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Flow characteristic properties in pipelines are determined from the temperature evolution, measured by fiber Bragg gratings, after transit of a thermal slug. Results analyze both laminar and turbulent flow regimes.

The lasting effect of applying botulinum toxin type A in a patient with bruxism is analyzed using an interocclusal device instrumented by fiber Bragg grating sensors. The case study involves analyses of maximum bite forces and hyperactivity during sleep for a volunteer patient. In controlled, in vivo , assays, the bite force exerted by the patient is monitored when using the interocclusal device. A maximum bite force of ~38 N was obtained before the application of botulinum toxin. One month after the application, the force had reduced to ~20 N (i.e., by ~57%). By contrast, approximately two months after the application, the force had recovered to 90% of the initial value. In hyperactivity assays, the patient slept with the interocclusal device in position, with the biting activity monitored, before and after the application of botulinum toxin. Prior to the application of botulinum toxin, the mean force was ~28 N, which reduced by 25% after the application. In addition, the time interval between hyperactivity events almost doubled after the botulinum toxin application.

A fractured clavicle fixed with an intramedullary device is studied when subjected to cantilever bending forces, as compared to an intact bone. Results from FBG sen-sors show the strain distribution and point to possible limitations.

In this letter, we present an open-source simulator applied to design and to analyze prism coupling sensors considering surface plasmon resonance (SPR) effect based on Kretschmann's configuration. The open-source simulator is called Sim-SPR and takes into account principles of software engineering. For comparison purposes and to validate our results, we considered two simulation tools already consolidated in the literature and performed an experimental setup for detecting resonant angle in a prism-based SPR sensor. The sensor design was based on optical prism (BK7 glass) as well as Au thin film. The results show that Sim-SPR provides reflectance curves that present a minimum in the resonance condition, resulting in a good agreement when compared with simulation and experimental data. Sim-SPR provides new insights and it has great promise for possible applications in the field of biosensors.

We report the use of optical fiber sensors for monitoring the rhythmic masticatory muscle activity during sleep bruxism episodes, which represents an original approach. Our work measured the hyperactivity of a volunteer wearing different types of occlusal devices that were instrumented by fiber Bragg grating sensors. We compare results obtained with two different occlusal device materials (rigid and resilient). We also investigated thermal images obtained with an infrared camera before and after the sleeping period, to observe the associated temperature changes. The results demonstrated that different hyperactivity can be perceived depending of the material used.

This study evaluates the polymerization shrinkage of a bulk fill flow composite photoactivated by continuous or ramped irradiation. Sample teeth were prepared with Class I occlusal cavity. The fiber Bragg grating sensors are placed along bucco-lingual and mesio-distal directions for measuring the shrinkage and temperature. The results reveal that ramp irradiation protocol showed a slower evolution of shrinkage polymerization curve, but the final values of shrinkage for continuous and ramp protocols are not significantly different. The ramp irradiation protocol showed higher temperature changes than that of the continuous irradiation procedure.

A fiber Bragg grating sensor is used to monitor the temperature of an air-cooled combustion motorcycle engine in this study. The sensor is attached to one of the aluminum cylinders fins of the motorcycle to characterize the heat transfer process. We present the results of the heating and cooling curves during tests with the motorcycle at rest and in motion. A better understanding of the air-cooling process can lead to the optimization of designs in this area.

Fiber Bragg gratings are used to measure the flow in pipelines by means of the temperature evolution, at two different measurement points, after transit of a thermal slug. Results analyze both laminar of turbulent flow regimes.

Contraction due to polymerization of dental resin can cause failure on the adhesive interfaces, can lead to problems such as the appearance of gaps in the interfaces, postoperative sensitivity, pulp damage and the return of the caries. The objective of this work is the study of stresses on the dental adhesive that are generated by the process shrinkage of resin associated with biting forces. A laboratory experiment measured the strains and temperature inside the Filtek

This article discusses procedures for production of tapered fibers in different diameters (tapers) and Bragg gratings writing (tFBG) in such fibers. The reflection spectra in different tFBGs are compared with a FBG written in standard single-mode fiber (SMF28). The gratings were characterized in terms of their thermal sensitivity. Values reasonably close to 11 pm/°C were expected and were obtained in the different gratings in tapers, confirming that the thermo-optical coefficient is predominant in relation to thermal expansion in gratings written in tapered fibers.

