sensors-logo

Journal Browser

Journal Browser

Optical Fiber Sensors

A topical collection in Sensors (ISSN 1424-8220). This collection belongs to the section "Optical Sensors".

Viewed by 54969

Editor

1. School of Technology and Management, Polytechnic Institute of Viana do Castelo, 4900-348 Viana do Castelo, Portugal
2. Centre for Applied Photonics (CAP), Institute for Systems and Computer Engineering, Technology and Science – INESC TEC, 4150-179 Porto, Portugal
Interests: long-period gratings; optical fibers; optical fiber sensors; interferometers; whispering gallery modes; microresonators; optical fiber communications
Special Issues, Collections and Topics in MDPI journals

Topical Collection Information

Dear Colleagues,

Interest in sensors based on optical technology and in particular those based on optical fibers has been growing rapidly in recent years. High-performance sensor devices and platforms with high-sensitivity and selectivity and a low limit of detection values have been proposed. The reasons for this are manifold: immunity to electromagnetic interference, small size, robustness, ability of remote operation, potential intrinsic multiplexing, high sensitivity, and great versatility associated to the large number of independent parameters that characterize radiation, as is the case of intensity, wavelength, frequency, phase, and polarization, all of them potentially sensitive to physical, chemical, and biological measurands.

In this Special Issue, dedicated to optical fiber sensors, we will focus on recent advances and developments in optical fibers, and original research papers, as well as reviews, are welcome. The goal is to gather contributions on various aspects related to optical fibers sensors, namely, new types of optical fibers, optical sources, devices in optical fibers (FBG, LPG, interferometers, etc.), and applications.

I hope that this Special Issue will provide the scientific community with a thorough overview of the current research on optical fibers sensors.

Prof. Dr. Paulo Caldas
Collection Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the collection website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

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 fibers
  • sensors
  • optical sources
  • bragg grating
  • long period grating
  • interferometers

Published Papers (20 papers)

2023

Jump to: 2022, 2021, 2020

12 pages, 1815 KiB  
Article
A Green Approach to Natural Dyes in Dye-Sensitized Solar Cells
by Nurul Izzati Abdul Shukor, Kah-Yoong Chan, Gregory Soon How Thien, Mian-En Yeoh, Pei-Ling Low, Nisha Kumari Devaraj, Zi-Neng Ng and Boon Kar Yap
Sensors 2023, 23(20), 8412; https://0-doi-org.brum.beds.ac.uk/10.3390/s23208412 - 12 Oct 2023
Cited by 2 | Viewed by 1641
Abstract
Solar cells are pivotal in harnessing renewable energy for a greener and more sustainable energy landscape. Nonetheless, eco-friendly materials for solar cells have not been as extensive as conventional counterparts, highlighting a significant area for further investigation in advancing sustainable energy technologies. This [...] Read more.
Solar cells are pivotal in harnessing renewable energy for a greener and more sustainable energy landscape. Nonetheless, eco-friendly materials for solar cells have not been as extensive as conventional counterparts, highlighting a significant area for further investigation in advancing sustainable energy technologies. This study investigated natural dyes from cost-effective and environmentally friendly blueberries and mulberries. These dyes were utilized as alternative sensitizers for dye-sensitized solar cells (DSSCs). Alongside the natural dyes, a green approach was adopted for the DSSC design, encompassing TiO2 photoanodes, eco-friendly electrolytes, and green counter-electrodes created from graphite pencils and candle soot. Consequently, the best-optimized dye sensitizer was mulberry, with an output power of 13.79 µW and 0.122 µW for outdoor and indoor environments, respectively. This study underscored the feasibility of integrating DSSCs with sensitizers derived from readily available food ingredients, potentially expanding their applications in educational kits and technology development initiatives. Full article
Show Figures

