Showing papers on "Fiber optic sensor published in 2022"

Label-free plasmonic immunosensor for cortisol detection in a D-shaped optical fiber.

Abstract: Measuring cortisol levels as a stress biomarker is essential in many medical conditions associated with a high risk of metabolic syndromes such as anxiety and cardiovascular diseases, among others. One technology that has a growing interest in recent years is fiber optic biosensors that enable ultrasensitive cortisol detection. Such interest is allied with progress being achieved in basic interrogation, accuracy improvements, and novel applications. The development of improved cortisol monitoring, with a simplified manufacturing process, high reproducibility, and low cost, are challenges that these sensing mechanisms still face, and for which solutions are still needed. In this paper, a comprehensive characterization of a D-shaped fiber optic immunosensor for cortisol detection based on surface plasmon resonance (SPR) enabled by gold coating is reported. Specifically, the sensor instrumentation and fabrication processes are discussed in detail, and a simulation with its complete mathematical formalism is also presented. Moreover, experimental cortisol detection tests were performed for a detection range of 0.01 to 100 ng/mL, attaining a logarithmic sensitivity of 0.65 ± 0.02 nm/log(ng/mL) with a limit of detection (LOD) of 1.46 ng/mL. Additionally, an investigation of signal processing is also discussed, with the main issues addressed in order to highlight the best way to extract the sensing information from the spectra measured with a D-shaped sensor.

Advances in Micro-Fabricated Fiber Bragg Grating for Detection of Physical, Chemical, and Biological Parameters—A Review

Abstract: Fiber optic sensors are widely used in environmental sensing because of their high precision, compact size, remote operation, chemical inertness and multiplexing capabilities. This paper reviews the design, fabrication, and deployment of fiber optic sensors for various applications using grating technology. We conclude with a review of different applications, focusing on environmental factors, hazardous gases, volatile organic compounds biomolecules, marine salinity, and civil structure health monitoring. Our main objective is to provide a complete review of current solutions for humidity, temperature, and other environmental conditions using fiber grating sensors along with a summary of potential future research directions. This paper focuses on fiber grating-based devices and analyze the current state of precedent and existing research around the world as well as the hurdles that lie in the way of their speedy advancement in this field.

A Review of Distributed Fiber–Optic Sensing in the Oil and Gas Industry

Abstract: Fiber–optic sensors have been widely deployed in various applications, and their use has gradually increased since the 1980 s. Distributed fiber–optic sensors, which enable continuous and real–time measurements along the entire length of an optical fiber cable, have undergone significant improvements in underlying industries. In the oil and gas industry, distributed fiber–optic sensors can provide significantly valuable information throughout the life cycle of a well and can monitor pipelines transporting hydrocarbons over great distances. Here, we review the deployment of fiber–optic Rayleigh–based distributed acoustic sensing (DAS), Raman–based distributed temperature sensing (DTS), and Brillouin–based distributed temperature and strain sensing (DTSS) in the oil and gas industry. In particular, we describe the operation principle and basic experimental setups of the DAS, DTS, and DTSS, highlighting their applications in the upstream, midstream, and downstream sectors of the oil and gas industry. We further developed a prototype of a fiber–optic hybrid DAS–DTS system that simultaneously measures vibration and temperature along a multimode fiber (MMF). The reported hybrid sensing system was tested in an operational oil well. This work also discusses the challenges that might hinder the growth of the distributed fiber–optic sensing market in the petroleum industry, and we further point out the future directions of related research.