This case study describes a new method using a fiber optic Bragg grating sensor to determine muscle fatigue in a patient wearing a resilient occlusal device for the treatment of bruxism symptoms. Four tasks performed at maximum bite force induced rapid exhaustion for the analysis of fatigue. The results show that it is possible to obtain a better understanding of the muscle fatigue process by using the fiber sensor. Differences between the bite patterns are detected at each phase of the induced fatigue. It is possible to compare the bite peak sensitivity coefficients for the exhaustion phase, 1.37 Ns-1, and for fatigue phase, 2.54 Ns-1. Additionally, the increase in the facial thermal profile is correlated to the different bite force pattern performed.

An automated system is reported in this work with the goal of fabricating photonic structures by the direct-write technique with femtosecond laser pulses. This technique uses a fine focused laser beam into transparent substrates and the translation of the substrate parallel or perpendicular to the propagation direction of the incident laser beam. Control procedures related to laser pulses and the sample translation were implemented and integrated, giving rise to a fully automated femtosecond writing system. Functional straight-line and curved waveguides have been successfully achieved with the automated writing system, where single-mode propagation is observed from their near-field profiles when 635-nm light is injected and guided. In addition, the possibility of writing 2D and 3D photonic structures is confirmed by tracing a logarithmic spiral structure (2D) and a fan-out structure (3D). These results show that the developed system is fully operational in practice for the purpose of fabricating a variety of photonic structures with potential applications in the modern communication networks and integrated photonic circuits.

This paper describes an optical-fiber sensor development and implementation, based on Bragg gratings, to measure the mechanical deformation at the bone surface of a bovine mandible, caused by chewing different types of food and rumination. A suitable encapsulation was developed using a titanium mesh as a transducer and sensor calibration and characterization tests were performed. The proposed sensor was deployed in a living animal transmitting the detected bone deformation to the data collecting instrument. The acquired signal was applied to a pattern-classification algorithm based on decision trees for identifying the chewing process of different foods. The results demonstrate that the sensor is effective and sensitive, capable of capturing the force generated during the masticatory process.

This work describes the hydrogenation, writing and thermal treatment process of seed fiber Bragg gratings – FBG, written with spectra in the visible range by an Ion argon laser. Those gratings have different writing times. After writing, those FBGs are submitted to thermal treatment to induce regeneration. The processes are followed to compare the spectral parameters.

This work reviews the use of Bragg grating sensors (FBG) for in vivo analysis of biomechanics behavior. Two apparatuses are studied, a mechanical hand grip and an occlusal splint, both devices instrumented by FBG. The results obtained along dynamics assays indicate that the instrumented devices are a powerful appliance for biomechanical analyses, like muscular fatigue.

This study evaluates the polymerization shrinkage of two types of acrylic resins using two methods of splinting. Two implants were placed in an artificial bone, with the two transfer copings joined with dental floss and acrylic resins. Measurements of shrinkage and temperature were performed with fiber Bragg grating sensors. The results revealed that both resins showed similar shrinkage values, although one of them also showed a higher temperature increase. The measured values demonstrated that the separation and reconnection of the splinting with acrylic resin is effective at relaxing stress polymerization and reducing shrinkage polymerization.

Statement of problem Information regarding the shrinkage kinetics and monomer conversion of dual-polymerized conventional and self-adhesive resin luting agents (RLA) in situ is lacking. Purpose The purpose of this in vitro study was to evaluate the shrinkage strain and ratio of 1 conventional and 1 self-adhesive RLA by using fiber optic sensors based on Bragg gratings and Vickers hardness in the root canal. Material and methods The root canals of 34 single-rooted premolars were endodontically treated and assigned to 2 groups according to the RLA: RelyX ARC (ARC) and RelyX U200 (U200). Two Bragg grating sensors were attached to fiber posts (n=10), and both post and RLA were placed inside the root canal so that shrinkage strain and ratio values could be measured at the cervical and apical root thirds. For hardness analysis (n=7), two 1-mm-thick slices of each root-third (cervical and apical) were obtained, and 4 indentations were made on the RLA layer. The shrinkage strain and rate, as well as hardness data, were evaluated by using 2-way repeated-measures ANOVA followed by the Bonferroni post hoc test when a significant interaction between factors was detected (α=.05). Results The shrinkage strain and rate values of both RLAs were higher at the cervical third than those at the apical third. ARC showed higher shrinkage strain than U200 at the cervical third. The highest hardness values were observed at the cervical third, while ARC showed the lowest hardness values at the apical third. Conclusions The shrinkage kinetics profile and hardness of self-adhesive RLA may differ from those of conventional RLA depending on the root third.

