E-Mail Alert

Add your e-mail address to receive forthcoming issues of this journal:

Journal Browser

Journal Browser

Special Issue "Optical Fiber Sensors 2017"

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

Deadline for manuscript submissions: closed (15 January 2018)

Special Issue Editors

Guest Editor
Dr. Alexandre François

School of Engineering, University of South Australia, Adelaide, Australia and the Institute for Photonics and Advanced Sensing (IPAS), School of Physical Sciences, The University of Adelaide, Adelaide, Australia
Website | E-Mail
Phone: +61 (0) 8 830 23546
Interests: optics spectroscopy; label free optical biosensors; plasmonics; whispering gallery modes; surface functionalization; immunoassays; point of care diagnostics
Guest Editor
Prof. David Lancaster

School of Engineering and the Future Industries Institute, University of South Australia, Adelaide, Australia
Website | E-Mail
Phone: +61 (0) 8 830 25538
Interests: photonic sensors and devices, laser physics, guided-wave lasers, ultra-fast laser materials processing, optical spectroscopy
Guest Editor
Dr. Nicolas Riesen

School of Engineering, University of South Australia, Adelaide, Australia and Institute for Photonics and Advanced Sensing, School of Physical Sciences, The University of Adelaide, Adelaide, Australia
Website | E-Mail
Phone: +61 (0) 8 831 30871
Interests: optical microcavities; whispering gallery modes; distributed fiber sensing; nonlinear optics; optical waveguide theory; integrated optics

Special Issue Information

Dear Colleagues,

Optical fiber sensors have been used for a considerable period of time, yet they are still an exciting and dynamic research field with a wide range of new and emerging applications. The aim of this Special Issue is to reflect on the latest improvements in optical fiber sensor technologies, encompassing the diverse range of architectures, sensing mechanisms and applications.

We invite manuscripts for this forthcoming Special Issue entitled “Optical Fiber Sensors 2017”, in all aspects pertinent to fiber sensors. Both reviews and original research articles are welcome. Reviews should provide an up-to-date and critical overview of state-of-the-art technologies in the following research fields applied to fiber sensors:

  • Physical, mechanical, and electromagnetic sensors
  • Chemical, environmental, biological and medical sensors and bio photonics
  • Interferometric and polarimetric sensors including gyroscopes
  • Micro- and nano-structured fiber sensors including photonic crystal fibers and gratings sensors
  • Multiplexing and sensor networking
  • Distributed sensing
  • Smart structures and sensors including Bragg gratings, Fabry Perot cavities, plasmonic and Mach Zehnder interferometer.
  • New concepts for photonic sensing

If you have any suggestions that you would like to discuss beforehand, please feel free to contact us. We look
forward to and welcome your participation in this special issue.

Dr. Alexandre François
Prof. David Lancaster
Dr. Nicolas Riesen
Guest Editors

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 papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue 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 monthly 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 1800 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.

Published Papers (27 papers)

View options order results:
result details:
Displaying articles 1-27
Export citation of selected articles as:

Research

Jump to: Review

Open AccessArticle Fused Microknot Optical Resonators in Folded Photonic Tapers for in-Liquid Durable Sensing
Sensors 2018, 18(5), 1352; https://doi.org/10.3390/s18051352
Received: 4 March 2018 / Revised: 2 April 2018 / Accepted: 19 April 2018 / Published: 26 April 2018
PDF Full-text (764 KB) | HTML Full-text | XML Full-text
Abstract
Optical microknot fibers (OMFs) serve as localized devices, where photonic resonances (PRs) enable self-interfering elements sensitive to their environment. However, typical fragility and drifting of the knot severely limit the performance and durability of microknots as sensors in aqueous settings. Herein we present
[...] Read more.
Optical microknot fibers (OMFs) serve as localized devices, where photonic resonances (PRs) enable self-interfering elements sensitive to their environment. However, typical fragility and drifting of the knot severely limit the performance and durability of microknots as sensors in aqueous settings. Herein we present the fabrication, electrical fusing, preparation, and persistent detection of volatile liquids in multiple wetting–dewetting cycles of volatile compounds and quantify the persistent phase shifts with a simple model relating to the ambient liquid, enabling durable in-liquid sensing employing OMF PRs. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2017)
Figures

Figure 1

Open AccessArticle Discrimination of Temperature and Strain in Brillouin Optical Time Domain Analysis Using a Multicore Optical Fiber
Sensors 2018, 18(4), 1176; https://doi.org/10.3390/s18041176
Received: 6 March 2018 / Revised: 6 April 2018 / Accepted: 9 April 2018 / Published: 12 April 2018
PDF Full-text (5058 KB) | HTML Full-text | XML Full-text
Abstract
Brillouin optical time domain analysis is the sensing of temperature and strain changes along an optical fiber by measuring the frequency shift changes of Brillouin backscattering. Because frequency shift changes are a linear combination of temperature and strain changes, their discrimination is a
[...] Read more.
Brillouin optical time domain analysis is the sensing of temperature and strain changes along an optical fiber by measuring the frequency shift changes of Brillouin backscattering. Because frequency shift changes are a linear combination of temperature and strain changes, their discrimination is a challenge. Here, a multicore optical fiber that has two cores is fabricated. The differences between the cores’ temperature and strain coefficients are such that temperature (strain) changes can be discriminated with error amplification factors of 4.57 °C/MHz (69.11 μ ϵ /MHz), which is 2.63 (3.67) times lower than previously demonstrated. As proof of principle, using the multicore optical fiber and a commercial Brillouin optical time domain analyzer, the temperature (strain) changes of a thermally expanding metal cylinder are discriminated with an error of 0.24% (3.7%). Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2017)
Figures

