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Fiber Bragg Gratings for Health Monitoring: from Civil Engineering to Human Body

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A special issue of Sensors (ISSN 1424-8220). This special issue belongs to the section "Physical Sensors".

Deadline for manuscript submissions: closed (20 April 2023) | Viewed by 13167

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Dr. Daniela Lo Presti

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Unit of Measurements and Biomedical Instrumentation, Department of Engineering, Università Campus Bio-Medico di Roma, Via Alvaro del Portillo, 21, 00128 Rome, Italy
Interests: Fiber Bragg gratings; measuring systems development and assessment; wearables for health monitoring; physiological monitoring; joint movements detections
Special Issues, Collections and Topics in MDPI journals

Dr. Cátia Leitão

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i3N, Department of Physics, University of Aveiro, Aveiro, Portugal
Interests: optical fiber sensors; biosensors; optical biosensors; physiological monitoring; fiber bragg gratings; optical fibers technology
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Dr. Michele Arturo Caponero

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Photonics Micro- and Nano-structures Laboratory, ENEA Research Center of Frascati, Via Enrico Fermi 45, 0044 Frascati (Rome), Italy
Interests: optical fiber sensors for civil engineering, biomedical, and high energy physics applications
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Fiber Bragg Gratings (FBGs) are reliable sensing solutions for health monitoring in a variety of fields, from civil engineering to biomedical applications. Although these terms seem to address very different realities, they both regard structures and systems (i.e., constructed environment and human body) that degrade with ageing. In both fields, preventive measures should be applied to identify early signs of damage or disease, launching alarms by the monitoring procedures.

Among numerous sensing technologies, FBGs with their unique properties of miniaturized size, light weight, immunity to electromagnetic interferences, long-term stability, and intrinsic compliance with ATEX and medical devices directives are particularly suitable for monitoring health conditions of civil infrastructures (e.g., structural deterioration, damages, and environmental parameters) and human bodies (e.g., changes in physiological status and body movement).

This Special Issue aims to advance the state of the art in civil engineering and biomedical applications with original research contributions focusing on the development and assessment of new FBG-based sensing solutions for health monitoring. These innovative systems will improve the life expectancy of civil infrastructures and human systems by detecting abnormal health states and damages at an early stage and giving assistance, maintenance, and rehabilitation advice.

Dr. Daniela Lo Presti
Dr. Cátia Leitão
Dr. Michele Arturo Caponero
Guest Editors

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Keywords

Structural health monitoring
Wearables for health monitoring
Measuring systems for human joint movement detection
Wearable sensors for physiological monitoring
Biosensors
Smart systems for environmental monitoring
Health data acquisition and analysis
Sensing technologies for damage detection and assessment
Measuring systems development and assessment

Published Papers (6 papers)

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Research

11 pages, 2435 KiB

Open AccessCommunication

Pretreatment of Ultra-Weak Fiber Bragg Grating Hydrophone Array Based on Cubic Spline Interpolation Using Intensity Compensation

by Yandong Pang, Hanjie Liu, Ciming Zhou, Junbin Huang, Hongcan Gu and Zhiqiang Zhang

Sensors 2022, 22(18), 6814; https://doi.org/10.3390/s22186814 - 08 Sep 2022

Cited by 5 | Viewed by 1379

Abstract

The demodulation algorithm based on 3 × 3 coupler in a fiber-optic hydrophone array has gained extensive attention in recent years. The traditional method uses a circulator to construct the normal path-match interferometry; however, the problem of increasing the asymmetry of the three-way signal to be demodulated is easily overlooked. To provide a solution, we report a pretreatment method for hydrophone array based on 3 × 3 coupler demodulation. We use cubic spline interpolation to perform nonlinear fitting to the reflected pulse train and calculate the peak-to-peak values of the single pulse to determine the light intensity compensation coefficient of the interference signal, so as to demodulate the corrected three-way interference signal. For experimental verification, ultra-weak fiber Bragg gratings (uwFBGs) with reflectivity of −50 dB are applied to construct a hydrophone array with 800 sensors, and a vibratory liquid column method is set up to generate a low-frequency hydroacoustic signal. Compared to the traditional demodulation algorithm based on a 3 × 3 coupler, the pretreatment method can improve the consistency of interference signals. The Lissajous figures show that cubic spline interpolation can improve the accuracy of monopulse peak seeking results by about 1 dB, and intensity compensation can further lead to a much lower noise density level for the interference pulse amplitude—specifically, more than 7 dB at 5~50 Hz—and the signal-to-noise ratio is improved by approximately 10 dB at 10 Hz. The distinct advantages of the proposed pretreatment method make it an excellent candidate for a hydrophone array system based on path-match interferometry. Full article