Femtosecond laser-inscribed fiber-optic sensor for seawater salinity and temperature measurements

Abstract: In this study, a fiber-optic sensor based on Fabry-Perot interferometer (FPI) and Mach-Zehnder interferometer (MZI) cascaded structure is proposed and demonstrated for seawater salinity and temperature simultaneous measurements. A section of hollow-core fiber (HCF) with a U-shaped defect is spliced between single-mode fibers to form FPI. The U-shaped defect inscribed by the femtosecond laser facilitates liquid flow-through and enables the salinity measurement. The MZI composes of laser-induced optical waveguides written in the cladding of the coating-retained single-mode fiber. There is an interaction between the evanescent field of the in-fiber waveguides and the coating due to the written waveguide is close to the cladding-coating interface. Part of the incident light is reflected by HCF to form the FPI spectrum, while the transmitted light in the core is coupled to the written waveguides and guided along the cladding region, which finally returned to the core to obtain the MZI spectrum. Theoretical analysis and experimental verification are carried out, and the results show that the proposed sensor offers a salinity sensitivity of 0.244 nm/‰ and a temperature sensitivity of − 2.767 nm/℃. Such a cascaded interferometer has advantages of high sensitivity and compact size, which is expected to be widely used in seawater parameter measurements due to the flexible structure and precise control.

Fibre optic distributed acoustic sensing of volcanic events

Abstract: Abstract Understanding physical processes prior to and during volcanic eruptions has improved significantly in recent years. However, uncertainties about subsurface structures distorting observed signals and undetected processes within the volcano prevent volcanologists to infer subtle triggering mechanisms of volcanic phenomena. Here, we demonstrate that distributed acoustic sensing (DAS) with optical fibres allows us to identify volcanic events remotely and image hidden near-surface volcanic structural features. We detect and characterize strain signals associated with explosions and locate their origin using a 2D-template matching between picked and theoretical wave arrival times. We find evidence for non-linear grain interactions in a scoria layer of spatially variable thickness. We demonstrate that wavefield separation allows us to incrementally investigate the ground response to various excitation mechanisms. We identify very small volcanic events, which we relate to fluid migration and degassing. Those results provide the basis for improved volcano monitoring and hazard assessment using DAS.

In-situ DNA detection with an interferometric-type optical sensor based on tapered exposed core microstructured optical fiber

Abstract: A label-free DNA biosensor based on exposed core microstructured optical fiber for in-situ real-time DNA detection has been presented and experimentally demonstrated. The sensor is fabricated by splicing a section of tapered exposed core fiber (ECF) between two single-mode fibers (SMFs), forming a multimode Mach-Zehnder interferometer (MZI). The ECF design provides the evanescent field with the sensitivity of a micro/nano optical fiber. In this paper, the ECF has a large cladding diameter (160 µm) but a small core (9 µm), and the core of the ECF is further reduced by tapering, which significantly improves the refractive index (RI) sensitivity. The sensor can detect local RI changes that occur on the surface of the optical fiber due to the binding of biomolecules. We immobilized probe DNA (pDNA) on the exposed side of the core to detect the complementary DNA (cDNA), demonstrating use for specific and label-free sensing of DNA hybridization. Experimental results show that the sensor can qualitatively detect cDNA with the sensitivity of 0.0618 nm/nM and a detection limit of 0.31 nM at a temperature of 25 °C. The proposed DNA biosensor has potential applications in fast developing fields such as medical diagnostics, cancer screening, drug testing, and environmental engineering.

In-situ DNA detection with an interferometric-type optical sensor based on tapered exposed core microstructured optical fiber

Abstract: A label-free DNA biosensor based on exposed core microstructured optical fiber for in-situ real-time DNA detection has been presented and experimentally demonstrated. The sensor is fabricated by splicing a section of tapered exposed core fiber (ECF) between two single-mode fibers (SMFs), forming a multimode Mach-Zehnder interferometer (MZI). The ECF design provides the evanescent field with the sensitivity of a micro/nano optical fiber. In this paper, the ECF has a large cladding diameter (160 µm) but a small core (9 µm), and the core of the ECF is further reduced by tapering, which significantly improves the refractive index (RI) sensitivity. The sensor can detect local RI changes that occur on the surface of the optical fiber due to the binding of biomolecules. We immobilized probe DNA (pDNA) on the exposed side of the core to detect the complementary DNA (cDNA), demonstrating use for specific and label-free sensing of DNA hybridization. Experimental results show that the sensor can qualitatively detect cDNA with the sensitivity of 0.0618 nm/nM and a detection limit of 0.31 nM at a temperature of 25 °C. The proposed DNA biosensor has potential applications in fast developing fields such as medical diagnostics, cancer screening, drug testing, and environmental engineering.

