Etched Fiber Bragg Grating Sensor Research Articles

L-cysteine modified gold nanoparticles for copper (II) ion detection using etched Fiber Bragg Grating sensor

L-cysteine modified gold nanoparticles for copper (II) ion detection using etched Fiber Bragg Grating sensor

A Silver Nanoparticle Modified Etched Fiber Bragg Grating Sensor for Arsenic Detection

A Silver Nanoparticle Modified Etched Fiber Bragg Grating Sensor for Arsenic Detection

Selective detection of lead in water using etched fiber Bragg grating sensor

In this work, we demonstrate a maleic acid (MA) functionalized gold nanoparticle (AuNP) coated, clad etched-fiber Bragg grating (e-FBG) sensor, capable of detecting lead metal ion (Pb2+) in water. The self-assembled carboxylic group in MA-AuNP shows an assertive coordination behavior towards Pb2+ for selective detection through a Bragg wavelength shift. The limit of detection (LOD) is found to be 10 femtomolar (fM, 0.0000002 ppb) with a dynamic range up to 100 nanomolar (nM, 20.72 ppb), which is within the acceptable limit stipulated by the World Health Organization (WHO) for safe drinking water (10 ppb). The sensor's recovery concentration is > 90% for spiked real water samples. A good reproducibility (standard error < 10 pm) and specificity along with portability, small footprint and real time response make e-FBG sensor an ideal optical probe for drinking water.

Enhanced Optical Sensitivity of Polyvinyl Alcohol–Reduced Graphene Oxide Electrospun Nanofiber Coated Etched Fiber Bragg Grating Sensor for Detection of Myoglobin a Cardiac Biomarker

Etched fiber Bragg grating (eFBG) sensors have shown to be highly sensitive with the capability of giving accurate real‐time response to a variety of measurands such as pressure, gas, biomolecules, to name a few. These sensors have not shown their mettle as competitive products mainly due to nonreproducibility in results and inefficiency in upscaling for large‐scale production; the main reason being nonuniform and complicated coating procedures. Herein, the enhancement in refractive index (RI) sensitivity (≈4 times) obtained with electrospinning of polyvinyl alcohol–reduced graphene oxide (PVA–rGO) nanofibers onto eFBG sensor using a customized target and a unique sandwich arrangement is demonstrated. The enhancement in RI sensitivity has led to a lower detection limit and increased sensitivity and linear range for a case study using myoglobin (Mb), an early‐stage cardiac biomarker with high reproducible results (standard error ≤±2.3%). rGO embedded PVA nanofiber electrospun onto an eFBG sensor (PVA–rGO sensor) is the first of its kind and has significant importance in developing cost‐effective, label‐free, multianalyte, portable, real‐time, point‐of‐care (POC) kits at ambient conditions.

Highly sensitive and Rapid detection of mercury in water using functionalized etched fiber Bragg grating sensors

• CNC bolaamphiphile functionalized eFBG sensor for selective and rapid detection of mercury (Hg). • Thiol-Hg 2+ coordination interaction between CNC and Hg 2+ determined by both UV absorbance and Bragg wavelength shifts. • Low LOD (< WHO standard), linear dynamic range and good repeatability using low sample volumes and minimal instruments. • Promising results with real water sample prove. • eFBG sensor to be used as on-site, real time Hg 2+ probe. An effective optical method has been proposed using cysteine conjugated naphthalene diimide (CNC) bolaamphiphile functionalised etched Fiber Bragg grating (eFBG) sensor for selective and rapid detection of mercury (Hg 2+ ) in drinking water. The sensor responds with a Bragg wavelength shift (Δλ B ) to the thiol-Hg 2+ coordination interaction between CNC and Hg 2+ . The thiol-Hg 2+ interaction was initially studied by UV absorbance studies (bulk solutions) of CNC with increased concentrations of Hg 2+ (600 nM to 3 μM). The study displayed a linear relationship with the limit of detection (LOD) of 100 nM, which is below the world health organisation (WHO) standards for drinking water (22 nM). To enhance the LOD, the CNC was coated onto the eFBG sensor using two coating protocols (dip and spin coating) followed by Hg 2+ detection. The dip (spin) coated sensor displayed a dynamic-range from 1 pM to 1 μM (1 pM to 10 nM) and LOD of 1 pM. The sensor's repeatability (maximum error of 13.2 picometers) and specificity in the presence of other interfering metals like Pb 2+ , Cu 2+ , Na 2+ and Cd 2+ has been determined. The sensor can be developed into a highly sensitive, selective, portable, real-time, on-site Hg 2+ optical probe for drinking water.

Etched Fiber Bragg Grating Sensor for Quantification of DNA

The detection and quantification of DNA is of critical importance in various molecular biology processes and has applications in fields ranging from forensics to environmental monitoring. Here, the development of a highly sensitive and label-free technique for DNA detection is reported. This article proposes a reduced graphene oxide (rGO) coated etched Fiber Bragg Grating (eFBG) sensor as a tool for the detection and quantification of dsDNA. The proposed sensor is found to have a limit of detection of 261.87 pg/$\mu \text{l}$ and the sensor response is a linear function of the dsDNA concentration in the range between 1 ng/$\mu \text{l}$ to 50 ng/$\mu \text{l}$ with excellent stability and repeatability. The paper also proposes a technique to quantitatively measure the amount of DNA bound to the sensor and thus, the DNA binding efficacy of the rGO coating on the sensor, utilizing UV spectrometry.

