IN-LINE FIBER ETALON FOR STRAIN-MEASUREMENT

A description and demonstration of a fiber interferometer that uses a short segment of silica hollow-core fiber spliced between two sections of single-mode fiber to form a mechanically robust in-line cavity are presented. The hollow-core fiber is specifically manufactured to have an outer diameter that is equal to the outer diameter of the single-m ode lead fibers, thereby combining the best qualities of existing intr insic and extrinsic Fabry-Perot sensors. A dynamic strain resolution o f approximately 22 nepsilon/square-root Hz at frequencies of >5 Hz wit h a sensor gauge length of 137 mum is demonstrated.