Center Wavelength Of Fiber Bragg Grating Research Articles

SOC estimation of lithium battery based on the combination of electrical parameters and FBG non-electrical parameters and using NGO-BP model

Accurately estimating of the state of charge (SOC) of lithium batteries is of great significance for improving the service life and utilization efficiency of lithium batteries. In this paper, fiber Bragg grating (FBG) sensors are used to capture the offset of the FBG central wavelength caused by strain and temperature during the charging and discharging process of lithium batteries, and the current state of charge of lithium batteries is obtained through the combination of electrical parameters and FBG non-electrical parameters.A battery monitoring experimental system was established, and the comparison of wavelength offset collected by PDMS packaged FBG and bare FBG during the charging and discharging process of lithium batteries was discussed. The prediction results were compared by temperature compensating the central wavelength offset collected during the charging and discharging of lithium batteries, then introduced BP neural network and optimized NGO- BP neural network regression models for training to compare the prediction effects, the results of which point to the fact that in terms of regression model performance and improvement of FBG non-electrical parameters on model performance, the various indicators predicted by NGO-BP are stronger than those predicted by BP. After adding FBG non-electrical parameters, both the BP regression model and the NGO-BP regression model showed remarkable improvement in RMSE, MAE, and R2 compared to the purely electrical parameters, and the best prediction method for the NGO-BP non-purely electrical parameters, with RMSE of 0.0201 and MAE of 0.0154, which decreased by 77.94% and 73.12% respectively compared to the BP pure electrical parameter prediction method, and R2 of 0.9988, which increased by 5.88%, thus the joint accurate estimation of lithium battery SOC by electrical measurement characteristics and FBG non-electrical parameters is basically realized, which brings values for the design and development of battery management system.

Temperature self-compensating and high-sensitivity FBG inclination sensor based on the sliding mass principle

This paper presents a temperature self-compensating, high-sensitivity fiber Bragg grating (FBG) inclination sensor. A sliding mass block and a spring are selected as the inclination-force conversion components to induce strain in the substrate where the FBGs are located, resulting in a change in the center wavelength. Both sides of the sliding mass block are arranged with one FBG on each side to play the role of temperature self-compensating. By calculating the variation of the center wavelength of the two FBGs, the variation of the inclination angle can be obtained. The detailed mechanical construction and sensing mechanism of the sensor are introduced, and the theoretical sensitivity factor formula of the sensor is given. The calibration test and static characteristics analysis of the sensor are carried out with the inclination angle change as the parameter. The experimental results show that there is a good linear relationship between the inclination angle and the FBG central wavelength, and the sensor possesses good repeatability and creep resistance. The maximum angular sensitivity is 427.3 pm/°, avoiding the cross-sensitivity between temperature and strain of the FBG. The sensitivity of the sensor can be easily adjusted by replacing the sliding mass block and the spring.

A novel fast response and high precision water temperature sensor based on Fiber Bragg Grating

A novel fast response and high precision water temperature sensor scheme based on gallium alloy sensitivity enhanced Fiber Bragg Grating(FBG) is proposed and experimentally demonstrated. In order to achieve faster temperature response speed of the sensor, a fiber Bragg grating is encapsulated in a single-end sealed metal tube which is filled with liquid gallium alloy. The very high thermal conductivity of the liquid gallium alloy that is filled in the metal tube gives rise to an experimental sensitivity of 30 pm/℃. Thanks to accurate and optimal design of metal tube structure parameters, the sensor exhibits an excellent response speed of 43 ms/℃ in water. Very good linearity between center wavelength of FBG and temperature is also achieved in the experiment. The research result of this paper is especially useful for applications where rapid temperature response and high precision are required at the same time, such as ocean CTD(Conductivity Temperature Depth) measuring equipment, ocean hydrology and underwater submersible.

SOI-based 12 × 12 arrayed waveguide grating for fiber Bragg grating interrogation system

Fiber Bragg grating (FBG) interrogator is a scientific instrument that can indirectly monitor physical quantities such as temperature and pressure by detecting the center wavelength of FBG. The arrayed waveguide grating (AWG), one of the fundamental parts of the FBG interrogation system, is essential for driving the downsizing of the system and high-speed rate. In this paper, a 12-channel silicon on insulator based AWG with an average 3 dB bandwidth of 2.23 , insertion loss of less than 5 dB, and crosstalk of −16.64 dB is designed and fabricated for a photonic integrated FBG interrogation system. The wavelength resolution of the FBG interrogation system of this AWG is 8 , and the wavelength accuracy measured in the dynamic range of 0.8 is 10.59 . This AWG can be well used in FBG interrogation systems.

