Proposed Fiber Optic Sensor Research Articles

2D-Vector Magnetic Sensing Based on Ring-Shaped Fiber-Optic Structure Coated with Magnetic Fluid.

In this work, a novel fiber-optic sensor for 2D magnetic sensing is explored based on nanostructured magnetic fluid. The fiber-optic sensor comprises a ring-shaped fiber structure that is coated with magnetic fluid. The unique magneto-optical characteristic of the nanostructured magnetic fluid enables the fiber-optic structure to detect magnetic fields. By utilizing the 3D Monte Carlo method, the magneto-optical characteristic induced by the nanostructure changes in the magnetic fluid was analyzed. The sensor can realize 2D vector magnetic sensing by intensity demodulation and achieves a sensitivity of 2.402 dB/mT. The proposed fiber optic sensor helps in developing a high-sensitivity 2D vector magnetic field sensor, which has potential applications in the fields of navigation, electrical power systems, and biological detection.

Coherent Fiber-Optic Sensor for Ultra-Acoustic Crack Emissions.

A coherent optical fiber sensor with adequate sensitivity for detecting the acoustic emission (AE) during the propagation of a crack in a ferrous material is presented. The proposed fiber optic sensor is successfully compared in terms of the SNR (Signal to Noise Ratio) and detectable AE energy levels to commercially available AE piezo-transducers sensors and is proven to be an effective and advantageous alternative for sensing and monitoring fatigue damage in structural applications.

Gold-Diaphragm Based Fabry-Perot Ultrasonic Sensor for Partial Discharge Detection and Localization

Acoustic measurement is the most widely used non-electric method to detect partial discharge (PD) signals by detect the ultrasonic waves arisen from partial discharge. To solve the shortages of low sensitivity and susceptibility to interferences, a gold diaphragm based Fabry-Perot interferometer ultrasonic sensor is proposed and experimentally demonstrated. Its high acoustic sensitivity and directional insensitivity shows great capability for PD detection and localization. Experimental results illustrate a well acoustic response from 20 kHz to 150 kHz when standard ultrasonic signals applied. The frequency range covers the acoustic frequencies derived from PD process. The ultrasonic signals from a discharge source is measured by the proposed fiber optic sensor with difference distances and incident angles. The output shows an attenuation of 1.32 dB/m and the sensor can detect weak signals as far as 3 m. The directional deviation coefficients are less than 10% for each measuring distance which exhibits directional independence. Two localization techniques with a sensor array (four sensors) are proposed and simulations are carried out to verify them feasible. The fiber-optic ultrasonic sensor may have a great potential in stability maintenance of electrical power systems due to its low cost, compact structure, environmentally robustness and simple manufacturing.

Chirped anti-resonant reflecting optical waveguide for the distributed sensing of pressure.

A chirped anti-resonant reflecting optical waveguide (ARROW) for the simultaneous measurement of pressure intensity and spatial localization has been proposed and experimentally demonstrated. An etched chirped ARROW was fabricated, which shows a chirped spectral characteristic. Additionally, an in-line Mach-Zehnder interferometer is also formed with the core mode and higher-order modes. The pressure intensity and the spatial localization can be detected by interrogating the wavelength shift of the in-line Mach-Zehnder interferometer and the chirped ARROW, respectively. The experimental results show that the pressure sensitivity of $ - {4.42}\;{\rm nm/MPa}$-4.42nm/MPa and the spatial sensitivity of 0.86 nm/cm can be achieved. The proposed fiber optic sensor can be used for multipoint pressure detection in the fields of security, structure monitoring, and oil exploration, etc.

Modeling of a fiber optic SPR biosensor employing Tin Selenide (SnSe) allotropes

We report an unique design of a fiber optic SPR biosensor in this study utilizing two-dimensional (2D) Tin Selenide (SnSe) allotropes not revealed before. Due to enhanced optical characteristics with 2D graphene-like structure of monolayer SnSe, recently it is getting much attraction by the researchers to use as a biomolecular recognition element (BRE) in sensor design. Sensitivity of the proposed fiber optic sensor with three sorts of monolayer allotropes of SnSe (α-SnSe, δ-SnSe and ε-SnSe) as a BRE is analyzed through wavelength interrogation scheme for sensing application. Results show that sensors with α-SnSe, δ-SnSe, and ε-SnSe exhibit sensitivities of 3225 nm/RIU, 3300 nm/RIU and 3475 nm/RIU respectively. It is obvious that proposed sensor with improved sensitivity outperforms the conventional Ag-only based sensors having poor sensitivity of 1800 nm/RIU. Thus the proposed SnSe allotropes can be reasonable alternate of conventional BRE to design extremely high sensitive fiber optic SPR biosensors for DNA hybridization.

