Efficient Acoustic-Optical Fiber Coupling for Enhanced Sensor Response
Abstract
Technologies that enable the autonomous monitoring of the structural and integrity of Navy assets are needed to improve the decision making necessary for the preventative maintenance of components that are prone to fatigue and failure. The of low price, integrated functionality and reliability of acoustic devices have prompted the development of an array of acoustics-based sensing technologies. Recently, FBGs have been deployed as transducers to collect and identify the distortion or conversion of the ultrasonic waves excited in structure to identify defects and the generation and propagation of cracks. Efficient coupling of these ultrasonic waves from the structure to the FBGs is required to achieve the high signal-to-noise ration necessary to extract the relevant information from sensors. Furthermore, longitudinal mode conversion upon couplingassures conservation and propagation of the acoustic waves in the optical fiber sensor. The demonstration of acoustic-optical fiber horns with high coupling efficiencies that can be readily integrated with the FBG based acoustic sensors will help usher in the next generation of real-time nondestructive evaluation technologies for naval systems.The objective of the proposed three-year effort is to develop compact and efficient acoustic-optical fiber horns and couplers and demonstrate improvements to the ultrasonic detection sensitivity of fiber Bragg grating (FBG) sensors. Exhaustive theoretical modeling and analyses will be performed to design acoustic-optical fiber horns and couplers for mode conversion andpropagation in fused silica optical fibers. Materials optimization will be performed selected acoustic-optical fiber horn/couplers will be fabricated and integrated with the sensing fiber. Materials and techniques will be evaluated to bond the horn/amplifier to the surface of test piece and embedded in a test piece. A preliminary investigation of lamb wave coupling efficiencies toa rectangular fused silica optical fiber and single crystal sapphire fiber based ultrasonic coupling to silica based optical fiber and will be performed The performance and coupling efficiencies of the horns/couplers will be characterized with our unique in-house characterization equipment thatenables attenuation and power confinement via time domain reflectometry (TDR). An acoustic sensing system will be developed based on fused silica based intrinsic Fabry Perot interferometers (IFPIs) and/or fiber Bragg gratings (FBGs) to demonstrate ultrasonic sensors with high detection sensitivity. Prototype ultrasonic sensing systems will be constructed and evaluated in a simulated laboratory environment.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 08, 2020
- Source ID
- N000142012485
Entities
People
- Gary Pickrell
Organizations
- Office of Naval Research
- United States Navy
- Virginia Tech