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Special Issue "Fiber Bragg Grating Based Sensors and Systems"

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

Deadline for manuscript submissions: closed (30 September 2020).

Special Issue Editor

Prof. Dr. Oleg Morozov
E-Mail Website1 Website2
Guest Editor
Department of Radiophotonics and Microwave Technologies, Kazan National Research Technical University named after A.N. Tupolev-KAI, 10, Karl Marx st., 420111 Kazan, Tatarstan, Russia
Interests: microwave photonics; fiber optic sensors; fiber bragg gratings; application of electro-optical modulators; lidars; transfer of optical technologies in microwave range; microwave resonant sensors; microwave high- and low-intensity technologies; double-frequency methods in sensors and telecommunications
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Special Issue Information

Dear Colleagues,

Today, no one doubts that fiber Bragg gratings (FBGs) have become the most used tool for measuring various physical parameters, the structural integrity of engineering systems, and biological activity of living systems. Classical approaches to measurements based on temperature and mechanical deformations and changes in the refractive index of the surrounding sensor environment are actively developing. New measurement principles are emerging based, for example, on physical changes in the length of the grating. The search for ways to simplify and reduce the price of FBG interrogation systems on the one hand, and improve their metrological characteristics on the other, is ongoing. One of the winning directions of these studies is the transition to microwave photonics measurement systems, which have been developed on the basis of schemes of optoelectronic generators, frequency mapping, probing using multifrequency laser radiation with difference frequencies lying in the microwave range, and comb generators. The second promising direction is the development and creation of addressable FBGs, the use of which makes it possible to increase the efficiency of processing measurement data and provides the ability to visualize quasidistributed sensors and map their readings.

 Bearing this in mind, this issue is dedicated, but not limited, to the following issues:

  • Modeling and simulation of FBGs;
  • Fabrication of FBGs;
  • Multiparameter FBG sensors;
  • Addressable FBGs;
  • Nonsymmetrical FBGs;
  • Special type of FBG sensors with one or multiplicative phase shifts;
  • Sensors on chirped, tilted, superstructured, etc. FBGs;
  • Нigh-speed optoelectronic interrogation methods;
  • Microwave photonics interrogation methods;
  • FBG sensors in dynamic measurements;
  • FBG sensors in quasistatic measurements;
  • FBGs in optical fibers of different classes;
  • FBG sensors in DTS, DTSS, and DAS systems;
  • FBG sensor on-board applications;
  • FBG sensors in medicine and living systems monitoring;
  • Biological FBG sensors;
  • Integration and packaging of FBGs in technical and living systems;
  • Application of FPI sensors, based on FBGs;
  • Dual nature of FBGs as elements of sensor and telecommunication systems;
  • Transfer of FBG characterization methods on different optical resonance structures;
  • Transfer of FBG principles in microwave range.

We hope that the works published in this Special Issue will confirm the fundamental importance of the FBG invention and their comprehensive application in all areas of human activity, as well as open up new prospects for the creation and application of FBGs as quanta of various cyberphysical systems.

Prof. Dr. Oleg G. Morozov
Guest Editor

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Published Papers (12 papers)