We investigated a vertical organic field effect transistor (VOFET) behavior with an intermediate electrode formed by a tin (Sn) layer, whose growth presents a self-organized pattern grid with natural pores, fundamental to its operation. The choose of the materials to compose the channel formed by a fullerene ( $$\text {C}_{60}$$ ) and a intermediate electrode of Sn brings a structure able to work with very low voltage and ambipolar gate biasing behavior, concomitantly. A explanation based on the importance of the roughness/pores in the intermediate electrode and the control of the energy barrier of the injection interface clarifies how to obtain the on–off state in unipolar VOFETs with ambipolar gate biasing. A theoretical basis support that when there is a low injection energy barrier inside and outside of the pores from a roughness intermediate electrode the electrical characterization its a combination of a very low voltage operation with a non negligible off-output current.

Analysis of the state of polarization of light guided by structures recorded in crystals of lithium niobate and lithium fluoride indicates that the recording method is determinant in the formation of birefringent structures. Each structure was written with a single and continuous translation of the crystal transversally to the laser beam. The characteristics of the birefringence of the structures recorded are observed in both crystals, even for lithium fluoride lacking intrinsic birefringence. In the case of the lithium niobate structure there is different areas with different degree of birefringence. The structure generated with femtosecond laser is directly linked to the recording method and the crystalline lattice can provide advantages for application in photonic devices.

The widespread use of smartphones forecasts huge increase in application-based portable sensors, particularly using the embedded light source and camera detector. Albeit Fibre Bragg gratings (FBG) were originally discovered at visible wavelengths, their commercial and scientific dissemination is predominant in the C-band of optical communications. Recently, several authors gave attention to FBG in the visible, aiming simpler and low-costly interrogation methods that could increase the application of FBG sensors in biomedicine, immunology and biophysics. We study the detection of VIS FBG using standard lamps or LEDs coupled to VIS, silicon based, CCDs in commercial instruments. We show that is possible to record the FBG spectrum with adequate signal to noise ratio,allowing hand held FBG interrogation methods in diverse environments.

This study evaluated the shrinkage polymerization of two dual-curing resin cements during in vitro and in situ tests, using fiber Bragg grating with different curing time periods. The cements used were: Relyx ARC (dual conventional) and Relyx U200 (dual self-adhesive). For the in vitro experiment, the resin cements and the sensors were placed between two glass coverslips and afterwards were photoactivated for 40 s ( N = 20). For the in situ experiments, 20 human teeth were prepared to receive root posts cemented with the same two resin cements. Two sensors were glued to the posts’ surfaces at the coronal and apical thirds. Next, the cementation of the posts was photoactivated for 40 s. The sensors measured the strain for 60 min in both experiments. Data from in vitro and in situ experiments were analyzed by three-way ANOVA and Games–Howell multiple comparison procedures. Data from the coronal and apical thirds were analyzed by two-way ANOVA and T-test. The results showed that the polymerization shrinkage values are similar for the in vitro and in situ experiments, that contraction is greater after 5 minutes curing time compared to the contraction at 60 min, that both resin cements performed similarly and that the shrinkage measurement at the cervical third showed higher values than those at the apical third.

In this work, several temperature sensors were produced and encapsulated using Bragg fiber optic gratings (FBG). The FBGs were recorded in the infrared bands using standard telecommunication single-mode optical fiber (G-652). The fiber used does not undergo thermal pre-treatment in the production of standard FBG and undergoes a previous hydrogenation process to produce the regenerated Bragg gratings (RFBG). In the RFBG production process we use heat treatment at 850°C and the resulting gratings can be applied in long term measurements at temperatures lower than that of regeneration. FBGs and RFBGs were encapsulated with ceramic material alumina (Al2O3) and stainless steel to facilitate application as a sensor. A comparative study of thermal sensitivity for different capsules and compared with non-encapsulated optical fiber was done.

Bulk fill flow composites reduce patient’s chair time by replacing the incremental technique. Continuous and ramped irradiation are used for the polymerization; deformation and temperature are studied by fibre Bragg grating sensors.

Regenerated fibre Bragg gratings (RFBG) are obtained by heating an original seed grating until its reflection practically vanishes, which is followed by the growth of a new reflection band. Advantages of RFBG for sensing purposes are the longer lifetime and higher thermal stability at higher temperatures, as they have been observed to survive temperatures in the range 1300-1500 °C. The thermal stability of the RFBG permits several applications not attained by standard Bragg gratings.