Graphical abstract

10 pages, 2765 KiB  
Communication
Directional Torsion Sensor Based on a Two-Core Fiber with a Helical Structure
by Zhuo Song, Yichun Li and Junhui Hu
Sensors 2023, 23(6), 2874; https://0-doi-org.brum.beds.ac.uk/10.3390/s23062874 - 07 Mar 2023
Cited by 5 | Viewed by 1367
Abstract
A fiber-optic torsion sensor based on a helical two-core fiber (HTCF) is proposed and experimentally demonstrated for simultaneously measuring torsion angle and torsion direction. The sensor consists of a segment of HTCF and two single-mode fibers (SMFs) forming a Mach–Zehnder interferometer (MZI). The [...] Read more.
A fiber-optic torsion sensor based on a helical two-core fiber (HTCF) is proposed and experimentally demonstrated for simultaneously measuring torsion angle and torsion direction. The sensor consists of a segment of HTCF and two single-mode fibers (SMFs) forming a Mach–Zehnder interferometer (MZI). The helical structure is implemented by pre-twisting a 1 cm long two-core fiber (TCF). The performance of the sensor with pre-twisted angles of 180°, 360°, and 540° is experimentally analyzed. The results show that the sensor can realize the angular measurement and effectively distinguish the torsion direction. It is worth noting that the sensor has maximum sensitivity when the pre-twist angle is 180 degrees. The obtained wavelength sensitivities of torsion and temperature are 0.242 nm/(rad/m) and 32 pm/°C, respectively. The sensor has the advantages of easy fabrication, low cost, compact structure, and high sensitivity, which is expected to yield potential applications in fields where both torsion angle and direction measurements are required. Full article
Show Figures

Figure 1

2022

Jump to: 2023, 2021, 2020

13 pages, 10451 KiB  
Communication
Non-Intrusive Pipeline Flow Detection Based on Distributed Fiber Turbulent Vibration Sensing
by Ying Shang, Chen Wang, Yongkang Zhang, Wenan Zhao, Jiasheng Ni and Gangding Peng
Sensors 2022, 22(11), 4044; https://0-doi-org.brum.beds.ac.uk/10.3390/s22114044 - 26 May 2022
Cited by 4 | Viewed by 1730
Abstract
We demonstrate a non-intrusive dynamic monitoring method of oil well flow based on distributed optical fiber acoustic sensing (DAS) technology and the turbulent vibration. The quantitative measurement of the flow rate is theoretically acquired though the amplitude of the demodulated phase changes from [...] Read more.
We demonstrate a non-intrusive dynamic monitoring method of oil well flow based on distributed optical fiber acoustic sensing (DAS) technology and the turbulent vibration. The quantitative measurement of the flow rate is theoretically acquired though the amplitude of the demodulated phase changes from DAS based on the flow impact in the tube on the pipe wall. The experimental results show that the relationships between the flow rate and the demodulated phase changes, in both a whole frequency region and in a sensitive-response frequency region, fit the quadratic equation well, with a max R2 of 0.997, which is consistent with the theoretical simulation results. The detectable flow rate is from 0.73 m3/h to 2.48 m3/h. The experiments verify the feasibility of DAS system flow monitoring and provide technical support for the practical application of the downhole flow measurement. Full article
Show Figures

Figure 1

22 pages, 8565 KiB  
Article
Experimental Analysis and Multiscale Modeling of the Dynamics of a Fiber-Optic Coil
by Özkan Kahveci, Caner Gençoğlu and Tuncay Yalçinkaya
Sensors 2022, 22(2), 582; https://0-doi-org.brum.beds.ac.uk/10.3390/s22020582 - 13 Jan 2022
Cited by 2 | Viewed by 2024
Abstract
Fiber-optic gyroscopes (FOGs) are common rotation measurement devices in aerospace applications. They have a wide range of diversity in length and in the winding radius of the coil to meet system requirements. Every dimensional parameter in the coil influences the dynamic response of [...] Read more.
Fiber-optic gyroscopes (FOGs) are common rotation measurement devices in aerospace applications. They have a wide range of diversity in length and in the winding radius of the coil to meet system requirements. Every dimensional parameter in the coil influences the dynamic response of the system, eventually leading to measurement errors. In order to eliminate the errors and to qualify the system, after the design and production stages, a deep and comprehensive testing procedure follows. In this study, the dynamic behavior of a quadrupole wound fiber-optic coil is investigated. First, pre-wound fiber-optic coils are tested with an impact modal test, where the mode shapes and natural frequencies are determined with structural data acquisition. For the modal analysis, a finite element (FE) model is developed where a representative volume element (RVE) analysis is also included to properly consider the influence of the microstructure. The experimental and numerical results are compared and validated. Moreover, an estimation model is proposed for a type of coil with different fiber lengths. Finally, the estimated coil set is produced and tested employing the same methodology in order to illustrate the capacity of the developed framework. Full article
Show Figures