Figure 1

Open AccessArticle Soil Water Measurement Using Actively Heated Fiber Optics at Field Scale
Sensors 2018, 18(4), 1116; https://doi.org/10.3390/s18041116
Received: 4 February 2018 / Revised: 28 March 2018 / Accepted: 2 April 2018 / Published: 6 April 2018
PDF Full-text (44588 KB) | HTML Full-text | XML Full-text
Abstract
Several studies have demonstrated the potential of actively heated fiber optics (AHFO) to measure soil water content (SWC) at high spatial and temporal resolutions. This study tested the feasibility of the AHFO technique to measure soil water in the surface soil of a
[...] Read more.
Several studies have demonstrated the potential of actively heated fiber optics (AHFO) to measure soil water content (SWC) at high spatial and temporal resolutions. This study tested the feasibility of the AHFO technique to measure soil water in the surface soil of a crop grown field over a growing season using an in-situ calibration approach. Heat pulses of five minutes duration were applied at a rate of 7.28 W m−1 along eighteen fiber optic cable transects installed at three depths (0.05, 0.10 and 0.20 m) at six-hour intervals. Cumulative temperature increase (Tcum) during heat pulses was calculated at locations along the cable. While predicting commercial sensor measurements, the AHFO showed root mean square errors (RMSE) of 2.8, 3.7 and 3.7% for 0.05, 0.10 and 0.20 m depths, respectively. Further, the coefficients of determination (R2) for depth specific relationships were 0.87 (0.05 m depth), 0.46 (0.10 m depth), 0.86 (0.20 m depth) and 0.66 (all depths combined). This study showed a great potential of the AHFO technique to measure soil water at high spatial resolutions (<1 m) and to monitor soil water dynamics of surface soil in a crop grown field over a cropping season with a reasonable compromise between accuracy and practicality. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2017)
Figures

Figure 1

Open AccessArticle Embedded Distributed Optical Fiber Sensors in Reinforced Concrete Structures—A Case Study
Sensors 2018, 18(4), 980; https://doi.org/10.3390/s18040980
Received: 13 January 2018 / Revised: 7 March 2018 / Accepted: 22 March 2018 / Published: 26 March 2018
PDF Full-text (85745 KB) | HTML Full-text | XML Full-text
Abstract
When using distributed optical fiber sensors (DOFS) on reinforced concrete structures, a compromise must be achieved between the protection requirements and robustness of the sensor deployment and the accuracy of the measurements both in the uncracked and cracked stages and under loading, unloading
[...] Read more.
When using distributed optical fiber sensors (DOFS) on reinforced concrete structures, a compromise must be achieved between the protection requirements and robustness of the sensor deployment and the accuracy of the measurements both in the uncracked and cracked stages and under loading, unloading and reloading processes. With this in mind the authors have carried out an experiment where polyimide-coated DOFS were installed on two concrete beams, both embedded in the rebar elements and also bonded to the concrete surface. The specimens were subjected to a three-point load test where after cracking, they are unloaded and reloaded again to assess the capability of the sensor when applied to a real loading scenarios in concrete structures. Rayleigh Optical Frequency Domain Reflectometry (OFDR) was used as the most suitable technique for crack detection in reinforced concrete elements. To verify the reliability and accuracy of the DOFS measurements, additional strain gauges were also installed at three locations along the rebar. The results show the feasibility of using a thin coated polyimide DOFS directly bonded on the reinforcing bar without the need of indention or mechanization. A proposal for a Spectral Shift Quality (SSQ) threshold is also obtained and proposed for future works when using polyimide-coated DOFS bonded to rebars with cyanoacrylate adhesive. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2017)
Figures

Figure 1

Open AccessArticle Two-Dimensional Layered Nanomaterial-Based One-Dimensional Photonic Crystal Refractive Index Sensor
Sensors 2018, 18(3), 857; https://doi.org/10.3390/s18030857
Received: 16 January 2018 / Revised: 3 March 2018 / Accepted: 8 March 2018 / Published: 14 March 2018
Cited by 1 | PDF Full-text (1234 KB) | HTML Full-text | XML Full-text
Abstract
One-dimensional photonic crystal (1DPC) sensors have emerged as contenders for traditional surface plasmon resonance sensors, owing to their potential for the detection of bigger molecules and particles due to their higher interaction volume in the sensing medium. Two-dimensional layered nanomaterials, most notably graphene
[...] Read more.
One-dimensional photonic crystal (1DPC) sensors have emerged as contenders for traditional surface plasmon resonance sensors, owing to their potential for the detection of bigger molecules and particles due to their higher interaction volume in the sensing medium. Two-dimensional layered nanomaterials, most notably graphene and dichalcogenides (e.g., MoS2, MoSe2, WS2, and WSe2), have shown higher refractive index sensitivity because of their absorption as well as adsorption property. The proposed configuration of 1DPC presented consists of alternate layers of the aforementioned nanomaterials and silicon. The performance parameters, namely the sensitivity, resolution, quality factor, and the evanescent field penetration depth, are calculated and compared with 1DPC having poly methyl methacrylate (PMMA) in place of silicon. Increased shift in resonance angle and quality factor are observed by replacing PMMA with silicon, but at the cost of decreased resolution. Further, our results show that although the sensitivity and quality factor of the 1DPC sensor is less than that of the conventional surface plasmon resonance sensor (SPR) with a gold thin film, it has much higher resolution and penetration depth to make it suitable for large molecules. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2017)
Figures

