Session: 04 - 01 Emerging Techniques & Technology

Paper Number: 108692

108692 - Modeling of Ultrasonic Coupling Between Optical Fibers Through an Adhesive Bond for Shm Applications 

FBG sensors have been widely applied to detect ultrasonic waves in structures for structural health monitoring applications. In addition, it can be advantageous to couple the ultrasonic waves into longitudinal modes in the optical fibers for detection with a remote FBG. This approach can increase the sensitivity of the FBG to ultrasonic signal. The authors recently demonstrated that longitudinal modes can also be transferred between optical fibers using an adhesively bonded coupler. This coupling preserves the waveform of the ultrasonic signal, however, the parameters governing the coupling coefficient are not known. This paper presents an experimentally validated finite element model of the coupling behavior. In addition this finite model is compared to two ordinary differential equation (ODE) representations of the system including a coupling coefficient and damping parameter. Parameter sweeps of the coupler geometry are performed to understand how they affect the coupling coefficient. It is shown that the spring interface condition ODE model better represents the coupling behavior, however the attenuation due to the adhesive cannot be captured. Additionally, coupling between multiple input and output fiber configurations are studied, similar to that of optical fiber couplers. The simulation results are compared to experimental measurements of couplers with the different input-output conditions. Finally, the usefulness of this coupling technique is described for Lamb wave imaging of structures.

Presenting Author: Kara Peters North Carolina State University

Presenting Author Biography: N/A