Figure 1

14 pages, 3095 KiB  
Article
Research on the Dual Modulation of All-Fiber Optic Current Sensor
by Jianhua Wu, Xiaofeng Zhang and Liang Chen
Sensors 2022, 22(2), 430; https://0-doi-org.brum.beds.ac.uk/10.3390/s22020430 - 07 Jan 2022
Cited by 3 | Viewed by 1541
Abstract
Acousto-optic modulator (AOM) and electro-optical modulator (EOM) are applied to realize the all-fiber current sensor with a pulsed light source. The pulsed light is realized by amplitude modulation with AOM. The reflected interferometer current sensor is constructed by the mirror and phase modulation [...] Read more.
Acousto-optic modulator (AOM) and electro-optical modulator (EOM) are applied to realize the all-fiber current sensor with a pulsed light source. The pulsed light is realized by amplitude modulation with AOM. The reflected interferometer current sensor is constructed by the mirror and phase modulation with EOM to improve the anti-interference ability. A correlation demodulation algorithm is applied for data processing. The influence of the modulation frequency and duty cycle of AOM on the optical system is determined by modeling and experiment. The duty cycle is the main factor affecting the normalized scale factor of the system. The modulation frequency mainly affects the output amplitude of the correlation demodulation and the system signal-to-noise ratio. The frequency multiplication factor links AOM and EOM, primarily affecting the ratio error. When the frequency multiplication factor is equal to the duty cycle of AOM and it is an integer multiple of 0.1, the ratio error of the system is less than 1.8% and the sensitivity and the resolution of AFOCS are 0.01063 mV/mA and 3 mA, respectively. The measurement range of AFOCS is from 11 mA to 196.62 A, which is excellent enough to meet the practical requirements for microcurrent measurement. Full article
Show Figures

Figure 1

2021

Jump to: 2023, 2022, 2020

15 pages, 5351 KiB  
Communication
High-Temperature Measurement of a Fiber Probe Sensor Based on the Michelson Interferometer
by Jiahao Guo, Siping Lian, Ying Zhang, Yufeng Zhang, Dezhi Liang, Yongqin Yu, Ruohang Chen, Chenlin Du and Shuangchen Ruan
Sensors 2022, 22(1), 289; https://0-doi-org.brum.beds.ac.uk/10.3390/s22010289 - 31 Dec 2021
Cited by 13 | Viewed by 2336
Abstract
In this paper, a fiber probe high-temperature sensor based on the Michelson Interferometer (MI) is proposed and experimentally verified. We used a fiber splicing machine to fabricate a taper of the single-mode fiber (SMF) end. The high order modes were excited at the [...] Read more.
In this paper, a fiber probe high-temperature sensor based on the Michelson Interferometer (MI) is proposed and experimentally verified. We used a fiber splicing machine to fabricate a taper of the single-mode fiber (SMF) end. The high order modes were excited at the taper, so that different modes were transmitted forward in the fiber and reflected by the end face of the fiber and then recoupled back to the fiber core to form MI. For comparison, we also coated a thin gold film on the fiber end to improve the reflectivity, and the reflection intensity was improved by 16 dB. The experimental results showed that the temperature sensitivity at 1506 nm was 80 pm/°C (100 °C~450 °C) and 109 pm/°C (450 °C~900 °C). The repeated heating and cooling processes showed that the MI structure had good stability at a temperature up to 900 °C. This fiber probe sensor has the advantages of a small size, simple structure, easy manufacturing, good stability, and broad application prospects in industrial and other environments. Full article
Show Figures

Figure 1

22 pages, 1720 KiB  
Article
Icing Condition Predictions Using FBGS
by Miguel González del Val, Julio Mora Nogués, Paloma García Gallego and Malte Frövel
Sensors 2021, 21(18), 6053; https://0-doi-org.brum.beds.ac.uk/10.3390/s21186053 - 09 Sep 2021
Cited by 8 | Viewed by 1886
Abstract
Icing is a hazard which is important for the aerospace industry and which has grown over the last few years. Developing sensors that can detect the existence not only of standard icing conditions with typically small droplet size, but also of Supercooled Large [...] Read more.
Icing is a hazard which is important for the aerospace industry and which has grown over the last few years. Developing sensors that can detect the existence not only of standard icing conditions with typically small droplet size, but also of Supercooled Large Droplet (SLD) conditions is one of the most important aims in order to minimize icing hazards in the near future. In the present paper a study of the Fiber Bragg Grating Sensors’ (FBGSs) performance as a flight icing detection system that predicts the conditions of an icing cloud is carried out. The test matrix was performed in the INTA Icing Wind Tunnel (IWT) with several icing conditions including SLD. Two optic fibers with 16 FBGS in total were integrated in the lower and upper surface of an airfoil to measure the temperature all over the chord. The results are compared with a Messinger heat and mass balance model and the measurements of the FBGS are used to predict the Liquid Water Content (LWC) and Ice Accretion Rate (IAR). Finally, the results are evaluated and a sensor assessment is made. A good correlation was observed between theoretical calculations and test results obtained with the FBGS in the IWT tests. FBGS proved to detect the beginning and end of ice accretion, LWC and IAR quickly and with good precision. Full article
Show Figures