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Open AccessArticle
Evaluation of Strain Transition Properties between Cast-In Fibre Bragg Gratings and Cast Aluminium during Uniaxial Straining
Sensors 2020, 20(21), 6276; https://doi.org/10.3390/s20216276 - 04 Nov 2020
Viewed by 420
Abstract
Current testing methods are capable of measuring strain near the surface on structural parts, for example by using strain gauges. However, stress peaks often occur within the material and can only be approximated. An alternative strain measurement incorporates fibre-optical strain sensors (Fiber Bragg [...] Read more.
Current testing methods are capable of measuring strain near the surface on structural parts, for example by using strain gauges. However, stress peaks often occur within the material and can only be approximated. An alternative strain measurement incorporates fibre-optical strain sensors (Fiber Bragg Gratings, FBG) which are able to determine strains within the material. The principle has already been verified by using embedded FBGs in tensile specimens. The transition area between fibre and aluminium, however, is not yet properly investigated. Therefore, strains in tensile specimens containing FBGs were measured by neutron diffraction in gauge volumes of two different sizes around the Bragg grating. As a result, it is possible to identify and decouple elastic and plastic strains affecting the FBGs and to transfer the findings into a fully descriptive FE-model of the strain transition area.We thus accomplished closing the gap between the external load and internal straining obtained from cast-in FBG and generating valuable information about the mechanisms within the strain transition area.It was found that the porosity within the casting has a significant impact on the stiffness of the tensile specimen, the generation of excess microscopic tensions and thus the formation of permanent plastic strains, which are well recognized by the FBG. The knowledge that FBG as internal strain sensors function just as well as common external strain sensors will now allow for the application of FBG in actual structural parts and measurements under real load conditions. In the future, applications for long-term monitoring of cast parts will also be enabled and are currently under development. Full article
(This article belongs to the Special Issue Fiber Bragg Grating Based Sensors and Systems)
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Open AccessArticle
Addressed Fiber Bragg Structures in Load-Sensing Wheel Hub Bearings
Sensors 2020, 20(21), 6191; https://doi.org/10.3390/s20216191 - 30 Oct 2020
Cited by 1 | Viewed by 608
Abstract
The work presents an approach to instrument the load-sensing bearings for automotive applications for estimation of the loads acting on the wheels. The system comprises fiber-optic sensors based on addressed fiber Bragg structures (AFBS) with two symmetrical phase shifts. A mathematical model for [...] Read more.
The work presents an approach to instrument the load-sensing bearings for automotive applications for estimation of the loads acting on the wheels. The system comprises fiber-optic sensors based on addressed fiber Bragg structures (AFBS) with two symmetrical phase shifts. A mathematical model for load–deformation relation is presented, and the AFBS interrogation principle is described. The simulation includes (i) modeling of vehicle dynamics in a split-mu braking test, during which the longitudinal wheel loads are obtained, (ii) the subsequent estimation of bearing outer ring deformation using a beam model with simply supported boundary conditions, (iii) the conversion of strain into central frequency shift of AFBS, and (iv) modeling of the beating signal at the photodetector. The simulation results show that the estimation error of the longitudinal wheel force from the strain data acquired from a single measurement point was 5.44% with a root-mean-square error of 113.64 N. A prototype load-sensing bearing was instrumented with a single AFBS sensor and mounted in a front right wheel hub of an experimental vehicle. The experimental setup demonstrated comparable results with the simulation during the braking test. The proposed system with load-sensing bearings is aimed at estimation of the loads acting on the wheels, which serve as input parameters for active safety systems, such as automatic braking, adaptive cruise control, or fully automated driving, in order to enhance their effectiveness and the safety of the vehicle. Full article
(This article belongs to the Special Issue Fiber Bragg Grating Based Sensors and Systems)
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Open AccessArticle
High Speed, Localized Multi-Point Strain Measurements on a Containment Vessel at 1.7 MHz Using Swept-Wavelength Laser-Interrogated Fiber Bragg Gratings
Sensors 2020, 20(20), 5935; https://doi.org/10.3390/s20205935 - 20 Oct 2020
Viewed by 527
Abstract
Dynamic elastic strain in ~1.8 and 1.0 m diameter containment vessels containing a high explosive detonation was measured using an array of fiber Bragg gratings. The all-optical method, called real-time localized strain measurement, recorded the strain for 10 ms after detonation with additional [...] Read more.
