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The importance of humidity control is spreading through a broad spectrum of applications, from food and pharmaceutical industries to biomedical and chemical fields. During the last decades, the growing interest in fiber Bragg gratings (FBG) led to new approaches and applications for the humidity measurement by means of the deposition of hygroscopic materials on gratings. The influence of the coating material and its features such us coating thickness (tk) and concentration (wt%) on static and dynamic metrological properties have been investigated in this paper. In this paper, four agar-coated FBG sensors for humidity measurements have been fabricated, and the influence of tk and wt% on the sensors’ sensitivity and response time has been experimentally assessed. Sensitivity increases with tk and wt%: for instance, at 1 wt% it was $0.0024\,\,\text {nm}\cdot {\%}^{\mathrm {-1}}$ and $0.0052\,\,\text {nm}\cdot {\%}^{\mathrm {-1}}$ for $\text {tk}=87\,\,\mu \text{m}$ and $\text {tk} = 212\,\,\mu \text{m}$ , respectively. Results showed that also the response time increased with tk and wt%: for instance, at 1 wt% it was 56.7 s and 107.6 s for $\text {tk} = 87\,\,\mu \text{m}$ and $\text {tk}=212\,\,\mu \text{m}$ , respectively.

The present in vitro study proposes a novel (to the best of our knowledge) methodology employing a fiber Bragg grating sensor for the evaluation of pulp chamber temperature increase during the polymerization of the composite resin induced by the light-curing process. A fiber Bragg grating temperature sensor (FBGTS) has been developed in view of its ease of insertion into the pulp chamber with minimal widening of the pulpal canal. The temperature increase in the pulpal chamber during the polymerization of the composite resin by light curing has been characterized with varying depths of cavities of 1 mm, 1.5 mm, and 2 mm employing FBGTS. Also, the increase in temperature of the pulpal chamber during the polymerization of the composite resin has been studied with variants of the light-curing device. The obtained results are expected to be an indicator towards the potential hazard caused by heat induced pulpal injuries during the polymerization of composite resins using a light-curing device.

Recently, it has become necessary to develop a monitoring technology that combines an FBG (fiber Bragg grating) sensor as a means for continuously monitoring whether the reinforcing effect of an FRP (fiber-reinforced polymer) is maintained on FRP-reinforced structural members. However, most existing research focuses on the insertion of FBG sensors into bar-shaped FRPs, and there is a lack of studies that analyze the details for an FRP strip combined with FBG sensors. In this regard, this paper seeks to develop a reinforcement for an NSM (near-surface-mounted) retrofit in which an optical fiber with an FBG sensor is combined with FRP strips. For this, a series of experiments were performed to find the adhesive strength of optical fiber-epoxy-FRP interfaces, the tensile strength of the FBG sensor part of optical fiber with a reflection lattice, and the sensing performance depending on the adhesion length between the optical fiber and the FRP strips. As a result of the study, the adhesion length not less than 20 mm in one direction from the center, with a total adhesion length of 40 mm, needs to be secured when the optical fiber with an FBG is attached and fixed between the two FRP strips with epoxy. In addition, it is expected that the proposed model can be used to properly predict the strain transfer of an FRP strip with a fiber optic sensor and can also be utilized when determining optimum dimensions.

A method for the continuous detection of heart rate (HR) in signals acquired from patients using a sensor mat comprising a nine-element array of fiber Bragg gratings during routine magnetic resonance imaging (MRI) procedures is proposed. The method is based on a deep learning neural network model, which learned from signals acquired from 153 MRI patients. In addition, signals from 343 MRI patients were used for result verification. The proposed method provides automatic continuous extraction of HR with the root mean square error of 2.67 bpm, and the limits of agreement were -4.98–5.45 bpm relative to the reference HR.

Wavelength variation of fiber Bragg grating sensor is caused by strain and temperature. We propose a method to discriminate between these two parameters by measuring full width half maxima at different strain and temperature values.

Epidural anesthesia is a clinical practice described as an injection of anesthetic into an epidural space using a special catheter. It is a very popular treatment for pain relief, but due to the blindness of the procedure existing techniques frequently fail in identifying the epidural space. One of the proposed solutions is to use Fiber Bragg Grating (FBG) sensors to measure the strain experienced by the needle during injection. Since different tissues have different properties, the strain acting on the needle will vary when it passes from one tissue to another. an array of five FBG sensors, mounted on the external side of the catheter, records the local strain and discriminates forces and bending on the catheter, serving as a guidance method. Experiments have been performed on a phantom.