In this paper a method to evaluate the presence of microorganisms of the coliform group in water samples using the ultra-weak bioluminescence (UWB) is proposed. A series of UWB measurements and optical density measurements from cultures of both a set of standard E. coli strain samples, and a set of water samples from a river near Curitiba City in Brazil were performed. All samples were previously incubated at 37 °C for 11 h in nutritive medium before the temporal UWB emission profiles data were acquired for a period of 24 h inside a dark chamber of an especially implemented instrumentation capable of doing photon counting measurements. For the optical density measurements, a spectrophotometer was used to acquire the growth kinetics of those cultures for a period of 13 h, and the results compared to the UWB profiles. Periodic time-components analysis of the UWB data from both the set of standard E. coli samples and the set of the river's water samples were performed and compared to each other. The results have shown that the UWB temporal profiles resemble in some way the growth kinetics curve and the periodic time-components analysis is an effective way to discriminate between contaminated and non-contaminated samples, therefore the method may be viable for detecting coliforms in water samples in less time than usual methods.

A visible fiber Bragg grating (Vis-FBG) with wavelength peak centered at 673.07 nm was inscribed in a multimode fiber designed for infrared (IR) operation using a femtosecond (fs) laser emitting at 248 nm. The fiber cladding is removed by chemical etching in hydrofluoric acid solution (40%). The sensor refractive index response is determined by dipping the sensor into diluted glycerin solution at different concentrations with refractive index range from 1.3328 to 1.4607. The Vis-FBG performance is compared with an IR etched FBG (EFBG) with similar diameter. The sensitivity found for the Vis-FBG sensor is 15.71nm/RIU with a 6.34 x 10 -3 RIU resolution for a refractive index of 1.4607.

In this work we report the development of a method to characterize occlusal splints using fiber Bragg grating sensors. The occlusal splints are used to treatment for muscle pain resulting from parafunctional habit and or occlusal alterations. The gratings are inserted in to the occlusal splints in order to measure the forces applied to the splints. The analyses are performed in a volunteer with bruxism, in order to obtain the sensibility to the applied load. The analyses of the force distribution in the splint are realized in vivo and the results indicate that the proposed method is a powerful tool for the characterization of occlusal splints.

The technique recommended to achieve adhesion of composites to the enamel and dentine in dentistry is incremental with gradual photo-activation. Bulk fill composites were developed to reduce the clinical time and shrinkage polymerization. There are two types of bulk fill composites according the viscosity. The present study evaluates the shrinkage and temperature change during the polymerization of a bulk fill composite of low viscosity inside a teeth cavity, prepared to replace teeth tissue lost by caries and fractures. Fiber Bragg grating sensors are used in this investigation due their great sensibility and small dimensions. The results reveal shrinkage polymerization of −863±168 μe and temperature change of 12±7°C. The temperature variationis high and can compromise the pulp vitality.

We report regeneration studies of fiber Bragg gratings with resonance band in the visible spectral range. The FBG were produced by direct illumination under the phase mask using UV light from a fs-laser pumped optical parametric amplifier. Some seed gratings were not so saturated as common C-Band gratings written by other methods but their regeneration efficiency is quite high. The final line-widths are narrower than the similar C-band regenerated gratings.

We report an optical fiber multiparameter sensor for refractive index and temperature measurements. The proposed sensor is composed by a microcavity in multimode fiber, assisted by Bragg gratings (FBGs) in singlemode fiber. The microcavity is engraved in a multimode optical fiber by using the femtosecond laser micromachining. The sensor is characterized through microcavity immersion in water and based on its temperature variation. The results show that it is possible to obtain refractive index and temperature measurements with sensitivities of 1625 μW/RIU (refractive index unit) and of 0.23 μW/°C, with resolution of 1.8 × 10−4 RIU and of 1.3 °C.

The description of an interrogation system for fiber Bragg grating sensors is reported. The full implementation in hardware of the required signal processing is proposed and made publicly available. The hardware description is implemented in a field programmable gate array (FPGA) development kit and the processing units allow one to control an optoelectronic interrogation system that uses the tunable filter method. Since the signal that drives the used Fabry-Perot filter (FFP) using a digital-to-analog converter (DAC) requires the generation of a triangular/saw-tooth waveform, the non-linear behavior of the DAC is compensated with a new methodology in this application using FPGA. When it operates controlled by a personal computer, off-board additional adaptive signal processing is used to suppress optical interference in an innovative way while removing undesired distortions in the signals caused by reflections in the optical circuit.

