a RF peak ablation, in accordance with RF theory. The proposed solution promises to be very useful for the surgeon because a real-time temperature feedback allows for the adaptation of RFA parameters during surgery and better delineates the area under treatment.

Self-Evaluation of PANDA-FBG Based Sensing System for Dynamic Distributed Strain and Temperature Measurement.

Science.gov (United States)

Zhu, Mengshi; Murayama, Hideaki; Wada, Daichi

2017-10-12

A novel method is introduced in this work for effectively evaluating the performance of the PANDA type polarization-maintaining fiber Bragg grating (PANDA-FBG) distributed dynamic strain and temperature sensing system. Conventionally, the errors during the measurement are unknown or evaluated by using other sensors such as strain gauge and thermocouples. This will make the sensing system complicated and decrease the efficiency since more than one kind of sensor is applied for the same measurand. In this study, we used the approximately constant ratio of primary errors in strain and temperature measurement and realized the self-evaluation of the sensing system, which can significantly enhance the applicability, as well as the reliability in strategy making.

A Fiber Bragg Grating—Bimetal Temperature Sensor for Solar Panel Inverters

Directory of Open Access Journals (Sweden)

Mohd Afiq Ismail

2011-09-01

Full Text Available This paper reports the design, characterization and implementation of a Fiber Bragg Grating (FBG-based temperature sensor for an Insulted-Gate Bipolar Transistor (IGBT in a solar panel inverter. The FBG is bonded to the higher Coefficient of Thermal Expansion (CTE side of a bimetallic strip to increase its sensitivity. Characterization results show a linear relationship between increasing temperature and the wavelength shift. It is found that the sensitivity of the sensor can be categorized into three characterization temperature regions between 26 °C and 90 °C. The region from 41 °C to 90 °C shows the highest sensitivity, with a value of 14 pm/°C. A new empirical model that considers both temperature and strain effects has been developed for the sensor. Finally, the FBG-bimetal temperature sensor is placed in a solar panel inverter and results confirm that it can be used for real-time monitoring of the IGBT temperature.

Enhancing thermal reliability of fiber-optic sensors for bio-inspired applications at ultra-high temperatures

Science.gov (United States)

Kang, Donghoon; Kim, Heon-Young; Kim, Dae-Hyun

2014-07-01

The rapid growth of bio-(inspired) sensors has led to an improvement in modern healthcare and human-robot systems in recent years. Higher levels of reliability and better flexibility, essential features of these sensors, are very much required in many application fields (e.g. applications at ultra-high temperatures). Fiber-optic sensors, and fiber Bragg grating (FBG) sensors in particular, are being widely studied as suitable sensors for improved structural health monitoring (SHM) due to their many merits. To enhance the thermal reliability of FBG sensors, thermal sensitivity, generally expressed as αf + ξf and considered a constant, should be investigated more precisely. For this purpose, the governing equation of FBG sensors is modified using differential derivatives between the wavelength shift and the temperature change in this study. Through a thermal test ranging from RT to 900 °C, the thermal sensitivity of FBG sensors is successfully examined and this guarantees thermal reliability of FBG sensors at ultra-high temperatures. In detail, αf + ξf has a non-linear dependence on temperature and varies from 6.0 × 10-6 °C-1 (20 °C) to 10.6 × 10-6 °C-1 (650 °C). Also, FBGs should be carefully used for applications at ultra-high temperatures due to signal disappearance near 900 °C.

Low Loss Polycarbonate Polymer Optical Fiber for High Temperature FBG Humidity Sensing

DEFF Research Database (Denmark)

Woyessa, Getinet; Fasano, Andrea; Markos, Christos

2017-01-01

We report the fabrication and characterization of a polycarbonate (PC) microstructured polymer optical fiber (mPOF) Bragg grating (FBG) humidity sensor that can operate beyond 100°C. The PC preform, from which the fiber was drawn, was produced using an improved casting approach to reduce...... the attenuation of the fiber. The fiber loss was found reduced by a factor of two compared to the latest reported PC mPOF [20], holding the low loss record in PC based fibers. PC mPOFBG was characterized to humidity and temperature, and a relative humidity (RH) sensitivity of 7.31± 0.13 pm/% RH in the range 10...

Load Identification for a Cantilever Beam Based on Fiber Bragg Grating Sensors

Directory of Open Access Journals (Sweden)

Xuegang Song

2017-07-01

Full Text Available Load identification plays an important role in structural health monitoring, which aims at preventing structural failures. In order to identify load for linear systems and nonlinear systems, this paper presents methods to identify load for a cantilever beam based on dynamic strain measurement by Fiber Bragg Grating (FBG sensors. For linear systems, the proposed inverse method consists of Kalman filter with no load terms and a linear estimator. For nonlinear systems, the proposed inverse method consists of cubature Kalman filter (CKF with no load terms and a nonlinear estimator. In the process of load identification, the state equations of the beam structures are constructed by using the finite element method (FEM. Kalman filter or CKF is used to suppress noise. The residual innovation sequences, gain matrix, and innovation covariance generated by Kalman filter or CKF are used to identify a load. To prove the effectiveness of the proposed method, numerical simulations and experiments of the beam structures are employed and the results show that the method has an excellent performance.

The Packaging Technology Study on Smart Composite Structure Based on The Embedded FBG Sensor

Science.gov (United States)

Zhang, Youhong; Chang, Xinlong; Zhang, Xiaojun; He, Xiangyong

2018-03-01

It is convenient to carry out the health monitoring of the solid rocket engine composite shell based on the embedded FBG sensor. In this paper, the packaging technology using one-way fiber layer of prepreg fiberglass/epoxy resin was proposed. The proposed packaging process is simple, and the packaged sensor structure size is flexible and convenient to use, at the mean time, the packaged structure has little effect on the pristine composite material structure.

Test of Fibre Bragg Gratings samples under High Fast Neutrons Fluence

Directory of Open Access Journals (Sweden)

Cheymol G.

2018-01-01

The measurements show that for nearly all gratings the Bragg peak remains visible after the irradiation, and that Radiation Induced Bragg Wavelength Shifts (RI-BWSs vary from few pm (equivalent to an error of less than 1°C for a temperature sensor to nearly 1 nm (equivalent to 100°C depending of the FBG types. High RI-BWSs could indeed be expected when considering the huge refractive index variation and compaction of the bare fibre samples that have been measured by other techniques. Post writing thermal annealing is confirmed as a key parameter in order to obtain a more radiation tolerant FBG. Our results show that specific annealing regimes allow making FGBs suitable to perform temperature measurements in a MTR experiment.

Study of Optical Fiber Sensors for Cryogenic Temperature Measurements.

Science.gov (United States)

De Miguel-Soto, Veronica; Leandro, Daniel; Lopez-Aldaba, Aitor; Beato-López, Juan Jesus; Pérez-Landazábal, José Ignacio; Auguste, Jean-Louis; Jamier, Raphael; Roy, Philippe; Lopez-Amo, Manuel

2017-11-30

In this work, the performance of five different fiber optic sensors at cryogenic temperatures has been analyzed. A photonic crystal fiber Fabry-Pérot interferometer, two Sagnac interferometers, a commercial fiber Bragg grating (FBG), and a π-phase shifted fiber Bragg grating interrogated in a random distributed feedback fiber laser have been studied. Their sensitivities and resolutions as sensors for cryogenic temperatures have been compared regarding their advantages and disadvantages. Additionally, the results have been compared with the given by a commercial optical backscatter reflectometer that allowed for distributed temperature measurements of a single mode fiber.

Study of Optical Fiber Sensors for Cryogenic Temperature Measurements

Directory of Open Access Journals (Sweden)

Veronica De Miguel-Soto

2017-11-01

Full Text Available In this work, the performance of five different fiber optic sensors at cryogenic temperatures has been analyzed. A photonic crystal fiber Fabry-Pérot interferometer, two Sagnac interferometers, a commercial fiber Bragg grating (FBG, and a π-phase shifted fiber Bragg grating interrogated in a random distributed feedback fiber laser have been studied. Their sensitivities and resolutions as sensors for cryogenic temperatures have been compared regarding their advantages and disadvantages. Additionally, the results have been compared with the given by a commercial optical backscatter reflectometer that allowed for distributed temperature measurements of a single mode fiber.

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

Science.gov (United States)

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

2018-04-08

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.

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

Directory of Open Access Journals (Sweden)

Weifang Zhang

2018-04-01

Full Text Available 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.

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

Science.gov (United States)

Tang, Yongsheng; Ren, Zhongdao

2017-02-20

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.

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

Directory of Open Access Journals (Sweden)

Yongsheng Tang

2017-02-01

Full Text Available 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.

Response of fiber Bragg gratings bonded on a glass/epoxy laminate subjected to static loadings

KAUST Repository

Mulle, Matthieu

2015-04-22

Fiber Bragg gratings (FBG) may be used to monitor strain over the surface of a structure as an alternative technology to conventional strain gauges. However, FBG bonding techniques have still not been established to yield satisfactory surface measurements. Here, two adhesives were investigated, one with low viscosity and the other with high viscosity for bonding FBGs on glass/epoxy sandwich skins. First, instrumented elementary specimens were tested under tension. FBG strain results were analyzed together with digital image correlation (DIC) measurements. The influence of the bonding layer on the measured strain and on the integrity of the sensor was investigated by considering different regions of interest. Next, an instrumented structural sandwich beam was tested under four-point bending. FBG rosettes were compared to conventional strain gauge rosettes. The high viscosity adhesive demonstrated behaviors that affected FBG accuracy. Brittleness of the bonding layer and poor interface adhesion were observed using DIC and X-ray tomography. By contrast, the low viscosity adhesive demonstrated satisfactory results. The FBG strain measurements appeared to be consistent with those of DIC. The accuracy is also adequate as the FBGs and the conventional strain gauges had similar results in three directions, under tension and under compression.

Real-time Cure Monitoring of Composites Using a Guided wave-based System with High Temperature Piezoelectric Transducers, Fiber Bragg Gratings, and Phase-shifted Fiber Bragg Gratings

Science.gov (United States)

Hudson, Tyler Blake

An in-process, in-situ cure monitoring technique utilizing a guided wave-based concept for carbon fiber reinforced polymer (CFRP) composites was investigated. Two automated cure monitoring systems using guided-wave ultrasonics were developed for characterizing the state of the cure. In the first system, surface mounted high-temperature piezoelectric transducer arrays were employed for actuation and sensing. The second system motivated by the success of the first system includes a single piezoelectric disc, bonded onto the surface of the composite for excitation; fiber Bragg gratings (FBGs) and/or phase-shifted fiber Bragg gratings (PSFBGs) were embedded in the composite for distributed cure sensing. Composite material properties (viscosity and degree of cure) evolved during cure of the panels fabricated from HexcelRTM IM7/8552 prepreg correlated well to the amplitude, time of arrival, and group velocity of the guided wave-based measurements during the cure cycle. In addition, key phase transitions (gelation and vitrification) were clearly identified from the experimental data during the same cure cycle. The material properties and phase transitions were validated using cure process modeling software (e.g., RAVENRTM). The high-temperature piezoelectric transducer array system demonstrated the feasibility of a guided wave-based, in-process, cure monitoring and provided the framework for defect detection during cure. Ultimately, this system could provide a traceable data stream for non-compliance investigations during serial production and perform closed-loop process control to maximize composite panel quality and consistency. In addition, this system could be deployed as a "smart" caul/tool plate to existing production lines without changing the design of the aircraft/structure. With the second system, strain in low frequency (quasi-static) and the guided wavebased signals in several hundred kilohertz range were measured almost simultaneously using the same FBG or PS-FBG

A High-Resolution Demodulation Algorithm for FBG-FP Static-Strain Sensors Based on the Hilbert Transform and Cross Third-Order Cumulant

Directory of Open Access Journals (Sweden)

Wenzhu Huang

2015-04-01

Full Text Available Static strain can be detected by measuring a cross-correlation of reflection spectra from two fiber Bragg gratings (FBGs. However, the static-strain measurement resolution is limited by the dominant Gaussian noise source when using this traditional method. This paper presents a novel static-strain demodulation algorithm for FBG-based Fabry-Perot interferometers (FBG-FPs. The Hilbert transform is proposed for changing the Gaussian distribution of the two FBG-FPs’ reflection spectra, and a cross third-order cumulant is used to use the results of the Hilbert transform and get a group of noise-vanished signals which can be used to accurately calculate the wavelength difference of the two FBG-FPs. The benefit by these processes is that Gaussian noise in the spectra can be suppressed completely in theory and a higher resolution can be reached. In order to verify the precision and flexibility of this algorithm, a detailed theory model and a simulation analysis are given, and an experiment is implemented. As a result, a static-strain resolution of 0.9 nε under laboratory environment condition is achieved, showing a higher resolution than the traditional cross-correlation method.