2-D Nanomaterials Assisted LSPR MPM Optical Fiber Sensor Probe for Cardiac Troponin I Detection

Abstract: This study used localized surface plasmon resonance (LSPR) technology to develop an optical fiber biosensor for the detection of cardiac troponin I (cTnI). The etched core mismatch, multimode–photosensitive–multimode (MPM) fiber structure, is used in this study. Following that, graphene oxide (GO), gold nanoparticles (AuNPs), and molybdenum disulfide nanoparticles (MoS2-NPs) are immobilized to the etched MPM surface to improve the sensitivity and stability of the sensor probe. Furthermore, the sensing surface is functionalized with an enzyme to improve the selectivity performance. The absorption spectrum of nanomaterials is determined using a UV-Vis spectrophotometer and a transmission electron microscope (TEM), while the surface of an immobilized probe was observed using a scanning electron microscope (SEM). To determine the sensor’s reliability, a variety of experiments are carried out, including sensing, reusability, reproducibility, stability, pH, and selectivity. Sensitivity of 3.4 pm/(ng/mL), a correlation coefficient of 0.928, limit of detection (LoD) of 96.2638 ng/mL, and linear range of 0–1000 ng/mL are among the sensor’s final performance specifications.

Review of Fiber Optic Displacement Sensors

Abstract: Displacement measurements are of significant importance in a variety of critical scientific and engineering fields such as gravitational wave detection, geophysical research, and manufacturing industries. Due to the inherent advantages such as compactness, high sensitivity, and immunity to electromagnetic interference, in recent years, fiber optic sensors have been widely used in an expansive range of sensing applications, ranging from infra-structural health monitoring to chemical and biological sensing. Of particular interest here, fiber optic displacement sensors have gained wide interest and have evolved from basic intensity modulation-based configurations to more advanced structures, such as fiber Bragg grating-based, interferometric configurations, etc. This paper reviews specifically the advanced fiber optic displacement sensing techniques that have been developed in the past two decades. Details regarding the working principle, sensor design, and performance measures of fiber Bragg gratings-based, interferometers-based (including the Fabry-Perot interferometer, the Michelson interferometer, and the multimode interferometer), microwave photonics-based, and surface plasmon resonance-based fiber optic displacement sensors are given. Challenges and perspectives on future research in the development of practical and high-temperature tolerant displacement sensors are also discussed.

Hybrid Fiber-Optic Sensor for Seawater Temperature and Salinity Simultaneous Measurements

Abstract: In this letter, we propose a compact hybrid fiber-optic sensor for seawater temperature and salinity simultaneous measurements. The device consists of a hollow-core fiber (HCF)-based Fabry-Perot interferometer (FPI) and no-core fiber (NCF)-based anti-resonance (AR) structure. A U-shaped groove is inscribed in the HCF by femtosecond laser for liquid inflow and salinity sensing. A section of the polymer coating is retained on the NCF to excite the AR effect for temperature measurement. The incident light is partially reflected at the HCF fusion end-faces and forms the FPI reflection spectrum, while the transmission light in the NCF cladding is coupled to the polymer coating and forms the AR phenomenon. In theoretical modeling, the temperature and salinity responses of the hybrid sensor are analyzed separately, and the corresponding sensitivities are calculated theoretically. In the experiment, the results show that the temperature and salinity sensitivities are -4.948 nm/ and 0.235 nm/, respectively. In addition, the calibration test, time stability, and repeatability of the sensor are also evaluated by the experiments. The construction method of this hybrid sensing structure is flexible and accurate, so it is expected to be applied in the seawater parameter measurements.

