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Authors of this article focused on the use of fiber-optic technology for monitoring heart and respiratory rate of the human body. The article describes an innovative method of encapsulating fiber Bragg grating (FBG) into polymer polydimethylsiloxane (PDMS) and comparison of this measuring probe with an FBG sensor glued on the plexiglass pad. The team of authors offers a solution which is basically focused on the monitoring of long-term ill patients with a minimum of physical movement load. Real data were acquired from a group of 10 volunteers with their written consent in the laboratory environment. Acquired data was compared by the Bland-Altman method.

Technology fiber Bragg grating (FBG) belongs to the most widespread fiber optic sensors. It used for measuring a large number of chemical and physical quantities. Immunity to el ectromagnetic interference, small size, high sensitivity and principle information encoding about the measured value to the spectral characteristics cause usability of FBG sensors in medicine for monitoring vital signs such as heart rate, blood pressure, temperature or respiration. An important factor in this area is the use of an inert material for the Bragg gr atings encapsulation. An interesting choice is the elastomer polydimethylsiloxane (PDMS). PDMS is optically clear, general inert, non-toxic and non-flammable. The material commonly used for biomedical and medical applications. Experimental results presented in this paper describe the creation of prototype FBG sensor for the heart rate monitoring of a human body. The sensor is realized by Bragg grating encapsulated into polydimethylsiloxane. The FBG sensor is part of the elastic contact strap which encircles the chest of the patient. This chest expansion leads to a spectral shift of the reflected light from the FB G. The research based on the monitoring of eight different test persons. Heart rate meas urements were compared with a reference signal ECG and analyzed objectively by th e Bland-Altman statistic.

The surface-bonding method of the fiber Bragg grating(FBG) sensor is easier to handle than embedding method. However surface bonded FBG sensors have the limitation of the signal characteristics being affected by the bonding layer. In this study, the effects of the bonding length on the surface installed FBG sensor signal characteristics under various load types were empirically investigated. To evaluate the stability of the signal characteristics of the FBG sensors, the strain transfer rate and the multiple peaks ratio of the reflected spectrum were calculated and compared. From the experimental results, the strain transfer ratio and multiple peaks ratio varied because of the different strain gradients formed depending on the applied load type. Therefore, it was found that the effective bonding length for respective load types need to be determined to get a stable signal from the surface bonded FBG sensors.

We investigate the sensitivity improvement of fiber Bragg grating (FBG) sensors based on the optical attenuation-based weak value amplification (WVA). We successfully enhance the strain sensitivity of the FBG sensor based on the proposed WVA. The amplification factor (A) controlled by the optical attention is optimized to improve the sensitivity of the FBG sensing probe. The strain sensitivity of the FBG sensor using the proposed attenuation-based WVA is successfully enhanced by a factor of 2.73 compared with that without the WVA.

The curing process of epoxy resin was monitored real-time by using embedded fiber Bragg grating (FBG) sensor. The resin was cured at room temperature 24°C for 24 hours. The curing monitor test showed that the temperature inside the resin went up quickly at the first 70 minutes. Then the temperature increased slowly till 120 minutes. Afterward, the central wavelength decreased which indicated two stage of curing, i.e. temperature reduction and curing shrinkage. Furthermore, the cured resin sample under tensile load was studied. Strain gauges were applied in order to evaluate the FBG sensor. Experimental results showed that difference existed between the mentioned sensors.

Applications of composite materials in aerospace structures is increasing due to the outstanding properties, however, monitoring such composite structures exposed to harsh environments is still a posing issue. Low Earth orbit space structures are exposed to property degradation and damage from high-degree vacuum, ultraviolet radiation, thermal cycling, and atomic oxygen attack which are detrimental to composite materials. In this study, FBG sensors for embedding in CFRP composite plates in different thickness locations to provide health and damage monitoring of the material exposed to such environments regarding the overall health of the material with a focus on the exposed surface are explored in comparison to conventional FBG sensors.

To enrich the sensing mechanism of the FBG sensors, the cantilever FBG sensor is taken as an example to analyze the effect of the deflection on the embedded stress distribution and structure parameters of the FBG, and a widely applicable analysis method is thus proposed. Models of the single-core and multi-core FBG sensor are built by the proposed method and a modified transmission matrix method is utilized to simulate the built models. The lateral resolution of the multicore FBG sensor is proved to be 1500 times higher than the single-core FBG sensor. Simulation results of the proposed models indicate that this approach is tally with the experiment of other researches, and it can be used to analyze the performance of the designed sensors, such as spectrum signal and resolution, or as a guide of designing FBG sensors.