Dynamic elastic strain in ~1.8 and 1.0 m diameter containment vessels containing a high explosive detonation was measured using an array of fiber Bragg gratings. The all-optical method, called real-time localized strain measurement, recorded the strain for 10 ms after detonation with additional measurements being sequentially made at a rate of 1.7 MHz. A swept wavelength laser source provided the repetition rate necessary for such high-speed measurements while also providing enough signal strength and bandwidth to simultaneously measure 8 or more unique points on the vessel’s surface. The data presented here arethen compared with additional diagnostics consisting of a fast spectral interferometer and an optical backscatter reflectometer to show a comparison between the local and global changes in the vessel strain, both dynamically and statically to further characterize the performance of the localized strain measurement. The results are also compared with electrical resistive strain gauges and finite element analysis simulations. Full article
(This article belongs to the Special Issue Fiber Bragg Grating Based Sensors and Systems)
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Open AccessArticle
Generation of Vortex Optical Beams Based on Chiral Fiber-Optic Periodic Structures
Sensors 2020, 20(18), 5345; https://doi.org/10.3390/s20185345 - 18 Sep 2020
Viewed by 536
Abstract
In this paper, we consider the process of fiber vortex modes generation using chiral periodic structures that include both chiral optical fibers and chiral (vortex) fiber Bragg gratings (ChFBGs). A generalized theoretical model of the ChFBG is developed including an arbitrary function of [...] Read more.
In this paper, we consider the process of fiber vortex modes generation using chiral periodic structures that include both chiral optical fibers and chiral (vortex) fiber Bragg gratings (ChFBGs). A generalized theoretical model of the ChFBG is developed including an arbitrary function of apodization and chirping, which provides a way to calculate gratings that generate vortex modes with a given state for the required frequency band and reflection coefficient. In addition, a matrix method for describing the ChFBG is proposed, based on the mathematical apparatus of the coupled modes theory and scattering matrices. Simulation modeling of the fiber structures considered is carried out. Chiral optical fibers maintaining optical vortex propagation are also described. It is also proposed to use chiral fiber-optic periodic structures as sensors of physical fields (temperature, strain, etc.), which can be applied to address multi-sensor monitoring systems due to a unique address parameter—the orbital angular momentum of optical radiation. Full article
(This article belongs to the Special Issue Fiber Bragg Grating Based Sensors and Systems)
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Open AccessArticle
Dual Wavelength Differential Detection of Fiber Bragg Grating Sensors with a Pulsed DFB Laser
Sensors 2020, 20(17), 4766; https://doi.org/10.3390/s20174766 - 24 Aug 2020
Viewed by 528
Abstract
We show how dual wavelength differential detection can be used to measure fiber Bragg grating sensors using nanosecond pulses from a single DFB laser diode, by taking advantage of its dynamic chirp. This can be performed in two ways: by measuring the reflected [...] Read more.
We show how dual wavelength differential detection can be used to measure fiber Bragg grating sensors using nanosecond pulses from a single DFB laser diode, by taking advantage of its dynamic chirp. This can be performed in two ways: by measuring the reflected power from two separate pulses driven by two different currents, or by taking two delayed digitized samples within a single pulse. A prototype instrument using fast digitizing and processing with an FPGA is used to characterize the chirp, from which the performance can be optimized for both measurement schemes. Full article
(This article belongs to the Special Issue Fiber Bragg Grating Based Sensors and Systems)
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Open AccessArticle
Comparative Study of Damage Detection Methods Based on Long-Gauge FBG for Highway Bridges
Sensors 2020, 20(13), 3623; https://doi.org/10.3390/s20133623 - 28 Jun 2020
Cited by 2 | Viewed by 652
Abstract
Damage detection of highway bridges is a significant part of structural heath monitoring. Conventional accelerometers or strain gauges utilized for damage detection have many shortcomings, especially their monitoring gauge length being too short, which would result in poor damage detection results. Under this [...] Read more.
Damage detection of highway bridges is a significant part of structural heath monitoring. Conventional accelerometers or strain gauges utilized for damage detection have many shortcomings, especially their monitoring gauge length being too short, which would result in poor damage detection results. Under this circumstance, long-gauge FBG sensors as a novel optical sensor were developed to measure the macro-strain response of the structure. Based on this sensor, many derived damage detection methods were proposed. These methods exhibit various characteristics and have not been systematically compared. As a result, it is difficult to evaluate the state of the art and also leads to confusion for users to select. Therefore, a strict comparative study on three representative methods using long-gauge FBG was carried out. First, these methods’ theoretical backgrounds and formats were reformulated and unified for better comparison. Then, based on validated vehicle–bridge coupling simulation, these methods’ performances were tested through a series of parametric studies including various damage scenarios, vehicle types, speeds, road roughness and noise levels. The precision and reliability of three methods have been thoroughly studied and compared. Full article