A modified phase diversity wavefront sensor with a diffraction grating

International Nuclear Information System (INIS)

Luo Qun; Huang Lin-Hai; Gu Nai-Ting; Rao Chang-Hui

2012-01-01

The phase diversity wavefront sensor is one of the tools used to estimate wavefront aberration, and it is often used as a wavefront sensor in adaptive optics systems. However, the performance of the traditional phase diversity wavefront sensor is limited by the accuracy and dynamic ranges of the intensity distribution at the focus and defocus positions of the CCD camera. In this paper, a modified phase diversity wavefront sensor based on a diffraction grating is proposed to improve the ability to measure the wavefront aberration with larger amplitude and higher spatial frequency. The basic principle and the optics construction of the proposed method are also described in detail. The noise propagation property of the proposed method is also analysed by using the numerical simulation method, and comparison between the diffraction grating phase diversity wavefront sensor and the traditional phase diversity wavefront sensor is also made. The simulation results show that the diffraction grating phase diversity wavefront sensor can obviously improve the ability to measure the wavefront aberration, especially the wavefront aberration with larger amplitude and higher spatial frequency

Enhancing thermal reliability of fiber-optic sensors for bio-inspired applications at ultra-high temperatures

International Nuclear Information System (INIS)

Kang, Donghoon; Kim, Heon-Young; Kim, Dae-Hyun

2014-01-01

The rapid growth of bio-(inspired) sensors has led to an improvement in modern healthcare and human–robot systems in recent years. Higher levels of reliability and better flexibility, essential features of these sensors, are very much required in many application fields (e.g. applications at ultra-high temperatures). Fiber-optic sensors, and fiber Bragg grating (FBG) sensors in particular, are being widely studied as suitable sensors for improved structural health monitoring (SHM) due to their many merits. To enhance the thermal reliability of FBG sensors, thermal sensitivity, generally expressed as α f + ξ f and considered a constant, should be investigated more precisely. For this purpose, the governing equation of FBG sensors is modified using differential derivatives between the wavelength shift and the temperature change in this study. Through a thermal test ranging from RT to 900 °C, the thermal sensitivity of FBG sensors is successfully examined and this guarantees thermal reliability of FBG sensors at ultra-high temperatures. In detail, α f + ξ f has a non-linear dependence on temperature and varies from 6.0 × 10 −6  °C −1 (20 °C) to 10.6 × 10 −6  °C −1 (650 °C). Also, FBGs should be carefully used for applications at ultra-high temperatures due to signal disappearance near 900 °C. (paper)

A Long-Period Grating Sensor for Wind Turbine Blades

DEFF Research Database (Denmark)

Glavind, Lars

This PhD project concerns the applied research for providing a novel sensor for measurements on wind turbine blades, based on Long-Period Gratings. The idea is based on the utilization of a special asymmetrical optical fibre with Long-Period Gratings for directional sensitive bend sensing...... blade material, where a suitable process and recoating material were investigated. The sensor was implemented and tested on a full scale wind turbine blade placed on a test rig. This first prototype has demonstrated the capability of the sensor for wind turbine blade monitoring, particular...... the possibility to distinguish between the flap- and edge-wise bend directions on the wind turbine blade, providing a selective sensor. The sensor has proven to be very robust and suitable for this application....

Elastomeric polymer resonant waveguide grating based pressure sensor

International Nuclear Information System (INIS)

Song, Fuchuan; Xie, Antonio Jou; Seo, Sang-Woo

2014-01-01

In this paper, we demonstrate an elastomeric polymer resonant waveguide grating structure to be used as a pressure sensor. The applied pressure is measured by optical resonance spectrum peak shift. The sensitivity—as high as 86.74 pm psi −1 or 12.58 pm kPa −1 —has been experimentally obtained from a fabricated sensor. Potentially, the sensitivity of the demonstrated sensor can be tuned to different pressure ranges by the choices of elastic properties and layer thicknesses of the waveguide and cladding layers. The simulation results agree well with experimental results and indicate that the dominant effect on the sensor is the change of grating period when external pressure is applied. Based on the two-dimensional planar structure, the demonstrated sensor can be used to measure applied surface pressure optically, which has potential applications for optical ultrasound imaging and pressure wave detection/mapping

Monitoring pressure profiles across an airfoil with a fiber Bragg grating sensor array

Science.gov (United States)

Papageorgiou, Anthony W.; Parkinson, Luke A.; Karas, Andrew R.; Hansen, Kristy L.; Arkwright, John W.

2018-02-01

Fluid flow over an airfoil section creates a pressure difference across the upper and lower surfaces, thus generating lift. Successful wing design is a combination of engineering design and experience in the field, with subtleties in design and manufacture having significant impact on the amount of lift produced. Current methods of airfoil optimization and validation typically involve computational fluid dynamics (CFD) and extensive wind tunnel testing with pressure sensors embedded into the airfoil to measure the pressure over the wing. Monitoring pressure along an airfoil in a wind tunnel is typically achieved using surface pressure taps that consist of hollow tubes running from the surface of the airfoil to individual pressure sensors external to the tunnel. These pressure taps are complex to configure and not ideal for in-flight testing. Fiber Bragg grating (FBG) pressure sensing arrays provide a highly viable option for both wind tunnel and inflight pressure measurement. We present a fiber optic sensor array that can detect positive and negative pressure suitable for validating CFD models of airfoil profile sections. The sensing array presented here consists of 6 independent sensing elements, each capable of a pressure resolution of less than 10 Pa over the range of 70 kPa to 120 kPa. The device has been tested with the sensor array attached to a 90mm chord length airfoil section subjected to low velocity flow. Results show that the arrays are capable of accurately detecting variations of the pressure profile along the airfoil as the angle of attack is varied from zero to the point at which stall occurs.

Health monitoring of unmanned aerial vehicle based on optical fiber sensor array

Science.gov (United States)

Luo, Yuxiang; Shen, Jingshi; Shao, Fei; Guo, Chunhui; Yang, Ning; Zhang, Jiande

2017-10-01

The unmanned aerial vehicle (UAV) in flight needs to face the complicated environment, especially to withstand harsh weather conditions, such as the temperature and pressure. Compared with conventional sensors, fiber Bragg grating (FBG) sensor has the advantages of small size, light weight, high reliability, high precision, anti-electromagnetic interference, long lift-span, moistureproof and good resistance to causticity. It's easy to be embedded in composite structural components of UAVs. In the paper, over 1000 FBG sensors distribute regularly on a wide range of UAVs body, combining wavelength division multiplexing (WDM), time division multiplexing (TDM) and multichannel parallel architecture. WDM has the advantage of high spatial resolution. TDM has the advantage of large capacity and wide range. It is worthful to constitute a sensor network by different technologies. For the signal demodulation of FBG sensor array, WDM works by means of wavelength scanning light sources and F-P etalon. TDM adopts the technology of optical time-domain reflectometry. In order to demodulate efficiently, the most proper sensor multiplex number with some reflectivity is given by the curves fitting. Due to the regular array arrangement of FBG sensors on the UAVs, we can acquire the health state of UAVs in the form of 3D visualization. It is helpful to master the information of health status rapidly and give a real-time health evaluation.

Characterization of FBG sensor interrogation based on a FDML wavelength swept laser

Science.gov (United States)

Jung, Eun Joo; Kim, Chang-Seok; Jeong, Myung Yung; Kim, Moon Ki; Jeon, Min Yong; Jung, Woonggyu; Chen, Zhongping

2012-01-01

In this study, we develop an ultra-fast fiber Bragg grating sensor system that is based on the Fourier domain mode-locked (FDML) swept laser. A FDML wavelength swept laser has many advantages compared to the conventional wavelength swept laser source, such as high-speed interrogation, narrow spectral sensitivity, and high phase stability. The newly developed FDML wavelength swept laser shows a superior performance of a high scan rate of 31.3 kHz and a broad scan range of over 70 nm simultaneously. The performance of the grating sensor interrogating system using a FDML wavelength swept laser is characterized in both static and dynamic strain responses. PMID:18852764

Multi-resonance peaks fiber Bragg gratings based on largely-chirped structure

Science.gov (United States)

Chen, Chao; Zhang, Xuan-Yu; Wei, Wei-Hua; Chen, Yong-Yi; Qin, Li; Ning, Yong-Qiang; Yu, Yong-Sen

2018-04-01

A composite fiber Bragg grating (FBG) with multi-resonance peaks (MRPs) has been realized by using femtosecond (fs) laser point-by-point inscription in single-mode fiber. This device contains a segment of largely-chirped gratings with the ultrahigh chirp coefficients and a segment of uniform high-order gratings. The observed MRPs are distributed in an ultra-broadband wavelength range from 1200 nm to 1700 nm in the form of quasi-period or multi-peak-group. For the 8th-order MRPs-FBG, we studied the axial strain and high-temperature sensing characteristics of different resonance peaks experimentally. Moreover, we have demonstrated a multi-wavelength fiber lasers with three-wavelength stable output by using a 9th-order MRPs-FBG as the wavelength selector. This work is significant for the fabrication and functionalization of FBGs with complicated spectra characteristics.

Interrogation of fibre Bragg gratings through a fibre optic rotary joint on a geotechnical centrifuge

Science.gov (United States)

Correia, Ricardo; James, Stephen W.; Marshall, Alec; Heron, Charles; Korposh, Sergiy

2016-05-01

The monitoring of an array of fibre Bragg gratings (FBGs) strain sensors was performed through a single channel, single mode fibre optic rotary joint (FORJ) mounted on a geotechnical centrifuge. The array of three FBGs was attached to an aluminum plate that was anchored at the ends and placed on the model platform of the centrifuge. Acceleration forces of up to 50g were applied and the reflection signal of the monitored FBGs recorded dynamically using a 2.5kHz FBG interrogator placed outside the centrifuge. The use of a FORJ allowed the monitoring of the FBGs without submitting the FBG interrogator to the high g-forces experienced in the centrifuge.

Micro-structured optical fiber sensor for simultaneous measurement of temperature and refractive index

Science.gov (United States)

Liu, Ying-gang; Liu, Xin; Ma, Cheng-ju; Zhou, Yu-min

2018-03-01

Through using micro-machining method for optical fiber sensor, a kind of miniature, compact and composite structural all-fiber sensor is presented. Based on manufacturing two micro-holes with certain distance in ordinary single-mode fiber Bragg grating (FBG) by excimer laser processing technique, we fabricate a dual Fabry-Perot-FBG (FP-FBG) composite fiber interferometric sensor, which can be used in simultaneous measurement for liquid's refractive index (RI) and temperature change. Due to every micro-hole and the dual micro-holes in fiber acting as different Fabry-Perot (FP) cavities, this kind of sensor has not only different RI sensitivities but also different temperature sensitivities, which are corresponding to the wavelength shifts of the fine interference fringes and spectral envelope, respectively. The experimental results show that the spectral wavelength shift keep better linear response for temperature and RI change, so that we can select the higher temperature and RI sensitivities as well as the analyzed sensitivities of FBG to utilize them for constituting a sensitivity coefficients matrix. Finally, the variations of liquid's temperature and RI are detected effectively, and the resolutions can reach to 0.1 °C and 1.0 ×10-5 RIU. These characteristics are what other single-type sensors don't have, so that this kind of all-fiber dual FP-FBG composite fiber interferometric sensor can be used in extremely tiny liquid environment for measuring different physical quantities simultaneously.

A point-wise fiber Bragg grating displacement sensing system and its application for active vibration suppression of a smart cantilever beam subjected to multiple impact loadings

International Nuclear Information System (INIS)

Chuang, Kuo-Chih; Ma, Chien-Ching; Liao, Heng-Tseng

2012-01-01

In this work, active vibration suppression of a smart cantilever beam subjected to disturbances from multiple impact loadings is investigated with a point-wise fiber Bragg grating (FBG) displacement sensing system. An FBG demodulator is employed in the proposed fiber sensing system to dynamically demodulate the responses obtained by the FBG displacement sensor with high sensitivity. To investigate the ability of the proposed FBG displacement sensor as a feedback sensor, velocity feedback control and delay control are employed to suppress the vibrations of the first three bending modes of the smart cantilever beam. To improve the control performance for the first bending mode when the cantilever beam is subjected to an impact loading, we improve the conventional velocity feedback controller by tuning the control gain online with the aid of information from a higher vibration mode. Finally, active control of vibrations induced by multiple impact loadings due to a plastic ball is performed with the improved velocity feedback control. The experimental results show that active vibration control of smart structures subjected to disturbances such as impact loadings can be achieved by employing the proposed FBG sensing system to feed back out-of-plane point-wise displacement responses with high sensitivity. (paper)

A Low Frequency FBG Accelerometer with Symmetrical Bended Spring Plates

Directory of Open Access Journals (Sweden)

Fufei Liu

2017-01-01

Full Text Available To meet the requirements for low-frequency vibration monitoring, a new type of FBG (fiber Bragg grating accelerometer with a bended spring plate is proposed. Two symmetrical bended spring plates are used as elastic elements, which drive the FBG to produce axial strains equal in magnitude but opposite in direction when exciting vibrations exist, leading to doubling the wavelength shift of the FBG. The mechanics model and a numerical method are presented in this paper, with which the influence of the structural parameters on the sensitivity and the eigenfrequency are discussed. The test results show that the sensitivity of the accelerometer is more than 1000 pm/g when the frequency is within the 0.7–20 Hz range.

Polymer Optical Fibre Bragg Grating Humidity Sensor at 100ºC

DEFF Research Database (Denmark)

Woyessa, Getinet; Fasano, Andrea; Markos, Christos

2016-01-01

We have demonstrated a polymer optical fibre Bragg grating humidity sensor that can be operated up to 100ºC. The sensor has been fabricated from a polycarbonate (PC) microstructured polymer optical fibre Bragg grating (mPOFBG). PC mPOFBG gave a relative humidity (RH) sensitivity of 6.95±0.83 pm...

An FBG acoustic emission source locating system based on PHAT and GA

Science.gov (United States)

Shen, Jing-shi; Zeng, Xiao-dong; Li, Wei; Jiang, Ming-shun

2017-09-01

Using the acoustic emission locating technology to monitor the health of the structure is important for ensuring the continuous and healthy operation of the complex engineering structures and large mechanical equipment. In this paper, four fiber Bragg grating (FBG) sensors are used to establish the sensor array to locate the acoustic emission source. Firstly, the nonlinear locating equations are established based on the principle of acoustic emission, and the solution of these equations is transformed into an optimization problem. Secondly, time difference extraction algorithm based on the phase transform (PHAT) weighted generalized cross correlation provides the necessary conditions for the accurate localization. Finally, the genetic algorithm (GA) is used to solve the optimization model. In this paper, twenty points are tested in the marble plate surface, and the results show that the absolute locating error is within the range of 10 mm, which proves the accuracy of this locating method.

Laser sensor with Bragg gratings of fiber optics to physics parameter measuring

International Nuclear Information System (INIS)

Vazquez, R.; Garcia, C.; May, M.; Camas, J.