High-performance temperature and pressure dual-parameter sensor based on a polymer-coated tapered optical fiber.

Abstract: Based on the polymer encapsulation method, a compact structure and high-sensitivity temperature and pressure dual parametric sensor was developed in this paper by wrapping an optical microfiber coupler (OMC) in polydimethylsiloxane (PDMS). Benefiting from the stable chemical properties and good optical field control ability of PDMS, the sensor showed good stability and repeatability. The dependence of the sensor sensitivity on wavelength, temperature, and pressure was experimentally investigated. The results showed that the temperature and pressure sensitivity could reach -2.283 nm/°C and 3.301 nm/Mpa in the C-band range. To overcome the cross-sensitivity of sensor temperature and pressure, a sensitivity matrix was established to realize dual-parameter simultaneous demodulation. In addition, the pressure repeatability of the sensor was tested. Based on this, the sensitivity matrix was further calibrated to reduce the error and improve the accuracy of demodulation. Finally, we also designed a protective shell for the sensor to meet the requirements of practical marine applications. Compared with other existing types of optical fiber sensors, this sensor has the advantages of simple fabrication, high sensitivity, and environmental adaptability, and has great potential for application in the field of marine environmental monitoring.

Ultrahigh-performance vector magnetic field sensor with wedge-shaped fiber tip based on surface plasmon resonance and magnetic fluid

Abstract: Abstract A novel fiber-optic vector magnetic field sensor and its sensing quality dependent of fabrication method has been proposed and investigated. The proposed sensor has two surfaces on the tip of a multimode fiber, which is used as the sensing probe. By plating different thickness of gold film on the surfaces, surface plasmon resonance (SPR) can be generated and the signal can be reflected by the surfaces as well. Meanwhile, magnetic fluid (MF) as the magnetic field sensitive material is packed around the sensing probe. The experimental results prove that the response of MF to external magnetic field can be used to sense magnetic field intensity and direction via monitoring the dip wavelength of SPR. The obtained refractive index (RI) sensitivities are 2105 nm/RIU (RI range: 1.332–1.365) and 6692 nm/RIU (RI range: 1.372–1.411), magnetic field intensity sensitivities are 11.67 nm/mT (0°), and −0.47 nm/mT (90°). Besides, the proposed sensing probe is ultracompact and the footprint is extremely small (the length of sensing part is only 615 μm), which is very helpful for magnetic field detection in narrow space and gradient field.

A Surface Plasmon Resonance Optical Fiber Sensor for Simultaneous Measurement of Relative Humidity and Temperature

Abstract: In this work, a new method was explored for developing temperature and relative humidity (RH) optical fiber sensors based on surface plasmon resonance (SPR). A SPR optical fiber sensor coated with carboxymethyl cellulose (CMC) and polydimethylsiloxane (PDMS) was proposed for the simultaneous measurement of RH and temperature. The sensor was fabricated by connecting two no-core optical fibers (NCFs) using multimode optical fibers (MMFs). Metal films were deposited on the surface of NCFs and further coated with CMC and PDMS. CMC coating was used for RH sensing based on the change of refractive index (RI) caused by water absorption; PDMS coating was used for temperature sensing based on its RI change with temperature. Univariate analysis showed that there was very weak interaction between RH and temperature measurement. For RH sensing, the sensitivities were −1.230 nm/RH%, −2.932 nm/RH% and −0.431 nm/RH% when RH were 50%~65%, 65%~70% and 70%~80%, respectively; for temperature sensing, the sensitivity was −2.213 nm/°C at 10 °C~50 °C. The proposed sensor can not only respond to both temperature and RH variation, but also compensate the cross sensitivity between the two parameters. It is simple in structure, easy to manufacture and efficient in the simultaneous detection of temperature and RH, which promises great application prospects in the fields of agriculture, food industry, biological field and other production activities.