Figure 1

14 pages, 3191 KiB  
Article
Control of Excitation of Cladding Modes by Tapering an Insertion of Special Fiber
by Diomid D. Bakurov and Oleg V. Ivanov
Sensors 2021, 21(7), 2498; https://0-doi-org.brum.beds.ac.uk/10.3390/s21072498 - 03 Apr 2021
Cited by 4 | Viewed by 1659
Abstract
A method for controlling the excitation of cladding modes by tapering special fiber insertions made of SM450 and coreless fibers is proposed. The coupling coefficients between the core mode and the cladding modes of the tapered fiber insertion are calculated. For the calculation, [...] Read more.
A method for controlling the excitation of cladding modes by tapering special fiber insertions made of SM450 and coreless fibers is proposed. The coupling coefficients between the core mode and the cladding modes of the tapered fiber insertion are calculated. For the calculation, changes in the effective refractive indices and phases of the fiber core and in the cladding modes upon tapering are found. The field distribution of the core mode of the standard fiber transmitted through fiber insertion is obtained. The transmission characteristics of insertions of SM450 and coreless fibers during tapering are simulated and compared with the experiment. The possibility of controlling the transmission and excitation of various cladding modes is confirmed experimentally. Full article
Show Figures

Figure 1

10 pages, 3097 KiB  
Communication
Acoustic Optical Fiber Sensor Based on Graphene Oxide Membrane
by Catarina S. Monteiro, Maria Raposo, Paulo A. Ribeiro, Susana O. Silva and Orlando Frazão
Sensors 2021, 21(7), 2336; https://0-doi-org.brum.beds.ac.uk/10.3390/s21072336 - 27 Mar 2021
Cited by 18 | Viewed by 3094
Abstract
A Fabry–Pérot acoustic sensor based on a graphene oxide membrane was developed with the aim to achieve a faster and simpler fabrication procedure when compared to similar graphene-based acoustic sensors. In addition, the proposed sensor was fabricated using methods that reduce chemical hazards [...] Read more.
A Fabry–Pérot acoustic sensor based on a graphene oxide membrane was developed with the aim to achieve a faster and simpler fabrication procedure when compared to similar graphene-based acoustic sensors. In addition, the proposed sensor was fabricated using methods that reduce chemical hazards and environmental impacts. The developed sensor, with an optical cavity of around 246 µm, showed a constant reflected signal amplitude of 6.8 ± 0.1 dB for 100 nm wavelength range. The sensor attained a wideband operation range between 20 and 100 kHz, with a maximum signal-to-noise ratio (SNR) of 32.7 dB at 25 kHz. The stability and sensitivity to temperatures up to 90 °C was also studied. Moreover, the proposed sensor offers the possibility to be applied as a wideband microphone or to be applied in more complex systems for structural analysis or imaging. Full article
Show Figures

Figure 1

13 pages, 2840 KiB  
Article
Effect of Low-Doses of Gamma Radiation on Electric Arc-Induced Long Period Fiber Gratings
by Patricia Mesonero-Santos, Ana Fernández-Medina, Luis C. C. Coelho, Duarte Viveiros, Pedro A. Jorge, Tomás Belenguer and Raquel López Heredero
Sensors 2021, 21(7), 2318; https://0-doi-org.brum.beds.ac.uk/10.3390/s21072318 - 26 Mar 2021
Cited by 4 | Viewed by 1845
Abstract
This work presents an experimental study on the effects of gamma radiation on Long Period Fiber Gratings (LPFGs) in a low-dose test campaign to evaluate their eventual degradation. The study was carried out with standard single-mode fibers where the grating was inscribed using [...] Read more.
This work presents an experimental study on the effects of gamma radiation on Long Period Fiber Gratings (LPFGs) in a low-dose test campaign to evaluate their eventual degradation. The study was carried out with standard single-mode fibers where the grating was inscribed using the Electric-Arc Discharge (EAD) technique. Before the gamma campaign, a detailed optical characterization was performed with repeatability tests to verify the accuracy of the setup and the associated error sources. The gamma-induced changes up to a dose of 200 krad and the recovery after radiation were monitored with the Dip Wavelength Shift (DWS). The results show that the gamma sensitivity for a total dose of 200 krad is 11 pm/krad and a total DWS of 2.3 nm has been observed with no linear dependence. Post-radiation study shows that recovery from radiation-induced wavelength shift is nearly complete in about 4000 h. Experimental results show that the changes suffered under gamma irradiation of these LPFGs are temporary making them a good choice as sensors in space applications. Full article
Show Figures

