Fiber Bragg Grating Temperature Sensor Research Articles

Single-Mode versus Multimode Fiber Bragg Grating Temperature Sensors: A Theoretical Study

This paper aims to enhance understanding regarding the impact of the geometrical parameters of the grating on the transmission spectrum of single-mode and multimode fiber Bragg grating sensors and to compare the performance of both sensors for temperature monitoring. Furthermore, we propose a novel design where we combine between phase shifted and tilted grating in MMFBG sensors to further enhance their sensitivity and make them more suited for temperature sensing applications. In this regard, a numerical simulation using the eigenmode expansion (EME) solver of Lumerical software is conducted. Analysis of the obtained results suggests that the multimode Fiber Bragg grating sensor has the potential to be used as a temperature sensor with good sensitivity when it is well designed.

Underwater temperature and pressure monitoring for deep-sea SCUBA divers using optical techniques

The safety of SCUBA divers remains at high risk in deep-sea owing to multiple factors such as dangerous surrounding, rely upon technical equipment necessary for life support, decreased underwater navigation, and communication infrastructure. Gradual decrease and increase in water temperature and pressure corresponding to depth are among the most common problems that cause most of the fatalities in deep-sea diving. Therefore, different gadgets for accurate measurement of vital parameters, reliable navigation, and seamless communication are of prime importance. In this paper, we propose an all-optical technique for local and remote monitoring of underwater temperature and pressure for deep-sea SCUBA divers based on fiber Bragg grating (FBG) sensors and underwater optical communication-single mode fiber (UWOC-SMF) integrated transmission system. The proposed technique is implemented using two FBG temperature and pressure sensors fixed over diver’s suit and UWOC-SMF integrated transmission system for simultaneous local and remote monitoring of underwater temperature and pressure. Remote monitoring of underwater temperature and pressure is achieved at ship station through a remotely operated underwater vehicle (ROV) and UWOC-SMF integrated transmission system by means of shifts in the original Bragg wavelengths of sensors due to temperature and pressure variations. The performance of the sensors is analyzed for pressure and temperature in the range of 0 to 6.4 MPa (≈0 to 655 mH2O) and 40 to −2°C, respectively corresponding to different depths. The results show that the proposed technique can work well in the deep ocean over a range of pressures and temperatures of 0–7 MPa and 40 to −2°C while achieving a temperature sensitivity of 4.3 p.m./°C and a pressure sensitivity of 30.5 p.m./MPa. Clear spectra of reflected signals from FBG sensors at ship station are achieved after signal transmission over UWOC-SMF hybrid link.

Dual-modal fiber-optic sensor for simultaneous pH and temperature monitoring in tumor microenvironment

The tumor microenvironment (TME) is a complex system. Temperature, pH, oxygen content, and other biomarkers comprehensively reflect the growth state of the tumor, necessitating a multi-parameter detection strategy to garner the precise status of tumor for treatment guidance. Fluorescence imaging technology is a promising tool for realizing this goal due to its advantages of low cost, real-time responses, and high sensitivity. However, several limitations, including the shallow penetration depth of fluorescence signals in biological tissues and the potential crosstalk between multiple fluorescence signals, hinder the practical application of current fluorescence imaging technology. In this paper, a dual-mode optical fiber sensor consisting of a fiber fluorescence pH sensor and a fiber Bragg grating (FBG) temperature sensor is presented. The compact sensor uses different principles for pH and temperature monitoring, thus effectively eliminating potential crosstalk between different signals. In addition, its small size allows it to be inserted into deep tissues for detection. The sensor responds quickly to changes in pH.Moreover, the temperature sensitivity of FBG packaged with PDMS is 34 % higher than the uncoated FBG. In vivo experiments confirmed that the sensor can accurately distinguish normal tissues and tumor tissues. The proposed sensor provides a novel way to realize multi-parameter monitoring of tumor microenvironment and improve the specificity of tumor detection.

In-situ optimization of lateral film uniformity in PVD system by using Fiber Bragg grating temperature sensors

Fiber Bragg grating (FBG) based temperature sensing method has been employed in this work for measuring the lateral temperature distribution on substrate plane during pulse DC magnetron sputtering deposition for optimization of lateral film uniformity. The evolution of temperature distribution with the variation of important process parameters like pulse width (496–1616 ns), deposition pressure (3.1 × 10−3–1.9 × 10–2 mbar) and sputtering power (25–250 W) have been measured over 40 mm radial distance on glass substrate horizon. To investigate the effect of substrate height on the temperature distribution, the later has been measured at two different substrate heights (60 mm and 90 mm) for varying sputtering power. Finally, the effect of variation in temperature distribution on uniformity of thickness and optical, morphological and structural properties have been investigated by separately depositing two HfO2 thin films at two representative extreme deposition powers (75 W and 200 W). The correlation of film non-uniformity of the above properties with the temperature distribution suggests that FBG based multipoint temperature sensing can be possibly used as an indicative tool for in situ optimization of the lateral film uniformity. In addition, the fast response and workability in plasma environment of FBG sensors enables precise in situ mapping of temperature distribution in sputtering process.