Clinical scenarios could be characterized by several adverse conditions. For this reason, it is important to ensure a safety interaction between medical equipment and patients. In this context, optical fiber-based technologies are becoming very popular because they are considered intrinsically safe and immune to electromagnetic interferences. Among them, Fiber Bragg Grating (FBG) sensors are gaining in importance for the monitoring of physiological parameters like breathing rate (BR), heart rate, and body temperature. Moreover, among many procedures, polymer functionalization of the fiber optic allows making FBG sensitive to chemical parameters, including: relative humidity (RH), pH, gas, and biomolecules. In this study, we investigated the possibility of using a FBG-based needle for monitoring both RH and BR during mechanical ventilation. Regarding RH estimation, we performed a qualitative analysis to assess if the probe is able to follow RH changes, during mechanical ventilation. The proposed systems experienced a Bragg wavelength shift of ~0.38 nm for RH changes from ~20% to ~90% and vice versa. The performance of the needle for BR estimation was investigated at different minute volumes (MV) and BR set by using the ventilator, covering the values used in the adult ventilation. The BR values estimated by the system were compared to the ones provided by the mechanical ventilator, and used as reference. The absolute value of the percentage errors $(\varepsilon _{\mathrm {e}\mathrm {r}\mathrm {r}}\%)$ was always lower than 3.7% (in the 90% of cases it was

Continuous respiratory monitoring is important to assess adequate ventilation. We present a fiber optic-based smart textile for respiratory monitoring able to work during Magnetic Resonance (MR) examinations. The system is based on the conversion of chest wall movements into strain of two fiber Bragg grating (FBG) sensors, placed on the upper thorax (UT). FBGs are glued on the textile by an adhesive silicon rubber. To increase the system sensitivity, the FBGs positioning was led by preliminary experiments performed using an optoelectronic system: FBGs placed on the chest surface experienced the largest strain during breathing. System performances, in terms of respiratory period (TR), duration of inspiratory (TI) and expiratory (TE) phases, as well as left and right UT volumes, were assessed on four healthy volunteers. The comparison of results obtained by the proposed system and an optoelectronic plethysmography highlights the high accuracy in the estimation of TR, TI, and TE: Bland-Altman analysis shows mean of difference values lower than 0.045 s, 0.33 s, and 0.35 s for TR, TI, and TE, respectively. The mean difference of UT volumes between the two systems is about 8.3%. The promising results foster further development of the system to allow routine use during MR examinations.Continuous respiratory monitoring is important to assess adequate ventilation. We present a fiber optic-based smart textile for respiratory monitoring able to work during Magnetic Resonance (MR) examinations. The system is based on the conversion of chest wall movements into strain of two fiber Bragg grating (FBG) sensors, placed on the upper thorax (UT). FBGs are glued on the textile by an adhesive silicon rubber. To increase the system sensitivity, the FBGs positioning was led by preliminary experiments performed using an optoelectronic system: FBGs placed on the chest surface experienced the largest strain during breathing. System performances, in terms of respiratory period (TR), duration of inspiratory (TI) and expiratory (TE) phases, as well as left and right UT volumes, were assessed on four healthy volunteers. The comparison of results obtained by the proposed system and an optoelectronic plethysmography highlights the high accuracy in the estimation of TR, TI, and TE: Bland-Altman analysis shows mean of difference values lower than 0.045 s, 0.33 s, and 0.35 s for TR, TI, and TE, respectively. The mean difference of UT volumes between the two systems is about 8.3%. The promising results foster further development of the system to allow routine use during MR examinations.

In this work, Pd/Pt material based fiber Bragg grating (FBG) sensors has been proposed for detection of hydrogen sulfide gas. Here, characteristics of FBG parameters were numerically calculated and simulated. The variation in reflectivity based on refractive index has been shown. The reflectivity of FBG can be varied when refractive index is changed. The proposed sensor works on very low concentration i.e., 0% to 1%, which has the capability to detect in the early stage.

An ultra-low crosstalk and polarization independent interferometric FBG sensor array were demonstrated utilizing novel crosstalk synthesis and polarization switching (CIS-PS) hybrid processing method. The measured crosstalk reached −50dB, making it attractive for acoustic and seismic sensing applications.