(This article belongs to the Special Issue Fiber Bragg Grating Based Sensors and Systems)
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Open AccessEditor’s ChoiceArticle
Multi-Addressed Fiber Bragg Structures for Microwave-Photonic Sensor Systems
Sensors 2020, 20(9), 2693; https://doi.org/10.3390/s20092693 - 09 May 2020
Cited by 5 | Viewed by 1190
Abstract
The new theory and technique of Multi-Addressed Fiber Bragg Structure (MAFBS) usage in Microwave Photonics Sensor Systems (MPSS) is presented. This theory is the logical evolution of the theory of Addressed Fiber Bragg Structure (AFBS) usage as sensors in MPSS. The mathematical model [...] Read more.
The new theory and technique of Multi-Addressed Fiber Bragg Structure (MAFBS) usage in Microwave Photonics Sensor Systems (MPSS) is presented. This theory is the logical evolution of the theory of Addressed Fiber Bragg Structure (AFBS) usage as sensors in MPSS. The mathematical model of additive response from a single MAFBS is presented. The MAFBS is a special type of Fiber Bragg Gratings (FBG), the reflection spectrum of which has three (or more) narrow notches. The frequencies of narrow notches are located in the infrared range of electromagnetic spectrum, while differences between them are located in the microwave frequency range. All cross-differences between optical frequencies of single MAFBS are called the address frequencies set. When the additive optical response from a single MAFBS, passed through an optic filter with an oblique amplitude–frequency characteristic, is received on a photodetector, the complex electrical signal, which consists of all cross-frequency beatings of all optical frequencies, which are included in this optical signal, is taken at its output. This complex electrical signal at the photodetector’s output contains enough information to determine the central frequency shift of the MAFBS. The method of address frequencies analysis with the microwave-photonic measuring conversion method, which allows us to define the central frequency shift of a single MAFBS, is discussed in the work. Full article
(This article belongs to the Special Issue Fiber Bragg Grating Based Sensors and Systems)
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Open AccessArticle
On the Evaluation of a Coupled Sequential Approach for Rotorcraft Landing Simulation
Sensors 2020, 20(9), 2540; https://doi.org/10.3390/s20092540 - 29 Apr 2020
Cited by 3 | Viewed by 682
Abstract
Maximum loads acting on aircraft structures generally arise when the aircraft is undergoing some form of acceleration, such as during landing. Landing, especially when considering rotorcrafts, is thus crucial in determining the operational load spectrum, and accurate predictions on the actual health/load level [...] Read more.
Maximum loads acting on aircraft structures generally arise when the aircraft is undergoing some form of acceleration, such as during landing. Landing, especially when considering rotorcrafts, is thus crucial in determining the operational load spectrum, and accurate predictions on the actual health/load level of the rotorcraft structure cannot be achieved unless a database comprising the structural response in various landing conditions is available. An effective means to create a structural response database relies on the modeling and simulation of the items and phenomena of concern. The structural response to rotorcraft landing is an underrated topic in the open scientific literature, and tools for the landing event simulation are lacking. In the present work, a coupled sequential simulation strategy is proposed and experimentally verified. This approach divides the complex landing problem into two separate domains, namely a dynamic domain, which is ruled by a multibody model, and a structural domain, which relies on a finite element model (FEM). The dynamic analysis is performed first, calculating a set of intermediate parameters that are provided as input to the subsequent structural analysis. Two approaches are compared, using displacements and forces at specific airframe locations, respectively, as the link between the dynamic and structural domains. Full article
(This article belongs to the Special Issue Fiber Bragg Grating Based Sensors and Systems)
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Open AccessEditor’s ChoiceArticle
Wearable Hand Module and Real-Time Tracking Algorithms for Measuring Finger Joint Angles of Different Hand Sizes with High Accuracy Using FBG Strain Sensor
Sensors 2020, 20(7), 1921; https://doi.org/10.3390/s20071921 - 30 Mar 2020
Cited by 6 | Viewed by 1128
Abstract
This paper presents a wearable hand module which was made of five fiber Bragg grating (FBG) strain sensor and algorithms to achieve high accuracy even when worn on different hand sizes of users. For real-time calculation with high accuracy, FBG strain sensors move [...] Read more.
This paper presents a wearable hand module which was made of five fiber Bragg grating (FBG) strain sensor and algorithms to achieve high accuracy even when worn on different hand sizes of users. For real-time calculation with high accuracy, FBG strain sensors move continuously according to the size of the hand and the bending of the joint. Representatively, four algorithms were proposed; point strain (PTS), area summation (AREA), proportional summation (PS), and PS/interference (PS/I or PS/I_ α ). For more accurate and efficient assessments, 3D printed hand replica with different finger sizes was adopted and quantitative evaluations were performed for index~little fingers (77 to 117 mm) and thumb (68~78 mm). For index~little fingers, the optimized algorithms were PS and PS/I_ α . For thumb, the optimized algorithms were PS/I_ α and AREA. The average error angle of the wearable hand module was observed to be 0.47 ± 2.51° and mean absolute error (MAE) was achieved at 1.63 ± 1.97°. These results showed that more accurate hand modules than other glove modules applied to different hand sizes can be manufactured using FBG strain sensors which move continuously and algorithms for tracking this movable FBG sensors. Full article