Figure 1

17 pages, 3242 KiB  
Article
Proof of Concept for a Quick and Highly Sensitive On-Site Detection of SARS-CoV-2 by Plasmonic Optical Fibers and Molecularly Imprinted Polymers
by Nunzio Cennamo, Girolamo D’Agostino, Chiara Perri, Francesco Arcadio, Guido Chiaretti, Eva Maria Parisio, Giulio Camarlinghi, Chiara Vettori, Francesco Di Marzo, Rosario Cennamo, Giovanni Porto and Luigi Zeni
Sensors 2021, 21(5), 1681; https://0-doi-org.brum.beds.ac.uk/10.3390/s21051681 - 01 Mar 2021
Cited by 69 | Viewed by 5207
Abstract
The rapid spread of the Coronavirus Disease 2019 (COVID-19) pandemic, caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) pathogen has generated a huge international public health emergency. Currently the reference diagnostic technique for virus determination is Reverse Transcription Polymerase Chain Reaction [...] Read more.
The rapid spread of the Coronavirus Disease 2019 (COVID-19) pandemic, caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) pathogen has generated a huge international public health emergency. Currently the reference diagnostic technique for virus determination is Reverse Transcription Polymerase Chain Reaction (RT-PCR) real time analysis that requires specialized equipment, reagents and facilities and typically 3–4 h to perform. Thus, the realization of simple, low-cost, small-size, rapid and point-of-care diagnostics tests has become a global priority. In response to the current need for quick, highly sensitive and on-site detection of the SARS-CoV-2 virus in several aqueous solutions, a specific molecularly imprinted polymer (MIP) receptor has been designed, realized, and combined with an optical sensor. More specifically, the proof of concept of a SARS-CoV-2 sensor has been demonstrated by exploiting a plasmonic plastic optical fiber sensor coupled with a novel kind of synthetic MIP nano-layer, especially designed for the specific recognition of Subunit 1 of the SARS-CoV-2 Spike protein. First, we have tested the effectiveness of the developed MIP receptor to bind the Subunit 1 of the SARS-CoV-2 spike protein, then the results of preliminary tests on SARS-CoV-2 virions, performed on samples of nasopharyngeal (NP) swabs in universal transport medium (UTM) and physiological solution (0.9% NaCl), were compared with those obtained with RT-PCR. According to these preliminary results, the sensitivity of the proposed optical-chemical sensor proved to be higher than the RT-PCR one. Furthermore, a relatively fast response time (about 10 min) to the virus was obtained without the use of additional reagents. Full article
Show Figures

Figure 1

10 pages, 2393 KiB  
Communication
Monitoring the Growth of a Microbubble Generated Photothermally onto an Optical Fiber by Means Fabry–Perot Interferometry
by J. Gabriel Ortega-Mendoza, Placido Zaca-Morán, J. Pablo Padilla-Martínez, Josué E. Muñoz-Pérez, José Luis Cruz and Miguel V. Andrés
Sensors 2021, 21(2), 628; https://0-doi-org.brum.beds.ac.uk/10.3390/s21020628 - 18 Jan 2021
Cited by 3 | Viewed by 2230
Abstract
In the present paper, we show the experimental measurement of the growth of a microbubble created on the tip of a single mode optical fiber, in which zinc nanoparticles were photodeposited on its core by using a single laser source to carry out [...] Read more.
In the present paper, we show the experimental measurement of the growth of a microbubble created on the tip of a single mode optical fiber, in which zinc nanoparticles were photodeposited on its core by using a single laser source to carry out both the generation of the microbubble by photothermal effect and the monitoring of the microbubble diameter. The photodeposition technique, as well as the formation of the microbubble, was carried out by using a single-mode pigtailed laser diode with emission at a wavelength of 658 nm. The microbubble’s growth was analyzed in the time domain by the analysis of the Fabry–Perot cavity, whose diameter was calculated with the number of interference fringes visualized in an oscilloscope. The results obtained with this technique were compared with images obtained from a CCD camera, in order to verify the diameter of the microbubble. Therefore, by counting the interference fringes, it was possible to quantify the temporal evolution of the microbubble. As a practical demonstration, we proposed a vibrometer sensor using microbubbles with sizes of 83 and 175 µm as a Fabry–Perot cavity; through the time period of a full oscillation cycle of an interferogram observed in the oscilloscope, it was possible to know the frequency vibration (500 and 1500 Hz) for a cuvette where the microbubble was created. Full article
Show Figures