Sensitivity-Improved Fiber Bragg Grating Temperature Sensor Based on Microwave-Photonic Enhanced Vernier Effect

Sensitivity-Improved Fiber Bragg Grating Temperature Sensor Based on Microwave-Photonic Enhanced Vernier Effect

Assessment of Tunnel Lining Stability through Integrated Monitoring of Fiber Bragg Grating Strain and Structural Deformation.

Tunnel excavation induces the stress redistribution of the surrounding rock. Structural cracks may develop in the secondary lining due to this stress redistribution and bias pressure, consequently affecting the overall construction safety of the tunnel. This paper aims to achieve real-time monitoring of the excavation stability of the lining structure by integrating two monitoring technologies: structural deformation monitoring and fiber grating strain monitoring. Additionally, it proposes a method to simultaneously measure the thermal strain and applied stress-strain of the structure. By analyzing the displacement and deformation of the lining structure, its stability can be preliminarily evaluated in the short term. To achieve long-term real-time monitoring and a more accurate assessment of the tunnel structure's stability, the paper introduces fiber Bragg grating (FBG) strain sensor monitoring technology. First, based on the geological stratigraphy information obtained from the exploration, a simulation model of the tunnel under different section bias angles is established. The displacement and stress concentration areas of the lining structure are then analyzed to optimize the sensor deployment array and provide a theoretical basis for the sensor arrangement. FBG strain sensors are installed on the surface of the structure to measure thermal strain and loading stress-strain, whereas FBG temperature sensors measure local temperature. The findings indicate that following tunnel excavation, the maximum daily strain differences at K107+043 and K107+240 were 126.87 µε and 209.38 µε, respectively. After a period of rock disturbance, the average daily strain differences due to applied stress-strain were 16.8 µε and 12.65 µε, respectively. The thermal strain was close to the daily strain difference. Therefore, after the rock disturbance subsided, the strain fluctuations in the lining structure were mainly caused by local temperature changes, and the surrounding rock tended to stabilize. This offers a viable method for evaluating structural stability post-tunnel excavation.

A novel packaging method for FBG temperature sensors based on ultrasonic-assisted soldering technology

The packaging technology of fiber Bragg grating (FBG) sensors is the key to determining their operational performance. A method for encapsulating FBG temperature sensors using ultrasonic-assisted soldering technology has been proposed and attempted. This packaging method is based on the successful connection between SiO2 quartz glass and Invar alloy. Implementing this soldering connection depends on the active components in the solder, which are dispersed into SiO2 and metal alloys to form more stable substances. The FBG with the removed coating is reliably connected to the metal capillary through ultrasonic soldering. The fragile FBG is adequately protected in the capillary. Sn-based solder with a melting point of 297 ℃ has been selected. The soldering temperature of 330 ℃ avoids significant residual stress caused by the difference in the thermal expansion coefficient of the material at the joint. Excellent bonding strength between optical fibers, solder, and capillaries is necessary for encapsulating sensors. Compared to adhesive, solder packaging is no longer affected by the creep of the sealant. The results show that the working range of FBG temperature sensors encapsulated in epoxy resin is −25 ℃ −115 ℃, while temperature sensors encapsulated by welding can operate stably at −50 ℃ −280 ℃. Sensors packaged using ultrasonic-assisted soldering technology have the potential to be embedded in metal substrates, creating favorable conditions for the development of intelligent electromechanical components.

A Comprehensive Review of MEMS-enabled Dual-mode Pressure and Temperature Sensors

This paper offers an examination of MEMS-enabled dual-mode sensors, emphasizing key concepts, technologies, and developments in the area. Micro-Electro-Mechanical Systems, or MEMS, have revolutionized sensor design, enabling the creation of small, effective, and multipurpose devices for simultaneous monitoring of temperature and pressure. The review begins with how MEMS and Integrated Circuits (ICs) are integrated into sensor systems and explores MEMS incorporation into dual-mode sensors, clarifying crucial manufacturing processes and design approaches. Furthermore, the paper classifies and examines basic MEMS sensor types, such as Surface Acoustic Wave (SAW), Barometers, Differential Pressure Sensors, Absolute Pressure Sensors, Strain Gauge Pressure Sensors, Accelerometer-Based Pressure Sensors, Magnetometer-Based Pressure Sensors, Fiber Bragg Grating (FBG) Temperature Sensors, and Force Sensors.

