Query: Fiber optic sensor detection

title: High sensitivity detection of partial discharge acoustic emission within power transformer by sagnac fiber optic sensor
abstract: Partial discharge acoustic detection is an important monitoring tool for power transformer diagnosis, which was traditionally performed by mounting the piezoelectric transducers on the oil tank surface. The disadvantage of partial discharge acoustic detection is its low sensitivity when partial discharge occurs inside the winding, which greatly compromises the value of partial discharge acoustic detection. Fiber optic sensors that can be deployed within power transformer are expected to be a potential solution. In this research, we used a Sagnac fiber sensor system built in lab to investigate the benefits of using fiber optic sensor for partial discharge acoustic detection. Acoustic pulses were induced in oil outside the winding and in oil duct inside the winding of a single phase 50 kV transformer. Although both fiber optic sensor and piezoelectric sensor can effectively detect the acoustic pulses outside the winding, fiber optic sensor gained a much better sensitivity over piezoelectric transducer to detect the acoustic pulses originated inside the winding. We envisage that the proposed fiber sensor can be deployed in power transformers to significantly enhance the detection performance of acoustic emission induced by partial discharge.

title: Highly sensitive detection of dopamine using a graphene functionalized plasmonic fiber optic sensor with aptamer conformational amplification
abstract: Surface plasmon resonance (SPR) optical fiber sensors can be used as cost effective and relatively simple to implement alternatives to well established bulky prism configurations for high sensitivity in situ biomedical measurements. The miniaturized size and remote operation ability offer a multitude of opportunities for single point sensing in hard to reach spaces, even possibly in vivo. The biosensor configuration presented here utilizes a nano scale metal coated tilted fiber Bragg grating (TFBG) imprinted in a commercial single mode fiber core with no structural modifications. A unique feature of our TFBG sensor is the use of a single layer graphene coating over the gold coated fiber surface, functionalized with a selective DNA aptamer for highly sensitive detection of target molecules. We have demonstrated the capture of dopamine molecules by the DNA aptamer, resulting in aptamer well defined conformational changes in response to dopamine surface affinities. This process amplifies the surface refractive index modulation over the fiber surface to enable precise dopamine concentration measurement in real time via monitoring of the surface plasmon resonance signals. The sensor shows a linear response for dopamine concentration in the range from 10 13 M to 10 8 M with a lower limit of detection of 10 13 M. This limiting concentration is lower than the concentration fluctuations of dopamine in the human brain. The sensor works with minimal cross sensitivities because of the core mode calibration inherent in the TFBG. Integration of the TFBG with a hypodermic needle should allow similar measurements in vivo, presenting an appealing solution for rapid, low power consumption and highly sensitive detection of analytes at low concentrations in medicine as well as in chemical and environmental monitoring.

title: Distributed fiber optic sensor enhanced detection and prediction of shrinkage induced delamination of ultra high performance concrete overlay
abstract: This study develops a delamination detection system for smart ultra high performance concrete (UHPC) overlays using a fully distributed fiber optic sensor. Three 450 mm (length) x 200 mm (width) x 25 mm (thickness) UHPC overlays were cast over an existing 200 mm thick concrete substrate. The initiation and propagation of delamination due to early age shrinkage of the UHPC overlay were detected as sudden increases and their extension in spatial distribution of shrinkage induced strains measured from the sensor based on pulse pre pump Brillouin optical time domain analysis. The distributed sensor is demonstrated effective in detecting delamination openings from microns to hundreds of microns. A three dimensional finite element model with experimental material properties is proposed to understand the complete delamination process measured from the distributed sensor. The model is validated using the distributed sensor data. The finite element model with cohesive elements for the overlay substrate interface can predict the complete delamination process.

title: Surface plasmon resonance based fiber optic sensor for the detection of cysteine using diosmin capped silver nanoparticles
abstract: A simple green method to synthesize silver nanoparticles (AgNPs) is described where diosmin acts as reducing and capping agent. Formation of diosmin capped silver nanoparticles (Dios AgNPs) was characterized using UV vis spectroscopy, X ray diffraction, TEM, Raman imaging and FTIR analysis. Investigations on the biosensing of Dios AgNPs among various amino acids showed excellent response towards cysteine. Further an SPR based fiber optic sensor for cysteine was fabricated and its sensitivity, selectivity and limit of detection were investigated and reported. The fiber optic sensor was developed by coating a thin film of silver over the unclad core of the fiber and then coated with Dios AgNPs. The sensor has advantages of low cost of production, fast response, high selectivity and sensitivity. The sensor can be used for online monitoring and remote sensing applications.

title: Label free detection of DNA hybridization with a compact LSPR based fiber optic sensor.
abstract: A miniaturized, robust, localized surface plasmon resonance (LSPR) coupled fiber optic (FO) nanoprobe providing an integrated and portable solution for detection of DNA hybridization and measurement of DNA concentrations has been demonstrated. The FO nanoprobe was created by constructing arrays of metallic nanostructures on the end facets of optical fibers utilizing nanofabrication technologies, including electron beam lithography and lift off processes. The LSPR FO nanoprobe device offers real time, label free, and low sample volume quantification of single strand DNA in water with high sensitivity and selectivity, achieving a limit of detection around 10 fM. These results demonstrate the feasibility of the LSPR FO nanoprobe device as a compact and low cost biosensor for detection of short strand DNA.