Graphical abstract

2020

Jump to: 2023, 2022, 2021

17 pages, 4239 KiB  
Article
Verification of the Propagation Range of Respiratory Strain Using Signal Waveform Measured by FBG Sensors
by Shouhei Koyama, Atsushi Fujimoto, Yuma Yasuda and Yuuki Satou
Sensors 2020, 20(24), 7076; https://0-doi-org.brum.beds.ac.uk/10.3390/s20247076 - 10 Dec 2020
Cited by 5 | Viewed by 2094
Abstract
The FBG (Fiber Bragg grating) sensor is an optical fiber type strain sensor. When a person breathes, strain occurs in the lungs and diaphragm. This was verified using an FBG sensor to which part of the living body this respiratory strain propagates. When [...] Read more.
The FBG (Fiber Bragg grating) sensor is an optical fiber type strain sensor. When a person breathes, strain occurs in the lungs and diaphragm. This was verified using an FBG sensor to which part of the living body this respiratory strain propagates. When measured in the abdomen, the signal waveforms were significantly different between breathing and apnea. The respiratory cycle measured by the temperature sensor attached to the mask and the strain cycle measured by the FBG sensor almost matched. Respiratory strain was measured in the abdomen, chest, and shoulder, and the signal amplitude decreased with distance from the abdomen. In addition, the respiratory rate could be calculated from the measured strain signal. On the other hand, respiratory strain did not propagate to the elbows and wrists, which were off the trunk, and the respiratory time, based on the signal period, could not be calculated at these parts. Therefore, it was shown that respiratory strain propagated in the trunk from the abdomen to the shoulder, but not in the peripheral parts of the elbow and wrist. Full article
Show Figures

Figure 1

10 pages, 36551 KiB  
Communication
Fiber Bragg Grating with Enhanced Cladding Modes Inscribed by Femtosecond Laser and a Phase Mask
by Weijia Bao, Shen Liu, Wenjie Feng and Yiping Wang
Sensors 2020, 20(24), 7004; https://0-doi-org.brum.beds.ac.uk/10.3390/s20247004 - 08 Dec 2020
Cited by 2 | Viewed by 2581
Abstract
In this paper, we demonstrate a fiber Bragg grating (FBG) with a wide range and a comb with continuous cladding mode resonances inscribed in non-photosensitive single mode fibers using a femtosecond laser and a phase mask. The FBG is inscribed in the core [...] Read more.
In this paper, we demonstrate a fiber Bragg grating (FBG) with a wide range and a comb with continuous cladding mode resonances inscribed in non-photosensitive single mode fibers using a femtosecond laser and a phase mask. The FBG is inscribed in the core and cladding, exciting a series of cladding modes in transmission. The birefringence induced by this FBG structure offers significant polarization-dependence for cladding modes, thus allowing the vector fiber twist to be perceived. By measuring the peak-to-peak differential intensity of orthogonally polarized cladding mode resonances, the proposed sensor presents totally opposite intensity response in the anticlockwise direction for the torsion angle ranging from −45° to 45°. The cladding mode comb approximately covers wavelengths over the O-, E-, S-, and C-bands in transmission. The cutoff cladding mode of air can be observed in the spectrum. Thus, the sensible refractive index range is estimated to be from 1.00 to 1.44. Temperature responsivity of the grating is also characterized. The proposed device potentially provides new solutions to the various challenges of physical vector and bio-chemical parameters sensing. Full article
Show Figures

Figure 1

37 pages, 22464 KiB  
Review
Optical Fiber Sensors by Direct Laser Processing: A Review
by David Pallarés-Aldeiturriaga, Pablo Roldán-Varona, Luis Rodríguez-Cobo and José Miguel López-Higuera
Sensors 2020, 20(23), 6971; https://0-doi-org.brum.beds.ac.uk/10.3390/s20236971 - 06 Dec 2020
Cited by 20 | Viewed by 5503
Abstract
The consolidation of laser micro/nano processing technologies has led to a continuous increase in the complexity of optical fiber sensors. This new avenue offers novel possibilities for advanced sensing in a wide set of application sectors and, especially in the industrial and medical [...] Read more.
The consolidation of laser micro/nano processing technologies has led to a continuous increase in the complexity of optical fiber sensors. This new avenue offers novel possibilities for advanced sensing in a wide set of application sectors and, especially in the industrial and medical fields. In this review, the most important transducing structures carried out by laser processing in optical fiber are shown. The work covers different types of fiber Bragg gratings with an emphasis in the direct-write technique and their most interesting inscription configurations. Along with gratings, cladding waveguide structures in optical fibers have reached notable importance in the development of new optical fiber transducers. That is why a detailed study is made of the different laser inscription configurations that can be adopted, as well as their current applications. Microcavities manufactured in optical fibers can be used as both optical transducer and hybrid structure to reach advanced soft-matter optical sensing approaches based on optofluidic concepts. These in-fiber cavities manufactured by femtosecond laser irradiation followed by chemical etching are promising tools for biophotonic devices. Finally, the enhanced Rayleigh backscattering fibers by femtosecond laser dots inscription are also discussed, as a consequence of the new sensing possibilities they enable. Full article
Show Figures