Figure 1

Open AccessArticle Detection of Internal Metal Loss in Steel Pipes and Storage Tanks via Magnetic-Based Fiber Optic Sensor
Sensors 2018, 18(3), 815; https://doi.org/10.3390/s18030815
Received: 11 January 2018 / Revised: 5 March 2018 / Accepted: 6 March 2018 / Published: 8 March 2018
PDF Full-text (3168 KB) | HTML Full-text | XML Full-text
Abstract
A monitoring solution was developed for detection of material loss in metals such as carbon steel using the force generated by permanent magnets in addition to the optical strain sensing technology. The working principle of the sensing system is related to the change
[...] Read more.
A monitoring solution was developed for detection of material loss in metals such as carbon steel using the force generated by permanent magnets in addition to the optical strain sensing technology. The working principle of the sensing system is related to the change in thickness of a steel plate, which typically occurs due to corrosion. As thickness decreases, the magnetostatic force between the magnet and the steel structure also decreases. This, in turn, affects the strain measured using the optical fiber. The sensor prototype was designed and built after verifying its sensitivity using a numerical model. The prototype was tested on steel plates of different thicknesses to establish the relationship between the metal thickness and measured strain. The results of experiments and numerical models demonstrate a strong relationship between the metal thickness and the measured strain values. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2017)
Figures

Figure 1

Open AccessArticle Modeling and Analysis of a Combined Stress-Vibration Fiber Bragg Grating Sensor
Sensors 2018, 18(3), 743; https://doi.org/10.3390/s18030743
Received: 7 February 2018 / Revised: 24 February 2018 / Accepted: 26 February 2018 / Published: 1 March 2018
Cited by 1 | PDF Full-text (9155 KB) | HTML Full-text | XML Full-text
Abstract
A combined stress-vibration sensor was developed to measure stress and vibration simultaneously based on fiber Bragg grating (FBG) technology. The sensor is composed of two FBGs and a stainless steel plate with a special design. The two FBGs sense vibration and stress and
[...] Read more.
A combined stress-vibration sensor was developed to measure stress and vibration simultaneously based on fiber Bragg grating (FBG) technology. The sensor is composed of two FBGs and a stainless steel plate with a special design. The two FBGs sense vibration and stress and the sensor can realize temperature compensation by itself. The stainless steel plate can significantly increase sensitivity of vibration measurement. Theoretical analysis and Finite Element Method (FEM) were used to analyze the sensor’s working mechanism. As demonstrated with analysis, the obtained sensor has working range of 0–6000 Hz for vibration sensing and 0–100 MPa for stress sensing, respectively. The corresponding sensitivity for vibration is 0.46 pm/g and the resulted stress sensitivity is 5.94 pm/MPa, while the nonlinearity error for vibration and stress measurement is 0.77% and 1.02%, respectively. Compared to general FBGs, the vibration sensitivity of this sensor is 26.2 times higher. Therefore, the developed sensor can be used to concurrently detect vibration and stress. As this sensor has height of 1 mm and weight of 1.15 g, it is beneficial for minimization and integration. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2017)
Figures

Figure 1

Open AccessArticle Fiber-Optic Pyrometer with Optically Powered Switch for Temperature Measurements
Sensors 2018, 18(2), 483; https://doi.org/10.3390/s18020483
Received: 28 December 2017 / Revised: 26 January 2018 / Accepted: 1 February 2018 / Published: 6 February 2018
Cited by 1 | PDF Full-text (1770 KB) | HTML Full-text | XML Full-text
Abstract
We report the experimental results on a new infrared fiber-optic pyrometer for very localized and high-speed temperature measurements ranging from 170 to 530 °C using low-noise photodetectors and high-gain transimpedance amplifiers with a single gain mode in the whole temperature range. We also
[...] Read more.
We report the experimental results on a new infrared fiber-optic pyrometer for very localized and high-speed temperature measurements ranging from 170 to 530 °C using low-noise photodetectors and high-gain transimpedance amplifiers with a single gain mode in the whole temperature range. We also report a shutter based on an optical fiber switch which is optically powered to provide a reference signal in an optical fiber pyrometer measuring from 200 to 550 °C. The tests show the potential of remotely powering via optical means a 300 mW power-hungry optical switch at a distance of 100 m, avoiding any electromagnetic interference close to the measuring point. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2017)
Figures

Figure 1

Open AccessArticle Overhead Transmission Line Sag Estimation Using a Simple Optomechanical System with Chirped Fiber Bragg Gratings. Part 1: Preliminary Measurements
Sensors 2018, 18(1), 309; https://doi.org/10.3390/s18010309
Received: 27 November 2017 / Revised: 14 January 2018 / Accepted: 18 January 2018 / Published: 20 January 2018
Cited by 3 | PDF Full-text (4686 KB) | HTML Full-text | XML Full-text
Abstract
A method of measuring the power line wire sag using optical sensors that are insensitive to high electromagnetic fields was proposed. The advantage of this technique is that it is a non-invasive measurement of power line wire elongation using a unique optomechanical system.
[...] Read more.
A method of measuring the power line wire sag using optical sensors that are insensitive to high electromagnetic fields was proposed. The advantage of this technique is that it is a non-invasive measurement of power line wire elongation using a unique optomechanical system. The proposed method replaces the sag of the power line wire with an extension of the control sample and then an expansion of the attached chirped fiber Bragg grating. This paper presents the results of the first measurements made on real aluminum-conducting steel-reinforced wire, frequently used for power line construction. It has been shown that the proper selection of the CFBG (chirped fiber Bragg grating) transducer and the appropriate choice of optical parameters of such a sensor will allow for high sensitivity of the line wire elongation and sag while reducing the sensitivity to the temperature. It has been shown that with a simple optomechanical system, a non-invasive measurement of the power line wire sag that is insensitive to temperature changes and the influence of high electromagnetic fields can be achieved. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2017)
Figures