Space deployable mechanisms are widely used, important and multi-purpose components in aerospace fields. In order to ensure the mechanism in normal situation after unfolded, detecting the deformation caused by huge temperature difference in real-time is necessary. This paper designed a deployable mechanism setup, completed its distributed deformation measurement by means of fiber Bragg grating (FBG) sensors and BP neural network, proved the mechanism distributed strain takes place sequence and FBG sensor is capable for space deployable mechanisms deformation measuring.

The FBG sensor has globally been commercialized in various fields that is actively applied in Korea as well. Especially it is widely used as a structural monitoring sensor in civil engineering and construction structures due to its advantages including electrical stability, chemical stability and multiplexing. This report aims to introduce safety inspection of the FBG sensor in respect of radioactivity which has been applied to a silo structure for radioactive waste disposal as an example.

The large span and heterogeneous components of multi-layered pavement structure usually bring about stochastic damage, and many modern approaches, such as ground penetrating radar, integral imaging and optical fiber sensing technology, have been employed to detect the degeneration mechanism. Restricted by the cost and universality, novel elements for pavement monitoring are in high demand. Optical fiber sensing technology for high sensitivity, long stability, anti-corrosion and resistance to water erosion then is considered. Therefore, a movable FBG sensor located in flexible pipe is developed, which has long stroke inside inner wall of the hollow pipe, and a full-scale shape of the structure could be sketched just with one FBG. Theoretical and experimental methods about establishing the relationship between wavelength variable and curvature have been provided, and function about reconfiguring the coordinate is converted to a mathematic question. Move over, transfer error modification has been taken into account for modify related error. Multi-layered pavement model embedded with this sensor will be accomplished to inspect its performance in later work. The work in the paper affords a feasible method for shape monitoring and would be potentially valuable for the maintenance and inverse design of pavement structure.

A novel real-time monitoring system based on Fiber Bragg Grating (FBG) sensor has been developed to detect chatter in boring process. In the system, a boring bar with large length-to-diameter ratio (FSTUP3225R/L-16S) was the test subject. The FBG sensor was installed on the surface of the boring bar with the length of 225mm. A classical strain gauge was employed to measure the vibratory strain and compare the results with the ones from FBG sensor. The measurements were carried out using various cutting parameters to obtain the desired chatter phenomenon. The analysis of the experimental data was verified the chatter happened during the deep hole boring. Comparison between the experimental results from two kinds of sensors demonstrated that the measurement technique could be used to detect the dynamic strain, as well as the permitting one to research the method to identify boring chatter on-line be using optical fiber sensor system.

We present a solid-state FBG array interrogator and multiplexer capable of determining absolute FBG wavelengths and of providing high-speed, high-resolution static and dynamic measurements. Using a described procedure, deployable on multiplexing passive-interferometric schemes, the system is able to determine initial sensor wavelengths and thereafter track wavelength changes with interferometric resolution. The scheme allows high-resolution interrogation of FBG sensor arrays to be applied to many industrial applications, where previously the lack of combined absolute and quasi-static wavelength measurement precluded the use of interferometric techniques. Using a preliminary laboratory embodiment, we demonstrate a wavelength determination accuracy of

It is the aim of this paper to present the design of a sensor system based on fiber Bragg gratings (FBG) for the strain monitoring of an adaptive trailing edge (ATE) device. Some of the activities herein showed comes from developments inside the project SARISTU (EU-FP7), funded by the European Union inside the VII Framework Programme and focused on smart aircraft structures. Because the TE is immerged into 3D structural and aerodynamic fields, the sensor system network should have chord- and span-wise features. The ATE device will be equipped with a shape monitoring system using a widely distributed sensors based on fiber optic (FO) elements herein referred to, mainly with the aim of reducing the number of channels (then expense, complexity, etc.). In what follows, the mathematical modelling of a sensor system concept based on FBG is applied to evaluate the chord-wise strain of a trailing edge device. A hinge rotation detection capabilities based on strain measurements is presented. The detection and process of data concerning the in-flight ATE local deformation are necessary to reconstruct the shape produced by the action of a dedicated actuation system.