Figure 1

12 pages, 3945 KiB  
Article
Negative Curvature Hollow Core Fiber Based All-Fiber Interferometer and Its Sensing Applications to Temperature and Strain
by Dejun Liu, Wei Li, Qiang Wu, Haoyu Zhao, Fengzi Ling, Ke Tian, Changyu Shen, Fangfang Wei, Wei Han, Gerald Farrell, Yuliya Semenova and Pengfei Wang
Sensors 2020, 20(17), 4763; https://0-doi-org.brum.beds.ac.uk/10.3390/s20174763 - 23 Aug 2020
Cited by 11 | Viewed by 2901
Abstract
Negative curvature hollow core fiber (NCHCF) is a promising candidate for sensing applications; however, research on NCHCF based fiber sensors starts only in the recent two years. In this work, an all-fiber interferometer based on an NCHCF structure is proposed for the first [...] Read more.
Negative curvature hollow core fiber (NCHCF) is a promising candidate for sensing applications; however, research on NCHCF based fiber sensors starts only in the recent two years. In this work, an all-fiber interferometer based on an NCHCF structure is proposed for the first time. The interferometer was fabricated by simple fusion splicing of a short section of an NCHCF between two singlemode fibers (SMFs). Both simulation and experimental results show that multiple modes and modal interferences are excited within the NCHCF structure. Periodic transmission dips with high spectral extinction ratio (up to 30 dB) and wide free spectral range (FSR) are produced, which is mainly introduced by the modes coupling between HE11 and HE12. A small portion of light guiding by means of Anti-resonant reflecting optical waveguide (ARROW) mechanism is also observed. The transmission dips, resulting from multimode interferences (MMI) and ARROW effect have a big difference in sensitivities to strain and temperature, thus making it possible to monitor these two parameters with a single sensor head by using a characteristic matrix approach. In addition, the proposed sensor structure is experimentally proven to have a good reproducibility. Full article
Show Figures

Figure 1

8 pages, 2563 KiB  
Communication
A High-Strength Strain Sensor Based on a Reshaped Micro-Air-Cavity
by Yanping Chen, Junxian Luo, Shen Liu, Mengqiang Zou, Shengzhen Lu, Yong Yang, Changrui Liao and Yiping Wang
Sensors 2020, 20(16), 4530; https://0-doi-org.brum.beds.ac.uk/10.3390/s20164530 - 13 Aug 2020
Cited by 5 | Viewed by 2093
Abstract
We demonstrate a high-strength strain sensor based on a micro-air-cavity reshaped through repeating arc discharge. The strain sensor has a micro-scale cavity, approximate plane reflection, and large wall thickness, contributing to a broad free spectrum range ~36 nm at 1555 nm, high fringe [...] Read more.
We demonstrate a high-strength strain sensor based on a micro-air-cavity reshaped through repeating arc discharge. The strain sensor has a micro-scale cavity, approximate plane reflection, and large wall thickness, contributing to a broad free spectrum range ~36 nm at 1555 nm, high fringe contrast ~38 dB, and super-high mechanical robustness, respectively. A sensitivity of ~2.39 pm/με and a large measurement range of 0 to 9800 με are achieved for this strain sensor. The strain sensor has a high strength, e.g., the tensile strain applied the sensor is up to 10,000 με until the tested the single-mode fiber is broken into two sections. In addition, it exhibited low thermal sensitivity of less than 1.0 pm/°C reducing the cross-sensitivity between tensile strain and temperature. Full article
Show Figures

