Abstract

Fiber-optic based communication depends on the availability of high quality low loss optical fibers. Light guidance within a fiber is discussed.

Operating wavelengths have been extended by controlling fiber attenuation and dispersion. Fiber fabrication methods are presented. The use of high purity starting materials and vapor deposition techniques allows the production of glass fibers having optical losses that approach the intrinsic loss of silica. Fiber drawing processes determine strength. Active optical fibers have been exploited to amplify light, extending the range of transmission systems and allowing increased capacity. Erbium-doped fibers are being used for signal amplification in fiber-optic cable. Devices taking advantage of gratings written in optical fibers include filters and lasers.

Most fiber-optic smart structure applications fall into one of four major categories. The first is smart manufacturing where fiber-optic sensors are embedded or attached to parts during the manufacturing process. They are then used to monitor such parameters as temperature, pressure, viscosity, degree of cure, and residual strain. After the parts have been made, the same sensors or another set may be used for the second application area of nondestructive testing. Here, the fiber sensors may be used to measure acoustic signatures, changes in strain profiles, delamination, and other indications of changes in the structural characteristics of fabricated parts. The third aspect of fiber-optic smart structures that has been the focus of many efforts is health and damage assessment systems for structures. In the parts of the structure that have been assembled, fiber-optic sensor technology is used to monitor the overall health of the structure. Finally, fiber-optic smart structures may be used to support control systems.

Fiber-optic sensors that are particularly useful for smart structures are briefly overviewed, followed by examples of applications.