Figure 1

Open AccessArticle Fabry-Perot Interferometric High-Temperature Sensing Up to 1200 °C Based on a Silica Glass Photonic Crystal Fiber
Sensors 2018, 18(1), 273; https://doi.org/10.3390/s18010273
Received: 18 December 2017 / Revised: 14 January 2018 / Accepted: 14 January 2018 / Published: 18 January 2018
PDF Full-text (3306 KB) | HTML Full-text | XML Full-text
Abstract
A Fabry-Perot interferometric sensor for temperature measurement was fabricated based on a silica glass solid-core photonic crystal fiber with a central air-bore. By splicing a stub of photonic crystal fiber to a standard single-mode fiber, an intrinsic Fabry-Perot cavity was formed inside the
[...] Read more.
A Fabry-Perot interferometric sensor for temperature measurement was fabricated based on a silica glass solid-core photonic crystal fiber with a central air-bore. By splicing a stub of photonic crystal fiber to a standard single-mode fiber, an intrinsic Fabry-Perot cavity was formed inside the photonic crystal fiber. Sensing experiment results show that the sensor can work stably for a consecutive 24 h under temperatures up to 1100 °C, and the short-term operation temperature can reach as high as 1200 °C (<30 min). In the measurement range of 300–1200 °C, the temperature sensitivity of the peak wavelength shift can reach as high as 15.61 pm/°C, with a linearity of 99.76%. The presented interferometric sensor is compact in size and possesses advantages such as an extended working range and high sensitivity, showing promising application prospects. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2017)
Figures

Figure 1

Open AccessArticle High-Temperature Sensor Based on Fabry-Perot Interferometer in Microfiber Tip
Sensors 2018, 18(1), 202; https://doi.org/10.3390/s18010202
Received: 13 December 2017 / Revised: 6 January 2018 / Accepted: 8 January 2018 / Published: 12 January 2018
Cited by 1 | PDF Full-text (3711 KB) | HTML Full-text | XML Full-text
Abstract
A miniaturized tip Fabry-Perot interferometer (tip-FPI) is proposed for high-temperature sensing. It is simply fabricated for the first time by splicing a short length of microfiber (MF) to the cleaved end of a standard single mode fiber (SMF) with precise control of the
[...] Read more.
A miniaturized tip Fabry-Perot interferometer (tip-FPI) is proposed for high-temperature sensing. It is simply fabricated for the first time by splicing a short length of microfiber (MF) to the cleaved end of a standard single mode fiber (SMF) with precise control of the relative cross section position. Such a MF acts as a Fabry-Perot (FP) cavity and serves as a tip sensor. A change in temperature modifies the length and refractive index of the FP cavity, and then a corresponding change in the reflected interference spectrum can be observed. High temperatures of up to 1000 °C are measured in the experiments, and a high sensitivity of 13.6 pm/°C is achieved. This compact sensor, with tip diameter and length both of tens of microns, is suitable for localized detection, especially in harsh environments. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2017)
Figures

Figure 1

Open AccessArticle Optical Fiber Demodulation System with High Performance for Assessing Fretting Damage of Steam Generator Tubes
Sensors 2018, 18(1), 201; https://doi.org/10.3390/s18010201
Received: 12 November 2017 / Revised: 5 January 2018 / Accepted: 9 January 2018 / Published: 12 January 2018
PDF Full-text (6197 KB) | HTML Full-text | XML Full-text
Abstract
In order to access the fretting damage of the steam generator tube (SGT), a fast fiber Fabry-Perot (F-P) non-scanning correlation demodulation system based on a super luminescent light emitting diode (SLED) was performed. By demodulating the light signal coming out from the F-P
[...] Read more.
In order to access the fretting damage of the steam generator tube (SGT), a fast fiber Fabry-Perot (F-P) non-scanning correlation demodulation system based on a super luminescent light emitting diode (SLED) was performed. By demodulating the light signal coming out from the F-P force sensor, the radial collision force between the SGT and the tube support plate (TSP) was interrogated. For higher demodulation accuracy, the effects of the center wavelength, bandwidth, and spectrum noise of SLED were discussed in detail. Specially, a piezoelectric ceramic transducer (PZT) modulation method was developed to get rid of the interference of mode coupling induced by different types of fiber optics in the demodulation system. The reflectivity of optical wedge and F-P sensor was optimized. Finally, the demodulation system worked well in a 1:1 steam generator test loop and successfully demodulated a force signal of 32 N with a collision time of 2 ms. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2017)
Figures

Figure 1

Open AccessArticle Graphene Oxide in Lossy Mode Resonance-Based Optical Fiber Sensors for Ethanol Detection
Sensors 2018, 18(1), 58; https://doi.org/10.3390/s18010058
Received: 11 December 2017 / Revised: 16 December 2017 / Accepted: 22 December 2017 / Published: 27 December 2017
PDF Full-text (2796 KB) | HTML Full-text | XML Full-text
Abstract
The influence of graphene oxide (GO) over the features of an optical fiber ethanol sensor based on lossy mode resonances (LMR) has been studied in this work. Four different sensors were built with this aim, each comprising a multimode optical fiber core fragment
[...] Read more.
The influence of graphene oxide (GO) over the features of an optical fiber ethanol sensor based on lossy mode resonances (LMR) has been studied in this work. Four different sensors were built with this aim, each comprising a multimode optical fiber core fragment coated with a SnO2 thin film. Layer by layer (LbL) coatings made of 1, 2 and 4 bilayers of polyethyleneimine (PEI) and graphene oxide were deposited onto three of these devices and their behavior as aqueous ethanol sensors was characterized and compared with the sensor without GO. The sensors with GO showed much better performance with a maximum sensitivity enhancement of 176% with respect to the sensor without GO. To our knowledge, this is the first time that GO has been used to make an optical fiber sensor based on LMR. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2017)
Figures