(This article belongs to the Special Issue Fiber Bragg Gratings for Health Monitoring: from Civil Engineering to Human Body)

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14 pages, 5029 KiB

Open AccessArticle

Looseness Identification of Track Fasteners Based on Ultra-Weak FBG Sensing Technology and Convolutional Autoencoder Network

by Sheng Li, Liang Jin, Jinpeng Jiang, Honghai Wang, Qiuming Nan and Lizhi Sun

Sensors 2022, 22(15), 5653; https://doi.org/10.3390/s22155653 - 28 Jul 2022

Cited by 2 | Viewed by 1378

Abstract

Changes in the geological environment and track wear, and deterioration of train bogies may lead to the looseness of subway fasteners. Identifying loose fasteners randomly distributed along the subway line is of great significance to avoid train derailment. This paper presents a convolutional autoencoder (CAE) network-based method for identifying fastener loosening features from the distributed vibration responses of track beds detected by an ultra-weak fiber Bragg grating sensing array. For an actual subway tunnel monitoring system, a field experiment used to collect the samples of fastener looseness was designed and implemented, where a crowbar was used to loosen or tighten three pairs of fasteners symmetrical on both sides of the track within the common track bed area and the moving load of a rail inspection vehicle was employed to generate 12 groups of distributed vibration signals of the track bed. The original vibration signals obtained from the on-site test were converted into two-dimensional images through the pseudo-Hilbert scan to facilitate the proposed two-stage CAE network with acceptable capabilities in feature extraction and recognition. The performance of the proposed methodology was quantified by accuracy, precision, recall, and F1-score, and displayed intuitively by t-distributed stochastic neighbor embedding (t-SNE). The raster scan and the Hilbert scan were selected to compare with the pseudo-Hilbert scan under a similar CAE network architecture. The identification performance results represented by the four quantification indicators (accuracy, precision, recall, and F1-score) based on the scan strategy in this paper were at least 23.8%, 9.5%, 20.0%, and 21.1% higher than those of the two common scan methods. As well as that, the clustering visualization by t-SNE further verified that the proposed approach had a stronger ability in distinguishing the feature of fastener looseness. Full article

(This article belongs to the Special Issue Fiber Bragg Gratings for Health Monitoring: from Civil Engineering to Human Body)

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12 pages, 3210 KiB

Open AccessArticle

Generalized Cross-Correlation Strain Demodulation Method Based on Local Similar Spectral Scanning

by Yuqi Tian, Jiwen Cui, Zaibin Xu and Jiubin Tan

Sensors 2022, 22(14), 5378; https://doi.org/10.3390/s22145378 - 19 Jul 2022

Cited by 3 | Viewed by 1529

Abstract

Optical fiber measurement technology is widely used in the strength testing of buildings, the health testing of industrial equipment, and the minimally invasive surgery of modern medical treatment due to its characteristics of free calibration, high precision, and small size. This paper presents an algorithm that can improve the range and stability of strain measurements in order to solve the problems of the small range and measurement failure of optical fiber strain sensors based on optical frequency-domain reflectometry (OFDR). Firstly, a Rayleigh scattering model based on the refractive index perturbation of an optical fiber is proposed to study the characteristics of Rayleigh scattering and to guide the strain demodulation algorithm based on the spectral shift. Secondly, a local similar scanning method that can maintain a high similarity by monitoring local Rayleigh scattering signals (LSs) before and after strain is proposed. Thirdly, a generalized cross-correlation algorithm is proposed to detect spectral offset, solving the problem of demodulation failure in the case of a Rayleigh scattering signal with a low signal-to-noise ratio. Experiments show that the proposed method still has high stability when the spatial resolution is 3 mm. The measurement precision is 6.2 με, which proves that the multi-peaks or pseudo-peaks of the traditional algorithm in the case of a large strain, the high spatial resolution, and the poor signal-to-noise ratio are solved, and the stability of the strain measurement process is improved. Full article

(This article belongs to the Special Issue Fiber Bragg Gratings for Health Monitoring: from Civil Engineering to Human Body)

