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Fiber Optic Sensors and Applications 2021–2022

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

Deadline for manuscript submissions: closed (31 December 2022) | Viewed by 13951

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Special Issue Editors

Dr. Aitor Urrutia

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Guest Editor

Department of Electrical and Electronic Engineering, Institute of Smart Cities, Public University of Navarra, 31006 Pamplona, Spain
Interests: optical fiber sensors based on nanostructured coatings; plasmon resonance-based fiber sensors

Dr. Pablo Zubiate

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Guest Editor

Department of Electrical and Electronic Engineering, Public University of Navarra, 31006 Pamplona, Spain
Interests: optical sensor; LMRs probe; thin films; biosensing; nanostructures
Special Issues, Collections and Topics in MDPI journals

Dr. Nerea De Acha Morrás

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Guest Editor

Department of Electrical and Electronic Engineering, Public University of Navarra, 31006 Pamplona, Spain
Interests: optical fiber sensors; nanotechnology

Dr. Diego Lopez-Torres

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Guest Editor

Department. of Electrical and Electronic Engineering, Public University of Navarra, 31006 Pamplona, Spain
Interests: microstructured optical fiber (suspended core and photonic crystal fiber); optical fiber gas; volatile organic compound and humidity sensors

Special Issue Information

Dear Colleagues,

Optical fiber sensing is currently an emerging and versatile technology, thanks to the continuous advances in micro/nanofabrication techniques as well as the application of new nanomaterials. Novel microstructured fibers combined with a new generation of nanostructured coatings are enabling the development of enhanced optical fiber sensors. Consequently, there is an increasing interest in these fiber-based devices for the monitoring of physical, chemical, and biological parameters providing higher sensitivity ratios, better minimum concentration values, or improving other sensing parameters.

The aim of this Special Issue is to collect the most recent and relevant advances in fiber optic sensors, including fundamental and applied research, sensing platforms and fiber configurations, sensing mechanisms and other applications in the period 2021–2022.

Dr. Aitor Urrutia
Dr. Pablo Zubiate
Dr. Nerea De Acha
Dr. Diego Lopez-Torres
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Sensors is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

optical fiber sensors
physical and chemical sensors
biological sensors
interferometric sensors
resonance-based sensors
fiber gratings sensors
colorimetric sensors
fluorescence
microstructured fibers
nanostructured coatings

Published Papers (6 papers)

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Research

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10 pages, 2038 KiB

Open AccessCommunication

Interferometric Fiber Optic Probe for Measurements of Cavitation Bubble Expansion Velocity and Bubble Oscillation Time

by Emil Zubalic, Daniele Vella, Aleš Babnik and Matija Jezeršek

Sensors 2023, 23(2), 771; https://0-doi-org.brum.beds.ac.uk/10.3390/s23020771 - 10 Jan 2023

Cited by 3 | Viewed by 1767

Abstract

Cavitation bubbles are used in medicine as a mechanism to generate shock waves. The study of cavitation bubble dynamics plays a crucial role in understanding and utilizing such phenomena for practical applications and purposes. Since the lifetime of cavitation bubbles is in the range of hundreds of microseconds and the radii are in the millimeter range, the observation of bubble dynamics requires complicated and expensive equipment. High-speed cameras or other optical techniques require transparent containers or at least a transparent optical window to access the region. Fiber optic probe tips are commonly used to monitor water pressure, density, and temperature, but no study has used a fiber tip sensor in an interferometric setup to measure cavitation bubble dynamics. We present how a fiber tip sensor system, originally intended as a hydrophone, can be used to track the expansion and contraction of cavitation bubbles. The measurement is based on interference between light reflected from the fiber tip surface and light reflected from the cavitation bubble itself. We used a continuous-wave laser to generate cavitation bubbles and a high-speed camera to validate our measurements. The shock wave resulting from the collapse of a bubble can also be measured with a delay in the order of 1 µs since the probe tip can be placed less than 1 mm away from the origin of the cavitation bubble. By combining the information on the bubble expansion velocity and the time of bubble collapse, the lifetime of a bubble can be estimated. The bubble expansion velocity is measured with a spatial resolution of 488 nm, half the wavelength of the measuring laser. Our results demonstrate an alternative method for monitoring bubble dynamics without the need for expensive equipment. The method is flexible and can be adapted to different environmental conditions, opening up new perspectives in many application areas. Full article

