Simultaneous measurement of two strain components in composite structures using embedded fiber sensor

This paper uses an in-line fiber etalon (ILFE) cascaded with an in-fiber Br agg grating to simultaneously measure axial and transverse strain component s inside a cantilever beam fabricated from a graphite/epoxy composite mater ial. The ILFE and Bragg grating sensor signals are demultiplexed using a va riation of coherence division multiplexing, and then demodulated using a Ps eudo-Heterodyne scheme. Composite cylinders models are developed that allow the optical measurements to be related to the strains in the host composit e material. Experimental results show that both of the measurement errors o f the two strain components are approximately 5 mu epsilon.