2009-01-01

We present the operation of a fiber laser sensor made by an Erbium Doped Fiber pumped at 980nm, an 4.23 km passive fiber and two fiber Bragg gratings placed at the ends of the laser cavity. Under normal conditions, the Bragg gratings have different reflection wavelengths and laser emission is not generated. The two Bragg gratings can be placed at the same reflection wavelength when the Bragg grating with the lowest reflective wavelength increases their temperature which can be used as a sensor element. The laser generation thus shows that the Bragg grating is increasing their temperature. We used a Peltier cell for to change gradually the temperature. (Author)

Ultra-short FBG based distributed sensing using shifted optical Gaussian filters and microwave-network analysis.

Science.gov (United States)

Cheng, Rui; Xia, Li; Sima, Chaotan; Ran, Yanli; Rohollahnejad, Jalal; Zhou, Jiaao; Wen, Yongqiang; Yu, Can

2016-02-08

Ultrashort fiber Bragg gratings (US-FBGs) have significant potential as weak grating sensors for distributed sensing, but the exploitation have been limited by their inherent broad spectra that are undesirable for most traditional wavelength measurements. To address this, we have recently introduced a new interrogation concept using shifted optical Gaussian filters (SOGF) which is well suitable for US-FBG measurements. Here, we apply it to demonstrate, for the first time, an US-FBG-based self-referencing distributed optical sensing technique, with the advantages of adjustable sensitivity and range, high-speed and wide-range (potentially >14000 με) intensity-based detection, and resistance to disturbance by nonuniform parameter distribution. The entire system is essentially based on a microwave network, which incorporates the SOGF with a fiber delay-line between the two arms. Differential detections of the cascaded US-FBGs are performed individually in the network time-domain response which can be obtained by analyzing its complex frequency response. Experimental results are presented and discussed using eight cascaded US-FBGs. A comprehensive numerical analysis is also conducted to assess the system performance, which shows that the use of US-FBGs instead of conventional weak FBGs could significantly improve the power budget and capacity of the distributed sensing system while maintaining the crosstalk level and intensity decay rate, providing a promising route for future sensing applications.

POF based glucose sensor incorporating grating wavelength filters

DEFF Research Database (Denmark)

Hassan, Hafeez Ul; Aasmul, Søren; Bang, Ole

2014-01-01

AND RESEARCH IN POLYMER OPTICAL DEVICES; TRIPOD. Within the domain of TRIPOD, research is conducted on "Plastic Optical Fiber based Glucose Sensors Incorporating Grating Wavelength Filters". Research will be focused to optimized fiber tips for better coupling efficiency, reducing the response time of sensor...

Nano-imprint gold grating as refractive index sensor

International Nuclear Information System (INIS)

Kumari, Sudha; Mohapatra, Saswat; Moirangthem, Rakesh S.

2016-01-01

Large scale of fabrication of plasmonic nanostructures has been a challenging task due to time consuming process and requirement of expensive nanofabrication tools such as electron beam lithography system, focused ion beam system, and extreme UV photolithography system. Here, we present a cost-effective fabrication technique so called soft nanoimprinting to fabricate nanostructures on the larger sample area. In our fabrication process, a commercially available optical DVD disc was used as a template which was imprinted on a polymer glass substrate to prepare 1D polymer nano-grating. A homemade nanoimprinting setup was used in this fabrication process. Further, a label-free refractive index sensor was developed by utilizing the properties of surface plasmon resonance (SPR) of a gold coated 1D polymer nano-grating. Refractive index sensing was tested by exposing different solutions of glycerol-water mixture on the surface of gold nano-grating. The calculated bulk refractive index sensitivity was found to be 751nm/RIU. We believed that our proposed SPR sensor could be a promising candidate for developing low-cost refractive index sensor with high sensitivity on a large scale.

Fibre Bragg Grating and Long Period Grating Sensors in Polymer Optical Fibres

DEFF Research Database (Denmark)

Bundalo, Ivan-Lazar

mechanisms in polymer fibres using a CO2 laser. One is etching and the other one is perturbation of the microstructured region. After inscription of LPGs, the concept of a biocompatible distributed medical endoscope is presented, where an all-plastic LPG based device is produced. A transducer pod is made...... of applications and pushing the limits. The first part of the work focuses on the fabrication of FBGs in polymer optical fibres. FBGs are a periodic perturbation of the refractive index of the optical fibre core which act as a wavelength specific reflector. The fibres used are made of Polymethyl methacrylate....... In this system a high power CO2 laser is used for the inscription. An LPG is also a periodic perturbation of the guided core mode in fibre, but unlike FBG which reflects the core mode, the LPG couples the core mode to a cladding mode outside the core. We have shown that the LPG grating can be formed through two...

Characterizing Fiber Bragg Grating Index Profiles to Improve the Writing Process

DEFF Research Database (Denmark)

Espejo, M.J.; Svalgaard, Mikael; Dyer, S.D.

2006-01-01

We demonstrate an accurate method for identifying both systematic and random errors in a fiber Bragg grating (FBG) writing system and show its application to calibration of the writing process. We first measure the FBG impulse response using low-coherence interferometry, and then we calculate......-beam dithered phase mask FBG writing system. We demonstrate the ability to identify errors in the writing process that would not likely be found from a measurement of the FBG reflection spectrum alone....

FBG Interrogation Method with High Resolution and Response Speed Based on a Reflective-Matched FBG Scheme

Science.gov (United States)

Cui, Jiwen; Hu, Yang; Feng, Kunpeng; Li, Junying; Tan, Jiubin

2015-01-01

In this paper, a high resolution and response speed interrogation method based on a reflective-matched Fiber Bragg Grating (FBG) scheme is investigated in detail. The nonlinear problem of the reflective-matched FBG sensing interrogation scheme is solved by establishing and optimizing the mathematical model. A mechanical adjustment to optimize the interrogation method by tuning the central wavelength of the reference FBG to improve the stability and anti-temperature perturbation performance is investigated. To satisfy the measurement requirements of optical and electric signal processing, a well- designed acquisition circuit board is prepared, and experiments on the performance of the interrogation method are carried out. The experimental results indicate that the optical power resolution of the acquisition circuit border is better than 8 pW, and the stability of the interrogation method with the mechanical adjustment can reach 0.06%. Moreover, the nonlinearity of the interrogation method is 3.3% in the measurable range of 60 pm; the influence of temperature is significantly reduced to 9.5%; the wavelength resolution and response speed can achieve values of 0.3 pm and 500 kHz, respectively. PMID:26184195

Fiber Bragg Grating Sensors for Harsh Environments

Directory of Open Access Journals (Sweden)

Stephen J. Mihailov

2012-02-01

Full Text Available Because of their small size, passive nature, immunity to electromagnetic interference, and capability to directly measure physical parameters such as temperature and strain, fiber Bragg grating sensors have developed beyond a laboratory curiosity and are becoming a mainstream sensing technology. Recently, high temperature stable gratings based on regeneration techniques and femtosecond infrared laser processing have shown promise for use in extreme environments such as high temperature, pressure or ionizing radiation. Such gratings are ideally suited for energy production applications where there is a requirement for advanced energy system instrumentation and controls that are operable in harsh environments. This paper will present a review of some of the more recent developments.

Development of Metal Oxide Nanostructure-based Optical Sensors for Fossil Fuel Derived Gases Measurement at High Temperature

Energy Technology Data Exchange (ETDEWEB)

Chen, Kevin P. [Univ. of Pittsburgh, PA (United States)

2015-02-13

This final technical report details research works performed supported by a Department of Energy grant (DE-FE0003859), which was awarded under the University Coal Research Program administrated by National Energy Technology Laboratory. This research program studied high temperature fiber sensor for harsh environment applications. It developed two fiber optical sensor platform technology including regenerative fiber Bragg grating sensors and distributed fiber optical sensing based on Rayleigh backscattering optical frequency domain reflectometry. Through the studies of chemical and thermal regenerative techniques for fiber Bragg grating (FBG) fabrication, high-temperature stable FBG sensors were successfully developed and fabricated in air-hole microstructured fibers, high-attenuation fibers, rare-earth doped fibers, and standard telecommunication fibers. By optimizing the laser processing and thermal annealing procedures, fiber grating sensors with stable performance up to 1100°C have been developed. Using these temperature-stable FBG gratings as sensor platform, fiber optical flow, temperature, pressure, and chemical sensors have been developed to operate at high temperatures up to 800°C. Through the integration of on-fiber functional coating, the use of application-specific air-hole microstructural fiber, and application of active fiber sensing scheme, distributed fiber sensor for temperature, pressure, flow, liquid level, and chemical sensing have been demonstrated with high spatial resolution (1-cm or better) with wide temperature ranges. These include the demonstration of 1) liquid level sensing from 77K to the room temperature, pressure/temperature sensing from the room temperature to 800C and from the 15psi to 2000 psi, and hydrogen concentration measurement from 0.2% to 10% with temperature ranges from the room temperature to 700°C. Optical sensors developed by this program has broken several technical records including flow sensors with the highest

[INVITED] Tilted fiber grating mechanical and biochemical sensors

Science.gov (United States)

Guo, Tuan; Liu, Fu; Guan, Bai-Ou; Albert, Jacques

2016-04-01

The tilted fiber Bragg grating (TFBG) is a new kind of fiber-optic sensor that possesses all the advantages of well-established Bragg grating technology in addition to being able to excite cladding modes resonantly. This device opens up a multitude of opportunities for single-point sensing in hard-to-reach spaces with very controllable cross-sensitivities, absolute and relative measurements of various parameters, and an extreme sensitivity to materials external to the fiber without requiring the fiber to be etched or tapered. Over the past five years, our research group has been developing multimodal fiber-optic sensors based on TFBG in various shapes and forms, always keeping the device itself simple to fabricate and compatible with low-cost manufacturing. This paper presents a brief review of the principle, fabrication, characterization, and implementation of TFBGs, followed by our progress in TFBG sensors for mechanical and biochemical applications, including one-dimensional TFBG vibroscopes, accelerometers and micro-displacement sensors; two-dimensional TFBG vector vibroscopes and vector rotation sensors; reflective TFBG refractometers with in-fiber and fiber-to-fiber configurations; polarimetric and plasmonic TFBG biochemical sensors for in-situ detection of cell, protein and glucose.

Acoustic emission detection with fiber optical sensors for dry cask storage health monitoring

Science.gov (United States)

Lin, Bin; Bao, Jingjing; Yu, Lingyu; Giurgiutiu, Victor

2016-04-01

The increasing number, size, and complexity of nuclear facilities deployed worldwide are increasing the need to maintain readiness and develop innovative sensing materials to monitor important to safety structures (ITS). In the past two decades, an extensive sensor technology development has been used for structural health monitoring (SHM). Technologies for the diagnosis and prognosis of a nuclear system, such as dry cask storage system (DCSS), can improve verification of the health of the structure that can eventually reduce the likelihood of inadvertently failure of a component. Fiber optical sensors have emerged as one of the major SHM technologies developed particularly for temperature and strain measurements. This paper presents the development of optical equipment that is suitable for ultrasonic guided wave detection for active SHM in the MHz range. An experimental study of using fiber Bragg grating (FBG) as acoustic emission (AE) sensors was performed on steel blocks. FBG have the advantage of being durable, lightweight, and easily embeddable into composite structures as well as being immune to electromagnetic interference and optically multiplexed. The temperature effect on the FBG sensors was also studied. A multi-channel FBG system was developed and compared with piezoelectric based AE system. The paper ends with conclusions and suggestions for further work.

Design of FBG En/decoders in Coherent 2-D Time-polarization OCDMA Systems

Science.gov (United States)

Hou, Fen-fei; Yang, Ming

2012-12-01

A novel fiber Bragg grating (FBG)-based en/decoder for the two-dimensional (2-D) time-spreading and polarization multiplexer optical coding is proposed. Compared with other 2-D en/decoders, the proposed en/decoding for an optical code-division multiple-access (OCDMA) system uses a single phase-encoded FBG and coherent en/decoding. Furthermore, combined with reconstruction-equivalent-chirp technology, such en/decoders can be realized with a conventional simple fabrication setup. Experimental results of such en/decoders and the corresponding system test at a data rate of 5 Gbit/s demonstrate that this kind of 2-D FBG-based en/decoders could improve the performances of OCDMA systems.

Polymer coated fiber Bragg grating thermometry for microwave hyperthermia.