title: Localized surface plasmon resonance based fiber optic sensor for the detection of triacylglycerides using silver nanoparticles
abstract: A label free technique for the detection of triacylglycerides by a localized surface plasmon resonance (LSPR) based biosensor is demonstrated. An LSPR based fiber optic sensor probe is fabricated by immobilizing lipase enzyme on silver nanoparticles (Ag NPs) coated on an unclad segment of a plastic clad optical fiber. The size and shape of nanoparticles were characterized by high resolution transmission electron microscopy and UV visible spectroscopy. The peak absorbance wavelength changes with concentration of triacylglycerides surrounding the sensor probe, and sensitivity is estimated from shift in the peak absorbance wavelength as a function of concentration. The fabricated sensor was characterized for the concentration of triacylglyceride solution in the range 0 to 7 mM. The sensor shows the best sensitivity at a temperature of 37degC and pH 7.4 of the triacylglycerides emulsion with a response time of 40 s. A sensitivity of 28.5 nm/mM of triacylglyceride solution is obtained with a limit of detection of 0.016 mM in the entire range of triacylglycerides. This compact biosensor shows good selectivity, stability, and reproducibility in the entire physiological range of triacylglycerides and is well suited to real time online monitoring and remote sensing.

title: Surface Plasmon Resonance based fiber optic sensor for mercury detection using gold nanoparticles PVA hybrid
abstract: Fabrication of Surface Plasmon Resonance (SPR) based fiber optic sensor for mercury detection utilizing gold nanoparticles (AuNPs) PVA hybrid as sensing material is reported. Films of citrate capped AuNPs in PVA matrix are prepared and their optical properties are studied. UV vis spectroscopy, Fourier transform infrared spectroscopy (FTIR) transmission electron microscopy (TEM) and Particle size analysis (DLS) are performed to ascertain the formation of Au NPs. Aqueous Hg 2+ sensing of citrate capped gold nanoparticles in PVA matrix are investigated. Further SPR based fiber optic sensor has been fabricated using citrate capped AuNPs PVA hybrid as sensing material. The detection limit of the proposed sensor is found to be 1 x10 6 M.

title: Fiber optic sensor for heart rate detection
abstract: The principle of operation, design aspects, experimentation and performance of an extrinsic fiber optic sensor using fiber optic displacement sensor for the measurement of amplitude and frequency of heart rate signal is presented and investigated. The displacement sensor consists of fiber optic transmitter, fiber optic bundled probe and photodiode detector and an artificial electrocardiogram (ECG) signal is used in the testing. The sensitivity of the sensor is found to be 0.002 mV/mm and thus it is capable of measuring heart rate from 50 bpm to 300 bpm with linearity more than 99% The simplicity of the design, high degree of sensitivity, dynamic range and the low cost of the fabrication make it suitable for real field applications. Moreover, accuracy and reliability are the excellent pay offs of this fiber optic sensor.

title: A novel method of identifying damage types in carbon fiber reinforced plastic cross ply laminates based on acoustic emission detection using a fiber optic sensor
abstract: We applied a highly sensitive phase shifted fiber optic Bragg grating (PS FBG) sensor with a broad bandwidth to acoustic emission (AE) detection in a composite material. Based on AE detection, this research proposed a novel method to identify damage types in carbon fiber reinforced plastic (CFRP) laminates. Because the PS FBG sensor measured pure dynamic strain, the detected AE signals had great physical reliability, which made elastic wave theory suitable for analysis of the signal. The analysis clarified the different characteristics of Lamb wave modes in three types of AEs caused by a transverse crack, delamination and fiber breakage. Additionally, the ratios of the amplitudes of the S0 mode to the A0 mode and the peak frequencies quantitatively evaluated the mode characteristics in the AE signals. Simultaneously using the two physical parameters, we identified the three types of damage among the AE signals detected in a three point bending test. Furthermore, the finite element method based AE wave propagation simulation agreed well with the identification results. Hence, the proposed identification method with the PS FBG sensor has great physical reliability for evaluating damage in composite laminates.

title: SPR based fiber optic sensor for refractive index sensing with enhanced detection accuracy and figure of merit in visible region
abstract: We, theoretically, propose a surface plasmon resonance (SPR) based indium tin oxide (ITO) silver (Ag) coated fiber optic sensing probe for refractive index sensing in visible regime of the electromagnetic spectrum. A comparative study of ITO+Ag coated probe with Ag coated probe and with ITO coated probe using their respective optimized film thicknesses is carried out. We show that the proposed probe is endowed with the better sensitivity characteristic of ITO and better detection accuracy (DA) characteristic of Ag, and can sense change in refractive index with enhanced DA and figure of merit (FOM) in the visible region.