Multichannel Fiber Optic SPR Sensors: Realization Methods, Application Status, and Future Prospects

Abstract: Fiber optic sensors based on surface plasmon resonance (SPR) have demonstrated outstanding performance in biomedical, environmental monitoring, public safety, and other aspects, which provide powerful platforms for qualitative detection and quantitative analysis of molecular interactions. Among them, multichannel fiber optic SPR sensor has become a core tool in parallel detection scenarios due to the superiorities of compensating for nonspecific binding and environmental fluctuations and implementing multianalyte determination. The realization methods of multichannel sensing revolve around fiber microstructures, enhancement by materials, and hybrid fiber. The applications of multichannel fiber optic SPR sensors are demonstrated in sensing of liquid refractive index (RI), RI and temperature, biochemical molecules, and physical parameters. This review thoroughly analyzes and compares the structure, excitation effect, sensing performance, and the advantages and disadvantages of each type of multichannel fiber optic SPR sensor. Even though there are still some challenges, such as insufficient sensing channels and difficulty in fabrication, in their advancement, efforts in multidiscipline including developing high‐performance sensitive films and innovating micro–nano fabrication processes will overcome these bottlenecks. Lastly, the future development directions of multichannel fiber optic SPR sensors from principle, structure, and material aspects are discussed.

In-line reflected fiber sensor for simultaneous measurement of temperature and liquid level based on tapered few-mode fiber.

Abstract: An in-line reflective dual-parameters fiber-optic sensor is proposed in this work, whereas it is experimentally verified by measuring both the liquid level and the local temperature distribution simultaneously. The proposed sensor configuration comprises a single-mode fiber (SMF), a tapered few-mode fiber (TFMF), as well as a silver-coated capillary tube. The extracted experimental results indicate that the liquid level only affects the power of the resonant dips, while having little impact on the wavelength. On the other hand, both the wavelength and the power of the resonant dips vary with the temperature change. Therefore, the simultaneous measurement of the liquid level and temperature can be realized according to the different responses of the resonant dips to the liquid level and temperature. The obtained liquid level and temperature sensitivities can reach the values of 0.106 dB/mm and 0.029 dB/°C, 35 pm/°C, respectively. The sensor exhibits the advantages of high stability and low cost, the demodulation relates on only one wavelength which can shorten the scanning wavelength range during measurement. The proposed sensor can be potentially applied where accurate and simultaneous measurements of both temperature and liquid level are required.

Advances in Multicore Fiber Grating Sensors

Abstract: In recent years, multicore fiber (MCF) has attracted increasing interest for sensing applications, due to its unique fiber structure of multiple parallel cores in a single fiber cladding, which offers a flexible configurable platform to establish diverse functional fiber devices for sensing applications. So far, a variety of discrete fiber sensors using MCF have been developed, among which one of the major categories is the MCF grating sensors. The most distinct characteristic of MCF that differs from the normal single mode fibers is that the off-center cores of a MCF are sensitive to bending, which is caused by the bending induced tangential strain in off-center waveguides through either compression or stretching. The bending sensitivity has been widely developed for bending/curvature sensing or measuring physical parameters that are associated with bending. In this paper, we review the research progress on MCF-based fiber grating sensors. MCF-based diverse fiber grating sensors will be introduced, whose working principles will be discussed, and various types of applications of the MCF grating sensors will be summarized. Finally, the challenges and prospects of MCF grating for sensing applications will be presented.

Plastic Optical Fiber Based SPR Sensor for Simultaneous Measurement of Refractive Index and Liquid Level

Abstract: In this work, a plastic optical fiber (POF) based surface plasmon resonance (SPR) sensor is proposed and demonstrated for simultaneous measurement of refractive index (RI) and liquid level. The sensor probe is fabricated by polishing the POF and drilling several micro-holes with equal pitch along the fiber axial, after depositing a layer of gold film on the polished region, the SPR probe is obtained. The effects of the micro-hole on the sensing performance are investigated and the structural parameters of the micro hole are optimized. Experimental results show that the changes of the liquid RI can be detected by monitoring the wavelength position of the SPR peak, and the liquid level can be measured by monitoring the deepness of the SPR peak. An RI sensitivity of 2024.41 nm/RIU was obtained in the RI range of 1.335-1.40, and a resolution of 5 mm and measurement range of 25 mm for liquid level measurement were achieved for the probe. The proposed sensor is compact in size and has a very small cross sensitivity for the RI and liquid level measurement, which is useful in the biomedical and industrial sensing fields.