Thermal stability of both standard and regenerated Bragg gratings written in normal and photosensitive optical fibers was accessed. An apparent spectral wavelength stabilization of common gratings with no thermal hysteresis was reached after thermal treatments. However, after a time interval of 5 months, gratings exhibited a shift in the resonance Bragg wavelength at room temperature, as well as important changes in the thermal sensitivity above 200 ºC. Regenerated gratings proved to be stable only at temperatures below the critical regeneration temperature, with significant loss of reflectivity above that critical value.

This paper reports an effective method of packaging a fiber Bragg grating (FBG) for the simultaneous measurement of temperature and strain. The technique consists of embedding two fiber Bragg grating sensors inside a polymeric material with different geometrical characteristics. The mechanical and thermal characterizations of the optical transducer were performed. Then a matrix equation used measurements of the wavelength shifts from the two sensors and yielded information about the temperature and strain coefficients. The preliminary results demonstrate the feasibility of the encapsulation technique allowing measurements of temperature and strain in smart structures and harsh environments. The experimental procedure provides robustness to the sensor and the matrix equation approach has the potential to determine simultaneously the strain and temperature coefficients.

This works presents the simulation and validation of the thermal, electrical and mechanical models of a three-phase induction motor (TIM). Fiber Bragg grating (FBG) sensors are used to measure stator temperature and validate the thermal model. The knowledge of the relationship between losses and temperature variation in the TIM makes a simulation of the motor possible. To determine losses in the TIM an equivalent electrical circuit in arbitrary reference frame is used, which combines a traditional model with the more usual modeling of losses in the stator iron. The thermal study of the motor is performed using an equivalent thermal circuit formed by thermal capacitances and thermal conductivities that are separately considered for the stator and rotor. The losses calculated with the electrical and mechanical models are the input parameters for the thermal model. The simulation of the electrical model produces an error of approximately 4.2% when determining the Joule effect losses in the motor when compared to the experimentally obtained results. The simulation of the mechanical model presents an error of 0.2% for the losses due to friction and ventilation. The stator and rotor temperature, obtained with the thermal model, presented a high correlation with the measured values. The thermal model presents a maximum error of 0.75 °C when one compares them to the average experimental values of temperature in the stator during the temperature transient behavior. When the temperature in the stator reaches steady state, the experimental and simulated results converge to the same values. The use of FBGs to measure temperature in the machine allowed a thermal model to be developed, which also uses the mechanical losses of the machine and is the main contribution of this work.

Ultra-weak photon emission (UWPE) detection and measurement from biological samples is a promising tool with potential use in several fields such as agriculture, environmental science, food science and biomedicine. An instrumentation based on a photomultiplier module (PMT) is presented, and its performance in terms of dark-noise and bacteria detection was evaluated in order to assure that it is able to feasibly realize UWPE measurements applied to sanitary control. The UWPE counter relies on a dark-chamber and a PMT. The PMT window is placed in the center of the chamber, sight above a Petri's dish that contains the biological sample. under measurement rests. The PMT is cooled down to 10°C to minimize the dark-counts. At 10°C the dark-count is around 17 counts/s, which is feasible for E. coli detection.

The thermal and deformation properties of fiber Bragg gratings (FBG) in the visible range were characterized for the first time in our knowledge. The FBG were written in silica single mode (cutoff in the visible and infrared range) and multimode fibers, using a phase-mask (460 nm period) illuminated by a 248 nm femtosecond laser.

The aim of the study is to demonstrate the potential of the fibre Braggs grating (FBG) in the measurement of different jaw movements that are performed for patients with occlusal parafunction using occlusal splints. Two silicon plates each 2mm are used, the fibre optic sensor is positioned in the maxillary left first molar region above the point of contact with opposing tooth after pressing the first plate on the model. Then the second silicon plate is pressed. The device has a final thickness of 2 mm. The occlusal splint is installed in the mouth of the patient who underwent different movements on occlusal splint. The maximum frequency bite is monitored. The results demonstrate that the bite shows a difference between grinding and clenching movements. The curves behaviour patterns are presented in order to show these different comparisons. Therefore, it is concluded that the fibre Braggs grating consists in an efficient method for monitoring the mechanical behaviour bite of patients with occlusal splints.