Dual-parameter combined measurement sensor based on tri-metal structure

Simultaneous measurement of strain and temperature in vibrating environments has always been a key technical issue in the field of structural health monitoring. To address the bottleneck of inadequate dual-parameter measurement performance in existing Fiber Bragg Grating (FBG) strain and temperature sensors, a new type of fiber optic grating sensor with anti-vibration capabilities for the measurement of both strain and temperature is proposed. The sensor utilizes a flexible hinge structure made of 304 steel with high elastic modulus for strain sensitization and a bimetallic structure composed of 7075 aluminum and 4 J36 Invar alloy for temperature sensitization, integrating both types of sensors. Theoretical analysis of the sensor was conducted, followed by the fabrication of a prototype and the establishment of a testing system for performance evaluation. The results show that the designed dual-parameter FBG sensor has a strain sensitivity of approximately 3.06 pm/µε, about 2.62 times that of a bare FBG, and a temperature sensitivity of about 50.2 pm/℃, roughly 4.97 times that of a bare FBG. In anti-vibration performance tests between 5–100 Hz, the wavelength drift of the strain and temperature sections of the FBG in the sensor were both within 1 pm, meeting the requirements for simultaneous measurement of strain and temperature in vibrating environments. These findings provide a reference for the development of similar sensors and further improvement of the measurement performance of FBG strain and temperature sensors.

Dynamic characterization of Fiber Bragg Grating temperature sensors

To reliably characterize fast dynamic heat transfer mechanisms, fast-response temperature sensors are crucial, including knowledge about the temporal response. In this paper, the dynamic behavior of a Fiber Bragg Grating temperature sensor is investigated and compared to different types of fast-response thermocouples using two different experimental dynamic characterization methods. A temperature step is generated by either plunging the sensor into a fluid or exposing it to a fluid droplet at different temperatures. The step response is evaluated to determine the sensor response time. Calibration runs are performed for a silica-based 0.125mm FBG sensor, as well as for 0.16mm and 0.8mm exposed tip and 0.25mm sheathed tip type K thermocouples. Water, glycerin, oil and GaInSn were used to cover a broad range of applications regarding different thermal diffusivities and viscosities. The FBG sensor showed the shortest response times compared to the thermocouples, ranging from 60ms in oil down to 3ms in liquid metal, which is 20% up to 70% faster compared to a 0.25mm sheathed tip type K thermocouple. Additional plunging calibration runs of the FBG sensor were performed in a ternary nitrate molten salt mixture (HITEC) to determine its overall and dynamic behavior in corrosive fluids at elevated temperatures. It turns out that the FBG sensor is not affected by the molten salt and shows similar response times to those measured in water. Regarding the characterization methods, both techniques show reproducible results, even though the droplet method is inapplicable for sensors with higher heat capacity or lower thermal conductivity than the calibration fluid. Furthermore, splashing effects for fluids with low viscosity reduce the reliability of the droplet method. The results also show that a dynamic characterization is indispensable for temperature measurements with high temporal resolution because the response time depends on the sensor size and the heat transfer coefficient between sensor and surrounding, which in turn depends on the sensor type, fluid properties and the flow parameters.

Research on sensitized Fiber Bragg Grating temperature sensor based on bimetal three-substrates.

Temperature is one of the most important physical quantities in the field of earthquake precursor observation. Aiming at the problem of low sensitivity in the Fiber Bragg Grating (FBG) temperature sensor, the sensitized FBG temperature sensor based on bimetal three-substrates is proposed. Through theoretical analysis of the bimetallic model, the structural parameters of the sensor are optimized, and the sensor is simulated and analyzed with ANSYS. Then, the sensor is developed according to the simulation results, and the temperature test system is built to test the performance of the sensor. The results show that the sensitivity of the temperature sensor is 49.3 pm/°C, which is about 4.9 times that of the bare FBG sensor, and the linearity is over 0.999. The research results provide a reference for developing the same type of sensors and further improving the sensitivity of FBG temperature sensors.

