Dr. Dolendra Karki Profile

Dr. Dolendra Karki

at Univ of Pittsburgh

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Author

Publications (12)

Proceedings Article | 7 June 2024 Presentation + Paper

Multimode interference-based fiber optic sensors using single mode/no-core/single mode (SNS) configuration

Tulika Khanikar, Dolendra Karki, Yang-Duan Su, Khurram Naeem, Paul Ohodnicki

Proceedings Volume 13044, 130440P (2024) https://doi.org/10.1117/12.3022011

KEYWORDS: Sensors, Fiber optics sensors, Single mode fibers, Multimode fibers, Fiber optics, Multimode interference devices, Refractive index, Spectral response, Signal intensity

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Proceedings Article | 7 June 2024 Presentation + Paper

Pipeline damage detection using multimode fiber-optic acoustic sensor and ultrasonic guided waves

Khurram Naeem, Pengdi Zhang, Enrico Sarcinelli, Dolendra Karki, Tulika Khanikar, Yang-Duan Su, Nageswara Lalam, Ruishu Wright, Paul Ohodnicki

Proceedings Volume 13044, 130440O (2024) https://doi.org/10.1117/12.3013838

KEYWORDS: Pipes, Acoustics, Sensors, Ultrasonics, Fiber optics sensors, Accelerometers, Vibration, Nondestructive evaluation, Multiplexing, Fiber optics

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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.

Proceedings Article | 7 June 2024 Presentation + Paper

Dopant segregation in single-crystal optical fiber grown via the laser-heated pedestal growth technique

Gary Lander, Jeffrey Wuenschell, Geunsik Lim, Dolendra Karki, Jun Young Hong, Paul Ohodnicki, Michael Buric

Proceedings Volume 13044, 130440H (2024) https://doi.org/10.1117/12.3013980

KEYWORDS: Dopants, Optical fibers, Structured optical fibers, Raman spectroscopy, Sapphire, Optical transmission, Neodymium

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Proceedings Article | 7 June 2024 Presentation + Paper

Dynamic response of magnetic fluid-cladded MMI fiber optic sensor optimized for fourth self-imaging spectral response

Dolendra Karki, Tulika Khanikar, Suraj Mullurkara, Khurram Naeem, Jun Young Hong, Paul Ohodnicki

Proceedings Volume 13044, 130440R (2024) https://doi.org/10.1117/12.3013823

KEYWORDS: Magnetometry, Nanoparticles, Multimode interference devices, Sensors, Frequency response, Magnetic sensors, Fiber optics sensors

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Proceedings Article | 4 October 2023 Presentation + Paper

Plasmonic and interferometric optical fiber sensors for electrical system monitoring applications

P. Ohodnicki, Y. Su, D. Karki, T. Khanikar, K. Naeem, N. Lalam, J. Wuenschell, M. Buric, R. Wright

Proceedings Volume 12647, 126470H (2023) https://doi.org/10.1117/12.2677290

KEYWORDS: Sensors, Fiber optics sensors, Transformers, Acoustics, Magnetism, Chemical analysis, Acetylene, Magnetic sensors, Plasmonics, Vibration

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Proceedings Article | 13 June 2023 Presentation + Paper

High-sensitivity distributed pipelines infrastructure monitoring with internal deployed fibers and Rayleigh enhancement

Khurram Naeem, Nageswara Lalam, Dolendra Karki, Tulika Khanikar, Ruishu Wright, Andy Gillooly, Kent Weisenberg, Ping Lu, Paul Westbrook, Paul Ohodnicki

Proceedings Volume 12532, 125320J (2023) https://doi.org/10.1117/12.2665058

KEYWORDS: Signal to noise ratio, Acoustics, Optical fibers, Metals, Single mode fibers, Optical sensing, Ferroelectric materials, Structural health monitoring, Fiber optics sensors, Data acquisition

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Proceedings Article | 13 June 2023 Presentation + Paper

Nuclear canister integrity monitoring using quasi-distributed fiber acoustic sensors and physics-based modeling

P. Ohodnicki, E. Sarcinelli, P. Zhang, K. Naeem, D. Karki, R. Meyer, N. Lalam, R. Wright

Proceedings Volume 12532, 125320I (2023) https://doi.org/10.1117/12.2665084

KEYWORDS: Acoustics, Fiber optics sensors, Corrosion, Vibration, Modeling, Sensors, Finite element methods, Structural health monitoring, Optical sensing, Waveguides

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Proceedings Article | 13 June 2023 Presentation + Paper

Optimization of the fourth self-imaging spectral response in magnetic fluid cladded-MMI fiber optic sensor for magnetometry

Dolendra Karki, Tulika Khanikar, Khurram Naeem, Nageswara Lalam, Paul Ohodnicki

Proceedings Volume 12532, 125320K (2023) https://doi.org/10.1117/12.2664107

KEYWORDS: Magnetic sensors, Refractive index, Absorption, Fiber optics sensors, Spectral response, Nanoparticles, Multimode interference devices, Refractometry, Magnetometry, Magnetooptics

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Proceedings Article | 27 May 2022 Presentation + Paper

Robotic fiber optic internal deployment tool for pipeline integrity monitoring

Nageswara Lalam, Ibrahiim Syed, Dolendra Karki, Kent Weisenberg, Ruishu Wright, Paul Ohodnicki

Proceedings Volume 12105, 1210504 (2022) https://doi.org/10.1117/12.2619045

KEYWORDS: Fiber optics, Robotics, Optical fiber cables, Optical fibers, Temperature metrology, Sensing systems, Fiber optics sensors, Rayleigh scattering

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Proceedings Article | 27 May 2022 Presentation + Paper

Machine vision approach of process control during single crystal fiber growth via laser heated pedestal growth method

Dolendra Karki, Edward Hoffman, Dong Shengye, Victoria Taylor Schmotzer, Bo Liu, Paul Ohodnicki

Proceedings Volume 12105, 1210508 (2022) https://doi.org/10.1117/12.2618538

KEYWORDS: Laser stabilization, Crystals, Process control, Machine vision, Feedback loops, LabVIEW, Fiber optics sensors

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Proceedings Article | 27 May 2022 Presentation + Paper

Fiber-optic sensor packaging assessment and benchmarking for embedded sensing applications

Dolendra Karki, Christopher Smith, Joseph Damian, Kayte Denslow, Glenn Grant, Jung-Kun Lee, Paul Ohodnicki

Proceedings Volume 12105, 1210505 (2022) https://doi.org/10.1117/12.2618492

KEYWORDS: Fiber optics sensors, Optical fibers, Fiber optics, Nondestructive evaluation, Structural health monitoring, Optical fiber cables, Fiber coatings

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Proceedings Article | 12 April 2021 Presentation + Paper

Fabrication and application of single crystal fiber via laser heated pedestal growth system

B. Liu, D. Karki, S. Bera, P. Ohodnicki

Proceedings Volume 11739, 1173903 (2021) https://doi.org/10.1117/12.2586173

KEYWORDS: Laser crystals, Fiber lasers, Crystals, Laser development, Biological and chemical sensing, Imaging spectroscopy, High power lasers, Environmental sensing, Control systems

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Showing 5 of 12 publications

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