Design Parameters of a Serpentine Optical Fiber Bending Transducer for Strain Measurements in Smart Structures

A unique optical fiber transducer for measurement of bending strains that can be used for display of distributed strains in a structure is described. A mathematical model for the design of this transducer with circular segments is presented. The attenuation along one 360° segment with respect to bending radius and a biaxial stress field is derived. Analytical results show that the serpentine transducer is most sensitive to curvature of the plane that includes the circular segment. The effects of the bending curvature on a circular segment, when the center of curvature is in the same plane as that of the circular segment, is for the attenuation to average out to produce relatively small net change as a function of curvature.

Experimental results are presented to show the output of net attenuation through the serpentine transducer. Three-point bending tests demonstrate the problem of selection of the initial circular segment radius to avoid the whispering gallery mode of attenuation fluctuation.