Quasi-distributed FBG interrogation based on coherent wavelength-to-time mapping using mode-locked laser and pseudo-random barcode

A microwave photonic demodulation scheme for multiplexing fiber Bragg grating (FBG) sensing system based on coherent wavelength-to-time (WTT) mapping is proposed and demonstrated experimentally in this paper. With the help of mode-locked laser (MLL) source and dispersion element, the broadband pseudo-random barcode obtained from fiber random grating can be mapped into time domain to fulfill high-speed interrogation for FBGs. The shifts of FBG center wavelength will be transformed into the variations of filtered pseudo-random barcode, and finally converted into the time location changes of the cross-correlation peaks with narrow full-width half-maximum (FWHM), which is helpful to realize high-accuracy and high-resolution FBG demodulation utilizing oscilloscope. The experiment results exhibit good demodulation linearity and a strain interrogation sensitivity of 0.0302 ns/με in cascaded sensing network with a repetition rate of 20 MHz, corresponding to a strain measurement resolution of 2.05 με. Besides, the impacts of system noises and light source line-shapes on the demodulation performance are studied numerically, and the relevant solutions are proposed and verified respectively.

A miniaturized, low-cost and portable fiber Bragg grating interrogation system for remote monitoring

A miniaturized, low-cost, 4-channel fiber Bragg grating (FBG) interrogation system for real-time remote monitoring is presented in this paper. A superluminescent light emitting diode (SLED) as the broadband light source combined with an interrogation module and an optical switch is applied in the system. The moving average method is employed to remove noise effects, and then Gaussian fitting method is used to realize the interrogation of FBG central wavelength with high precision. On software design, the WebSocket network protocol is introduced to establish communication between data processing core and webpages to achieve cross-platform remote access through the browser without user’s software installation. The proposed interrogation system not only displays the reflected spectrum and demodulated central wavelength in real time on the webpage, but also realizes the data storage and channel switch remotely. The interrogator for remote monitoring of FBG sensors proposed in this paper has been proved experimentally with the interrogation resolution 0.1 pm, the precision of 5 pm for the FBG central wavelength, interrogation stability up to ± 1.1 pm, and interrogation frequency of 4 kHz.

Automatic and rapid calibration method for temperature coefficient of fiber grating temperature sensor

Bare fiber Bragg grating (FBG) is packaged by thermal conductive materials and to be used as a temperature sensor. In the oil bath calibration of the temperature coefficient of the FBG temperature, it is difficult to accurately synchronize the single point temperature measurement and the simultaneously record FBG central wavelength using different devices. An automatic, fast and high precision calibration method for temperature coefficient of FBG temperature sensor is proposed. The experimental results show that the temperature coefficient obtained by the proposed method can accurately measure the temperature, and the calibration process is fast and avoids the error caused by manual recording and formula derivation. The system is suitable for rapid calibration of mass-produced FBG sensors.

Design of storage and management device of packaged FBG sensors based on RFID

In the application of fiber Bragg grating(FBG) sensor in structural condition monitoring, the reasonable layout scheme is designed according to its central wavelength. However, the paper label with FBG central wavelength information may be lost when FBG is used, therefore it is difficult to store and manage FBG sensors. This paper designs a storage device and its management system of packaged independent FBG sensor based on RFID technology. The oblique grid structure can store the FBG sensors with the same central wavelength. The RFID reader module is arranged on the top of the box-type device with multi-layer oblique grid. The packaged FBG sensors are stored, read and classified with the help of special software.

An optical fiber sensor based on polyimide coated fiber Bragg grating for measurement of relative humidity

Humidity is an important parameter in many industry fields and accurate humidity measurement is of great significance to improve production efficiency and ensure product quality. This paper presents a sensing model and scheme for utilizing thermoplastic polyimide (PI) coated fiber Bragg grating (FBG). The humidity sensitive PI layer was firstly prepared and coated on the FBG. The humidity calibration experiment was designed to verify the sensor performance based the saturated salt solution method. The experimental results show this FBG humidity sensor can work steady in the relative humidity (RH) condition ranging from 11%RH to 83% RH, with the sensitivity of the sensor less than 2 pm/% RH and measurement uncertainty of ±1% RH in the temperature range of 30 °C to 70 °C. In order to solve the problem that the PI-coated FBG is both sensitive to the humidity and temperature (cross sensitivity problem), a novel method of temperature compensation has been proposed. The method uses the character that the coefficients of expansion of the PI-coated layer for humidity and temperature are linearly superimposed and obtains the temperature compensation coefficient by linear interpolation of the function relationship between the measured temperature and the FBG central wavelength shift. The analysis of experimental data shows that within the temperature variation range of 20 °C, this temperature compensation method can effectively guarantee the average wavelength errors within 0.03 nm without reference grating. In this way, it can extend the FBG humidity measurement under environmental temperature up to 90 °C making it possible for application in the measurement the humidity in the high temperature environment.