Science.gov (United States)

Saxena, Indu Fiesler; Hui, Kaleo; Astrahan, Melvin

2010-09-01

Measuring tissue temperature distribution during electromagnetically induced hyperthermia (HT) is challenging. High resistance thermistors with nonmetallic leads have been used successfully in commercial HT systems for about three decades. The single 1 mm thick temperature sensing element is mechanically moved to measure tissue temperature distributions. By employing a single thermometry probe containing a fixed linear sensor array temperature, distributions during therapy can be measured with greater ease. While the first attempts to use fiber Bragg grating (FBG) technology to obtain multiple temperature points along a single fiber have been reported, improvement in the detection system's stability were needed for clinical applications. The FBG temperature sensing system described here has a very high temporal stability detection system and an order of magnitude faster readout than commercial systems. It is shown to be suitable for multiple point fiber thermometry during microwave hyperthermia when compared to conventional mechanically scanning probe HT thermometry. A polymer coated fiber Bragg grating (PFBG) technology is described that provides a number of FBG thermometry locations along the length of a single optical fiber. The PFBG probe developed is tested under simulated microwave hyperthermia treatment to a tissue equivalent phantom. Two temperature probes, the multiple PFBG sensor and the Bowman probe, placed symmetrically with respect to a microwave antenna in a tissue phantom are subjected to microwave hyperthermia. Measurements are made at start of HT and 85 min later, when a 6 degrees C increase in temperature is registered by both probes, as is typical in clinical HT therapy. The optical fiber multipoint thermometry probe performs highly stable, real-time thermometry updating each multipoint thermometry scan over a 5 cm length every 2 s. Bowman probe measurements are acquired simultaneously for comparison. In addition, the PFBG sensor's detection

Omnidirectional piezo-optical ring sensor for enhanced guided wave structural health monitoring

International Nuclear Information System (INIS)

Giurgiutiu, Victor; Roman, Catalin; Lin, Bin; Frankforter, Erik

2015-01-01

This paper presents a novel method for the detection of ultrasonic waves from acoustic emission events using piezoelectric wafer ac3tive sensors (PWAS) and optical fiber Bragg grating (FBG) sensing combined with mechanical resonance amplification principles. The method is best suited for detecting the out-of-plane motion of the AE wave with preference for a certain frequency that can be adjusted by design. Several issues are discussed: (a) study the mode shapes of the sensors under different resonance frequencies in order to understand the behavior of the ring in a frequency band of interest; (b) comparison of analytical results and mode shapes with FEM predictions; (c) choice of the final piezo-optical ring sensor shape; (d) testing of the piezo-optical ring sensor prototype; (e) discussion of the ring-sensor test results in comparison with conventional results from PWAS and FBG sensors mounted directly on the test structure. The paper ends with summary, conclusions, and suggestions for further work. (paper)

A MEMS torsion magnetic sensor with reflective blazed grating integration

International Nuclear Information System (INIS)

Long, Liang; Zhong, Shaolong

2016-01-01

A novel magnetic sensor based on a permanent magnet and blazed grating is presented in this paper. The magnetic field is detected by measuring the diffracted wavelength of the blazed grating which is changed by the torsion motion of a torsion sensitive micro-electromechanical system (MEMS) structure with a permanent magnet attached. A V-shape grating structure is obtained by wet etching on a (1 0 0) SOI substrate. When the magnet is magnetized in different directions, the in-plane or out-of-plane magnetic field is detected by a sensor. The MEMS magnetic sensor with a permanent magnet is fabricated after analytical design and bulk micromachining processes. The magnetic-sensing capability of the sensor is tested by fiber-optic detection system. The result shows the sensitivities of the in-plane and out-of-plane magnetic fields are 3.6 pm μ T −1 and 5.7 pm μ T −1 , respectively. Due to utilization of the permanent magnet and fiber-optic detection, the sensor shows excellent capability of covering the high-resolution detection of low-frequency signals. In addition, the sensitive direction of the magnetic sensor can be easily switched by varying the magnetized direction of the permanent magnet, which offers a simple way to achieve tri-axis magnetic sensor application. (paper)

Simultaneous measurement of temperature and pressure by a single fiber Bragg grating with a broadened reflection spectrum.

Science.gov (United States)

Guo, Tuan; Qiao, Xueguang; Jia, Zhenan; Zhao, Qida; Dong, Xiaoyi

2006-05-01

Simultaneous measurement of temperature and pressure with a single fiber Bragg grating (FBG) based on a broadened reflection spectrum is proposed and experimentally demonstrated. A novel double-hole structure of a cantilever beam is designed, and a FBG is affixed on the nonuniform strain area of the cantilever beam. The Bragg reflection bandwidth is sensitive to the spatially gradient strain but is free from the spatially uniform temperature. The wavelength peak shift and the bandwidth broadening of the FBG with a change of temperature and pressure allow for simultaneous discrimination between the temperature and the pressure effects. Standard deviation errors of 1.4 degrees C and 1.8 kPa were obtained with temperature and pressure ranges of 20 degrees C-100 degrees C and 0-80 kPa, respectively. This novel and low-cost sensor approach has considerable potential applications for temperature-insensitive strain measurement.

Field monitoring of static, dynamic, and statnamic pile loading tests using fibre Bragg grating strain sensors

Science.gov (United States)

Li, Jin; Correia, Ricardo P.; Chehura, Edmon; Staines, Stephen; James, Stephen W.; Tatam, Ralph; Butcher, Antony P.; Fuentes, Raul

2009-10-01

Pile loading test plays an important role in the field of piling engineering. In order to gain further insight into the load transfer mechanism, strain gauges are often used to measure local strains along the piles. This paper reports a case whereby FBG strain sensors was employed in a field trial conducted on three different types of pile loading tests in a glacial till. The instrumentation systems were configured to suit the specific characteristic of each type of test. Typical test results are presented. The great potential of using FBG sensors for pile testing is shown.

Fabrication and characterization of polycarbonate microstructured polymer optical fibers for high-temperature-resistant fiber Bragg grating strain sensors

DEFF Research Database (Denmark)

Fasano, Andrea; Woyessa, Getinet; Stajanca, Pavol

2016-01-01

Here we present the fabrication of a solid-core microstructured polymer optical fiber (mPOF) made of polycarbonate (PC), and report the first experimental demonstration of a fiber Bragg grating (FBG) written in a PC optical fiber. The PC used in this work has a glass transition temperature of 145°C...

Radio-frequency unbalanced M-Z interferometer for wavelength interrogation of fiber Bragg grating sensors.

Science.gov (United States)

Zhou, Jiaao; Xia, Li; Cheng, Rui; Wen, Yongqiang; Rohollahnejad, Jalal

2016-01-15

The optical unbalanced Mach-Zehnder interferometer (UMZI) has attracted significant interests for interrogation of FBG sensors owing to its excellent advantages in sensitivity, resolution, and demodulation speed. But this method is still limited to dynamic measurements due to its poor stability and reliability when used for quasi-static detections. Here, we propose for the first time, to the best of our knowledge, a radio-frequency unbalanced M-Z interferometer (RF-UMZI) for interrogation of FBG sensors, which, owing to its operation in an incoherent rather than a coherent regime, provides an ideal solution for the existing stability problem of the conventional UMZI, with remarkable features of adjustable resolution and potentially extremely high sensitivity. A dispersion compensation fiber (DCF) and single-mode fiber (SMF) with a small length difference are served as the two unbalanced arms of the RF interferometer. The induced differential chromatic dispersion transfers the wavelength shift of the FBG to the change of the RF phase difference between the two interferometric carriers, which ultimately leads to the variation of the RF signal intensity. An interrogation of a strain-turned FBG was accomplished and a maximum sensitivity of 0.00835  a.u./με was obtained, which can easily be further improved by more than two orders of magnitude through various fiber dispersion components. Finally, the stability of the interrogation was tested.

FBG Interrogation Method with High Resolution and Response Speed Based on a Reflective-Matched FBG Scheme.

Science.gov (United States)

Cui, Jiwen; Hu, Yang; Feng, Kunpeng; Li, Junying; Tan, Jiubin

2015-07-08

In this paper, a high resolution and response speed interrogation method based on a reflective-matched Fiber Bragg Grating (FBG) scheme is investigated in detail. The nonlinear problem of the reflective-matched FBG sensing interrogation scheme is solved by establishing and optimizing the mathematical model. A mechanical adjustment to optimize the interrogation method by tuning the central wavelength of the reference FBG to improve the stability and anti-temperature perturbation performance is investigated. To satisfy the measurement requirements of optical and electric signal processing, a well- designed acquisition circuit board is prepared, and experiments on the performance of the interrogation method are carried out. The experimental results indicate that the optical power resolution of the acquisition circuit border is better than 8 pW, and the stability of the interrogation method with the mechanical adjustment can reach 0.06%. Moreover, the nonlinearity of the interrogation method is 3.3% in the measurable range of 60 pm; the influence of temperature is significantly reduced to 9.5%; the wavelength resolution and response speed can achieve values of 0.3 pm and 500 kHz, respectively.

Fiber Bragg Gratings, IT Techniques and Strain Gauge Validation for Strain Calculation on Aged Metal Specimens

Directory of Open Access Journals (Sweden)

Ander Montero

2011-01-01

Full Text Available This paper studies the feasibility of calculating strains in aged F114 steel specimens with Fiber Bragg Grating (FBG sensors and infrared thermography (IT techniques. Two specimens have been conditioned under extreme temperature and relative humidity conditions making comparative tests of stress before and after aging using different adhesives. Moreover, a comparison has been made with IT techniques and conventional methods for calculating stresses in F114 steel. Implementation of Structural Health Monitoring techniques on real aircraft during their life cycle requires a study of the behaviour of FBG sensors and their wiring under real conditions, before using them for a long time. To simulate aging, specimens were stored in a climate chamber at 70 °C and 90% RH for 60 days. This study is framed within the Structural Health Monitoring (SHM and Non Destructuve Evaluation (NDE research lines, integrated into the avionics area maintained by the Aeronautical Technologies Centre (CTA and the University of the Basque Country (UPV/EHU.

Single- and two-phase flow characterization using optical fiber bragg gratings.

Science.gov (United States)

Baroncini, Virgínia H V; Martelli, Cicero; da Silva, Marco José; Morales, Rigoberto E M

2015-03-17

Single- and two-phase flow characterization using optical fiber Bragg gratings (FBGs) is presented. The sensor unit consists of the optical fiber Bragg grating positioned transversely to the flow and fixed in the pipe walls. The hydrodynamic pressure applied by the liquid or air/liquid flow to the optical fiber induces deformation that can be detected by the FBG. Given that the applied pressure is directly related to the mass flow, it is possible to establish a relationship using the grating resonance wavelength shift to determine the mass flow when the flow velocity is well known. For two phase flows of air and liquid, there is a significant change in the force applied to the fiber that accounts for the very distinct densities of these substances. As a consequence, the optical fiber deformation and the correspondent grating wavelength shift as a function of the flow will be very different for an air bubble or a liquid slug, allowing their detection as they flow through the pipe. A quasi-distributed sensing tool with 18 sensors evenly spread along the pipe is developed and characterized, making possible the characterization of the flow, as well as the tracking of the bubbles over a large section of the test bed. Results show good agreement with standard measurement methods and open up plenty of opportunities to both laboratory measurement tools and field applications.

Dual fiber Bragg gratings configuration-based fiber acoustic sensor for low-frequency signal detection

Science.gov (United States)

Yang, Dong; Wang, Shun; Lu, Ping; Liu, Deming

2014-11-01

We propose and fabricate a new type fiber acoustic sensor based on dual fiber Bragg gratings (FBGs) configuration. The acoustic sensor head is constructed by putting the sensing cells enclosed in an aluminum cylinder space built by two Cband FBGs and a titanium diaphragm of 50 um thickness. One end of each FBG is longitudinally adhered to the diaphragm by UV glue. Both of the two FBGs are employed for reflecting light. The dual FBGs play roles not only as signal transmission system but also as sensing component, and they demodulate each other's optical signal mutually during the measurement. Both of the two FBGs are pre-strained and the output optical power experiences fluctuation in a linear relationship along with a variation of axial strain and surrounding acoustic interference. So a precise approach to measure the frequency and sound pressure of the acoustic disturbance is achieved. Experiments are performed and results show that a relatively flat frequency response in a range from 200 Hz to 1 kHz with the average signal-to-noise ratio (SNR) above 21 dB is obtained. The maximum sound pressure sensitivity of 11.35mV/Pa is achieved with the Rsquared value of 0.99131 when the sound pressure in the range of 87.7-106.6dB. It has potential applications in low frequency signal detection. Owing to its direct self-demodulation method, the sensing system reveals the advantages of easy to demodulate, good temperature stability and measurement reliability. Besides, performance of the proposed sensor could be improved by optimizing the parameters of the sensor, especially the diaphragm.

Highly Sensitive Cadmium Concentration Sensor Using Long Period Grating

Directory of Open Access Journals (Sweden)

A. S. Lalasangi

2011-08-01

Full Text Available In this paper we have proposed a simple and effective Long Period Grating chemical sensor for detecting the traces of Cadmium (Cd++ in drinking water at ppm level. Long Period gratings (LPG were fabricated by point-by-point technique with CO2 laser. We have characterized the LPG concentration sensor sensitivity for different solutions of Cd concentrations varying from 0.01 ppm to 0.04 ppm by injecting white Light source and observed transmitted spectra using Optical Spectrum Analyzer (OSA. Proper reagents have been used in the solutions for detection of the Cd species. The overall shift in wavelength is 10 nm when surrounding medium gradually changed from water to 0.04 ppm of cadmium concentrations. A comparative study has been done using sophisticated spectroscopic atomic absorption spectrometer (AAS and Inductively Coupled Plasma (ICP instruments. The spectral sensitivity enhancement was done by modifying grating surface with gold nanoparticles.

Fiber Bragg grating-based performance monitoring of a slope model subjected to seepage

Science.gov (United States)

Zhu, Hong-Hu; Shi, Bin; Yan, Jun-Fan; Zhang, Jie; Zhang, Cheng-Cheng; Wang, Bao-Jun

2014-09-01

In the past few years, fiber optic sensing technologies have played an increasingly important role in the health monitoring of civil infrastructures. These innovative sensing technologies have recently been successfully applied to the performance monitoring of a series of geotechnical structures. Fiber optic sensors have shown many unique advantages in comparison with conventional sensors, including immunity to electrical noise, higher precision and improved durability and embedding capabilities; fiber optic sensors are also smaller in size and lighter in weight. In order to explore the mechanism of seepage-induced slope instability, a small-scale 1 g model test of the soil slope has been performed in the laboratory. During the model’s construction, specially fabricated sensing fibers containing nine fiber Bragg grating (FBG) strain sensors connected in a series were horizontally and vertically embedded into the soil mass. The surcharge load was applied on the slope crest, and the groundwater level inside of the slope was subsequently varied using two water chambers installed besides the slope model. The fiber optic sensing data of the vertical and horizontal strains within the slope model were automatically recorded by an FBG interrogator and a computer during the test. The test results are presented and interpreted in detail. It is found that the gradually accumulated deformation of the slope model subjected to seepage can be accurately captured by the quasi-distributed FBG strain sensors. The test results also demonstrate that the slope stability is significantly affected by ground water seepage, which fits well with the results that were calculated using finite element and limit equilibrium methods. The relationship between the strain measurements and the safety factors is further analyzed, together with a discussion on the residual strains. The performance evaluation of a soil slope using fiber optic strain sensors is proved to be a potentially effective

Fiber Bragg grating-based performance monitoring of a slope model subjected to seepage

International Nuclear Information System (INIS)

Zhu, Hong-Hu; Shi, Bin; Yan, Jun-Fan; Zhang, Cheng-Cheng; Wang, Bao-Jun; Zhang, Jie

2014-01-01

In the past few years, fiber optic sensing technologies have played an increasingly important role in the health monitoring of civil infrastructures. These innovative sensing technologies have recently been successfully applied to the performance monitoring of a series of geotechnical structures. Fiber optic sensors have shown many unique advantages in comparison with conventional sensors, including immunity to electrical noise, higher precision and improved durability and embedding capabilities; fiber optic sensors are also smaller in size and lighter in weight. In order to explore the mechanism of seepage-induced slope instability, a small-scale 1 g model test of the soil slope has been performed in the laboratory. During the model’s construction, specially fabricated sensing fibers containing nine fiber Bragg grating (FBG) strain sensors connected in a series were horizontally and vertically embedded into the soil mass. The surcharge load was applied on the slope crest, and the groundwater level inside of the slope was subsequently varied using two water chambers installed besides the slope model. The fiber optic sensing data of the vertical and horizontal strains within the slope model were automatically recorded by an FBG interrogator and a computer during the test. The test results are presented and interpreted in detail. It is found that the gradually accumulated deformation of the slope model subjected to seepage can be accurately captured by the quasi-distributed FBG strain sensors. The test results also demonstrate that the slope stability is significantly affected by ground water seepage, which fits well with the results that were calculated using finite element and limit equilibrium methods. The relationship between the strain measurements and the safety factors is further analyzed, together with a discussion on the residual strains. The performance evaluation of a soil slope using fiber optic strain sensors is proved to be a potentially effective

Miniature and low cost fiber Bragg grating interrogator for structural monitoring in nano-satellites

Science.gov (United States)

Toet, P. M.; Hagen, R. A. J.; Hakkesteegt, H. C.; Lugtenburg, J.; Maniscalco, M. P.

