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Fiber Bragg grating (FBG) sensors have been widely applied for structural health monitoring applications. In some applications, remote bonding of the optical fiber is applied, where ultrasonic waves are coupled from the structure to the optical fiber and propagated along the fiber to the FBG sensor. The distance that this signal can propagate along the optical fiber without decaying below a threshold value can be critical to the area of the structure that can be monitored per sensor. In this paper, we develop a method to measure the acoustic mode attenuation of fiber waveguides based on laser Doppler vibrometry (LDV) that is independent of the fiber type. In order to validate the method, we compare attenuation measurements on single-mode optical fibers using both the LDV and FBG sensor methods. Once the method is validated, experimental measurements of different coated and uncoated optical fibers are performed to quantify the role of the fiber diameter on the attenuation coefficient. As the radius of the waveguide decreases, the signal attenuation increases exponentially.

Coherence of acoustic wave coupling through adhesive bond coupler is investigated using fiber ring resonator configuration. Coherent interference is observed between different kinds of fibers, opening up possibilities for sensing in field applications.

We demonstrate sensing based on an acoustic fiber ring resonator using optical fiber adhesive coupling for temperature sensing based on in acoustic path length and water level based on acoustic loss per unit length.

We examine the measurement of acoustic mode attenuation in optical fibers for sensing applications using both an internal fiber Bragg grating and laser Doppler vibrometry.

We amplify the signal coupled from ultrasonic Lamb waves into an optical fiber, for structural damage detection applications, using two devices: an ultrasonic horn and a phononic crystal GRIN lens.

This paper analyzes the conversion of acoustic modes in optical fibers from Lamb waves in structures. Experimental verifications of the physical behavior of these modes using micro-laser Doppler vibrometry is also presented.

We demonstrate a self-referencing FBG sensor for damage detection. The sensor compensates for changing environmental conditions by measuring the reference and distorted signal simultaneously and uses traveling acoustic waves in optical fibers.

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.