Figure 1

Open AccessArticle Fiber-Optic Sensor-Based Remote Acoustic Emission Measurement in a 1000 °C Environment
Sensors 2017, 17(12), 2908; https://doi.org/10.3390/s17122908
Received: 11 October 2017 / Revised: 27 November 2017 / Accepted: 12 December 2017 / Published: 14 December 2017
PDF Full-text (5606 KB) | HTML Full-text | XML Full-text
Abstract
Recently, the authors have proposed a remote acoustic emission (AE) measurement configuration using a sensitive fiber-optic Bragg grating (FBG) sensor. In the configuration, the FBG sensor was remotely bonded on a plate, and an optical fiber was used as the waveguide to propagate
[...] Read more.
Recently, the authors have proposed a remote acoustic emission (AE) measurement configuration using a sensitive fiber-optic Bragg grating (FBG) sensor. In the configuration, the FBG sensor was remotely bonded on a plate, and an optical fiber was used as the waveguide to propagate AE waves from the adhesive point to the sensor. The previous work (Yu et al., Smart Materials and Structures 25 (10), 105,033 (2016)) has clarified the sensing principle behind the special remote measurement system that enables accurate remote sensing of AE signals. Since the silica-glass optical fibers have a high heat-resistance exceeding 1000 °C, this work presents a preliminary high-temperature AE detection method by using the optical fiber-based ultrasonic waveguide to propagate the AE from a high-temperature environment to a room-temperature environment, in which the FBG sensor could function as the receiver of the guided wave. As a result, the novel measurement configuration successfully achieved highly sensitive and stable AE detection in an alumina plate at elevated temperatures in the 100 °C to 1000 °C range. Due to its good performance, this detection method will be potentially useful for the non-destructive testing that can be performed in high-temperature environments to evaluate the microscopic damage in heat-resistant materials. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2017)
Figures

Figure 1

Open AccessArticle Low Cost Plastic Optical Fiber Pressure Sensor Embedded in Mattress for Vital Signal Monitoring
Sensors 2017, 17(12), 2900; https://doi.org/10.3390/s17122900
Received: 30 October 2017 / Revised: 4 December 2017 / Accepted: 8 December 2017 / Published: 13 December 2017
PDF Full-text (3726 KB) | HTML Full-text | XML Full-text
Abstract
The aim of this paper is to report the design of a low-cost plastic optical fiber (POF) pressure sensor, embedded in a mattress. We report the design of a multipoint sensor, a cheap alternative to the most common fiber sensors. The sensor is
[...] Read more.
The aim of this paper is to report the design of a low-cost plastic optical fiber (POF) pressure sensor, embedded in a mattress. We report the design of a multipoint sensor, a cheap alternative to the most common fiber sensors. The sensor is implemented using Arduino board, standard LEDs for optical communication in POF (λ = 645 nm) and a silicon light sensor. The Super ESKA® plastic fibers were used to implement the fiber intensity sensor, arranged in a 4 × 4 matrix. During the breathing cycles, the force transmitted from the lungs to the thorax is in the order of tens of Newtons, and the respiration rate is of one breath every 2–5 s (0.2–0.5 Hz). The sensor has a resolution of force applied on a single point of 2.2–4.5%/N on the normalized voltage output, and a bandwidth of 10 Hz, it is then suitable to monitor the respiration movements. Another issue to be addressed is the presence of hysteresis over load cycles. The sensor was loaded cyclically to estimate the drift of the system, and the hysteresis was found to be negligible. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2017)
Figures

Figure 1

Open AccessArticle Fiber Fabry-Perot Force Sensor with Small Volume and High Performance for Assessing Fretting Damage of Steam Generator Tubes
Sensors 2017, 17(12), 2899; https://doi.org/10.3390/s17122899
Received: 29 October 2017 / Revised: 28 November 2017 / Accepted: 11 December 2017 / Published: 13 December 2017
Cited by 1 | PDF Full-text (5147 KB) | HTML Full-text | XML Full-text
Abstract
Measuring the radial collision force between the steam generator tube (SGT) and the tube support plate (TSP) is essential to assess the fretting damage of the SGT. In order to measure the radial collision force, a novel miniaturized force sensor based on fiber
[...] Read more.
Measuring the radial collision force between the steam generator tube (SGT) and the tube support plate (TSP) is essential to assess the fretting damage of the SGT. In order to measure the radial collision force, a novel miniaturized force sensor based on fiber Fabry-Perot (F-P) was designed, and the principle and characteristics of the sensor were analyzed in detail. Then, the F-P force sensor was successfully fabricated and calibrated, and the overall dimensions of the encapsulated fiber F-P sensor were 17 mm × 5 mm × 3 mm (L × W × H). The sensor works well in humid, high pressure (10 MPa), high temperature (350 °C), and vibration (40 kHz) environments. Finally, the F-P force sensors were installed in a 1:1 steam generator test loop, and the radial collision force signals between the SGT and the TSP were obtained. The experiments indicated that the F-P sensor with small volume and high performance could help in assessing the fretting damage of the steam generator tubes. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2017)
Figures

