FBG-based Sensors Research Articles

Etched FBG-Based Optical Fiber Sensor for Hg²+ Ion Detection in Aqueous Solution

Etched FBG-Based Optical Fiber Sensor for Hg²+ Ion Detection in Aqueous Solution

Design of an FBG-Based Tension Sensor With High Sensitivity and Linearity for Cable-Driven Continuum Robots

Design of an FBG-Based Tension Sensor With High Sensitivity and Linearity for Cable-Driven Continuum Robots

Design of a Fiber Temperature and Strain Sensor Model Using a Fiber Bragg Grating to Monitor Road Surface Conditions

In this paper, the types and principles of operation of fiber sensors based on fiber Bragg gratings (FBGs) are investigated. The influence of strain and temperature on the characteristics of FBGs is considered, and a method for the simultaneous measurement of these parameters is presented. Laboratory studies were carried out in the temperature range from +18 °C to +135 °C with an incremental step of 5 °C, with the actual temperature not deviating by more than ±0.5 °C. From the data obtained, the Bragg wavelength–temperature relationships were plotted, which showed a linear increase in wavelength with increasing temperature. This study shows that the use of two FBGs with a different sensitivity to temperature and strain allowed for the simultaneous measurement of both parameters. Numerical models created in the MATLAB R2022b environment confirmed the high accuracy and precision of the measurements. The FBG-based sensors demonstrated a robust performance in harsh environments, withstanding temperatures of up to 160 °C and high humidity, making them applicable in various industries and sciences. This work confirms that FBGs are a promising tool for accurate temperature and strain measurements, providing reliable results in harsh environments.

Enhancing data sparsity in spectral signals using wavelet decomposition for improved compression and storage efficiency

Wavelet decomposition (WD) is integrated into the Compressive Sensing (CS) model to enhance data sparsity. This approach aims to ensure efficiency and quality in the received data after compression and reconstruction processes. The proposed WD-CS model is developed for reflected spectra signals from Fiber Bragg Gratings-based extensometers, which were subjected to induced deflections simulating the underground soil movement. WD decomposes the input signal before compressive measurement, followed by transferring and storing the compressed data in the cloud. The spectral data were reconstructed using Orthogonal Matching Pursuit (OMP) followed by wavelet reconstruction. The impact of wavelet decomposition on the quality of compression and reconstruction is assessed and compared against that of the standard CS model. The findings indicate that the WD-CS model can improve data sparsity by a factor of three and compressibility by a factor of ten without degenerating the reconstructed data quality. The error in the Bragg wavelength shift of the reconstructed spectra is minimal extracted using Pseudo-high Resolution Interrogation (PHRI) method. The proposed WD-CS model is useful in improving data compression for FBG spectra as well as storage efficiency, which make it potentially applicable in FBG-based sensor networks for long-term structural health monitoring applications.

An FBG-based optical pressure sensor for the measurement of radial artery pulse pressure.

One of the diagnostic tool for clinical evaluation and disease diagnosis is a pulse waveform analysis. High fidelity radial artery pulse waveforms have been investigated in clinical research to compute central aortic pressure, which has been demonstrated to be predictive of cardiovascular diseases. The radial artery must be inspected from several angles in order to obtain the best pulse waveform for estimate and diagnosis. In this study, we present the design and experimental testing of an optical sensor based on Fiber Bragg Gratings (FBG). A 3D printed device along with the FBG is used to measure the radial artery pulses. The proposed sensor is used for the purpose of quantifying the radial artery pulse waveform across major pulse position point. The suggested optical sensing system can measure the pulse signal with good accuracy. The main characteristic parameters of the pulse can then be retrieved from the processed signal for their use in clinical applications. By conducting experiments under the direction of medical experts, the pulse signals are measured. In order to experimentally validate the sensor, we used it to detect the pulse waveforms at Guan position of the wrist's radial artery in accordance with the diagnostic standards. The findings show that combining optical technologies for physiological monitoring and radial artery pulse waveform monitoring using FBG in clinical applications are highly feasible.