(This article belongs to the Special Issue Fiber Bragg Grating Based Sensors and Systems)
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Open AccessArticle
Experimental Study on Glaze Icing Detection of 110 kV Composite Insulators Using Fiber Bragg Gratings
Sensors 2020, 20(7), 1834; https://doi.org/10.3390/s20071834 - 26 Mar 2020
Viewed by 680
Abstract
Icing detection of composite insulators is essential for the security and stability of power grids. As conventional methods have met difficulties in harsh weather, a 110 kV composite insulator with embedded Fiber Bragg Gratings (FBGs) was proposed for detecting glaze icing in this [...] Read more.
Icing detection of composite insulators is essential for the security and stability of power grids. As conventional methods have met difficulties in harsh weather, a 110 kV composite insulator with embedded Fiber Bragg Gratings (FBGs) was proposed for detecting glaze icing in this paper. FBG temperature compensation sensors in ceramic tubes were adopted for simultaneous measurement of icicle loads and temperature. Then, temperature calibration experiments and simulated icicle load experiments were carried out to obtain temperature and icicle load characteristics of FBGs. The results showed that temperature sensitivities of FBG strain sensors and FBG temperature compensation sensors were 18.16 pm/°C, and 13.18 pm/°C, respectively. Besides, wavelength shifts were linearly related to icicle loads within the polar angle range of −60° to 60°, and the load coefficient of FBG facing the icicle was -34.6 pm/N. In addition, the wavelength shift generated by several icicles was equal to the sum of wavelength shifts generated by each icicle within the polar angle range of −15° to 15°. Finally, icicles can cause wavelength shifts of FBGs within a big shed spacing. The paper provides a novel icing detection technology for composite insulators in transmission lines. Full article
(This article belongs to the Special Issue Fiber Bragg Grating Based Sensors and Systems)
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Open AccessLetter
Optical Designs with Curved Detectors for Fiber Bragg Grating Interrogation Monitors
Sensors 2021, 21(1), 34; https://doi.org/10.3390/s21010034 - 23 Dec 2020
Viewed by 440
Abstract
In this paper, we evaluate the application of curved detectors and freeform optics technologies for fiber Bragg gratings (FBGs) interrogation monitors design. It is shown that, in a high-dispersion spectrograph scheme, the camera part operates in special conditions, which result in a field [...] Read more.
In this paper, we evaluate the application of curved detectors and freeform optics technologies for fiber Bragg gratings (FBGs) interrogation monitors design. It is shown that, in a high-dispersion spectrograph scheme, the camera part operates in special conditions, which result in a field curvature change. This field curvature can be compensated by the use of a curved detector. When used together with freeform optics, the curved detectors allow for reduction of the number of optical components to two or even one element by merging their functions. Three design examples for the range of 810–860 nm reaching the spectral resolution limit of 89–139 pm at NA=0.14 are presented to demonstrate the achieved performance and the technological trade-offs. Full article
(This article belongs to the Special Issue Fiber Bragg Grating Based Sensors and Systems)
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Open AccessLetter
Demonstration of a Filterless, Multi-Point, and Temperature-Independent Fiber Bragg Grating Dynamical Demodulator Using Pulse-Width Modulation
Sensors 2020, 20(20), 5825; https://doi.org/10.3390/s20205825 - 15 Oct 2020
Viewed by 490
Abstract
We demonstrated in this work a filterless, multi-point and temperature-independent FBG (fiber Bragg grating) dynamical demodulator using pulse-width-modulation (PWM). In this approach, the FBG interrogation system is composed of a tunable laser and a demodulator that is designed to detect the wavelength shift [...] Read more.
We demonstrated in this work a filterless, multi-point and temperature-independent FBG (fiber Bragg grating) dynamical demodulator using pulse-width-modulation (PWM). In this approach, the FBG interrogation system is composed of a tunable laser and a demodulator that is designed to detect the wavelength shift of the FBG sensor without any optical filter making it very suitable to be used in harsh environments. In this work, we applied the proposed method that uses the PWM technique for FBG sensors placed in high pressure and high-temperature environments. The proposed method was characterized in the laboratory using an FBG sensor modulated in a frequency of 6 Hz, with a 1 kHz sweeping frequency in the wavelength range from 1527 to 1534 nm. Also, the method was evaluated in a field test in an engine of a thermoelectric power plant. Full article
(This article belongs to the Special Issue Fiber Bragg Grating Based Sensors and Systems)
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