Fiber optic sensors show many advantages as compared to other alternatives for a wide range of energy applications spanning electrical grid, pipelines, and civil infrastructure monitoring amongst others. Multimode interference-based fiber optic sensor configuration is one device architecture that is being explored for a range of different analytes, and which is fabricated by sandwiching a section of multimode fiber between two single mode fibers. Fiber optic devices based on multimode interference (MMI) are easy to fabricate and offer attractive prospects for applications in the areas of optical communication and fiber lasers as well as sensing. When light is coupled from a single mode fiber to a multimode fiber (MMF), multiple modes supported by the MMF are excited and interfere with each other, giving rise to an interference pattern along the MMF length. At specific positions along the axis of the MMF, light is concentrated and forms replicas of the input field which are known as self-images, with the self-imaging condition providing a narrow-band interference feature as a function of wavelength that is also affected by a wide range of analytes for sensing purposes. The self-images formed are simulated here using commercial software COMSOL Multiphysics. Sensitivity to a range of different analytes including refractive index, strain and hydrogen gas is explored. Optical fiber sensors based upon multimode interferometer sensors are investigated as attractive sensing options for infrastructure monitoring applications.
Structural Health Monitoring (SHM) of pipelines using nondestructive testing/evaluation (NDT/E) techniques is important particularly for the energy industries and for the oil/gas distribution which helps reduction in maintenance costs as well as increased service lifespan. Among various NDE techniques, ultrasonic guidedwaves (GWs) technique is popular for inspection and monitoring of pipes due to its advantages e.g., long-distance monitoring using a fixed sensor probe, full volumetric coverage, and inspection for invisible or inaccessible structure. Recently, performance and scope of the GWs method is explored using optical fiber sensing technology such as fiber Bragg gratings are demonstrated for many ultrasonic sensing applications. The optical fiber sensors bring the advantage of remote sensing, large acoustic bandwidth, and multiplexing capability of the sensors to extend the range of GWs based NDE method. This work describes the health monitoring of damaged pipeline structure in a nondestructive manner using alternative No-core fiber (NCF) based quasi-distributed fiber-optic acoustic sensor combined with ultrasonic GWs excitation. We set up two similar 6-inch carbon-steel pipes (16-ft long), one consists of various defects and the other is healthy without any defect for reference. The pipes are actively excited by employing different ultrasonic sources; (1) magnetostrictive collar (MR) to generate the axisymmetric (torsion) GWs and (2) conventional piezoelectric patches to generate the antisymmetric flexural waves on the exterior surface, and the characteristics of acoustic-ultrasonic signals are studied using NCF based multiplexed fiber-optic sensor. Fiber optic sensor is an inline multimode interferometer made by sandwiching a piece of NCF (~5cm) between the single mode fibers. The NCF sensor is remotely bonded at 45° w.r.t pipe axis on one end and has an ultrasonic sensing range of >600kHz. Finally, the measured acousto-ultrasonic signals for different ultrasonic sources are compared to those obtained by the numerical simulation or electrical-based sensor for the healthy and damaged test pipes. The proposed work presents useful insight for damage detection in pipes using an NCF-based quasi-distributed fiber-optic acoustic sensor combined with ultrasonic GWs excitation.
The cost of conventional fiber optic interrogation system has been the limiting factor for its commercialization and market penetration into electrical asset monitoring where the room for capital investment on sensors is relatively small. The ability to deliver portable and cost-effective sensors without compromising their performances becomes critical. Here, we demonstrate the application and low-cost interrogation strategy for intensity-modulated evanescent wave fiber temperature sensor made of plasmonenabled thin films. Optical transmittance change resulting from the thermal damping of plasmonic absorption intensity is converted into analog voltage signals, then transmitted wirelessly through a set of commercial wireless hardware to enable remote monitoring capability. The temperature response is compared against a custom-designed intensity-based Fiber Bragg Grating (FBG) interrogator with Long Period Grating (LPG) edge filter, where its temperature and strain sensing performance of the intensity-based FBG interrogator is presented and discussed. Both sensors are deployed to monitor the dynamic thermal behavior of Li-ion polymer pouch cell under normal charging/discharging conditions. Finally, the initial design and implementation of an energy harvesting circuit that powers the low-cost wireless interrogator from a potential instrumented power conversion/storage device itself is also discussed.
Electrical system monitoring applications are of increasing importance given recent trends towards electrification driving adoption of renewables and electric vehicles, for example. Thermal and acoustic signatures play an important role in health monitoring while electrical and magnetic field signatures can provide information about operational state. Optical fiber sensors are of particular interest for electrical system applications because of the compatibility with deployment in electrified systems without concerns for electromagnetic interference (EMI) or additional potential risks due to the presence of electrical sensor wires or power at the sensing location, particularly for medium voltage electrical systems. In this presentation, an overview of recent work in optical fiber-based sensing for electrical asset monitoring applications will be discussed in detail. Plasmonic sensors integrated with engineered nanomaterials will be discussed for thermal and other health monitoring applications while interferometric sensors will be discussed for acoustics and also magnetic fields and electrical current sensing. New directions in fiber-based sensing applications will also be discussed moving into the future.