Rapid prototyping of FBG-based optical sensors for vibration analysis of mechatronic systems

The detection and study of vibrations play a fundamental role in the monitoring and safety of engineering systems. This is especially true in the aerospace sector, where the operating environment is often hostile, and the constraints on weights and dimensions are very tight. For these reasons, the research and application of sensors based on optical signal transmission are becoming increasingly important. The opportunity to implement distributed measurements along a single optical fiber, the small size and weight, and the high resistance to electromagnetic interference make this technology an ideal candidate for the development of next-generation aerial platforms. In this paper, the authors focus on designing and developing a novel sensor that employs Fiber Bragg Grating (FBG) for vibration detection. Their primary aim is to explore the potential and constraints of this technology and build an initial prototype for testing purposes. Additionally, the project enabled the authors to experiment with rapid prototyping techniques that rely on 3D printing and additive manufacturing. The impact of various design choices, such as materials, geometry, and manufacturing, on the demonstrator sensitivity was explored by analysing the problem mathematically. A Matlab script was developed to estimate dimensions, weights, and dynamic performances, and modelling FEM was used for validation.

Development of a High-Precision and Large-Range FBG-Based Sensor Inspired by a Crank-Slider Mechanism for Wearable Measurement of Human Knee Joint Angles

Development of a High-Precision and Large-Range FBG-Based Sensor Inspired by a Crank-Slider Mechanism for Wearable Measurement of Human Knee Joint Angles

Experimental research of a structural health monitoring system concept based on fiber Bragg grating sensors on composite panels of an aircraft

In the dynamic realm of aviation, ensuring the structural integrity of aircraft stands as an imperative pillar of safety and operational efficiency. Amidst this landscape, the advent of Fiber Bragg Grating (FBG) sensing technology has propelled structural health monitoring (SHM) into a new era of precision and reliability. This paper embarks on an exploration of SHM in aviation, using the transformative capabilities of FBG sensing. The primary objective was to evaluate the sensitivity of FBG-based sensors to static and dynamic loads as well as the response to defects formed upon fracture. The study involves fifteen experiments with FBG setups on a composite panel. Using interrogators, the distortions in optical signals were obtained and recalculated to provide data on deformations. Based on the results, FBG sensing technology proved to be sensitive to the mentioned load types, outputting consistent data.

High-precision FBG-based sensor for soil settlement monitoring: A comparative study with magnetic settlement gauges and PIV technique

The primary objective of layered settlement monitoring is to detect subsidence issues in soil or foundational structures, in order to implement appropriate measures for ensuring the safety and stability of engineering projects. Conventional monitoring techniques have problems such as errors in manual readings, high costs, susceptibility to interference, and low levels of automation. A layered soil settlement sensor based on fiber Bragg grating (FBG) technology is proposed in this study. This sensor utilizes an equal-strength beam as an "intermediate bridge" to make the FBG sensor respond. The sensor is prepared by the laboratory's 3D fused deposition modelling (FDM) and calibrated by applying displacement loads through a fine-tuning platform. The sensitivity coefficient is 0.068 nm/mm, and the correlation coefficient exceeds 0.99. Finally, the sensor exhibited high precision when compared to measurements obtained from magnetic settlement gauges and particle image velocimetry (PIV). The discrepancies between the measurement outcomes of the sensor and the actual values of soil settlement does not exceed 3.33%.

Towards FBG-Based Shape Sensing and Sensor Drift for a Steerable Needle

Continuum manipulators contribute to promising improvements of minimally invasive surgical procedures due to their compliance, small size, and ability to navigate anatomical pathways. Feedback of the shape of such robots within the body is currently being researched through the use of fiber Bragg grating (FBG) sensors. As the size of the robot is reduced, placement of the sensors becomes increasingly challenging, often relying on glues and epoxies. In this article, a triplet of FBG fibers is used for shape sensing of a tendon driven continuum joint. Tests are performed to show the accuracy of reconstruction using this sensor both alone and incorporated in a tendon-driven continuum joint. A repeatable sensor drift was observed during prolonged deflection which caused an increase in error of up to 0.218 mm over a 10-min period. Results showed the effect of the repeated and sustained deflection on shape reconstruction under various deflection conditions and temperatures.

FBG-based three-dimensional micro-force sensor with axial force sensitivity-enhancing and temperature compensation for micro-forceps.