Figure 1

24 pages, 5124 KiB  
Review
A Review of Coating Materials Used to Improve the Performance of Optical Fiber Sensors
by Changxu Li, Wenlong Yang, Min Wang, Xiaoyang Yu, Jianying Fan, Yanling Xiong, Yuqiang Yang and Linjun Li
Sensors 2020, 20(15), 4215; https://0-doi-org.brum.beds.ac.uk/10.3390/s20154215 - 29 Jul 2020
Cited by 49 | Viewed by 6325
Abstract
In order to improve the performance of fiber sensors and fully tap the potential of optical fiber sensors, various optical materials have been selectively coated on optical fiber sensors under the background of the rapid development of various optical materials. On the basis [...] Read more.
In order to improve the performance of fiber sensors and fully tap the potential of optical fiber sensors, various optical materials have been selectively coated on optical fiber sensors under the background of the rapid development of various optical materials. On the basis of retaining the original characteristics of the optical fiber sensors, the coated sensors are endowed with new characteristics, such as high sensitivity, strong structure, and specific recognition. Many materials with a large thermal optical coefficient and thermal expansion coefficients are applied to optical fibers, and the temperature sensitivities are improved several times after coating. At the same time, fiber sensors have more intelligent sensing capabilities when coated with specific recognition materials. The same/different kinds of materials combined with the same/different fiber structures can produce different measurements, which is interesting. This paper summarizes and compares the fiber sensors treated by different coating materials. Full article
Show Figures

Graphical abstract

10 pages, 5035 KiB  
Article
Nonlinear Hydraulic Pressure Response of an Improved Fiber Tip Interferometric High-Pressure Sensor
by Wei Huang, Zhe Zhang, Jun He, Bin Du, Changrui Liao, Shen Liu, Guolu Yin and Yiping Wang
Sensors 2020, 20(9), 2548; https://0-doi-org.brum.beds.ac.uk/10.3390/s20092548 - 30 Apr 2020
Cited by 7 | Viewed by 2221
Abstract
We demonstrate a silica diaphragm-based fiber tip Fabry–Perot interferometer (FPI) for high-pressure (40 MPa) sensing. By using a fiber tip polishing technique, the thickness of the silica diaphragm could be precisely controlled and the pressure sensitivity of the fabricated FPI sensor was enhanced [...] Read more.
We demonstrate a silica diaphragm-based fiber tip Fabry–Perot interferometer (FPI) for high-pressure (40 MPa) sensing. By using a fiber tip polishing technique, the thickness of the silica diaphragm could be precisely controlled and the pressure sensitivity of the fabricated FPI sensor was enhanced significantly by reducing the diaphragm thickness; however, the relationship between the pressure sensitivity and diaphragm thickness is not linear. A high sensitivity of −1.436 nm/MPa and a linearity of 0.99124 in hydraulic pressure range of 0 to 40 MPa were demonstrated for a sensor with a diaphragm thickness of 4.63 μm. The achieved sensitivity was about one order of magnitude higher than the previous results reported on similar fiber tip FPI sensors in the same pressure measurement range. Sensors with a thinner silica diaphragm (i.e., 4.01 and 2.09 μm) rendered further increased hydraulic pressure sensitivity, but yield a significant nonlinear response. Two geometric models and a finite element method (FEM) were carried out to explain the nonlinear response. The simulation results indicated the formation of cambered internal silica surface during the arc discharge process in the fiber tip FPI sensor fabrication. Full article
Show Figures

Figure 1

10 pages, 8722 KiB  
Article
Rapid Yeast Cell Viability Analysis by Using a Portable Microscope Based on the Fiber Optic Array and Simple Image Processing
by Weiming Wang, Hang Liu, Yan Yu, Fengyu Cong and Jun Yu
Sensors 2020, 20(7), 2092; https://0-doi-org.brum.beds.ac.uk/10.3390/s20072092 - 08 Apr 2020
Cited by 3 | Viewed by 2763
Abstract
A fiber optic array (FOA) can be used as an alternative or a supplement to the lens in a microscope due to its large magnification, high coupling efficiency and extremely low distortion. Based on our previous research, this paper first demonstrated the resolution [...] Read more.
A fiber optic array (FOA) can be used as an alternative or a supplement to the lens in a microscope due to its large magnification, high coupling efficiency and extremely low distortion. Based on our previous research, this paper first demonstrated the resolution and field-of-view (FOV) of the microscope based on the FOA. To further validate the FOA microscope’s imaging capability, yeast activity and concentration were investigated by simple image processing. The results showed that the percentages of live and dead yeast cells correctly identified were 92.1% and 84.8%, except for the clusters, which agreed well with the manual counting methods. Then, the performances of the portable microscopes based on the FOA and lens were compared and the factors that affect the FOA microscope imaging performance were analyzed. Full article
Show Figures

Figure 1

Back to TopTop