Outdoor optical fiber cabinets are generally installed along roadsides where environmental conditions, such as sun exposure, rain, and dust, can cause damage to the cabinets. Furthermore, high temperatures and unexpected impacts that cause cabinet deformation may damage the network equipment inside the cabinets, affecting the quality of communications. This paper developed an optical fiber sensing system for real-time monitoring of the temperature variation and external forces exerted on outdoor cabinets using fiber Bragg gratings (FBGs). This FBG sensing system was established in the network management center, and was linked to the outdoor cabinets at the remote end through optical fibers in order to monitor the impacts and temperature changes of the cabinets. Experimental results revealed that exerting an external impact force of 297 N on an outdoor cabinet severely dented the impacted cabinet surface. When the monitoring system detects external impacts exceeding 297 N or cabinet temperatures greater than 65 °C, the network management center can then immediately send maintenance personnel to check for any network impairments.

In this paper, we have demonstrated that the spectral bandwidth of a FBG can be modulated by embedding a single Fiber Bragg grating (FBG) sensor in a composite laminate. The bandwidth modulation was achieved by exploiting the birefringence of the embedded – FBG sensor, which was sensitive to the transverse strain and thus varies with temperature or axial load. Combining the bandwidth changes with the Bragg wavelength shift may enable measuring the simultaneous changes in temperature and axial strain using a single FBG sensor.

The demand on high-speed weigh-in-motion (WIM) measurement rises significantly in last decade to collect weight information for traffic managements especially after the introduction of weigh-station bypass programs such as Pre-Pass. In this study, a three-dimension glass fiber-reinforced polymer packaged fiber Bragg grating sensor (3D GFRP-FBG) is introduced to be embedded inside flexible pavements for weigh-in-motion (WIM) measurement at high speed. Sensitivity study showed that the developed sensor is very sensitive to the passing weights at high speed. Field tests also validated that the developed sensor was able to detect weights at a vehicle driving speed up to 55mph, which can be applied for WIM measurements at high speed.

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

A novel scheme for a code-division multiplexing based fiber Bragg grating sensor system is theoretically analyzed and experimentally demonstrated. The results show that the proposed scheme enables an improved signal-to-noise ratio performance compared with the time-division multiplexing method and that spontaneous–spontaneous beating noise should be included in the analysis to avoid overestimation. The simple and effective setup provides a competitive approach for using fiber Bragg grating sensors in practical application systems.

A new evaluation method of the bridge strengthening effect is proposed based on the fiber optic sensor. The monitor layout scheme of bridge is designed to monitor the bridge strengthening effect accurately by measuring dynamic load moment and transverse vibration of the railroad bridge using the fiber Bragg grating sensor. At first, the paper presents the evaluation principle of the bridge strengthening. And then the fiber sensors are set up on the railroad bridge for extracting data of the health status from these sensors. The effect of the strengthening could be shown from the data change after bridge strengthening applied. The researches provide the scheme of the bridge strengthening quality evaluation, which is the base for the control of construction quality for new bridge strengthening technology.

During mechanical ventilation, specific devices are used to heat and to humidify gases delivered by mechanical ventilators. Basically, they must replace the function of the upper airways that are bypassed by tracheostomy or endotracheal tubes. Among others heated wire humidifiers (HWHs) are the most popular to accomplish this task. Their control is not based on the measure of relative humidity (RH) but on the gas temperature in a single point of the breathing circuit. Owing to the mentioned control, HWHs' performance shows some weaknesses in particular when they work under demanding ventilatory settings. Moreover, also environmental conditions (e.g., temperature) can affect HWHs' performance. The direct control of the air humidity may be beneficial to overcome these hurdles. The aim of this work is to develop a fiber optic sensors, based on fiber Bragg grating (FBG) technology for RH measurements in mechanical ventilation. It consists of a coated FBG, whose output changes with RH due to the volume expansion of the coating material. The proposed sensor has been fabricated with a simple coating procedure and it is coated with a cost effective polymer (i.e., agarose), which can be used in a wide range of RH values. An experimental set-up allowing the delivering of air with different amounts of vapour content (relative humidity from about 0% to saturation) has been prepared to perform a preliminary assessment of the sensor in a wide range of RH values. The proposed sensor shows promising results in terms of both capability to follow RH changes, as well as sensitivity and range of measurement. Future testing will assess in depth the metrological properties of the proposed sensor and will evaluate the potential of the sensor for RH monitoring during mechanical ventilation. The implementation of a feedback based on RH may be useful both to improve the performance of HWHs, to minimize the influence of external factors on the humidification process, as well as to pave the way to new strategy of control in this field. © 2017 IEEE.