The proposed desensitized encapsulation structure solved the problem that more than 5500μe test range for FBG sensor. The single steel wire with proposed FBG sensor tension test in laboratory before and after fatigue experiment showed the rationality and reliability of sensor structure. A scheme using desensitized encapsulation FBG sensor to fabricate smart cable which was compatible with production process of parallel steel wires cable was designed. The specimen cable tension test verified sensors high survival rate of the design scheme and good long-term precision after fatigue experiment. Also the actual application of smart cable was tested by one bridge during the construction and operation stage.

The strain sensitivity of FBG-based strain sensors that had been inscribed into three different types of optical fibers were determined for both conditions, for fibers that were glued on a specimen and for free, bare fibers, i. e. fibers that were not bonded to a structure at the location of the FBG. The influence of the gluing technique on the strain sensitivities of the FBG sensor elements was investigated by comparing the strain sensitivities of a multitude of attached and free sensor elements on a statistical basis. A good agreement between the strain sensitivities of free and attached fibers was achieved, which shows the high quality of the gluing method employed.

Corrosion of steel in structures has become a major cause of structural degradations. Corrosion detection and monitoring are necessary for evaluation of structural service conditions. A novel FBG based sensor for steel corrosion detection and monitoring is developed previously. In this paper the sensor performances are evaluated by comparing to the corrosive rate of rebars in the corrosive environments. The correlation between the wavelength shifts of the sensor and the corrosive depth is established. It is proved that the sensor responses successfully to the occurrence of rebar corrosion, which shows the promising feasibility of applying the sensor for corrosion indicator.

In this paper, we report our recent work in an application of fiber Bragg grating (FBG) sensors in progressive failure monitoring of E-glass/vinylester top-hat stiffener (THS) composites. FBG sensor arrays were embedded at strategic points within the THS to monitor the onset and progress of failure modes as the THS undergone a transverse loading. Techniques to embed FBGs in-situ during composite structure fabrication are developed. Our experiments demonstrated that key structural failure information can be obtained from the analysis and assessment of data, such as average strain, strain gradient and full spectrum measurements, collected by the embedded FBG sensors.

We suggest a spectrometer demodulation method of FBG sensors for the possible uses in wind power generator's blade monitoring. High signal-to-noise ratio outputs and linear demodulation were obtained by combining a fiber laser light source and a spectrometer which used a holographic volume grating and a 512-pixel PD array. Preliminary experimental results are presented to show the feasibility of the suggested FBG demodulation system.

The importance of real-time detection of cable force during stretching construction can hardly be overstated, especially in long-span space cable system. In this paper, a novel approach to monitor the cable structure health using fiber Bragg grating (FBG) sensors was elaborated and applied in monitoring the tensioning process of suspend-cable dome of Dalian Gymnasium under construction. The encapsulated FBG strain sensors were adhered to the anchor to detect the cable force. Calibration tests conducted prior to leaving factory in order to get the cable force sensitivity coefficient were also presented. The monitoring results of stage stretching construction prove that this cable force monitoring method based on FBG sensors has advantages of easy installation, non-destruction to structure and high precision, showing promising potential in cable structure health monitoring.

In the past few years, fiber Bragg grating (FBG) sensors have attracted a lot of interest and there were number of studies on the use of FBG sensors to detect the strain of steelworks. This paper describes the strain sensors based on FBG with different package used for steelwork. Strain distribution of the steelwork is predicted through Finite element analysis. Bare FBG, FBG sensor packaged with steel sheet and resistance strain gauges are set on the same specified location of steel specimen, and load is added on the steelwork by rally machine. Strain values of the steel specimen can be caught by three kinds of sensors when load is stabilized. Then the load added on the steelwork is changed from 0KN to 50KN and back to 0KN, meanwhile the values of strain are recorded respectively. Results of three sensors are compared mutually and are all close to theoretical values provided by FEA.

Many established and recently-introduced optical biosensor concepts rely on the detection of a small wavelength change in response to change of temperature, adhesion of bio-particles, strain, or chemical environment. Special coatings are used to sensitize them to specifically bound molecules (e.g., biomarkers). We describe a compact and fast wavelength monitor that can resolve sub-pm wavelength changes. The unit was demonstrated by reading out a FBG sensor and can resolve wavelength changes as small as 50fm with a bandwidth of more than 100Hz.