2017-11-01

In this paper we present a newly developed Fiber Optic measurement system, consisting of Fiber Bragg Grating (FBG) sensors and an FBG interrogator. The development of the measuring system is part of the PiezoElectric Assisted Smart Satellite Structure (PEASSS) project, which was initiated at the beginning of 2013 and is financed by the Seventh Framework Program (FP7) of the European Commission. Within the PEASSS project, a Nano-Satellite is being designed and manufactured to be equipped with new technology that will help keep Europe on the cutting edge of space research, potentially reducing the cost and development time for more accurate future sensor platforms including synthetic aperture optics, moving target detection and identification, and compact radars. After on ground testing the satellite is planned to be launched at the end of 2015. Within the satellite, different technologies will be demonstrated on orbit to show their capabilities for different in-space applications. For our application the FBG interrogator monitors the structural and thermal behaviour of a so called "smart panel". These panels will enable fine angle control and thermal and vibration compensation in order to improve all types of future Earth observations, such as environmental and planetary mapping, border and regional imaging. The Fiber Optic (FO) system in PEASSS includes four FBG strain sensors and two FBG temperature sensors. The 3 channel interrogator has to have a small footprint (110x50x40mm), is low cost, low in mass and has a low power consumption. In order to meet all these requirements, an interrogator has been designed based on a tunable Vertical-Cavity Surface-Emitting Laser (VCSEL) enabling a wavelength sweep of around 7 nm. To guarantee the absolute and relative performance, two reference methods are included internally in the interrogator. First, stabilized reference FBG sensors are used to obtain absolute wavelength calibrations. This method is used for the temperature

Apodization Optimization of FBG Strain Sensor for Quasi-Distributed Sensing Measurement Applications

Directory of Open Access Journals (Sweden)

Fahd Chaoui

2016-01-01

Full Text Available A novel optimized apodization of Fiber Bragg Grating Sensor (FBGS for quasi-distributed strain sensing applications is developed and introduced in this paper. The main objective of the proposed optimization is to obtain a reflectivity level higher than 90% and a side lobe level around −40 dB, which is suitable for use in quasi-distributed strain sensing application. For this purpose, different design parameters as apodization profile, grating length, and refractive index have been investigated to enhance and optimize the FBGS design. The performance of the proposed apodization has then been compared in terms of reflectivity, side lobe level (SLL, and full width at half maximum (FWHM with apodization profiles proposed by other authors. The optimized sensor is integrated on quasi-distributed sensing system of 8 sensors demonstrating high reliability. Wide strain sensitivity range for each channel has also been achieved in the quasi-distributed system. Results prove the efficiency of the proposed optimization which can be further implemented for any quasi-distributed sensing application.

Fiber Bragg grating fabrication for the implementation of sensors in the electronics and optoelectronics laboratory at BUAP

Science.gov (United States)

Bracamontes Rodríguez, Y. E.; Beltrán Pérez, G.; Castillo Mixcóatl, J.; Muñoz Aguirre, S.

2011-09-01

Fiber Bragg gratings (FBG) are important optical devices since they have been quite successful not only in the field of communications but also in sensor systems and optical fiber lasers. In the sensors area they are generally used as detection elements for different physical parameters such as temperature, strain, flow, etc. In the electronics and optoelectronics laboratory at Benemérita Universidad Autónoma de Puebla (LEyO-BUAP), there are already experimental setups of sensors as well as laser systems, where FBGs are fundamental elements for their adequate performance. However, these FBGs are commercial devices and they present limited characteristics in their transmission profiles, bandwidth and reflectivity. On the other hand, in some occasions, the delivery time from the fabricant to the customer is quite long. Therefore, it is important for LEyO to implement a system to fabricate this kind of devices, which would mean LEyO independence in the technological development. In this work, results of FBGs fabrication based on the phase mask technique are presented. Such mask is optimized for UV and it has a period of 1060 nm. A Nd:YAG pulsed laser with a 5 ns pulse length and an energy of 40 mJ was used as the UV source employing the 4th harmonic generation to obtain a 266 nm wavelength. Ge-doped fiber was used to fabricate the devices.

Employing optical code division multiple access technology in the all fiber loop vibration sensor system

Science.gov (United States)

Tseng, Shin-Pin; Yen, Chih-Ta; Syu, Rong-Shun; Cheng, Hsu-Chih

2013-12-01

This study proposes a spectral amplitude coding-optical code division multiple access (SAC-OCDMA) framework to access the vibration frequency of a test object on the all fiber loop vibration sensor (AFLVS). Each user possesses an individual SAC, and fiber Bragg grating (FBG) encoders/decoders using multiple FBG arrays were adopted, providing excellent orthogonal properties in the frequency domain. The system also mitigates multiple access interference (MAI) among users. When an optical fiber is bent to a point exceeding the critical radius, the fiber loop sensor becomes sensitive to external physical parameters (e.g., temperature, strain, and vibration). The AFLVS involves placing a fiber loop with a specific radius on a designed vibration platform.

Experimental demonstration of a ferroelectric liquid crystal tunable filter for fast demodulation of FBG sensors

Science.gov (United States)

Mathews, Sunish; Semenova, Yuliya; Rajan, Ginu; Farrell, Gerald

2009-05-01

A discretely tunable Surface-Stabilized Ferroelectric Liquid Crystal based Lyot Filter, with tuning speeds in the order of microseconds, is demonstrated experimentally as a channel dropper for the demodulation of multiple Fibre Bragg Grating sensors. The 3-stage Lyot Filter designed and experimentally verified can be used together with the high-speed ratiometric wavelength measurement system employing a fibre bend loss edge filter. Such systems can be used for the demodulation of distributed Fibre Bragg Grating sensors employed in applications such as structural monitoring, industrial sensing and haptic telerobotic surgical systems.

Optical detection of glucose and glycated hemoglobin using etched fiber Bragg gratings coated with functionalized reduced graphene oxide.

Science.gov (United States)

Sridevi, S; Vasu, K S; Sampath, S; Asokan, S; Sood, A K

2016-07-01

An enhanced optical detection of D-glucose and glycated hemoglobin (HbA1c ) has been established in this study using etched fiber Bragg gratings (eFBG) coated with aminophenylboronic acid (APBA)-functionalized reduced graphene oxide (RGO). The read out, namely the shift in Bragg wavelength (ΔλB ) is highly sensitive to changes that occur due to the adsorption of glucose (or HbA1c ) molecules on the eFBG sensor coated with APBA-RGO complex through a five-membered cyclic ester bond formation between glucose and APBA molecules. A limit of detection of 1 nM is achieved with a linear range of detection from 1 nM to 10 mM in the case of D-glucose detection experiments. For HbA1c , a linear range of detection varying from 86 nM to 0.23 mM is achieved. The observation of only 4 pm (picometer) change in ΔλB even for the 10 mM lactose solution confirms the specificity of the APBA-RGO complex coated eFBG sensors to glucose molecules. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Optical Fiber Sensors Based on Fiber Ring Laser Demodulation Technology.

Science.gov (United States)

Xie, Wen-Ge; Zhang, Ya-Nan; Wang, Peng-Zhao; Wang, Jian-Zhang

2018-02-08

A review for optical fiber sensors based on fiber ring laser (FRL) demodulation technology is presented. The review focuses on the principles, main structures, and the sensing performances of different kinds of optical fiber sensors based on FRLs. First of all, the theory background of the sensors has been discussed. Secondly, four different types of sensors are described and compared, which includes Mach-Zehnder interferometer (MZI) typed sensors, Fabry-Perot interferometer (FPI) typed sensors, Sagnac typed sensors, and fiber Bragg grating (FBG) typed sensors. Typical studies and main properties of each type of sensors are presented. Thirdly, a comparison of different types of sensors are made. Finally, the existing problems and future research directions are pointed out and analyzed.

Study on the weighing system based on optical fiber Bragg grating

Science.gov (United States)

Wang, Xiaona; Yu, Qingxu; Li, Yefang

2010-10-01

The optical fiber sensor based on wavelength demodulation such as fiber Bragg grating(FBG), with merits of immunity to electromagnetic interference, low drift and high precision, has been widely used in many areas, such as structural health monitoring and smart materials, and the wavelength demodulation system was also studied widely. In the paper, a weighing system based on FBG was studied. The optical source is broadband Erbium-doped fiber ring laser with a spectral range of 1500~1600nm and optical power of 2mW; A Fabry-Perot Etalon with orientation precision of 1pm was adopted as real-time wavelength calibration for the swept laser; and multichannel high resolution simultaneous sampling card was used in the system to acquire sensing signals simultaneously, thus high-resolution and real-time calibration of sweep-wavelength can be achieved. The FBG was adhered to a cantilever beam and the Bragg wavelength was demodulated with the system. The weighing system was done after calibrated with standard weight. Experimental results show that the resolution of the weighing system is 0.5 g with a full scale of 2Kg.

Tunability of the FBG group delay through acousto-optic modulation

Science.gov (United States)

Marques, Carlos A. F.; Oliveira, Roberson A.; Pohl, Alexandre A. P.; Nogueira, Rogério N.

2013-03-01

A new method for fine control of the group delay of a fiber Bragg grating (FBG) is presented. It is based on an acoustic wave applied to the fiber. The standing acoustic wave imposes a periodic chirp to the uniform FBG. Tunability is obtained through adjustment of the intensity and/or frequency of the acoustic wave. A fast switching time of ∼17 μs was achieved. The experimental results were verified by theoretical simulation showing a good agreement between them. It can be used for different applications such as tunable narrow dispersion compensator for independent coarse wavelength division multiplexing (CWDM) channels or optical delay lines.

Influence on Calculated Blood Pressure of Measurement Posture for the Development of Wearable Vital Sign Sensors

Directory of Open Access Journals (Sweden)

Shouhei Koyama

2017-01-01

Full Text Available We studied a wearable blood pressure sensor using a fiber Bragg grating (FBG sensor, which is a highly accurate strain sensor. This sensor is installed at the pulsation point of the human body to measure the pulse wave signal. A calibration curve is built that calculates the blood pressure by multivariate analysis using the pulse wave signal and a reference blood pressure measurement. However, if the measurement height of the FBG sensor is different from the reference measurement height, an error is included in the reference blood pressure. We verified the accuracy of the blood pressure calculation with respect to the measurement height difference and the posture of the subject. As the difference between the measurement height of the FBG sensor and the reference blood pressure measurement increased, the accuracy of the blood pressure calculation decreased. When the measurement height was identical and only posture was changed, good accuracy was achieved. In addition, when calibration curves were built using data measured in multiple postures, the blood pressure of each posture could be calculated from a single calibration curve. This will allow miniaturization of the necessary electronics of the sensor system, which is important for a wearable sensor.

Tactile Sensor Array with Fiber Bragg Gratings in Quasi-Distributed Sensing

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Marcelo A. Pedroso

2018-01-01

Full Text Available This work describes the development of a quasi-distributed real-time tactile sensing system with a reduced number of fiber Bragg grating-based sensors and reports its use with a reconstruction method based on differential evolution. The sensing system is comprised of six fiber Bragg gratings encapsulated in silicone elastomer to form a tactile sensor array with total dimensions of 60 × 80 mm, divided into eight sensing cells with dimensions of 20 × 30 mm. Forces applied at the central position of the sensor array resulted in linear response curves for the gratings, highlighting their coupled responses and allowing the application of compressive sensing. The reduced number of sensors regarding the number of sensing cells results in an undetermined inverse problem, solved with a compressive sensing algorithm with the aid of differential evolution method. The system is capable of identifying and quantifying up to four different loads at four different cells with relative errors lower than 10.5% and signal-to-noise ratio better than 12 dB.

In-situ monitoring of curing and ageing effects in FRP plates using embedded FBG sensors

Science.gov (United States)

Xian, Guijun; Wang, Chuan; Li, Hui

2010-04-01

In recent years, fiber reinforced polymer (FRP) composites have been widely applied in civil engineering for retrofitting or renewal of existing structures. Since FRP composite may degrade when exposed to severe outdoor environments, a serious concern has been raised on its long term durability. In the present study, fiber Bragg grating (FBG) sensors were embedded in glass-, carbon- and basalt-fiber reinforced epoxy based FRP plates with wet lay-up technology, to in-situ monitor the stain changes in FRPs during the curing, and water immersion and freeze-thaw ageing processes. The study demonstrates that the curing of epoxy resin brings in a slight tension strain (e.g., 10 ~ 30 μɛ) along the fiber direction and a high contraction (e.g., ~ 1100μɛ) in the direction perpendicular to the fibers, mainly due to the resin shrinkage. The cured FRP strips were then subjected to distilled water immersion at 80oC and freeze-thaw cycles from -30°C to 30°C. Remarkable strain changes of FRPs due to the variation of the temperatures during freeze-thaw cycles indicate the potential property degradation from fatigue. The maximum strain change is dependent on the fiber types and directions to the fiber. Based on the monitored strain values with temperature change and water uptake content, CTE (coefficient of thermal expansion) and CME (coefficient of moisture expansion) are exactly determined for the FRPs.