Nuclear containment building is used as second blockage to protect us from a radiation leakage caused by the natural disaster or anyaccidents, so it's safety is important and must be kept with continuous surveillance. In this study, we measured the strain of a nuclearcontainment building's wall by using FBG sensor and investigated the structural safety of a nuclear containment building. 50 FBG strainsensors and 18 FBG strain sensors were attached on the side wall and upper dome of a nuclear containment building, respectively. Wemeasured the strains of the outside concrete wall during the Structural Integrity Test (SIT) of a nuclear containment building. The strain ofan upper dome was larger than that of a side wall, about 200 u o. And the very small strain was measured at vertical direction of a sidewall. These experimental results were used to evaluate the structural health of nuclear containment building. Keywords : Fiber Bragg grating, Nuclear containment building, SIT, Fiber optic sensor

This paper presents a damage detection and imaging approach using guided waves and through the use of optical fiber Bragg Grating (FBG) sensors for structural health monitoring (SHM) purpose. An FBG array composed with four linearly aligned FBG sensors for guided wave sensing is designed. It is found that FBG sensors are optimized for sensing guided wave coming along the axial direction yet minimized for those along the normal direction. To overcome this limitation and allow for all directional sensing, a FBG phased array beamforming algorithm is derived based on the commonly used delay-and-sum beamforming algorithm principle. The work continues to evaluate the detection capability of the FBG array through two experimental studies on an aluminum plate: (a) guided wave source localization; (b) surface damage detection. The results indicates that both targets are successfully detected and agree well with their actual locations and thus confirms the capability of using presented FBG phased array for rapidly inspecting a large area with limited access.

Hyperthermal techniques are spreading as an alternative to conventional surgery for cancer removal. A real-time temperature feedback can be used to adjust the treatment settings, in order to improve the clinical outcomes. In this paper, we experimentally assessed the feasibility for distributed temperature monitoring of a custom probe, which consists of a needle embedding six fiber Bragg gratings (FBGs). Since FBGs are also sensitive to strain, we focused on the analysis of the measurement error (artifact) caused by respiratory movements. We assessed the artifact both on ex vivo pig liver and lung (by mimicking the movement of these organs caused by respiration) and on in vivo trial on pig liver. Lastly, we proposed an algorithm to detect and minimize the artifact during ex vivo liver laser ablation. During both ex vivo and in vivo trials, the probe insertion within the organ was easy and safe. The artifact was significant (up to 3 °C), but the correction algorithm allows minimizing the error. The main advantages of the proposed probe are: 1) spatially resolved temperature monitoring (in six points of the tissue by inserting a single needle) and 2) the needle is magnetic resonance (MR)-compatible, hence can be used during MR-guided procedure. Even if the model is close to humans, further trials are required to investigate the feasibility of the probe for clinical applications. © 2001-2012 IEEE.

Comfortable and easy to wear systems are gaining popularity for monitoring physiological parameters. Among others, smart textiles based on fiber optic sensors have shown promising results for respiratory monitoring and applications in magnetic resonance (MR) environment. The aim of the present study was to design, fabricate and assess on healthy volunteers a smart textile based on fiber Bragg grating (FBG) sensors for respiratory monitoring. The new design was driven by the chest wall kinematics analysis performed by a marked-based motion capture system. The proposed textile shows promising performances for the non-intrusive monitoring of both compartmental and global volumetric parameters over time. Moreover, the use of FBGs makes the system MR-compatible. This feature was tested on two volunteers. The system did neither cause any image artifacts nor discomfort to the volunteers. This promising results encourage future developments to investigate the feasibility of the proposed smart textile for long-term observation of respiratory parameters, for patients monitoring during MR scan, and during sport activities in athletes. © 2016 IEEE.

The first publication on the sensing potential for side-written Bragg gratings in optical fiber appeared as a patent PCT publication by the Meltz et al. group from UTC in 1986. In the 30 years that have followed, we have seen an extraordinary series of developments in fiber Bragg grating (FBG) sensor technology, taking it from early conceptual laboratory demonstrations to powerful commercial distributed sensing platforms, with many companies now developing and marketing FBG systems and ‘interrogator’ units. This paper will review this history, highlight some of the key developments in the sensing capabilities developed and touch on some truly novel applications of the technology. The paper will also review more recent applications based on the use of extremely weak draw-tower written grating arrays that exploit the unique properties of Bragg gratings in ways to enable creative & differentiated sensing capabilities.