Multipoint Temperature Measurement System for Aero-Engine External Piping Based on Arrayed Fiber Bragg Grating Temperature Sensors

Multipoint Temperature Measurement System for Aero-Engine External Piping Based on Arrayed Fiber Bragg Grating Temperature Sensors

Modeling analysis and experimental study on epoxy packaged FBG sensor for cryogenic temperature measurement

The Fiber Bragg grating (FBG) is a kind of temperature-sensitive optical device that has irreplaceable advantages for cryogenic measurement. In this work, a model-driven FBG temperature sensor packaging method was proposed to improve the sensor’s sensitivity and linearity and predict the sensor's response time in cryogenic. The numerical model explores the relationship between the sensor’s size and performance. The packaging method can prepare high-precision samples of multiple sizes and provide experimental support for this study. The accuracy of the model is verified by comparing the calculated results with the results of a warming-up experiment and a liquid nitrogen experiment. The results show an improvement in sensitivity and linearity, and the model can also be used to predict the characteristics of FBG coated with epoxy resins at cryogenic temperature. The sensor with a thickness of 0.2 mm has a sensitivity and linearity of 26.6 pm/K and 0.997, respectively, in the range of 80 K-270 K.

Fiber-cavity ring-down temperature sensor using a transmissive configuration combined with the heterodyne detection technique.

A fiber Bragg grating temperature sensor based on the cavity ring-down technique is reported. A quasi-linear fiber cavity is proposed to reduce optical loss in the cavity instead of a conventional fiber-loop configuration. The heterodyne detection technique is applied to sensitively detect weak pulses from the cavity. A combination of the quasi-linear fiber cavity and heterodyne detection allows the sensitive detection of the decaying pulse trains and high-resolution measurement of the wavelength shift of the Bragg grating induced by the temperature change. A temperature resolution of about 0.01°C is achieved.

Modelling and analysis of fiber Bragg grating temperature sensor for Internet of things applications (FBG-4-IoT)

The integration of Fiber Bragg Grating (FBG) sensors into the Internet of Things (IoT) has garnered significant attention in recent years because of their immunity to electromagnetic and radio frequency interference, small size and weight, and corrosion resistance. This paper aims to enhance the performance characteristics of FBG sensors for temperature measurement by proposing a specific design of their parameters, thus facilitating their implementation in IoT applications. The FBG temperature sensor is designed to operate in the 1500–1600 nm wavelength range. The outcomes display a high sensitivity of 0.61 nm/°C with a Full Width Half Maxima (FWHM) of 7.893 nm and a Figure of Merit (FOM) of 7.72 x 10−2/°C. The calculated Quality Factor (Q) of the sensor was 195.67. When compared with previous studies in the literature, our obtained results confirm the enhanced performance of the proposed design of the FBG sensor, which render it suitable for utilization in most industrial use cases, especially in harsh environments.

Monitoring experiment and simulation on solidification of DNAN based melt‐cast explosive with FBG sensors

AbstractIn order to obtain the change rule of the temperature field and the mechanism of defect formation during the solidification process of melt‐cast explosive, the temperature field change data were tested during the solidification process of DNAN based melt‐cast explosive by using an arrayed spatially distributed Fiber Bragg Grating (FBG) temperature sensor device. The temperature field variation during the solidification experiment was obtained under the condition that the cooling rate of the boundary water‐bath temperature was 0.2 °C/min. On the basis of the solidification experiments, the macroscopic solidification process of small‐caliber grenade at different boundary cooling rates was simulated using ProCAST software. The simulation results show that when the boundary cooling rate is 0.2 °C/min, the temperature fields during the solidification process of DNAN based melt‐cast explosive are in good agreement with that of the experimental monitoring points; the size of the melt‐cast charge defects decreases as the boundary cooling rate becomes smaller; and the location of the charge defects is closer to the tail of the grenade as the cooling rate decreases. In addition, a mesoscopic model of DNAN based melt‐cast explosive was established in the paper. At the mesoscopic level, the generation, formation, and evolution of charge defects in DNAN based melt‐cast explosive during solidification were investigated. The study results provide theoretical guidance for the formulation design and process optimization of DNAN based melt‐cast explosives, as well as for improving the charge quality of ammunition.

Design of High Performance Triangular Fiber Bragg Grating Temperature Sensor using OptiSystem and OptiGrating Software

This paper presents on the design of high performance triangular Fiber Bragg Grating (FBG) as temperature sensor. This triangular FBG is designed and simulated using OptiGrating Software. The Triangular FBG design is exported to OptiSystem Software. In the OptiSystem software, the overall triangular FBG temperature sensor system is designed and simulated. It found that the triangular FBG has higher temperature sensitivity which is 37.5pm/°C than the standard FBG which is around 13pm/°C. It also has high linearity of 99.2% which specifies the consistency of wavelength shift as the temperature is increased. It also has higher resolution due to its sharp peak and smaller bandwidth.

