Intrinsic microbend fiber optic sensors

Abstract

In this paper, special optical fibers are embedded into 3-D braided carbon/epoxy composites to constitute intrinsic microbend fiber optic sensors for internal strain measurement. Samples with embedded optical fibers are braided through four-step method and processed through Resin Transfer Molding (RTM) process. Special measures are taken to prevent damage of the sensors. The microbend optic fiber sensor works well in a three-point bending experiment. The experiments show that the output intensity of the microbend sensor is proportional to the internal strain of the sample while the load increases. Similar results can be achieved as the load decreases.The results show that the embedded microbend fiber optic sensor is fit for internal strain measurement in 3-D braided composites.

Optical transmission modulation by fiber guide bending

“…The invariant of guided rays in the FLG falls between the values n1 < l < n0, where n0 is the maximum value of n(r). The formula calculates the value of the ray path invariant for a graded FLG: (7) Figure 2 (a) shows the dependence graphs of l(r) for four different bending radii of the FLG. It can be seen from the graphs that as the radius of curvature of FLG decrease the caustic of the turnoff points narrows and shifts to the external boundary of the FLG core.…”

“…The broad options to create quasi-distributed FOMLs based on them are offered by their properties, such as the nonseparable sensor design and the simple control of its configuration. The research of the functional principles and amplitude microbend sensor designs can also be learnt from the studies [4][5][6][7][8][9].…”

“…The observed design involves squeezing a multi-mode (MM) optical fiber with two parallel strips in an elastic substrate. The approaches based on microbend of fiber light guides in 3Dcarbon or epoxy-filled composites for measuring internal deformations have also been successfully used [7].…”