Low-noise high-order Raman fiber laser pumped by random lasing.

Raman fiber lasers (RFLs) have been widely utilized in long-haul optical transmission systems as pump sources for distributed Raman amplification (DRA) to increase transmission distance and capacity. However, RFLs with relatively large temporal intensity fluctuations would deteriorate signal quality due to the transfer of relative intensity noise (RIN). In this Letter, a low-noise high-order RFL common cavity pumped by an ytterbium-doped random fiber laser (YRFL) is proposed and demonstrated for the first time, to the best of our knowledge. Stable 4th-order random Raman lasing operating at 1365 nm is generated with 8.9 W of output power, without use of a multi-stage master oscillation power amplification system. Thanks to the YRFL common-cavity pumping where a wavelength division multiplexer (WDM)-assisted fiber-loop mirror is used to generate stable 1090 nm ytterbium-doped random lasing and cascaded random Raman lasing simultaneously, the RIN of the 1365 nm RFL is suppressed as low as -120dB/Hz without any peak over a 0-100 MHz span. Furthermore, the output power and lasing wavelength of this RFL can be flexibly tuned by adjusting the laser diode pump power, high-reflectivity fiber Bragg grating center wavelength, and single-mode fiber length. Hence, such a low-noise high-order RFL paves a way for the development of novel tunable RFLs with stable temporal output, leading to potential replacement of conventional RFLs for DRA in long-haul optical transmission systems to achieve better performances.

Position Prediction of Soft Finger Driven by SMA Based on Fiber Bragg Grating Sensor

The purpose of this study is to analyze the deformation of soft finger driven by shape memory alloy (SMA) under fiber Bragg grating (FBG) sensor. Firstly, the structure and material properties of the finger, as well as the theoretical calculation of the shape of the finger by using the Cosserat elastic rod theory are introduced. Next, FBG sensors are arranged on the soft finger skeleton to analyze the theoretical relations such as FBG central wavelength and curvature, and the mathematical algorithm is used to realize the actual bending shape fitting of the soft finger. Finally, the flexural deformation experiment of the soft finger is carried out to validate the theoretical results based on Cosserat theory and ABAQUS simulation. The experimental results show the FBG sensor can effectively predict the deformation of the soft finger in real-time.

Strain and temperature sensor based on fiber Bragg grating cascaded bi-tapered four-core fiber Mach–Zehnder interferometer

A novel strain and temperature sensor based on the fiber Bragg grating (FBG) cascaded two-tapered four-core fiber (FCF) Mach–Zehnder interference (MZI) is proposed and fabricated. The two optical fiber tapers, acting respectively as a beam splitter and a coupler, are able to produce interference phenomena, so the high interference extinction ratio (above 20 dB) can be obtained. The attenuation peak at 1562 nm and the FBG center wavelength at 1550 nm in the transmission spectra are, respectively, selected to represent MZI and FBG as the monitoring wavelengths. The results indicate that the sensitivities of MZI to strain and temperature are −1.83 pm μϵ−1 and 46.93 pm C−1, respectively, and those of FBG to strain and temperature are 1.26 pm μϵ−1 and 10.58 pm C−1, respectively. Both the FBG and MZI exhibit insensitivity to the refractive index. The cascaded sensor has good linearity and is applied to measure the strain and temperature simultaneously.

Experimental study on a new FBG-based and Terfenol-D inclinometer for slope displacement monitoring

Slope displacement monitoring is an important means for early warning of landslide hazards, which is of great significance for preventing building damage and economic losses. This study describes a new inclinometer based on fiber Bragg grating (FBG) sensing technology and magnetostrictive effects. A series of FBG sensors were attached to the surface of the Terfenol-D to measure the magnetostrictive strain under different magnetic fields. Authors performed multiple sets of calibration experiments in the laboratory to obtain significant results. Furthermore, this study used the linear relationship between the center wavelength of FBG and the rotating angle of Terfenol-D to obtain the relative deflection angle between the rigid elements. The experiments show that the calibration results are in good agreement with the theoretical results. The developed inclinometer has good linearity, high tilt measurement sensitivity and high resolution.

The Analysis of FBG Central Wavelength Variation with Crack Propagation Based on a Self-Adaptive Multi-Peak Detection Algorithm.

We propose a peak seeking algorithm to extract the damage characteristic-variation of central wavelength to monitor the crack damage status in aluminum alloy plates using surface bonded fiber Bragg grating (FBG) sensors. The FBG sensors are sensitive to the uniform and non-uniform strain distribution along their longitudinal direction, and the effect appears in the power spectrum of the reflected light from the gauge section. In this paper, we propose a fast-self-adaptive multi-peak seeking algorithm to detect the central wavelength shifting of the FBG reflection spectrum with the crack propagation. The proposed peak searching algorithm results point to a significant improvement compared to other conventional methods. Then the central wavelength shifting is applied to explain the crack propagation behavior of the aluminum plates under quasi-static tensile test conditions. The different damages feature changing intervals which are associated with the crack position and the FBGs location, demonstrating that central wavelength shifting performs as an indicator to detect structural crack damage.

