Preferential directional coupling to ultrasonic sensor using adhesive tape

Junghyun Wee; Drew Hackney; Kara Peters

doi:10.1117/1.OE.58.7.072003

16 January 2019 Preferential directional coupling to ultrasonic sensor using adhesive tape

Junghyun Wee, Drew Hackney, Kara Peters

Author Affiliations +

Optical Engineering, Vol. 58, Issue 7, 072003 (January 2019). https://doi.org/10.1117/1.OE.58.7.072003

Abstract

For structural health monitoring applications, recent studies have demonstrated an increased ultrasonic detection sensitivity of fiber Bragg grating (FBG) sensors through remote bonding of the FBG to a structure. In this case, the S₀ or A₀ Lamb waves in a structure are coupled to guided L₀₁ waves in an optical fiber at the adhesive bond location, resulting in L₀₁ modes of equal amplitudes propagating in both directions along the optical fiber. We demonstrate that when the adhesive bond is replaced with adhesive tape the S₀ mode couples to the same L₀₁ modes, however, with a preferential direction. Therefore, our study investigates the mechanism causing the preferential direction. We first identify different ultrasonic coupling pathways from a plate to an FBG through adhesive tape, demonstrating that both direct and indirect pathways are active, but that the indirect pathway produces the directional coupling. Then we test different adhesive tape parameters through experiments and simulations, demonstrating that flexural rigidity and bond length are parameters that can be used to control the directionality. The results of this work could be applied to design multiplexed FBG sensor arrays with specified signal pathways through the optical fiber networks.

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Junghyun Wee, Drew Hackney, and Kara Peters "Preferential directional coupling to ultrasonic sensor using adhesive tape," Optical Engineering 58(7), 072003 (16 January 2019). https://doi.org/10.1117/1.OE.58.7.072003

Received: 12 October 2018; Accepted: 6 December 2018; Published: 16 January 2019

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