During retinal microsurgery, excessive interaction force between surgical instruments and intraocular tissue can cause serious accidents such as tissue injury, irreversible retinal damage, and even vision loss. It is essential to accurately sense the micro tool-tissue interaction force, especially for the Ophthalmic Microsurgery Robot. In this study, a fiber Bragg grating (FBG) three-dimensional (3-D) micro-force sensor for micro-forceps is proposed, which is integrated with the drive module as an end-effector and can be conveniently mounted onto the ophthalmic surgical robot. An innovative axial force sensitivity-enhancing structure is proposed based on the principles of flexure-hinge and flexible levers to overcome the low sensitivity of axial force measurement. A dual-grating temperature compensation method is adopted for axial force measurement, which considers the differential temperature sensitivity of the two FBGs. Three FBGs are arranged along the circumference of the guide tube in this study to measure transverse forces and compensate for effects caused by changes in temperature. The experimental results demonstrate that the micro-forceps designed in this study achieved a resolution of 0.13 mN for transverse force and 0.30 mN for axial force. The temperature compensation experiments show that the 3-D micro-force sensor can simultaneously compensate for temperature effects in axial and transverse force measurement.

Experimental development and evaluation of a fiber bragg grating-based outside air temperature sensor for aircraft applications

This study presents the development and rigorous evaluation of a Fiber Bragg Grating (FBG)-based Outside Air Temperature (OAT) sensor designed for aircraft applications. Employing a Design of Experiments (DoE) approach, the research optimized the sensor's performance for reliability, accuracy, and durability in aviation environments. Experimental assessment covered detailed installation of the FBG sensor on an aircraft, considering influential parameters such as outside dimensions and varying temperature. The OAT sensor's design focused on robustness and precision for accurate real-time temperature recording, vital for operational efficiency and safety. Extensive statistical analysis assessed the sensor's performance under differing conditions, providing valuable insights into operational capabilities and overall efficacy. Thermo-climatic chamber tests simulated extreme environmental conditions to validate the sensor's durability and function under potential aircraft operational scenarios. This research enhances understanding of FBG-based OAT sensors for aircraft applications, demonstrating their superior robustness and performance capabilities, thereby contributing to aviation safety, operational efficiency, and data precision.© 2017 Elsevier Inc. All rights reserved.

Fiber-Bragg-Grating-Based Sensor System to Measure Battery State of Charge Based on a Machine Learning Model

Real-time monitoring of the state of charge (SOC) of the batteries used in a wide variety of applications is becoming increasingly important, especially given the impetus by the current targets towards “net-zero”. In this research, an advanced approach was used involving fiber Bragg grating (FBG)-based sensors that were developed and implemented for the measurement of the key parameters required to ensure optimum battery performance. In this work, one of the biggest challenges to assess (and then map) the data from the sensor system developed is tackled in order to better understand the key parameters of the battery in an efficient and improved way. It is well known that the relationship between the changes in the resonance wavelength of the FBGs used in the sensor system, arising due to change in the electrical parameters of the battery, is complex and dependent on several different factors. In this work, this effect was evaluated by coupling the sensor data to a data-driven regression model approach that was developed for the measurement of the SOC of the batteries used, and this was obtained directly and conveniently from the FBG data. In this comprehensive study, FBG-based sensors were fabricated and then installed onto the battery, which then was subjected to a range of charging–discharging cycles, following which the electrical parameters of the battery were estimated from recorded data using a black-box machine learning (ML) model. Data-driven regression algorithms were employed for the training of the black-box model. The efficiency of the estimation of the SOC of the battery from the FBG-based sensor data was found to be high, at 99.62% (R2 values of Estimated SOC and True SOC line), creating a very satisfactory result for this key measurement. Thus, the work shows the robustness of the FBG-based sensor system combined with the neural network algorithm as an effective way to evaluate the electrical parameters of the battery, which is particularly important, as no physical/electrochemical/electrical model of the system is thus required.

FBG-based 3D shape sensor based on spun multi-core fibre for continuum surgical robots

FBG-based 3D shape sensor based on spun multi-core fibre for continuum surgical robots

Design and investigation of a novel vector displacement sensor using fiber Bragg grating technology

This paper presents a novel fiber Bragg grating (FBG)-based displacement sensor with simple construction for vector deformation monitoring of slope surface. The interesting structure design and sensing principle of determining the displacement direction and amplitude simultaneously are reported. Calibration tests of six different auxiliary structures (namely core sensing elements) of the sensor are reported, which demonstrates that they are characterized by a superb linearity with an R2 of over 0.998, large measurement range of 140 mm, high sensitivity of 4.362 pm/mm, maximum hysteresis error of 3.25% and maximum repeatability error of 6.62%, respectively. A simulated rock slope test of the sensor is conducted to investigate the performance for determining the progressive sliding process of sliding mass. Additionally, a homogeneous soil slope model test is further conducted and the vector deformation of slope surface is accurately captured by three proposed FBG-based displacement sensors. This capability in identifying two-dimensional displacement can provide a bright application prospect in intelligent monitoring field.