Fiber Optic Sensor Based on Vernier Microwave Frequency Comb

We demonstrate a proposed fiber optic sensor based on detecting the envelope of a Vernier microwave frequency comb (VMFC). A mode-locked fiber laser was employed as a microwave frequency comb source. A fiber ring, functioning as a sensor head as well as a microwave photonic filter, tailored the amplitude of each harmonic of the microwave frequency comb. By carefully designing the fiber ring length and the frequency separation of the microwave frequency comb, the Vernier effect is generated on the photodiode recovered microwave frequency comb after the laser pulses pass through the fiber ring. The sensing information can be deduced by tracking the envelope of the VMFC. The experimental results of a temperature sensing test show that the frequency shifts of the envelope peak have a good linear relationship with temperature variation. Furthermore, the sensitivity of the proposed sensor system is controllable.

Al2O3-MgO nanocomposite based fiber optic temperature sensor

Fabrication and characterization of fiber optic temperature sensors using Al2O3-MgO nanocomposite as cladding material have been reported. Co-precipitation route was adopted to synthesize Al2O3, MgO and their composites of different composition. The synthesized Al2O3-MgO nanocomposites (25%–75%, 50%–50% and 75%–25%) of different mole concentrations have been characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy and UV-Visible spectroscopy to investigate the structural, morphological, elemental and optical properties. The temperature sensing probe was fabricated by coating Al2O3-MgO nanocomposites over the unclad portion of an optical fiber. The response of the sensors has been studied in the temperature range of 35 °C–80 °C. Further, the experimental result depicts an exorbitant temperature sensitivity of ∼10.8 towards Al2O3-MgO nanocomposites (50%–50%) than other composites, pristine Al2O3 and MgO. In addition the sensor exhibits an ultrahigh sensitivity of 0.62%/°C with a better linear regression coefficient of 95%. Therefore, the proposed fiber optic sensor is capable of measuring dynamic temperatures in relentless environment.

Enhancement in performance of an evanescent wave fiber optic sensor in the near-infrared region by graphene’s chemical potential

An intensity interrogation-based fiber optic evanescent wave sensor with graphene monolayer is simulated and analyzed in the near-infrared spectral region. Chalcogenide glasses are considered as fiber’s core and clad materials. Dispersion relations of normal and malignant human liver tissues are considered for analysis. The effect of graphene’s chemical potential (μ) on sensor’s performance is examined, which is evaluated in terms of sensitivity and resolution. The analysis of simulation results indicates that if μ is set around 0.45 eV at 1550-nm light wavelength (λ), the sensitivity achieved is nearly 47 mW/RIU (real index) and 280 mW/RIU (imaginary index), and the resolution achieved is of the order of 10−9 RIU (real index) and 10-10 RIU (imaginary index). Even further improvement in the sensing performance can be achieved around μ = 0.6 eV. The analysis shows that it is preferable to use p-polarized light as it provides significantly better values of sensitivity and resolution than s-polarized light. In addition to smaller photodamage and reduced Rayleigh scattering (due to being operated in NIR), the proposed fiber optic sensor probe has the capability to provide considerably superior resolution than existing fiber optic sensors based on different techniques.

Chalcogenide fiber-optic SPR chemical sensor with MoS2 monolayer, polymer clad, and polythiophene layer in NIR using selective ray launching

Abstract Surface plasmon resonance (SPR) based chalcogenide fiber-optic sensor with polymer clad and MoS2 monolayer is simulated and analyzed in near infrared (NIR) for detection of mixture of alcohols (ethanol and methanol) dissolved in water solution. The proposed fiber optic sensor is analyzed under angular interrogation method, which is based on selective ray (on-axis) launching of monochromatic light into the fiber core at varying angle followed by measuring the loss of power (in dB) after passing through the SPR probe region. The performance of the sensor is analyzed in terms of its figure of merit (FOM). The sensor’s specificity towards alcohols along with considerably larger FOM is achieved by utilizing a polythiophene (PT) layer. The results indicate that longer NIR wavelength (λ) provides superior sensing performance. The sensor’s performance is better for larger volume fraction of methanol in the water solution. The proposed fiber optic SPR sensor has the capability of providing much greater FOM compared with the previously-reported SPR sensors.

Fluoride Fiber-Optic SPR Sensor With Graphene and NaF Layers: Analysis of Accuracy, Sensitivity, and Specificity in Near Infrared

Surface plasmon resonance (SPR) based fluoride fiber-optic sensor with graphene and sodium fluoride layers is simulated and analyzed in near infrared (NIR) for detection of alcohols. Through this paper, the fluoride fiber has been employed for the first time in SPR sensing application. The proposed fiber optic sensor is analyzed under angular interrogation method, which is based on on-axis launching of monochromatic light into the fiber core at varying angle followed by measuring the power transmitted through the SPR probe region. The sensor's specificity towards alcohols plus a significantly increased sensitivity and accuracy are ensured by a polythiophene layer. The results indicate that longer NIR wavelength (λ) provides superior sensing performance. Further, the proposed sensor's performance can be significantly enhanced by tuning the chemical potential (μ) of graphene monolayer. In summary, monochromatic light of λ = 1550 nm and 0.65 eV <; μ <; 0.70 eV provides substantially high performance in terms of sensitivity, accuracy, and figure of merit. The proposed sensor has the capability to provide significantly better performance than previously-reported SPR sensors.