Review of femtosecond laser machining technologies for optical fiber microstructures fabrication

Abstract: In order to break through the accuracy limits of traditional processing technology and research microscopic phenomena, the sensing structures are fabricated by femtosecond (fs) laser micro-machining technology based on different sensing principles. Fs laser can realize the production of true three-dimensional structure due to its small heat-affected area, high processing accuracy and efficiency, so that it can achieve multi-parameter, high-precision simultaneous measurement on an optical fiber sensor with a smaller size. The application of fs laser increases the flexibility of the sensing structure and improves the key performance indicators of optical fiber sensors. With its excellent performance, the research interest of some scholars is aroused. In this review, the following are studied: firstly, fs lasers are used to fabricate Fabry-Perot interferometer (FPI), Mach-Zehnder interferometer (MZI), fiber Bragg grating (FBG), the combination structures of interferometer and FBG (CI and FBG); secondly, the manufacturing process, repeatability, size, sensitivity, stability, cross-sensitivity, mechanical stability, etc. are compared with the traditional sensor made without fs laser; finally, according to the current development trend of optical fiber sensing devices, the development trend and future expectations of optical fiber sensor with microstructures fabricated by fs lasers are also discussed.

Exploiting Plasmonic Phenomena in Polymer Optical Fibers to Realize a Force Sensor

Abstract: In this work, a novel sensing approach to realize a force optical fiber sensor is designed, developed, and experimentally tested. The proposed sensing methodology exploits the effects of deformation due to an applied force on a patch of plastic optical fiber (POF) connected at the input of a surface plasmon resonance (SPR) sensor realized in a D-shaped POF. Therefore, the proposed force sensor system consists of an SPR D-shaped POF sensor, connected to a spectrometer, within input of a POF patch, connected to a light source used for interacting with the applied force. When the applied force on the patch changes, the mode profile of the light in the multimode POF patch and the SPR-POF sensor change too, so the SPR spectra shift. The obtained experimental results demonstrate that the proposed sensor has a resolution of the force sensor equal to about 22 mN and an excellent linear response in the range from 0 N to 0.5 N.

High sensitivity fiber cladding SPR strain sensor based on V-groove structure.

Abstract: How to couple the light in the fiber core to the cladding is an urgent issue that need to be done for the fabrication of the fiber-cladding SPR sensor, and there is no report about the fiber SPR strain sensor. Hereby, we propose and demonstrate a high sensitivity fiber cladding SPR strain sensor based on V-groove structure. By CO2 laser, the V-groove is fabricated on the single-mode fiber, and the light in the fiber core is effectively coupled to the cladding. The cladding 2cm behind the V-groove is coated with sensing gold film, and a multimode fiber is spliced with the sensing probe to construct the novel fiber cladding SPR sensor. On the basis of the investigation of the effects of different V-groove depth, number and period on the performance of fiber SPR refractive index sensor, a high sensitivity strain SPR sensor is designed and fabricated by employing the characteristic that the V-groove will deform with strain. The testing results indicate that the average refractive index sensitivity of the sensor is 2896.4nm/RIU, and the strain wavelength sensitivity is 25.92pm/µε which is much higher than that of the fiber interference and grating strain sensors, and the strain light intensity sensitivity is -4.4×10-4 a.u./µε. The proposed fiber cladding SPR strain sensor has the advantages of simple structure and convenient manufacture, and can be used for working in a narrow space.