Figure 1

Open AccessArticle Two Interrogated FBG Spectral Linewidth for Strain Sensing through Correlation
Sensors 2017, 17(12), 2837; https://doi.org/10.3390/s17122837
Received: 6 October 2017 / Revised: 20 November 2017 / Accepted: 1 December 2017 / Published: 7 December 2017
PDF Full-text (1196 KB) | HTML Full-text | XML Full-text
Abstract
The spectral linewidth from two cross-correlated fiber Bragg gratings (FBGs) are interrogated and characterized using a delayed self-homodyne method for fiber strain sensing. This approach employs a common higher frequency resolution instead of wavelength. A sensitivity and resolution of 166 MHz/με and 50
[...] Read more.
The spectral linewidth from two cross-correlated fiber Bragg gratings (FBGs) are interrogated and characterized using a delayed self-homodyne method for fiber strain sensing. This approach employs a common higher frequency resolution instead of wavelength. A sensitivity and resolution of 166 MHz/με and 50 nε were demonstrated from 4 GHz spectral linewidth characterization on the electric spectrum analyzer. A 10 nε higher resolution can be expected through random noise analyses when the spectral linewidth from two FBG correlations is reduced to 1 GHz. Moreover, the FBG spectrum is broadened during strain and experimentally shows a 0.44 pm/με sensitivity, which is mainly caused by the photo elastic effect from the fiber grating period stretch. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2017)
Figures

Figure 1

Open AccessArticle All-Fiber Laser Curvature Sensor Using an In-Fiber Modal Interferometer Based on a Double Clad Fiber and a Multimode Fiber Structure
Sensors 2017, 17(12), 2744; https://doi.org/10.3390/s17122744
Received: 28 September 2017 / Revised: 31 October 2017 / Accepted: 7 November 2017 / Published: 28 November 2017
Cited by 1 | PDF Full-text (6346 KB) | HTML Full-text | XML Full-text
Abstract
An all-fiber curvature laser sensor by using a novel modal interference in-fiber structure is proposed and experimentally demonstrated. The in-fiber device, fabricated by fusion splicing of multimode fiber and double-clad fiber segments, is used as wavelength filter as well as the sensing element.
[...] Read more.
An all-fiber curvature laser sensor by using a novel modal interference in-fiber structure is proposed and experimentally demonstrated. The in-fiber device, fabricated by fusion splicing of multimode fiber and double-clad fiber segments, is used as wavelength filter as well as the sensing element. By including a multimode fiber in an ordinary modal interference structure based on a double-clad fiber, the fringe visibility of the filter transmission spectrum is significantly increased. By using the modal interferometer as a curvature sensitive wavelength filter within a ring cavity erbium-doped fiber laser, the spectral quality factor Q is considerably increased. The results demonstrate the reliability of the proposed curvature laser sensor with advantages of robustness, ease of fabrication, low cost, repeatability on the fabrication process and simple operation. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2017)
Figures

Figure 1

Open AccessArticle Assembled Cantilever Fiber Touch Trigger Probe for Three-Dimensional Measurement of Microstructures
Sensors 2017, 17(11), 2652; https://doi.org/10.3390/s17112652
Received: 17 October 2017 / Revised: 11 November 2017 / Accepted: 14 November 2017 / Published: 20 November 2017
PDF Full-text (13616 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, an assembled cantilever fiber touch trigger probe was developed for three-dimensional measurements of clear microstructures. The probe consists of a shaft assembled vertically to an optical fiber cantilever and a probing sphere located at the free end of the shaft.
[...] Read more.
In this paper, an assembled cantilever fiber touch trigger probe was developed for three-dimensional measurements of clear microstructures. The probe consists of a shaft assembled vertically to an optical fiber cantilever and a probing sphere located at the free end of the shaft. The laser is emitted from the free end of the fiber cantilever and converges on the photosensitive surface of the camera through the lens. The position shift of the light spot centroid was used to detect the performance of the optical fiber cantilever, which changed dramatically when the probing sphere touched the objects being measured. Experimental results indicated that the sensing system has sensitivities of 3.32 pixels/μm, 1.35 pixels/μm, and 7.38 pixels/μm in the x, y, and z directions, respectively, and resolutions of 10 nm, 30 nm, and 5 nm were achieved in the x, y, and z, respectively. An experiment on micro slit measurement was performed to verify the high aspect ratio measurement capability of the assembled cantilever fiber (ACF) probe and to calibrate the effective two-point diameter of the probing sphere. The two-point probe sphere diameter was found to be 174.634 μm with a standard uncertainly of 0.045 μm. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2017)
Figures

Figure 1

Open AccessArticle Optical Spring Effect in Micro-Bubble Resonators and Its Application for the Effective Mass Measurement of Optomechanical Resonant Mode
Sensors 2017, 17(10), 2256; https://doi.org/10.3390/s17102256
Received: 12 July 2017 / Revised: 21 September 2017 / Accepted: 26 September 2017 / Published: 30 September 2017
PDF Full-text (1866 KB) | HTML Full-text | XML Full-text
Abstract
In this work, we present a novel approach for obtaining the effective mass of mechanical vibration mode in micro-bubble resonators (MBRs). To be specific, the effective mass is deduced from the measurement of optical spring effect (OSE) in MBRs. This approach is demonstrated
[...] Read more.
In this work, we present a novel approach for obtaining the effective mass of mechanical vibration mode in micro-bubble resonators (MBRs). To be specific, the effective mass is deduced from the measurement of optical spring effect (OSE) in MBRs. This approach is demonstrated and applied to analyze the effective mass of hollow MBRs and liquid-filled MBRs, respectively. It is found that the liquid-filled MBRs has significantly stronger OSE and a less effective mass than hollow MBRs, both of the extraordinary behaviors can be beneficial for applications such as mass sensing. Larger OSE from higher order harmonics of the mechanical modes is also observed. Our work paves a way towards the developing of OSE-based high sensitive mass sensor in MBRs. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2017)
Figures