Raman-assisted phase sensitive amplifier using a fiber Bragg grating-based tunable phase shifter.

A low-loss Raman-assisted phase sensitive amplifier (PSA) with a ∼20 dB signal net gain is experimentally demonstrated. The amplitude and phase adjustment for PSA are achieved by using non-uniform Raman gain and a tunable fiber Bragg grating (FBG), respectively. The total component loss of the system is measured to be ∼8 dB. By tuning the FBG central wavelength, (1)an up to 5.6dB signal gain improvement is obtained; and (2)a ∼4 dB receiver sensitivity enhancement is observed for 20 and 25Gbaud quadrature phase shift keying signals and a 10Gbaud 16-quadrature amplitude modulation signal.

Fiber Bragg grating temperature calibration based on BP neural network

A novel method which applies BP neural network (BPNN) to temperature calibration of fiber Bragg grating (FBG) sensors is proposed and discussed. Processing and analysis of experimental data showed that this method fitted very well the complex relationship between the center wavelength of FBG and temperature which is approximately linear in room temperature whereas nonlinear in low temperature. The maximum absolute error and root mean squared error were respectively 0.9434 °C, 0.2102 °C in fitting and 0.8943 °C, 0.2081 °C in testing which verified the advantage of BPNN fitting compared with the previous polynomial fitting. The forecasting performance of BPNN was also satisfactory. The novel FBG temperature calibration method based on BPNN has considerable application prospect in FBG temperature measurement.

Temperature Compensation Fiber Bragg Grating Pressure Sensor Based on Plane Diaphragm

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

Real-time bonded area in-situ shear stress measurement of double butt strap joints based on FBG center wavelength analyses

One novel method which can achieve real-time bonded area in-situ shear stress measurement of double butt strap joints based on fiber Bragg grating (FBG) center wavelength analyses is proposed in this paper. Theory calculation model of this novel method is established to explain its feasibility. To verify the feasibility, testing experiment on one prototype is carried out. In the fabrication of the testing prototype of the double butt strap joint, four fiber Bragg gratings (FBGi, i=1, 2, 3, 4) are embedded in the bonded area. After data analyses, shear stress measurement sensitivity coefficients of FBGi (i=1, 2, 3, 4) show the same trend as theory calculation, and their values are 21.33pm/MPa, 21.95pm/MPa, 23.5pm/MPa and 21.2pm/MPa, respectively. All these data confirm the feasibility and correctness of the novel bonded area in-situ shear stress measurement method.

Research on one-piece structure target flow sensing technology based on fiber Bragg grating

In view of problems existing in the detection of the traditional hydraulic system, such as the large volume of sensor and the low measurement accuracy, a new one-piece target type flow sensor is designed and researched based on fiber Bragg grating (FBG). A compact structure is designed, which is convenient to be dismantled, processed, and installed, based on the analysis of the principle of FBG and the structure of target type flow sensor. The force of target put in fluid flow is turned into the FBG wavelength drift, with a corresponding relationship. The problem on the cross sensitivities of the temperature and strain is solved effectively by using double FBG symmetrically pasted on the both surfaces of the cantilever. The impact on the fluid state is analyzed through simulation in the software FLUENT, and the results show that the impact was smaller than that of the traditional structure. The results of experiments in the hydraulic system show that there is a good linear relationship between the change in the dual FBG central wavelength and mass loading on the target sheet has a good linear relationship, and the sensitivity is twice that of a single FBG sensitivity.

A wide‐range demodulation method for FBG sensor

ABSTRACTThe principle, structure design, and experimental setup of a fiber Bragg grating (FBG) sensor based on matching grating are introduced. The FBG sensor requires several fiber gratings to demodulate. This study proposes a simple signal detection method to demodulate the resonance wavelength shift of the FBG. Photodiodes convert the reflected light signal of every fiber grating into electrical signal. The reflected light signals are then collected by a computer through a data collection box. The physical quantity is reported in real time according to the calibrated data. This method has a wider range of demodulation and displays the drift of center wavelength of sensor FBG in real time. The temperature/strain cross‐sensitivity issue of FBG sensor is solved to some extent due to the same temperature drift of the same type of FBG. Experimental results show that the system has a wavelength measurement error of less than 0.009 nm, and the corresponding microstrain measurement error is less than 7.5 με. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2416–2419, 2016