(This article belongs to the Special Issue Fiber Optic Sensors and Applications 2021–2022)

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11 pages, 3482 KiB

Open AccessArticle

Influence of Bubble Deformation on the Signal Characteristics Generated Using an Optical Fiber Gas–liquid Two-Phase Flow Sensor

by Yu Ma, Yangrui Zhang, Song Li, Weimin Sun and Elfed Lewis

Sensors 2021, 21(21), 7338; https://0-doi-org.brum.beds.ac.uk/10.3390/s21217338 - 04 Nov 2021

Cited by 2 | Viewed by 1715

Abstract

The use of optical fiber probe in two-phase flow measurements is very frequently encountered, especially in the applications of chemical engineering and petroleum industries. In this work, the influence of bubble piercing signals caused by bubble deformation is studied experimentally using a laboratory-prepared wedge-shaped fiber probe in a lab-scale gas–liquid flow generator. A three-dimensional simulation model is established to study the influence of bubble deformation on the piercing signals. A theoretical analysis of the characteristics of the pre-signal influenced by the bubble deformations is undertaken for a wide range of different modeled bubble shapes. Combining the experimental and simulation results, a promising analytical method to estimate the bubble shapes by analyzing the characteristics of pre-signals is proposed. The results of this investigation demonstrate that it is possible to estimate the bubble shapes before the fiber probe contacts the bubble surface. The method developed in this investigation is therefore highly promising for reducing errors caused by deformation during the probe piercing process. Full article

(This article belongs to the Special Issue Fiber Optic Sensors and Applications 2021–2022)

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17 pages, 1913 KiB

Open AccessArticle

Efficient Optical Sensing Based on Phase Shift of Waves Supported by a One-Dimensional Photonic Crystal

by Roman Kaňok, Petr Hlubina, Lucie Gembalová and Dalibor Ciprian

Sensors 2021, 21(19), 6535; https://0-doi-org.brum.beds.ac.uk/10.3390/s21196535 - 30 Sep 2021

Cited by 9 | Viewed by 1715

Abstract

Interferometric methods of optical sensing based on the phase shift of the Bloch surface waves (BSWs) and guided waves (GWs) supported by a one-dimensional photonic crystal are presented. The photonic crystal, composed of six SiO₂/TiO₂ bilayers with a termination layer of TiO₂, is employed in the Kretschmann configuration. Under resonance condition, an abrupt phase change is revealed, and the corresponding phase shift is measured by interferometric techniques applied in both the spectral and spatial domains. The spectral interferometric technique employing a birefringent quartz crystal is used to obtain interference of projections of p- and s-polarized light waves reflected from the photonic crystal. The phase shifts are retrieved by processing the spectral interferograms recorded for various values of relative humidity (RH) of air, giving the sensitivity to the RH as high as 0.029 rad/%RH and 0.012 rad/%RH for the BSW and GW, respectively. The spatial interferometric technique employs a Wollaston prism and an analyzer to generate an interference pattern, which is processed to retrieve the phase difference, and results are in good agreement with those obtained by sensing the phase shift in the spectral domain. In addition, from the derivative of the spectral phase shifts, the peak positions are obtained, and their changes with the RH give the sensitivities of 0.094 nm/%RH and 0.061 nm/%RH for the BSW and GW, respectively. These experimental results demonstrate an efficient optical sensing with a lot of applications in various research areas. Full article

(This article belongs to the Special Issue Fiber Optic Sensors and Applications 2021–2022)

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10 pages, 3855 KiB

Open AccessCommunication

Highly Sensitive Dual Parameter Sensor Based on a Hybrid Structure with Multimode Interferometer and Fiber Bragg Grating Fabricated by Femtosecond Laser

by Xinran Dong, Li Zeng, Dongkai Chu and Xiaoyan Sun

Sensors 2021, 21(17), 5938; https://0-doi-org.brum.beds.ac.uk/10.3390/s21175938 - 03 Sep 2021