Sensitivity enhancement of FBG sensor for portlandite monitoring

In this paper, a cladding etched fiber Bragg grating (FBG) sensor is proposed to monitor chemicals (Ca(OH)2 and Mg(OH)2) which produces in civil structures. Further, to enhance the sensitivity, an indium tin oxide is coated on cladding etched FBG sensor. It is observed that the indium tin oxide coated sensor is highly sensitive in terms of chemical detection and inducing wavelength shift of 12 nm and 10 nm with Ca(OH)2 and Mg(OH)2 respectively. On the other hand, cladding etched FBG sensor produces a wavelength shift of 8 nm and 6 nm for Ca(OH)2 and Mg(OH)2 respectively.

Analysis of experimental results on the adulteration measurement by an etched fiber Bragg grating sensor

This paper presents an analysis of the experimental results on the adulteration measurement of methanol content in ethyl alcohol by a HF etched fiber Bragg grating (EFBG). A minimum methanol concentration, down to 1% in ethyl alcohol, was measured. The sensitivity of the developed EFBG sensor was about 30nm/refractive index unit (RIU). The minimum change in refractive index of 2×10−4 was estimated. The experimental results are analyzed based on double clad approximation theory for cylindrical/rectangular waveguide geometry. A graphical method is used to find out the dependence of effective refractive index of the double clad fiber on cladding diameter and on surrounding refractive index. The change in Bragg wavelength, with surrounding medium refractive index, is estimated. It is observed that, for a particular clad diameter, the effective refractive index increased with increase in surrounding medium refractive index. The refractive index sensitivity was also higher for lower clad diameter grating. The theoretical analysis explained the experimental results very well.

Highly Sensitive Carbon Nanotubes Coated Etched Fiber Bragg Grating Sensor for Humidity Sensing

The sensing of relative humidity (RH) at room temperature has potential applications in several areas ranging from biomedical to horticulture, paper, and textile industries. In this paper, a highly sensitive humidity sensor based on carbon nanotubes (CNTs) coated on the surface of an etched fiber Bragg grating (EFBG) sensor has been demonstrated, for detecting RH over a wide range of 20%-90% at room temperature. When water molecules interact with the CNT coated EFBG, the effective refractive index of the fiber core changes, resulting in a shift in the Bragg wavelength. It has been possible to achieve a high sensitivity of ~31 RH, which is the highest compared with many of the existing FBG-based humidity sensors. The limit of detection in the CNT coated EFBG has been found to be ~0.03 RH . The experimental data shows a linear response of Bragg wavelength shift with increase in humidity. This novel method of incorporating CNTs on to the FBG sensor for humidity sensing has not been reported before.

Calibration of Etched Fiber Bragg Grating Sensor Arrays for Measurement of Molecular Surface Adsorption

Etched Fiber Bragg Grating (EFBG) sensors are attractive from the point of the inherently high multiplexing ability of fiber based sensors. However, the strong dependence of the sensitivity of EFBG sensors on the fiber diameter requires robust methods for calibration when used for distributed sensing in a large array format. Using experimental data and numerical modelling, we show that knowledge of the wavelength shift during the etch process is necessary for high-fidelity calibration of EFBG arrays. However as this approach requires the monitoring of every element of the sensor array during etching, we also proposed and demonstrated a calibration scheme using data from bulk refractometry measurements conducted post-fabrication without needing any information about the etching process. Although this approach is not as precise as the first one, it may be more practical as there is no requirement to monitor each element of the sensor array. We were able to calibrate the response of the sensors to within 3% with the approach using information acquired during etching and to within 5% using the post-fabrication bulk refractometry approach in spite of the sensitivities of the array element differing by more than a factor of 4. These two approaches present a tradeoff between accuracy and practicality.

Etched fiber Bragg grating for refractive index distribution measurement

We present a refractive index (RI) distribution sensor based on an etched fiber Bragg grating (FBG). The FBG is etched by hydrofluoric acid solution until the residual diameter of its core is about 5.73μm, and then it is installed in a micro-tube where the RI of the liquid medium decreases linearly along its axis. The reflection spectrum of the etched FBG changes from a single resonant peak into many micro-resonant peaks under the inhomogeneous liquid medium. The difference of the wavelengths between the maximum micro-resonant peak and the minimum one changes linearly with the RI gradient, and the average change of the wavelengths of them changes linearly with the average change of the RI as well. Experimental results show that the sensitivity of RI gradient and the average sensitivity of RI for this etched FBG sensor is about 336.2nmmm/RIU and 49.44nm/RIU, respectively, when the surrounding RI ranges from 1.330 to 1.3586. Associated with the sensitivity of the RI gradient and the average sensitivity of the RI, the linear RI distribution of inhomogeneous liquid medium surrounding the etched FBG can be obtained.