Figure 1

Open AccessArticle A Hot-Polymer Fiber Fabry–Perot Interferometer Anemometer for Sensing Airflow
Sensors 2017, 17(9), 2015; https://doi.org/10.3390/s17092015
Received: 9 August 2017 / Revised: 30 August 2017 / Accepted: 1 September 2017 / Published: 2 September 2017
Cited by 5 | PDF Full-text (3926 KB) | HTML Full-text | XML Full-text
Abstract
This work proposes the first hot-polymer fiber Fabry–Perot interferometer (HPFFPI) anemometer for sensing airflow. The proposed HPFFPI is based on a single-mode fiber (SMF) endface that is attached to a UV-cured polymer to form an ultracompact fiber Fabry–Perot microcavity. The proposed polymer microcavity
[...] Read more.
This work proposes the first hot-polymer fiber Fabry–Perot interferometer (HPFFPI) anemometer for sensing airflow. The proposed HPFFPI is based on a single-mode fiber (SMF) endface that is attached to a UV-cured polymer to form an ultracompact fiber Fabry–Perot microcavity. The proposed polymer microcavity was heated using a low-cost chip resistor with a controllable dc driving power to achieve a desired polymer’s steady-state temperature (T) that exceeds the T of the surrounding environment. The polymer is highly sensitive to variations of T with high repeatability. When the hot polymer was cooled by the measured flowing air, the wavelength fringes of its optical spectra shifted. The HPFFPI anemometers have been experimentally evaluated for different cavity lengths and heating power values. Experimental results demonstrate that the proposed HPFFPI responses well in terms of airflow measurement. A high sensitivity of 1.139 nm/(m/s) and a good resolution of 0.0088 m/s over the 0~2.54 m/s range of airflow were achieved with a cavity length of 10 μm and a heating power of 0.402 W. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2017)
Figures

Figure 1

Open AccessArticle Differential Phononic Crystal Sensor: Towards a Temperature Compensation Mechanism for Field Applications Development
Sensors 2017, 17(9), 1960; https://doi.org/10.3390/s17091960
Received: 11 May 2017 / Revised: 29 July 2017 / Accepted: 23 August 2017 / Published: 25 August 2017
Cited by 1 | PDF Full-text (1861 KB) | HTML Full-text | XML Full-text
Abstract
Phononic crystals are resonant structures with great potential to be implemented in applications as liquid sensors. The use of the symmetry reduction technique allows introducing relevant transmission features inside bandgaps by creating defect modes in a periodic regular structure. These features can be
[...] Read more.
Phononic crystals are resonant structures with great potential to be implemented in applications as liquid sensors. The use of the symmetry reduction technique allows introducing relevant transmission features inside bandgaps by creating defect modes in a periodic regular structure. These features can be used as measures to quantify changes in the speed of sound of liquid samples that could be related to the concentration of analytes or the presence of pathogens among other interesting applications. In order to be able to implement this new technology in more challenging applications, such as biomedical applications, it is necessary to have a very precise and accurate measurement. Changes in temperature greatly affect the speed of sound of the liquid samples, causing errors in the measurements. This article presents a phononic crystal sensor that, by introducing additional defect modes, can carry out differential measurements as a temperature compensation mechanism. Theoretical studies using the transmission line model and analytes at various temperatures show that the proposed temperature compensation mechanism enhances the performance of the sensor in a significant way. This temperature compensation strategy could also be implemented in crystals with different topologies. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2017)
Figures

Figure 1

Open AccessArticle Radiation-Induced Attenuation of Perfluorinated Polymer Optical Fibers for Radiation Monitoring
Sensors 2017, 17(9), 1959; https://doi.org/10.3390/s17091959
Received: 25 July 2017 / Revised: 22 August 2017 / Accepted: 24 August 2017 / Published: 25 August 2017
Cited by 2 | PDF Full-text (2767 KB) | HTML Full-text | XML Full-text
Abstract
Due to some of their unique properties, optical fiber dosimeters are attractive and extensively researched devices in several radiation-related areas. This work evaluates the performance and potential of commercial perfluorinated polymer optical fibers (PF-POFs) for radiation monitoring applications. Gamma radiation-induced attenuation (RIA) of
[...] Read more.
Due to some of their unique properties, optical fiber dosimeters are attractive and extensively researched devices in several radiation-related areas. This work evaluates the performance and potential of commercial perfluorinated polymer optical fibers (PF-POFs) for radiation monitoring applications. Gamma radiation-induced attenuation (RIA) of two commercial PF-POFs is evaluated in the VIS spectral region. Influence of a dose rate and temperature on RIA measurement is investigated, along with defect stability and measurement repeatability. Co-extruded PF-POFs are identified as more suitable for radiation monitoring applications due to lower dose-rate dependence. With co-extruded PF-POF, RIA measurement holds potential for highly-sensitive radiation monitoring with good reproducibility. The results show that operation in the blue part of the spectrum provides most favorable performance in terms of the largest nominal radiation sensitivity, lower temperature, and dose-rate dependence as well as higher defect stability. We demonstrate for the first time to our knowledge, that PF-POFs can be used for distributed detection of radiation with doses down to tens of Grays. The off-the-shelf, user-friendly PF-POF could be of interest as a cheap, disposable sensor for various applications, especially of a more qualitative nature. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2017)
Figures