The present study investigates the influence of uniform FBG length on temperature measurement under substantial temperature gradient. This analysis is particularly relevant in the scenario of laser ablation (LA), where the temperature gradient close to the optical applicator is significant (e.g., up to 50 °C/mm). Aiming to assess how the sensor length affects the measurement process in LA, both bench and ex vivo experiments were carried out by applying temperature gradient in the range 5 °C/cm-30 °C/cm on 1 mm-length FBG and 10 mm-length FBG. Results showed that the use of small-sized FBGs is recommended in LA for two main reasons: i) the spectrum reflected by shorter sensors has not shown significant alterations with the gradient. Alterations of the spectrum shape could compromise peak detection algorithms, and, therefore, the estimation of the actual temperature; ii) Arrays of shorter sensors can provide multipoint temperature measurements, with quiet good spatial resolution (e.g., 3 mm), by inserting a single fiber in the tissue. © 2016 IEEE.

Technology such as Fiber Bragg Grating (FBG) sensors are widely accepted in almost all industries. FBG are being investigated for their applicability in other markets such as smart structures. Fiber optic sensors can also be used in many different applications. Fiber optic sensors are available in several types; among them, the Bragg grating sensor is being studied in this research. For this research work, the main focus was the use of fiber Bragg grating sensors for measuring strain. The key objective of this research; to determine the functionality of fiber Bragg grating sensors compared to that of conventional foil gauges. Fiber Bragg grating sensors were chosen for this research because they have a high potential for various uses in the monitoring of smart structures. The major incentives for this type of research are the current deterioration of civil structures in west Malaysia. The laboratory tests are being reported in this research work including tests of steel straps and an aluminum test specimen. In all the tests, strain was measured using the fiber Bragg grating sensors and compared to values from a conventional foil gauge. The results are being discussed in details. It was inferred that the use of fiber optic technology for the monitoring of civil structures is very promising and the future is sure to bring further advancements and improvements.

The use of a fiber Bragg grating (FBG) sensor array for the measurement of dynamic combined stress of ship thruster inner-skin is presented. The triaxial stress is detected using improved three-element rectangular rosette consisting of FBG sensors. Phase lag effect among triaxial stress sensor is considered and eliminated by employing multi-channel demodulation and improving the layout of sensor rosette array and connection layout. The tests are carried on to measure the distributed combined-stress change of ship thruster duct when ship thruster work at different rotate speed and pitch of angle. The test result are analyzed which show that measured stress are acceptable and in accord with predicted result.

For the benefit of electrical isolation, corrosion resistance and quasi-distributed detecting, Fiber Bragg Grating Sensor has been studied for high-speed railway application progressively. Existing Axle counter system based on fiber Bragg grating sensor isn’t appropriate for high-speed railway for the shortcoming of emplacement of fiber Bragg grating sensor, low Sampling rate and un-optimized algorithm for peak searching. We propose a new design for the Axle counter of high-speed railway based on high-speed fiber Bragg grating demodulating system. We also optimized algorithm for peak searching by synthesizing the three sensor data, bringing forward the time axle, Gaussian fitting and Finite Element Analysis. The feasibility was verified by field experiment.

Fiber Bragg grating (FBG) is demonstrated to measure displacement, which relies on attaching the FBG on a cantilever structure, so that the vertical displacement of the cantilever's free end can be obtained by measuring the wavelength shift of FBG. A novel technique is then presented to measure displacement and temperature simultaneously with a single FBG. The measured displacement and temperature sensitivities of this cantilever-based FBG sensor are 8.22×10 −4 mm −1 and 8.86×10−5 (°C−1), respectively. And the measurement range can be up to 10.5 mm.

We propose a newly designed fiber Bragg grating (FBG) sensor with protective armored cable. The packaged FBG array is bonded on a specially designed arc-shape structure mounted on a wall for intrusion detection for the first time.

Based on the advantages of the fiber Bragg grating sensing technology, this paper presents a principle of a novel smart concrete with fiber optical Bragg grating sensor, analyses the theory and characteristics, illustrates the key technology and method to make the fiber Bragg grating sensor for the smart concrete, and proves the feasibility with experiments. The results indicate that the smart concrete with fiber Bragg grating sensors is feasible in the structure monitoring and damage diagnosing in the long run.

Based on the basic theory of the fiber Bragg grating sensor, a kind of stickup FBG sensor is developed, which is applied in the structure strengthening. With the experiment of the FBG senor and the common electricity sensor stuck on the reinforced structure, the result shows that the FBG sensor not only has a high performance, but also can realize the control on the spot and on the line.

This paper describes the basic principle of fiber Bragg grating sensor, and designs to produce small-size ceramic package Fiber Bragg grating temperature sensor probes. We test the sensitivity, stability, repeatability, response speed of the probe and other parameters affected by the packaging method. To meet needs of practical application, we mainly investigate the response speed of the probe. We take several methods to research response speed of the probe in different temperatures from 35°Cto 42°C, The experiment results show that the reaction time can reach at 2 seconds.