This Small Business Innovation Research Phase I project will attempt to develop a fiber optic sensor system for automated collection of data needed in monitoring infrastructure health. It incorporates two advances in wavelength sensing technology. Distributed arrays of In-Fiber Bragg Grating sensors have demonstrated high-sensitivity, long-term monitoring capabilities at affordable costs. By translating induced displacement into frequency shift, Bragg-sensors provide an optical alternative to electronic devices. They are used for precise measurements of displacements due to mechanical or other processes. The firm's proprietary technology for precision optical-wavelength (frequency) measurement is well suited for use in precision estimation of wavelength shifts of arrays of Bragg sensors. Integration of the firm's receiver with Bragg sensors provides simultaneous measurements on 10 sensors per fiber, with a dynamic range of 3 orders-of-magnitude. Accuracies equivalent to a few micro-strain at sampling rates of 10 KHz appear to be achievable. The proposed architecture provides a low-cost monitoring system using a programmable switching element. This allows one set of the more costly system elements to be used sequentially to sample large arrays of hundreds of sensors. Bcause wavelength is the basic measurement parameter, these sensors can be variably spaced and different measurement types can be intermixed along the same Fiber-Optic cable. Successful development of the proposed system will provide the basis for a high-performance, affordable, fiber-optic sensor system with broad commercial application in the areas of. environmental monitoring; nondestructive evaluation and monitoring of civil structures; and for use in "smart" composite structures.