Detection of premature browning in ground beef with an integrated optical-fibre based sensor using reflection spectroscopy and fibre Bragg grating technology

International Nuclear Information System (INIS)

O'Farrell, M; Sheridan, C; Lewis, E

2007-01-01

This paper reports on an optical fibre based sensor system to detect the occurrence of premature browning in ground beef. Premature browning (PMB) occurs when, at a temperature below the pasteurisation temperature of 71 deg. C, there are no traces of pink meat left in the patty. PMB is more frequent if poorer quality beef or beef that has been stored under imperfect conditions. The experimental work pertaining to this paper involved cooking fresh meat and meat that has been stored in a freezer for, 1 week, 1 month and 3 months and recording the reflected spectra and temperature at the core of the product, during the cooking process, in order to develop a classifier based on the spectral response and using a Self-Organising Map (SOM) to classify the patties into one of four categories, based on their colour. Further tests were also carried out on developing an all-optical fibre sensor for measuring both the temperature and colour in a single integrated probe. The integrated probe contains two different sensor concepts, one to monitor temperature, based on Fibre Bragg Grating (FBG) technology and a second for meat quality, based on reflection spectroscopy in the visible wavelength range

Angle transducer based on fiber Bragg gratings able for tunnel auscultation

Science.gov (United States)

Quintela, A.; Lázaro, J. M.; Quintela, M. A.; Mirapeix, J.; Muñoz-Berti, V.; López-Higuera, J. M.

2010-09-01

In this paper an angle transducer based on Fiber Bragg Grating (FBG) is presented. Two gratings are glued to a metallic platen, one in each side. It is insensitive to temperature changes, given that the temperature shifts affect equally to both FBG. When the platen is uniformly bent an uniform strain appears in both sides of the platen. It depends on the bend angle and the platen length and thickness. The transducer has been designed to be used in the auscultation of tunnels during their construction process and during their live time. The transducer design and its characterization are presented.

Design Parameter Optimization of a Silicon-Based Grating Waveguide for Performance Improvement in Biochemical Sensor Application.

Science.gov (United States)

Hong, Yoo-Seung; Cho, Chun-Hyung; Sung, Hyuk-Kee

2018-03-05

We performed numerical analysis and design parameter optimization of a silicon-based grating waveguide refractive index (RI) sensor. The performance of the grating waveguide RI sensor was determined by the full-width at half-maximum (FWHM) and the shift in the resonance wavelength in the transmission spectrum. The transmission extinction, a major figure-of-merit of an RI sensor that reflects both FWHM and resonance shift performance, could be significantly improved by the proper determination of three major grating waveguide parameters: duty ratio, grating period, and etching depth. We analyzed the transmission characteristics of the grating waveguide under various design parameter conditions using a finite-difference time domain method. We achieved a transmission extinction improvement of >26 dB under a given bioenvironmental target change by the proper choice of the design procedure and parameters. This design procedure and choice of appropriate parameters would enable the widespread application of silicon-based grating waveguide in high-performance RI biochemical sensor.

Fibre Bragg grating based accelerometer with extended bandwidth

International Nuclear Information System (INIS)

Basumallick, Nandini; Biswas, Palas; Dasgupta, Kamal; Bandyopadhyay, Somnath; Chakraborty, Rajib; Chakraborty, Sushanta

2016-01-01

We have shown experimentally that the operable bandwidth of a fibre Bragg grating (FBG) based accelerometer can be extended significantly, without compromising its sensitivity, using a post-signal processing technique which involves frequency domain weighting. It has been demonstrated that using the above technique acceleration can be correctly interpreted even when the operating frequency encroaches on the region where the frequency response of the sensor is non-uniform. Two different excitation signals, which we often encounter in structural health monitoring applications, e.g. (i) a signal composed of multi-frequency components and (ii) a sinusoidal excitation with a frequency sweep, have been considered in our experiment. The results obtained have been compared with a piezo accelerometer. (paper)

Bragg Grating Based Sensors in Microstructured Polymer Optical Fibers: Accelerometers and Microphones

DEFF Research Database (Denmark)

Stefani, Alessio

With the growing interest towards fiber Bragg grating sensors and the growing ability in manufacturing polymer optical fibers, the development of polymer fiber Bragg sensors has catched the attention of industries with the goal of developing high performance sensors. This thesis presents...... and in microstructured fibers made of PMMA and TOPAS is reported. The gratings have been written at both 1550 nm, to take advantage of components made for telecommunications, and 850 nm, to exploit the lower loss of polymers and the fast acquisition electronics at this wavelength. A technique for writing multiplexed...

Simultaneous measurement of magnetic field and temperature based on an etched TCFMI cascaded with an FBG

Science.gov (United States)

Yan, Guofeng; Zhang, Liang; He, Sailing

2016-04-01

In this paper, a dual-parameter measurement scheme based on an etched thin core fiber modal interferometer (TCMI) cascaded with a fiber Bragg grating (FBG) is proposed and experimentally demonstrated for simultaneous measurement of magnetic field and temperature. The magnetic field and temperature responses of the packaged TCFMI were first investigated, which showed that the magnetic field sensitivity could be highly enhanced by decreasing of the TCF diameter and the temperature-cross sensitivities were up to 3-7 Oe/°C at 1550 nm. Then, the theoretical analysis and experimental demonstration of the proposed dual-parameter sensing scheme were conducted. Experimental results show that, the reflection of the FBG has a magnetic field intensity and temperature sensitivities of -0.017 dB/Oe and 0.133 dB/°C, respectively, while the Bragg wavelength of the FBG is insensitive to magnetic field and has a temperature sensitivity of 13.23 pm/°C. Thus by using the sensing matrix method, the intensity of the magnetic field and the temperature variance can be measured, which enables magnetic field sensing under strict temperature environments. In the on-off time response test, the fabricated sensor exhibited high repeatability and short response time of ∼19.4 s. Meanwhile the reflective sensing probe type is more compact and practical for applications in hard-to-reach conditions.

Casing Pipe Damage Detection with Optical Fiber Sensors: A Case Study in Oil Well Constructions

Directory of Open Access Journals (Sweden)

Zhi Zhou

2010-01-01

Full Text Available Casing pipes in oil well constructions may suddenly buckle inward as their inside and outside hydrostatic pressure difference increases. For the safety of construction workers and the steady development of oil industries, it is critically important to measure the stress state of a casing pipe. This study develops a rugged, real-time monitoring, and warning system that combines the distributed Brillouin Scattering Time Domain Reflectometry (BOTDR and the discrete fiber Bragg grating (FBG measurement. The BOTDR optical fiber sensors were embedded with no optical fiber splice joints in a fiber-reinforced polymer (FRP rebar and the FBG sensors were wrapped in epoxy resins and glass clothes, both installed during the segmental construction of casing pipes. In situ tests indicate that the proposed sensing system and installation technique can survive the downhole driving process of casing pipes, withstand a harsh service environment, and remain intact with the casing pipes for compatible strain measurements. The relative error of the measured strains between the distributed and discrete sensors is less than 12%. The FBG sensors successfully measured the maximum horizontal principal stress with a relative error of 6.7% in comparison with a cross multipole array acoustic instrument.

Integrated optical electric field sensor based on a Bragg grating in lithium niobate

Science.gov (United States)

Runde, D.; Brunken, S.; Rüter, C. E.; Kip, D.

2007-01-01

We demonstrate a new sensor concept for the measurement of oscillating electric fields that is based on Bragg gratings in LiNbO3:Ti channel waveguides. This miniaturized sensor that works in a retroreflective scheme does not require metallic electrodes and can be directly immersed in an oscillating electric field. The electric field induces a shift of the Bragg wavelength of the reflection grating that is due to the electro-optic effect. The operating point of the sensor is chosen by adjusting the laser wavelength to the slope of the spectral reflectivity function of the grating. In this way the magnitude of an external electric field is measured precisely as the amplitude of modulated reflected light intensity by using a lock-in amplifier. The sensor principle is demonstrated by detecting low-frequency electric fields ranging from 50 V/cm to 5 kV/cm without any conducting parts of the sensor head. Furthermore, the ability of the sensor to determine the three-dimensional orientation of an external electric field by a single rotation along the waveguide direction is demonstrated.

Aviation Fuel Gauging Sensor Utilizing Multiple Diaphragm Sensors Incorporating Polymer Optical Fiber Bragg Gratings

DEFF Research Database (Denmark)

Marques, C. A. F.; Pospori, A.; Saez-Rodriguez, D.

2016-01-01

A high-performance fuel gauging sensor is described that uses five diaphragm-based pressure sensors, which are monitored using a linear array of polymer optical fiber Bragg gratings. The sensors were initially characterized using water, revealing a sensitivity of 98 pm/cm for four of the sensors...... of sensors manufactured with a polyurethane-based diaphragm showed no measurable deterioration over a three month period immersed in fuel. These sensors exhibited a sensitivity of 39 pm/cm, which is less than the silicone rubber devices due to the stiffer nature of the polyurethane material used....

Monitoring the Damage State of Fiber Reinforced Composites Using an FBG Network for Failure Prediction

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Esat Selim Kocaman

2017-01-01

Full Text Available A structural health monitoring (SHM study of biaxial glass fibre-reinforced epoxy matrix composites under a constant, high strain uniaxial fatigue loading is performed using fibre Bragg grating (FBG optical sensors embedded in composites at various locations to monitor the evolution of local strains, thereby understanding the damage mechanisms. Concurrently, the temperature changes of the samples during the fatigue test have also been monitored at the same locations. Close to fracture, significant variations in local temperatures and strains are observed, and it is shown that the variations in temperature and strain can be used to predict imminent fracture. It is noted that the latter information cannot be obtained using external strain gages, which underlines the importance of the tracking of local strains internally.

Effects of the inclined femto laser incidence at the phase mask on FBG carving

Science.gov (United States)

Wang, Jian; Wu, Shengli; Zhang, Jintao; Ren, Wenyi

2015-12-01

The inclined incidence of the femto laser on the phase mask in fiber Bragg grating (FBG) carving has a significant effect on the quality of FBG fabrication. Based on that the infrared femto laser has highly spatial coherence and the order walk-off will happen behind the phase mask, the interferogram generated at the fiber core by the inclined femto laser beam has been analyzed using the multi-beam interference principle. The influence of beam inclination on the coherence of the 0th and ± 1st orders diffraction with different exposure distance, the visibility of interferogram and the frequency component of the transverse interferogram intensity has also been analyzed. It is meaningful for the FBG fabricating with the femto laser.

Monitoring Ingress of Moisture in Structural Concrete Using a Novel Optical-Based Sensor Approach

International Nuclear Information System (INIS)

Yeo, T L; Cox, M A C; Boswell, L F; Sun, T; Grattan, K T V

2006-01-01

The detection of moisture ingress in concrete is important for structural monitoring and in this work is realised by monitoring the shift in the characteristic wavelength of a fibre Bragg grating-based sensor. The sensor relies upon a moisture-sensitive polymer layer deposited on the fibre Bragg grating (FBG) and the strain induced on it as a result of polymer swelling is monitored. Moisture ingress experiments were carried out using two such optical fibre sensors, placed at varying distances from the edge of the face of standard concrete cubes to the inner part of the concrete sample and subjected to water at a constant temperature. Information on the properties of different types of concrete and thus potentially on the migration of dissolved salts and their effect on reinforcement bars within concrete can be obtained

Temperature-insensitive fiber Bragg grating dynamic pressure sensing system.

Science.gov (United States)

Guo, Tuan; Zhao, Qida; Zhang, Hao; Zhang, Chunshu; Huang, Guiling; Xue, Lifang; Dong, Xiaoyi

2006-08-01

Temperature-insensitive dynamic pressure measurement using a single fiber Bragg grating (FBG) based on reflection spectrum bandwidth modulation and optical power detection is proposed. A specifically designed double-hole cantilever beam is used to provide a pressure-induced axial strain gradient along the sensing FBG and is also used to modulate the reflection bandwidth of the grating. The bandwidth modulation is immune to spatially uniform temperature effects, and the pressure can be unambiguously determined by measuring the reflected optical power, avoiding the complex wavelength interrogation system. The system acquisition time is up to 85 Hz for dynamic pressure measurement, and the thermal fluctuation is kept less than 1.2% full-scale for a temperature range of -10 degrees C to 80 degrees C.

Design of high-order all-optical temporal differentiators based on multiple-phase-shifted fiber Bragg gratings.

Science.gov (United States)

Kulishov, Mykola; Azaña, José

2007-05-14

A simple and general approach for designing practical all-optical (all-fiber) arbitrary-order time differentiators is introduced here for the first time. Specifically, we demonstrate that the Nth time derivative of an input optical waveform can be obtained by reflection of this waveform in a single uniform fiber Bragg grating (FBG) incorporating N &pi-phase shifts properly located along its grating profile. The general design procedure of an arbitrary-order optical time differentiator based on a multiple-phase-shifted FBG is described and numerically demonstrated for up to fourth-order time differentiation. Our simulations show that the proposed approach can provide optical operation bandwidths in the tens-of-GHz regime using readily feasible FBG structures.

Embedded Bragg grating fiber optic sensor for composite flexbeams

Science.gov (United States)

Bullock, Daniel; Dunphy, James; Hufstetler, Gerard

1993-03-01

An embedded fiber-optic (F-O) sensor has been developed for translaminar monitoring of the structural integrity of composites, with a view to application in composite helicopter flexbeams for bearingless main rotor hubs. This through-thickness strain sensor is much more sensitive than conventional in-plane embedded F-O sensors to ply delamination, on the basis of a novel insertion technique and innovative Bragg grating sensor. Experimental trials have demonstrated the detection by this means of potential failures in advance of the edge-delamination or crack-propagation effect.