Cited by 5 | Viewed by 1945

Abstract

A hybrid sensing configuration for simultaneous measurement of strain and temperature based on fiber Bragg grating (FBG) written in an offset multimode fiber (MMF) interferometer using femtosecond laser pulse is proposed and demonstrated. A Mach–Zehnder interferometer is formed by splicing a section of MMF between two single-mode fibers (SMFs) and a high interference fringe of up to 15 dB is achieved. The sensing experimental results show a strain sensitivity of −1.17 pm/με and 0.6498 pm/με for the dip of MZI and Bragg peak, while a temperature sensitivity of 42.84 pm/°C and 19.96 pm/°C is measured. Furthermore, the matrix analysis has found that the strain and temperature resolution of the sensor are as high as ±12.36 με and ±0.35 °C, respectively. In addition, the sensor has merits of simple fabrication, good spectral quality, and high resolution, which shows attractive potential applications in dual-parameter sensing. Full article

(This article belongs to the Special Issue Fiber Optic Sensors and Applications 2021–2022)

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15 pages, 5776 KiB

Open AccessArticle

Deep UV Formation of Long-Term Stable Optical Bragg Gratings in Epoxy Waveguides and Their Biomedical Sensing Potentials

by Steffen Hessler, Marieke Rüth, Horst-Dieter Lemke, Bernhard Schmauss and Ralf Hellmann

Sensors 2021, 21(11), 3868; https://0-doi-org.brum.beds.ac.uk/10.3390/s21113868 - 03 Jun 2021

Cited by 1 | Viewed by 2099

Abstract

In this article, we summarize our investigations on optimized 248 nm deep ultraviolet (UV) fabrication of highly stable epoxy polymer Bragg grating sensors and their application for biomedical purposes. Employing m-line spectroscopy, deep UV photosensitivity of cross-linked EpoCore thin films in terms of responding refractive index change is determined to a maximum of Δn = + (1.8 ± 0.2) × 10⁻³. All-polymer waveguide Bragg gratings are fabricated by direct laser irradiation of lithographic EpoCore strip waveguides on compatible Topas 6017 substrates through standard +1/-1-order phase masks. According near-field simulations of realistic non-ideal phase masks provide insight into UV dose-dependent characteristics of the Bragg grating formation. By means of online monitoring, arising Bragg reflections during grating inscription via beforehand fiber-coupled waveguide samples, an optimum laser parameter set for well-detectable sensor reflection peaks in respect of peak strength, full width at half maximum and grating attenuation are derived. Promising blood analysis applications of optimized epoxy-based Bragg grating sensors are demonstrated in terms of bulk refractive index sensing of whole blood and selective surface refractive index sensing of human serum albumin. Full article

(This article belongs to the Special Issue Fiber Optic Sensors and Applications 2021–2022)

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Review

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20 pages, 3166 KiB

Open AccessReview

Optical Fiber Probe Microcantilever Sensor Based on Fabry–Perot Interferometer

by Yongzhang Chen, Yiwen Zheng, Haibing Xiao, Dezhi Liang, Yufeng Zhang, Yongqin Yu, Chenlin Du and Shuangchen Ruan

Sensors 2022, 22(15), 5748; https://0-doi-org.brum.beds.ac.uk/10.3390/s22155748 - 01 Aug 2022

Cited by 6 | Viewed by 2605

Abstract

Optical fiber Fabry–Perot sensors have long been the focus of researchers in sensing applications because of their unique advantages, including highly effective, simple light path, low cost, compact size, and easy fabrication. Microcantilever-based devices have been extensively explored in chemical and biological fields while the interrogation methods are still a challenge. The optical fiber probe microcantilever sensor is constructed with a microcantilever beam on an optical fiber, which opens the door for highly sensitive, as well as convenient readout. In this review, we summarize a wide variety of optical fiber probe microcantilever sensors based on Fabry–Perot interferometer. The operation principle of the optical fiber probe microcantilever sensor is introduced. The fabrication methods, materials, and sensing applications of an optical fiber probe microcantilever sensor with different structures are discussed in detail. The performances of different kinds of fiber probe microcantilever sensors are compared. We also prospect the possible development direction of optical fiber microcantilever sensors. Full article

(This article belongs to the Special Issue Fiber Optic Sensors and Applications 2021–2022)

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