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15 pages, 6080 KiB

Open AccessArticle

Application of FBG Sensor to Safety Monitoring of Mine Shaft Lining Structure

by Kun Hu, Zhishu Yao, Yanshuang Wu, Yongjie Xu, Xiaojian Wang and Chen Wang

Sensors 2022, 22(13), 4838; https://doi.org/10.3390/s22134838 - 26 Jun 2022

Cited by 5 | Viewed by 1547

Abstract

The use of fiber Bragg grating (FBG) sensors is proposed to solve the technical problem of poor sensor stability in the long-term safety monitoring of shaft lining structures. The auxiliary shaft of the Zhuxianzhuang coal mine was considered as the engineering background, and a test system implementing FBG sensors was established to monitor the long-term safety of the shaft lining structure. Indoor simulation testing revealed that the coefficient of determination (r²) between the test curves of the FBG sensor and the resistance strain gauge is greater than 0.99 in both the transverse and vertical strains. Therefore, the FBG sensor and resistance strain gauge test values are similar, and the error is small. The early warning value was obtained by calculation, according to the specific engineering geological conditions and shaft lining structure. The monitoring data obtained for the shaft lining at three test levels over more than three years reveal that the measured vertical strain value is less than the warning value, indicating that the shaft lining structure is currently in a safe state. The analysis of the monitoring data reveals that the vertical strain increment caused by the vertical additional force is approximately 0.0752 με/d. As the mine drainage progresses, the increasing vertical additional force acting on the shaft lining will compromise the safety of the shaft lining structure. Therefore, the monitoring must be enhanced to facilitate decision-making for safe shaft operation. Full article

(This article belongs to the Special Issue Fiber Bragg Gratings for Health Monitoring: from Civil Engineering to Human Body)

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17 pages, 6193 KiB

Open AccessArticle

A Wearable System Composed of FBG-Based Soft Sensors for Trunk Compensatory Movements Detection in Post-Stroke Hemiplegic Patients

by Daniela Lo Presti, Martina Zaltieri, Marco Bravi, Michelangelo Morrone, Michele Arturo Caponero, Emiliano Schena, Silvia Sterzi and Carlo Massaroni

Sensors 2022, 22(4), 1386; https://doi.org/10.3390/s22041386 - 11 Feb 2022

Cited by 8 | Viewed by 2051

Abstract

In this study, a novel wearable system for the identification of compensatory trunk movements (CTMs) in post-stroke hemiplegic patients is presented. The device is composed of seven soft sensing elements (SSEs) based on fiber Bragg grating (FBG) technology. Each SSE consists of a single FBG encapsulated into a flexible matrix to enhance the sensor’s robustness and improve its compliance with the human body. The FBG’s small size, light weight, multiplexing capability, and biocompatibility make the proposed wearable system suitable for multi-point measurements without any movement restriction. Firstly, its manufacturing process is presented, together with the SSEs’ mechanical characterization to strain. Results of the metrological characterization showed a linear response of each SSE in the operating range. Then, the feasibility assessment of the proposed system is described. In particular, the device’s capability of detecting CTMs was assessed on 10 healthy volunteers and eight hemiplegic patients while performing three tasks which are representative of typical everyday life actions. The wearable system showed good potential in detecting CTMs. This promising result may foster the use of the proposed device on post-stroke patients, aiming at assessing the proper course of the rehabilitation process both in clinical and domestic settings. Moreover, its use may aid in defining tailored strategies to improve post-stoke patients’ motor recovery and quality of life. Full article

(This article belongs to the Special Issue Fiber Bragg Gratings for Health Monitoring: from Civil Engineering to Human Body)

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16 pages, 3713 KiB

Open AccessArticle

Plant Wearable Sensors Based on FBG Technology for Growth and Microclimate Monitoring

by Daniela Lo Presti, Sara Cimini, Carlo Massaroni, Rosaria D’Amato, Michele Arturo Caponero, Laura De Gara and Emiliano Schena

Sensors 2021, 21(19), 6327; https://doi.org/10.3390/s21196327 - 22 Sep 2021

Cited by 21 | Viewed by 4013

Abstract

Plants are primary resources for oxygen and foods whose production is fundamental for our life. However, diseases and pests may interfere with plant growth and cause a significant reduction of both the quality and quantity of agriculture products. Increasing agricultural productivity is crucial for poverty reduction and food security improvements. For this reason, the 2030 Agenda for Sustainable Development gives a central role to agriculture by promoting a strong technological innovation for advancing sustainable practices at the plant level. To accomplish this aim, recently, wearable sensors and flexible electronics have been extended from humans to plants for measuring elongation, microclimate, and stressing factors that may affect the plant’s healthy growth. Unexpectedly, fiber Bragg gratings (FBGs), which are very popular in health monitoring applications ranging from civil infrastructures to the human body, are still overlooked for the agriculture sector. In this work, for the first time, plant wearables based on FBG technology are proposed for the continuous and simultaneous monitoring of plant growth and environmental parameters (i.e., temperature and humidity) in real settings. The promising results demonstrated the feasibility of FBG-based sensors to work in real situations by holding the promise to advance continuous and accurate plant health growth monitoring techniques. Full article

(This article belongs to the Special Issue Fiber Bragg Gratings for Health Monitoring: from Civil Engineering to Human Body)

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Fiber Bragg Gratings for Health Monitoring: from Civil Engineering to Human Body

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