@article{soman_kim_boyer_peters_2024, title={Optimal Design of a Sensor Network for Guided Wave-Based Structural Health Monitoring Using Acoustically Coupled Optical Fibers}, volume={24}, ISSN={["1424-8220"]}, url={https://www.mdpi.com/1424-8220/24/19/6354}, DOI={10.3390/s24196354}, abstractNote={Guided waves (GW) allow fast inspection of a large area and hence have received great interest from the structural health monitoring (SHM) community. Fiber Bragg grating (FBG) sensors offer several advantages but their use has been limited for the GW sensing due to its limited sensitivity. FBG sensors in the edge-filtering configuration have overcome this issue with sensitivity and there is a renewed interest in their use. Unfortunately, the FBG sensors and the equipment needed for interrogation is quite expensive, and hence their number is restricted. In the previous work by the authors, the number and location of the actuators was optimized for developing a SHM system with a single sensor and multiple actuators. But through the use of the phenomenon of acoustic coupling, multiple locations on the structure may be interrogated with a single FBG sensor. As a result, a sensor network with multiple sensing locations and a few actuators is feasible and cost effective. This paper develops a two-step methodology for the optimization of an actuator–sensor network harnessing the acoustic coupling ability of FBG sensors. In the first stage, the actuator–sensor network is optimized based on the application demands (coverage with at least three actuator–sensor pairs) and the cost of the instrumentation. In the second stage, an acoustic coupler network is designed to ensure high-fidelity measurements with minimal interference from other bond locations (overlap of measurements) as well as interference from features in the acoustically coupled circuit (fiber end, coupler, etc.). The non-sorting genetic algorithm (NSGA-II) is implemented for finding the optimal solution for both problems. The analytical implementation of the cost function is validated experimentally. The results show that the optimization does indeed have the potential to improve the quality of SHM while reducing the instrumentation costs significantly.}, number={19}, journal={SENSORS}, author={Soman, Rohan and Kim, Jee Myung and Boyer, Alex and Peters, Kara}, year={2024}, month={Oct} }
 @article{kim_peters_2023, title={Modeling of Ultrasonic Coupling between Optical Fibers through an Adhesive Bond for Sensing Applications}, volume={12488}, ISBN={["978-1-5106-6083-0"]}, ISSN={["1996-756X"]}, DOI={10.1117/12.2666031}, abstractNote={This paper presents finite element modeling of an adhesively bonded coupler for the transfer of acoustic modes between two optical fibers. Acoustic modes are propagated through optical fibers for Lamb wave detection with remotely bonded Bragg grating sensors. The model output is compared to previous experimental data, varying the relative diameter of the two fibers. Parameter sweeps of the coupler geometry are also performed to understand how they affect the coupling coefficient.}, journal={HEALTH MONITORING OF STRUCTURAL AND BIOLOGICAL SYSTEMS XVII}, author={Kim, Jee Myung and Peters, Kara}, year={2023} }
 @article{kim_wee_peters_2022, title={Demonstration of Coherent Interference between Acoustic Waves Using a Fiber Ring Resonator}, volume={22}, ISSN={["1424-8220"]}, url={https://www.mdpi.com/1424-8220/22/11/4163}, DOI={10.3390/s22114163}, abstractNote={Optical fibers were previously demonstrated to propagate and detect acoustic modes that were converted from Lamb waves for structural health-monitoring applications; typically, a fiber Bragg grating sensor in the optical fiber is used to detect acoustic modes. Acoustic modes can transfer from one fiber to another through a simple adhesive bond coupler, preserving the waveform of the acoustic mode. This paper experimentally investigates the coherence of acoustic waves through the adhesive coupler, using a fiber ring resonator (FRR) configuration. This configuration was chosen because the wave coupled to the second fiber interferes with the original wave after it encircles the fiber ring. We performed this experiment using different geometries of optical fibers in the ring, including a standard single-mode optical fiber, a hollow silica capillary tube, and a large-diameter multi-mode fiber. The results demonstrate that the acoustic wave, when transferring through an adhesive coupler, interferes coherently even when the main and ring fibers are of different types. Finally, we demonstrate that the FRR can be applied for sensing applications by measuring the mode attenuations in the ring due to a changing external environment (water-level sensing) and measuring the optical-path length change in the ring (temperature sensing).}, number={11}, journal={SENSORS}, author={Kim, Jee Myung and Wee, Junghyun and Peters, Kara}, year={2022}, month={Jun} }