Being an important bridge engineering structural strengthening manner, external prestressing method usually makes steel strand which is one of the most widely used member in external cable bear large strain in construction and operating stage. By means of directly testing structural strain to monitor the mechanical condition and prestressing loss of steel strand is a great challenge for civil engineers. In order to exert the advantages of FBG sensing technology, study FBGbased bridge external prestressing test method, achieve the FBG-based prestressing loss monitoring, in this paper, the difficulties that use FBG to test structural large strain were analyzed and a FBG-based monitoring strategy was elicited. In order to verify the proposed method, a real bridge strengthening engineering paradigm was given. The monitoring results showed that the proposed strategy not only met the requirement for structural large strain testing during the whole construction process, but also the intact FBG sensor still played a role in the subsequent prestressing loss monitoring.

An extensive model test program had been carried out to investigate the issues of ice loading on bridge pier model. This paper investigated design principle of three kinds of FBG sensor modules, including FBG-based displacement sensor module, FBG-based strain sensor module and FBG-based force sensor module. A series of calibration tests of all FBG sensors had been made to detect the sensitivity of FBG sensor modules previously. There were 12 FBG-based sensors applied to monitor the failure progress and to predict the cracking inside the bridge pier model. The results of the ice loading tests proved that the FBG-based sensor had many advantages, characterized by its small size, high precision, easier installation, water resistance and cold resistance, demonstrating promising potentials in cracking and failure monitoring of bridge pier model.

A human physiological parameters intelligent clothing is researched with FBG sensor technology. In this paper, the principles and methods of measuring human physiological parameters including body temperature and heart rate in intelligent clothing with distributed FBG are studied, the mathematical models of human physiological parameters measurement are built; the processing method of body temperature and heart rate detection signals is presented; human physiological parameters detection module is designed, the interference signals are filtered out, and the measurement accuracy is improved; the integration of the intelligent clothing is given. The intelligent clothing can implement real-time measurement, processing, storage and output of body temperature and heart rate. It has accurate measurement, portability, low cost, real-time monitoring, and other advantages. The intelligent clothing can realize the non-contact monitoring between doctors and patients, timely find the diseases such as cancer and infectious diseases, and make patients get timely treatment. It has great significance and value for ensuring the health of the elders and the children with language dysfunction.

Fibre Bragg gratings are promising sensors for medical and bioengineering applications, mainly because of their small dimensions and chemical inertness. Although few examples of such applications are published up to date, we present results that show the expected potential for FBG sensor applications in biomechanical engineering.

In this paper, a novel 3D strain FBG sensor based on cylinder structure is reported. In our experiment, we used 3 FBGs as sensing element and fixed them on the side of the cylinder according to 120° angle intervals. Based on the physical and mathematics principle, theoretical derivations and experiment setup were also showed. In application, this sensor would have a good prospect.

A FBG-based dynamic strain sensor system, whose responding frequency and resolution can be high as 16Hz and ~1μe 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.

There is a growing demand for lightweight structures in aircraft systems for energy and cost savings. The authors have therefore continued development of the Highly Reliable Advanced Grid Structure (HRAGS) with the aim of application of the same to aircraft. HRAGS is provided with health monitoring functions that make use of Fiber Bragg Grating (FBG) sensors in advanced grid structures, which have been the focus of attention in recent years as lightweight structures. It is a new lightweight structural concept that enables lighter weight to be obtained while maintaining high reliability. This report describes the tests and evaluation of the Proto System conducted to verify experimentally the concept of the highly reliable advanced grid structure. The Proto System consists of a skin panel embedded with 29 FBG sensors and a wavelength detection system. The artificial damage to the skin panel of the specimen was successfully detected by comparing the strain distributions before and after the introduction of the damage measured by FBG sensors. Next, the application of HRAGS to the wing tip was studied. The results of the studies above are reported here.

It is a great challenge to prevent cracks occurring due to the temperature deviation of inside and exterior of large mass concrete structures during construction. 237 FRP (Fiber Reinforced Polymer)-packaged FBG (Fiber Bragg Grating) temperature and strain sensors have been used to monitor the temperature and strain course of mass concrete structures for construction control of Nanjing 3rd Yangtze Bridge. The practical investigation results show that the FRP-packaged FBG sensors are proper for construction control of mass concrete structures, which show great advantages rather than conventional sensors.