In this work, we demonstrate a reflection-based nanocomposite-functionalized fiber H2 sensor for ease of installation and H2 sensing in energy storage, fuel cells, electrolyzers, and other similar devices. High-temperature H2 fiber probes decorated with Au-Pt bimetallic alloy nanoparticles (NPs) in rutile titania matrix are characterized with scanning electron microscopy (SEM) and grazing incidence x-ray diffraction (GIXRD), and tested experimentally with varying H2 concentration and cycling gas conditions. In response to reducing H2, fully reversible reflectance intensity changes at the alloy NPs’ localized surface plasmon resonance (LSPR) absorption peak are demodulated in real-time. The reflection fiber probe coated with bimetallic Au-Pt NPs in titania show 15x higher sensitivity than corresponding monometallic Au NPs in titania. The demonstration of reflection hydrogen fiber probe provides an installation advantage in various reactor environment applications, and the investigation of the Au-Pt binary alloy system unfolds new sensitivity-enhancing pathways for NP-based LSPR modulation in reducing H2 environment at high temperatures.
Nanocomposite thin-film coated fiber optic sensors can be a promising solution to real-time temperature monitoring of electrical assets and imminent failure detection owing to minimal electrical connections and immunity to electromagnetic interference. However, cost of optical interrogation hardware has been a major roadblock for commercialization of fiber optic sensors. Here, we present a novel and simplified design of a fiber optic temperature sensor based on localized surface plasmon resonance (LSPR) response, a low-cost photodiode transimpedance-amplifier (TIA) circuit and collimated LED for monitoring applications where the cost of deployment is a critical consideration. The TIA circuit is designed to capture temperature-induced optical transmission and reflection responses by photocurrent-converted voltage variations communicated through Serial Peripheral Interface (SPI) wireless communication protocols. Wirelessly interrogable optical fiber sensors can therefore be potentially integrated in a wide range of assets such as grid-scale energy storage and medium or high voltage electric power conversion systems. To further minimize system complexity as compared to transmissionbased sensors demonstrated previously, a major emphasis is on a new reflection-based fiber sensor probe. This is also simulated in an optical waveguide physics-based model with Au-incorporated dielectric matrix oxides deposited on the fiber tip. Preliminary results of modeling the temperature response using end-coated reflection fiber probes are discussed.
pH is a critical parameter for wellbore integrity and geochemical monitoring in wells for oil and gas production, CO2 storage, H2 subsurface storage, and geothermal systems. In situ real-time pH monitoring in subsurface wells is of significant value for wellbore integrity monitoring and predictive analysis of well component deterioration such as casing steel corrosion and cement carbonation. However, harsh environments in subsurface wells have limited many commonly used pH sensors. We have previously demonstrated optical fiber pH sensors coated with metal oxide-based sensing materials such as TiO2, which offer stability at high pressures and temperatures. In this study, we demonstrated TiO2 coated optical fibers for real-time distributed pH monitoring based on backscattered light interrogation. TiO2 coated optical fibers were tested under ambient conditions and wellbore relevant conditions at elevated temperatures. TiO2 coating was deposited on the optical fibers through a facile sol-gel method. TiO2 coated optical fibers have shown promising pH sensing results under elevated temperatures and high pH conditions, making them suitable for wellbore cement monitoring.
KEYWORDS: Transformers, Temperature sensors, Optical fibers, Thermal modeling, Fiber optics sensors, Thermography, Temperature metrology, Magnetism, Finite element methods, Thin films
Reliable, secure, and resilient electricity distribution requires continuous health monitoring of electrical assets including power transformers. Among all sensing parameters, temperature is of utmost importance. Using optical fiber sensors for temperature monitoring has various advantages over traditional methods as they are inherently immune to electromagnetic interference, are good insulators at high-voltage levels, and are easy to install due to their small size and flexibility. Measuring the temperature of different parts of a power transformer core can help to detect hotspots and predict imminent device health issues. In this paper, a low-cost temperature sensor based on plasmonic-enabled optical fiber is demonstrated in multiple arrangements. The simplest arrangement would cost ~ $100 with potential for further cost reductions through reductions in the cost of the detection and excitation circuitry and optical components. By functionalizing an optical fiber with Au-Silica thin-films, the sensor was also demonstrated to measure the temperature of an energized transformer core in real-time. Repeatability and reliability of the proposed sensor were confirmed by running multiple cycles.
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