 @article{soman_kim_aiton_peters_2022, title={Guided waves based damage localization using acoustically coupled optical fibers and a single fiber Bragg grating sensor}, volume={203}, ISSN={["1873-412X"]}, DOI={10.1016/j.measurement.2022.111985}, abstractNote={Fiber Bragg grating (FBG) sensors have long been thought of as the ideal sensors for structural health monitoring (SHM) due to their small size, light weight, ability to be embedded and ability to be multiplexed. So, FBG sensors have been commonly used for strain based SHM. In recent times, a renewed interest is seen in the use of FBG sensors for GW measurements using the edge filtering approach which increases the sensitivity several fold. The remote bonding configuration has also been proposed to enhance this sensitivity further. But in order to achieve damage localization, a multi-sensor network is needed. The FBG sensors and the equipment for employing them in the edge filtering configuration is expensive. As a result, their use for SHM in large structures is still limited. Recent studies have shown that the acoustic wave in an optical fiber may be transferred from one optical fiber to another through an adhesive based acoustic coupler. In this study, this phenomenon is used to develop an SHM system which is capable of damage localization using a single FBG sensor. The paper presents a proof-of-concept of the use of the acoustically coupled optical fibers and single FBG for damage localization. The paper also highlights the design considerations of an acoustic coupler and discusses them in detail. The proposed approach has a potential to radically reduce the equipment costs (factor of 3) which is one of the limiting factors in the widespread acceptance of SHM systems in structures.}, journal={MEASUREMENT}, author={Soman, Rohan and Kim, Jee Myung and Aiton, Sean and Peters, Kara}, year={2022}, month={Nov} }
 @article{soman_boyer_kim_peters_2022, title={Particle Swarm Optimization Algorithm for Guided Waves Based Damage Localization Using Fiber Bragg Grating Sensors in Remote Configuration}, volume={22}, ISSN={["1424-8220"]}, url={https://www.mdpi.com/1424-8220/22/16/6000}, DOI={10.3390/s22166000}, abstractNote={Structural health monitoring (SHM) systems may allow a reduction in maintenance costs and extend the lifetime of the structure. As a result, they are of interest to the research community. Ideally, the SHM methods should be low cost, while being able to detect and localize small levels of damage reliably and accurately. The fiber Bragg grating (FBG) sensors are light in weight, insensitive to electric and magnetic fields, and can be embedded. The edge filtering configuration for transduction allows the use of FBG for guided wave (GW) sensing. This sensitivity may be further enhanced through their application in the remote bonded configuration. This paper provides a proof-of-concept for the use of remotely bonded FBG for damage localization. In order to improve the computational efficiency, a particle swarm optimization (PSO) based algorithm is developed. The PSO allows a significant improvement in the computation time which makes it better suited for real-time damage localization. The proposed objective function is based on the exponential elliptical approach. First, the suitability of the PSO for damage localization is shown. Then the performance of the chosen objective function is compared with the brute-force algorithm as well as other objective functions found in the literature. The methodology is employed on a simple aluminum plate. The results indicate that indeed the objective function along with the PSO is suitable for damage localization. Also as the objective function is developed taking into consideration the specific challenges with the use of FBG sensors, performs better than the other objective functions as well as the brute force algorithm.}, number={16}, journal={SENSORS}, author={Soman, Rohan and Boyer, Alex and Kim, Jee Myung and Peters, Kara}, year={2022}, month={Aug} }
 @article{kim_marashi_wee_peters_2021, title={Acoustic wave coupling between optical fibers of different geometries}, volume={60}, ISSN={["2155-3165"]}, DOI={10.1364/AO.441494}, abstractNote={In this study, we investigate coupling of acoustic guided waves from
					different types of input fibers, through a bonded coupler, to an
					optical fiber. These acoustic waves can then be detected with
					conventional fiber Bragg gratings (FBGs). The input waves are measured
					using a high-resolution 3D laser Doppler vibrometer, and the output
					waves in the optical fiber are measured using an FBG. We demonstrate
					that the wave coupling between two waveguides varies with the
					cross-sectional area and the modulus of elasticity of the fibers.}, number={36}, journal={APPLIED OPTICS}, author={Kim, Jee Myung and Marashi, Cameron and Wee, Junghyun and Peters, Kara}, year={2021}, month={Dec}, pages={11042–11049} }
 @article{kim_marashi_wee_peters_2021, title={Investigation on acoustic wave transfer variation between fibers of different diameters and types using acoustic coupler}, volume={11591}, ISSN={["1996-756X"]}, DOI={10.1117/12.2584249}, abstractNote={When using fiber Bragg grating (FBG) sensors in structural health monitoring (SHM) applications, one of the drawbacks is that the sensor location is fixed once it is installed and it is difficult to extend an already existing system. The use of an acoustic coupler to transfer fiber guided traveling waves from one fiber to another could resolve this issue as the system could be modified for extension. In this study, we investigate the coupling of optical fiber guided waves between two different types of fibers through an acoustic coupler. Specifically, input waves are launched into an input fiber and coupled to an output fiber through the acoustic coupler. The input waves are measured using a high-resolution 3D laser Doppler Vibrometer (LDV) and the output waves from the output fiber are measured using an FBG. We demonstrate that the wave coupling between two fibers varies with the cross-sectional area of the input fiber.}, journal={SENSORS AND SMART STRUCTURES TECHNOLOGIES FOR CIVIL, MECHANICAL, AND AEROSPACE SYSTEMS 2021}, author={Kim, Jee Myung and Marashi, Cameron and Wee, Junghyun and Peters, Kara}, year={2021} }