Figure 1

Open AccessArticle Curvature and Temperature Measurement Based on a Few-Mode PCF Formed M-Z-I and an Embedded FBG
Sensors 2017, 17(8), 1725; https://doi.org/10.3390/s17081725
Received: 17 June 2017 / Revised: 15 July 2017 / Accepted: 24 July 2017 / Published: 27 July 2017
Cited by 1 | PDF Full-text (9073 KB) | HTML Full-text | XML Full-text
Abstract
We have experimentally demonstrated an optical fiber Mach-Zehnder interferometer (MZI) structure formed by a few-mode photonic crystal fiber (PCF) for curvature measurement and inscribed a fiber Bragg grating (FBG) in the PCF for the purpose of simultaneously measuring temperature. The structure consists of
[...] Read more.
We have experimentally demonstrated an optical fiber Mach-Zehnder interferometer (MZI) structure formed by a few-mode photonic crystal fiber (PCF) for curvature measurement and inscribed a fiber Bragg grating (FBG) in the PCF for the purpose of simultaneously measuring temperature. The structure consists of a PCF sandwiched between two multi-mode fibers (MMFs). Bending experimental results show that the proposed sensor has a sensitivity of −1.03 nm/m−1 at a curvature range from 10 m−1 to 22.4 m−1, and the curvature sensitivity of the embedded FBG was −0.003 nm/m−1. Temperature response experimental results showed that the MZI’s wavelength, λa, has a sensitivity of 60.3 pm/°C, and the FBG’s Bragg wavelength, λb, has sensitivity of 9.2 pm/°C in the temperature range of 8 to 100 °C. As such, it can be used for simultaneous measurement of curvature and temperature over ranges of 10 m−1 to 22.4 m−1 and 8 °C to 100 °C, respectively. The results show that the embedded FBG can be a good indicator to compensate the varying ambient temperature during a curvature measurement. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2017)
Figures

Figure 1

Review

Jump to: Research

Open AccessReview Distributed Optical Fiber Sensors Based on Optical Frequency Domain Reflectometry: A review
Sensors 2018, 18(4), 1072; https://doi.org/10.3390/s18041072
Received: 14 January 2018 / Revised: 30 March 2018 / Accepted: 30 March 2018 / Published: 3 April 2018
Cited by 1 | PDF Full-text (81980 KB) | HTML Full-text | XML Full-text
Abstract
Distributed optical fiber sensors (DOFS) offer unprecedented features, the most unique one of which is the ability of monitoring variations of the physical and chemical parameters with spatial continuity along the fiber. Among all these distributed sensing techniques, optical frequency domain reflectometry (OFDR)
[...] Read more.
Distributed optical fiber sensors (DOFS) offer unprecedented features, the most unique one of which is the ability of monitoring variations of the physical and chemical parameters with spatial continuity along the fiber. Among all these distributed sensing techniques, optical frequency domain reflectometry (OFDR) has been given tremendous attention because of its high spatial resolution and large dynamic range. In addition, DOFS based on OFDR have been used to sense many parameters. In this review, we will survey the key technologies for improving sensing range, spatial resolution and sensing performance in DOFS based on OFDR. We also introduce the sensing mechanisms and the applications of DOFS based on OFDR including strain, stress, vibration, temperature, 3D shape, flow, refractive index, magnetic field, radiation, gas and so on. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2017)
Figures

Figure 1

Open AccessReview Optical Fiber Sensors Based on Fiber Ring Laser Demodulation Technology
Sensors 2018, 18(2), 505; https://doi.org/10.3390/s18020505
Received: 31 December 2017 / Revised: 3 February 2018 / Accepted: 5 February 2018 / Published: 8 February 2018
PDF Full-text (3246 KB) | HTML Full-text | XML Full-text
Abstract
A review for optical fiber sensors based on fiber ring laser (FRL) demodulation technology is presented. The review focuses on the principles, main structures, and the sensing performances of different kinds of optical fiber sensors based on FRLs. First of all, the theory
[...] Read more.
A review for optical fiber sensors based on fiber ring laser (FRL) demodulation technology is presented. The review focuses on the principles, main structures, and the sensing performances of different kinds of optical fiber sensors based on FRLs. First of all, the theory background of the sensors has been discussed. Secondly, four different types of sensors are described and compared, which includes Mach–Zehnder interferometer (MZI) typed sensors, Fabry–Perot interferometer (FPI) typed sensors, Sagnac typed sensors, and fiber Bragg grating (FBG) typed sensors. Typical studies and main properties of each type of sensors are presented. Thirdly, a comparison of different types of sensors are made. Finally, the existing problems and future research directions are pointed out and analyzed. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2017)
Figures

Figure 1

Open AccessFeature PaperReview A Review of Microfiber-Based Temperature Sensors
Sensors 2018, 18(2), 461; https://doi.org/10.3390/s18020461
Received: 20 January 2018 / Revised: 31 January 2018 / Accepted: 1 February 2018 / Published: 4 February 2018
PDF Full-text (8896 KB) | HTML Full-text | XML Full-text
Abstract
Optical microfiber-based temperature sensors have been proposed for many applications in a variety of industrial uses, including biomedical, geological, automotive, and defense applications. This increasing demand for these micrometric devices is attributed to their large dynamic range, high sensitivity, fast-response, compactness and robustness.
[...] Read more.
Optical microfiber-based temperature sensors have been proposed for many applications in a variety of industrial uses, including biomedical, geological, automotive, and defense applications. This increasing demand for these micrometric devices is attributed to their large dynamic range, high sensitivity, fast-response, compactness and robustness. Additionally, they can perform in-situ measurements remotely and in harsh environments. This paper presents an overview of optical microfibers, with a focus on their applications in temperature sensing. This review broadly divides microfiber-based temperature sensors into two categories: resonant and non-resonant microfiber sensors. While the former includes microfiber loop, knot and coil resonators, the latter comprises sensors based on functionally coated/doped microfibers, microfiber couplers, optical gratings and interferometers. In the conclusions, a summary of reported performances is presented. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2017)
Figures

Figure 1

Back to Top