Development of LSPR-Based Optical Fiber Dopamine Sensor Using L-Tyrosine-Capped Silver Nanoparticles and Its Nonlinear Optical Properties

Facile synthesis of L-tyrosine-capped silver nanoparticles (Tyr-AgNPs) was carried out, and its linear and nonlinear optical properties were investigated. Further, the sensing properties of Tyr-AgNPs toward dopamine were explored. Tyr-AgNPs exhibit a decrease in fluorescence intensity while a linear increase in absorption spectrum against increase in dopamine (DA) concentration (0–50 μM) at room temperature. Tyr-AgNPs are used as the sensing material for the fabrication of fiber optic dopamine sensor. Sensitivity, selectivity, and limit of detection of the sensor are evaluated. This proposed fiber optic sensor may offer sensitive and low-cost strategy for DA detection.

Wide Range Fiber Displacement Sensor Based on Bending Loss

A wide range fiber optic sensor system for displacement and crack monitoring is developed. In the proposed fiber optic sensor system, a number of fiber loops are formed from a single fiber and each fiber loop is used as a crack or displacement sensor. The feasibility and the dynamic range of the fiber sensor developed in this manner are investigated experimentally. Both glass fibers and plastic fibers are used in the experiments. Experimental results show that the new fiber optic sensor has a wide range (maximum range is 88 mm) and this sensor also has a high sensitivity for displacement and crack monitoring when an appropriate diameter of the fiber loop is selected as the sensor. Moreover, the proposed method is very simple and has low cost, so in situ application potential of the proposed sensor is high.

가변 페브리-페로 필터와 FBG를 이용한 광세기 기반 자기기준 광섬유 센서

본 논문에서는 자기기준 특성을 가지는 광세기 기반 광섬유 센서 구조를 제안하고 실험적으로 구현하여 성능을 제시한다. 제안하는 광섬유 센서는 광대역 광원(BLS), fiber Bragg grating (FBG), 가변 페브리-페로(Fabry-Perot) 필터, LabVIEW 프로그램으로 구성된다. 제안한 자기기준 광섬유 센서의 이론적인 해석을 통하여 측정 변수(Χ)와 보정 변수(β)를 정의하고, 이를 바탕으로 전달함수(Η)를 구한다. 또한 실험을 통하여 이론적인 해석의 타당성을 제시한다. 제안한 광섬유 센서 구조는 광대역 광원의 출력 광세기가 0 dB, 3 dB, 6 dB 감소해도 측정결과에 영향을 미치지 않는 자기기준 특성을 가진다. 또한 다른 특성의 FBG를 사용하여도 측정 가능하므로, 제안한 광섬유 센서 구조는 임의의 규격을 가진 FBG를 사용할 수 있다. 광원의 광세기가 감소하였을 때와 세 가지 다른 특성의 FBG 쌍을 이용하여 측정한 결과 이론적인 값과 잘 일치함을 보였다. 따라서 제안한 광섬유 센서는 자기기준 특성과 구성하는 FBG의 규격이 비교적 엄격하지 않아도 되는 장점을 가진다.

Transmissive grating-reflective mirror-based fiber optic accelerometer for stable signal acquisition in industrial applications

This paper discusses an applicable fiber-optic accelerometer composed of a transmissive grating panel, a reflection mirror, and two optical fibers with a separation of quarter grating pitch as transceivers that monitor the low-frequency accelerations of civil engineering structures. This sensor structure brings together the advantages of both a simple sensor structure, which leads to simplified cable design by 50% in comparison with the conventional transmission-type fiber optic accelerometer, and a stable reflected signals acquisition with repeatability in comparison to the researched grating-reflection type fiber optic accelerometer. The vibrating displacement and sinusoidal acceleration measured from the proposed fiber optic sensor demonstrated good agreement with those of a commercial laser displacement sensor and a MEMS accelerometer without electromagnetic interference. The developed fiber optic accelerometer can be used in frequency ranges below 4.0 Hz with a margin of error that is less than 5% and a high sensitivity of 5.06 rad/(m/s)2.

Performance of a single reflective grating-based fiber optic accelerometer

This paper presents a single reflective grating-based fiber optic accelerometer that can monitor the low-frequency acceleration of civil engineering structures. A simpler sensor structure was realized by employing a single reflective grating panel and two optical fibers as transceivers rather than the moiré fringe fiber optic accelerometer, which is composed of two gratings and four optical fibers. The simplified layout contributes to resolving the issues of space restraints during installation and complex cabling problems in transmission of fiber optic accelerometers. The measured oscillated displacement and sinusoidal acceleration from the proposed fiber optic sensor demonstrated good agreement with those of a commercial laser displacement sensor and an accelerometer without electromagnetic interference. The developed fiber optic accelerometer can be used in frequency ranges below 4 Hz within a 5% error margin and high sensitivity of 33.33 rad G−1. Furthermore, in comparison with the conventional transmission fiber optic accelerometer design, the proposed scheme's cable design is simplified by 50%.