In-Fiber Acoustic Generation, Manipulation and Detection
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 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. The proposed program seeks to improve the performance of the fiber optic acoustic sensing technologies and investigate the potential for acoustic fiber Bragg gratings (AFBGs) to further expand the functionality and capabilities of optical fiber-based sensing systems. The development and demonstration of in-fiber acoustics for use with optical fiber acoustic sensors will yield a compact, high performance technology that will enable the realtime structural health monitoring of critical engine components and naval assets.The objective of the proposed three-year effort is to develop acoustic generator arrays in a single optical fiber that can be actively tuned for (pseudo) distributed measurements from metallic surfaces. The fundamental mechanisms that govern optically driven acoustic excitation and manipulation in an optical fiber will be investigated to enable active acoustic tuning (directionality, frequency, intensity, etc..) and expanded functionality with acoustic fiber Bragg grating (AFBG) technologies. In the first project year, the generation of acoustic waves from an external metal source will be studied to gain a full understanding of the mechanisms that govern photo- acoustic wave excitation. The potential for the selective and controlled excitation of one or more in-fiber acoustic generators will be evaluated in the second project year. AFBGs with apodized profiles will be investigated for integration at higher frequencies (> 1 MHz) to yield measurements with high spatial resolution and enable multiplexing in a single fiber length. Directional and characteristic control of acoustic generators will be evaluated with a special multi-material optical fiber with metal included in the cladding and combined with AFBG technologies. In the final year of the project, an active all-optical fiber based acoustic sensing system and all-acoustic fiber sensing system will be demonstrated for the structural health monitoring of metal structures. The successful execution of the proposed program will set the stage for the development of all-fiber acoustic generation/detection technology with unparalleled capabilities and the small footprint necessary to facilitate near-term adoption for the structural health monitoring of U.S. naval assets.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 06, 2021
- Source ID
- N000142112125
Entities
People
- Gary Pickrell
Organizations
- Office of Naval Research
- United States Navy
- Virginia Tech