Application of Notched Long-Period Fiber Grating Based Sensor for CO2 Gas Sensing

Science.gov (United States)

Wu, Chao-Wei; Chiang, Chia-Chin

2016-01-01

An inductively coupled plasma etching process to fabricate notched long-period fiber gratings for CO2 gas sensing is proposed in this article. In the gas sensing test, the 15% mixed CO2 gas was used for characterization of CO2 adsorption by the amine-modified nanoporous silica foams of the notched long-period fiber grating sensor. The results shows the spectra were changed with the CO2 gas flow within 13 min. During the absorption process, the transmission of the resonant dip was decreased by 2.884 dB. Therefore, the proposed notched long-period fiber grating gas sensor shows good performance and is suitable as a gas sensor for monitoring the CO2 adsorption process.

Fast Interrogation of Fiber Bragg Gratings with Electro-Optical Dual Optical Frequency Combs.

Science.gov (United States)

Posada-Roman, Julio E; Garcia-Souto, Jose A; Poiana, Dragos A; Acedo, Pablo

2016-11-26

Optical frequency combs (OFC) generated by electro-optic modulation of continuous-wave lasers provide broadband coherent sources with high power per line and independent control of line spacing and the number of lines. In addition to their application in spectroscopy, they offer flexible and optimized sources for the interrogation of other sensors based on wavelength change or wavelength filtering, such as fiber Bragg grating (FBG) sensors. In this paper, a dual-OFC FBG interrogation system based on a single laser and two optical-phase modulators is presented. This architecture allows for the configuration of multimode optical source parameters such as the number of modes and their position within the reflected spectrum of the FBG. A direct read-out is obtained by mapping the optical spectrum onto the radio-frequency spectrum output of the dual-comb. This interrogation scheme is proposed for measuring fast phenomena such as vibrations and ultrasounds. Results are presented for dual-comb operation under optimized control. The optical modes are mapped onto detectable tones that are multiples of 0.5 MHz around a center radiofrequency tone (40 MHz). Measurements of ultrasounds (40 kHz and 120 kHz) are demonstrated with this sensing system. Ultrasounds induce dynamic strain onto the fiber, which generates changes in the reflected Bragg wavelength and, hence, modulates the amplitude of the OFC modes within the reflected spectrum. The amplitude modulation of two counterphase tones is detected to obtain a differential measurement proportional to the ultrasound signal.

Fast Interrogation of Fiber Bragg Gratings with Electro-Optical Dual Optical Frequency Combs

Directory of Open Access Journals (Sweden)

Julio E. Posada-Roman

2016-11-01

Full Text Available Optical frequency combs (OFC generated by electro-optic modulation of continuous-wave lasers provide broadband coherent sources with high power per line and independent control of line spacing and the number of lines. In addition to their application in spectroscopy, they offer flexible and optimized sources for the interrogation of other sensors based on wavelength change or wavelength filtering, such as fiber Bragg grating (FBG sensors. In this paper, a dual-OFC FBG interrogation system based on a single laser and two optical-phase modulators is presented. This architecture allows for the configuration of multimode optical source parameters such as the number of modes and their position within the reflected spectrum of the FBG. A direct read-out is obtained by mapping the optical spectrum onto the radio-frequency spectrum output of the dual-comb. This interrogation scheme is proposed for measuring fast phenomena such as vibrations and ultrasounds. Results are presented for dual-comb operation under optimized control. The optical modes are mapped onto detectable tones that are multiples of 0.5 MHz around a center radiofrequency tone (40 MHz. Measurements of ultrasounds (40 kHz and 120 kHz are demonstrated with this sensing system. Ultrasounds induce dynamic strain onto the fiber, which generates changes in the reflected Bragg wavelength and, hence, modulates the amplitude of the OFC modes within the reflected spectrum. The amplitude modulation of two counterphase tones is detected to obtain a differential measurement proportional to the ultrasound signal.

Advances in Fiber Optic Sensors Technology Development for temperature and strain measurements in Superconducting magnets and devices

CERN Document Server

Chiuchiolo, A.; Bajko, M.; Bottura, L.; Consales, M.; Cusano, A.; Giordano, M.; Perez, J. C.

2016-01-01

The luminosity upgrade of the Large Hadron Collider (HL-LHC) requires the development of a new generation of superconducting magnets based on Nb$_{3}$Sn technology. In order to monitor the magnet thermo-mechanical behaviour during its service life, from the coil fabrication to the magnet operation, reliable sensing systems need to be implemented. In the framework of the FP7 European project EUCARD, Nb$_{3}$Sn racetrack coils are developed as test beds for the fabrication validation, the cable characterization and the instrumentation development. Fiber optic sensors (FOS) based on Fiber Bragg Grating (FBG) technology have been embedded in the coils of the Short Model Coil (SMC) magnet. The FBG sensitivity to both temperature and strain required the development of a solution able to separate the mechanical and temperature effects. This work presents the feasibility study of the implementation of embedded FBG sensors for the temperature and strain monitoring of the 11 T type conductor. We aim to monitor and regi...

An in-fiber Bragg grating sensor for contact force and stress measurements in articular joints

International Nuclear Information System (INIS)

Dennison, Christopher R; Wild, Peter M; Wilson, David R; Gilbart, Michael K

2010-01-01

We present an in-fiber Bragg grating-based sensor (240 µm diameter) for contact force/stress measurements in articular joints. The contact force sensor and another Bragg grating-based pressure sensor (400 µm diameter) are used to conduct the first simultaneous measurements of contact force/stress and fluid pressure in intact cadaveric human hips. The contact force/stress sensor addresses limitations associated with stress-sensitive films, the current standard tools for contact measurements in joints, including cartilage modulus-dependent sensitivity of films and the necessity to remove biomechanically relevant anatomy to implant the films. Because stress-sensitive films require removal of anatomy, it has been impossible to validate the mechanical rationale underlying preventive or corrective surgeries, which repair these anatomies, by conducting simultaneous stress and pressure measurements in intact hips. Methods are presented to insert the Bragg grating-based sensors into the joint, while relevant anatomy is left largely intact. Sensor performance is predicted using numerical models and the predicted sensitivity is verified through experimental calibrations. Contact force/stress and pressure measurements in cadaveric joints exhibited repeatability. With further validation, the Bragg grating-based sensors could be used to study the currently unknown relationships between contact forces and pressures in both healthy and degenerated joints

BDK-doped core microstructured PMMA optical fiber for effective Bragg grating photo-inscription

DEFF Research Database (Denmark)

Hu, Xuehao; Woyessa, Getinet; Kinet, Damien

2017-01-01

An endlessly single-mode doped microstructured poly(methyl methacrylate) (PMMA) optical fiber is produced for effective fiber Bragg grating (FBG) photo-inscription by means of a 400 nm femtosecond pulsed laser and the phase mask technique. The fiber presents a uniform benzyl dimethyl ketal (BDK......) distribution in its core without drastic loss increase. It was produced using the selected center hole doping technique, and the BDK dopant acts as a photoinitiator. In this Letter, we report a rapidly growing process of the grating reflection band. For an 11 mW mean laser power, the FBG reflectivity reaches...

A Self-Referenced Optical Intensity Sensor Network Using POFBGs for Biomedical Applications

Directory of Open Access Journals (Sweden)

Alberto Tapetado Moraleda

2014-12-01

Full Text Available This work bridges the gap between the remote interrogation of multiple optical sensors and the advantages of using inherently biocompatible low-cost polymer optical fiber (POF-based photonic sensing. A novel hybrid sensor network combining both silica fiber Bragg gratings (FBG and polymer FBGs (POFBG is analyzed. The topology is compatible with WDM networks so multiple remote sensors can be addressed providing high scalability. A central monitoring unit with virtual data processing is implemented, which could be remotely located up to units of km away. The feasibility of the proposed solution for potential medical environments and biomedical applications is shown.

A self-referenced optical intensity sensor network using POFBGs for biomedical applications.

Science.gov (United States)

Tapetado Moraleda, Alberto; Sánchez Montero, David; Webb, David J; Vázquez García, Carmen

2014-12-12

This work bridges the gap between the remote interrogation of multiple optical sensors and the advantages of using inherently biocompatible low-cost polymer optical fiber (POF)-based photonic sensing. A novel hybrid sensor network combining both silica fiber Bragg gratings (FBG) and polymer FBGs (POFBG) is analyzed. The topology is compatible with WDM networks so multiple remote sensors can be addressed providing high scalability. A central monitoring unit with virtual data processing is implemented, which could be remotely located up to units of km away. The feasibility of the proposed solution for potential medical environments and biomedical applications is shown.

Ultrafast all-optical integrator based on a fiber Bragg grating: proposal and design.

Science.gov (United States)

Preciado, Miguel A; Muriel, Miguel A

2008-06-15

We demonstrate a simple technique for the implementation of an all-optical integrator based on a uniform-period fiber Bragg grating (FBG) in reflection that is designed to present a decreasing exponential impulse response. The proposed FBG integrator is readily feasible and can perform close to ideal integration of few-picosecond and subpicosecond pulses.

Fiber-optic refractometer based on an etched high-Q π-phase-shifted fiber-Bragg-grating.

Science.gov (United States)

Zhang, Qi; Ianno, Natale J; Han, Ming

2013-07-10

We present a compact and highly-sensitive fiber-optic refractometer based on a high-Q π-phase-shifted fiber-Bragg-grating (πFBG) that is chemically etched to the core of the fiber. Due to the p phase-shift, a strong πFBG forms a high-Q optical resonator and the reflection spectrum features an extremely narrow notch that can be used for highly sensitivity refractive index measurement. The etched πFBG demonstrated here has a diameter of ~9.3 μm and a length of only 7 mm, leading to a refractive index responsivity of 2.9 nm/RIU (RIU: refractive index unit) at an ambient refractive index of 1.318. The reflection spectrum of the etched πFBG features an extremely narrow notch with a linewidth of only 2.1 pm in water centered at ~1,550 nm, corresponding to a Q-factor of 7.4 × 10(5), which allows for potentially significantly improved sensitivity over refractometers based on regular fiber Bragg gratings.

A distributed fluid level sensor suitable for monitoring fuel load on board a moving fuel tank

Science.gov (United States)

Arkwright, John W.; Parkinson, Luke A.; Papageorgiou, Anthony W.

2018-02-01

A temperature insensitive fiber Bragg grating sensing array has been developed for monitoring fluid levels in a moving tank. The sensors are formed from two optical fibers twisted together to form a double helix with pairs of fiber Bragg gratings located above one another at the points where the fibers are vertically disposed. The sensing mechanism is based on a downwards deflection of the section of the double helix containing the FBGs which causes the tension in the upper FBG to decrease and the tension in the lower FBG to increase with concomitant changes in Bragg wavelength in each FBG. Changes in ambient temperature cause a common mode increase in Bragg wavelength, thus monitoring the differential change in wavelength provides a temperature independent measure of the applied pressure. Ambient temperature can be monitored simultaneously by taking the average wavelength of the upper and lower FBGs. The sensors are able to detect variations in pressure with resolutions better than 1 mmH2O and when placed on the bottom of a tank can be used to monitor fluid level based on the recorded pressure. Using an array of these sensors located along the bottom of a moving tank it was possible to monitor the fluid level at multiple points and hence dynamically track the total fluid volume in the tank. The outer surface of the sensing array is formed from a thin continuous Teflon sleeve, making it suitable for monitoring the level of volatile fluids such as aviation fuel and gasoline.

Experimental Investigation of a Self-Sensing Hybrid GFRP-Concrete Bridge Superstructure with Embedded FBG Sensors

OpenAIRE

Wang, Yanlei; Li, Yunyu; Ran, Jianghua; Cao, Mingmin

2012-01-01

A self-sensing hybrid GFRP-concrete bridge superstructure, which consists of two bridge decks and each bridge deck is comprised of four GFRP box sections combined with a thin layer of concrete in the compression zone, was developed by using eight embedded FBG sensors in the top and bottom flanges of the four GFRP box sections at midspan section of one bridge deck along longitudinal direction, respectively. The proposed self-sensing hybrid bridge superstructure was tested in 4-point loading to...

Simultaneous measurement of temperature and strain using a phase-shifted fiber Bragg grating inscribed by femtosecond laser

Science.gov (United States)

Jiang, Yajun; Liu, Chi; Li, Dong; Yang, Dexing; Zhao, Jianlin

2018-04-01

A novel method for simultaneous measurement of temperature and strain using a single phase-shifted fiber Bragg grating (PS-FBG) is proposed. The PS-FBG is produced by exposing the fusion-spliced fiber with a femtosecond laser and uniform phase mask. Due to the non-uniform structure and strain distribution in the fusion-spliced region, the phase-shift changes with different responses during increases to the temperature and strain; by measuring the central wavelengths and the loss difference of two transmission dips, temperature and strain can be determined simultaneously. The resolutions of this particular sensor in measuring temperature and strain are estimated to be  ±1.5 °C and  ±12.2 µɛ in a range from  -50 °C to 150 °C and from 0 µɛ to 2070 µɛ.

Water Vapor Sensors Based on the Swelling of Relief Gelatin Gratings

Directory of Open Access Journals (Sweden)

Sergio Calixto

2015-01-01

Full Text Available We report on a novel device to measure relative humidity. The sensor is based on surface diffraction gratings made of gelatin. This material swells and shrinks according to the content of water vapor in air. By sending a light beam to the grating, diffracted orders appear. Due to the gelatin swelling or shrinking, first order intensity changes according to the relative humidity. Calibration curves relating intensity versus relative humidity have been found. The fabrication process of diffraction gratings and the testing of the prototype sensing devices are described.

Design and development of long-period grating sensors for ...