Application of a fiber Bragg grating temperature sensing method based on support vector regression optimized by a genetic algorithm for the decreasing external ambient temperature case.

We studied the application of the fiber Bragg grating (FBG) temperature sensing method based on support vector regression optimized by a genetic algorithm (GA-SVR) for constant and decreasing external ambient temperature cases by simulation. The external ambient temperature could be retrieved from both the transient FBG wavelength and its corresponding change rate using GA-SVR, before the FBG temperature sensor reached the thermal equilibrium state with the external ambient temperature. FBG wavelengths and their corresponding change rates in the cases of FBG sensor temperatures higher and lower than the external ambient temperature were studied and used to construct the training data set. We found that there exist singularity points in the curves of the wavelength change rate when the FBG sensor temperature is higher than the external ambient temperature in some cases, which is different from the case where the FBG sensor temperature is lower than the external ambient temperature. Its application for sensing the constant and decreasing external ambient temperature in real time was demonstrated with an accuracy of 0.32°C in those two cases. It also indicates that for real applications of this temperature sensing method where the external ambient temperature varies randomly, the FBG sensor temperature changes rather than the external ambient temperature changes play the dominant role. What is more, the demodulation time was decreased to 0.002s, which is approximately 0.05‱ of the time constant of the FBG temperature sensor. In other words, this method makes it possible to realize the external ambient temperature determination using a time smaller than the time constant of the FBG sensor. The high sensing accuracy and fast demodulation speed are crucial for future high-performance real-time FBG temperature sensing.

Dynamic adsorption behavior of 1.1.1.2-tetrafluoroethane (R134a) on activated carbon beds under different humidity and moisture levels

1.1.1.2-Tetrafluoroethane (R134a) is developed as a tracer for mechanical leakage detection in military chemistry. Due to the weaker physical adsorption properties, water vapor competitive adsorption limits the use of tracer R134a. Thus, it is urgent to the analyze dynamic competitive adsorption behavior of R134a and water vapor on the activated carbon. In this study, R134a breakthrough curves on the fixed beds packed with activated carbons under different relative humidity and moisture content levels were systematically measured. Combining mass spectrometry, gas chromatography, and a novel fiber Bragg grating temperature sensor, the dynamic competitive adsorption processes and axial temperature of fixed beds were first reported. Interestingly, with increasing moisture content, R134a breakthrough time decreased, but dynamic adsorption capacity increased. This was attributed to the fact that the residual water vapor could increase the specific surface area and pore volume of activated carbon to enhance R134a dynamic adsorption capacity. Using the R134a as the standard, the dynamic competitive adsorption process was first revealed and could be divided into four stages including Co-adsorption, Co-breakthrough, Competitive Adsorption (“Rolling Up” and “Adsorption Platform”), and Dynamic Adsorption Equilibrium. “Rolling Up” and “Adsorption Platform” phenomena are mainly determined by the strength of intermolecular interactions, the concentration difference of adsorbate, and the thermal effect induced by water vapor adsorption/desorption.

Application of FWM-Based OFC for DWDM Optical Communication System with Embedded FBG Sensor Network

Abstract Four-wave mixing optical frequency comb fibre-based setups (FWM-OFCs) have the potential to improve the combined dense wavelength division multiplexed passive optical network (DWDM-PON) and fibre Bragg grating (FBG) temperature sensors network providing easier application, broader technological opportunities for network development, and energy efficiency by substituting a power-demanding laser array. In this research, OFCs are generated for the purpose of combined network application of DWDM-PON and FBG optical sensors. The paper also investigates compatibility scenarios with OFCs in such systems. The mathematical simulation model has been developed and the performance of FWM-OFC based 8-channel 50 GHz spaced non-return-to-zero on-off keying (NRZ-OOK) modulated DWDM-PON transmission system, operating at 50 km single-mode fibre (SMF) with a bit rate of at least 10 Gbps embedded with 7 FBG optical temperature sensors, has been studied. As it is shown, FWM application results in OFC source that has fluctuations of the individual comb tones of less than 3 dB in power, and with an extinction ratio of about 33 dB for operation range of 192.9–193.25 THz, acting as a unified light source for all the data transmission channels. Embedded FBG optical sensors network causes negligible 0.3 dB power penalty.