Due to their variability Fibre Bragg Grating (FBG) sensors are introduced in a growing number of applications. Furthermore using their spectral selectivity and adjustable reflectivity these sensors are predestined for serial networking, whereby presently in most cases the addressing is realised by time division multiple access (TDMA) or wavelength division multiple access (WDMA). But these technologies have big disadvantages regarding the effective use of the prevailing resources time and wavelength, respectively. In this paper a new scheme capable of addressing a large number of FBGs in a single serial network is proposed and compared to TDMA and WDMA. Using all optical sequence inversion keyed (SIK) direct sequence (DS) code division multiple access (CDMA) it overcomes the restrictions handling the resources time and wavelength without loosing accuracy. A simulation with 20 FBGs in a spectral range of 2nm shows the abilities of this system, which can be build up with nearly the same components as TDMA systems.

Fiber Bragg grating (FBG) sensor systems have been widely developed and the feasibility of their application to various fields has been demonstrated. However, from the viewpoint of the combination of highly multiplexed system and hybrid sensing of static parameter and dynamic parameter, investigations are not adequate yet. In this paper an interrogation technique for static and dynamic FBG sensors is developed. We demonstrated that the method could measure the temperature within 1°C and detect a frequency signal up to 300Hz. We designed a multiplexing method and evaluated that the multiplexed FBG sensor system was able to monitor a maximum of 192 FBG sensors. As a result, we confirmed the applicability of the system for large-scale monitoring of temperature, strain and vibration.

A series of FBG sensor modules for the building structure are developed. And the health monitoring system using FBG-based sensor modules were installed. Which was used for the 12th floor steel frame building of the damage tolerant built. There are 64 FBG-based sensors in the building structure. A detailed experiment was done about the FBG-based displacement sensor module, the FBG-based strain sensor module, and the FBG-based temperature modules.

Two homemade FBG (Fiber Brag Grating) sensors were installed on specific locations of a small-scale three-story structure model. The model was excited by various kinds of vibrations and the dynamic strain data were measured. In order to make a full comparison, the traditional RSG sensors were also installed on the same location of the FBG sensors. The accelerometers and LVDTias were also used to offer detailed dynamic information about the structure. Analysis on the test results showed good agreements between the FBG and the RSG sensors and the advantages of using FBG sensors. The fundamental frequency of the structure was also obtained from analyzing the measured data. The result shows that the FBG sensors can be a good alternative for the RSG sensors in monitoring the structure behavior. In addition, experimental study of plates with cracks was carried out using the FBG sensors. Four homemade FBG (Fiber Brag Grating) sensors were installed on specific locations of an aluminum plate. Four traditional RSG sensors were also installed on the same location of the FBG sensors. Test results shows that the FBG sensors can be used to locate the position of cracks. This study shows that the FBG sensors are very good candidates in structural health monitoring and could be widely used in the near future.

In this paper we studied the potential of using FBG strain sensors to measure the torsion deformation theoretically and experimentally. FBG strain sensors are bonded on the surface of a shaft. When the shaft under torsion there is strain induced in the FBG sensor and the Bragg wavelength will shift accordingly. According to the wavelength shift and photoelastic properties of the FBG sensor bonded on the shaft the torsion deformation of the shaft can be obtained. In order to minimize the measurement error the optimal direction of the FBG sensor was obtained. The influence of the orientation deviation of the FBG sensor was discussed in detail. The feasibility of this method is demonstrated by experiment and the test results agree with the theoretical analysis very well.

In-fiber Bragg grating (FBG) sensor technology has become one of the most progressing sensing topics of this decade in the field of optical fiber sensor technologies as FBG sensors are capable of measuring a wide range of parameters and have potential for simultaneous measurement of multi- parameters. In recent years, rapid progress has been made, in particular, in sensor system developments and applications. The fundamental aspects of the FBG sensor technology have been reviewed recently by the author. As a complementary article, this review paper concentrates on the recent progress in applications of FBG sensors for large composite structures, electrical power industry and medicine. Also, recent progress in sensor system developments associated with these applications are addressed.

Significant progress has been made in recent years in multiplexing techniques for in-fiber Bragg grating (FBG) sensors. This paper is intended to give a systematic overview of recent progress in the multiplexing techniques, including wavelength-division-multiplexing, spatial- division-multiplexing, time-division-multiplexing, and their combinations. There is no doubt that these multiplexing techniques will play an important role in the FBG sensor technology as they make FBG sensor systems cost-effective for quasi-distributed measurement.