Indian Academy of Sciences (India)

Raja Ramanna Centre for Advanced Technology, Indore 450 213. ∗ e-mail: ... Home built CO2 laser (Max power 20 Watt) is focused onto .... Claus R O 1997 Temperature-insensitive and strain insensitive long-period grating sensors for smart.

Microcavity-coupled fiber Bragg grating with tunable reflection spectra and speed of light.

Science.gov (United States)

Chen, Lei; Han, Ya; Liu, Qian; Liu, Yan-Ge; Zhang, Weigang; Chou, Keng C

2018-04-15

After a fiber Bragg grating (FBG) is fabricated, the reflection spectrum of the FBG is generally not tunable without mechanical deformation or temperature adjustment. Here we present a microcavity-coupled FBG with both a tunable reflection lineshape and dispersion using electromagnetically induced transparency. The Fano interference of light in the FBG and the microcavity allows for dramatic modification of the reflection spectrum. The phase of the reflected spectrum is continuously tunable between 0 and 2π to produce various Fano lineshapes. The dispersion of the output light is adjustable from normal dispersion to abnormal dispersion, consequently providing an adjustable speed of light. Additionally, it allows the FBG to switch from a notch filter to a bandpass filter at the resonant wavelength, which is not possible in a conventional uniform FBG.

Optical fiber Bragg grating-instrumented silicone liner for interface pressure measurement within prosthetic sockets of lower-limb amputees

Science.gov (United States)

Al-Fakih, Ebrahim; Arifin, Nooranida; Pirouzi, Gholamhossein; Mahamd Adikan, Faisal Rafiq; Shasmin, Hanie Nadia; Abu Osman, Noor Azuan

2017-08-01

This paper presents a fiber Bragg grating (FBG)-instrumented prosthetic silicone liner that provides cushioning for the residual limb and can successfully measure interface pressures inside prosthetic sockets of lower-limb amputees in a simple and practical means of sensing. The liner is made of two silicone layers between which 12 FBG sensors were embedded at locations of clinical interest. The sensors were then calibrated using a custom calibration platform that mimics a real-life situation. Afterward, a custom gait simulating machine was built to test the liner performance during an amputee's simulated gait. To validate the findings, the results were compared to those obtained by the commonly used F-socket mats. As the statistical findings reveal, both pressure mapping methods measured the interface pressure in a consistent way, with no significant difference (P-values ≥0.05). This pressure mapping technique in the form of a prosthetic liner will allow prosthetics professionals to quickly and accurately create an overall picture of the interface pressure distribution inside sockets in research and clinical settings, thereby improving the socket fit and amputee's satisfaction.

Studies on measurement of chloride ion concentration in concrete structures with long-period grating sensors

Science.gov (United States)

Tang, Jaw-Luen; Chiang, Tsung-Yu; Chang, Hsiang-Ping; Wang, Jian-Neng

2006-03-01

We report the development and demonstration of a simple and low-cost long-period grating (LPG) sensor for chloride ion concentration measurement in concrete structures. The LPG sensor is extremely sensitive to the refractive index of the medium surrounding the cladding surface of the sensing grating, thus allowing it to be used as an ambient index sensor or chemical concentration indicator with high stability and reliability. We have measured chloride ion levels in a concrete sample immersed in salt water solution with different weight concentration ranging from 0 % to 20 %, and results showed that the LPG sensor exhibited a linear decrease in the transmission loss and resonance wavelength shift when the concentration increased. The measurement accuracy for concentration of salt in water solution is estimated to be 0.6 % and the limit of detection for chloride ion is about 0.04 %. To further enhance its sensitivity for chloride concentrations, we have coated gold nanoparticles on the grating surface of the LPG sensor. The sensing mechanism is based on the sensitivity of localized surface plasmon resonance of self-assembled Au colloids on the grating portion of the LPG. With this method, a factor of two increases in sensitivity of detecting chemical solution concentrations was obtained. The advantage of this type of the sensor is relatively simple of construction and ease of use. Moreover, the sensor has the potential capability for on-site, in vivo, and remote sensing, and has the potential use for disposable sensors.

A fast response hydrogen sensor with Pd metallic grating onto a fiber's end-face

Science.gov (United States)

Yan, Haitao; Zhao, Xiaoyan; Zhang, Chao; Li, Qiu-Ze; Cao, Jingxiao; Han, Dao-Fu; Hao, Hui; Wang, Ming

2016-01-01

We demonstrated an integrated hydrogen sensor with Pd metallic grating fabricated on a fiber end-face. The grating consists of three thin metal layers in stacks, Au, WO3 and Pd. The WO3 is used as a waveguide layer between the Pd and Au layer. The Pd layer is etched by using a focused ion beam (FIB) method, forming a Pd metallic grating with period of 450 nm. The sensor is experimentally exposed to hydrogen gas environment. Changing the concentration from 0% to 4% which is the low explosive limit (LEL), the resonant wavelength measured from the reflection experienced 28.10 nm spectral changes in the visible range. The results demonstrated that the sensor is sensitive for hydrogen detection and it has fast response and low temperature effect.

Novel fiber Bragg grating fabrication system for long gratings with independent apodization and with local phase and wavelength control.

Science.gov (United States)

Chung, K M; Dong, L; Lu, C; Tam, H Y

2011-06-20

We proposed and demonstrated a novel practical fiber Bragg grating (FBG) fabrication setup constructed with high performance linear stages, piezoelectric translation (PZT) stages, and a highly stable continuous wave laser. The FBG fabrication system enables writing of long FBGs by a continuous translate-and-write process and allows implementation of arbitrary chirp and apodization. A key innovation is that the local Bragg wavelength is controlled by a simple movement of the phase mask by a PZT in the direction perpendicular to its surface. The focus position of the two writing beams is not changed during the Bragg wavelength change, an intrinsic feature of the design, ensuring simplicity, robustness and stability. Apodization can be achieved by vibrating the phase mask in the direction parallel to its surface by a PZT. Phase steps can also be inserted in FBGs at any desired locations by stepping the same PZT. A long uniform FBG and a linearly chirped FBG are written to demonstrate the performance of the setup.

A review of spectrally coded multiplexing techniques for fibre grating sensor systems

International Nuclear Information System (INIS)

Childs, Paul; Wong, Allan C L; Yan, Binbin; Li, Mo; Peng, Gang-Ding

2010-01-01

We review recent work and progress on spectrally coded multiplexing (SCM). SCM is a generic multiplexing technique that provides more efficient data usage, additional flexibility and greater channel capability for fibre and fibre grating based sensor systems. We show a few examples of newly developed SCM techniques based on specially designed fibre gratings

BDK-doped core microstructured PMMA optical fiber for effective Bragg grating photo-inscription.

Science.gov (United States)

Hu, Xuehao; Woyessa, Getinet; Kinet, Damien; Janting, Jakob; Nielsen, Kristian; Bang, Ole; Caucheteur, Christophe

2017-06-01

An endlessly single-mode doped microstructured poly(methyl methacrylate) (PMMA) optical fiber is produced for effective fiber Bragg grating (FBG) photo-inscription by means of a 400 nm femtosecond pulsed laser and the phase mask technique. The fiber presents a uniform benzyl dimethyl ketal (BDK) distribution in its core without drastic loss increase. It was produced using the selected center hole doping technique, and the BDK dopant acts as a photoinitiator. In this Letter, we report a rapidly growing process of the grating reflection band. For an 11 mW mean laser power, the FBG reflectivity reaches 83% in only 40 s.

Characterization and optimization of an ultrasonic piezo-optical ring sensor

International Nuclear Information System (INIS)

Frankforter, Erik; Lin, Bin; Giurgiutiu, Victor

2016-01-01

A resonant piezo-optical ring sensor with both piezoelectric and fiber Bragg grating (FBG) sensing elements was assessed for ultrasonic wave detection. The ring sensor is an existing device that has been shown experimentally to exhibit a number of sensing features: omnidirectionality, mode selectivity, and frequency tunability. The present study uses finite element modeling to understand these features as a means to characterize and optimize the sensor. A combined vibration-wave propagation modeling approach was used, where the vibrational modeling provided a basis for understanding sensing features, and the wave propagation modeling provided predictive power for sensor performance. The sensor features corresponded to the fundamental vibrational mode of the sensor, particularly to the base motion of this mode. The vibrational modeling was also used to guide sensor optimization, with an emphasis on the FBG and piezoelectric sensing elements. It was found that sensor symmetry and nodes of extraneous resonance modes could be exploited to provide a single-resonance response. A series of pitch-catch guided wave experiments were performed on a thin aluminum plate to assess the optimized sensor configuration. Tuning curves showed a single-frequency response to a Lamb wave and mechanical filtering away from the dominant frequency; the sensor capability for mechanical amplification of a Lamb wave and mechanical amplification of a pencil-lead-break acoustic emission event were also demonstrated. (paper)

Control of fibre laser mode-locking by narrow-band Bragg gratings

International Nuclear Information System (INIS)

Laegsgaard, J

2008-01-01

The use of narrow-band high-reflectivity fibre Bragg gratings (FBGs) as end mirrors in a fibre laser cavity with passive mode-locking provided by a semiconductor saturable absorber mirror (SESAM) is investigated numerically. The FBG is found to control the energy range of stable mode-locking, which may be shifted far outside the regime of SESAM saturation by a suitable choice of FBG and cavity length. The pulse shape is controlled by the combined effects of FBG dispersion and self-phase modulation in the fibres, and a few ps pulses can be obtained with standard uniform FBGs

Strain sensors for high field pulse magnets

Energy Technology Data Exchange (ETDEWEB)

Martinez, Christian [Los Alamos National Laboratory; Zheng, Yan [Los Alamos National Laboratory; Easton, Daniel [Los Alamos National Laboratory; Farinholt, Kevin M [Los Alamos National Laboratory; Park, Gyuhae [Los Alamos National Laboratory

2009-01-01

In this paper we present an investigation into several strain sensing technologies that are being considered to monitor mechanical deformation within the steel reinforcement shells used in high field pulsed magnets. Such systems generally operate at cryogenic temperatures to mitigate heating issues that are inherent in the coils of nondestructive, high field pulsed magnets. The objective of this preliminary study is to characterize the performance of various strain sensing technologies at liquid nitrogen temperatures (-196 C). Four sensor types are considered in this investigation: fiber Bragg gratings (FBG), resistive foil strain gauges (RFSG), piezoelectric polymers (PVDF), and piezoceramics (PZT). Three operational conditions are considered for each sensor: bond integrity, sensitivity as a function of temperature, and thermal cycling effects. Several experiments were conducted as part of this study, investigating adhesion with various substrate materials (stainless steel, aluminum, and carbon fiber), sensitivity to static (FBG and RFSG) and dynamic (RFSG, PVDF and PZT) load conditions, and sensor diagnostics using PZT sensors. This work has been conducted in collaboration with the National High Magnetic Field Laboratory (NHMFL), and the results of this study will be used to identify the set of sensing technologies that would be best suited for integration within high field pulsed magnets at the NHMFL facility.

High spatial and temporal resolution interrogation of fully distributed chirped fiber Bragg grating sensors

OpenAIRE

Ahmad, Eamonn J.; Wang, Chao; Feng, Dejun; Yan, Zhijun; Zhang, Lin

2017-01-01

A novel interrogation technique for fully distributed linearly chirped fiber Bragg grating (LCFBG) strain sensors with simultaneous high temporal and spatial resolution based on optical time-stretch frequency-domain reflectometry (OTS-FDR) is proposed and experimentally demonstrated. LCFBGs is a promising candidate for fully distributed sensors thanks to its longer grating length and broader reflection bandwidth compared to normal uniform FBGs. In the proposed system, two identical LCFBGs are...

Fiber Bragg gratings-based sensing for real-time needle tracking during MR-guided brachytherapy

Energy Technology Data Exchange (ETDEWEB)

Borot de Battisti, Maxence, E-mail: M.E.P.Borot@umcutrecht.nl; Maenhout, Metha; Lagendijk, Jan J. W.; Vulpen, Marco van; Moerland, Marinus A. [Department of Radiotherapy, University Medical Center Utrecht, Heidelberglaan 100, Utrecht 3584 CX (Netherlands); Denis de Senneville, Baudouin [Imaging Division, University Medical Center Utrecht, Heidelberglaan 100, Utrecht 3584 CX, The Netherlands and IMB, UMR 5251 CNRS/University of Bordeaux, Talence 33400 (France); Hautvast, Gilion; Binnekamp, Dirk [Philips Group Innovation Biomedical Systems, Eindhoven 5656 AE (Netherlands)

2016-10-15

Purpose: The development of MR-guided high dose rate (HDR) brachytherapy is under investigation due to the excellent tumor and organs at risk visualization of MRI. However, MR-based localization of needles (including catheters or tubes) has inherently a low update rate and the required image interpretation can be hampered by signal voids arising from blood vessels or calcifications limiting the precision of the needle guidance and reconstruction. In this paper, a new needle tracking prototype is investigated using fiber Bragg gratings (FBG)-based sensing: this prototype involves a MR-compatible stylet composed of three optic fibers with nine sets of embedded FBG sensors each. This stylet can be inserted into brachytherapy needles and allows a fast measurement of the needle deflection. This study aims to assess the potential of FBG-based sensing for real-time needle (including catheter or tube) tracking during MR-guided intervention. Methods: First, the MR compatibility of FBG-based sensing and its accuracy was evaluated. Different known needle deflections were measured using FBG-based sensing during simultaneous MR-imaging. Then, a needle tracking procedure using FBG-based sensing was proposed. This procedure involved a MR-based calibration of the FBG-based system performed prior to the interventional procedure. The needle tracking system was assessed in an experiment with a moving phantom during MR imaging. The FBG-based system was quantified by comparing the gold-standard shapes, the shape manually segmented on MRI and the FBG-based measurements. Results: The evaluation of the MR compatibility of FBG-based sensing and its accuracy shows that the needle deflection could be measured with an accuracy of 0.27 mm on average. Besides, the FBG-based measurements were comparable to the uncertainty of MR-based measurements estimated at half the voxel size in the MR image. Finally, the mean(standard deviation) Euclidean distance between MR- and FBG-based needle position