Investigation of FBG Linear/Angular Acceleration Sensor for Novel Type Inertial Measurement

A novel inertial measurement unit (IMU) was proposed to measure the three-axis linear/angular acceleration of a body using six fiber Bragg grating (FBG) optical fiber acceleration sensors sharing the same rotational center. The six acceleration sensors were shown to accurately distinguish between movements in different directions using a vibration generator and rotary motor/encoder device. The results also indicated that the measurement range of the FBG linear acceleration sensor was ±14 g, its average sensitivity was approximately 229.4 pm/g, and its nonlinearity was under 0.05%. Furthermore, the average sensitivity and nonlinearity of the FBG angular acceleration sensor were 21°/s²/pm and 0.23%, respectively. When measuring linear and angular acceleration, the cross-axis sensitivity of the IMU was within 2.0%. The measurement accuracy of the roll and pitch angle during 360° rotation as well as that of the yaw angle during 720° rotation were both in the range of 0.54 to 1.31%. Most of results indicated that the FBG-based IMU sensor was within the performance specifications of an equivalent conventional IMU sensor. Thus, the concept underlying the proposed sensor can be confidently used as a basis to develop a high-precision IMU sensor that is unaffected by electromagnetic interference.

Strain FBG-Based Sensor for Detecting Fence Intruders Using Machine Learning and Adaptive Thresholding.

This paper demonstrates an intruder detection system using a strain-based optical fiber Bragg grating (FBG), machine learning (ML), and adaptive thresholding to classify the intruder as no intruder, intruder, or wind at low levels of signal-to-noise ratio. We demonstrate the intruder detection system using a portion of a real fence manufactured and installed around one of the engineering college's gardens at King Saud University. The experimental results show that adaptive thresholding can help improve the performance of machine learning classifiers, such as linear discriminant analysis (LDA) or logistic regression algorithms in identifying an intruder's existence at low optical signal-to-noise ratio (OSNR) scenarios. The proposed method can achieve an average accuracy of 99.17% when the OSNR level is <0.5 dB.

Fiber Bragg grating-based optical filters for high-resolution sensing: A comprehensive analysis

In-fiber Bragg grating filters continue to proliferate, and their applications expand with the rapid advancement of fiber optic component fabrication techniques. Mathematical models for the realisation, characterization, and simulation of fiber Bragg gratings (FBGs) are required to design gratings for various purposes. In this article, a review of the various methodologies is provided. The principles of FBG and the development of FBG-based sensors for temperature, pressure, liquid level, strain, and refractive index sensing in diverse applications have been discussed. The operating concept and performance of cavity structures based on FBG have been investigated. Different sensing architectures with high sensitivity and resolution are presented, including FBG encased in a ring configuration. The basic interrogation techniques are also discussed.

Optical strain sensor with dual fibre Bragg grating topology

The paper presents the design, operation, and proof of principle realisation and validation of a relatively cheap fibre optic strain sensor based on two fibre Bragg grating (FBG) elements with different spectral responses. Its performance is compared with the measurement capabilities of a FBG-based sensor that uses an optical interrogator.

Assessing operational performance in industrial billet casting using an instrumented mould

ABSTRACT In the present study, the operational characteristics of an industrial billet caster were investigated. Two billet moulds were instrumented with Fibre Bragg Grating (FBG)-based temperature sensors and run for their full lives of 320 h each under normal plant conditions doing open casting with oil lubrication. The heat fluxes and temperatures of the mould wall were used to study the peritectic nature of the grades cast. The data from the moulds were also used to understand the main resistances to heat transfer by comparing the variation in mould wall temperatures to the variation in liquid steel temperature through a cast. The impact of mould life on the heat transfer through the mould was also studied by comparing data of similar casting conditions over the whole life of the mould. The instrumented moulds were also used to study sticker breakouts. The classical breakout signatures were obtained in the temperature profiles in the breakout events. It was found that the hot spot associated with the temperature peak was moving down at a speed of around 0.7–0.75 times the casting speed. The usefulness of FBG-based temperature sensors for practical billet caster operations has been shown.